The Perceived Bulbar Redness of Clinical Grading Scales

Abstract

Subjective estimates of redness are based on a combination of chromaticity and vessel-based components. Psychophysical scaling of perceived redness lends itself to being used to cross-calibrate these four clinical scales.

Grading Bulbar Redness Using Cross-Calibrated Clinical Grading Scales

“…9,12,17 The ability to convert redness grades obtained with different grading scales would be particularly valuable for research settings, however, and it seems that if grading scales were better aligned, a comparison between grading estimates may be possible. In an attempt to achieve a better comparability of redness estimates, we have introduced a psychophysical scaling model 21,22 that allowed the perceived redness of the McMonnies/Chapman-Davies (MC-D), IER, and Efron bulbar redness grading scales to be quantified for a 0 to 100 redness range relative to the reference images of the VBR scale. 22 Similar to the studies using objective metrics, 16 -18 the perceived redness data also indicated a misalignment of the reference images between scales, and detected widely different dynamic ranges (i.e., the range that is covered by the reference images) between the scales.…”

“…The same 10 participants that had also participated in the previous redness scaling experiments 21,22 were asked to represent perceived bulbar redness of printed color copies of the sample images (5 ϫ 3 cm) by placing them relative to the unlabeled reference images of one of the four scales. No time constraints were imposed for completion of the task.…”

“…The start and end point of this 1.5 m range corresponded to the minimum and maximum redness level, and were labeled by 0 and 100, respectively. Within this range, the modified reference images of each scale (i.e., after removal of potentially confounding features such as lids or lashes) 21 were presented so that their position matched their newly determined, calibrated reference grades (Table 1). 22 The grading task took place under full room illumination (cool white fluorescent lighting; general color rendering index 84).…”

“…The participants had no previous experience with grading of ocular conditions, other than having completed the scaling of the reference images. 21,22 After the placement of each image, its position was measured, translated into its corresponding redness grade between 0 and 100, and removed before the next sample image was presented for assessment. Each participant estimated the redness of the sample images four times, once per scale, with a break of at least two days between each grading session.…”

“…Redness was subjectively estimated on a table top within the same 1.5 m range that had been used for the psychophysical scaling 21,22 and the subsequent calibration 22 of the reference images of the MC-D, IER, Efron, and VBR scales. The start and end point of this 1.5 m range corresponded to the minimum and maximum redness level, and were labeled by 0 and 100, respectively.…”