Abstract
Purpose: :
Prostaglandin analog use is associated with periocular skin hyperpigmentation. However, no standardized method exists to objectively measure this change. Our study examined the color indices and reproducibility of the Minolta CR–400 chromameter in measuring periocular pigmentation in normal Caucasian and African–American adults.
Methods: :
25 Caucasian (mean age 68.4) and 26 African–American (mean age 64.4) subjects with healthy skin and no eye or skin medication use in the past 6 months were enrolled. Subjects were further grouped according to the Fitzpatrick skin classification system based on skin color and reaction to sun exposure. Skin color was measured with the CR–400 which reads light reflected off skin at 3 wavelengths. The light was analyzed by the L*a*b* system, where value L* = luminance of color, a* = redness and greenness, and b* = yellowness and blueness. Three serial readings were taken from each patient from the forehead, right cheek, and 7 points around each eye. Two instruments were used to test inter–instrument variability. P–values reported are the upper limit of a range.
Results: :
Significant differences in L* a* b* values were noted between each Fitzpatrick skin type, for all locations (p = 0.030) by Kruskal–Wallis analysis. L* a* b* differences between Caucasian and African American groups as a whole showed significance for all periocular locations (p = 0.038). In the 3 Fitzpatrick groups within African Americans, all 3 indices varied significantly between groups (p = 0.018). In Caucasians however, only L* varied significantly among Fitzpatrick groups (p = 0.047). Furthermore, L* a* b* measurements at 3 different locations on the upper and lower lids showed variability for all 3 indices in both ethnic groups. Repeated readings on the upper and lower lids show very good intra (ICC = 0.80–0.99) and inter–instrument (ICC = 0.95–0.99) reproducibility by intra–class correlation analysis.
Conclusions: :
The CR–400 can be used to objectively and reproducibly measure periocular skin pigmentation in both Caucasians and African Americans. These color indices showed significant differences between each of 6 Fitzpatrick skin types as well as between Caucasians and African Americans. Our study also showed that measurements of multiple points around the eye are necessary to control for small but significant variability in pigmentation in different periocular locations.
Keywords: drug toxicity/drug effects • pharmacology • eyelid