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Comparison between live and photographed slit lamp grading of corneal staining
Luigina Sorbara1, Rachael Peterson, Simone Schneider
1*OD, MSc, FAAO †PhD, BSc(Hons), MCOptom, FAAO ‡PhD §MCOptom, PhD, FAAO Centre for Contact Lens Research, School of Optometry and Vision Science, University of Waterloo, Waterloo, Ontario, Canada (LS, RP, SS); and Deakin Optometry, School of Medicine, Deakin University, Melbourne, Victoria, Australia (CW).
Purpose:
To compare live and photographic (still) grades of corneal staining of the same eyes and the repeatability of grading between two investigators.
Methods:
Thirty patients were recruited to participate in a contact lens study, and their level of corneal staining was graded by two investigators in situ (live images), using slit lamp biomicroscopy. Digital still images of the corneal staining were also captured during the study visits. An independent observer selected 105 of the still images graded by investigator 1 and another 105 images graded by investigator 2 and presented them to the original investigator in a random order, on three separate occasions. Grading was performed at the time of the live grading and the three still image sessions, using the Centre for Contact Lens Research corneal staining scale that combines grades of both extent and type to provide an overall "global staining score" from 0 to 10,000 for corneal staining. A comparison was made between live and still grades as well as the intrainvestigator repeatability for the multiple grading of the still images.
Results:
The mean (±SD) of corneal staining grades recorded for the same eyes examined live and then later on three occasions was 1795 (±1083) and 714 (±974), respectively, for participants examined by investigator 1 (p < 0.001) and 1854 (±1075) and 461 (±411) for those examined by investigator 2 (p < 0.001). There was a significant difference over the three repeated still grading sessions for each investigator (p < 0.001), although there was a high degree of consistency among the three still grading sessions for each of the investigators: the intraclass correlation for investigator 1 was 0.91 (confidence interval, 0.87 to 0.93) and that for investigator 2 was 0.82 (confidence interval, 0.77 to 0.87).
Discussion:
Digital still image grading of corneal staining significantly underrepresented the amount of corneal staining observed through a slit lamp. Clinical investigators graded corneal staining with a high degree of consistency.
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