A Review of Optometric Assessment Techniques for Use With Mentally Retarded and Other Special-Needs Patients

This course presents methods for examining patients with mental retardation, developmental delay, and/or other special needs. It is designed to familiarize the clinician with characteristics of this population and to describe specific vision tests most likely to yield useful information.

It is important to recognize that examinations with special needs patients often differ significantly from standard examinations. However, any complete vision examination should assess at least the patient's acuity, refractive error, accommodation, binocularity, fields, eye movement abilities, and ocular health.

Typical (and less common) tests that can be used to assess each aspect of visual function will be discussed followed by a review of how to perform the tests. Suggestions will also be presented to provide insights regarding the examination of special-needs patients.

According to the American Association on Mental Retardation, “Mental retardation is a disability characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social, and practical adaptive skills.” (3)

In the United States, an estimated 6.2 to 7.5 million people are retarded. (1) Retardation is 10 times more common than cerebral palsy and affects 25 times as many people as does blindness. One out of ten American families is directly impacted by mental retardation. (2)

Although retardation can occur in isolation, in 85% of patients it exists in conjunction with other handicapping disorders such as Down’s Syndrome, cerebral palsy, Turner’s Syndrome, and Fragile X Syndrome. (2)

There are four basic classifications of mental retardation, which are based largely on measured intelligence quotient (IQ). The mild group includes 90% of those with retardation. IQs of patients in this group range from 50 to 69. The moderate group includes 5% of retarded persons; IQs range from 35 to 55. The severe group includes 2.5% of retardates; IQs range from 20 to 40. The fourth group is the profound population, which also includes 2.5% of the retarded population. The IQs of profoundly retarded individuals are below 20 to 25. (2)

It is important to note that a patient's developmental age (DA) cannot be determined strictly by measuring IQ alone and may differ significantly from it. Developmental age is based on assessments of how well an individual functions in social settings. Family members, case managers, and support staff are invaluable in helping to describe a patient's abilities and limitations when determining DA.

As a group, patients with retardation and developmental disabilities are at increased risk for ocular abnormalities including significant refractive errors, strabismus, ocular disease, and information processing problems. Margaret Ronis has shown that 100% of the developmentally disabled individuals she studied had accommodation dysfunction, 92% had oculomotor dysfunction, and 78% had visual-perceptual dysfunction. (4)

Each special-needs patient has unique issues and adaptations. Understanding these personality-related dynamics can be vital to completing a comprehensive vision exam. For example, some profoundly mentally retarded patients exhibit severe stranger wariness and need to be approached with an appropriate level of sensitivity.

It is best to allow retarded patients to participate in as many decisions regarding their care as possible. This helps them feel a sense of some control over the situation. Even small amounts of empowerment hold special meaning for someone who senses that most things are out of his/her control.

Allow extra time for patient response to procedures and questions. Delayed processing and a "slow mental clock" often accompany retardation and developmental delays.

Planning and preparation for the examination begins well before the patient arrives. A questionnaire can be sent out in advance of the appointment to gather information that will help in understanding the unique needs of the patient and his/her level(s) of function. (5) The questionnaire will allow the clinician to ascertain where the patient falls within the developmental spectrum by asking questions about visual and developmental milestones.

It is also useful to determine who will be accompanying the patient to the examination and how well they know the patient. If the patient is in a care facility, the facility may send the an employee unfamiliar with the patient and the patient's needs.

Listed below are examples of questions that would help in preparation for the patient's examination.

When the patient first enters the office, it is important to observe how the patient and any accompanying caregiver interact and to develop a feel for the patient's body language. Careful observation will provide an indication of the best way to approach the patient and his/her communication style. For example, does the patient like to be touched on the arm or hand, or does he or she shy away from touches?

During the medical history portion of the examination, an understanding of medications generally prescribed for the special-needs population and their side-effects is important. It is common for patients to have been prescribed multiple pharmaceuticals, some or all of which can produce visual side-effects.

For example, anti-seizure medications have been reported to cause concentric contraction of the visual field and blurred vision, (6) and anticonvulsant medications can reduce extraocular muscle performance. Several central nervous system agents used to treat obsessive-compulsive disorders, anxiety, and hyperactivity (e.g., paroxetine (Paxil®), alprazolam (Xanax®), and pemoline (Cylert®)) list blurred vision as possible side-effects. Anticholinergic drugs prescribed to manage symptoms of cerebral palsy can also cause dry, irritated eyes, varying degrees of cycloplegia, and blurred vision. (7)

If possible, request records from previous vision examinations prior to the patient's visit or have records brought with the patient. Patients with special needs often have an extensive history of ocular and systemic health issues.

The patient’s method of communication is arguably the most important piece of information to learn prior to actually starting the examination.

The school record of a visually impaired child enrolled in special education classes will typically contain information from previous functional vision assessments and eye exams. These records can be requested from the school and are an excellent resource to review before the examination.

Establishing a level of trust with the patient is essential to obtaining a maximum level of participation. Demonstrate genuine care for the patient. Establishing trust and rapport is even more important with a special-needs patient than it is with a normal patient.

Request that a caregiver who knows the patient, special education teacher, or a staff-worker accompany the special-needs patient on at least the first visit. This will aid in obtaining information regarding the patient’s disabilities and strengths. It also facilitates an interdisciplinary team approach by allowing more members of the team to have input. In addition, it fosters better communication and helps to promote common management goals.

The quality of life for many developmentally disabled individuals depends on the degree of functional vision they possess. (4)

There are several different types of tests used to determine visual acuity. Selection of a test is largely dependent on the patient's ability to respond and his/her developmental age. Time is of the essence when conducting the examination, so it is best if the practitioner has three or four different acuity tests on hand in order to choose the right test for the situation. Discrimination acuity tests are more specific than other tests, but require letter and/or symbol recognition. Less specific tests include preferential looking procedures that rely on the tendency of a patient to look at a patterned or otherwise interesting stimulus versus a plain one. There are also physiologically-oriented tests such as optokinetic nystagmus and visually evoked potential measurements.

Letter recognition tests are generally more successful when the patient has a developmental age of at least five or six years. The best tests for determining visual acuity via letter recognition are the Snellen and Bailey-Lovie acuity tests. Snellen acuity tests have been traditionally considered the gold standard, but the Bailey-Lovie Test is better from a psychometric perspective because of its equally progressive LogMar (logarithmic minimum angle of resolution) format.

