Refractive Associations with Cataract: the Blue Mountains Eye Study

Abstract

purpose. To assess the relationship between myopia and age-related cataract in a defined older population.

methods. A cross-sectional study of 3654 people aged 49 to 97 years was conducted in the Blue Mountains near Sydney, Australia, from 1992 through 1994. General medical, eye, and refractive history and information about confounders were collected by questionnaire. Participants had a detailed determination of refraction, and the spherical equivalent refraction of each eye was calculated. The Wisconsin Cataract Grading System was used in masked grading of slit lamp and retroillumination lens photographs, to assess presence and severity of nuclear, cortical, and posterior subcapsular (PSC) cataract. Data from both eyes were analyzed by the generalized estimating equation method, adjusting for cataract risk factors.

results. Included in the analysis were 7308 eyes. A history of wearing distance glasses, excluding eyes with current hyperopic refraction, was used as a proxy for myopia. Subjects who had worn distance glasses were more likely to have nuclear cataract (odds ratio [OR] 1.3; confidence interval [CI] 1.0–2.1). After stratification by age at first wearing distance glasses, this relationship remained only for people who first wore distance glasses after age 40 years (OR 1.3; CI 1.0–1.8), which suggested a myopic refractive shift from developing nuclear opacity and was supported by the weak association found between current myopic refraction and nuclear cataract (OR 1.3; CI 1.0–1.6). Eyes with onset of myopia before age 20 years had the greatest PSC cataract risk (OR 3.9; CI 2.0–7.9). This was supported by the finding of an association between current myopic refraction and PSC cataract (OR 2.5; CI 1.6–4.1). PSC cataract was inversely associated with hyperopia (OR 0.6; CI 0.4–0.9). Refraction-related increasing odds were found between PSC cataract and myopia: low myopia (OR 2.1; CI 1.4–3.5), moderate myopia (OR 3.1; CI 1.6–5.7), and high myopia (OR 5.5; CI 2.8–10.9). High myopia was associated with PSC, cortical, and late nuclear cataract.

conclusions. Early-onset myopia (before age 20 years) may be a strong and independent risk factor for PSC cataract. The findings suggest the possibility of a dose response between levels of myopia and PSC cataract. Nuclear cataract was associated with presumed acquired myopia, whereas high myopia was associated with all three types of cataract.

Moderate to high myopia has a known association with age-related cataract. ^{1 2 3} However, for lower levels of myopia this relationship has been disputed. ^{1 4 5} Although many studies have suggested that low myopia may be an important risk factor for cataract, ^{4 6 7} there have been few recent reports of examination of this association. In particular, no population-based studies have explored the potential relationship between low levels of myopia and the principal types of age-related cataract. 

Perkins performed a retrospective study of patients who had undergone cataract surgery and reported an association between low myopia and cataract. ⁴ However, this study was limited by the availability of past refraction records in only 17% of subjects. In two hospital-based case–control studies from Oxfordshire (United Kingdom), ^{6 7} Harding reported an association between childhood myopia and cataract, but did not subdivide the age-related cataract types. He estimated that 7% of cataract was directly attributable to myopia. ⁷ Two other studies that reported an association also did not subdivide cataract types. ^{2 8}  

Recent studies have examined the relationship between a history of wearing glasses in youth and individual types of age-related cataract. Although no association was found with either nuclear, cortical, or PSC cataract, the Lens Opacities Case–Control Study reported an association between a history of wearing glasses before age 20 years (interpreted as a proxy for myopia) and mixed cataract (OR 1.44). ⁹ The Beaver Dam Eye Study ¹⁰ examined individual cataract types in the worse eye and compared people who had worn distance glasses before age 21 years with those who had begun wearing distance glasses after age 40 years. Use of distance glasses before age 21 years had a statistically significant association with PSC cataract (OR 1.20) in women, but not in men (OR 1.06), after controlling for age. After controlling for other confounders, this association in women was stronger (OR 1.43), although not statistically significant (95% CI 0.98–2.08). A history of wearing distance glasses before age 21 years in men was associated with a significantly lower risk of nuclear cataract (OR 0.77), and wearing glasses was also interpreted as protecting against ultraviolet radiation. 

