Prevention strategies for age related cataract: present limitations and future possibilities

Smoking Cessation May Reduce Risk of Visual Field Progression in Heavy Smokers

PRCIS

The earlier a person quits smoking the more likely is the optic nerve be spared from damage.

PURPOSE

To investigate the effect of smoking cessation on visual field (VF) progression in glaucoma.

METHODS

Primary open angle glaucoma patients with a minimum of 3 years follow-up and 5 VFs were included. Linear mixed models were used to investigate the effects of smoking on the rates of 24-2 VF mean deviation loss after adjusting for confounding factors. Cox proportional hazard regression was used to identify whether different levels of smoking intensity were associated with VF progression with respect to different duration of quitting.

RESULTS

Five hundred eleven eyes of 354 patients were included over the mean follow-up of 12.4 years. Mean baseline age (95% confidence interval) was 62.3 (61.2, 63.4) years. One hundred forty nine (42.1%) patients were smokers. In a multivariable model, smoking intensity was associated with faster VF loss (-0.06, 95% confidence interval (-0.10, -0.01) dB/year per 10 pack-years, P =0.01) among smokers. Heavy smokers (≥20 pack-years) who had quit ˂25 years prior had significantly greater odds of VF progression compared with never smokers (odds ratio=2.49 (1.01, 6.08); P =0.046). There was no significant difference in odds of VF progression in heavy smokers who had quit smoking more than 25 years compared with never smokers ( P =0.43). A significantly higher proportion of VF progression was found in heavy smokers who quit < 25 years compared with heavy smokers who quit ≥25 years by Kaplan-Meier analysis ( P =<0.001).

CONCLUSIONS

After ≥25 years of smoking cessation, the risk of VF progression in former heavy smokers becomes similar to never smokers. Long-term smoking cessation may be associated with lower VF progression in glaucoma patients.

Screening for Impaired Visual Acuity in Older Adults: US Preventive Services Task Force Recommendation Statement

IMPORTANCE

Impairment of visual acuity is a serious public health problem in older adults. The number of persons 60 years or older with impaired visual acuity (defined as best corrected visual acuity worse than 20/40 but better than 20/200) was estimated at 2.91 million in 2015, and the number who are blind (defined as best corrected visual acuity of 20/200 or worse) was estimated at 760 000. Impaired visual acuity is consistently associated with decreased quality of life in older persons, including reduced ability to perform activities of daily living, work, and drive safely, as well as increased risk of falls and other unintentional injuries.

OBJECTIVE

To update its 2016 recommendation, the US Preventive Services Task Force (USPSTF) commissioned a systematic review to evaluate the benefits and harms of screening for impaired visual acuity in older adults.

POPULATION

Asymptomatic adults 65 years or older who present in primary care without known impaired visual acuity and are not seeking care for vision problems.

EVIDENCE ASSESSMENT

The USPSTF concludes that the evidence is insufficient to assess the balance of benefits and harms of screening for impaired visual acuity in asymptomatic older adults. The evidence is lacking, and the balance of benefits and harms cannot be determined. More research is needed.

RECOMMENDATION

The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for impaired visual acuity in older adults. (I statement).

Marijuana smoking and cataract

BACKGROUND

Cigarette smoking is a well-known risk factor for cataract and other ailments, including heart disease, lung cancer, and chronic obstructive pulmonary disease. Cannabis smoke, like tobacco smoke, contains a comparable variety of carcinogenic and toxic compounds.

PURPOSE

In the present study, we analyzed UK Biobank data to determine whether smoking cannabis, like cigarettes, might be related to cataract.

METHODS

Our analysis included all UK Biobank subjects with cataracts and information on cannabis and cigarette smoking habits. The diagnosis of cataract was ascertained using the 10th Revision of the International Classification of Diseases (ICD10), H25. The age at diagnosis of cataract was obtained from UK Biobank data field 4700. Cannabis information was recorded in UK Biobank category 143, data field 20453, ever taken cannabis.

RESULTS

Subjects who used cannabis 11-100 times or more were significantly younger (4-5 years) when they developed cataract than subjects who never used cannabis. To determine the relationship of current cigarette smoking to cannabis use and age at cataract, the univariate general linear model of SPSS was used, dependent variable age at cataract, fixed factor cannabis use, random factor pack years of cigarettes smoked. Cannabis use was significantly related to age at cataract diagnosis (P<0.001) and independent of the effect of pack-years of cigarettes smoked (P=0.008). Linear regression revealed an insignificant relationship between pack-years of cigarette smoking and age at cataract diagnosis (P=0.073). To further evaluate the relationship of cannabis to cataract, propensity score matching was performed. We identified 28,432 subjects with cataract. Current cigarette smoking and age were covariates; cannabis use (yes/no) was the indicator variable. Current cigarette smoking was significantly associated with a 1.2 odds ratio for cataract. Cannabis use was not significantly associated with the odds ratio for cataract.

CONCLUSION

Like tobacco smoke, cannabis smoke contains thousands of organic and inorganic chemical compounds. Cannabis tar is chemically similar to tar found in tobacco smoke, and over fifty known carcinogens have been identified in cannabis smoke, including nitrosamines, reactive aldehydes, and polycyclic hydrocarbons. Thus, the association of cannabis with cataract that we report here is not entirely surprising. Further studies are warranted.