LogMar charts allow standardized analysis of visual acuity scores and comparisons of results more precisely. It offers this because the equal linear steps of the LogMar scale represent equal ratios in the standard size sequence; the letters change in size logarithmically by 0.1 log units (or 1.2589 times) per line as the acuity demand increases/decreases. There are always five letters per line, therefore, each letter is assigned a score of 0.02.

For example, an individual who could read the entire 0.4 line would score 0.4. If that individual could then read 2 letters from the 0.3 line, his/her score would be 0.36 because 0.02 would be subtracted per correct letter from the last full line read [0.4 – (2*0.02) = 0.36]. A LogMar score of 0.0 would be equal to a 20/20 (6/6) Snellen acuity; the log of 0.0 is 1, which represents a minimum angle of resolution equal to a Snellen 20/20 (6/6).

Fig. 1. Bailey-Lovey Acuity Test Chart (Figure from Rosenbloom, Alfred & Morgan, Meredith. Principles and Practice of Pediatric Optometry. JB Lippincott Co., Philadelphia, 1990; page 170.)

The traditional advantage of letter tests is that most practitioners have a high level of comfort and experience working with them. Another advantage is that they are universally available and well standardized.

The HOTV test is appropriate for patients with developmental ages between three and seven years. The test receives its name because only the letters H, O, T. and V are used in the chart. The test is administered in the same fashion as other acuity tests, such as Snellen. If a patient is non-verbal or does not know the alphabet, he/she can still perform this acuity test by pointing to corresponding letters on a near card.

It is important to note that the HOTV symbols blur to dissimilar shapes (much like Snellen letters), hence it may be possible for the patient to identify the correct letter even though it may be seen as very blurry. Given this limitation, HOTV results correlate well with Snellen acuities. A benefit of HOTV results is that they are not affected by letter reversals and it is useful even with those patients who may only know a few letters of the alphabet.

The Lea Symbol Acuity test is usually successful for patients with developmental ages between two and one half and five years. The patient views a distant chart and matches symbols of different sizes that are presented on it to similar symbols presented on a large near chart.

A major benefit of this test is that it is works well with non-verbal patients because they can point to the matching symbol on the example card. It has also been recommended by the American Academy of Ophthalmology.

Another significant advantage is that all the Lea symbols blur to circles, thus the patient will be less likely to experience a sense of failure when all of the symbols below acuity threshold appear the same. This means that during testing the patient believes that he/she is always answering correctly.

The Lea Symbols test can be performed at distance or at near and its results correlate well with HOTV acuities. (8)

The Lighthouse Flashcard Acuity test is appropriate for patients with developmental ages between two and three years. This is a forced choice test in which the patient must correctly identify apple, house, or umbrella figures. To administer the test, show the lower demand cards at a closer distance and have the patient name the symbols on the cards. Once the examiner is satisfied that the patient has grasped the concept, the examiner begins the test at a distance of ten feet. Show the cards in a random order at higher acuity demands. It is recommended that four presentations be given at each acuity level. An acuity value is assigned as the last Snellen equivalent for which the patient correctly identified four out of four presentations.

Lighthouse results are comparable to those from the HOTV because both are symbol recognition tests that blur to dissimilar shapes. Therefore, a correct response on either test may be the result of blur interpretation and the test may over-estimate the patient's acuity.

The broken wheel test uses Landolt C symbols in conjunction with the picture of a car, making it useful with developmental ages down to three years of age. The broken wheel test is performed by displaying pictures of two cars side-by-side, one with the letter “O” for wheels and the other with Landolt C’s. The patient is asked to point to the car with broken wheels.

Fig. 5. Broken Wheel Test (Figure from Hilco/Wilson Smart Ophthalmological Products. (2004). Retrieved from http://www.hilco.com/catalog/catalog_browse.asp?ResultType=single&prodID=4557&IDType=internal&refpg=exam_vistest_main.asp on January 16, 2005.

The broken wheel acuity test is very sensitive to blur. Slight blur causes the images of the broken and non-broken wheels to appear the same, whereas with the same level of blur some Snellen letters can still be discriminated due to letter morphology.

The broken wheel test uses a forced choice paradigm so it can be repeated without changing the demand or risking memorization. There is only a 25% probability that a patient is guessing if he or she correctly identifies three out of four presentations. Broken wheel test results correlate well with Snellen acuities.

Teller acuity cards measure grating acuity using a preferential looking paradigm. The test is especially useful for patients with cortical impairment because it does not require a high level of form perception ability. The test is appropriate for developmental ages of two years and below.

Each Teller card has stripes on one side, an isoluminant gray field on the other, and a small observation hole in the center. To administer the test, the clinician holds the card up to his/her face and views the patient's response to presentation of the card through the observation hole. The natural human tendency is to orient the eyes/head to the high contrast stripes rather than the gray isoluminant portion of the card. The examiner observes the gaze of the patient to determine if the patient detects and orients to the stimulus stripes.

To avoid bias, the examiner should be ignorant regarding which side of the card contains the stimulus stripes. Optimally, the patient should have unrestricted horizontal motilities in order to respond in a manner detectable to the cardholder. Head turns and pointing at the side of the card with the stripes are also acceptable responses.

Different cards have different grating spatial frequencies corresponding to Snellen acuities. Each Teller card is presented four times. The patient moves on to the next higher frequency grating acuity card until the orientation response is extinguished, and the patient can no longer correctly respond to three out of four presentations. This end-point determines the patient's acuity.

Cardiff cards are preferential looking cards that employ form discrimination with vanishing optotypes. Cardiff cards differ from Teller cards in that Cardiff cards are held with a vertical orientation and there is no observation hole. With Cardiff cards, the clinician observes whether the patient's eyes move up or down to either the picture stimulus or the blank area of the card. The test is continued with smaller and smaller pictures until the patient can no longer identify the location of the stimulus on two out of three presentations.

Cardiff cards are printed with eleven different acuity stimuli. This test is useful for patients who function between a one and three year developmental age.

As with the Teller cards, an advantage of Cardiff card testing is that no language is required. A disadvantage is that assumes unrestricted ocular motilities in the vertical meridian. Vertical eye movements can also be somewhat harder to detect than the horizontal movements made during Teller card testing.

Other useful tests for determining acuity include the Bailey-Hall Cereal Test, which is good for developmental ages between eighteen months and three years of age. The Bailey-Hall Cereal Test is a forced choice picture test that has two cards at each acuity level, one with a picture of a piece of cereal, the other with a textured square. Operant conditioning can be employed by giving the patient a piece of cereal for each correct response.

