A comparison of two methods for estimating polymegethism in cell areas of the human corneal endothelium

Doughty, Michael J.; Oblak, Emil

doi:10.1111/j.1475-1313.2007.00533.x

Cited by 13 publications

(12 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Low attention on correcting the corners provides a significantly larger random error in the estimates of polymegethism and pleomorphism than the estimate of cell density. This confirms recent similar findings (Oblak et al 2002;Sheng et al 2007;Doughty 2008;Doughty & Aakre 2008;Doughty & Oblak 2008).…”

Section: Standard For Calibration Of Csm Measurementssupporting

confidence: 82%

“…A common model for analysing the random error in endothelial morphometry is to divide the random error into inter-system variation, inter-operator variation and measurement error. Inter-system variation, which involves inter-operator variation, has been analysed in several recent studies (Deb-Joardar et al 2007a,b;Hirneiss et al 2007;Doughty & Oblak 2008). Such estimates, unfortunately, are limited to repeated measurements by a number of operators on the same defined clinical material and therefore are limited to that specific clinical material.…”

Section: Standard For Calibration Of Csm Measurementsmentioning

confidence: 99%

See 1 more Smart Citation

Simulation of specular microscopy images of corneal endothelium, a tool for control of measurement errors

Bucht

Söderberg

Manneberg

2011

Acta Ophthalmologica

View full text Add to dashboard Cite

Purpose:We aimed at developing simulation software capable of producing images of corneal endothelium close to identical to images captured by clinical specular microscopy with defined morphometrical characteristics. It was further planned to demonstrate the usefulness of the simulator by analysing measurement errors associated with a trained operator using a commercially available semi-automatic algorithm for analysis of simulated images.Methods: Software was developed that allows creation of unique images of the corneal endothelium expressing morphology close to identical with that seen in images of corneal specular microscopy. Several hundred unique images of the corneal endothelium were generated with randomization, spanning a physiological range of endothelial cell density. As an example of the usefulness of the simulator for analysis of measurement errors in corneal specular microscopy, a total of 12 of all the images generated were randomly selected such that the endothelial cell density expressed was evenly distributed over the physiological range of endothelial cell density. The images were transferred to a personal computer. The imagenet-640 software was used to analyse endothelial cell size variation, percentage of hexagonal endothelial cells, and endothelial cell density. Results:The simulator developed allows randomized generation of corneal specular microscopy images with a preset expected average and variation of cell structure. Calculated morphometric information of each cell is stored in the simulator. The image quality can secondarily be varied with a toolbox of filters to approximate a large spectrum of clinically captured images. As an example of the use of the simulator, measurement errors associated with one trained operator using the imagenet-640 software, and focusing on endothelial cell density, were examined. The functional dependence between morphometric information estimated with the imagenet-640 software algorithm and real morphometric information as provided by the simulator was analysed with regression. It was demonstrated that that the estimations of endothelial cell size variation was associated with a scaling error and that the random error was strongly dependent on the operator. Conclusion:The newly developed simulator for randomized generation of morphometrically defined corneal specular microscopy images for the first time makes it possible to estimate a spatial scaling error of an available semi-automatic algorithm and to determine the random measurement error of important morphometric estimates in a defined reference sample of images. It is anticipated that the simulator will be a valuable tool for the generation of a large set of morphometrically well-characterized corneal specular microscopy images that can be used for calibration among research centres, for minimization of random errors and for measurement of quality control. Simulated images will be useful for the development of fully automatic analysis of corneal endothelial cell morphometry.

show abstract

Section: Standard For Calibration Of Csm Measurementssupporting

confidence: 82%

Section: Standard For Calibration Of Csm Measurementsmentioning

confidence: 99%

Simulation of specular microscopy images of corneal endothelium, a tool for control of measurement errors

Bucht

Söderberg

Manneberg

2011

Acta Ophthalmologica

View full text Add to dashboard Cite

show abstract

“…[13][14][15] Various semi-automated and automated methods are available on specular and confocal microscopes that are routinely used to assess ECD. 11,16,17 In vivo confocal microscopy (IVCM) provides highly magnified images of corneal layers, including the corneal endothelium, 11,[18][19][20][21] even from corneas with advanced Fuchs' dystrophy before grafting 19 or from previously failed grafts with partial opacities. 10 One of the endothelial morphometry programmes available with one confocal microscope (Confoscan CS4, Nidek Technologies, Albignasego, Italy) is the Nidek Advanced Vision Information System software (NAVIS).…”

Section: Introductionmentioning

confidence: 99%

In vivo confocal microscopy of the corneal endothelium: comparison of three morphometry methods after corneal transplantation

