Scotoma Simulation in Healthy Subjects

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Abstract

SIGNIFICANCE

This article shows a successful concept for simulating central scotoma, which is associated with age-related macular degeneration (AMD), in healthy subjects by an induced dark spot at the retina using occlusive contact lenses. The new concept includes a control mechanism to adjust the scotoma size through controlling pupil size without medication. Therefore, a miniaturized full-field adaptation device was used.

PURPOSE

The aim of this study was to design a novel concept to simulate AMD scotoma in healthy subjects using occlusive contact lenses.

METHODS

To define an optimal set of lens parameters, we constructed an optical model and considered both the anatomical pupil diameter and the opaque central zone diameter of the contact lens. To adjust the scotoma size, we built a miniaturized full-field adaptation device. We demonstrate the validity of this novel concept by functional measurements of visual fields using automated threshold perimetry. Finally, we conducted a perception study including two tasks, consisting of pictograms and letters. The stimuli were presented at different eccentricities and magnifications.

RESULTS

The visual fields of all 10 volunteers exhibited absolute scotomas. The loss of contrast sensitivity ranged within 27 and 36 dB (P < .05), and the scotoma localizations were nearly centered to the macula (mean variation, 2.0 ± 4.8° horizontally; 3.5 ± 4.7° vertically). The eccentric perception of letters showed the largest numbers of correctly identified stimuli. The perception of pictograms showed significantly reduced numbers (P < .0001) and revealed a dependency on magnification. The results suggest that best perception is possible for magnified stimuli near the scotoma.

Conclusions

We demonstrated that the creation of an absolute simulated AMD scotoma is possible using occlusive contact lenses combined with a miniaturized full-field adaptation device.

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