A new objective system for grading corneal haze

J. A. Laird, R. W. Beuerman, C. A. Harlow, S. C. Kaufman, S. J. Chew

Research output: Contribution to journalArticlepeer-review


Purpose. The purpose of this study was to develop a grading scale based on digital image properties to objectively quantify the corneal haze that accompanies swelling of the stroma, which is more precise and reliable than the familiar 4-tiered scale. Methods. In vivo confocal images of the cornea were obtained from rabbits before and immediately after excimer laser refractive surgery and then daily for six days. Images show trends in the frequency of occurrence and characteristics of a number of detectable morphological features. This system approaches the problem by quantifying detectable features such as the density, size, and reflectivity of keratocyte nuclei, and the frequency and reflectivity of fibrous processes that stem from activated keratocytes. Results. Quantification of morphological features that are concomitant to increased haziness results in a set of indices for each image that indicate its position along the trend lines observed in experimental data, thus indicating the degree of haziness of the image. In these images, the nuclear size (in pixels) was 504±43 before and immediately after PRK, and changed to 294±32, 214±40, and 194±17 as haze was developing. Nuclei were not detectable in extreme haze. The normalized nuclear reflectivity varied from 1.00 before and immediately after PRK to 1.03, 1.39, 3.09, and 3.55 as haze was developing. Similarly, nuclear density changed from 570 cells/mm2 to 770 cells/mm2. Conclusions. The objective grading of haze by computer-based algorithms can effectively replace the truncated 4-tiered subjective clinical grading system currently in use to characterize corneal damage. Such a system would be useful in assessing the degree of wound healing following laser surgery.

Original languageEnglish (US)
Pages (from-to)S58
JournalInvestigative Ophthalmology and Visual Science
Issue number3
StatePublished - Feb 15 1996
Externally publishedYes


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