The impact of cataract, cataract types, and cataract grades on vision-specific functioning using Rasch analysis

Long Term Visual Outcomes of an Extended Macular Vision IOL in Eyes with Macular Disease and Visually Insignificant Cataract

Purpose

To determine long-term efficacy and safety of an extended macular vision intraocular lens (IOL) implanted in patients with dry age-related macular degeneration (AMD) and visually insignificant cataracts.

Design

Retrospective observational case series.

Setting

MicroChirurgia Oculare, Italy.

Methods

A retrospective case series of patients with dry AMD and visually insignificant cataracts undergoing phacoemulsification and implantation of an extended macular vision IOL designed to optimize image quality up to 10° from the foveal center (EyeMax Mono, Sharpview Ophthalmology, London, UK). Criteria for implantation were visually insignificant cataract (NC1 according to LOCS III classification) with dry age-related macular degeneration. Hypermetropia was targeted in most eyes to provide magnification when corrected with spectacles. Primary outcome measures were changes in corrected distant and secondary outcome measures included near visual acuity (CDVA and CNVA, respectively) between baseline and latest follow-up and safety outcomes.

Results

113 eyes of 86 patients (mean age 70.3±7.9 years) were included (mean follow-up: 48.3±25.1 months). Mean CDVA improved by 0.22 logMAR (11 ETDRS letters), from 0.53±0.4 to 0.31±0.3 (n=113, p<0.001). Similarly, mean CNVA improved by 0.08 logMAR (4 ETDRS letters), from 0.45±0.2 to 0.37±0.2 (n=77, p<0.001). Eleven eyes had AMD with extensive atrophy, and their mean CDVA improved by 0.32 logMAR (16 ETDRS letters). Three eyes (2.7%) experienced loss of more than one line in logMAR CDVA and four eyes (5.2%) experienced loss of more than one line in logMAR CNVA. No complications or instances of IOL exchange were reported.

Conclusion

Visual improvement in eyes with visually insignificant cataract and AMD who underwent phacoemulsification and were implanted with EyeMax Mono IOL appears to be influenced by the IOL optical design. Vision enhancement in eyes with visually insignificant cataracts underscores the IOL's ability to optimize use of healthy retinal areas. Prospective studies with control groups are needed to confirm these findings.

Polydopamine based photothermal/photodynamic synchronous coating modified intraocular lens for efficient and safer posterior capsule opacification prevention

Posterior capsule opacification (PCO), as one of the most common late complications after intraocular lens (IOL) implantation in cataract surgery, seriously affects patients' postoperative vision and surgical satisfaction, and can only be treated by laser incision of the posterior capsule. Although drug eluting coating modification have been proved to inhibit PCO effectively, the complicated coating methods and the potential toxicity of the antiproliferative drugs hinders its actual application. In this study, an indocyanine green (ICG) loaded polydopamine (PDA) coating modified IOL (IP-IOL) was designed to prevented PCO. In vitro and in vivo studies have shown that IP-IOL can effectively eliminate lens epithelial cells and significantly reduce the degree of PCO. At the same time, it still has good imaging quality and optical properties. Furthermore, both the near-infrared irradiation and ICG loaded PDA coating modified IOLs have proved to possess high biological safety to eyes. Thus, with easy preparation and safer near-infrared irradiated photothermal/photodynamic synchronous properties, such ICG loaded PDA coating provides an effective yet easier and safer PCO prevention after IOL implantation.

Correlation between color vision, visual acuity, contrast sensitivity and photostress recovery in the visually impaired: a cross-sectional study

Background

To investigate the correlation of colour vision, visual acuity, contrast sensitivity, and photostress recovery time test scores in visually impaired patients.

Materials and methods

A total of 133 subjects were enroled and 133 eyes were examined. The pathological group consisted of 76 (57.1%) males with an average age of 68.0 (SD=13.2) and 57 (42.9%) females, with an average age of 68.1 (SD=15.2), Mann-Whitney U test was used to evaluate the differences in K-colour tests, HRR, visual acuity, Contrast Sensitivity test and photostress recovery time test between two different groups of severity.

Results

Correlations were found among colour vision tests, visual acuity, contrast sensitivity, and photostress recovery time scores in eyes with age-related macular degeneration, with diabetic retinopathy, with optic nerve diseases, and various other retinal diseases (P<0.05). In patients with moderate-visual impairments.

Conclusions

The colour vision test scores correlate with the scores of visual acuity, contrast sensitivity, and photostess recovery time test. It may be a useful clinical surrogate for functional vision.

Immediately sequential bilateral cataract surgery

PURPOSE OF REVIEW

This review aims to clarify the advantages and disadvantages of immediately sequential bilateral cataract surgery (ISBCS) based on recent studies, illustrate the safety of this approach, the cost-effectiveness, and present the importance of inclusion protocols for the best results.

RECENT FINDINGS

In recent studies, the authors found no evidence of an increased risk of bilateral devastating complications such as endophthalmitis with ISBCS based on descriptive evidence compared to delayed sequential bilateral cataract surgery (DSBCS). Furthermore, recent studies on cost analyses showed that ISBCS resulted in fewer costs and significant cost savings to third-party payers, patients, and society compared to DSBCS.

SUMMARY

The ISBCS surgical approach decreases hospital visits, reduces costs, and provides rapid visual rehabilitation and neuro adaptation. The risk of bilateral simultaneous complications is now recognized to be very rare with intracameral antibiotics and compliance with correct protocols. With new generations of optical biometry and lens calculation formulas, refractive surprises are occasional for normal eyes. However, refractive surprise is controversial, especially in the implantation of presbyopia correction intra-ocular lenses, which must be evaluated carefully in the ISBCS approach.

Potential of GJA8 gene variants in predicting age-related cataract: A comparison of supervised machine learning methods

Cataracts are the problems associated with the crystallins proteins of the eye lens. Any perturbation in the conformity of these proteins results in a cataract. Age-related cataract is the most common type among all cataracts as it accounts for almost 80% of cases of senile blindness worldwide. This research study was performed to predict the role of single nucleotide polymorphisms (SNPs) of the GJA8 gene with age-related cataracts in 718 subjects (400 age-related cataract patients and 318 healthy individuals). A comparison of supervised machine learning classification algorithm including logistic regression (LR), random forest (RF) and Artificial Neural Network (ANN) were presented to predict the age-related cataracts. The results indicated that LR is the best for predicting age-related cataracts. This successfully developed model after accounting different genetic and demographic factors to predict cataracts will help in effective disease management and decision-making medical practitioner and experts.

Cataracts

94 million people are blind or visually impaired globally, and cataract is the most common cause of blindness worldwide. However, most cases of blindness are avoidable. Cataract is associated with decreased quality of life and reduced life expectancy. Most cases of cataract occur after birth and share ageing and oxidative stress as primary causes, although several non-modifiable and modifiable risk factors can accelerate cataract formation. In most patients, phacoemulsification with intraocular lens implantation is the preferred treatment and is highly cost-effective. There has been an increase in the use of comprehensive cataract surgical services, including diagnoses, treatment referrals, and rehabilitation. However, global inequity in surgical service quality is still a limitation. Implementation of preoperative risk assessment, risk reduction strategies, and new surgical technologies have made cataract surgery possible at an earlier stage of cataract severity with the expectation of good refractive outcomes. The main challenge is making the service that is currently available to some patients accessible to all by use of universal health coverage.

Immediate sequential bilateral surgery versus delayed sequential bilateral surgery for cataracts

BACKGROUND

Age-related cataract affects both eyes in most cases. Most people undergo cataract surgery in both eyes on separate days, referred to as delayed sequential bilateral cataract surgery (DSBCS). An alternative procedure involves operating on both eyes on the same day, but as two separate procedures, known as immediate sequential bilateral cataract surgery (ISBCS). Potential advantages of ISBCS include fewer hospital visits for the patient, faster visual recovery, and lower healthcare costs. Nevertheless, concerns exist about possible bilateral, postoperative, sight-threatening adverse effects with ISBCS. Therefore, there is a clear need for evaluating evidence regarding the safety, effectiveness, and cost-effectiveness of ISBCS versus DSBCS.