We designed in the present population-based cross-sectional study to explore whether refractive error, particularly increasing levels of myopia, could precede and be an independent risk factor for age-related cataract, after taking into account the effects of other known cataract risk factors. Further, we attempted to examine temporal aspects of the relationship between myopia and development of cataract. 

Methods

The Blue Mountains Eye Study is a population-based study of the prevalence and causes of age-related vision loss, conducted in two urban postal code areas of the Blue Mountains region near Sydney, Australia. The study population and methods have been described previously. ¹¹ After a private census, all permanent residents aged 49 years or older, were invited to participate. Of 4433 age-eligible residents, 3654 people (82.4%) aged 49 to 97, participated from 1992 through 1994, including 2072 women and 1582 men (mean age, 66 years). There were 68 people who died and 210 who moved from the area (6.3%) before they could be examined. The remaining 501 people refused examination, including 353 (8.0%) who permitted a brief interview and 148 (3.3%) who refused any participation. Residents who attended for the examination were more likely to wear glasses currently and to have hypertension and were less likely to have ever seen an ophthalmologist than were nonattenders. ¹² Nonparticipants were also slightly older but had a similar gender distribution and prevalence of doctor-diagnosed eye disease (cataract, glaucoma, and age-related macular degeneration) to participants. Ethical approval for the study was obtained from the Western Sydney Area Human Ethics Committee and written, informed consent was obtained from all subjects. The research was conducted according to the recommendations of the Declaration of Helsinki. 

A standardized questionnaire was administered by trained interviewers that included eye and general medical histories, use of medications, and demography. Several questions regarding myopia were included, such as: “Do you wear glasses (that includes bifocals or multifocals) to see clearly in the distance, or have you in the past?” and “How old were you when you first needed to wear glasses to see clearly in the distance?” Objective refraction was performed using an autorefractor (model 530; Humphrey, San Leandro, CA) and was followed by subjective refraction, according to the Beaver Dam Eye Study modification of the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol and a logMAR chart. ^{11 13} The spherical equivalent refraction (SER) defined as the sum of the best-corrected spherical refraction plus half the cylindrical refraction, was used to categorize current refractive status. 

The questionnaire also asked about known and potential risk factors for cataract, including a history of diabetes, hypertension, smoking, and use of inhaled or oral steroids. Hypertension was defined as a history of treated hypertension and/or systolic blood pressure higher than 160 mm Hg or diastolic pressure higher than 90 mm Hg. Sun-related skin damage to the hands, forearms, and face was assessed by a single senior examiner (PM) and graded as none, present, mild, moderate, or severe. 

At the clinic visit, a detailed eye examination was performed. Photographs of the lens of each eye were taken after pupil dilatation with 1% tropicamide and 10% phenylephrine drops. The protocol for lens photography and grading closely followed the Wisconsin Cataract Grading System ^{14 15} developed for the Beaver Dam Eye Study. Slit lamp photographs were taken to assess the severity of nuclear cataract (camera model SL-7E; Topcon Optical, Tokyo, Japan). Retroillumination photographs of the anterior and posterior lens were taken to assess the presence and severity of cortical and PSC cataracts (cataract camera model CT-R; Neitz, Tokyo, Japan). 

The severity of nuclear cataract on a 5-point scale was assessed by comparing subject photographs with a set of four standard photographs. The presence and severity of cortical cataracts were graded by placing over the Neitz photographs a circular grid divided into eight equal wedges and a central circle. Graders estimated the area percentage for each of these nine segments involved by cataract. The percentages were summed to give an estimate of the total lens area involved by cataract. PSC cataract was graded similarly. Photographs taken of pupils less than 4 mm in diameter were excluded from cortical cataract analyses. All photographs were graded by one of two masked graders. The κ values for intergrader reproducibility were 0.79 for nuclear (260 eyes), 0.78 for cortical (379 eyes), and 0.57 for PSC cataract (383 eyes). The quadratic weighted κ statistic (intraclass correlation coefficient) was used, because this measure correlates two graders on the same scale in reproducing the actual grade. ¹⁵ The values for nuclear and cortical cataract represent good reproducibility, whereas the value for PSC cataract is fair. 

