Measurement of consensual accommodation in vision-impaired eyes.

PURPOSE

To measure the accommodative response in unsighted or profoundly vision impaired (PVI) eyes when accommodation is elicited in the fellow, sighted eye.

METHODS

Eighty-eight unilaterally PVI subjects (UPS) and 97 bilaterally sighted subjects (BSS) (10 to 45 years) were enrolled. Subjects had clear ocular media for auto-refraction and could steadily fixate targets with the sighted eye. For BSS, a long-pass filter was placed in front of one eye to simulate unilateral blindness. Both eyes were measured with a Shin-Nippon auto-refractor while fixating a 4/40 letter at 4 m and then an N8 letter at 40 cm and at 33 cm. Accommodation was calculated as the difference between distance and near refraction.

RESULTS

Only subjects with repeatable alignment between measurements were included in the analyses (64 UPS, 95 BSS). Results were analyzed using t test and a generalized linear mixed model including age, sightedness, distance spherical equivalent, and accommodation as factors. The t test found no significant difference between eyes for UPS (p = 0.981 at 40 cm and p = 0.663 at 33 cm). For BSS, the sighting eye produced statistically significant but only slightly greater amounts of accommodation than the filtered eye (0.098 diopters [D], p = 0.002 at 40 cm and 0.189 D, p < 0.001 at 33 cm). The generalized linear mixed model found no difference between BSS and UPS in terms of difference in accommodation between eyes (p = 0.128 at 40 cm and p = 0.157 at 33 cm).

CONCLUSIONS

The PVI eyes of unilaterally PVI individuals display similar accommodative response to their fellow, sighted eyes when accommodation is elicited by near target of up to 3 D to the fellow eye. However, the difference in accommodative response between PVI and fellow, sighted eye is related to the amount of accommodation elicited.