Automated Retroillumination Photography Analysis for Objective Assessment of Fuchs Corneal Dystrophy

Abstract

Purpose Retroillumination photography analysis (RPA) is an objective tool for assessment of the number and distribution of guttae in eyes affected with Fuchs Corneal Dystrophy (FCD). Current protocols include manual processing of images; here we assess validity and interrater reliability of automated analysis across various levels of FCD severity. Methods Retroillumination photographs of 97 FCD-affected corneas were acquired and total counts of guttae previously summated manually. For each cornea, a single image was loaded into ImageJ software. We reduced color variability and subtracted background noise. Reflection of light from each gutta was identified as a local area of maximum intensity and counted automatically. Noise tolerance level was titrated for each cornea by examining a small region of each image with automated overlay to ensure appropriate coverage of individual guttae. We tested interrater reliability of automated counts of guttae across a spectrum of clinical and educational experience. Results A set of 97 retroillumination photographs were analyzed. Clinical severity as measured by a modified Krachmer scale ranged from a severity level of 1 to 5 in the set of analyzed corneas. Automated counts by an ophthalmologist correlated strongly with Krachmer grading (R2=0.79) and manual counts (R2=0.88). Intraclass correlation coefficient demonstrated strong correlation, at 0.924 (95% CI, 0.870- 0.958) among cases analyzed by three students, and 0.869 (95% CI, 0.797- 0.918) among cases for which images was analyzed by an ophthalmologist and two students. Conclusions Automated RPA allows for grading of FCD severity with high resolution across a spectrum of disease severity.

Towards Clinical Trials in Fuchs Endothelial Corneal Dystrophy: Classification and Outcome Measures—The Bowman Club Lecture 2019

“…Furthermore, these scales are based on subjective clinical assessment, and can result in cornea specialists agreeing less than 50% of the time 34. Photographic grading of guttae distribution is a more objective assessment of the distribution and extent of guttae,43 44 but this method is not simple to standardise within and between clinical practices, and does not help to define the presence or severity of corneal oedema.…”

“…49 It is unknown if any treatments will result in the resolution of guttae (without excising host Descemet membrane) at this time; endothelial imaging might therefore be helpful to assess the confluency and area occupied by guttae before and after intervention. The latter will require sampling multiple regions of cornea because of regional variation of guttae49; retroillumination photography may have a role too 43 44…”

Peripheral Endothelial Cell Count Is a Predictor of Disease Severity in Advanced Fuchs Endothelial Corneal Dystrophy

“…Slit lamp grading evaluates the area of guttae coalescence and presence of edema. 6 An additional method used to determine severity is retroillumination photograpy, 9,10 which has been employed to detect formation of new guttae over time. 11 However, manual counting can be time-consuming.…”

Imaging the Corneal Endothelium in Fuchs Corneal Endothelial Dystrophy

“…Retroillumination of the cornea is another important technique to assess and document the distribution and number of guttae. 9,10 After pupillary dilation, the cornea is examined with reflected light from the fundus using a small angle between the illumination and biomicroscope. 10 This retroillumination technique results in the visualization of individual and confluent guttae from light scattering ( Figure 1).…”

“…10 Retroillumination photography analysis is an effective way to document the number and distribution of guttae, and to demonstrate the formation of new guttae and progression over time. 9,10 To address the resource-intensive nature of manually counting guttae, an automated method for retroillumination photography analysis has been developed and has shown to be highly correlated with both manual and Krachmer grading of guttae. 9 While the slit-lamp examination including specular reflection and retroillumination is an essential part of the clinical examination, additional objective diagnostic testing such as specular microscopy and confocal microscopy are often needed for a more comprehensive evaluation of the CE for initial diagnosis or ongoing management.…”