Data for cortical and PSC cataracts were missing from approximately 3% of subjects because photographs were ungradable or were not taken. Because of intermittent camera malfunction (underexposure of some photographs), 1045 (29%) subjects did not have photographs suitable for nuclear cataract grading. These subjects did not differ in any important way from subjects with gradable photographs. ¹⁵  

We analyzed data from both eyes, using the generalized estimating equation method described in Zeger et al. ¹⁶ and Liang and Zeger. ¹⁷ Although usually bilateral, both refractive error and cataract are eye specific. The generalized estimating equation method allows use of data from both eyes while accounting for the correlation between the two eyes in a single subject. It affords greater precision of estimation and is less sensitive to missing data for some eyes. ¹⁸ Cataract was a dichotomized variable in all analyses. Cortical cataract was considered present if 5% or more of the lens was involved, whereas PSC cataract was considered present if any PSC opacity was graded. Nuclear cataract was considered present if graded level 3 or higher, in keeping with the definition of early cataract used previously in the Beaver Dam Eye Study ¹⁹ and in our prevalence report. ¹⁵  

In the multivariate analyses, we controlled for age, sex, hypertension, diabetes (history), smoking (current, past, or never), use of oral or inhaled steroids (ever or never), and level of sun-related skin damage (mild, moderate, or severe). Age was a continuous variable, whereas all other variables were categorical. Statistical software (Statistical Analysis System, ver. 6.12; SAS Institute, Cary, NC) was used for statistical analysis, including generalized estimating equation analyses. Odds ratios (OR) and 95% confidence intervals (CI) are presented. 

Results

We excluded 325 (4.5%) aphakic, pseudophakic, or enucleated eyes from the analyses. Eyes with missing or ungradable photographs accounted for other missing cataract data. Using data from both eyes and the definitions outlined, 2182 (47.4%) eyes had nuclear, 1211 (18.0%) eyes had cortical, and 265 had PSC (3.9%) cataract. Of the mixed types of cataract, 491 (10.9%) eyes had mixed cortical and nuclear cataract, 124 (2.7%) had mixed nuclear and PSC cataract, and 70 (1.0%) had mixed cortical and PSC cataract. All three cataract types coexisted in only 39 eyes (0.9%). A much smaller number of eyes had pure cataract types: Pure nuclear cataract was found in 1554 eyes (34.4%), pure cortical in 272 eyes (6.0%), and pure PSC in 52 eyes (1.2%). 

Current refraction data were available on 7243 (99.1%) eyes. Emmetropia was defined as a spherical equivalent refrac-tion (SER) between +1.0 and −1.0 D, myopia less than −1 D, and hyperopia more than +1 D. We divided myopia into three groups: Low myopia was defined as SER of −1 D or less to more than− 3.5 D, moderate myopia as SER of −3.5 D or less to more than −6 D, and high myopia as SER of −6 D or less. There were 2998 (41.4%) emmetropic, 3295 (45.5%) hyperopic, and 950 (13.1%) myopic eyes. Of eyes with myopia, 665 (70%) had low, 188 (19.8%) moderate, and 97 (10.2%) high myopia. 

Data were available on use of distance glasses in the past for 99.9% of subjects (7302 eyes) and age at first wearing distance glasses for 99.1% (6832 eyes). Of these, 32.1% had never worn distance glasses, 47.4% had begun wearing distance glasses after age 40 years, 9.9% between ages 21 and 39 years inclusive, and 10.6% before age 20 years. In using a history of wearing distance glasses measure as a proxy for myopia, we excluded from analyses eyes with a current hyperopic refraction. We considered that this would exclude most subjects who wore glasses for hyperopia at an early age. The age at which subjects reported first wearing distance glasses was divided into three groups: Age less than 20 years defined an early-onset myopia group; age 20 to 39 years, a later onset myopia group; and age 40 years or older, the group with latest onset. Subjects in the referent group had never worn distance glasses. 

