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A. Ntola, P.J. Murphy; The Effect of Iris Pigmentation and Ethnic Origin on Corneal and Skin Sensitivity, and on Tear Film Break–Up Time and Blink Rate . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4397.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess the effect of iris pigmentation and ethnic origin on corneal sensitivity (CS), skin sensitivity (SS), tear film break–up (BUT) and blink rate. Methods: Subjects (n=172) were recruited for the study and allocated to four ethnic groups: 1) 86 Caucasian (m=28, f=58, age=23.5±3.7), 2) 40 Asian (m=5, f=35, age=21.9±3.5), 3) 30 Chinese (m=10, f=20, age=24.3±5.6), and 4) 16 Black African (m=6, f=10, age=24.2±3.9). Ethical approval was obtained and subjects were asked to sign a consent form prior to participating. Subjects were also classified according to the Iris Color Classification System. All measurements were made on the right eye only and after 12 noon to avoid any diurnal bias. Central CS was measured using the Non–Contact Corneal Aesthesiometer (NCCA), which stimulates the cold sensitive C fibres. SS was assessed at the upper closed eyelid using the NCCA. Tear film break–up time was assessed following the instillation of 0.7µl of fluorescein. The blink rate was recorded for 5 minutes without the subject's knowledge. Results: 1) Caucasians had a progressive decrease in sensitivity with increasing iris pigmentation (R2=0.97). 2) No difference in CS was found between ethnic groups (ANOVA, p>0.05) except for Asian/African groups, with Africans being less sensitive than Asians (t–test, p=0.02). 3) A significant difference in SS was found only between the Chinese and Africans groups (t–test, p<0.05). 5) No significant correlation was found for CS and SS between each ethnic group. 6) A weak but significant correlation was found between blink rate and BUT for all ethnic groups, with blink rate decreasing as BUT increases (R2=0.28). Conclusions: 1) Iris pigmentation influences CS; as iris pigmentation increases, CS decreases. 2) No significant difference was found in CS, SS, BUT and blink rate between the ethnic groups. 3) BUT and blink rate are weakly correlated; as blink rate increases, BUT decreases.
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