Thiol antioxidants protect human lens epithelial (HLE B-3) cells against tert-butyl hydroperoxide-induced oxidative damage and cytotoxicity

Oxidative damage to lens epithelial cells plays an important role in the development of age-related cataract, and the health of the lens has important implications for overall ocular health. As a result, there is a need for effective therapeutic agents that prevent oxidative damage to the lens. Thiol antioxidants such as tiopronin or N-(2-mercaptopropionyl)glycine (MPG), N-acetylcysteine amide (NACA), N-acetylcysteine (NAC), and exogenous glutathione (GSH) may be promising candidates for this purpose, but their ability to protect lens epithelial cells is not well understood. The effectiveness of these compounds was compared by exposing human lens epithelial cells (HLE B-3) to the chemical oxidant tert-butyl hydroperoxide (tBHP) and treating the cells with each of the antioxidant compounds. MTT cell viability, apoptosis, reactive oxygen species (ROS), and levels of intracellular GSH, the most important antioxidant in the lens, were measured after treatment. All four compounds provided some degree of protection against tBHP-induced oxidative stress and cytotoxicity. Cells treated with NACA exhibited the highest viability after exposure to tBHP, as well as decreased ROS and increased intracellular GSH. Exogenous GSH also preserved viability and increased intracellular GSH levels. MPG scavenged significant amounts of ROS, and NAC increased intracellular GSH levels. Our results suggest that both scavenging ROS and increasing GSH may be necessary for effective protection of lens epithelial cells. Further, the compounds tested may be useful for the development of therapeutic strategies that aim to prevent oxidative damage to the lens.

Common causes of visual impairment in the elderly

Background

Aging is not a disease; rather, it is a process. As people age, visual impairment (VI) becomes more common. In 2010, the overall prevalence rate of vision impairment in all races was 25.66% in individuals aged ≥ 80 years, according to the estimate of the National Eye Institute at the National Institutes of Health. This review aimed to address the common causes of VI in the elderly.

Methods

In this narrative review, an electronic search of the PubMed/MEDLINE database was conducted using "visual impairment" and "elderly" for the period between January 2010 and April 2021, to include randomized clinical trials and observational studies concerning VI in the elderly. The selected time period was chosen to provide an updated review.

Results

The search yielded 2955 articles published over the period of more than 11 years. The relevant randomized clinical trials or observational studies were included and reviewed. Cataracts, refractive errors, open-angle glaucoma, age-related macular degeneration, and diabetic retinopathy were the most common age-related ocular disorders leading to VI if untreated in the elderly. The loss of visual acuity can adversely affect quality of life in the elderly. Difficulty with activities of daily living related to VI can lead to social isolation, depression, and anxiety. Loss of vision in the elderly is linked to an increased risk of falls, hip fracture, depression, and poor quality of life.

Conclusions

The most common causes of VI in the elderly are cataracts and refractive errors. VI in most ocular diseases is more prevalent in women than in men due to longer lifespan. The overall prevalence of the main causes of VI in the elderly is expected to increase; therefore, health policymakers should consider this when planning for the health-enhancement program of the population.

Habitual Tea Consumption and Risk of Cataracts: A Longitudinal Study

We aimed to investigate the association between habitual tea consumption and the risk of developing cataracts in a large community-based cohort study. We prospectively collected volunteers from 29 recruitment centers that were ≧ 55 years old with no history of cataracts at the beginning of the study. There were 12,080 participants with available information in our study and were divided into two groups according to habitual tea consumption; non-tea-drinking and tea-drinking groups. The mean age was 59 years. Compared to the non-tea-drinking group, the tea-drinking group had a significantly lower incidence of developing cataracts (15.5% vs 12.1%) during follow-up of 46 months. In multivariate Cox proportional hazards regression analysis, the relative risk (RR) of incident cataracts was lower in the tea-drinking group than the non-tea-drinking group (RR = 0.848; 95% confidence interval [CI] = 0.751 to 0.957). Participants with ≧ 2 cups per day were associated with almost 16% reduction in the risk of developing cataracts compared with the non-tea-drinking group (RR = 0.844; 95% CI = 0.741 to 0.961). Our study suggests that habitual tea consumption can reduce the incidence of cataracts and raises the possibility that the tea content may slow the progression of cataracts.

Factors associated with the uptake of cataract surgery and interventions to improve uptake in low- and middle-income countries: A systematic review

Despite significant evidence around barriers hindering timely access to cataract surgery in low- and middle-income countries (LMICs), little is known about the strategies necessary to overcome them and the factors associated with improved access. Despite significant evidence that certain groups, women for example, experience disproportionate difficulties in access, little is known about how to improve the situation for them. Two reviews were conducted recently: Ramke et al., 2018 reported experimental and quasi-experimental evaluations of interventions to improve access of cataract surgical services, and Mercer et al., 2019 investigated interventions to improve gender equity. The aim of this systematic review was to collate, appraise and synthesise evidence from studies on factors associated with uptake of cataract surgery and strategies to improve the uptake in LMICs. We performed a literature search of five electronic databases, google scholar and a detailed reference review. The review identified several strategies that have been suggested to improve uptake of cataract surgery including surgical awareness campaigns; use of successfully operated persons as champions; removal of patient direct and indirect costs; regular community outreach; and ensuring high quality surgeries. Our findings provide the basis for the development of a targeted combination of interventions to improve access and ensure interventions which address barriers are included in planning cataract surgical services. Future research should seek to examine the effectiveness of these strategies and identify other relevant factors associated with intervention effects.