We found an association between any current myopia and presence of nuclear cataract (OR 1.3; CI 1.0–1.6) after adjusting for other cataract risk factors. This weak association was present for all three levels of myopia but was only significant for moderate myopia, as shown in Table 1 . Any history of wearing distance glasses was significantly associated with presence of nuclear cataract. This was present before (OR 1.4; CI 1.1–1.7; Table 2 ) as well as after, excluding eyes with current hyperopic refraction (OR 1.3; CI 1.0–2.1; Table 3 ). However, after stratification by the age at which distance glasses were first worn, a statistically significant association was found only for persons who began wearing distance glasses after age 40 years (OR 1.3; CI 1.0–1.8; Tables 2 3 ). We performed further analyses, defining late nuclear cataract as level 4 or higher. Using this definition, current myopia had a stronger association with cataract. Any myopia was associated with late nuclear cataract (OR 2.3; CI 1.7–3.2) and a statistically significant relationship was found with lower degrees of myopia (−1 D to more than −6 D; OR 2.3; CI 1.7–3.2) as well as with high myopia (less than −6 D; OR 2.3;CI 1.1–4.5) after multivariate adjustment. 

Any current myopia was associated with presence of PSC cataract (OR 2.5; CI 1.6–4.1), before and after adjusting for the level of nuclear cataract. In the PSC cataract model, we controlled for the severity of nuclear cataract because of the known myopic shift in refraction caused by development of nuclear opacity ¹ (Table 1) . We found a weak negative association between PSC cataract and hyperopic compared with emmetropic eyes (OR 0.6; CI 0.4–0.9). A refraction-related trend was found for increasing risk of PSC cataract with increasing myopic refractive error. The magnitude of this association was OR 2.1 ( CI 1.2–3.8) for low myopia, OR 3.0 (CI 1.3–6.9) for moderate myopia, and OR 4.9 (CI 2.1–11.4) for high myopia. The association between a history of wearing distance glasses and PSC cataract was not statistically significant (OR 1.3; CI 0.8–2.1) in the multivariate analysis. However, after excluding eyes with current hyperopic refraction, this relationship was statistically significant (OR 2.6; CI 1.5–4.4; Table 3 ). The model was also adjusted for the severity of nuclear cataract. The strongest association was found in people with early-onset myopia (OR 3.9; CI 2.0–7.9), with a weaker association found with later onset myopia (OR 3.1; CI 1.3–7.3). 

A weak association was present between cortical cataract and hyperopia, after adjusting for other risk factors (OR 1.4; CI 1.1–1.7). High myopia was also associated with cortical cataract (OR 2.9; CI 1.4–6.0). No associations were found between history of wearing distance glasses and presence of cortical cataract. 

The Beaver Dam Eye Study compared people who wore distance glasses before age 20 years with those who wore them from age 40 years. When we made a comparison between these two groups, we found that people who wore distance glasses before age 20 years were more likely to have PSC cataract than those who began wearing distance glasses from age 40 years (Table 4) . Odds for the association with PSC cataract were greater for women (OR 3.1; CI 1.8–5.3) than men (OR 2.2; CI 1.0–4.8). Women who wore distance glasses from age 40 years were more likely to have nuclear cataract. There was thus an association between older age at wearing distance glasses and nuclear cataract in women. 

Discussion

The Blue Mountains Eye Study findings support the contention that long-standing myopia is an independent risk factor for age-related cataract, particularly PSC. 

Strengths of our study are its large sample size with use of data from both eyes, high response rate, control for other known cataract risk factors, and careful measurement of study variables using a standardized protocol and masked photographic grading to define the three main cataract types. A major limitation of these data is shared with all cross-sectional studies: We were unable to determine clearly the temporal relationship between the factors under study. We attempted, by using historical and examination data, to explore temporality. Further potential limitations are the possibility of inadequate control for important confounders (other cataract risk factors), despite the care taken to achieve this. Although there was a reduced number of nuclear cataract photographs available for analysis because of camera malfunction, there were no important differences between subjects with or without gradable photographs. ¹⁵  

As expected, we found an association between presence of nuclear cataract and any current myopia. ¹ Nuclear sclerosis increased the refractive index of the lens and so increased lens power. When examining the age at which distance glasses were first worn (excluding eyes with current hyperopic refraction), we found the association with presence of nuclear cataract was only statistically significant for people who first started wearing distance glasses from age 40 years. This suggests that it is the myopic shift caused by nuclear sclerosis that leads to the need for a distance glasses correction, as emphasized by Brown and Hill ¹ and Reeves et al. ³  