OBJECTIVES

To assess the safety of ISBCS compared to DSBCS in people with bilateral age-related cataracts and to summarise current evidence for the incremental resource use, utilities, costs, and cost-effectiveness associated with the use of ISBCS compared to DSBCS in people with bilateral age-related cataracts (primary objectives). The secondary objective was to assess visual and patient-reported outcomes of ISBCS compared to DSBCS in people with bilateral age-related cataracts.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register; 2021, Issue 5); Ovid MEDLINE; Ovid Embase; the ISRCTN registry; ClinicalTrials.gov; the WHO ICTRP; and DARE and NHS EED on the CRD Database on 11 May 2021. There were no language restrictions. We limited the searches to a date range of 2007 onwards.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) to assess complications, refractive outcomes, best-corrected distance visual acuity (BCDVA) and patient-reported outcome measures (PROMs) with ISBCS compared to DSBCS. We included non-randomised (NRSs), prospective, and retrospective cohort studies comparing ISBCS and DSBCS for safety assessment, because of the rare incidence of important adverse events. To assess cost-effectiveness of ISBCS compared to DSBCS, we included both full and partial economic evaluations, and both trial-based and model-based economic evaluations.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures and assessed risk of bias for NRSs using the ROBINS-I tool. For cost-evaluations, we used the CHEC-list, the CHEERS-checklist, and the NICE-checklist to investigate risk of bias. We assessed the certainty of evidence with the GRADE tool. We reported results for economic evaluations narratively.

MAIN RESULTS

We included 14 studies in the review; two RCTs, seven NRSs, and six economic evaluations (one study was both an NRS and economic evaluation). The studies reported on 276,260 participants (7384 for ISBCS and 268,876 for DSBCS) and were conducted in Canada, the Czech Republic, Finland, Iran, (South) Korea, Spain (Canary Islands), Sweden, the UK, and the USA. Overall, we considered the included RCTs to be at 'high to some concerns' risk of bias for complications, 'some concerns' risk of bias for refractive outcomes and visual acuity, and 'high' risk of bias for PROMs. The overall risk of bias for NRSs was graded 'serious' regarding complications and 'serious to critical' regarding refractive outcomes.  With regard to endophthalmitis, we found that relative effects were estimated imprecisely and with low certainty, so that relative estimates were not reliable. Nonetheless, we found a very low risk of endophthalmitis in both ISBCS (1/14,076 participants) and DSBCS (55/556,246 participants) groups. Based on descriptive evidence and partially weak statistical evidence we found no evidence of an increased risk of endophthalmitis with ISBCS. Regarding refractive outcomes, we found moderate-certainty (RCTs) and low-certainty (NRSs) evidence there was no difference in the percentage of eyes that did not achieve refraction within 1.0 dioptre of target one to three months after surgery (RCTs: risk ratio (RR) 0.84, 95% confidence interval (CI) 0.57 to 1.26; NRSs: RR 1.02, 95% CI 0.60 to 1.75). Similarly, postoperative complications did not differ between groups (RCTs: RR 1.33, 95% CI 0.52 to 3.40; NRSs: 1.04, 95% CI 0.47 to 2.29), although the certainty of this evidence was very low for both RCTs and NRSs. Furthermore, we found low-certainty (RCTs) to very low-certainty (NRSs) evidence that total costs per participant were lower for ISBCS compared to DSBCS, although results of individual studies could not be pooled. Only one study reported on cost-effectiveness. This study found that ISBCS is cost-effective compared to DSBCS, but did not measure quality-adjusted life years using preferred methods and calculated costs erroneously. Finally, regarding secondary outcomes, we found limited evidence on BCDVA (data of two RCTs could not be pooled, although both studies individually found no difference between groups (very low-certainty evidence)). Regarding PROMs, we found moderate-certainty evidence (RCTs only) that there was no difference between groups one to three months after surgery (standardised mean difference -0.08, 95% CI -0.19 to 0.03).

AUTHORS' CONCLUSIONS

Current evidence supports there are probably no clinically important differences in outcomes between ISBCS and DSBCS, but with lower costs for ISBCS. However, the amount of evidence is limited, and the certainty of the evidence was graded moderate to very low. In addition, there is a need for well-designed cost-effectiveness studies.

Discharge teaching, readiness for hospital discharge and post-discharge outcomes in cataract patients: A structural equation model analysis

AIM

To explore the interaction mechanism of cataract patients' quality of discharge teaching, discharge readiness and post-discharge outcomes using structural equation model analysis.

