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Non-contact Specular Microscopy for Evaluation of Corneal Endothelium in Early Fuchs’ Endothelial Corneal Dystrophy
Jianyan Huang1, MD, PhD; Tudor Tepelus1, PhD; Cristina Modak1, PhD; Vikas Chopra1,2, MD; Srinivas R Sadda1,2, MD; Olivia L Lee1,2, MD
1 Doheny Image Reading Center, Doheny Eye Institute, Los Angeles, California, USA; 2 Department of Ophthalmology, David Geffen School of Medicine, University of California Los Angeles. Los Angeles, USA
Financial DisclosureDr. Sadda
•Consultant: Allergan, Genentech, Regeneron, Optos, Carl Zeiss Meditec
•Research Grant Support: Optos, Carl Zeiss Meditec, Allergan, Genentech
Dr. Chopra
•Consultant: Allergan
•Research Grant Support: Allergan
Dr. Lee
•Consultant: Allergan
•Research Grant Support: Allergan
All other authors
•Nothing to disclose
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Introduction
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Early Fuchs endothelial corneal dystrophy (FECD) is characterized by asymmetrical, bilateral, slowly progressive formation of guttata in the absence of clinically significant corneal edema. Progression of cornea guttata proceeds from the center of the cornea and spreads to the periphery. Endothelial cell attrition rises with increasing number and size of the guttate lesions. Eventually, edema of the corneal epithelium and stroma appears, causing blurred vision.
Accurately assess the cornea endothelial cell density is clinically helpful to estimate the health of the endothelium, but also can track the progression of FECD longitudinally.
Specular microscopy can provide a non-invasive morphological analysis of the corneal endothelial cell layer to detect the early FECD patients and a variety of analysis programs are available to determine corneal endothelial cell density (ECD) and morphometry.
The purpose of this study is to describe the use of non-contact specular microscopy to obtain accurate endothelial cell measurements with Center method or Flex Center method in the face of varying guttata density.
Methods
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Using the Konan NSP 9900 specular microscope, three images of the central corneal endothelium were captured in each eye of normal control and early FECD affected eyes. All the eyes had no history of corneal or intraocular surgery, ocular trauma, keratitis or uveitis.
Patient and subject information
Group Age (years) Number Gender
Control 61.1±15.4 49 eyes (25 subjects) 13 female 12 male
FECD 60.3±14.5 39 eyes (24 patients) 13 female 11 male
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MethodsCorneal endothelial cell analysis using both the Center method and Flex Center method was performed by 2 certified graders. Measurements of ECD, coefficient of variation (CV) and hexagonality (HEX) were then calculated using Konan CellChek software.
Guttata surface area in each image was quantified by ImageJ, an image analysis software.
Variation in ECD values was determined based on the % error and relative standard deviation. Absolute error <5% was considered acceptable agreement.
Results were expressed as means ± standard deviations. Statistical analyses were performed using SPSS ver. 13.0. Statistical methods employed include paired t test, independent t test, Spearman correlation and one way ANOVA.
𝐶𝐷 𝑣𝑎𝑟𝑖𝑎𝑡𝑖𝑜𝑛 ሺ% 𝑒𝑟𝑟𝑜𝑟ሻ= 𝐶𝐷𝐻𝐼𝐺𝐻− 𝐶𝐷𝐿𝑂𝑊𝐶𝐷𝐿𝑂𝑊 × 100 < 5%
Results
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The mean values of endothelial parameters obtained by both Center and Flex Center methods in normal corneas and early FECD-affected corneas.
Normal corneas (n=49)
FECD affected corneas (n=39)
P* FECD affected corneas Frame#1
FECD affected corneas Frame#2
FECD affected corneas Frame#3
P**
Center method
ECD 2669±261 2322±537 0.001 2339±583 2308±603 2324±539 0.949
CV 34±4 29±4 <0.001 29±6 29±5 29±5 0.398
HEX 59±5 59±7 0.973 57±12 61±13 59±10 0.454
Flex center method
ECD 2664±261 2267±583 0.001 2275±579 2264±596 2267±584 0.906
CV 36±4 35±5 0.297 35±6 33±6 34±4 0.638
HEX 58±6 60±6 0.112 59±7 62±10 60±7 0.806
* Comparisons between the normal corneas and FECD affected corneas were made by paired t test.** Comparisons among the 3 different images from the same FECD affected corneas were made by one way ANOVA.
Results
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Correlation of overall guttata area with endothelial parameters in FECD-affected cornea.
Spearman correlation coefficient
P
Center method ECD -0.340 0.001
CV -0.314 0.001
HEX -0.174 0.069
Flex center method ECD -0.433 <0.001
CV -0.152 0.014
HEX -0.055 0.665
Results
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Agreement between Center method and Flex center method based on differences in the number (NUM) of identified cells applied to the calculation of ECD.
NUM Percentage of Error ≥5%
≤ 10 56.25 (9/16)
10< NUM ≤ 15 25 (3/12)
15< NUM ≤ 20 50 (3/6)
20< NUM ≤ 30 20 (2/10)
>30 12.3 (9/73)
Total 22.2 (26/117)
Results
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Frame
#1
#2
#3
Three representative eyes with early FECD, showing the ungraded specular image and the same image manually graded by Center and Flex center methods. (INP: input dots by grader).
Conclusions
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In early FECD, both Center and Flex center methods can be used to reliably determine ECD.
ECD values are lower in FECD-affected corneas than in control eyes.
The overall guttata has a negative correlation with ECD value, but is unrelated to CV and HEX.
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