comparison of endothelial cell count by manual and automated methods in normal corneas and in...
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Comparison of Endothelial Cell Count by Manual and Automated Methods in Normal Corneas and in
Fuchs' Endothelial Dystrophy
Somasheila I Murthy, Debarun Dutta, Varsha M Rathi
Cornea and Anterior Segment Services, L V Prasad Eye Institute, Hyderabad, India
Poster ID: 16856
Financial Disclosures
None of the authors have any financial
disclosures
• Endothelial cells are critical to maintain corneal transparency and its count is an indicator of endothelial health or disease 1, 2, 3
• The cell count software of NIDEK Confoscan 4 is regularly used to perform corneal endothelial cell analysis, either automatically or manually
• Accuracy of automated analysis falls as the cornea is more and more diseased4
• Manual count is recommended, however this is time consuming
BACKGROUND
1. Klias et al , Comparison of endothelial cell count using confocal and contact specular microscopy. Ophthalmologica. 2003 Mar-Apr; 217(2):99-103.
2. Modis L Jr et al , Corneal endothelial cell density and pachymetry measured by contact and noncontact specular microscopy. J Cataract Refract Surg. 2002 Oct;28(10):1763-9.
3. Doughty MJ et al, Toward a quantitative analysis of corneal endothelial cell morphology: a review of techniques and their application. Optom Vis Sci. 1989 Sep; 66(9):626-42.
4. 4. NAVIS for Confoscan 4 Operator’s Manual (2005-2007)
Hypothesis: There is a cut-off at which automated count is accurate and reliable
Purpose: To evaluate the difference in endothelial cell count between automated and manual methods in healthy corneas and in Fuchs’ endothelial dystrophy
Methods: • Retrospective observational study• Data was analysed by single experienced observer• One hundred images from both healthy and Fuchs’
endothelial dystrophy were selected for the study• Archived images from the NIDEK Confoscan 4 were
used to procure endothelial cell counts by automated and manual methods
PURPOSE, METHODS
The following parameters were required to select the image:
• Endothelial images: clear on all slides • At least 50 cells were taken in each in slide• After having selected the Region of Interest, the
automatic cell count was processed• For manual count, cells were selected in the region
of interest. Density information was calculated as: Density = cells in polygon / Polygon area [cells/mm2]
• Difference between two methods of >250 cells/mm2 was considered clinically significant
INCLUSION CRITERIA
Automated: 2613 cell/mm2Manual mode: 2578 cell/mm2
Normal cornea
Automated: 1675cell/mm2Manual mode: 1503 cell/mm2
Grade 2 Fuchs’
Manual mode: 423 cell/mm2 Automated: 1776 cell/mm2
Advanced Fuchs’
RESULTS
Table 1. Endothelial cell counts (cells/mm2) in healthy and Fuchs' dystrophy cornea
Images Average
auto count
Average
manual count
Average
difference
Range of
cells(differen
ce)
p value
Healthy
cornea
100 2471.24 ±
273.19
2444.50 ±
370.30
125.67 ±
86.9
2 to 402 cells 0.0463
Fuchs'
Dystroph
y
100 1827.73 ±
334.31
1196.71 ±
637.29
633.04 ±
435.03
54 to 1631
cells
<0.0001
RESULTS
Table 2. Endothelial cell counts done by automated and manual methods in images from Fuchs'
dystrophy
Number
of Images
Average
auto count
Average
manual count
Average
difference
Range of
cells
(difference)
p value
Cell count more
than 1000 cells /
mm2
49 2028.73 ±
329.53
1719.82 ±
489.47
312.96 ±
337.27
2 to 402
cells
<0.0001
Cell count less
than 1000 cells /
mm2
51 1626.73 ±
186.50
673.62 ±
149.52
953.12 ±
246.70
54 to1631
cells
<0.0001
• Advantage of automated mode is that there is no inter-observer variability, it is faster, repetitive and is independent of users’ experience and skills5
• In the other hand manual mode is time consuming needs higher level of technical skills and thereof it is unsuitable in busy clinic
• In our study the results have shown a large variability between the two methods (as much as up to more than 900 cells/mm2 difference) in advanced cases of Fuchs’ dystrophy.
Discussion
5. Imre L et al, Reliability and reproducibility of corneal endothelial image analysis by in vivo confocal microscopy. Graefes Arch Clin Exp Ophthalmol. 2001 Jun; 239(5):356-60.
• Decision on surgery in Fuchs’ often is aided by the cell count.
• Performing the test in automated mode would overestimate the count, thus delaying the surgical intervention and perhaps final outcome
• Both the clinician and investigator need to be aware
• More advanced diseased corneas should undergo manual count
Discussion
• In healthy corneas, any method can be used• Diseased corneas: the accuracy of the automated
count decreased with decrease in total cells• Manual count is therefore more reliable in
compromised endothelium • Automated count overestimates the results, and
can even give a value in normal range, thus misleading the clinician
Conclusion