Drug delivery to the lens for the management of cataracts

Cataracts are one of the most prevalent diseases of the lens, affecting its transparency and are the leading cause of reversible blindness in the world. The clarity of the lens is essential for its normal physiological function of refracting light onto the retina. Currently there is no pharmaceutical treatment for prevention or cure of cataracts and surgery to replace the affected lens remains the gold standard in the management of cataracts. Pharmacological treatment for prevention of cataracts is hindered by many physiological barriers that must be overcome by a therapeutic agent to reach the avascular lens. Various therapeutic agents and formulation strategies are currently being investigated to prevent cataract formation as access to surgery is limited. This review provides a summary of recent research in the field of drug delivery to the lens for the management of cataracts including models used to study cataract treatments and discusses the future perspectives in the field.

Exposure to subthreshold dose of UVR-B induces apoptosis in the lens epithelial cells and does not in the lens cortical fibre cells

PURPOSE

The aim of this study was to investigate in which part of the lens in vivo exposure to subthreshold dose of UVR-B radiation induces apoptosis.

METHODS

Twenty 6-week-old female albino Sprague-Dawley rats were exposed to subthreshold dose (1 kJ/m² ) of UVR-B unilaterally and killed at 120 hr after exposure. Lenses were enucleated and dissected on three regions: the lens epithelium, the cortex and the nucleus. The lens nucleus then was removed. Apoptosis markers p53 and caspase 3 were used to study apoptosis in the lens regions. qRT-PCR and Western blot were utilized to analyse the lenses.

RESULTS

TP53 and CASP3 mRNA expressions are increased in exposed lenses, both in the lens epithelium and in the cortex regions, in relation to non-exposed lenses. Expression of p53 protein is increased in exposed lens epithelium in relation to non-exposed lens epithelium. Caspase 3 protein is expressed in exposed lens epithelial cells, while it is not expressed in non-exposed lens epithelial cells. p53 and caspase 3 proteins are not expressed in either exposed nor non-exposed lens fibre cells.

CONCLUSION

Exposure to UVR-B increases mRNA transcription of apoptosis marker p53 in vivo in both regions of the lens and of apoptosis marker caspase 3 in the lens cortex. Exposure to UVR-B increases p53 and caspase 3 proteins expression just in the lens epithelium. In vivo exposure to subthreshold dose of UVR-B induces apoptosis in the lens epithelial cells and does not in the lens fibre cells.

Paradigm Shifts in Ophthalmic Diagnostics

PURPOSE

Future advances in ophthalmology will see a paradigm shift in diagnostics from a focus on dysfunction and disease to better measures of psychophysical function and health. Practical methods to define genotypes will be increasingly important and non-invasive nanotechnologies are needed to detect molecular changes that predate histopathology.

METHODS

This is not a review nor meant to be comprehensive. Specific topics have been selected to illustrate the principles of important paradigm shifts that will influence the future of ophthalmic diagnostics. It is our impression that future evaluation of vision will go beyond visual acuity to assess ocular health in terms of psychophysical function. The definition of disease will incorporate genotype into what has historically been a phenotype-centric discipline. Non-invasive nanotechnologies will enable a paradigm shift from disease detection on a cellular level to a sub-cellular molecular level.

RESULTS

Vision can be evaluated beyond visual acuity by measuring contrast sensitivity, color vision, and macular function, as these provide better insights into the impact of aging and disease. Distortions can be quantified and the psychophysical basis of vision can be better evaluated than in the past by designing tests that assess particular macular cell function(s). Advances in our understanding of the genetic basis of eye diseases will enable better characterization of ocular health and disease. Non-invasive nanotechnologies can assess molecular changes in the lens, vitreous, and macula that predate visible pathology. Oxygen metabolism and circulatory physiology are measurable indices of ocular health that can detect variations of physiology and early disease.

CONCLUSIONS

This overview of paradigm shifts in ophthalmology suggests that the future will see significant improvements in ophthalmic diagnostics. The selected topics illustrate the principles of these paradigm shifts and should serve as a guide to further research and development. Indeed, successful implementation of these paradigm shifts in ophthalmology may provide useful guidance for similar developments in all of healthcare.

The Association of Outdoor Activity and Age-Related Cataract in a Rural Population of Taizhou Eye Study: Phase 1 Report

Purpose

To study the relationship between outdoor activity and risk of age-related cataract (ARC) in a rural population of Taizhou Eye Study (phrase 1 report).

Method

A population-based, cross-sectional study of 2006 eligible rural adults (≥45 years old) from Taizhou Eye Study was conducted from Jul. to Sep. 2012. Participants underwent detailed ophthalmologic examinations including uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), intraocular pressure (IOP), slit lamp and fundus examinations as well as questionnaires about previous outdoor activity and sunlight protection methods. ARC was recorded by LOCSⅢ classification system. The prevalence of cortical, nuclear and posterior subcapsular cataract were assessed separately for the risk factors and its association with outdoor activity.

