Scale for Photographic Grading of Vitreous Haze in Uveitis

Purpose

To validate a scale for grading vitreous haze in uveitis using digitized photographs and standardized scoring.

Design

Evaluation of clinical research methodology.

Methods

Calibrated Bangerter diffusion filters inducing incremental decrements of spatial contrast were placed in front of the camera lens while photographing a normal eye to simulate vitreous haze. The photographs were digitized and an ordinal scale was created from 0 (none) to 8 (highest level of opacification at which fundus details could be seen). The scale steps correspond approximately to decimal Snellen visual acuities of 1.0, 0.8, 0.4, 0.2, 0.1, 0.04, 0.02, 0.01, and 0.002, with approximately 0.3 log step between each step. For validation, digitized fundus photographs of uveitis patients were displayed on a computer monitor for comparison with the standard photos. Three observers graded the test set twice under standard conditions. Interobserver and intraobserver variability and κ values for agreement greater than chance were calculated.

Results

Variance component analysis determined that 87.7% of the variance in grades was attributable to the test item rather than to grader or session. The intraclass correlation between graders and grading sessions varied from 0.84 to 0.91. Simple agreement within 1 grade between graders and sessions occurred in 90 ± 5.5% of gradings. κ values averaged 0.91, which is considered near perfect.

Conclusions

A 9-step photographic scale was designed to standardize the grading of vitreous haze in uveitis patients using fundus photographs. The scale is potentially adaptable to clinical trials in uveitis.