The Candy Bead Visual Acuity Test (CBVAT) can also be used for patients with developmental ages between ten to twelve months. Candy beads, such as cake decorations, are used to grossly estimate nearpoint visual acuity. The test is administered either by holding the small candy beads in one palm, while leaving the other empty or by placing the candy beads on a sheet of white paper. The patient is than instructed to pick up a single piece of candy. Again, operant conditioning can be employed by offering the child candy for each correct response.

Fig. 8. Bailey-Hall Cereal Test (left) and Candy Bead Visual Acuity Test sample pieces. (Figure from Press, Leonard and Moore, Bruce. Clinical Pediatric Optometry. Butterworth-Heinemann, Boston 1993; pg 48 and 51)

OKN is an objective test that requires little or no conscious effort by the patient. A drum with stripes or patterns is rotated and the examiner observes the patient's eyes as they follow the rotating stimulus and then jump back to pick up a new pattern as the one being followed moves out of sight. The angular subtense of the stripes or pattern is decreased until the nystagmus is extinguished, which determines the patient's acuity. This test is appropriate for developmental ages between eighteen months and seven years.

The VER is an objective electrodiagnostic test that can estimate a patient's acuity. A scalp electrode is used to record electrical signals from the visual cortex while the patient views a phase-reversing grating or checkerboard stimulus. The angular subtense of the stimulus detail is decreased until the VER becomes unmeasurable, which corresponds to the minimal detail the patient can resolve. Computers and other equipment required for VER recording are not commonly found in general optometric practices, but may be available in tertiary health care facilities.

If responses are inconsistent when measuring visual acuity, switch to a different test, preferably one that can be repeated without risk of patient memorization.

For patients who are non-verbal, utilize another mode of communication such as pointing to indicate a choice.

Special-needs patients have a higher than normal rate of binocular abnormalities that can interfere with development and perception. Many of theses disorders can be treated if they are detected early enough. (2)

This test is performed in a dim room. An ophthalmoscope light is directed at both of the patient's eyes simultaneously from a distance of about one meter, and the red reflexes are compared. If one eye has a brighter reflex, it is more likely to be strabismic, have greater uncorrected hyperopia/astigmatism, or have an ocular health abnormality.

Fig. 10. Brückner Test Results From a Strabismic Patient. (Figure from Rosenbloom, Alfred & Morgan, Meredith. Principles and Practice of Pediatric Optometry. JB Lippincott Co., Philadelphia, 1990; page 174.)

The Brückner test is helpful for low functioning patients and patients with limited visual ability such as those with cortical impairment because it only assesses the optical properties of the eyes and does not rely on information processing or perception. (With cortical impairment, the structures of the visual system are present, but information is not properly processed.)

The Brückner test requires minimal cooperation and participation from the patient because the patient’s attention is naturally drawn to the fixation light.

The Hirshberg test is used to grossly quantify any strabismus detected with the Brückner test. To perform the Hirshberg test, a small light source placed on the midline at eye level is viewed by the patient from a distance of about 40 cm. The Hirschberg can also be performed using the ophthalmoscope; this is especially helpful when the patient has dark irides. While the patient is looking at the light, the clinician notes the location of the Pürkinje corneal light reflexes in relation to the centers of the pupils. If the relative positions of the light reflexes are symmetric and centered , it is assumed that no strabismus is present. (Actually, the reflexes are decentered about 0.4 mm nasally, but this small decentration is very difficult to detect.)

Fig. 11. Hirschberg Tests Results From a Strabismic Patient. (Figure from Indiana University School of Optometry CE: Routine Optometric Examination of the Infant. (2003). Retrieved from http://www.opt.indiana.edu/ce/infant/exambr/hirsch.htm on January 23, 2005.)

If the light reflexes are significantly asymmetric, the angle of strabismus can be estimated by the amount of asymmetry, with 1 mm equal to approximately 22 prism diopters. (9)

This test can be used with patients who have cortical impairment because negligible cooperation is required. A disadvantage is that the strabismus angle estimate is not very precise.

This test provides a gross evaluation of monocular fixation when asymmetry is detected with the Hirschberg test.

The clinician's left eye is aligned with the patient’s midline and positioned 40 cm away. The patient’s left eye is occluded and the clinician’s right eye is closed.

A small light source is placed under the clinician's right eye and directed toward the patient's midline. The patient is then instructed to look at the light. The clinician views the corneal light reflex in relation to the center of the pupil, and the amount of decentration is estimated in millimeters.

When the corneal light reflex is decentered nasally, an exo deviation is present, whereas a temporal deviation represents an eso deviation. The quality of fixation is also assessed (e.g., jerky, searching, steady, or constant deviation).

The Krimsky test is performed after the MLF and Hirschberg tests if a strabismus has been detected. The clinician uses a correcting prism over the patient's fixating eye to center the light reflected from the cornea of the other eye. The magnitude and base direction of the prism quantify the patient's strabismus.

Unilateral and alternating cover tests are extremely helpful to objectively assess phoric or tropic postures. An interesting, engaging fixation target at distance and near is essential for obtaining optimal cover tests results with retarded or developmentally delayed patients.

The unilateral cover test is used to detect a possible tropic deviation. The procedure is performed by occluding one eye and then uncovering, allowing for fusion to be broken and then re-introduced. Occlude the right eye three or four times, then repeat the procedure for the left. The purpose of the unilateral cover test is to determine which eye tends to fixate under binocular conditions. An eye that moves when the opposite eye is occluded is exhibiting a strabismic deviation; an outward eye movement indicates esotropia, while an inward movement indicates an exotropia.

Placing a compensating prism in front of the deviating eye can measure the angle of the deviation in prism diopters. An esotropia is compensated with a base out prism and an exotropia is measured with a base in prism. If movement is not detected on the unilateral cover test, the alternating cover test is then used to find the phoric posture of the patient’s eyes. The occluder is quickly switched from eye to eye; the goal is to prevent both eyes from seeing the fixation target at all times. The test is repeated until the examiner is confident the results are consistent.

If done properly, the eyes will tend to posture in their habitual position under fusion-free conditions. It is important to occlude the eyes long enough for the eye movement to occur, usually two or three seconds. In this procedure, the examiner looks at the eye that has just been unoccluded. An outward movement indicates an esophoria, an inward movement would be termed exophoria, and no movement is labeled orthophoria.

