Amblyopia

1. Amblyopia F. Kianersi M.D. Isfahan University of Medical Sciences 1390 / 1 / 25 بنام خداوند جان وخرد

2. Amblyopia Sometimes called “lazy eye” characterized by: Uncorrectable, decreased visual acuity in an otherwise normal eye. Definition includes an operated eye made “structurally normal” by surgery (e.g. post cataract surgery).

3. Amblyopia: History “When the doctor sees nothing and the patient sees nothing, the diagnosis is Amblyopia.” Hippocrates, 450 B.C.

4. Amblyopia Onset early in life (typically before age 6). Amblyopia may be unilateral (most common) or bilateral. It is the most common cause of monocular vision loss in children and young adults. Prevalence: 2%-4% of population.

5. Amblyopia • Best-corrected Snellen V/A in amblyopic eyes range from mild deficits (20/25) to severe vision loss (≤20/400). • The accepted definition of clinically significant Amblyopia is BCVA ≤20/40 or a difference of 2 lines of Snellen acuity between the amblyopic eye and the normal eye.

6. Degree ofAmblyopia • Slight • BCVA: 0.6 - 0.8 • Middle • BCVA: 0.2 - 0.5 • Severe • BCVA: ≤ 0.1

7. Neurophysiology • Amblyopia is primarily a defect of central vision. • Cells of the primary visual cortex can completely lose their innate ability or show significant functional deficiencies. • Abnormalities also occur in neurons in the lateral geniculate body. • Evidence concerning involvement at the retinal level remains inconclusive.

8. Classification • Amblyopia is usually classified on the basis of its associated clinical condition. • Two basic conditions set up the developing visual system for failure and result in Amblyopia: • Abnormal binocular interaction (eg, Strabismus), • Blur/distortion of the visual image due to Uncorrected Refractive Errors or Media Opacities.

9. Classification • Strabismus Amblyopia (Misaligned eyes) • Anisometropic Amblyopia (Refractive Amblyopia) • Deprivation Amblyopia (Media opacity) • Multiple or “Mixed” mechanisms often are involved.

10. Amblyopia: Three Main Types Strabismic Amblyopia Anisometropia Amblyopia Deprivation Amblyopia

11. Strabismus Amblyopia • The most common form of Amblyopia. • Occurring in at least 40% of children with manifest Strabismus (usually Esotropia).

12. Strabismus Amblyopia • Strabismic Amblyopia is thought to result from competitive or inhibitory interaction between neurons carrying the nonfusible inputs from the two eye. • Which leads to domination of cortical vision centers by the fixating eye and chronically reduced responsiveness to the nonfixating eye input.

13. Strabismus: Esotropia Infantile Esotropia Poor ability to develop binocular fusion, Amblyopia or alternating fixation.

14. Strabismus: Esotropia Accomodative Esotropia Amblyopia common, More Hyperopic eye tends to cross and become Amblyopic.

15. Strabismus: Accomodative Esotropia If eyes straight with glasses: Amblyopia partly “self-treats” since both eyes are being used simultaneously. If eyes remain crossed with glasses: Fusion lost, Amblyopia worsens.

16. Strabismus: Exotropia Often have good fusional ability, Amblyopia less common than with Esotropia.

17. Amblyopia: Three Main Types Strabismic Amblyopia Anisometropia Amblyopia Deprivation Amblyopia

18. Anisometropia Amblyopia Second in frequency. Clear input to the visual cortex is required to develop good vision. When unequal refractive error in the tow eyes causes the image on the one retina to be chronically defocused AnisometropiaAmblyopiadevelops.

19. Anisometropia Amblyopia • Mild Hyperopic or Astigmatic Anisometropia (1-2D) can induce Mild Amblyopia. • Mild Myopia Anisometropia (less than -3D) usually doesn't cause Amblyopia. • Unilateral High Myopia (-6D) often result in Sever Amblyopic visual loss.

20. Ametropic Amblyopia • Large, approximately equal , uncorrected refractive errors in both eyes of a young child cause Bilateral reduction in acuity that is usually relatively Mild. • Hyperopia exceeding about 5 D and Myopia in excess of 10 D carry a risk of inducing Bilateral Amblyopia.

21. Meridional Amblyopia • Uncorrected Bilateral Astigmatism in early childhood may result in loss of resolving ability limited to the chronically blurred meridians. • The degree of Cylindrical Ametropia necessary to produce Meridional Amblyopia is not known, but most ophthalmologists recommend correction of greater than 2 D of cylinder.

22. Amblyopia: Three Main Types Strabismic Amblyopia Anisometropia Amblyopia Deprivation Amblyopia

23. Deprivation Amblyopia • It is usually caused by congenital or early acquired media opacity. • This form of Amblyopia is the least common but most damaging and difficult to treat.