Jonuscheit

Doughty

Ramaesh

2011

Eye

View full text Add to dashboard Cite

Purpose The purpose of this study was to assess the endothelium of corneal grafts by in vivo confocal microscopy (IVCM), and to evaluate an automated endothelial software system in comparison with a manual cell count and planimetry. Patients and methods Overall, 40 corneal grafts (20 deep anterior lamellar keratoplasties (DALKs) and 20 penetrating keratoplasties (PKs)) were assessed by scanning-slit IVCM. The endothelial cell density (ECD) was estimated with the automated and the manual cell count method of the instrument's Nidek Advanced Vision Information System (NAVIS) software. The results were compared with planimetry as the reference method, and the agreement was assessed. Results The mean ( ± SD) automated ECD was 2278 ± 524 cells/mm 2 (range 1167-3192 cells/mm 2 ), whereas the manual cell count method gave significantly lower ECDs with a mean of 1213±677 cells/mm 2 (range 218-2440 cells/mm 2 ; Po0.001). The manual cell counts were also significantly lower than those by planimetry, with a mean ECD of 1617 ± 813 cells/mm 2 (range 336-2941, Po0.001). Bland-Altman analyses indicated that the limits of agreement (LoA) between the automated and the planimetry method were À671 and þ 1992 cells/mm 2 , whereas they were À1000 and þ 202 cells/mm 2 when comparing the manual cell counts with planimetry. Conclusion Following keratoplasty, the NAVIS automated method is likely to overestimate endothelial cell counts due to oversegmenting of the cell domains. Automated ECDs are substantially higher than those by the manual counting method or planimetry. The differences are considerably larger post-keratoplasty than for normal corneas, and the methods should not be used interchangeably.

show abstract

“…Just as importantly, it could be that there are special factors that might determine polymegethism in Asian groups, assuming that the endothelial morphometry was reliable. It is important to note that that at least some commercially available image software systems are prone to error in that much larger COV values (from what might be considered normal) can be readily obtained, even with a single error in a set of cells …”

mentioning

confidence: 99%

“…It is important to note that that at least some commercially available image software systems are prone to error in that much larger COV values (from what might be considered normal) can be readily obtained, 33 even with a single error in a set of cells. 34,35 A more detailed study of endothelia from those of Asian ethnicity was undertaken, including further consideration of how the polymegethism might be related to ECD. Very high magnification prints and manual planimetry were used to essentially avoid any substantial errors in the morphometry.…”

mentioning

confidence: 99%

A prospective analysis of corneal endothelial polymegethism and cell density in young adult Asians

Doughty

2014

Clinical and Experimental Optometry

View full text Add to dashboard Cite

Purpose:The aim was to assess the morphology of the Asian corneal endothelium, particularly the index of polymegethism and its relationship to endothelial cell density assessments. Methods: The central regions of the corneal endothelium of 72 healthy, normal weight, non-contact lens wearers were assessed by non-contact specular microscopy. There were six groups of persons, aged between 18 and 27 years, whose ethnic origins were self-reported as Asian (Mainland China, Hong Kong, India, Malaysia, Pakistan or other Asian groups). Single images including at least 100 contiguous cells were obtained from each subject and were processed by planimetry after manual border marking to minimise errors. Calculations were made of the coefficient of variation of cell area (COV; polymegethism) as well as the endothelial cell density and percentage of six-sided cells. Results:The COV values ranged from 18 to 30.4 per cent (group mean 24.5 ± 2.8 per cent). The corneas had essentially normal thickness (0.530 ± 0.026 mm), with the endothelia showing a high percentage of six-sided cells (66.3 ± 7.1 per cent) and none showing even mild signs of polymegethism. Endothelial cell density estimates based on average cell areas ranged from 2,020 to 3,623 cells per mm 2 and from 2,157 to 3,835 with calculations based on individual cell areas. The difference between the two estimates of endothelial cell density was strongly related to the coefficient of variation (r = 0.765). Conclusions: This result is consistent with several older reports indicating that it is uncommon to find polymegethism in healthy young adult Asian individuals. Nonetheless, even low coefficient of variation values can substantially affect the estimations of the cell density.

show abstract

A comparison of two methods for estimating polymegethism in cell areas of the human corneal endothelium

Abstract: A centre-dot method using a small number of cells generates useful data on cell area and ECD, but it should be used cautiously for estimates of COV.

Cited by 13 publications

References 21 publications

Simulation of specular microscopy images of corneal endothelium, a tool for control of measurement errors

Simulation of specular microscopy images of corneal endothelium, a tool for control of measurement errors

In vivo confocal microscopy of the corneal endothelium: comparison of three morphometry methods after corneal transplantation

A prospective analysis of corneal endothelial polymegethism and cell density in young adult Asians

Contact Info

Product

Resources

About