Results

Of all 2006 eligible participants, 883 (44.0%) adults were diagnosed with ARC. The prevalence rates of cortical, nuclear and posterior subcapsular cataract per person were 41.4%, 30.4% and 1.5%, respectively. Women had a higher tendency of nuclear and cortical cataract than men (OR = 1.559, 95% CI 1.204–2.019 and OR = 1.862, 95% CI 1.456–2.380, respectively). Adults with high myopia had a higher prevalence of nuclear cataract than adults without that (OR = 2.528, 95% CI 1.055–6.062). Multivariable logistic regression revealed that age was risk factor of nuclear (OR = 1.190, 95% CI 1.167–1.213) and cortical (OR = 1.203, 95% CI 1.181–1.226) cataract; eyes with fundus diseases was risk factor of posterior subcapsular cataract (OR = 6.529, 95% CI 2.512–16.970). Outdoor activity was an independent risk factor of cortical cataract (OR = 1.043, 95% CI 1.004–1.083). The risk of cortical cataract increased 4.3% (95% CI 0.4%-8.3%) when outdoor activity time increased every one hour. Furthermore, the risk of cortical cataract increased 1.1% (95% CI 0.1%-2.0%) when cumulative UV-B exposure time increased every one year.

Conclusion

Outdoor activity was an independent risk factor for cortical cataract, but was not risk factor for nuclear and posterior subcapsular cataract. The risk of cortical cataract increased 4.3% when outdoor activity time increased every one hour. In addition, the risk of cortical cataract increased 1.1% (95% CI 0.1%-2.0%) when cumulative UV-B exposure time increased every one year.

Acute effect of cigarette smoking on pupil size and ocular aberrations: a pre- and postsmoking study

Aim. To evaluate the acute effects of cigarette smoking on photopic and mesopic pupil sizes and wavefront aberrations. Methods. Cigarette smoker volunteers were recruited in the study. Photopic and mesopic pupil sizes and total ocular aberrations were measured before smoking and immediately after smoking. All volunteers were asked to smoke a single cigarette containing 1.0 mg nicotine. Pupil sizes and total ocular aberrations were assessed by optical path difference scanning system (OPD-Scan II ARK-10000, NIDEK). Only the right eyes were considered for statistical analysis. The changes of pupil size and total ocular aberrations after smoking were tested for significance by Wilcoxon signed ranks test. Results. Mean photopic pupil size decreased from 3.52 ± 0.73 mm to 3.29 ± 0.58 mm (P = 0.001) after smoking. Mean mesopic pupil size was also decreased from 6.42 ± 0.75 mm to 6.14 ± 0.75 mm after smoking (P = 0.001). There was a decrease in all the measured components of aberrations (total wavefront aberration, higher-order aberration, total coma, total trefoil, total tetrafoil, total spherical aberration and total higher-order aberration) after smoking; however the differences were insignificant for all (P > 0.05). Conclusion. Our results indicate that pupil constricts after smoking. On the other hand, smoking does not alter ocular aberrations.

Effects of smoking on visual acuity of central serous chorioretinopathy patients

BACKGROUND

The aim of this study was to evaluate the differences, in terms of visual outcome and treatment needs, between smokers and non-smokers central serous chorioretinopathy (CSCR) patients.

METHODS

The files of 252 patients diagnosed with CSCR who had presented to the Retina Unit of the Ophthalmology Clinic at Dicle University Medical School in Turkey were retrospectively evaluated. Eighty-four smokers, with a known history of smoking of at least one pack-year, and 133 non-smokers were included, whereas 35 patients with additional pathologies were excluded from the study.

RESULTS

Of the patients, 192 (88.5%) were male and 25 (11.5%) were female. The mean patient age was 38.8 ± 8.1 years (range: 20-68 years). Visual acuity (VA) of the smoker and non-smoker groups was measured as 0.45 ± 0.35 and 0.24 ± 0.28 logarithm of the minimum angle of resolution (logMar), respectively, at the first visit; 0.19 ± 0.29 and 0.06 ± 0.14 logMar at the sixth month; and 0.07 ± 0.14 and 0.02 ± 0.05 logMar at the ninth month. VA measurements at presentation and during all examinations (1th, 6th and 9th month) were significantly different for the two groups. VA was lower in the smoker group. In 27 patients (12.4%), an additional treatment modality was needed. Of the 27 patients, only 8 (6%) were non-smokers, whereas 19 (22.6%) were smokers. There was no difference between groups in the recurrence rate during follow-up (p = 0.907); 14 (16.7%) smokers and 8 (19.0%) non-smokers experienced a recurrence.

CONCLUSION

This study has shown that patients selected and who are current smokers have poorer vision and need longer treatment.

Sociodemographic correlates of eye care provider visits in the 2006-2009 Behavioral Risk Factor Surveillance Survey

Background

Research has suggested that adults 40 years old and over are not following eye care visit recommendations. In the United States, the proportion of older adults is expected to increase drastically in the coming years. This has important implications for population ocular disease burden, given the relationship between older age and the development of many ocular diseases and conditions. Understanding individual level determinants of vision health could support the development of tailored vision health campaigns and interventions among our growing older population. Thus, we assessed correlates of eye care visits among participants of the Behavior Risk Factor Surveillance System (BRFSS) survey. We pooled and analyzed 2006–2009 BRFSS data from 16 States (N = 118,075). We assessed for the proportion of survey respondents 40 years of age and older reporting having visited an eye care provider within the past two years, two or more years ago, or never by socio-demographic characteristics.

Results

Nearly 80% of respondents reported an eye care visit within the previous two years. Using the ‘never visits’ as the referent category, the groups with greater odds of having an ocular visit within the past two years included those: greater than 70 years of age (OR = 6.8 [95% confidence interval = 3.7–12.6]), with college degree (5.2[3.0–8.8]), reporting an eye disease, (4.74[1.1–21.2]), diagnosed with diabetes (3.5[1.7–7.5]), of female gender (2.9[2.1–3.9]), with general health insurance (2.7[1.8–3.9]), with eye provider insurance coverage (2.1[1.5–3.0]), with high blood pressure (1.5[1.1–2.2]), and with moderate to extreme near vision difficulties (1.42[1.11–2.08]).