The alternating cover test deviation can also be measured (or neutralized) with compensating prism. The unilateral cover test is then performed again after the alternating cover test, a latent strabismus may be revealed due to fatigue of the binocular system. Norms for the cover test at near and distdance are six prism diopters exophoria and one-half prism diopter exophoria, respectively. Any deviation on the unilateral cover test is considered abnormal.

The NPC is a procedure that measures the maximum amount of convergence available while maintaining sensory fusion. If possible, the NPC is determined both subjectively and objectively. An engaging target is used to capture the patient's attention and slowly brought toward the patient's nose along the midline from a distance of about 40 cm, 10 to 15 degrees below eye level. The distance at which convergence is lost and one eye swings outward is an objective measure of the NPC break.

The objective NPC recovery occurs when both eyes regain fixation on the target as it is pulled away from the nose. The subjective NPC break occurs when the patient reports that two targets are perceived as it is moved toward the patient’s nose. The subjective NPC recovery occurs when the patient reports that the perception of two targets changes into the perception of one as the fixation target is pulled away from the nose. The results are recorded as break/recovery in centimeters. Norms for this procedure are 6 cm/10 cm.

Relative vergence ranges can be performed at distance and near to determine the limits of convergence and divergence. The tests are considered relative because the accommodative demand remains constant throughout the duration of the test. This test cone be done smoothly in-phoropter with Risley prisms or as “jump” or “step” vergences out-of-phoropter with loose prisms, prism bars, or hand-held Risley prisms. It may be necessary to ensure that the patient understands the concept of diplopia (double vision) by placing a vertical prism in front of one eye. Vergence tests can be done subjectively by having the patient tell you the moment they perceive two targets. Breaks in fusion can be objectively detected during this test by carefully observing the patient's eyes; when the vergence limit is reached, the alignment of the eyes will quickly change. It is customary to take blur, break, and recovery measurements for the test, although it may be difficult for special needs patients to accurately elicit a blur response. (10)

Fig. 13. Out of phoropter vergence test. (Figure from Rosenbloom, Alfred and Morgan, Meredith. Principles and Practice of Pediatric Optometry. JB Lippincott Co., Philadelphia, 1990; page 178.)

The Viewer-Free Random Dot Cube measures depth perception and global stereopsis. There are four targets: a circle, square, “E” and a blank control housed within a plastic cube. The patient views the sides of the cubes and reports if a three-dimensional target is perceived. A benefit of this device is that no polarized lenses are required, which is an advantage for patients who are uncomfortable with the tactile stimulation of wearing lenses and frames.

Fig. 14. Viewer Free Random Dot Cube. (Figure from Bernell Online Store (2004). Retrieved from http://www.bernell.com/store/prodinfo.asp?number=SY100&variation=&aitem=18&mitem=22 on January 16, 2005.

The Lang stereo-tests measure global stereopsis using pictures of common objects (e.g., a cat, a star, and a car) that are printed so that disparate images are seen by the eyes. To perform the test and see images float off the page, the patient must bi-foveate, so this test is very sensitive for detecting small angle strabismus. The images vary in disparity (1200, 600, and 550 arc seconds with Lang I; and 600, 400, and 200 arc seconds with Lang II).

An advantage of the Lang stereo-tests is the composition of the cards; there is a plastic prism overlay on the card that eliminates the need for polarized glasses and helps makes the cards very durable. A disadvantage is that images must be precisely aligned with the patient's visual axes; shifting the cards slightly to the left or right will cause objects to lose their float. The patient must have the ability/motility to point or describe the location of objects (i.e., flat on the page or floating above it) for the test to be administered successfully.

The Random Dot E stereovision test utilizes two test targets, a control target, and polarized glasses to evaluate stereopsis. A raised card blank that provides kinesthetic and tactile feedback to the patient about the hidden shape they will be looking for on the random dot card is presented to the patient to view and feel. Next, the two test targets are presented and the patient is asked which target has the letter “E” on it. An advantage of this procedure is that it is a forced choice test. Another advantage of the test is that although the test card provides just one global demand, the test can be administered at different distances in order to test different disparities.

For example at 50 cm, detection of stimulus float requires a disparity sensitivity of 504 arc seconds, whereas at 16 feet the corresponding disparity is 52 arc seconds. The disadvantage of this test is that polarized lenses are required. A non-verbal patient can perform this test by pointing to the card they identify as containing the floating shape.

To perform the Worth Dot Test, the patient wears red/green glasses over their correction and views a light with four dots (two red, one green, and one white dot) from a distance of 40 cm. The test is administered in normal room illumination.

A person with normal binocularity will see one red dot, two green dots, and will perceive the white dot as a lustrous a mixture of red and green) five dots indicate that the patient is diplopic, and two or three dots indicates that the patient is suppressing the image from one eye.

The Worth Dot Test can be repeated at distance. If there are different numbers of dots seen at the two distances, find the distance from the patient at which there is a change in the number of dots seen. This distance can be used to roughly estimate the extent of the suppression; the angular subtense of the lights on the retina is greater at closer distances, thus the suppression demonstrated may affect more area of the retina. New research suggests that even individuals with clinically normal binocular function may suppress at certain distances, so caution must be used when diagnosing central suppression. The study found that 66% of participants with clinically normal binocular function reported transitory/intermittent suppression at an approximate distance of 3.7 meters and that 77% of the participants demonstrated full suppression at an approximate distance of 4.5 meters. The study suggests that clinicians must observe suppression at distances much closer than 3.7 meters to indicate evidence of abnormal suppression. (11)

A disadvantage of the Worth Dot Test is that the patient can remember that there are four lights, which would allow a "correct" response independent of patient's perception. To prevent this, interchange similar appearing flashlights that have three and five dot patterns or pictures.

The Worth Dot Test measures secondary fusion. It can be administered in primary gaze as well as in different fields of gaze and at different distances to map out the patient's binocular field.

Always start with binocular testing prior to monocular testing because most retarded and developmentally delayed patients do not like occlusion. They may also be overly sensitive to the tactile feel of the occluder as it touches the face.

Many tests, such as Random dot stereograms and the Worth Dot test, require verbal feedback. Take into account the developmental level and response speed of the patient when choosing a test and interpreting results. Match the patient's verbal skills with the verbal skill required by the test.

As a population, special-needs patients are at higher risk for eye movement abnormalities. Often times, these individuals have an under-developed oculomotor system. In order to evaluate eye movement ability, motilities, near point of convergence, pursuits, and saccades should be considered. By identifying eye movement problems, practitioners may be able to improve function through a variety of therapies.

