Objective quantification of corneal haziness using anterior segment optical coherence tomography

Abstract

PurposeTo quantify normal corneal transparency by anterior segment optical coherence tomography (AS-OCT) by measuring the average pixel intensity. To analyze the variation in the average pixel intensity in mild and severe grades of corneal opacities.MethodsThis is an observational, cross-sectional study of 38 eyes from 19 patients with mild or severe grades of corneal opacities greater than 3 mm and a normal contralateral cornea. AS-OCT was performed centered on the opacity with a 3 mm cruciate protocol. A similar image is taken of the contralateral clear cornea in the same quadrant. The average pixel intensity was calculated in a standardized manner using MATLAB software.ResultThe average pixel intensity of the normal cornea was 99.6 ± 10.9 [standard deviation (SD)]. The average pixel intensity of the mild and severe corneal opacities was 115.5 ± 9.1 and 141.1 ± 10.3, respectively. The differences were statistically significant.ConclusionsAS-OCT images can be used to quantify corneal transparency. Average pixel intensity is a measure that varies significantly with varying corneal opacification.

Small incision lenticule extraction and femtosecond-assisted laser in situ keratomileusis in patients with deep corneal opacity: case series

“…Of note, although SMILE reported no adverse effects on corneal endothelial cells [17] , careful evaluation by specular microscope preoperatively, or even long-term follow- AS-OCT is an effective approach to detect morphological changes such as corneal atrophy or corneal edema according to the optical density [18][19] . Corneal transparency and grades of corneal opacities can be quantified using AS-OCT [20] . In this work, AS-OCT was applied to confirm the depth, area, and density of corneal opacity to assist the surgery design.…”

Case report: Utilization of neutral density filters for densitometry analysis of dense corneal opacities

“…Other modalities, such as OCT have been attempted for this purpose in the past, however, to date, there exists no standardized, validated, integrated OCT opacity analysis system with which to analyze the imaged cornea. 2 …”

“…One example of a density scale utilized in clinical care is categorizing corneal opacities into three grades: nebular, macular and leucoma. 2 , 3 This subjective qualitative system evaluates not only the density of the opacification but also the practitioner's ability to visualize iris architecture details, which may be obscured by the corneal pathology. Many clinicians instead prefer a numerical subjective system that is used to grade the corneal opacity from zero (clear cornea) to three (dense opacity), which relies on categorizing the opacity by both the density and the ability to visualize the underlying intraocular structures.…”

Detection of fine modifications in bulk corneal grafts based on backscattered light quantification

“…If the resolution is high enough, OCT can reveal lakes of water between the lamellas [14]. In vivo studies demonstrated that analyzing the backscattered light from OCT corneal images enables corneal transparency to be quantified [15]. When the average measured pixel intensity of a cornea which had lost transparency was compared with that of a normal cornea, average pixel intensity was shown to vary significantly with varying corneal opacification.…”