Aspirin effects on the development of cataracts in patients with diabetes mellitus. Early treatment diabetic retinopathy study report 16

A systematic review of risk factors for cataract in type 2 diabetes

Type 2 diabetes (T2D) is a risk factor for cataract development. With T2D prevalence increasing, the burden of cataract-associated vision loss will also increase. We aimed to characterise cataract diabetes-specific risk factors to assist prevention and management strategies. As part of a systematic review, two investigators independently searched online electronic databases according to a predetermined protocol for relevant published data to end-March 2018. Studies were included if they were longitudinal with ≥100 participants, diabetes was defined, a description of cataract assessment was provided, data were from humans, and the reports were in English. Study quality was assessed using the Newcastle Ottawa Scale and GRADE. Of 5255 publications identified, 19 from 13 study populations were included. The overall risk of bias was low. There was between-study variability. Age and glycaemic control were consistently associated with cataract development in T2D, but blood pressure, diabetes duration, sex, and aspirin use were not. Serum lipids and smoking remain possible risk factors, but available data are inconclusive. Glycaemia is the only consistent modifiable risk factor amongst a range of candidate variables. Due to the lack of consistency of the available evidence, and since mortality associated with T2D is declining with the likelihood of increased cataract-associated vision loss, additional well-conducted longitudinal studies are needed to identify modifiable risk factors that could prevent or delay cataract formation.

Cataract prevalence and prevention in Europe: a literature review

This literature review is aimed at the evaluation of the potential for cataract prevention in Europe. It was performed using PubMed with Mesh and free-text terms. Studies included were (i) performed on a population of Caucasian origin at an age range of 40-95 years, (ii) cataract was clinically verified, (iii) drug record of prescriptions, their indication, a record of every diagnosis, dosage and quantity of prescribed medicine were available, (iv) sample size >300 and (v) published between 1990 and 2009. The results of 29 articles were reviewed. Former [3.75 (2.26-6.21)] or current smoking [2.34 (1.07-5.15)], diabetes of duration >10 years [2.72 (1.72-4.28)], asthma or chronic bronchitis [2.04 (1.04-3.81)], and cardiovascular disease [1.96 (1.22-3.14)] increased the risk of cataract. Cataract was more common in patients taking chlorpromazine during ≥90 days with a dosage ≥300 mg [8.8 (3.1-25.1)] and corticosteroids >5 years [3.25 (1.39-7.58)] in a daily dose >1600 mg [1.69 (1.17-2.43)]. Intake of a multivitamin/mineral formulation [2.00 (1.35-2.98)] or corticosteroids [2.12 (1.93-2.33)] also increased the risk of cataract. Corticosteroids applied orally [3.25 (1.39-7.58)], parenteral [1.56 (1.34-1.82)] or inhalational [1.58 (1.46-1.71)] lead to cataract more frequently than those applied topically: nasal [1.33 (1.21-1.45)], ear [1.31 (1.19-1.45)] or skin [1.43 (1.36-1.50)]. Outpatient cataract surgery was negatively associated with total cataract surgery costs, and chlorpromazine, corticosteroids and multivitamin/mineral formation increase the risk of posterior subcapsular cataract dependent on dose, treatment application and duration. This review presented a comprehensive overview of specific and general cataract risk factors and an update on most recent experimental studies and randomized control trials directed at cataract prevention.

Risk factors associated with incident cataracts and cataract surgery in the Age-related Eye Disease Study (AREDS): AREDS report number 32

OBJECTIVE

To investigate potential risk factors associated with incident nuclear, cortical, and posterior subcapsular (PSC) cataracts and cataract surgery in participants in the Age-Related Eye Disease Study (AREDS).

DESIGN

Clinic-based prospective cohort study.

PARTICIPANTS

Persons (n = 4425) 55 to 80 years of age enrolled in a controlled clinical trial of antioxidant vitamins and minerals, AREDS, for age-related macular degeneration and cataract.

METHODS

Lens photographs were graded centrally for nuclear, cortical, and PSC opacities using the AREDS system for classifying cataracts. Type-specific incident cataracts were defined as an increase in cataract grade from none or mild at baseline to a grade of moderate at follow-up, also with a grade of at least moderate at the final visit, or cataract surgery. Cox regression analyses were used to assess baseline risk factors associated with type-specific opacities and cataract surgery.

MAIN OUTCOME MEASURES

Moderate cataract was defined as a grade of 4.0 or more for nuclear opacity, 10% or more involvement within the full visible lens for cortical opacity, and 5% or more involvement of the central 5-mm circle of the lens for PSC opacity. These were graded on baseline and annual lens photographs.

RESULTS

A clinic-based cohort of 4425 persons 55 to 80 years of age at baseline was followed up for an average of 9.8±2.4 years. The following associations were found: increasing age with increased risk of all types of cataract and cataract surgery; males with increased risk of PSC and decreased risk of cortical cataracts; nonwhite persons with increased risk of cortical cataract; hyperopia with decreased risk of PSC, nuclear cataract, and cataract surgery; Centrum (Wyeth Consumer Healthcare, Madison, NJ) use with decreased risk of nuclear cataract; diabetes with increased risk of cortical, PSC cataract, and cataract surgery; higher educational level with decreased risk of cortical cataract; and smoking with increased risk of cortical cataract and cataract surgery. Estrogen replacement therapy in female participants increased the risk of cataract surgery.

CONCLUSIONS

These findings largely are consistent with the results of previous studies, providing further evidence for possible modifiable risk factors for age-related cataract.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Effect of systemic medications on onset and progression of diabetic retinopathy

Diabetic retinopathy remains a leading cause of visual loss worldwide. Patients with diabetes mellitus commonly have multiple comorbidities treated with a wide variety of medications. Systemic medications that target glycemic control and coexisting conditions may have beneficial or deleterious effects on the onset or progression of diabetic retinopathy. In addition, data is accumulating to suggest that the use of systemic therapy primarily to address ocular complications of diabetic retinopathy may be a promising therapeutic approach. This article reviews our current understanding of the ocular-specific effects of systemic medications commonly used by patients with diabetes mellitus, including those directed at control of hyperglycemia, dyslipidemia, hypertension, cardiac disease, anemia, inflammation and cancer. Current clinical evidence is strongest for the use of angiotensin-converting enzyme inhibitors and angiotensin-2 receptor blockers in preventing the onset or slowing the progression of early diabetic retinopathy. To a more limited extent, evidence of a benefit of fibrates for diabetic macular edema exists. Numerous other agents hold considerable promise or potential risk. Thus, these compounds must undergo further rigorous study to determine the actual clinical efficacy and adverse effects before definitive therapeutic care recommendations can be offered.

Pharmacological prevention of diabetic cataract

Cataract--opacification of the lens--is closely related to diabetes as one of its major late complications. This review deals with three molecular mechanisms that may be involved in the development of diabetic cataract: nonenzymatic glycation of eye lens proteins, oxidative stress, and activated polyol pathway in glucose disposition. Implications resulting from these mechanisms for possible pharmacological interventions to prevent diabetic cataract are discussed. The article reviews research on potential anticataract agents, including glycation inhibitors, antioxidants, and aldose reductase inhibitors. Information on possible benefits of putative anticataract agents comes from a variety of approaches, ranging from laboratory experiments, both in vitro and in vivo, to epidemiological studies in patients.

Perspectives on diabetic retinopathy

PURPOSE

To review the evolution of the understanding of diabetic retinopathy (DR) and methods of treating DR, the present clinically relevant practice for eye disease in patients with diabetes mellitus, and trends in clinical patient care over the next 3 to 5 years.

DESIGN

Tabular review and presentation of clinical trials contributing to the understanding and treatment of DR and the author's philosophy of care for the patient with diabetes.

RESULTS

Diabetic retinopathy is a microvascular complication of diabetes mellitus that is a significant cause of new-onset blindness. The Diabetic Retinopathy Study was the first multicentered, randomized, clinical trial in ophthalmology. This study provided the scientific evidence for treatment of DR with scatter (panretinal) photocoagulation, and led to the funding of other multicentered clinical trials, including the Early Treatment Diabetic Retinopathy Study, which greatly elucidated the natural history of DR and firmly established laser photocoagulation as treatment for proliferative diabetic retinopathy (PDR) and diabetic macular edema. The Diabetes Control and Complications Trial and United Kingdom Prospective Diabetes Study established the value of intensive glycemic control in reducing the risk of onset and progression of DR and other microvascular complications of diabetes.

CONCLUSIONS

Severe vision loss and moderate vision loss from diabetes are essentially preventable with timely detection and treatments, careful long-term follow-up and comprehensive diabetes mellitus care firmly based on clinical evidence. Future treatments, as outgrowths of further understanding of the biochemical basis of the disease, will aim at curing or preventing retinal complications from diabetes.

Aspirin in diabetic retinopathy. A systematic review

Diabetes mellitus is a risk factor for eye disease that can lead to blindness. There have been both concerns that aspirin use might worsen diabetic retinopathy, as well as hopes that aspirin might be beneficial in treating it. We investigated whether there are beneficial effects of aspirin alone and in combination with other antiplatelet agents in the treatment of diabetic retinopathy, and the relative hazards for the development of high-risk proliferative retinopathy following aspirin treatment. We conducted a sensitive search for randomized controlled trials combined with index terms for identifying studies on aspirin treatment in diabetic retinopathy in the Cochrane Library (issue 4, 2001) and Medline (1966 to October, 2001). We examined randomized controlled clinical trials in diabetic patients with (non) proliferative diabetic retinopathy and aspirin treatment alone or in combination with dipyramidole versus placebo administration. Two independent reviewers judged trial eligibility, collected details of study population, interventions, and outcomes using a standard data extraction form. One reviewer assessed the quality of trial reporting. We identified six publications pertinent to our objective. Aspirin dosages ranged from 650 mg to 990 mg daily, the dose of dipyridamole, used in only one trial, was 225 mg per day. Studies lasted 8 weeks to 5 years. All trials showed that aspirin alone or in combination with dipyridamole neither lowered nor increased the risk of the development of diabetic retinopathy. The results suggest that there are no ocular contraindications to taking aspirin if required as part of a treatment for cardiovascular diseases or other medical indications.

Zeta-crystallin displays strong selectivity for salicylic acid over aspirin

Interaction of camel lens zeta-crystallin with aspirin was investigated by activity and fluorescence measurements. Aspirin minimally inhibited the oxidoreductase activity of the enzyme and weakly quenched its fluorescence. However, significant fluorescence quenching of zeta-crystallin coincided with the appearance of a fluorescence signal characteristic of salicylic acid thereby raising the possibility that salicylic acid might have been the moiety responsible for inhibition and fluorescence quenching. Direct fluorescence measurements showed that zeta-crystallin had a much higher affinity for salicylic acid than aspirin (K(i) of about 24 microM for salicylic acid versus 630 microM for aspirin). Salicylic acid was also far more effective in inhibiting zeta-crystallin than aspirin (K(i) values were 23 microM versus 820 microM, respectively). Inhibition kinetics suggested that salicylic acid interacted with zeta-crystallin via a binding site that was distinct from that of NADPH. Salicylic acid also interacted with and quenched the fluorescence of camel lens alpha-crystallin suggesting a general mode of interaction with lens proteins. Within the normal therapeutic concentrations of salicylic acid or aspirin, only crystallin-salicylic acid interactions might be significant. These results showed that camel lens zeta- and alpha-crystallin exhibited remarkable selectivity for salicylic acid over aspirin, and thus, could be considered as salicylate-binding proteins.

Can drugs or micronutrients prevent cataract?

Cataract is the major cause of blindness and of visual impairment worldwide, so its prevention is of the greatest importance. At present no drug therapy is licensed for use in the UK or the US, so the only treatment for cataract is by surgery, which is expensive and has adverse effects. This article reviews research on prevention of cataract by a variety of agents, including micronutrients as well as drugs. Benefits have been claimed for many compounds or mixtures and this review concentrates on those most extensively studied. Information on possible benefits of putative anticataract agents comes from a variety of approaches, from laboratory experiments, both in vitro and in vivo, to epidemiological studies in patients. Sorbitol-lowering drugs were the first to be examined systematically and progressed to clinical trials which were disappointing, and now the entire rationale for their use in prevention of cataract is questionable. Micronutrients showed little promise in animals but came to clinical trial in patients with cataract without the publication of any major benefit. Pantethine showed more promise in animal studies but the only clinical trial was abandoned early. A variety of laboratory and epidemiological evidence supports the benefits of aspirin-like drugs but there has been no trial specifically in patients with cataract. Add-on studies to trials of aspirin for other indications have not been encouraging. Research into other compounds is interesting but less advanced.

Risk factors associated with age-related nuclear and cortical cataract : a case-control study in the Age-Related Eye Disease Study, AREDS Report No. 5

OBJECTIVE

To investigate possible risk factors for age-related nuclear and cortical cataracts in participants in the Age-Related Eye Disease Study (AREDS).

DESIGN

Case-control study.

PARTICIPANTS

Of the 4757 persons enrolled in AREDS, 4477 age 60 to 80 years are included in the study.

MAIN OUTCOME MEASURES

Slit-lamp lens photographs were used to classify participants into one of three nuclear opacity groups (moderate nuclear, mild nuclear, and controls), ignoring cortical opacities. Retroillumination lens photographs were used to classify participants into one of three cortical opacity groups (moderate cortical, mild cortical, and controls), ignoring nuclear opacities.

RESULTS

Persons with moderate nuclear opacities were more likely to be female, nonwhite, and smokers and to have large drusen. Moderate nuclear opacities were less common in persons with higher educational status, a history of diabetes, and among those taking nonsteroidal antiinflammatory drugs. Moderate cortical opacities were associated with dark iris color, large drusen, weight change, and, at a borderline level of significance, higher levels of sunlight exposure and use of thyroid hormones. Moderate cortical opacities were less common in persons with higher educational status.

CONCLUSION

Consistent findings have now been reported across many studies for gender, educational status, sunlight exposure, and smoking. Our findings that use of nonsteroidal antiinflammatory drugs is inversely associated with nuclear cataract and that dark iris color and use of thyroid hormones may increase cortical cataract risk are less well substantiated and require further investigation.

Antidenaturant drugs for cataract and other condensation diseases

'Condensation diseases' are heterogeneous pathological conditions in which the primary pathogenetic step is the loss of solubility of specific substances, resulting in the formation of a condensed phase. Typical examples are cataract, nephrolithiasis, gallstone disease and certain rheumatic conditions in which protein denaturation, aggregation and precipitation may occur. Since the condensing molecules are often proteins, antidenaturant agents should be considered rational drugs for the treatment of these diseases. Surprisingly, however, only a few molecules with these properties are currently available for therapeutic use, including bendazac for cataract.

Epidemiology of risk factors for age-related cataract

Epidemiologic studies on risk factors for cataract have progressed significantly over the last decade. Age-related cataract is a multifactorial disease, and different risk factors seem to play a role for different cataract types. Cortical and posterior subcapsular cataracts appear to be most closely related to environmental stresses such as ultraviolet exposure, diabetes, and drug ingestion. Nuclear cataracts appear to be associated with smoking. Alcohol use seems to be associated with all cataract types. Consistent evidence also suggests that the prevalence of all cataract types is lower among those with higher education. Most of the current data support a role for antioxidants associated with decreased rates of all cataract types, but further studies are needed. More data are needed to establish the association, if any, of diarrhea, blood pressure, and use of allopurinol and phenothiazines with senile cataracts.