The purpose of evaluating ocular motilities is to assess the extent and symmetry of eye movements. To perform the assessment, instruct the patient to follow your fixation target with only their eyes; it may be necessary to place a hand atop the patient’s head to eliminate head movements. Start 50 cm from the patient and slowly trace a double H with the fixation target: move the light 40 cm to the patient’s right side, then up and then down, then move the light to the primary position, then up and then down, and finally move the light 40 cm to the patient’s left side, then up and then down. Compare both eyes and look for symmetry. The patient should be able to see a single target without experiencing pain or diplopia throughout the double H pattern. The tester should also look for smooth, accurate movements. If a patient has an asymmetric position of gaze, record the over action or limited range of motion.

The quality of eye movements can be evaluated by assessing pursuits and saccades. Pursuits are eye movements that are intended to produce a stable image of moving objects on the fovea. Saccades are quick, ballistic eye movements whose purpose is to bring the image of a peripheral target onto the fovea. Saccades can be voluntary or reflexive while pursuits are thought to have a large cognitive component. (12)

One of the most commonly used and tests for pursuits and saccades is the NSUCO Oculomotor Test. Both the test protocols and norms are available in the test manual. (12a)

Following the NSUCO Oculomotor Test procedures for assessment of pursuits and saccades, have the patient stand (if possible) with their arms at their sides and instruct them to follow a fixation target with their eyes. Hold the target approximately 40 cm from the patient and trace a circle with a 20 cm radius from primary gaze at least two times in a clockwise direction and two times in the counter-clockwise direction. Monitor and record the patient’s ability to complete each rotation, to maintain fixation of the target, and any head or body movements made during the testing. The procedure for evaluating saccades involves two targets. Hold the two fixation targets 40cm from the patient with a target positioned horizontally 10 cm from the right and left of the midline, respectively. If possible, have the patient stand with their arms at their side and feet at shoulder’s width. Have the patient fixate one target and then instruct them to quick look at the other target. Repeat each cycle four more times. It is reasonable to test saccades in vertical and diagonal orientations if more data is desired. Monitor and record any over- or under-shooting of fixation, the ability to complete the task, and any head or body movements.

Nystagmus is an involuntary, rhythmic side-to-side (oscillating) eye movement. Evaluate and characterize any nystagmus, especially in different positions of gaze and different amounts of convergence. If a null point exists, the patient will often take up the appropriate head posture to maintain gaze at the null point during demanding acuity tasks. Consider performing tests with this head position to minimize the effects of the nystagmus.

Do not be surprised to find unique oculomotor presentations with multiply handicapped patients; there may be neurological insults impinging upon different control centers in the oculomotor system.

There are therapies directed at managing eye movement abnormalities, but these are beyond the scope of this course. For further information, consult Optometric Management of Learning-Related Vision Disorders by Mitchell Scheiman and Michael Rouse (13), Applied Concepts in Vision Therapy by Leonard J. Press (14), or Binocular Anomalies: Procedures for Vision Therapy by John R. Griffin.(15)

Color vision can be especially important for multiply-handicapped patients because some communication and education strategies for are based on color-coded stimuli.

The CVTME test is effective for special needs patients and is relatively easy to administer. It is most appropriate for patients who have a developmental age of three years and above.

The test consists of fourteen pseudoisochromatic plates showing easily identifiable and engaging objects, e.g., boat, circle, dog, and star. The cards work well with special needs patients because of the test design. Each card in the set contains two symbols; the first six plates have one symbol that even a color deficient person should be able to identify. This is useful because it ensures the patient understands the test, prevents patients from feeling discouraged or self-conscious, and demonstrates the patient is putting forth a genuine effort.

If the patient is unable to verbally communicate, the test can be performed by asking him or her to use a small artist's paintbrush or cotton-tipped applicator to trace objects on the plates. To prolong plate life, do not let patients use fingers for tracing.

Pseudochromatic color plates are presented to the patient and he/she is asked to identify any shapes or numbers that are seen. Patients with defective color vision see no shapes or shapes that are different from the ones seen by normals. Like the CVTME, the Ishihara test can be administered by having the patient trace shapes on the plates with small artist's brush.

The Wool/Yarn test is performed by having the patient match colored swatches of yarn to standard swatches. This test can be used when other color tests are unsuccessful or inappropriate for the developmental age of the patient. The practitioner can get a rough idea of chromatic challenges based on colors of yarn the patient has trouble matching.

Ideally, visual fields should be measured with bowl-type automated perimeters, but few retarded patients can concentrate on the test and hold fixation for the time required to obtain a full set of fields. For this reason, fields are commonly measured using confrontation techniques.

An interesting target is used to keep the patient's attention directed straight ahead. Then a penlight or trans-illuminator is moved in from the periphery until the patient detects it. Sometimes it is necessary to have an assistant or the patient’s caregiver stand behind the patient and move the peripheral stimuli into the patient’s field of view. Observe the patient’s position of the stimulus when the patient first detects it and repeat the test in other field orientations to map the full field. It is also possible to have the patient look straight ahead and then flash a light in the patient’s periphery while monitoring head and eye movements to detect the extent of the visual field.

Take into account possibly slowed patient responses when mapping the field. If the stimulus is moved too fast or response latency is not considered, an artifactually constricted field will be found.

Tests of accommodation are especially important for special-needs patients because accommodative problems can be treated relatively easily with lenses or therapy.

The retinoscope is an invaluable tool for objectively accessing accommodation when phoropter procedures or lens tests produce equivocal results. If accommodative amplitude, facility, and posture fall within normal ranges, the clinician can usually be confident that the accommodative system is functioning properly.

To determine amplitude of accommodation, attach an age-appropriate fixation card to the retinoscope and begin scoping at a distance of 40 cm. Have the patient call out the shapes or letters on the card or ask him or her to find certain objects or letters on the card. Slowly decrease the distance to the patient until there is a sudden change to with motion of the retinoscope streak. The dioptric equivalent of the distance at which this occurs is the objective amplitude of accommodation. (16)

Perform the procedure binocularly. If a large lag value or leading posture is noted, perform the test monocularly to see what effects convergence has on the accommodative system. The minimum amplitude of accommodation expected depends on the age of the patient and can be determined from the Hofstetter formula: Minimum amplitude of accommodation (diopters) = 15 - (0.25 x age of patient in years).

The patient should have twice the amplitude required for any near demand. For example, a patient with a 33 cm working distance should have an amplitude of six diopters or more to function comfortably. Near lenses or visiion training may be prescribed to alleviate problems arising from insufficient amplitude of accommodation.

