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Volume 2 - The Diagnosis of Amblyopia
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Lecture 5 of 24 NEXT»
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Fixation - Preference for fixation with the same eye is easily observed in the infant
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Infant looks with one eye on examiner |
Pushes away "nonthreatening"occlusion - cries when preferred eye occluded |
Happy with occluder removed resumes fixation with preferred eye |
The above observation sequence confirms better vision in the right eye. The eye with better vision is always preferred and is called the fixing eye. Examination is then carried out to rule out an organic defect of the left eye in this case such as optic atrophy, coloboma, etc. If no organic cause is found, amblyopia can be diagnosed. If the refractive error is small and refraction is equal or nearly so meaning no anisometropia is found, patching is started. (Glasses are rarely needed unless the patient is highly ametropic or anisometropic.)
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Child always has one eye covered |
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If the child is under 1 year as shown in the example above you
can treat as follows:
1) Patch right eye (preferred eye with good vision) 3 days - THEN
2) Patch left eye 1 day (this allows good eye to maintain vision avoiding iatrogenic amblyopia)
3) Repeat above cycle each 4 days
4) Examine in two to four weeks |
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Vision testing can be successful beginning at age 3:
Pictures are less sensitive
Passing Screening:
With vision of 20/40 or better and with no more than one line difference in vision between the eyes, a child passes vision screening. At least 3 optotypes should be used at threshold (crowding). For best results with treatment, amblyopia should be detected by screening as early as possible after the 3rd birthday and before the 5th birthday. Prevent Blindness America suggests also passing a stereo acuity test using a random dot E at near. The child must be correct on 3 out of 4 options to pass. Passing this test also confirms alignment, but can be difficult for the younger child.
Photoscreening of infants has been promoted for its objective identification of strabismus, ametropia, and anisometropia in infants and preverbal children! Detection of these amblyopiogenic conditions at a younger age has the advantage of enabling earlier amblyopia treatment.
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Inequality of pupillary reflex is telltale in strabismus. If there is strong preference, it suggests amblyopia. If the eyes look aligned but the light reflex is abnormal, this could indicate anisometropia which is highly amblyopiagenic or high refractive error. |
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High hyperopia |
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Unequal reflex in strabismus/anisometropia |
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Symmetric typical abnormal reflexes |
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High myopia |
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Normal |
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Symmetric abnormal reflexes |
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Symmetric normal reflexes |
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Photoscreening raises the following issues:
1) Expense
2) Requires skilled interpretation
3) Sensitivity - specificity (accuracy) has not been established
Photoscreening as a technique for mass screening has not yet reached wide acceptance.
Who screens? Vision screeners must emphasize that a comprehensive examination has not been done. Screening simply points out that the child's vision status indicates the need for thorough examination which will determine if treatment is indicated - screening is best done by a non-ophthalmologist - non professional - or at least it should be done in a non professional capacity with no suggestion that all pathology has been ruled out - vision screening only indicates that visual acuity is at a passing level or not. Passing vision screening simply means that visual acuity has been shown to be at least at a specific level. Ideal screeners include:
1) Parents or other lay volunteers trained to screen - for eye health screening from birth to 3 years see Strabismus Minute, Vol. 2, No.1 and 2, "Warning Signs of Serious Eye Disease in the Newborn and Infant" (Part 1 and 2), Feb. 7, 2000 and Feb. 21, 2000
2) Pediatricians - family physicians - in office screening
3) School nurses (but screening most effective if done pre-school)
4) Professional vision screeners
The Strabismus Minute
, Vol.2, No. 5 Copyright (C) 2000 Eugene M. Helveston All Rights Reserved
Editor-in-Chief: Eugene M. Helveston, M.D.
Associate Editor: Faruk H. Orge, M.D.
Editorial Board: Bradley C. Black, M.D.
Edward R. O'Malley, M.D.
David A. Plager, M.D.
Derek T. Sprunger, M.D.
Daniel E. Neely, M.D.
Naval Sondhi, M.D.
Senior Editorial Consultant: Gunter K. von Noorden, M.D.
Graphics: Michelle L. Harmon
Technical Support: George J. Sheplock, M.D.
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