VF diameter was correlated significantly with logMAR visual acuity ( r = −0.84, P < 0.05), consistent with previous research, 8 but there was no significant correlation between VF diameter and Pelli-Robson letter contrast sensitivity ( r = 0.19, P = 0.63). The characteristics given in the Table are for the tested eye, which was selected at random, but the fellow eye had similar characteristics. The Table gives the patients' ages, inheritance patterns, logarithm of the minimum angle of resolution (logMAR) visual acuities, Pelli-Robson letter contrast sensitivities, and horizontal diameters of the visual field (VF) obtained with a Goldmann II/4e target. No patient had an atrophic-appearing macular lesion or more than a minimal cataract in the tested eye, based on clinical examination. Ten patients with RP (three males and seven females, aged 10–54 years) participated in the study. The results suggest that CS measurement in both the presence and absence of luminance noise can provide important information about visual dysfunction in RP patients. Low CS was associated with elevated intrinsic noise in this group of RP patients, but even patients with normal CS had elevated noise levels. Log CS 0 for the patients was correlated significantly with log N eq ( r = −0.80, P < 0.05), but not with log efficiency ( r = 0.54, P = 0.11). In comparison, only two patients had lower-than-normal sampling efficiency, and these two patients also had below-normal CS 0. All 10 patients had abnormally high N eq, including two patients with normal CS 0. Data were fit with a standard linear amplifier model, which provided estimates of N eq and sampling efficiency.ĬS 0 for the patients ranged from normal to as much as a factor of 3 below the lower limit of normal. DARK NOISE SAMPLERS PATCHCS was measured for 2-cycles-per-degree Gabor patch targets presented in the absence of noise ( CS 0) and in five levels of noise spectral density. Participants included 10 patients with RP aged 10 to 54 years, who had visual acuities of 20/40 or better, and 10 visually normal control subjects aged 22 to 65 years. To determine the relationships among equivalent intrinsic noise ( N eq), sampling efficiency, and contrast sensitivity (CS) in patients with retinitis pigmentosa (RP), where N eq is an estimate of the amount of noise within the visual pathway and sampling efficiency represents the subject's ability to use stimulus information optimally.
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