MEM retinoscopy is useful for objectively estimating the accommodative response at near. Adjust the room illumination to a level that is appropriate for reading and have the patient wear his or her best correction. Attach an age-appropriate MEM target that has either age appropriate words or pictures to a retinoscope and present it at the patient’s near working distance. Pass a vertical streak along each eye with the retinoscope and estimate the amount and direction of streak movement. With motion indicates an accommodative lag, and against motion indicates a lead. Quickly place a lens to compensate for the lead or lag in front of the patient’s eye and pass the streak back and forth again. Repeat the procedure until neutral is found. (16) Patients who demonstrate excessive lag amounts or leading postures may benefit from a near prescription or accommodative training.

MEM retinoscopy is most commonly performed at the patient’s habitual near working distance. If a habitual working distance cannot be determined subjectively, practitioners can estimate an approximate working distance by using the Harmon distance, or the distance between the point of the elbow to the middle knuckle on the patient.

The acuity demand of the target also changes the expected accommodative lag. With a 20/100 (6/30) target at 40 cm, the examiner would expect a lag of 0.62 diopter, whereas a 20/30 (6/9) demand target would be expected to reduce the lag to 0.25 diopter.

Facility of accommodation indicates flexibility of the accommodative system and the ease or difficulty with which a patient can shift focus from near to far and vice versa. To test facility subjectively, plus and minus 2.00 diopter lens flippers are alternately placed in front of the patient while his/her attention is directed to an age-appropriate threshold level acuity target, such as letters or detailed, high contract images. Every time the patient indicates that the target is in clear focus, the lens are flipped to the opposite dioptric power and the patient is instructed to again communicate when the image is clearly focused. One cycle occurs when the patient clearly focuses the target through both the negative lens and the positive lens; achievement of less than 10 cycles per minute indicates a lack of function of the accommodative system.

If the patient is unable to subjectively complete the task, a retinoscope can be used to objectively measure the status of the accommodative system. First, a baseline posture is noted with only the habitual prescription in place. This value is determined by using the MEM retinoscopy procedure described above. Once a baseline state of accommodation is established, plus and minus 2.00 diopter lens flippers are placed before the patients eyes while they are asked to focus on the letters or pictures on the age appropriate fixation card attached to the retinoscope. The lens placed before the patient while performing near retinoscopy allows the doctor to see how quickly the patient can recover from an accommodative stimulus and gives the practitioner an idea of how long it takes the patient to clearly “grasp” the target. It should take no longer than three seconds to regain the habitual baseline posture between lens flips. (16) Patients who need an extended time to return to their baseline posture may have a facility problem (or a cognitive problem). Accommodative facility difficulties can be treated by prescribing vision therapy or near lenses.

Multiply-handicapped children, particularly those with cerebral palsy, often exhibit accommodative paresis or spasm. (17)

As a population, individuals with developmental disabilities tend to under-accommodate.

Retinoscopy provides an objective measurement of refractive error and is often the most useful means of determining the refractive status with special-needs patients. Static retinoscopy is performed out-of-phoropter with working distance lenses (typically +1.50 diopter) in place to fog the patient. A lens rack is used to help measure refractive errors.

The most difficult aspect of retinoscopy is keeping the patient's fixation in the distance for the time needed to complete testing. An interesting target such as a puppet or a cartoon/movie can help the patient hold fixation. It is important to note that abnormal head postures can produce artifactual cylinder axes.

Mohindra retinoscopy, which is a type of near dynamic retinoscopy, is another objective technique for determining refractive error. The test is performed in a dark room with the retinoscope 50 cm from the patient. One of the patient's eyes is occluded and he or she is instructed to focus on the retinoscope light.

The distance refractive error is determined by adding –1.25 D to the gross sphere power obtained during retinoscopy. This technique can be used for infants and severely handicapped patients because of the strong tendency to look directly at the retinoscopy light.

Cycloplegic retinoscopy is performed in the same manner as for a normal patient. This test can be especially helpful for patients with accommodative fluctuation or other abnormalities because the cycloplegic agent tends to relax the accommodative system. Cyclopentolate® is considered the drug of choice for cycloplegic examinations, but tropicamide can be substituted.

It is important to note that the effect and duration of accommodative relaxation produced by tropicamide is less than that produced by cyclopentolate. Cyclopentolate (0.5 to 2.0%) produces mydriasis and cycloplegia in 30 to 60 min and these effects last up to 24 hours. Tropicamide (0.5 to 1.0%) produces mydriasis and cycloplegia in 20 to 35 min and these effects last up to 6 hours.

If nearly complete cycloplegia is required, atropine 0.5 to 3.0% can be administered over a series of days. Atropine takes effect in 60 to 180 min, and its effects last up to 12 days.

Autorefraction (AR) is useful as a back-up to retinoscopy, especially to help determine difficult astigmatic powers and axes. AR is performed in the same manner as with normal patients.

Difficulties often encountered with autorefraction include fixation maintenance and proximal accommodation. Cycloplegia improves autorefraction accuracy and reliability. (18)

Corneal irregularities and astigmatism can be estimated from the pattern light reflected from the cornea. A keratocope, consisting of illuminated concentric rings and a viewing aperture, is aimed at the patient's eye while the ring reflections are viewed by the clinician. Irregularities in the rings can indicate corneal distortion and astigmatism.

A direct ophthalmoscope can be utilized to determine gross refractive error when other methods are ineffective. To perform the test, position the ophthalmoscope vertically about 40 cm from the patient and observe the red retinal reflexes through the ophthalmoscope.

When a refractive error is present, crescent-shaped reflexes (like phases of the moon) will appear due to the relative position of the illuminated retinal area. A thin, light crescent or no crescent indicates the absence of significant refractive error. As the power of the refractive error increases, the crescent size also increases.

Generally, a half-full pupil crescent indicates about two to three diopters of refractive error, a quarter-full indicates about one diopter, and a three-quarters-full pupil indicates a three to six diopter refractive error range. Higher refractive errors (6 D or more) can be difficult to observe because the crescent fills the pupil. (19)

To determine whether a crescent indicates myopia or hyperopia, the orientation of the crescent relative to the position of the ophthalmoscope is observed. A crescent that forms towards the head of the ophthalmoscope indicates hyperopia; a crescent oriented towards the bottom of the scope indicates myopia.

Fig. 22. Orientations and Sizes of the Refractive Crescents. (Figure from Lowery, JP. (2003) Screening Children for binocular and refractive conditions with the direct ophthalmoscope. Pacific University College of Optometry.)

