12/02/2022
AMBLYOPIA
Symptoms:
➡️Usually none.
➡️Usually found when decreased vision is detected by vision testing in each eye.
➡️Individual letters are more easily read than a full line (crowding phenomenon).
➡️In reduced illumination, the visual acuity of an amblyopic eye is reduced much less than an organically diseased eye (neutral-density filter effect).
Signs:
➡️Poorer vision in one eye that is not improved with refraction and not entirely explained by an organic lesion.
➡️The involved eye nearly always has a higher refractive error.
➡️Central vision is primarily affected, while the peripheral visual field usually remains normal.
➡️Amblyopia, when severe, may cause a trace relative afferent pupillary defect
Etiology:
➡️Strabismus: Most common form (along with anisometropia). The eyes are misaligned. Vision is worse in the consistently deviating, nonfixating eye. Strabismus can lead to or be the result of amblyopia.
➡️Anisometropia: Most common form (along with strabismus). A large difference in refractive error (usually 21.50 diopters) between the two eyes. Can be seen in cases of eyelid hemangioma or congenital ptosis inducing astigmatism.
➡️Stumulus deprivational(Media opacity): A unilateral cataract, corneal scar, or PFV/PHPV may cause a preference for the other eye and thereby cause amblyopia.
➡️Occlusion: Amblyopia that occurs in the fellow eye as a result of too much patching or excessive use of atropine.
- Prevented by examining at appropriate intervals (1 week per year of age), patching part-time, or using the full cycloplegic refraction when using atropine.
➡️Toxic amblyopia : With use of alcohols/drugs
➡️Meriodonal amblyopia: Uncorrected high astigmatism.
Treatment:
➡️Appropriate spectacle correction (full cycloplegic refraction or reduce the hyperopia in both eyes symmetrically 21.50 diopters). If vision remains reduced after period of refractive adaptation (6 to 12 weeks), begin patching or penalization of fellow eye.
➡️Patching: Patch the eye with better corrected vision 2 to 6 hours/day for 1 week per year of age, with at least 1 hour of near activity. Adhesive patches placed directly over the eye are most effective. A patch can be worn over the glasses as long as the child does not peek around the patch. If a patch causes local irritation, use tincture of benzoin on the skin before applying the patch and use warm water compresses on the patch before removal.
➡️Penalization with atropine: Atropine 1% once daily (used with glasses) has been shown to be equally effective as patching in mild-to-moderate amblyopia (20/100 or better). If vision does not improve, the effect of the atropine can be increased byremoving the hyperopic lens from the glasses of the nonamblyopic eye. If the child is experiencing difficulty with school work with the use of atropine, he/she can wear full hyperopic correction with a +2.50 bifocal during school.
➡️Optical degradation: Use a high plus lens (e.g ., +9.00 diopters or an aphakic contact lens) to blur theimage.If the child is highly myopic, may remove the minus lens from the preferred eye.
➡️Continue patching until the vision is equalized or shows no improvement after three compliant cycles of patching. If a recurrence of amblyopia is likely, use part-time patching to maintain improved vision.
➡️If occlusion amblyopia (a decrease in vision in the patched eye) develops, patch the opposite eye for a short period (e.g ., 1 day per year of age), and repeat the examination.
➡️In strabismic amblyopia, delay strabismus surgery until the vision in the two eyes is equal, or maximal vision has been obtained in the amblyopic eye.
➡️If treatment of amblyopia fails or patient presents outside of treatment age range, protective glasses should be worn to prevent accidental injury to the nonamblyopic eye.Any child who does not have vision improved to at least 20/40 needs to wear eye protection during sports (one-eyed athlete rule).
➡️Treatment of media opacity: Remove the media opacity and begin patching the nonamblyopic eye.
➡️Treatment of anisometropic amblyopia: Give the appropriate spectacle correction at the youngest age possible. If vision remains reduced after period of refractive adaptation (6 to 12 weeks), begin patching or penalization of fellow eye.
