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Jianyan Huang, Jyotsna Maram, Cristina Modak, Srinivas R Sadda, Vikas Chopra, Olivia L Lee; Comparison of Non-contact Specular and Confocal Microscopy for the Evaluation of the Corneal Endothelium. Invest. Ophthalmol. Vis. Sci. 2014;55(13):999.
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To compare endothelial cell assessments obtained by non-contact specular and confocal microscopy using the Konan NSP-9900 and Nidek ConfoScan4 systems.
Sixty healthy eyes and 40 diseased eyes (15 eyes with Fuchs’ Endothelial Dystrophy and 26 with glaucoma) were examined with the Nidek ConfoScan4 confocal microscope and the Konan NP-9900 specular microscope. Certificated anterior segment graders at the Doheny image reading center compared the images from both instruments side by side for image quality assessment. Endothelial cell density (ECD) measurements were calculated with each instrument’s machine-generated automated (Konan Auto and Nidek Auto) and manual (Konan Center and Nidek Manual) methods, and compared to each other.
All normal and glaucomatous eyes had gradable images. However, in corneas with Fuchs’ Endothelial Dystrophy, poor image quality precluded ECD grading in 6.7% (1/15) and 46.7% (7/15) of the eyes, as obtained by confocal and specular microscopy respectively. ECD values were significantly higher in glaucomatous eyes compared to control eyes, irrespective of the counting method (Table 1). Regardless of whether the eye was normal or glaucomatous, ECD values obtained manually from either device were not statistically significantly different (P>0.05). In contrast, machine-generated ECD values were significantly different from manual results, measuring greater in all cases with specular microscopy,. Machine-generated ECD values from confocal microscopy also differed significantly from manual determinations, but not in a consistent direction. Table 1 ECD values obtained by 4 methods of either instrument. (Mean±SD cells/mm2) Konan Auto Konan Center Nidek Auto Nidek Manual Control 2865±272 2690±299 2552±231 2684±294 Glaucoma 2184±762 2013±736 2185±456 1998±736
Automatic machine-generated ECD measurements differed significantly from manual assessments, suggesting that the automated results should be used with caution. On the other hand, ECD values derived from the Konan Center method were comparable to Nidek’s Manual method in both normal and glaucomatous eyes, suggesting that, with manual grading, the two instruments can be used interchangeably for reliable ECD measurements. Because of a higher proportion of gradable images, confocal microscopy might be superior to specular microscopy for ECD measurements in Fuch’s corneal dystrophy.
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