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Jean-Francois Dinon, Muriel Boucart; Effect of contrast on face perception: Application to ophthalmology (AMD patients). Journal of Vision 2005;5(8):985. doi: 10.1167/5.8.985.
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Title: Effect of contrast on face perception: application to ophthalmology (AMD patients).
Authors: JF Dinon & M Boucart
Address: CHRU Lille, Hôpital Roger Salengro, service EFV, Lab. Neurosciences fonctionnelles & pathologies, 59037 Lille, France.
Objective: Age related Macular Degeneration (AMD) is a major cause of blindness in people over 50 years. AMD patients display difficulties in reading and recognizing faces. Our Study is designed to understand the effect of loss in contrast sensitivity and high spatial frequencies on face recognition in patients with AMD and healthy observers.
Method: Healthy subjects were tested in three tasks requiring different types of processing: (1) discrimination face/non-face, (2) discrimination of gender and (3) discrimination of known/unknown faces. The contrast of gray-level photographs of faces was manipulated in order to simulate the loss in contrast sensitivity of AMD patients. From each original photograph the contrast was divided by 2, 4, 8, 16, and 32 for healthy participants and divided by 2, 4, 8 and enhanced (2, 4, 8) for patients.
Results: For healthy subjects the results show that: (1) the decrease in contrast does not affect the face/non-face discrimination task, (2) gender discrimination requires 9% of the original contrast and face recognition requires at least 16% of the original contrast. For patients performance increases when the contrast is multiplied at least by two..
Conclusions: Our results indicate that difficulties in face recognition in patients with AMD are to a large part due to their loss in contrast sensitivity and its consequences on the perception of high spatial frequencies.
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