24. Deprivation Amblyopia • Best example: Monocular Congenital Cataract. • Any opacity preventing light from reaching the retina: • Ptosis • Corneal scar/opacity • Forceps injury at birth • Hereditary abnormalities • Vitreous opacity, Hemorrhage

25. Deprivation Amblyopia • The most severe vision loss due to Amblyopia can be found In cases of untreated pattern deprivation during the first 3 months of life, • Vision may be reduced to HM or even LP.

26. Deprivation Amblyopia • In children younger than 6 years, dense Congenital Cataract that occupy the central 3 mm or more of the lens must be considered capable of causing Sever Amblyopia. • Small Polar Cataracts & Lamellar Cataracts may cause mild to moderate Amblyopia or may have no effect on visual development.

27. Occlusion Amblyopia • Occlusion Amblyopia is a form of deprivation caused by excessive therapeutic patching.

28. Organic Amblyopia • Amblyopia sometimes coexists with visual loss directly caused by an uncorrectable structural abnormality of the eye such as Optic Nerve Hypoplasia or Coloboma. • When such a situation (“Organic Amblyopia") is encountered in a young child, it is appropriate to undertake a trial of occlusion therapy; improvement in vision confirms that Amblyopia was indeed present.

29. Diagnosis • Amblyopia is diagnosed when reduced V/A cannot be explained entirely on the basis of physical abnormalities and is found in association with a history or finding of a condition known to be capable of causing Amblyopia.

30. Diagnosis • Characteristics of vision alone cannot be used to reliably differentiate Amblyopia from other forms of visual loss. • The Crowding phenomenon is typical for Amblyopia but is not Patahogonomic. • Afferent pupillary defect (RAPD) rarely occurred in Amblyopia.

31. Diagnosis – V/A in Preverbal Children • Binocular fixation pattern is a test for estimating the relative level of vision in the tow eyes for children with strabismus who are under the age of about 3.

32. Diagnosis – V/A in 3-6 years old • A variety of optotypes can be used to directly measure acuity in children 3-6 years old.

33. Diagnosis – V/A in 3-6 years old • Often, however, only isolated letters can be used, which may lead to under estimated Amblyopia visual loss.

34. Diagnosis • Crowding bar or contour interaction bars, may help alleviate this problem. • Bar surrounding the optotype mimic the full of optotype to the amblyopia child.

35. Prevention / Screening

36. Prevention / Screening • Nearly all Amblyopic Visual loss is Preventable or Reversible with timely detection and appropriate intervention. • Children with Amblyopia or at risk for Amblyopia should be identified at a young age when the prognosis for successful treatment is best. • Role of Screening is important.

37. Prevention / Screening • In recent years, Amblyopia has become a topic of great interest in public health policy and discussions, beyond the domain of the treating ophthalmologist’s office.

38. Prevention / Early Treatment Overall affects 2-4% of population Awareness of problem

39. Prevention / ScreeningBirth First examination by primary care doctor before newborn leaves hospital. Look for clear, equal Red Reflex Congenital Cataract Hereditary Corneal Dystrophies Ocular alignment unreliable in first week of life.

40. Prevention / ScreeningBirth to 2 Years Examination at each well baby check Red reflex Ocular alignment should be orthophoric by 3-6 months Visual Acuity - Fix and Follow smoothly by 6 months

41. Prevention / Screening3, 4, 5 Year Checks Red reflex Ocular alignment - should be perfect Visual Acuity - Allen figures or similar External, anterior segment Ophthalmoscopic exam

42. Treatment

43. Treatment • Treatment of amblyopiainvolves the following steps: • Eliminating (if possible) any obstacle to vision such as a Cataract. • Correcting Refractive error. • Forcing use of the poorer eye by limiting use of the better eye.

44. Cataract Removal • Cataracts capable of producing Amblyopia require surgery without unnecessary delay. • Removal of significant congenital lens opacities during the first 2-3 months of life is necessary for optimal recovery of vision.

45. Cataract removal • In symmetrical bilateral cases, the interval between operations on the first and second eyes should be no more than 1-2 weeks. • Acutely developing severe traumatic cataracts in children younger than 6 years should be removed within a few weeks of injury, if possible. • Significant cataracts with uncertain time of onset also deserve prompt and aggressive treatment during childhood.

46. Refractive correction • In generally, optical prescription for amblyopic eyes should correct the full refractive error as determined with Cyclopagia. • Both Anisometropic and Ametropic Amblyopia may improve considerably with Refractive correction alone over several months.

47. Occlusion and Optical Degradation

48. Full Time Occlusion of the Sound Eye • Defined as occlusion during all waking hours. • It is the most powerful means of treating Amblyopia by enforced use of the defective eye.

49. Full Time Occlusion of the Sound Eye • If skin irritation, inadequate adhesion, or poor compliance proves to be a significant problem, Spectacle-mounted occluder or special opaque contact lenses can be used as an alternative to full-time patching.

50. Full Time Occlusion of the Sound Eye • Full time patching runs a small risk of perturbing Binocularity. • Full time patching should generally be used only when constant Strabismus eliminates any possibility of useful Binocular vision. • The child whose eyes are straight should be given some opportunity to see Binocularly.