When the ophthalmoscope is oriented vertically, powers in the 90th meridian (axis 180 correction) are determined. Rotating the scope to a horizontal orientation allows determination of powers in the 180th meridian (axis 90 correction). By comparing these findings, the amount of astigmatism can be estimated.

The refraction should done out-of-phoropter with a trial frame or with Halberg or Janelli clips over an existing spectacle correction.

The dioptric power necessary to obtain a clear view of the fundus using a direct ophthalmoscope can be helpful in estimating the refractive error. To estimate the refractive error, subtract the doctor’s uncompensated refractive error from the total power displayed on the ophthalmoscope.

If uncertain about the results of the refraction, have the patient return to the clinic repeat retinoscopy and confirm previous findings prior to prescribing.

Corneal abnormalities are more prevalent among special-needs patients (e.g., keratoconus in Downs Syndrome patients).

Keratometry allows a quick evaluation of the tear film integrity by observing the time between a blink and mire distortion due to tear breakup.

GAT is considered the gold standard for determining intraocular pressure. Disadvantages to Goldmann for a special-needs population include the need to instill anesthetic drops, obtaining cooperation for fixation, uncomfortable postural demands, and patient apprehension about instruments touching or coming close to the eyes. Often GAT can be difficult or impossible to perform with retarded or developmentally delayed patients.

The Tono-Pen® is small, handheld, and unobtrusive, and it can be easily be used with patients in wheelchairs. Other advantages include the ability to take multiple, quick measurements and the option to review results at a later time. The Tono-Pen® is excellent for use with irregular shaped corneas (many special-needs patient have corneal abnormalities and/or significant corneal astigmatism). Disadvantages are similar to those of GAT. An anesthetic is required and the eye must be approached and touched to obtain pressure readings.

Non-contact tonometry is useful when patients are apprehensive about the instillation of drops or having their eyes touched. However, this test is difficult to use when the patient is unable to maintain fixation or physically unable to sit in front of table-mounted instruments. Patient apprehension can be reduced by use of phrases such as, "the puff is like a monkey kiss" and demonstrating the puff of air delivered by the apparatus on the patient’s hand.

The Keeler Pulsair® tonometer is useful for determining IOPs with special-needs patients because the measuring part of the unit can be brought to the patient. This makes it useful for wheelchair-bound patients. Also, it does not have to come as close to the eye as required by other tonometers, and the air puff is gentler than the puff generated by some other instruments. Before taking a reading, explain and demonstrate the puff of air on the patient’s hand.

Advantages of pneumatic tonometry include low probability of infectious disease transmission because nothing touches the eye, no anesthetic or staining required, and the relative ease of use. A disadvantage is that the Pulsair® does make some noise, which may make patients wary. The cordless Reichert PT100 Portable NCT® is similar to the Keeler Pulsair®.

When pressures cannot be obtained using instruments because of physical limitations or patient anxiety, digital sampling tension can be used. The study "Assessment of intraocular pressure in children by digital tension" demonstrated that digital tension estimation was valid, especially in the normal (i.e., 6 to 22 mmHg) range. (20)

To perform digital tension estimation, have the patient close the eyes while looking down. Use one finger to steady the eye in position against the orbital fat, then apply pressure with a second finger above the tarsal plate. The relative softness or hardness of the eye can be determined by feeling the globe's resistance to pressure. Record the pressure as low, moderate, or high and whether a difference was noted between the eyes.

Gross inspection of anterior segment structures can be completed using a magnifying loop or a direct ophthalmoscope with some added plus power. A plus 20 diopter lens and a penlight can also be used to assess lids/lashes, conjunctival health, and corneal clarity.

Limbal glow can be used to check the anterior chamber angles and detect a bowed iris (iris bombe), which may suggest a propensity for angle closure. (21) Place the trans-illuminator to the temporal side of the patient's face approximately 3 cm lateral to the orbit and slightly posterior. Ask the patient to open his/her eyes widely and then rotate the trans-illuminator so that it is parallel with the cornea laterally and approximately perpendicular to the nose. Observe the amount of glow that is transmitted through the chamber angle and that is visible on the nasal side of the globe. A shadow on the nasal iris suggests bombe; uniform illumination suggests a flat iris.

A hand-held slit lamp is valuable when working with patients who are unable to move into the exam chair.

Turning down the BIO illumination may encourage the patient to cooperate more fully during this procedure. Patients with severe developmental disabilities are often unwilling or unable to sit for funduscopy even with reduced illumination. In such cases taking fundus pictures, using a scanning laser ophthalmoscope or one of the procedures described below, or, as a last resort, general anesthesia might be necessary. (22)

A direct ophthalmoscope, monocular indirect ophthalmoscope (e.g., PanOptic® Ophthalmoscope or Keeler Wide Angle Dual Magnification Scope®) can be used to examine the posterior pole of patients who cannot be dilated. A key factor when using these instruments is getting the patient to maintain a steady fixation. To accomplish this, it may be necessary to utilize the patient’s caregiver or an assistant.

This procedure is performed in a manner similar to binocular indirect ophthalmoscopy, but does not require the patient to be dilated. The clinician holds a plus 20 diopter lens directly in front of the patient’s eye while viewing the fundus through a direct ophthalmoscope from a distance of approximately 30 cm. An advantage of this technique is that relatively low light intensity is needed, which may encourage patient cooperation, but some practice is required to obtain good views of the fundus.

At the conclusion of an examination with a retarded or developmentally delayed patient, findings should be thoroughly discussed, documented, and presented to parents, caregivers, and educators. (Of course HIPAA regulations or other privacy requirements should be followed when deciding with whom to share results.) Complete documentation and implications of all findings are required because examination reports will often be used by persons without a special knowledge of vision care terms or procedures.

With special-needs patients, it is best to avoid the term normal. It is better to make comparisons. For example, “A person with good sight would see this, and you are seeing this because…” Be sure to emphasize any positive findings. Most special-needs patients are acutely aware of their limitations and shortcomings. Professionals should attempt to foster confidence and pride in their patient's strengths and successes whenever possible.

The importance of prescribing lens corrections for special-needs patients was established in a study by Bader and Woodruff who concluded that positive behavioral changes resulted from refractive error correction. (23) As might be expected, the earlier the age at which a correction is worn, the more significant the impact on behavior will be.