BACKGROUND

The quality of discharge teaching and discharge readiness are two indicators used to evaluate the quality of hospital discharge services. Little research has been done on the quality of discharge teaching, discharge readiness and post-discharge outcomes in cataract patients, especially in China.

METHODS

Four questionnaires were administered to 192 patients, and the results were analysed using Spearman's correlation and structural equation model.

RESULTS

The statistical analysis showed low-to-moderate correlations among the quality of discharge teaching, discharge readiness and post-discharge outcome variables; discharge readiness played an intermediary role in the interaction mechanism of the three variables.

CONCLUSION

The cataract patients demonstrated satisfactory quality of discharge teaching, discharge readiness and post-discharge outcomes. Quality of discharge teaching affected post-discharge outcomes through the intermediary role of discharge readiness.

IMPLICATIONS FOR NURSING MANAGEMENT

Nursing managers should recognize the importance of discharge services, pay more attention to improve the quality of discharge teaching and strengthen discharge readiness to prevent the risks of post-discharge complications and readmission.

Influence of cataract surgery for the first or second eye on vision-related quality of life (VR-QOL) and the predictive factors of VR-QOL improvement

PURPOSE

To assess improvements in vision-related quality of life (VR-QOL) in patients undergoing their first or second eye cataract surgery, as well as clinical factors related to VR-QOL.

STUDY DESIGN

Prospective case series.

METHODS

We examined 282 patients undergoing their first (222) or second (60) eye cataract surgery. VR-QOL was evaluated before and after surgery using the 25-item National Eye Institute visual function questionnaire (VFQ-25), along with the best-corrected visual acuity (BCVA), uncorrected visual acuity, and the lens opacities classification system III (LOCSIII). The resulting VFQ-25 subscale scores were compared between patients undergoing their first or second eye cataract surgery, including multiple regression analysis.

RESULTS

The mean VFQ-25 composite score (CS) was 71.5 ± 14.2 before and 84.0 ± 10.2 after the first eye cataract surgery and 73.5 ± 12.7 before and 85.4 ± 10.2 after the second eye cataract surgery. VFQ-25 scores improved significantly, with reduced disparity among patients after surgery in both groups. Preoperative CS was related to the preoperative sum of the BCVA (standardized partial regression coefficient (β) =  - 0.254, P < 0.001). Improvement in the CS was related to a preoperative poor BCVA (β = 0.203, P < 0.001), low CS (β =  - 0.693, P < 0.001), and high general health score (β = 0.118, P = 0.025).

CONCLUSIONS

VR-QOL improved after the first and second eye surgery. Many VFQ-25 subscales were related to the BCVA or LOCSIII scores. Low preoperative VR-QOL and BCVA were related to an improved postoperative VR-QOL.

Cost-effectiveness of immediate versus delayed sequential bilateral cataract surgery in the Netherlands (the BICAT-NL study): study design of a prospective multicenter randomised controlled trial

Background

Cataract surgery is one of the most frequently performed types of surgery. Most patients suffer from bilateral cataract and while cataract surgery of only one eye is effective in restoring functional vision, second-eye surgery leads to further improvements in health-related quality of life, and is cost-effective. At present, most patients undergo cataract surgery in both eyes on separate days as recommended in national guidelines, referred to as delayed sequential bilateral cataract surgery (DSBCS). An alternative procedure involves operating both eyes on the same day, but as separate procedures, known as immediately sequential bilateral cataract surgery (ISBCS). The aim of this study is to evaluate the effectiveness and costs of ISBCS compared to DSBCS, in order to test the hypothesis that ISBCS is non-inferior to DSBCS in terms of effectiveness and superior to ISBCS in terms of cost-effectiveness.

Methods/design

Multicenter non-inferiority randomised controlled clinical trial. Patients (18 years or older) with bilateral cataract and an indication for bilateral cataract surgery with an expected uncomplicated intraoperative and postoperative course are included in the study. Patients are randomly assigned to either ISBCS or DSBCS. The primary endpoint is the proportion of patients with a refractive outcome in the second eye within 1.0 dioptre from the target refraction, at 4 weeks after surgery. Secondary outcomes include corrected and uncorrected distance visual acuity, complications, patient reported outcomes (PROMs), cost-effectiveness, and budget impact. Follow-up visits are planned at 1 week after first-eye surgery and 4 weeks after second-eye surgery. At 3 months after first-eye surgery, the occurrence of complications is checked and patients fill in a final questionnaire.

