Iris color and visual functions.

BACKGROUND: The aim of this study was to evaluate if iris color is associated with differences in visual functions such as intraocular straylight (IOSL), contrast sensitivity (CS), or best-corrected visual acuity (BCVA). METHODS: In this retrospective cohort study, which is a subgroup analysis of a large prospective trial about visual impairments in European car drivers, we included 853 persons between 20 and 80 years of age and without a history of ocular surgery or any eye disease including cataract. Subjects participated in an ophthalmological examination, grading of lens opacity, and the measurement of visual functions such as IOSL, CS, and BCVA. Dependent on iris color, participants were divided into four groups: light-blue, blue-grey, green-hazel, and brown. RESULTS: Independent of age, IOSL was significantly (all p values < 0.0001, Fisher's LSD test) higher in participants with light-blue colored iris (1.14 log(IOSL) [95 % CI: 1.11-1.17]) compared to participants with blue-grey (1.07 log(IOSL) [95 % CI: 1.05-1.09]), green-hazel (1.06 log(IOSL) [95 % CI: 1.04-1.08]) or brown (1.06 log(IOSL) [95 % CI: 1.04-1.08]) iris color. CS was also lower in participants with light-blue pigmented irises (1.60 log(CS) [95 % CI: 1.58-1.62]) than in the other groups, but statistically significant (p = 0.013, Fisher's LSD test) only compared to brown iris color. For BCVA we could not found any difference between the four groups. CONCLUSIONS: We could show in this study that iris color has a significant impact on IOSL and to a lower degree on CS, but not on BCVA. Persons with light-blue iris color who showed significantly higher IOSL values therefore may experience disability glare in daily situations such as driving at night more often than others.

Cataract and pseudophakia in elderly European drivers.

PURPOSE: To evaluate the prevalence and association of different types and severities of cataract or pseudophakia with visual impairments in older European drivers. METHODS: In this prospective European multicenter study, 2211 active drivers, 45 years of age and older, participated in an ophthalmologic examination, the measurement of visual functions, and were asked to fill in the NEI-VFQ-25 and another questionnaire about driving habits, driving difficulties, and self-reported accidents. RESULTS: Prevalence of moderate and severe forms of cataract in an active driving population is lower than that in the general population, but could be found in both eyes in 20% (95% confidence interval [CI] 16%-25%) and 17% (95% CI:13%-21%) of subjects 75 years of age and older. In addition, there is a strong relationship between severity of cataract and parameters such as age, visual acuity, intraocular straylight, and contrast sensitivity. CONCLUSIONS: Cataract is not as highly prevalent in the elderly active driving population as in the general population, but is frequently present in drivers over 65 years of age. Lower prevalence of severe bilateral cataracts in countries with mandatory tests of visual functions of drivers suggest that this could be a suitable measure to detect and to reduce the number of active drivers with severe bilateral cataracts.