Abstract
Purpose: :
To investigate the association of a change at 2 years in cataract score, using the Age-Related Eye Disease Study (AREDS) lens classification system, with progression to cataract surgery or visual acuity loss of 2 lines or greater by 5 years.
Methods: :
AREDS participants were assessed for severity of nuclear, cortical, and posterior subcapsular (PSC) cataract using a standardized grading of retroillumnination and slit lamp lens photographs taken at baseline and annually. Nuclear cataracts were graded for optical density using a decimalized scale of 0.9-7.1, while cortical and PSC cataracts are graded for area of lens involvement, ranging from 0-100%. History of cataract surgery and and best corrected visual acuity were assessed every 6 months. Logistic regression analyses were used to assess the association between the change in lens opacities at 2 years and the outcomes by year 5 adjusting for baseline characteristics: age, sex, smoking, diabetes, AMD severity, cataract severity, history of cataract surgery in the fellow eye, and presence of multiple cataract types.
Results: :
At baseline the median scores by lens opacity type were: 2.0 for nuclear (n = 7565 eyes) and 0.2 and 0.0 for cortical and PSC cataracts respectively (n = 7579 eyes). The adjusted odds ratios (ORs) for the association of the clinically important outcomes by 5 years with progression of nuclear lens opacity by 1.0 or more but less than 2.0 units at 2 years, compared with less than a 1.0 unit change, were; 2.27 for cataract surgery (p<.0001) and 1.24 for ≥ 2 line vision loss (p=.008). For a ≥ 5 to <10-unit increase in cortical lens opacity at 2 years, compared with eyes showing a <5-unit increase, the ORs were: 2.53 for progression to cataract surgery (p=.0001) and 1.23 for ≥ 2 line vision loss (p=.058). For this same comparison of lens opacity progression, these ORs for PSC were: 3.57 (p=.003) and 1.70 (p=.008), respectively.
Conclusions: :
These results demonstrate that modest progression of all three types of lens opacities at 2 years on the AREDS cataract grading system are associated with an increased likelihood of clinically important outcomes (cataract surgery and visual acuity loss) by 5 years. Due to its predictive value, short term change in lens opacity, based on the AREDS lens classification system, may be a useful outcome variable for clinical research.
Clinical Trial: :
http://www.clinicaltrials.gov NCT00001312
Keywords: cataract • clinical (human) or epidemiologic studies: risk factor assessment • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology