Carolyn M. Machan

Age-Related Cataract Is Associated with Type 2 Diabetes and Statin Use

Purpose. Diabetes has been shown to be a risk factor for age-related (AR) cataract. As statins (HMG-CoA reductase inhibitors) are now commonly prescribed for patients with type 2 diabetes, their impact on AR cataract prevalence should be considered. This study determines associations between AR cataract, type 2 diabetes, and reported statin use in a large optometric clinic population. Methods. In all, 6397 patient files (ages <1–93 years) were reviewed. Overall prevalence of statin use was calculated for patients with type 2 diabetes (n = 452) and without diabetes (n = 5884). Multivariable logistic regression analysis for AR cataract was performed controlling for patient sex, smoking, high blood pressure, type 2 diabetes, and statin use. Results. The prevalence of statin use (in patients aged >38 years) was 56% for those with type 2 diabetes and 16% for those without diabetes. Type 2 diabetes was significantly associated with nuclear sclerosis (OR = 1.62, 1.14–2.29) and cortical cataract (OR = 1.37, 1.02–1.83). Statin use was associated with nuclear sclerosis (OR = 1.48, 1.09–2.00) and posterior subcapsular cataract (OR = 1.48, 1.07–2.04). The 50% probability of cataract in statin users occurred at age 51.7 and 54.9 years in patients with type 2 diabetes and without diabetes, respectively. In non-statin users, it was significantly later at age 55.1 and 57.3 years for patients with type 2 diabetes and without diabetes, respectively (p < 0.001). Conclusions. In this population, statin use was substantially higher in patients with type 2 diabetes and was associated with AR cataracts. Further long-term study is warranted to recommend monitoring of crystalline lenses in patients with type 2 diabetes benefiting from statins.

Increase in myopia prevalence in clinic-based populations across a century.

Purpose The study’s aim was to report prevalence estimates and age-related trends in refractive error in a clinic-based series and compare them to results from studies of a similar nature conducted since 1892. Methods Refractive error, patient age, and sex were collected from the files of all patients seen at the University of Waterloo School of Optometry and Vision Science clinic between January 2007 and January 2008. Patients were categorized as having myopia (<−0.5D mean ocular refraction [MOR]), hyperopia (>0.5D MOR), emmetropia, astigmatism (<−0.5D), and/or anisometropia (>1.0D difference between eyes). The prevalence of all refractive components was determined overall and in 1- and 5-year age groups, and then compared to data from older clinic-based studies. Refractive trends over time were noted. The prevalence of myopia and hyperopia were compared to older studies. Results The lowest prevalence of myopia was 5% at 0 to 5 years of age, after which it increased to 72% at 20 to 30 years of age and then decreased to 22% in patients older than 70 years. A myopic peak occurred at 24 years of age. The prevalence of hyperopia followed opposite trends with a minimum prevalence of 6% at 25 to 30 years of age. Peaks in emmetropia prevalence were 55% at 5 to 10 years of age and 37% at 45 to 50 years of age. The prevalence of astigmatism and anisometropia increased with age. The Waterloo Eye Study showed a higher prevalence of myopia across all ages compared to the older studies with a peak prevalence of 72% compared to 21% in the oldest (Herrnheiser) study from 1892. Conclusions In the last 100 years, there appears to have been a myopic shift in clinic-based populations and myopia prevalence appears to follow a predictable pattern with age.

Waterloo Eye Study: data abstraction and population representation.

