Optic nerve hypoplasia and small eyes in presumed amblyopia

Purpose: To assess the anatomy of eyes presumed to be amblyopic and their f ellow eyes. Participants: Two hundred seventy-five patients diagnosed with amblyopia and 88 healthy or glaucomatous subjects. Methods:All subjects und erwent complete examinations, including cycloplegic refraction, slit lamp e xamination, ophthalmoscopy, and retinal imaging. Axial lengths were determi ned on 263 amblyopic and 88 healthy and glaucomatous subjects by ultrasonic biometry. Main outcome measures: Optic disc areas were determined by magni fication correction of disc images performed with formulas. Dysversion of t he optic disc was determined by simultaneous viewing of disc photographs, d igitized images of both eyes, or both. Results: The mean disc area of eyes presumed to be amblyopic was 1.72 mm(2) +/- 0.73 SD and 1.95 mm(2) +/- 0.69 SD for nonamblyopic eyes (P = .0017). The mean disc area for 176 optic dis cs of glaucomatous and healthy eyes was 2.61 mm(2) +/- 0.95 SD. The mean ax ial length for eyes in the general population is 23.65 mm +/- 1.35 SD. The healthy and glaucomatous group in this study had a mean axial length of 23. 89 mm +/- 1.29 SD. The eyes with poorer vision that were assumed to be ambl yopic averaged 22.42 mm +/- 2.01 SD in length, whereas their nonamblyopic f ellow eyes averaged 22.83 mm +/- 1.89 SD (P = .022). The differences betwee n eyes in the healthy population and eyes that are presumably amblyopic, as well as the healthy and fellow eyes, are highly significant (P < .0001)(7. 0 x 10(-16)). Conclusion: Vision impairment in presumed amblyopia is associ ated with optic nerve hypoplasia with relative microphthalmos, which is mor e notable in those eyes with poorer vision.