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William Scott Tuten, Ramkumar Sabesan, Jennifer Holland, Austin Roorda, Jacque L Duncan; Using adaptive optics microperimetry to assess photoreceptor structure and function in healthy subjects and patients with retinal disease.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2626. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To develop and implement adaptive optics microperimetry to study the relationship between cone structure and function in normal eyes and patients with retinal disease.
A multi-wavelength adaptive optics scanning laser ophthalmoscope (AOSLO) was used to image the retina and probe cone function at targeted parafoveal locations in two patients with retinitis pigmentosa (RP; n = 4 eyes), one patient with dry age-related macular degeneration complicated by parafoveal geographic atrophy (AMD; n = 1 eye), and a group of four age-similar normals (n = 4 eyes). Real-time, image-based eye tracking enabled the delivery of a 550-nm test stimulus (diameter: 3 arcminutes = 14.5 μm) to targeted retinal loci between 0 and 4 degrees eccentricity along the temporal horizontal meridian. Increment thresholds were measured by presenting the test stimulus for 200 msec upon a 1.2° 550-nm background (luminance = 80 cd/m2), which ensured a cone-dominated response. At each test site, threshold was taken as the average of nine 4-2 dB staircases, and cone spacing was estimated from a histogram comprising all inter-cone distances identified within a sampling window of 50 μm.
For all subjects, increment thresholds increased roughly linearly with increasing eccentricity, although the slope of this elevation varied between individuals. For the two patients with early-stage RP, visual sensitivity and inter-cone spacing values were within normal limits for all tested sites. For the patient with AMD, areas with geographic atrophy were associated with absolute scotomas, while relatively normal-appearing regions between drusen yielded measurable thresholds. In normal subjects and patients with RP, the real-time eye tracking algorithm enabled precise stimulus delivery (SD: 0.42 arcmin = 2.0 μm on the retina), although its performance relied heavily on image quality.
AOSLO can be used to obtain robust and precise measures of parafoveal cone function in patients with retinal pathology. This approach sets the stage for establishing high-resolution structure-function correlations in patients with retinal disease, and may enhance our ability to assess the efficacy of novel treatments designed to inhibit photoreceptor degeneration.
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