Bader and Woodruff also demonstrated that patients who wore spectacle corrections improved their gross motor skills, and, more importantly, their fine motor skills. Patients were better able to print their names and other simple words from memory. In addition, patients who were suffering from anisometropia benefited significantly from an effective lens correction.

The patient’s habitual posture should be taken into account relative to head, neck, and trunk control. If bifocals are prescribed, first determine whether the patient has adequate oculomotor control and spatial awareness to properly utilize both the upper and lower portions of the lenses. Bifocals may not be appropriate if the patient cannot move his/her head to use the distance portion of the lenses when walking. The lenses may become an impediment to mobility in such cases. A better option may be to prescribe two sets of single-vision lenses for these patients.

When prescribing multiple single-vision lenses, it is important that the frames are easily distinguishable by both the patient and busy caregivers. That way, confusion as to which pair is for distance and which is for near can be minimized. Pay special attention to any fitting adjustment that need to be made in order for the patient to be comfortable with the spectacles.

When scheduling the first exam with a special-needs patient, plan on a minimum of one hour for the first visit so that the patient can gradually adapt to the environment of the clinic. Multiple visits may be required to complete a comprehensive vision examination.

If a patient is uncooperative or fearful, consider completing the functional portion of the exam during the first visit and rescheduling the dilation for a later visit.

Involve the patient and the caregiver in the examination to the greatest degree possible.

Get the patient to respond at the outset of the exam to increase rapport and make him or her more likely to participate later in the examination.

Use the highest level assessment procedures possible given the patient’s developmental level.

Be flexible with testing and switch to an alternative test whenever difficulty is encountered.

In order to maintain interest and conserve attentional resources, utilize brief testing sessions interspersed with conversation (or even play) breaks.

Be generous with sincere praise for participation. Encourage the patient to feel positive about their performance.

Whenever possible, illustrate, diagram, and use concrete examples of what you want the patient to do.

Sprinkle novel attention grabbers throughout your exam to maintain a high level of upcoming surprise anticipation. Use care not to present items that may become a distraction rather than a tool.

Special-needs patients are often taking multiple drugs. Confirm that they have taken all the recommended dosages for the day and that they are functioning at their normal level. Be aware of which drugs affect accommodation and acuity.

If the patient is more comfortable being in area other than the examination room and moving would not prevent gathering valid data, consider finding another location for testing.

If the patient is uncooperative or apprehensive about diagnostic drops, it may be easier to allow the patient to close his/her eyes while drops are applied to the respective medial canthi. Gently lift the upper lid to allow the drops to dissipate and occlude the nasolacrimal duct for about one minute after instillation. (24) It may be particularly useful for the patient to “practice” receiving eye drops by having a caregiver instill artificial tears at home a few days before the actual examination.

Whenever the developmental level of the patient permits, utilize subjective test responses to augment objective test results.

Special-needs patients often have a strong desire to please the clinician. They may try memorizing acuity tests or responding in a manner they perceive will not disappoint the examiner. Random presentation sequences in acuity and other tests will reduce the effects of this behavior.

Working with special-needs populations can be financially and professionally fulfilling if the practitioner has the requisite skills and resources. Having trained staff members to help with testing can reduce examination time and increase patient comfort.

Currently the special-needs population is visually under-served. The few clinicians who have made special-needs patients their specialty are insufficient to meet the need.

To quote Warburg, "The best way to learn how to work with this population is to be exposed to them, be around them. We have the duty to serve them because what has been done in the past has not been enough to meet their needs." (25)

Appendix I provides a listing of sources where tests mentioned in this course can be obtained. Appendix II is a compendium of tests organized by visual function. Each test has been subjectively ranked by the authors as to its appropriateness for a variety of handicaps including speech, hearing, motor and cognitive development.

Many of the test items described in the course can be obtained from the following general equipment suppliers:

	Hearing Impairment and Developmental Age of Two Years	Motor Impairment and Developmental Age of Two Years	Mute Patient with Developmental Age of Two Years	Hearing Impairment and Developmental Age of Six Years	Motor Impairment and Developmental Age of Six Years	Mute Patient with Developmental Age of Six Years
Visual Acuity
Snellen	1	1	1	4	4	4
HOTV	1	1	1	4	4	4
Lea Symbols	4	4	4	3	3	3
Broken Wheel	1	1	1	4	4	4
Lighthouse Flash Card	4	4	4	3	3	3
Teller Acuity Cards	4	4	4	2	2	2
Cardiff Cards	4	4	4	2	2	2
Bailey Hall Cereal Test	3	1	3	2	1	2
CBVAT	3	1	3	2	1	2
OKN Drum	3	3	3	3	3	3
Binocular Vision
Bruckner	4	4	4	4	4	4
Hirschberg	4	4	4	4	4	4
Monocular Light Fixation	4	4	4	4	4	4
Krimsky	4	4	4	4	4	4
Cover Test	3	3	3	4	4	4
Near Point of Convergence	4	4	4	4	4	4
Random Dot Cube	2	2	2	4	4	4
Lang Stereo Test	4	4	4	4	4	4
Random Dot E Test	2	2	2	4	4	4
Worth Dot Test	1	1	1	4	4	4
Color Vision
Color Vision Testing Made Easy	2	2	2	4	4	4
Ishihara	2	2	2	4	4	4
Wool Yarn Test	3	3	3	3	3	3
Accommodation
Retinoscope Push-up Amplitude	4	4	4	3	3	3
Flipper Facilities	3	3	3	4	4	4
MEM	3	3	3	4	4	4
Refraction
Static Retinoscopy	4	4	4	4	4	4
Mohindra Retinoscopy	3	3	3	3	3	3
Cycloplegic Retinoscopy	4	4	4	4	4	4
Autorefractor	2	2	2	4	4	4
Keratometry	2	2	2	4	4	4
Keratoscope	3	3	3	3	3	3
Refractive Crescents	2	2	2	2	2	2
Intraocular Pressure
Goldmann	4	4	4	4	4	4
Tono-Pen	4	4	4	4	4	4
Keeler Pulsair	4	4	4	4	4	4
NCT	4	4	4	4	4	4
Digital Manual	2	2	2	2	2	2
Anterior Segment Examination
Gross Inspection	2	2	2	2	2	2
20 D Lens and Penlight	3	3	3	3	3	3
Limbal Glow	3	3	3	3	3	3
Ophthalmoscope	3	3	3	3	3	3
Stationary Slit Lamp	4	4	4	4	4	4
Hand-Held Slit Lamp	4	4	4	4	4	4
Posterior Segment Examination
Dilated Exam with BIO	3	3