Doughty Michael J
Department of Vision Sciences, Glasgow-Caledonian University, Glasgow, Scotland.
Cornea. 2017 Aug;36(8):973-979. doi: 10.1097/ICO.0000000000001218.
To assess variability in endothelial cell density (ECD) estimates when polymegethism (variance in cell areas) is present.
Using noncontact specular microscope images of the corneal endothelium, 4 sets of 20 cases were selected, which included 200 cells and had coefficient of variation values of less than 30% (group 1), 31%-40% (group 2), 41%-50% (group 3), and over 50% (group 4). A stepwise analysis was undertaken, 20 cells at a time, of the ECD estimates when using different numbers of cells for the calculations.
The net differences in ECD estimates when comparing sets of 20 cells with 200 cells were 5.0% ± 3.9%, 8.1% ± 7.3%, 11.3% ± 9.4%, and 14.5% ± 12.4% for groups 1 to 4, respectively. For measures on 100 cells per image, the predicted variances in ECD values were 5.6%, 8.8%, 11.1%, and 13.7% for the 4 groups.
Higher values of corneal endothelial polymegethism result in predictable increases in the variability (uncertainty) in ECD estimates, thus reducing the "accuracy" of ECD values. There is no obvious utility in assessing more than 100 cells in such endothelia.
评估存在多形性（细胞面积方差）时内皮细胞密度（ECD）估计值的变异性。
使用角膜内皮的非接触式镜面显微镜图像，选取4组，每组20例，共200个细胞，变异系数值分别小于30%（第1组）、31%-40%（第2组）、41%-50%（第3组）和超过50%（第4组）。在计算时，每次逐步分析使用不同数量细胞时的ECD估计值，每次分析20个细胞。
第1至4组中，将20个细胞组与200个细胞组的ECD估计值进行比较时，净差异分别为5.0%±3.9%、8.1%±7.3%、11.3%±9.4%和14.5%±12.4%。对于每张图像100个细胞的测量，4组ECD值的预测方差分别为5.6%、8.8%、11.1%和13.7%。
角膜内皮多形性值越高，ECD估计值的变异性（不确定性）会出现可预测的增加，从而降低ECD值的“准确性”。对于此类内皮细胞，评估超过100个细胞并无明显益处。
