Morphometry of Corneal Endothelium in Patients with Corneal Guttata

Assessment of the reliability of endothelial cell-density estimates in the presence of pseudoguttata

“…Examples can be found where some cells included in morphometric analyses (e.g., as marked using a centre-dot analysis program) are clearly touching the guttata edges [21]. The same applies to application of an alternative 'automated contour' method [28], although the use of this type of software technique (also perhaps known as a 'polygonal' method) can be done such that cells in close contact with guttata are not included [4]. Such a selective approach appears to be very similar to that also used in assessing eye bank corneal endothelia where the 'contour' only included groups of cells with clearly resolved cell borders [5].…”

“…The current studies reveal a similar dichotomy in that some endothelia with grade 3 pseudoguttata have a rather lower ECD than age-matched controls while the others have similar or even higher apparent ECD values; the overall mean ECD may however not be different compared to age-matched controls without endothelial abnormalities. Beyond these studies, most other reports indicate that the ECD may only be slightly lower than age-matched controls or that no statistically significant difference could be detected [12,15,17,[24][25][26][27][28]. A confounding variable that can substantially affect ECD in guttata cases is whether the patients had had intraocular surgery (e.g., for cataracts) [15,28,31], and this aspect of patient history is not clearly identified in some reports.…”

“…The methodology used to generate ECD estimates in these various reports is however far from clear, and there appear to be few agreed guidelines on how the morphometry of such endothelia could or should be undertaken. As a result, the studies appear to show poor agreement with some studies reporting no statistically significant difference between normal and guttata-affected endothelia [12,15,17,[24][25][26][27][28] and others finding notable differences [16,19,21,22]. A key feature of endothelia with guttata or pseudoguttata is that only part of a cell may be evident in the immediate vicinity of the darkened regions.…”

“…True corneal guttata would generally be considered as being associated with a progressive endothelial dystrophy (e.g., Fuch's), while pseudoguttata can have similar appearances but be due to other reasons and have no obvious familial link [10][11][12][13][14]. Regardless of the reliability of being able to define the cause of endothelial guttate changes, there have been a variety of studies of the endothelial cell density in corneas affected with guttata or pseudoguttata [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. The methodology used to generate ECD estimates in these various reports is however far from clear, and there appear to be few agreed guidelines on how the morphometry of such endothelia could or should be undertaken.…”

Assessment of a variable frame (polygonal) method to estimate corneal endothelial cell counts after corneal transplantation

“…2 A variable frame method offers a slightly different approach in that a set of cells is outlined (as opposed to individual cells) on the original on-screen image, and then the number of cells within that outline (the variable frame) is counted. [18][19][20] With the area of the variable frame defined by the software and the number of cells counted, a calculation is then made to obtain the ECD in cells/mm 2 . By removing the step of needing to manually define each individual cell domain on an endothelial image, a variable frame software method may provide a good compromise between a time-consuming planimetry and unreliable results from either automated software or a fixed-frame manual cell count.…”