A 12-year-old child presented with right eye vision of 6/36 and left eye vision of 6/6. On retinoscopy at 66 cm, the right eye showed 4.5 D and left eye 1.5 D in both axes. The anterior chamber and fundus were normal. What is the cause of the decreased vision in the right eye? (LQ)
|D||Occipital lobe lesion|
Amblyopia is the unilateral, or (rarely) bilateral decrease of best corrected visual acuity caused by vision deprivation and/or abnormal binocular interaction, for which there is no pathology of the eye or visual pathway.
1. Strabismic amblyopia results from abnormal binocular interaction where there is continued monocular suppression of the deviating eye.
2. Anisometropic amblyopia is caused by a difference in refractive error between the two eyes.
3. Stimulus deprivation amblyopia results from vision deprivation eg. cataract or severe ptosis.
4. Iso-ametropic amblyopia results from vision deprivation. It is bilateral and caused by high symmetrical refractive errors usually hypermetropia.
5. Meridional amblyopia - caused by uncorrected astigmatism.
1. Visual acuity in amblyopia is often better while reading single letters than a row of letters.
2. crowding phenomenon Q
3. Neutral density Q filter (a) No significant drop in visual acuity implies amblyopia (b) A single drop in visual acuity implies an organic lesion.
4. Grating acuity Q - (ability to perceive a grid pattern of different frequencies) often exceeds spatial (snellen) acuity.
**Vision fields and colour visions are normal Q
1. The sensitive period during which amblyopia can be reversed is up to 7-8 years in strabismic amblyopia and longer (up to 11-12 years) for anisometropic amblyopia
2. Occlusion of the normal eye to encourage use of the amblyopic eye is the most effective treatment.
3. Penalization- alternative method, it may be used in relatively mild amblyopia (6/24 or better) in association with hypermetropia.