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F. Miani, M. Salvetat, L. Parisi, M. Felletti, M. Zeppieri, P. Brusini; Comparison Between Laser-Scanning-in-vivo-Confocal-Microscopy and Noncontact Specular Microscopy in Assessing Corneal Endothelial Cell Density and Central Corneal Thickness. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5083.
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To compare endothelial cell density (ECD) and central corneal thickness (CCT) measurements assessed with the laser-scanning-in-vivo-confocal-microscope HRT II corneal module and noncontact specular microscopy. Intrasession intra-observer and inter-observer agreement of the two instruments in a cohort of normal subjects were also determined.
This prospective observational cross-sectional study included 48 healthy subjects (mean age of 50.9±13.7 years, range 28-82). All subjects underwent ECD and CCT measurement with the laser-scanning-in-vivo-confocal-microscope HRT II corneal module (HRT-CM) and a noncontact-specular-microscope (NCSM) (Tomey EM-3000). The measurements were repeated 3 times with each device by two independent observers during the same session. The differences between the CCT and ECD values recorded by the two instruments were calculated using the paired t-test. The agreement between devices was evaluated using the Bland-Altman method. Intra- and inter-observer agreement for both instruments were assessed using the intraclass correlation coefficient (ICC).
The mean CCT measurements with NCSM and HRT-CM were respectively 538.2±30 µm and 540.8±44 µm (p=.15); the mean ECD measurements were 2564.6±178 cells/mm2 and 2667.4±378 cells/mm2 (p=.28). The mean of the differences (HRT-CM minus NCSM) were respectively 12.6±18 µm for CCT and 102.7±207 cells/mm2 for EDC. The differences significantly increased with increasing CCT and ECD (p<.001). The ICC for intra-observer agreement ranged from .96 to .99 for NCSM, and from .85 to .94 for the laser-scanning-in-vivo-confocal-microscopy. The ICC for inter-observer agreement ranged between .94 and .99 for the noncontact-specular-microscope, and between .91 and .98 for HRT-CM.
HRT-CM and NCSM showed an overall good inter-method agreement. HRT-CM tended to slightly overestimate both CCT and ECD, which increased with CCT and ECD. Both instruments showed an excellent intra- and inter-observer agreement that appeared to be better for NCSM.
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