BACKGROUND: Retinally induced aniseikonia is presumably the result of monocular/asymmetric displacement of the photoreceptors causing an image size difference between the two eyes. Treatment for anisometropic aniseikonia involves altering spectacle lens parameters for an overall magnification/minification effect, however retinally induced aniseikonia presents additional challenges.
CASE REPORT: AM, a 72-year old Caucasian male, was evaluated for aniseikonia following a vitrectomy, epiretinal membrane peel, and cataract extraction in the left eye. After surgery, he complained of binocular diplopia and a vertically elongated image in his left eye. Best corrected visual acuity was 20/25 OD and 20/30 OS at distance through +1.50-1.25x089 and -0.75-0.75x146 with a +2.50 add. Cover test findings revealed convergence insufficiency and a left hyperphoria with inadequate compensatory fusional vergence. The Aniseikonia Inspector revealed Horizontal: -1%, Vertical: 6%, Diagonal @ 45°: -2%, and Diagonal @ 135°: 6%. Optical solutions were explored to try to decrease the meridional aniseikonia. Relieving BI and BD prism alleviated asthenopia; however AM still reported a vertically elongated image in his left eye. Size lenses provided an overall size change but could not change the vertical elongation. An over-correcting against-the-rule astigmatic spectacle lens was able to alter the aniseikonia, but AM could not tolerate the blur. An over-correcting astigmatic spectacle and neutralizing toric contact lens system was prescribed; however he was unable to adapt to contact lens wear. AM inquired about an anamorphic lens, much like the one used in cinematography, to stretch full screen into widescreen format. A bitoric spectacle lens was designed using the Aniseikonia Inspector that was able to achieve this effect, decreasing AM's meridional aniseikonia to a more tolerable level.
CONCLUSION: This case report highlights the many options for changing lens parameters to affect image magnification/minification; however, significant heterogeneity in retinally induced aniseikonia presents a unique challenge to conventional iseikonic lenses options.