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D.C. Le, J.M. Enoch, D. Schwartz; Visual Responses Elicited Upon the Nasal Optic Nerve Head in a Sub-Set of High Myopes . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2776.
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Purpose and Background: This laboratory has studied traction effects affecting photoreceptor alignments in retinas of myopic observers. Induced traction was associated with the optic nerve head, and greatest effects were noted nasal to optic discs. Existing pathological literature suggests the presence of a super-traction zone associated with the nasal optic nerve head in about 37% of affected myopes (Grosniklaus & Green, in The Retina, 12:127-133, 1992), i.e., the retina and choroid in a meaningful proportion of these patients literally over-rides the nasal optic nerve head. Can vision be elicited in these over-ride zones? Method: Static perimetric techniques were used, and 12 myopes were tested in each eye. Goldmann I size targets, and 10 asb background luminance were used. Observers with staphylomas were not included, V.A. was 20/25 or better in each eye, fixation was good, no ocular disorders were noted other than myopia-related anomalies. Refractive errors ranged from -1.25 D to -14.00 D. A Canon Fundus Camera Perimeter Model CPP-1 was used. Results: 37% of eyes tested with myopia over -5 D, i.e., 6 eyes in 3 subjects revealed on-disc visual responses (assume in nasal over-ride zones). These myopes had errors of -6.00 to -8.00 D. These were not stray light effects; detailed observer responses were elicited. Testing was ca 1.5° outside of, and within the nasal optic nerve boundary, and 1.5° outside of the myopic crescents on the temporal retina. No response to Goldmann I, 1000 asb, was elicited on the temporal optic nerve, nor within temporal crescents. Responses elicited within the nasal over-ride zone were 1.0-1.8 log units (full measured range) less sensitive than retinal loci 1.5° outside of the nasal discs. A minimum of 8 loci were sampled in each eye. Evidence of rather prompt light adaptation existed in the over-ride zones of positive responders. On affected individuals, we are pursuing added data on eye-lengths, retinal/disc contour, blood supply, receptor orientations, etc. Conclusions: In a proportion of higher myopes which exhibit nasal retinal and choroidal over-ride traction zones, visual responses with high thresholds can be elicited upon the optic nerve head. Support: This research has been supported in part by Grants from the New Del Amo Research Program, an NEI Training Grant, and the Branna and Irv Sisenwein Fund. No Conflict.
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