Detailed mapping of the normal posterior pole retinal thickness by the scanning retinal thickness analyzer
Purpose: We have previously reported on the measurement of the retinal thickness at selected locations in the posterior pole with the aid of our method, the Retinal Thickness Analyzer (RTA). However, there is a clinical need to assess the area as well as the location of changes (thickening in macular edema and atrophy in glaucoma). We have thus developed our method further into a scanning RTA capable of generating detailed retinal thickness maps. The scanning RTA was applied to a pilot group of healthy subjects to define the normal map and its variations. Methods: A laser slit is projected on the retina and scanned, in 400 msec, across 10 locations on the fundus. The scan is performed in 9 areas to cover the posterior pole. The image of the laser slit intersection with the two retinal boundaries is digitally recorded and analyzed by an operator-free algorithm to generate a map of the retinal thickness. A commercial prototype (Talia - OcuMetrics) was used to examine 20 healthy volunteers aged 19 to 54 years (10 females and 10 males, 10 African Americans and 10 Caucasians). The retinal thickness was measured at the central posterior pole. Results: The retinal thickness was 195μm at the fovea, 355μm between the fovea and the disk and varied in correspondence with the known anatomy. Age, gender or race did not affect the retinal thickness. The standard deviation of the thickness at each of 1710 points was, on average, ±29μm. This variability did not change significantly with location. Conclusion: The correspondence of the detailed map with the anatomy further validates the method. The lack of large variations with age, gender or race is in agreement with previous data. The fact that the 95% confidence interval for the normal retinal thickness is less than 60μm indicates that subtle pathological changes in retinal thickness can be detected by scanning RTA. Early and sensitive detection can be applied, for example, to the diagnosis and management of diabetic macular edema and glaucoma.
Zou, S; Asrani, S; D'Anna, S; Zeimer, R
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