On the regional variability of averaged cell area estimates for the human corneal endothelium in relation to the extent of polymegethism

Abstract

Purpose To assess variability in the coefficient of variation (COV) in cell area estimates when using different numbers of cells for endothelial morphometry. Methods Using non-contact specular microscopy images of the corneal endothelium, 4 sets of 20 cases were selected that included 200 cells and had overall (global) COV values of less than 30 (group 1), 31-40 (group 2), 41-50 (group 3) and over 50% (group 4). Subjects could be normal, or had ophthalmic disease (such as diabetes), a history of rigid or soft contact lens wear or were assessed after cataract surgery. A stepwise analysis was undertaken, 20 cells at a time, of the variability in cell area estimates when using different numbers of cells for the calculations. Results Variability in the average cell area values was higher if only 20-60 cells were used in the calculations and then tended to decrease. The standard deviation values on these average cell area values and the calculated COV showed the same overall trends and were more than twice as large for endothelia with marked polymegethism. Using more than 100 cells/ image in markedly polymegethous endothelia only increased the variability in the calculations.Conclusions These analyses indicate that substantial region variability in cell area values can be expected in polymegethous endothelia. The analysis further confirm that using only small numbers of cells (e.g. less than 50/image) in such cases is likely to yield far less reliable estimates of COV.

Corneal endothelial cell loss after trabeculectomy and phacoemulsification in one or two steps: a prospective study

“…Neither in this study nor in our previous study [14] have we found significant COV increases after surgery, in accordance with the results of other authors [10,11]. Thus, the COV is not a very good indicator of corneal endothelial cell loss and this has been also suggested by other authors [31,32].…”

“…The baseline COV were similar in the one-step and two-step groups, also similar to those found in our previous study [ 14 ] and did not decrease significantly after phacotrabeculectomy. Most studies have documented COV between 30 and 40%, but also values of up to 60% [ 3 , 10 , 14 , 31 ], and increasing values when there is endothelial loss [ 10 , 11 , 14 , 18 , 32 ]. Neither in this study nor in our previous study [ 14 ] have we found significant COV increases after surgery, in accordance with the results of other authors [ 10 , 11 ].…”

“…Other authors use non-contact or contact specular microscopy and also automatic cell counting, while we use Confoscan 4™ confocal microscopy and semiautomatic cell counting in four images and we think that our method is more accurate and better reflects cell loss. Automatic endothelial cell counting may overestimate cell density, especially with lower cell densities [40,41] because the numbers of cells included in the analysis decrease and influence the results [32,[42][43][44].…”

Evaluation of the common pauraque (Nyctidromus albicollis) cornea using light and scanning electron microscopy

“…Endothelial efficiency can be evaluated from values such as mean cell area, cell density, CV and percentage of hexagonal cells. In such manner, it is possible to evaluate endothelial pleomorphism and polymegathism as a marker of past or present endothelial damage or disease (Doughty, 2006(Doughty, , 2018Doughty & Oblak, 2008). Different methods are used, such as specular microscopy, confocal microscopy and SEM.…”

“…Different methods are used, such as specular microscopy, confocal microscopy and SEM. The latter not only provides information on cell morphology, but is high enough to evaluate the three-dimensional cell organization and the ultrastructure of endothelial cells (Coyo et al, 2019;Doughty, 1989Doughty, , 2018Meek & Fullwood, 2001;Tamayo-Arango et al, 2009). The downside is that significant cellular contraction occurs with processing by dehydration with glutaraldehyde.…”