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R. N. Frank, M. Mequio; The Mystery of Macular Edema. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2686.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies have shown a poor correlation between macular thickness, by optical coherence tomography (OCT), and visual acuity in diabetic macular edema. We wished to determine if this was true of other causes of macular edema, and, if so, what other factors might be adduced to explain this poor correlation.
We evaluated computerized OCT images of patients with macular edema resulting from diabetic retinopathy, uveitis, branch or central retinal vein occlusions, or pseudophakia obtained at the Kresge Eye Institute over the past 4 years. We compared best-corrected visual acuity (decimal or logMAR) with central zone or central point macular thickness, or macular volume, and in the presence or absence of cystoid changes. We also evaluated the effect of macular edema duration for pseudophakic macular edema or macular edema in retinal vein occlusions, conditions with acute onset such that duration can be more accurately determined.
Consistent with published results of the DRCR.net and our own earlier data (ARVO, 2007) we find a poor correlation between visual acuity and OCT-measured macular thickness in diabetic retinopathy, and also in macular edema following pseudophakia, retinal vein occlusions, and uveitis, with r-values for linear regression not greater than 0.55 and usually much less. The relationship was poor even when eyes with cystoid changes were evaluated separately from eyes with non-cystoid edema. In eyes with acute onset of macular edema, duration also had little effect.
The correlation between macular thickness and visual acuity in several entities producing macular edema is poor. Other possible modifying factors, such as cystoid changes and macular edema duration, contribute little to this effect. The mechanism(s) by which macular edema produces visual loss remain puzzling.
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