We found a strong association between a history of wearing distance glasses before age 20 years and the presence of PSC cataract, which was supported by the positive association found between current myopic refraction and PSC cataract. This self-report of a proxy for myopia, however, has its limitations. It relies on the subject’s memory and correct interpretation of the question by the subject. However, it seems likely that a subject’s recollection of wearing prescription glasses may be more accurate than a recollection of having been told that cataract was present. ²⁰ Further, in using this history as a proxy for myopia, we excluded people with a current refraction of more than +1 D, because hyperopic subjects could also have worn distance glasses from a young age. Although the findings were similar when these subjects were included in analyses (Table 2) , excluding people with hyperopia strengthened the odds for PSC cataract, particularly for the early-onset group (Table 3) . These findings suggest that early-onset myopia may be a risk factor for development of PSC cataract in later life. 

Could the association found between myopia and PSC cataract have been confounded by difficulty in grading PSC in the presence of advanced nuclear cataract? It is not possible to exclude this as a possibility, but it seems unlikely to have had a major effect on our findings because of the relatively small number of subjects with the highest nuclear grade. ¹⁵  

Low myopia has not been previously implicated in the development of cortical cataract, and we also found no association. Our data, however, indicate that high myopia is associated with all three types of age-related cataract, particularly PSC. This finding is in keeping with the long-accepted notion that high myopia is an important risk factor for cataract. 

We had the opportunity to compare our results with Beaver Dam findings. The two studies used similar techniques, and our grading protocols were the same. Overall, the patterns of association found are similar. Both studies found that wearing distance glasses before age 20 years was associated with PSC cataract and that wearing myopic distance correction beginning in older age was associated with nuclear cataract. 

Mechanisms for the association between myopia and cataract are not known. It has been suggested that there may be a biochemical basis for cataractogenesis in myopic patients with retinal lipid peroxidation playing a role. ²¹ Our results showed a trend for an increasing association between PSC cataract and myopic refraction that extended from hyperopia to high myopia. Could the relationship with PSC cataract be based on axial length? Increasing axial length may tend to deprive the posterior lens of nutrition. To our knowledge, no study to date has studied axial length and cataract prevalence in a population. Further work in this area is warranted. The true refractive status of our study population remains unknown. Although we have measures of current refraction, greater clarity would have been provided by having axial length and keratometry measurements to differentiate axial from index myopia. 

A mechanical cause for the association between myopia and cataract was suggested by Weale. ² He argued that the lens matrix in myopia may be subject to greater pressure from the lens capsule than in other refractive states because of the reduced need for myopic subjects to accommodate. Weale further speculated that overcorrection of myopia in the late 20s may decrease the excess risk of cataract. ²  

Our findings may have important implications. Low myopia and cataract are both common problems worldwide, and our study also provides some evidence that the age-specific prevalence of myopia may be increasing. ²² Much research targets modifiable cataract risk factors to relieve the future public health burden of cataract. To date, however, there is no proven therapy that reduces development or progression of myopia. 

In summary, this cross-sectional study has examined several refractive parameters in attempting to build a picture of the temporal relationship between myopia and age-related cataract. A statistically significant relationship was found between myopia and PSC cataract, with a gradient from hyperopia to high myopia, which could be based on axial length. Further work is indicated to examine possible mechanisms for the relationship. 

 Supported by the Australian National Health and Medical Research Council and the Save Sight Institute, University of Sydney.

 Submitted for publication January 11, 1999; revised June 22, 1999; accepted July 6, 1999.

 Commercial relationships policy: N.

Table 1.

 

 

Adjusted Odds Ratios for Associations between Current Refraction and Types of Age-Related Cataract

Table 1.

 

Adjusted Odds Ratios for Associations between Current Refraction and Types of Age-Related Cataract