Discussion

This study protocol describes the design of a multicenter non-inferiority randomised controlled trial. Current studies on ISBCS often lack information on safety regarding refractive outcomes. In addition, there is a lack of well-designed cost-effectiveness studies using established methods. The BICAT-NL study will provide more insight in refractive and cost-effectiveness outcomes for ISBCS compared to DSBCS.

Trial registration

This study was prospectively registered at Clinicaltrials.gov on January 17th 2018. (Identifier: NCT03400124.

Correlation among Lens Opacities Classification System III grading, the 25-item National Eye Institute Visual Functioning Questionnaire, and Visual Function Index-14 for age-related cataract assessment

Purpose

To evaluate the relationship between cataract types and subjective visual function among patients with age-related cataract.

Methods

This was a prospective, multicenter, 831 Chinese patient-based, cross-sectional study. Patients were administered the Visual Function Index-14 (VF-14) and the 25-item National Eye Institute Visual Functioning Questionnaire (NEI-VFQ-25) to evaluate their subjective visual function. Lens Opacities Classification System III (LOCS III) was used to evaluate the type of cataract. Relationships among these parameters were analyzed.

Results

LOCS III cortical (C) and posterior subcapsular scores are negatively associated with VF-14 (r = − 0.188, P < 0.01; r = − 0.146, P < 0.01) and total score of NEI-VFQ-25 (r = − 0.223, P < 0.01; r = − 0.160, P < 0.01), respectively; LOCS III nuclear opalescence (NO) score is positively associated with VF-14 (r = 0.087, P < 0.05) and total score of NEI-VFQ-25 (r = 0.097, P < 0.05). In multiple linear regression, a decrease in the LOCS III C score is a significant predictor for improvement of the total score of NEI-VFQ-25 (β = − 1.286, P < 0.05). In contrast, an increase in LOCS III NO score is a significant predictor for improvement of VF-14 (β = 3.826, P < 0.01) and total score of NEI-VFQ-25 (β = 4.618, P < 0.01). Patients with LOCS III C score ≤ 2 have higher VF-14 (49.38 versus 43.74, P < 0.01), total (80.73 versus 71.58, P < 0.01) and subscale scores of NEI-VFQ-25 than patients with LOCS III C score > 2.

Conclusion

Cortical cataract has adverse effects on subjective visual function, while mild-to-moderate nuclear cataract has positive effects. Furthermore, “LOCS III C score > 2” can be a potential cutoff as a reference for cataract surgery without self-assessing questionnaires.

Electronic supplementary material

The online version of this article (10.1007/s10792-020-01353-0) contains supplementary material, which is available to authorized users.

Cataract grading systems: a review of past and present

PURPOSE OF REVIEW

To provide a comprehensive summary of past cataract grading systems, how they have shaped current grading systems, and the developing technologies that are being used to assess and grade cataracts.

RECENT FINDINGS

This summary of cataract grading systems examines the development and limitations that existed in past grading systems and how they have shaped the grading systems of present time. The Lens Opacities Classification System III (LOCS III) system is currently used both clinically and for research purposes. Recent advancements in imaging technologies have allowed researchers to create automatic systems that can locate lens landmarks and provide cataract grading scores that correlate well with LOCS III clinical grades. Utilizing existing technologies, researchers demonstrate that fundus photography and optical coherence tomography can be used as cataract grading tools. Lastly, deep learning has proved to be a powerful tool that can provide objective and reproducible cataract grading scores.

SUMMARY

Cataract grading schemes have provided ophthalmologists with a way to communicate clinical findings and to compare new developments in diagnostic technologies. As technologies advance, cataract grading can become more objective and standardized, allowing for improved patient care.

Correlational Analysis of Objective and Subjective Measures of Cataract Quantification

PURPOSE

To evaluate whether correlations exist between objective and subjective measures of vision quality as a consequence of cataract and whether this may qualify the Objective Scatter Index as a supplementary means of cataract assessment.

