Rod Sensitivity in Age-related Macular Degeneration (AMD) and Retinitis Pigmentosa (RP)
Rod Sensitivity in Age-related Macular Degeneration (AMD) and Retinitis Pigmentosa (RP)
A new fundus-guided microperimeter (MP-3S) has been developed by Nidek, Inc. to track the fundus of the patient and present stimuli in specific anatomically-defined locations. Furthermore, this tracking means that exactly the same locations can be tested on subsequent (follow-up) visits. The investigators will use a method called two-color perimetry to map rod and cone sensitivity on this device. With this technique, the sensitivity difference (blue-red) to chromatic test stimuli can be used to determine whether rods, cones or both photoreceptor systems mediate the threshold at a given location in the macula.
Despite recent advances in understanding the pathogenesis of retinitis pigmentosa (RP) and age-related macular degeneration (AMD), precise characterization of the disease phenotype remains elusive. In both diseases, much of the focus has necessarily been on the loss of cone function, since visual fields, acuity and contrast sensitivity are typically measured under photopic conditions. In RP, we need a greater understanding of patterns of rod loss since most disease-causing mutations affect primarily rods. In AMD, recent findings have shown that scotopic sensitivity can be much more affected than conventional photopic measurements such as visual acuity. For patients, however, it is difficult to maintain stable fixation, especially when central vision is compromised. A new fundus-guided microperimeter, the MP-3S, has been developed by Nidek, Inc. to circumvent this problem. The investigators will evaluate the value of this device for following rod and cone loss in patients with either RP or AMD.
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