Purpose:
Age-related lens opacities are the most common cause of vision loss worldwide. The purpose of the Irish Nun Eye Study (INES) is to assess the prevalence of age-related macular degeneration (AMD) and cataract in a community with a protected lifestyle.This study reports the prevalence of cataract in this population and correlates this with risk factors including UV-light exposure and hormonal levels.
Methods:
Nuns from Ireland were enrolled in the study (n= 1242). Information was collected on demographic, ophthalmic and medical status, dietary intake and sunlight exposure. Participants had a full ophthalmic examination, fundal imaging, macular pigment measurements, skin and iris photographs and lens imaging with the Neitz Cataract screener. A subgroup (20%) were also imaged using the Scheimpflug camera. Neitz cataract images were graded according to the Wisconsin protocol.The average percentage of the surface area of the lens was classified as: 0 to <5%; >5% to<25% and >25%. UV light exposure was calculated using a modification of the method described by Taylor et al (1992).
Results:
Data were available on 2466 eyes (age range 52-100 years) 75.3% were phakic, 24.2% were pseudophakic, 0.5% were ungradable.The prevalence of cortical opacities (CO) was: <5% (41.4%), 5 to 25% (45%) and 25-100% (13.6%). The prevalence of posterior subcapsular opacities (PSCO) was 0% in 92.3% of eyes, >0 to < 5% (7.1%), >5% to <25% (0.5%) and > 25% (0.1%). Both CO and PSCO increased with increasing age p<0.001 and p=0.001 respectively. Late menopause (p=0.04) was protective for both. HRT and hysterectomy with HRT were also protective. Hysterectomy alone or early menopause was a risk factor. Exposure to UV light was protective for CO (p=0.036) but risk for PSCO (p=0.013). The prevalence of CO for the age group > 75 years was 46.5% in INES and 42.4% in Beaver Dam Eye Study (BDES). For PSCO the prevalence >75 years was 0.51% in INES and 14.3% in BDES.
Conclusions:
The prevalence of CO in the INES population is similar to that in females in the BDES which is a comparable population, however the prevalence of PSCO is significantly less. Our study also indicates that UVR is not a risk factor for CO in women but is risk for PSCO.
Keywords: cataract • radiation damage: light/UV • clinical (human) or epidemiologic studies: prevalence/incidence