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. 2005 Dec;89(12):1576-80.
doi: 10.1136/bjo.2005.077164.

Aniseikonia associated with epiretinal membranes

M Ugarte  1 , T H Williamson
Affiliations

Aniseikonia associated with epiretinal membranes

M Ugarte et al. Br J Ophthalmol. 2005 Dec.

Abstract

Aims: To determine whether the computerised version of the new aniseikonia test (NAT) is a valid, reliable method to measure aniseikonia and establish whether aniseikonia occurs in patients with epiretinal membranes (ERM) with preserved good visual acuity.

Methods: With a computerised version of the NAT, horizontal and vertical aniseikonia was measured in 16 individuals (mean 47 (SD 16.46) years) with no ocular history and 14 patients (mean 67.7 (14.36) years) with ERM. Test validity was evaluated by inducing aniseikonia with size lenses. Test reliability was assessed by the test-retest method.

Results: In normal individuals, the mean percentage (SD) aniseikonia was -0.24% (0.71) horizontal and 0% (0.59) vertical. Validity studies revealed mean (SD) 0.990 (0.005) horizontal and 0.991 (0.004) vertical correlation coefficients, 0.985 (0.111) horizontal and 0.989 (0.102) vertical slope. Repeatability coefficients were 1.04 horizontal and 0.88 vertical. Aniseikonia in patients with ERM ranged from 4% to 14%. Eight patients showed 2% or more size difference between horizontal and vertical meridians.

Conclusions: The aniseikonia test used in this study can be considered a simple, fast, valid and reliable method to measure the difference in image size perceived by each eye. Aniseikonia does occur in symptomatic patients with ERM. The effect of ERM on image size is heterogeneous across the retinal area affected.

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Figures

Figure 1
Figure 1
Horizontal (A) and vertical (B) aniseikonia measured in 16 normal subjects after inducing changes in the green semicircle size (magnification (m): −9%, −7%, −5%, −3%, 3%, 5%, 7%, and 9%) with size lenses. The straight line represents the ideal test, 1 correlation coefficient, 1 slope and Y-axis intercept at 0.
Figure 2
Figure 2
Horizontal and vertical aniseikonia (%) measured in 14 patients with unilateral macular ERMs. In 11 patients the image perceived by the affected eye was larger than in the fellow eye (macropsia) and in the remaining three, the eye with the ERM detected images as smaller (micropsia). Eight patients demonstrated 2% or more difference in image size between horizontal and vertical meridia.
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