Conclusion

We found significant variation by socio-demographic characteristics and some variation in state-level estimates in this study. The present findings suggest that there remains compliance gaps of screening guidelines among select socio-demographic sub-groups, as well as provide evidence and support to the CDC’s Vision Health Initiative. This data further suggests that there remains a need for ocular educational campaigns in select socio-demographic subgroups and possibly policy changes to enhance insurance coverage.

Orally active multi-functional antioxidants delay cataract formation in streptozotocin (type 1) diabetic and gamma-irradiated rats

BACKGROUND

Age-related cataract is a worldwide health care problem whose progression has been linked to oxidative stress and the accumulation of redox-active metals. Since there is no specific animal model for human age-related cataract, multiple animal models must be used to evaluate potential therapies that may delay and/or prevent cataract formation.

METHODS/PRINCIPAL FINDINGS

Proof of concept studies were conducted to evaluate 4-(5-hydroxypyrimidin-2-yl)-N,N-dimethyl-3,5-dioxopiperazine-1-sulfonamide (compound 4) and 4-(5-hydroxy-4,6-dimethoxypyrimidin-2-yl)-N,N-dimethyl-3,5-dioxopiperazine-1-sulfonamide (compound 8), multi-functional antioxidants that can independently chelate redox metals and quench free radicals, on their ability to delay the progression of diabetic "sugar" cataracts and gamma radiation-induced cataracts. Prior to 15 Gy of whole head irradiation, select groups of Long Evans rats received either diet containing compound 4 or 8, or a single i.p. injection of panthethine, a radioprotective agent. Compared to untreated, irradiated rats, treatment with pantethine, 4 and 8 delayed initial lens changes by 4, 47, and 38 days, respectively, and the average formation of posterior subcapsular opacities by 23, 53 and 58 days, respectively. In the second study, select groups of diabetic Sprague Dawley rats were administered chow containing compounds 4, 8 or the aldose reductase inhibitor AL1576. As anticipated, treatment with AL1576 prevented cataract by inhibiting sorbitol formation in the lens. However, compared to untreated rats, compounds 4 and 8 delayed vacuole formation by 20 days and 12 days, respectively, and cortical cataract formation by 8 and 3 days, respectively, without reducing lenticular sorbitol. Using in vitro lens culture in 30 mM xylose to model diabetic "sugar" cataract formation, western blots confirmed that multi-functional antioxidants reduced endoplasmic reticulum stress.

CONCLUSIONS/SIGNIFICANCE

Multi-functional antioxidants delayed cataract formation in two diverse rat models. These studies provide a proof of concept that a general cataract treatment focused on reducing oxidative stress instead of a specific mechanism of cataractogenesis can be developed.

Apoptosis gene profiling reveals spatio-temporal regulated expression of the p53/Mdm2 pathway during lens development

Evidence is emerging for apoptosis gene expression in the lens during development. Therefore, here we used a filter array to assess expression of 243 apoptosis-related genes in the developing postnatal mouse lens using (33)P labelled cDNA synthesized from p7 and p14 mouse lenses. We demonstrated that 161 apoptosis-related genes were expressed at levels significantly above background and 20 genes were potentially significantly differentially expressed (P<0.05) by at least 2-fold between p7 and p14. We used RT-PCR to confirm expression of these genes in newborn, p7, p14 and 4 wk mouse lens cDNA samples. Expression of 19/20 of the genes examined was confirmed, while 5 genes (Huntingtin, Mdm2, Dffa, galectin-3 and Mcl-1) were confirmed as differentially regulated between p7 and p14. RT-PCR was also used to examine the expression of the chick homologues of the most-highly expressed and/or potentially differentially regulated genes in chick embryo lenses at E6-E16. The majority of genes expressed in the postnatal mouse lens were also expressed in the chick embryo lens. Western blotting confirmed developmentally regulated expression of Axl and Mcl-1 during mouse lens development and of Mdm2, Mdm4/X and p53 during mouse and chick lens development. Western blotting also revealed the presence of p53 and Mdm4/X splice variants and/or proteolytic cleavage products in the developing lens. Since Mdm2 is a regulator of the tumour suppressor gene p53, we chose to thoroughly investigate the spatio-temporal expression patterns of p53, Mdm2 and the functionally related Mdm4/X in mouse lens development at E12.5-E16.5 using immunocytochemistry. We also examined Mdm2 expression patterns during chick lens development at E6-E16 and Mdm4/X and p53 at E14. Expression of Mdm2, Mdm4/X and p53 was spatio-temporally regulated in various compartments of the developing lens in both mouse and chick, including lens epithelial and lens fibre cells, indicating potential roles for these factors in regulation of lens epithelial cell proliferation and/or lens fibre cell differentiation This study provides a thorough initial analysis of apoptosis gene expression in the postnatal mouse lens and provides a resource for further investigation of the roles in lens development of the apoptosis genes identified. Furthermore, building on the array studies, we present the first spatio-temporal analysis of expression of p53 pathway molecules (p53, Mdm2 and Mdm4/X) in both developing mouse and chick lenses, suggesting a potential role for the p53/Mdm2 pathway in lens development, which merits further functional analysis.

5-S-GAD, a novel radical scavenging compound, prevents lens opacity development

The ability of N-beta-alanyl-5-S-glutathionyl-3,4-dihydroxyphenylalanine (5-S-GAD)-a novel catechol derivative isolated from an insect as an antibacterial substance-to scavenge free radicals and prevent cataract progression was examined. 5-S-GAD scavenged 1,1-diphenylpicrylhydrazyl (DPPH) and superoxide anions (O(2)(*)(-)), and inhibited lipid peroxidation. It also significantly inhibited the onset of glucocorticoid-induced lens opacification in chick embryos. These effects of 5-S-GAD were stronger than those of N-acetylcarnosine and TEMPOL, which are reported to be effective radical scavengers in the prevention of cataract progression. 5-S-GAD clearly delayed the maturation of cataracts induced by diamide in cultured lenses of rats. Daily instillation of 5-S-GAD retarded the development of lens opacity in galactose-fed rats. Biochemical analysis of the lenses revealed that 20-kDa proteins, presumably consisting of alpha-crystallin, were the most susceptible to oxidative stress, which leads to the carbonylation of the side chains of these proteins. alpha-Crystallin carbonylation induced by diamide or galactose was notably inhibited by 5-S-GAD in a dose-dependent manner. Our results show that 5-S-GAD prevents acute lens opacification in these short-term experimental models, possibly in part by virtue of its antioxidative property, and 5-S-GAD is expected to have long-term pharmaceutical effects.

Clinical detection of precataractous lens protein changes using dynamic light scattering

OBJECTIVE

To use dynamic light scattering to clinically assess early precataractous lens protein changes.

METHODS

We performed a cross-sectional study in 380 eyes of 235 patients aged 7 to 86 years with Age-Related Eye Disease Study clinical nuclear lens opacity grades 0 to 3.8. A dynamic light-scattering device was used to assess alpha-crystallin, a molecular chaperone protein shown to bind other damaged lens proteins, preventing their aggregation. The outcome measure was the alpha-crystallin index, a measure of unbound alpha-crystallin in each lens. The association of the alpha-crystallin index with increasing nuclear opacity and aging was determined.

RESULTS

There was a significant decrease in the alpha-crystallin index associated with increasing nuclear lens opacity grades (P < .001). There were significant losses of alpha-crystallin even in clinically clear lenses associated with aging (P < .001). The standard error of measurement was 3%.

CONCLUSIONS

Dynamic light scattering clinically detects alpha-crystallin protein loss even in clinically clear lenses. alpha-Crystallin index measurements may be useful in identifying patients at high risk for cataracts and as an outcome variable in clinical lens studies.

CLINICAL RELEVANCE

The alpha-crystallin index may be a useful measure of the protective alpha-crystallin molecular chaperone reserve present in a lens, analogous to creatinine clearance in estimating renal function reserve.

Effect of two different UVA doses on the rabbit cornea and lens

The aim of the present paper was to examine the irradiation effect of two doses of UVA rays (365 nm) on the rabbit cornea and lens. Corneas of anesthetized adult albino rabbits were irradiated with UVA rays for 5 days (daily dose 1.01 J cm(-2) in one group of rabbits and daily dose 2.02 J cm(-2) in the second group of animals). The third day after the last irradiation, the rabbits were killed, and their eyes were employed for spectrophotometrical, biochemical and immunohistochemical investigations. Normal eyes served as controls. Absorption spectra of the whole corneal centers were recorded over the UV-VIS (visible) spectral range. Levels of antioxidant and prooxidant enzymes, nitric oxide synthases and nitric oxide (indirectly measured as nitrate concentration) were investigated in the cornea. Malondialdehyde, a byproduct of lipid peroxidation, was examined in the cornea and lens. The results show that the staining for endothelial nitric oxide synthase was more pronounced in corneas irradiated with the higher UVA dose. Otherwise, UVA rays at either dose did not significantly change corneal light absorption properties and did not cause statistically significant metabolic changes in the cornea or lens. In conclusion, UVA rays at the employed doses did not evoke harmful effects in the cornea or lens.

Towards automatic grading of nuclear cataract

Objective quantification of lens images is essential for cataract assessment and treatment. In this paper, bottom-up and top-down strategies are combined to detect the lens contour from the slit-lamp images. The center of the lens is localized by horizontal and vertical intensity profile clustering and the lens contour is estimated by fitting an ellipse. A modified active shape model (ASM) is further applied to detect the contour of the lens. The average intensity inside the lens is employed as the indicator of nuclear opacity. The relationship between our automated nuclear cataract assessment and the clinical grading is analyzed. The preliminary study of forty images shows that the difference between automatic grading and clinical grading is acceptable.

Acute effects of cigarette smoking on multifocal electroretinogram

BACKGROUND

Cigarette smoking was shown to have stimulant effects on pattern visual-evoked potentials. The aim of this study was to investigate the acute effects of cigarette smoking on multifocal electroretinogram (mfERG).

METHODS

This prospective case-control study was held in a tertiary referral centre in Turkish Armed Forces. mfERGs were investigated in a group of habitual smokers (30 right eyes of 30 subjects) in separate real smoking and sham smoking sessions. mfERG responses of the subjects were recorded after overnight abstinence. The responses were averaged over five retinal regions, the central hexagon (CH; central 6 degrees) and four concentric rings (ring 1 [R1; 7-12 degrees], ring 2 [R2; 13-18 degrees], ring 3 [R3; 19-24 degrees], ring 4 [R4; 25-30 degrees]). On each session mfERGs were recorded before (BS) and after smoking (AS) conditions.

RESULTS

Regarding P1 amplitudes (first positive deflection of the mfERG) in the real smoking sessions, the differences were significant in the CH (BS: 66.2 +/- 16.3 microV, AS: 73.3 +/- 19.6 microV, P < 0.001), in R1 (BS: 44.3 +/- 13.0, AS: 48.3 +/- 16.0, P = 0.004) and in R2 (BS: 30.1 +/- 8.3, AS: 33.7 +/- 9.7, P = 0.002). Similar results were found for N1 amplitudes and P1 and N1 (first negative deflection of the mfERG) latencies in the CH, R1 and R2. The differences in outer retinal areas (R3, R4) in the real smoking sessions and in all rings in the sham smoking sessions were not significant.

CONCLUSION

Cigarette smoking may stimulate the central retinal areas in the acute phase. This effect may be related with the stimulant effect of nicotine on neurotransmission, deleterious effects on retinal and/or choroidal circulation, carbon monoxide toxicity and nicotine withdrawal.

Effect of inhaled corticosteroids on risk of development of cataract: a meta-analysis

The objective of this study was to quantify the risk of cataract among users of inhaled corticosteroids (ICS). Studies that examined the association of ICS use with risk of cataract were identified through computerized (MEDLINE, EMBASE), manual searches using Index Medicus, and checking cross-references to recover all published articles and scientific session abstracts. Pooled odds ratio (OR) with 95% confidence intervals (CI) were estimated using two methods, fixed effects Mantel-Haenszel model and random effects DerSimonian-Laird model. Four studies satisfied all the inclusion/exclusion criteria and were included in the analysis. The pooled OR (95% CI) by the Mantel-Haenszel method was 1.48 (1.39-1.57) and by the DerSimonian-Laird method was 1.48 (1.30-1.68). The test for heterogeneity was not significant. A total number of nine negative studies would be required to make the results of our meta-analysis non-significant. Number needed to harm is 16 with 95% CI of 13-19. Contrary to popular belief, inhaled ICS may be associated with systemic side effects like cataract as shown by this meta-analysis. The risk of increased cataract shown in our analysis needs to be weighted against the benefits of ICS. Further evaluations are required to clarify the causal association between the dosage and duration of drug use.

Maximum tolerable dose for avoidance of cataract induced by ultraviolet radiation-B for 18 to 60 week old rats

The purpose of the present study was to investigate the maximum tolerable dose for avoidance of UVR-B-induced cataract in rats in the age interval 18-60 weeks and establish the functional relationship between age and sensitivity to UVR-B. Four groups of 20 albino Sprague-Dawley rats each, aged 18, 26, 40 or 60 weeks, were included. Each age group was divided into five UVR dose sub-groups. The rats were unilaterally exposed to ultraviolet radiation (lambda(max)=302.6 nm, lambda0.5=4.5 nm). The incident dose on the cornea varied between 0 and 9.2 kJ m(-2). One week after exposure, the rats were sacrificed and both lenses were extracted. The intensity of forward light scattering was measured and photographs were taken. The functional relationship between age and sensitivity to UVR-B was estimated as the maximum tolerable dose based on rats age from 3 to 60 weeks. The maximum tolerable dose for 18, 26, 40, and 60 weeks, respectively, was estimated to 5.2, 4.9, 4.7, and 5.1 kJ m(-2). The sensitivity to UVR-B for Sprague-Dawley rats increases with increasing age during the first third of the rat life span, and then stabilizes to a constant level during the remaining two-thirds.

Transparency and non-refractive functions of crystallins--a proposal

Based on the premise that all crystallins have cellular and metabolically relevant catalytic activities, we propose that aberrant changes in non-crystallin (non-refractive) functions presage the appearance of cataractous pathologies in an otherwise highly stable edifice of transparency. This proposal is based on accumulating evidence from developmental, molecular and genetic studies that have established that crystallins are more than inanimate building blocks of the transparent lens fiber mass. The published work does not support the perceived dichotomy in the relevance of crystallin function (as essential) and non-crystallin function (as either of secondary importance or not essential at all), to the emergence and maintenance of the phenotype of transparency. A number of crystallin mutations have stage-specific phenotypes at developmental times when their concentrations have not reached 'crystallin' (high) proportions. There is heterogeneity in the cataract phenotypes associated with similar or identical mutations in different populations; the cataracts have disparate phenotypes even when the mutations are in the same gene. These data suggest that non-crystallin function is not merely a non-lens activity of a crystallin but an essential requirement within the lens itself.

Cataract formation and prevention

Cataract, a leading cause of blindness worldwide, is a multifactorial eye disease. In developing countries the incidence of cataract among young generations is not uncommon due to malnutrition, excess exposure to ultraviolet radiation and so on. In developed countries, age-related cataract affecting the population over 65 years of age is a major concern. Oxidative stress was suggested to inflict damage to the lens and induce opacification, and a variety of antioxidant nutrients were tested for the prevention or delay of cataract development. Although promising results were obtained in animal studies of various antioxidants, epidemiological studies on human populations do not seem to support their protective effects unequivocally. It is unlikely that age-related cataract in man, similar to the ageing process itself, will be prevented or delayed by therapeutic drugs in the foreseeable future. At present, keeping a health-conscious life style (i.e., no smoking) may be the most effective and least expensive strategy to prevent the onset of age-related cataract.

Effects of moderate smoking on the central visual field

PURPOSE

To investigate whether moderate cigarette smoking has any effects on the central visual field.

METHODS

This study included 30 healthy, moderate cigarette smokers (10-20 cigarettes per day for at least the past 5 years) and 22 healthy non-smokers. After two training test sessions, all individuals underwent computerized visual field examinations (Humphrey 30-2 Full Threshold Test) with both white-on-white (W-W) perimetry and blue-on-yellow (B-Y) perimetry. One eye of each subject with reliable visual field test results was evaluated. The foveal threshold, mean deviation (MD), pattern standard deviation (PSD), short-term fluctuation (SF), corrected pattern standard deviation (CPSD), glaucoma hemifield test (GHT) and number of significantly depressed points deviating at p < 5%, p < 2%, p < 1% and p < 0.5% on the pattern deviation probability map of the smokers were compared with those of the non-smokers.

RESULTS

When the results of W-W perimetry were analysed, the smokers were found to have significantly lower foveal thresholds (p = 0.001) and mean retinal sensitivity (p = 0.02), and higher PSD (p = 0.002) and CPSD (p = 0.01) than the non-smokers. Short-term fluctuation was similar in both groups (p = 0.55). The number of significantly depressed points deviating at p < 5%, p < 2% and p < 1% on the pattern deviation probability map was similar for both groups (p > 0.05). The number of depressed points deviating at p < 0.5% on the pattern deviation probability map was higher for the smokers than for the non-smokers (p = 0.03). The results of B-Y perimetry showed the smokers to have a significantly lower foveal threshold than the non-smokers (p = 0.03). However, there were no significant differences in the global indices of the two groups (p > 0.05). The number of significantly depressed points deviating at p < 5%, p < 2%, p < 1% and p < 0.5% on the pattern deviation probability map was similar in both groups (p > 0.05). No significant difference in GHT was determined with either perimetry for the smokers compared with the non-smokers (p > 0.05).

CONCLUSION

This study suggests that moderate cigarette smoking is associated with both diffuse and localized reductions in retinal sensitivity with W-W perimetry. Only reduction in the foveal threshold was observed with B-Y perimetry, with no hints of diffuse and localized reductions.

Evidence of octacalcium phosphate and Type-B carbonated apatites deposited on the surface of explanted acrylic hydrogel intraocular lens

Fourier-transform infrared (FTIR) microspectroscopy combining with attenuated total reflection (ATR) microsampling technique and micro-Raman spectrophotometer were used to detect the deposited materials on the surface of acrylic hydrogel intraocular lens (IOL) with or without ocular implantation. Surface morphology and the interface of this IOL were further examined by a confocal laser scanning microscope. The brand-new IOL exhibited a very smooth, transparent and featureless surface, but the explanted IOL had an irregular cerebriform-like opaque appearance. Both FTIR/ATR and Raman microspectroscopic analyses showed the deposits on the surface of acrylic hydrogel IOL after ocular implantation to consist of octacalcium phosphate (OCP) and Type B carbonated apatites, leading to the opalescence of acrylic hydrogel IOL. Both vibrational microspectroscopic examinations also confirmed the mineralization still in progress on the surface of acrylic hydrogel IOL after ocular implantation for 2 years.

Tempol-H inhibits opacification of lenses in organ culture

Cataract is the world's leading cause of blindness and a disease for which no efficacious medical therapy is available. To screen potential anti-cataract agents, a lens organ culture model system was used. Opacification of lenses maintained in culture was induced by specific insults including H(2)O(2) or the cataractogenic sugar xylose. Potential anti-cataract agents were added to the culture medium and their ability to inhibit opacification and certain biochemical changes associated with the opacification were assessed. Among the compounds tested, Tempol-H, the hydroxylamine of the nitroxide Tempol, gave the most promising results. It significantly inhibited opacification of rat lenses in an H(2)O(2)-induced cataract system as well as opacification of rhesus monkey lenses induced by xylose. Tempol-H inhibited the loss of glutathione, the leakage of protein, and decreases in the ability of cultured lenses to accumulate (3)H-choline from the medium, all of which were associated with the development of lens opacification. The antioxidative activity of Tempol-H and its ability to re-dox cycle make it an attractive candidate as a therapeutic agent for the prevention of aging-related cataract.

Crystallins, genes and cataract

Far from being a physical entity, assembled of inanimate structural proteins, the ocular lens epitomizes the biological ingenuity that sustains an essential and near-perfect physical system of immaculate optics. Crystallins (alpha, beta, and gamma) provide transparency by dint of their high concentration, but it is debatable whether proteins that provide transparency are any different, biologically or structurally, from those that are present in non-transparent structures or tissues. It is becoming increasingly clear that crystallins may have a plethora of metabolic and regulatory functions, both within the lens as well as outside of it. Alpha-crystallins are members of a small heat shock family of proteins and beta/gamma-crystallins belong to the family of epidermis-specific differentiation proteins. Crystallin gene expression has been studied from the perspective of the lens specificity of their promoters. Mutations in alpha-, beta-, and gamma-crystallins are linked with the phenotype of the loss of transparency. Understanding catalytic, non-structural properties of crystallins may be critical for understanding the malfunction in molecular cascades that lead to cataractogenesis and its eventual therapeutic amelioration.