Glaucoma Affects Viewing Distance for Recognition of Sex and Facial Expression

To measure the distance for sex and facial expression recognition in patients with glaucoma.

Sixteen patients with open-angle glaucoma, 16 age-matched controls, and 12 young controls participated. During each trial, a face covering 0.36° × 0.5°, simulating the angular size of a face viewed at 20 m, was presented centrally. The angular size increased automatically by steps of 5 cm, simulating the face moving progressively closer. The participants were asked to stop the progression with a keypress, first, when they were able to recognize the sex, and second, when they were able to recognize the facial expression (angry, happy, neutral). We measured the threshold equivalent viewing distance to recognize the sex and the facial expression.

Participants with glaucoma, both those with and without reduced central acuity, required a shorter viewing distance (i.e., a larger face) than did controls to recognize both the sex (by 2.59 m, F1,30 = 8.7, P < 0.006) and the facial expression (by 3.64 m, F1,30 = 14, P < 0.001). No significant difference was found between younger and older controls.

Face perception is a skill that is reliant on central vision. Our behavioral results are consistent with the hypothesis of reduced central sensitivity in glaucoma. We suggest that the necessity to view larger faces in patients might result from a higher sensitivity to crowding that increases the difficulty to perceive the relevant features for recognition of both sex and facial expressions, akin to normal peripheral vision.