We’ve stated our case before that in many ways, a patient’s amblyopic eye may be considered as “learning disabled” relative to the non-amblyopia eye. This was bolstered in part by an article showing that in strabismic amblyopia, reading is impaired not only during monocular viewing with the amblyopic eye, but also with the nonamblyopic eye and binocularly. The impaired reading performance is associated with differences in both saccadic and fixational patterns, likely an adaptation to abnormal sensory experiences such as crowding and suppression. This has also been reported in acquired conditions termed “amblyopic dyslexia“, and is consistent with our newly developed visionhelp Amblyopia Project.
Over the weekend I had the chance to sit down with an attractive new case-based textbook edited by Traboulsi and Utz containing a nice chapter on amblyopia.
There are some particularly nice sound bites from the chapter, including the following:
- “Amblyopia is a neurodevelopmental disorder that occurs due to de-correlated binocular input to the visual cortex.”
(This squarely positions amblyopia more broadly as a neurodevelopmental problem worthy of deeper consideration than patching, atropinization or other approaches emphasizing monocular visual acuity as the main index of function. It also identifies it as a binocular vision problem.)
- “Although the first locus of dysfunction appears to occur in V1, abnormalities in the downstream extra-striate cortex have been shown by recent studies using neural recordings in animal models of amblyopia as well as psychophysical and functional MRI studies in humans. Involvement of striate as well as extra-striate visual cortex can explain the spectrum of visual functional abnormalities that involve both the afferent and efferent visual systems and visual perception in amblyopia.”
(This paves the way for appreciating amblyopia at a broader level, including the continuum of visual deficits from acuity [V1] to extra-striate areas directly impacting reading abilities even in the presence of adequate visual acuity.)
- “Dynamic retinoscopy should be completed to assess for hypo-accommodation, which may contribute to persistent amblyopia despite treatment.”
(There is a small but distinct chapter in the book dedicate to dynamic retinoscopy, and all I can say is Hallelujah! to the recognition of the importance of assessing and treating the accommodate system in amblyopia.)
- “Lastly, vision loss in a structurally abnormal eye (w.g. one with optic nerve coloboma, optic nerve hypoplasia, retinopathy of prematurity) should not be assumed to be caused only by the structural anomaly, as there may be an additional component of treatable amblyopia caused by anisometropia, strabismus, or occlusion. In such cases a trial of amblyopia therapy is indicated.”
(All too often amblyopia is dismissed as organic and the patient is never give the benefit of a trial period of vision therapy. Rather than differentiating amblyopia into treatable and non-treatable buckets, this is a reminder that there may be a functional component to organic amblyopia worth treating even if the underlying structural abnormality doesn’t change.)
Back to the emphasis on reading disorders, the chapter has a nice table reproduced from the Vision Screening Recommendations of the American Association for Pediatric Ophthalmology and Strabismus (AAPOS). Here is a nugget, published in 2014, that previously escaped me. Take a look at the very last item, and lo and behold there it is:
- Refer children not reading at grade level