Purpose. To determine data quality in the Waterloo Eye Study (WatES) and compare the WatES age/sex distribution to the general population. Methods. Six thousand three hundred ninety-seven clinic files were reviewed at the University of Waterloo, School of Optometry. Abstracted information included patient age, sex, presenting chief complaint, entering spectacle prescription, refraction, binocular vision, and disease data. Mean age and age distributions were determined for the entire study group and both sexes. These results were compared with Statistics Canada (2006) estimates and information on Canadian optometric practices. Inter- and intraabstractor reliability was determined through double entry of 425 and 50 files, respectively; the Cohen kappa statistic (K) was calculated for qualitative data and the intraclass correlation coefficient (ICC) for quantitative data. Availability of data within the files was determined through missing data rates. Results. The age of the patients in the WatES ranged from 0.2 to 93.9 years (mean age, 42.5 years), with all age groups younger than 85 years well represented. Females comprised 54.1% and males 45.9% of the study group. There were more older patients (>65 years) and younger patients (<10 years) than in the population at large. K values were highest for demographic information (e.g., sex, 0.96) and averaged slightly less for most clinical data requiring some abstractor interpretation (0.71 to 1.00). The two lowest interabstractor values, migraine (0.41) and smoking (0.26), had low reporting frequencies and definition ambiguity between abstractors. Intraclass correlation coefficient values were >0.90 for all but one continuous data type. Missing data rates were <2% for all but near phoria, which was 7.4%. Conclusions. The WatES database includes patients from all age groups and both sexes. It provides a fair representation of optometric patients in Canada. Its large sample size, good interabstractor repeatability, and low missing data rates demonstrates sufficient data quality for future analysis.

Binocular Vision and Eye Movement Disorders in Older Adults

PURPOSE To determine the prevalence of binocular vision (BV) and eye movement disorders in a clinic population of older adults. METHODS Retrospective clinic data were abstracted from files of 500 older patients seen at the University of Waterloo Optometry Clinic over a 1-year period. Stratified sampling gave equal numbers of patients in the 60 to 69, 70 to 79, and 80+ age groups. Data included age, general and ocular history and symptoms, use of antidepressants, a habit of smoking, refraction, visual acuity, BV and eye movement status for the most recent full oculo-visual assessment, and an assessment 10 years prior. The prevalence of any BV or eye movement abnormal test (AT) result, defined as a test result outside the normal range, was determined. This included strabismus (any) or phoria; incomitancy; poor pursuits; and remote near point of convergence (NPC). The prevalence of significant BV disorders (diagnostic entities, i.e., a clinical condition that may need treatment and may have functional implications) was also determined. RESULTS The prevalence of any BV or eye movement at was 41%, 44%, and 51% in the 60 to 69, 70 to 79, and 80+ age groups, respectively. These figures were lower for 10 years earlier: 31%, 36%, and 40% for ages 50 to 59, 60 to 69, and 70+, respectively. The prevalence of any BV or eye movement disorder was 27%, 30%, and 38% for the three age groups and 17%, 19%, and 24% for 10 years prior. Age and use of antidepressants most commonly predicted BV or eye movement AT or disorder. CONCLUSIONS BV disorders are common among older adults.

Prescribing for hyperopia in childhood and teenage by academic optometrists.

Purpose. The purpose of this study was to examine the prescribing patterns of academic optometrists for infants, children, and teenagers with hyperopia and the factors that affected the decision to prescribe. A comparison was made to published guidelines for prescribing for hyperopia in children. Methods. The Waterloo Eye Study (WatES) database is a database of all patients attending the Primary Care Clinic or the Pediatric Clinic at the School of Optometry, University of Waterloo, between February 2007 and January 2008. Records for 698 patients aged from birth to 19 years with hyperopia but without strabismus or significant anisometropia were extracted. They were analyzed to determine the factors that predicted whether a child was prescribed spectacles and the 50% prescribing points for hyperopia and astigmatism according to age. Results. Univariate analysis showed that the level of hyperopia, astigmatism, age, distance, and near phoria and presence of symptoms were associated with the prescription of spectacles (p < 0.05). Multivariate analysis showed that the prescription of spectacles was predicted by age, highest sphere (either right or left eye), highest cylinder, the presence of symptoms, and distance phoria. Among 0 to 3 year olds, all the children with 5 D or more of hyperopia had been prescribed spectacles. Among the 4 to 6 year olds, this point was 3.25 D; and for the 7 to 19 year olds, it was 2.25 D. The levels at which 50% of the population had been prescribed spectacles was 3.7, 1.8, and 1.1 D for the 0 to 3 year olds, 4 to 6 year olds, and 7 to 19 year olds, respectively. There was frequently a difference between the refraction and the prescription such that the younger children, in particular, were often under corrected for both hyperopia and astigmatism. Conclusions. The optometrists in this academic setting appear to follow the available optometric guidelines for prescribing for hyperopia. They tend to prescribe for lower levels of hyperopia than U.S. ophthalmologists.

Modeling the prevalence of age-related cataract: Waterloo eye study.

Purpose. To report on the prevalence of age-related (AR) cataract in an optometric clinic population including male and female subgroups. Methods. Retrospective patient file data reviewed for the Waterloo Eye Study database included age, sex, date of lens extraction (LE), and presence of AR cataract [nuclear sclerosis (NS), cortical cataracts (CC), posterior subcapsular (PSC) or associated LE]. Prevalence (%) was calculated for overall AR cataract, NS, CC, PSC, and bilateral LE for all Waterloo Eye Study patients. Logistic regression analysis was used to create age functions for overall AR prevalence and for significant differences in cataract types for males and females. The distribution of homogeneous and mixed cataract and mean age of first LE were determined for males and females. Results. The prevalence of all AR, NS, CC, PSC, and bilateral LE was 35.3, 28.8, 9.9, 3.6, and 14.0%, respectively. Being female was associated with an increased prevalence of CC (odds ratio = 1.54, 95% confidence interval, 1.27 to 1.88) and bilateral LE (odds ratio = 1.41, 95% confidence interval, 1.09 to 1.84). Females reached 50% prevalence earlier than men for CC (76.7 vs. 82.6 years, p < 0.05) and bilateral LE (84.6 vs. 90.5 years, p < 0.05). Males had an earlier age of first LE than females (70.4 vs. 73.2 years; p < 0.01). Conclusions. Logistic regression modeling indicates that being female in this optometric clinic population was associated with an increased prevalence of CC, mixed cataract, surgical intervention, and later age of first LE. These data are important for public health planning.

Value of Routine Eye Examinations in Asymptomatic Patients.

Purpose To determine if routine eye examinations in asymptomatic patients result in spectacle prescription change, new critical diagnosis, or new management of existing conditions. We also investigate whether age and time between assessments (assessment interval) impact detection rates. Methods The Waterloo Eye Study (WatES) database was created from a retrospective file review of 6397 patients seen at the University of Waterloo Optometry Clinic. Significant changes since the previous assessment (significant change) were defined as a change in spectacle prescription, presence of a new critical diagnosis, or a new management. Significant change, assessment interval, and age were extracted from the database for all asymptomatic patients presenting for a routine eye examination. The frequency of patients with significant change and the median assessment interval were determined for different age groups. Results Of 2656 asymptomatic patients, 1078 (41%) patients had spectacle prescription changes, 434 (16%) patients had new critical diagnoses, 809 (31%) patients had new managements, and 1535 (58%) patients had at least one of these (significant change). Median assessment intervals were 2.9 and 2.8 years for age groups 40 to <65 years and 20 to <40 years, respectively, approximately 1.5 years for patients 7 to <20, and between 1 and 1.5 years for patients <7 or >64. Controlling for assessment interval and sex, increasing age was associated with having a significant change (OR = 1.03, 95% CI 1.029–1.037). Similarly, controlling for age and sex, increased assessment interval was associated with having a significant change (OR = 1.06, 95% CI 1.02–1.11). Conclusions In asymptomatic patients, comprehensive routine optometric eye examinations detect a significant number of new eye conditions and/or result in management changes. The number detected increases with age and assessment interval.

Eye examinations improve visual acuity across ages

OBJECTIVE To investigate changes in distance best corrected visual acuity (BCVA) relative to presenting visual acuity (PVA) as a function of age and the number of years between eye examinations. DESIGN Retrospective cross-sectional study. PARTICIPANTS 6397 patient files at a large Canadian Optometric Clinic. METHODS A retrospective file review of patients aged 4 to 93 years from the University of Waterloo, Optometry Clinic was conducted. Mean decimal PVA values were calculated for all patients grouped by year of age, and a function was fit to these data using nonlinear regression. The same was done for BCVA and the functions were compared. In addition, the mean logMAR difference between PVA and BCVA was determined for patients grouped by the length of time between the study visual assessment and their previous visual assessment independent of patient age. RESULTS Right and left eye functions were not significantly different from each other for either PVA or BCVA. BCVA functions were significantly greater than PVA functions for both right (F[3174] = 194.7, p < 0.0001) and left (F[3174] = 206.0, p < 0.0001) eyes. PVA differed (≥1 line) from BCVA in at least 1 eye in 70% (n = 4054) of patients. The difference between BCVA and PVA increased as the length of time between assessments increased from 0.075 logMAR for <1 year to 0.107 logMAR for ≥5 years. CONCLUSIONS Refractive testing resulted in an improvement in BCVA over PVA in the majority of patients, over a wide range of ages.

Refractive error magnitude and variability: Relation to age

Purpose To investigate mean ocular refraction (MOR) and astigmatism, over the human age range and compare severity of refractive error to earlier studies from clinical populations having large age ranges. Methods For this descriptive study patient age, refractive error and history of surgery affecting refraction were abstracted from the Waterloo Eye Study database (WatES). Average MOR, standard deviation of MOR and astigmatism were assessed in relation to age. Refractive distributions for developmental age groups were determined. MOR standard deviation relative to average MOR was evaluated. Data from earlier clinically based studies with similar age ranges were compared to WatES. Results Right eye refractive errors were available for 5933 patients with no history of surgery affecting refraction. Average MOR varied with age. Children <1 yr of age were the most hyperopic (+1.79 D) and the highest magnitude of myopia was found at 27yrs (−2.86 D). MOR distributions were leptokurtic, and negatively skewed. The mode varied with age group. MOR variability increased with increasing myopia. Average astigmatism increased gradually to age 60 after which it increased at a faster rate. By 85+ years it was 1.25 D. J0 power vector became increasingly negative with age. J45 power vector values remained close to zero but variability increased at approximately 70 years. In relation to comparable earlier studies, WatES data were most myopic. Conclusions Mean ocular refraction and refractive error distribution vary with age. The highest magnitude of myopia is found in young adults. Similar to prevalence, the severity of myopia also appears to have increased since 1931.

Modifications made to the refractive result when prescribing spectacles.

Purpose. The purpose of this study was to determine how optometric practitioners modify the subjective refractive result when prescribing spectacles. Methods. Refractive data were gathered for patient visits at the School of Optometry, University of Waterloo, between January 2007 and January 2008. The entering prescription, subjective refraction, and exiting prescription were analyzed from 5001 records for patients aged ≥7 years. Results. The refraction was modified to create the prescription in at least one eye in 45% of cases; specifically, 27% of cases for the sphere power, 18% for the cylinder power, 25% for the cylinder axis, and 21% for the add. Significant differences, defined as ≥0.50 D in sphere, cylinder, or add power or a change in axis of 15° for cylinders <1 D, 10° for cylinders between 1 and ≤2, and 5° for cylinders >2, were made in at least one eye in 17% of cases; specifically 9% of cases for the sphere power, 6% for the cylinder power, 6% for the cylinder axis, and 5% for the add. Spheres were more likely to be modified in the minus direction (weaker plus and stronger minus power) (18 vs. 11%), cylinder powers reduced (14 vs. 5%), and adds increased in power (12 vs. 8%). Modifications to create the exiting prescription were made to be closer or the same as the entering prescription 97% of the time. However, modifications were such that the entering prescription was duplicated exactly only 0.7% of the time. Conclusions. Optometric practitioners routinely modify the subjective refraction to create the prescription. Small modifications are common, whereas larger modifications are used more sparingly. Because there is a significant amount of clinical judgment involved in determining the refractive prescription, reliance on automated or subjective refraction alone would not be prudent.