Type of Cataract	Current Refraction
		Hyperopia	Emmetropia	Any Myopia	Low Myopia	Medium Myopia	High Myopia
Eyes with PSC cataract
Model adjusted for age and sex	0.7 (0.5–1.0)	1.0 (referent)	2.6 (1.8–3.7)	2.1 (1.4–3.2)	3.0 (1.6–5.7)	5.5 (2.8–10.9)
Multivariate model, †	0.6 (0.4–0.9)	1.0 (referent)	2.5 (1.6–4.1)	2.1 (1.2–3.8)	3.0 (1.3–6.9)	4.9 (2.1–11.4)
Number of cases	99	88	77	45	18	14
Total number of eyes (%)	3104 (3.2)	2785 (3.2)	831 (9.3)	561 (8.0)	177 (10.2)	93 (15.1)
Eyes with nuclear cataract
Model adjusted for age and sex	1.5 (1.3–1.7)	1.0 (referent)	1.3 (1.0–1.6)	1.2 (0.9–1.5)	1.5 (1.0–2.3)	1.6 (0.9–2.7)
Multivariate model*	1.5 (1.3–1.8)	1.0 (referent)	1.3 (1.0–1.6)	1.2 (0.9–1.6)	1.5 (1.0–2.3)	1.4 (0.8–2.4)
Number of cases	1225	691	251	156	64	31
Total number of eyes (%)	2131 (57.5)	1902 (36.3)	559 (44.9)	362 (43.1)	130 (49.2)	67 (46.3)
Eyes with cortical cataract
Model adjusted for age and sex	1.2 (1.0–1.4)	1.0 (referent)	1.1 (0.9–1.4)	1.0 (0.8–0.4)	1.2 (0.7–1.9)	1.7 (0.9–3.3)
Multivariate model, †	1.4 (1.1–1.7)	1.0 (referent)	1.2 (0.8–1.6)	1.0 (0.7–1.5)	1.1 (0.6–2.0)	2.9 (1.4–6.0)
Number of cases	674	387	140	94	26	20
Total number of eyes (%)	3091 (21.8)	2771 (14.0)	825 (17.0)	557 (16.9)	175 (14.9)	93 (20.5)

 Low myopia, −1 to more than −3.5 D; medium myopia, −3.5 to more than −6 D; high myopia, −6 D or less. Data in parentheses beside ORs are 95% CIs.

*  Adjusted for age, sex, smoking, hypertension, diabetes, use of oral or inhaled steroids, and examiner-assessed sun-related skin damage.

†  Also adjusted for nuclear cataract grade.

Table 2.

 

 

Adjusted Odds Ratios for Associations between the Age at Which Distance Glasses Were First Worn and Types of Age-Related Cataract

Table 2.

 

Adjusted Odds Ratios for Associations between the Age at Which Distance Glasses Were First Worn and Types of Age-Related Cataract

Type of Cataract	Distance Glasses Worn			Age at Which Distance Glasses First Worn
		Never	Ever	40 or older	20–39	0–19
Eyes with PSC cataract
Model adjusted for age and sex	1.0 (referent)	1.3 (0.9–1.9)	1.1 (0.7–1.6)	1.5 (0.9–2.6)	2.7 (1.7–4.2)
Multivariate model, †	1.0 (referent)	1.3 (0.8–2.1)	1.1 (0.7–1.9)	1.4 (0.7–3.1)	2.5 (1.3–4.7)
Number of cases	58	206	108	28	51
Total number of eyes (%)	2070 (2.8)	4670 (4.4)	2994 (3.6)	608 (4.6)	672 (7.6)
Eyes with nuclear cataract
Model adjusted for age and sex	1.0 (referent)	1.5 (1.2–1.8)	1.5 (1.2–1.9)	1.4 (1.0–1.9)	1.2 (0.9–1.7)
Multivariate model*	1.0 (referent)	1.4 (1.1–1.7)	1.5 (1.2–1.8)	1.3 (0.9–1.9)	1.1 (0.8–1.5)
Number of cases	500	1680	1097	192	195
Total number of eyes (%)	1400 (35.7)	3206 (52.4)	2044 (53.7)	415 (46.3)	457 (42.7)
Eyes with cortical cataract
Model adjusted for age and sex	1.0 (referent)	0.7 (0.6–0.8)	0.9 (0.8–1.2)	1.0 (0.7–1.4)	1.0 (0.7–1.3)
Multivariate model, †	1.0 (referent)	0.9 (0.7–1.1)	1.1 (0.8–1.4)	1.5 (1.0–2.2)	1.2 (0.9–1.9)
Number of cases	305	904	569	107	112
Total number of eyes (%)	2059 (14.8)	4648 (19.4)	2977 (19.1)	607 (17.6)	670 (16.7)

 Data in parentheses beside ORs are 95% CIs.

*  Adjusted for age, sex, smoking, hypertension, diabetes, use of oral or inhaled steroids, and examiner-assessed sun-related skin damage.

†  Also adjusted for nuclear cataract grade.

Table 3.

 

 

Adjusted Odds Ratios for Associations between the Age at Which Distance Glasses Were First Worn and Types of Age-Related Cataract

Table 3.

 

Adjusted Odds Ratios for Associations between the Age at Which Distance Glasses Were First Worn and Types of Age-Related Cataract

Type of Cataract	Distance Glasses Worn			Age at Which Distance Glasses First Worn
		Never	Ever	40 or older	20–39	0–19
Eyes with PSC cataract
Model adjusted for age and sex	1.0 (referent)	2.4 (1.6–3.7)	1.8 (1.1–2.9)	2.7 (1.4–5.1)	4.4 (2.6–7.4)
Multivariate model, †	1.0 (referent)	2.6 (1.5–4.4)	2.0 (1.1–3.6)	3.1 (1.3–7.3)	3.9 (2.0–7.9)
Number of cases	35	130	51	20	46
Total number of eyes (%)	1569 (2.2)	2069 (6.3)	1061 (4.8)	360 (5.6)	441 (10.4)
Eyes with nuclear cataract
Model adjusted for age and sex	1.0 (referent)	1.3 (0.8–2.1)	1.3 (1.0–1.8)	1.2 (0.8–1.8)	1.3 (0.9–1.9)
Multivariate model*	1.0 (referent)	1.3 (1.0–2.1)	1.3 (1.0–1.8)	1.2 (0.8–1.9)	1.2 (0.8–1.8)
Number of cases	348	608	328	88	129
Total number of eyes (%)	1085 (32.1)	1391 (43.7)	712 (46.1)	243 (36.2)	327 (39.4)
Eyes with cortical cataract
Model adjusted for age and sex	1.0 (referent)	1.0 (0.8–1.3)	0.9 (0.7–1.2)	1.3 (0.8–1.9)	1.1 (0.7–1.5)
Multivariate model, †	1.0 (referent)	1.1 (0.8–1.5)	0.9 (0.6–1.2)	1.6 (1.0–2.8)	1.2 (0.8–1.9)
Number of cases	205	331	161	57	73
Total number of eyes (%)	1561 (13.1)	2057 (16.1)	1052 (15.3)	359 (15.9)	486 (15.0)

 Data in parentheses beside ORs are 95% CIs. Subjects with current hyperopic refraction were excluded.

*  Adjusted for age, sex, smoking, hypertension, diabetes, use of oral or inhaled steroids, and examiner-assessed sun-related skin damage.

†  Also adjusted for nuclear cataract grade.

Table 4.

 

 

Comparison of Present and Beaver Dam Eye Study Findings

Table 4.

 

Comparison of Present and Beaver Dam Eye Study Findings

Type of Cataract	Men			Women
		OR	95% CI	OR	95% CI
Eyes with PSC cataract
Model adjusted for age	1.8 (1.1)	1.9–3.6 (0.8–1.4)	2.5 (1.2)	1.5–4.0 (1.0–1.5)
Multivariate model*	2.2	1.0–4.8	3.1 (1.4)	1.8–5.3 (1.0–2.1)
Eyes with nuclear cataract
Model adjusted for age	1.0 (0.8)	0.5–1.5 (0.6–1.0)	0.7 (1.0)	0.5–1.0 (0.9–1.2)
Multivariate model*	0.9 (0.8)	0.6–1.5 (0.6–1.0)	0.7	0.5–1.0
Eyes with cortical cataract
Model adjusted for age	0.8 (0.7)	0.5–1.3 (0.5–1.0)	1.2 (1.1)	0.8–1.7 (0.9–1.4)
Multivariate model*	0.9 (0.7)	0.6–1.5 (0.5–1.0)	1.2	0.8–1.8

 Adjusted odds ratios for associations between age at which distance glasses were first worn and types of age-related cataract; Beaver Dam findings in parentheses where available. ¹⁰ Data are age at which distance glasses were first worn, less than 20 years of age versus 40 or more years. Data in parentheses are 95% CIs.

*  Adjusted for age, sex, smoking, hypertension, diabetes, use of oral or inhaled steroids, and examiner-assessed sun-related skin damage.