METHODS

A prospective multicenter, cross-sectional study was conducted in 10 centers across France in patients undergoing cataract extraction surgery (lens opacity evaluated with the Lens Opacities Classification System III). A quality of life assessment using the Visual Function Index-14 (VF-14) (14 questions scored from 0 to 4) and measurement of visual acuity and evaluation of the Objective Scatter Index (HD Analyzer, Visiometrics SL, Terrassa, Spain) to assess the alteration of light scatter were used as measures in the study.

RESULTS

The study included 1,768 eyes of 1,768 patients (mean age: 72.5 years; range: 28 to 93 years). The average OSI score was 4.97 ± 3.13 (range: 0.4 to 20.5). There was good correlation between visual acuity and OSI (r = -0.47, P < .001) and between OSI and VF-14 (r = -0.11, P < .001).

CONCLUSIONS

The results presented in this study confirm that the Objective Scatter Index has sufficient correlations with visual acuity and VF-14 to supplement existing cataract diagnosis in a large population encompassing a broad spectrum of cataract presentations.

Age-related cataract, cataract surgery and subsequent mortality: a systematic review and meta-analysis

PURPOSE

Changes in lens may reflect the status of systemic health of human beings but the supporting evidences are not well summarized yet. We aimed to determine the relationship of age-related cataract, cataract surgery and long-term mortality by pooling the results of published population-based studies.

METHODS

We searched PubMed and Embase from their inception till March, 2014 for population-based studies reporting the associations of any subtypes of age-related cataract, cataract surgery with all-cause mortality. We pooled the effect estimates (hazards ratios [HRs]) under a random effects model.

RESULTS

Totally, we identified 10 unique population-based studies including 39,659 individuals at baseline reporting the associations of any subtypes of cataract with all-cause mortality from 6 countries. The presence of any cataract including cataract surgery was significantly associated with a higher risk of death (pooled HR: 1.43, 95% CI, 1.21, 2.02; P<0.001; I(2) = 64.2%). In the meta-analysis of 9 study findings, adults with nuclear cataract were at higher risks of mortality (pooled HR: 1.55, 95% CI, 1.17, 2.05; P = 0.002; I(2) = 89.2%). In the meta-analysis of 8 study findings, cortical cataract was associated with higher risks of mortality (pooled HR: 1.26, 95% CI, 1.12, 1.42; P<0.001, I(2) = 29.7%). In the meta-analysis of 6 study findings, PSC cataract was associated with higher risks of mortality (pooled HR: 1.37, 95% CI, 1.04, 1.80; P = 0.03; I(2) = 67.3%). The association between cataract surgery and mortality was marginally non-significant by pooling 8 study findings (pooled HR: 1.27, 95% CI, 0.97, 1.66; P = 0.08; I(2)= 76.6%).

CONCLUSIONS

All subtypes of age-related cataract were associated with an increased mortality with nuclear cataract having the strongest association among the 3 cataract subtypes. However, cataract surgery was not significantly related to mortality. These findings indicated that changes in lens may serve as markers for ageing and systemic health in general population.

Overweight, obesity, and age-related cataract: a meta-analysis

PURPOSE

To examine the longitudinal association of overweight/obesity with age-related cataract.

METHODS

A systematic review of the literature was performed using PubMed and Embase from their inception until June 2013 for prospective data on body mass index categories identical or similar to the World Health Organization-recommended classifications of body weight and age-related cataract including nuclear, cortical, and posterior subcapsular (PSC) cataract. Meta-analyses were conducted using random-effects models with results reported as adjusted relative risks (RRs).

RESULTS

A total of 163,013 subjects aged 40 to 84 years from six prospective cohort studies were included in the meta-analysis. Obesity was associated with an increasing risk of nuclear cataract (pooled RR, 1.12; 95% confidence interval [CI], 1.02 to 1.25), cortical cataract (pooled RR, 1.34; 95% CI, 1.07 to 1.66), and PSC cataract (pooled RR, 1.52; 95% CI, 1.31 to 1.77). Overweight was only associated with an increasing risk of PSC cataract (pooled RR, 1.23; 95% CI, 1.09 to 1.40).

CONCLUSIONS

The longitudinal associations of obesity with incident age-related cataract are confirmed by the findings in this six-study meta-analysis. The association of obesity with PSC cataract is stronger than that with nuclear or cortical cataract. Randomized control trials are warranted to examine the effectiveness and cost-effectiveness of weight reduction in obese populations to decrease the risk of age-related cataract.