Nonarteritic anterior ischemic optic neuropathy: refractive error and its relationship to cup/disc ratio.
OBJECTIVE
To investigate refractive error in eyes with nonarteritic anterior ischemic optic neuropathy (NA-AION) and its relationship to cup/disc (C/D) ratio.


METHODS
Cohort study.


METHODS
A total of 608 consecutive patients with NA-AION.


METHODS
At first visit, all patients had a comprehensive ophthalmic evaluation, including recording best-corrected visual acuity, visual fields, anterior segment examination, ophthalmoscopy, and fluorescein fundus angiography. Morphometric measurement of C/D ratio was performed in 65 fellow normal eyes in patients with unilateral NA-AION. Refraction was converted into spherical equivalent for data analysis. The data were analyzed using Pearson correlation, Mantel-Haenszel chi-square test, Cochran-Mantel-Haenszel test, chi-square goodness-of-fit test, and segmented linear regression.


METHODS
Refractive error in NA-AION eyes and any association between refractive error and C/D ratio.


RESULTS
Mean age of patients with NA-AION was 60.9 (standard deviation [SD] = 12.6; range 20.5-95.2) years. Median time from onset to refraction was 2 weeks (interquartile range 1-5 weeks). There was a significant association between spherical equivalent and age (P<0.0001). Comparison of refraction in patients with NA-AION who were aged >or=50 years with that of an age-matched general population in the Framingham study cohort showed no significant difference between the 2 groups (P = 0.289). Comparison with the age-matched US population from the 1999-2000 National Health and Nutrition Examination Survey showed a higher proportion of NA-AION eyes with spherical equivalent from -0.5 to 0.5 diopters and a smaller proportion with -3 to <-0.5 and >0.5 to +3 diopters (P<0.001). For horizontal C/D ratio, a higher degree of myopia and higher degree of hyperopia were significantly associated with a larger C/D ratio (P<0.021). A similar pattern was seen for vertical C/D ratio in hyperopia (P = 0.057) but not in myopia (P = 0.428).


CONCLUSIONS
There was a significant association between spherical equivalent refraction and age (P<0.0001). C/D ratio in persons with NA-AION is significantly smaller than that seen in the general population. Morphometric study in patients with NA-AION showed that a higher degree of myopia and higher degree of hyperopia are significantly associated with a larger C/D ratio.


BACKGROUND
The authors have no proprietary or commercial interest in any materials discussed in this article.
Hayreh
Sohan Singh
SS
Department of Ophthalmology and Visual Sciences, College of Medicine, University of Iowa, Iowa City, Iowa, USA. sohan-hayreh@uiowa.edu
Zimmerman
M Bridget
MB
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001167:Arteritis / Q000503:physiopathology; D015331:Cohort Studies; D005260:Female; D005451:Fluorescein Angiography; D006801:Humans; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000473:pathology*; D018917:Optic Neuropathy, Ischemic / Q000175:diagnosis / Q000503:physiopathology*; D011446:Prospective Studies; D012030:Refractive Errors / Q000175:diagnosis / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology