Lens autofluorescence and light scatter in relation to the lens opacities classification system, LOCS III

Automatic Segmentation of Retinal Layers in Multiple Neurodegenerative Disorder Scenarios

Retinal Optical Coherence Tomography (OCT) allows the non-invasive direct observation of the central nervous system, enabling the measurement and extraction of biomarkers from neural tissue that can be helpful in the assessment of ocular, systemic and Neurological Disorders (ND). Deep learning models can be trained to segment the retinal layers for biomarker extraction. However, the onset of ND can have an impact on the neural tissue, which can lead to the degraded performance of models not exposed to images displaying signs of disease during training. We present a fully automatic approach for the retinal layer segmentation in multiple neurodegenerative disorder scenarios, using an annotated dataset of patients of the most prevalent NDs: Alzheimer's disease, Parkinson's disease, multiple sclerosis and essential tremor, along with healthy control patients. Furthermore, we present a two-part, comprehensive study on the effects of ND on the performance of these models. The results show that images of healthy patients may not be sufficient for the robust training of automated segmentation models intended for the analysis of ND patients, and that using images representative of different NDs can increase the model performance. These results indicate that the presence or absence of patients of ND in datasets should be taken into account when training deep learning models for retinal layer segmentation, and that the proposed approach can provide a valuable tool for the robust and reliable diagnosis in multiple scenarios of ND.

Visual Acuity Prior to Cataract Surgery and Risk of Retinal Detachment - A Population-Based Study

Purpose

To analyze preoperative visual acuity before cataract surgery regarding the risk of rhegmatogenous retinal detachment (RRD) after cataract surgery.

Methods

The preoperative visual acuity in an observational cohort study of patients undergoing cataract surgery in Skåne, southern Sweden, during 2015-2017 was analyzed with data retrieved from the Swedish National Cataract Register. This was then cross-referenced with patients undergoing surgery for retinal detachment at the Skåne University Hospital in Lund from 2015 to 2020. The main outcome was the risk-benefit ratio of measuring preoperative visual acuity before cataract surgery and the risk of RRD.

Results

The mean visual acuity in the whole study group (N=58,624), expressed as LogMAR, was 0.40 ± 0.32 (SD). In the group with RRD (n=298), the mean visual acuity was 0.44 ± 0.36 (p=0.07). In the subgroups of RRD, those aged <60 years 0.49 ± 0.44 (p=0.07), aged <60 years and axial length (AL) >25 mm 0.42 ± 0.38 (p=0.68), and in those aged <60 years, AL >25 mm and male sex 0.44 ± 0.39 (p=0.53). However, there is considerable variations in visual acuity of the various groups and in the high-risk group with RRD aged <60 years with AL>25 mm, 15% had a visual acuity of 0.8 or better in the operated eye.

Conclusion

There must be strong indications for performing cataract surgery in those with a high risk of retinal detachment, and the patient must be given adequate information on the risk of retinal detachment.

[Spectrofluorimetric changes in the lens after intravitreal injections of brolucizumab]

Intravitreal injections (IVI) of vascular endothelial growth factor (VEGF) inhibitors are actively used in the treatment of various ophthalmic pathologies. In addition to the pronounced therapeutic effect of anti-VEGF drugs described in the literature, a number of data on adverse effects associated with the use of IVI, including from the lens, have now been accumulated. Prevention of possible side effects of this type of treatment requires further investigation.

PURPOSE

The study evaluates the changes in spectrofluorometric parameters of the lens after intravitreal injections of brolucizumab in eyes with native lens.

MATERIAL AND METHODS

The study included 13 people with neovascular age-related macular degeneration (AMD) who received IVI of brolucizumab. All patients were over 40 years old; changes in central retinal thickness in the macular area exceeded 300 μm according to optical coherence tomography. Spectrofluorimetric indicators of the lens were studied before and after injections of the drug in both eyes. The spectra were analyzed in the wavelength range 412-698 nm to record the changes in the content of non-tryptophan fluorophore molecules in the lens.

RESULTS

Spectrofluorimetry revealed metabolic changes in the native lens after intravitreal injections of the drug brolucizumab. No such changes were observed in the lens of the eyes not injected with the drug (the «Control» group). The proposed investigation technique involves prospective assessment of the safety of various molecules injected intravitreally in terms of cataract development at various times after the injection.

CONCLUSION

Spectrofluorimetry can be used for identifying initial metabolic changes in the lens. It is a promising method for assessing the molecules used in intravitreal injections in terms of their safety for the native lens, as well as for development of detailed instructions for clinically substantiated use of drugs with adverse effects in the form of cataract induction. According to spectrofluorimetry, IVI of the drug brolucizumab affects metabolic changes in the lens.

Investigation of the association between lens autofluorescence ratio and diabetes: a cross-sectional study

AIMS/HYPOTHESIS

Lens autofluorescence ratio (LFR) is a novel approach to detect advanced glycation end products in a time-saving and non-invasive manner. However, its associations with glycemia and diabetes remain unclear. We conducted this study to address this issue in Chinese adults.

METHODS

We enrolled a total of 4,705 participants aged 20-70 years in China between May 2020 and January 2021 in a cross-sectional study. LFR was determined by biomicroscopy (ClearPath DS-120). Diabetes was ascertained by oral glucose tolerance test, self-reported history, and/or antidiabetic medication use. Correlation and logistic regression analyses were performed.

RESULTS

LFR was higher in participants with diabetes than those without (23.27 ± 6.51 vs. 19.45 ± 5.08, p < 0.001). LFR correlated with fasting plasma glucose and hemoglobin A1c in the overall and diabetes-stratified populations. The odds of diabetes was increased by 6% per one percent higher of LFR after multivariable-adjustment (odds ratio (OR) 1.06, 95% CI 1.04-1.08, p < 0.001). Participants in the highest quartile of LFR had higher odds of diabetes compared with those in the lowest quartile (OR 1.83, 95% CI 1.33-2.52, p < 0.001). Mediation analysis showed that, insulin resistance, as assessed by triglyceride-glucose index, may underline the relationship between high LFR and increased odds of diabetes.

CONCLUSIONS

LFR, a non-invasive indirect measure of advanced glycation end products, appears to be associated with glycemia and the risk of developing diabetes in Chinese adults.

The Influence of Intraocular Lens Implantation and Alterations in Blue Light Transmittance Level on the Brain Functional Network Architecture Reorganization in Cataract Patients

BACKGROUND

Cataract is one of the most common age-related vision deteriorations, leading to opacification of the lens and therefore visual impairment as well as blindness. Both cataract extraction and the implantation of blue light filtering lens are believed to improve not only vision but also overall functioning.

METHODS

Thirty-four cataract patients were subject to resting-state functional magnetic resonance imaging before and after cataract extraction and intraocular lens implantation (IOL). Global and local graph metrics were calculated in order to investigate the reorganization of functional network architecture associated with alterations in blue light transmittance. Psychomotor vigilance task (PVT) was conducted.

RESULTS

Graph theory-based analysis revealed decreased eigenvector centrality after the cataract extraction and IOL replacement in inferior occipital gyrus, superior parietal gyrus and many cerebellum regions as well as increased clustering coefficient in superior and inferior parietal gyrus, middle temporal gyrus and various cerebellum regions. PVT results revealed significant change between experimental sessions as patients responded faster after IOL replacement. Moreover, a few regions were correlated with the difference in blue light transmittance and the time reaction in PVT.

CONCLUSION

Current study revealed substantial functional network architecture reorganization associated with cataract extraction and alteration in blue light transmittance.

Lens fluorescence and skin fluorescence in the Copenhagen Twin Cohort Eye Study: Covariates and heritability

Lens and skin fluorescence are related to the systemic accumulation of advanced glycation end products, which is accelerated in diabetes. We have examined lens fluorescence and skin fluorescence in healthy adult twins. The study enrolled twins aged median 59 years from a national population-based registry. Diabetic individuals were excluded from analysis. The interrelatedness between fluorescence parameters and relations between fluorescence and age, current HbA1c and smoking pack years were examined using correlation tests and mixed model linear regression analyses. Broad-sense heritability was analyzed and compared for lens fluorescence, skin fluorescence and HbA1c. Lens fluorescence and skin fluorescence were crudely interrelated (R = 0.38). In linear regression analyses, age explained a larger fraction of the variance in lens fluorescence (R2 = 32%) than in skin fluorescence (R2 = 20%), whereas HbA1c explained smaller variance fractions (R2 = 3% and 8%, respectively) followed by smoking pack years (4% and 3%, respectively). In multivariate analyses, age, HbA1c and smoking pack years combined explained more of the variance in lens fluorescence (R2 = 35%) than in skin fluorescence (R2 = 21%), but the influence of HbA1c on lens fluorescence was not statistically significant (p = .2). Age-adjusted broad-sense heritability was 85% for lens fluorescence, 53% for skin fluorescence and 71% for HbA1c in best fitting heritability models. Both fluorescence parameters increased with age, current glycemia and cumulative smoking. Lens fluorescence was found to be a predominantly heritable trait, whereas skin fluorescence was more influenced by environmental factors and closer related to current glycemia. The results suggest that skin fluorophores have a faster turn-over than lens fluorophores.

Macular Pigment Response to Lutein, Zeaxanthin, and Meso-zeaxanthin Supplementation in Open-Angle Glaucoma

Purpose

To evaluate macular pigment response to carotenoid supplementation in glaucomatous eyes.

Design

Double-masked, randomized, placebo-controlled clinical trial, the European Nutrition in Glaucoma Management Study (ClinicalTrials.gov identifier, NCT04460365).

Participants

Sixty-two participants (38 men, 24 women) with a diagnosis of open-angle glaucoma were enrolled. Forty-two were randomized to receive the active supplement, 20 participants were allocated to placebo.

Methods

Macular pigment optical density (MPOD) was measured by autofluorescence using the Heidelberg Spectralis scanning laser ophthalmoscope. Macular pigment optical density volume within the central 6° of retinal eccentricity as well as MPOD at 0.23°, 0.51°, 0.74°, and 1.02° were recorded at baseline and at 6-month intervals over 18 months. Visual function was assessed using visual acuity, mesopic and photopic contrast sensitivity under glare conditions, photo stress recovery time, microperimetry, and Glaucoma Activities Limitation 9 questionnaire. Advanced glaucoma module scans of retinal nerve fiber layer thickness and ganglion cell complex thickness over the central 6° of retinal eccentricity also were completed at each study visit.

Main Outcome Measures

Change in MPOD after supplementation with 10 mg lutein, 2 mg zeaxanthin, and 10 mg meso-zeaxanthin or placebo over 18 months.

Results

A mixed-model repeated measures analysis of variance revealed a statistically significant increase in MPOD volume (significant time effect: F(3,111) = 89.31, mean square error (MSE) = 1656.9; P < 0.01). Post hoc t tests revealed a significant difference in MPOD volume at each study visit for the treatment group (P < 0.01 for all), but no change in the placebo group (P > 0.05 for all). A statistically significant increase in mesopic contrast sensitivity under glare conditions was noted at 18 months in the treatment group, but not placebo. No other structural or functional changes were observed. No serious adverse events were noted during the trial.

Conclusions

Macular pigment can be augmented in glaucomatous eyes by supplementation with a formulation containing the carotenoids lutein, zeaxanthin, and meso-zeaxanthin. The greatest relative benefit was observed in those with the lowest baseline levels, but increases were noted across all participants and each retinal eccentricity. The potential benefits of MP augmentation for macular health in glaucoma merit further long-term evaluation.

Axial Length Change in Pseudophakic Eyes Measured by IOLMaster 700

Purpose

The purpose of this study was to investigate the change in axial length (AL) after cataract surgery measured by swept source optical coherence tomography (IOLMaster 700), and explore ways to eliminate this AL measurement error in pseudophakic eyes.

Methods

Patients with cataract who underwent unilateral phacoemulsification with four types of intraocular lens (IOLs) implantation (Asphina 509M, Tecnis PCB00, enVista MX60, and Acrysof SN60WF) were enrolled. Bilateral AL measurements were performed before and 1 month after cataract surgery utilizing IOLMaster 700. The postoperative AL of the operated eye was evaluated using three different modes (phakic, aphakic, and pseudophakic), and the fellow eye was measured by phakic mode. Associations among the AL change and cataract grade, lens thickness, preoperative AL, or refractive index of IOL were investigated using stepwise multivariate linear regression.

Results

A total of 305 patients with cataract with mean age of 65.97 ± 13.39 years were recruited. The mean postoperative AL was 0.10 mm and 0.21 mm shorter than the pre-operative AL utilizing pseudophakic and phakic modes, respectively (P < 0.001). No significant difference was observed between pre-operative and postoperative AL using aphakic mode (P = 0.264). There were no significant associations among AL change in pseudophakic eye and cataract grade, lens thickness, pre-operative AL, or refractive index of IOL (P > 0.05).

Conclusions

A correction factor of 0.10 mm is suggested to eliminate AL measurement error of IOLMaster 700 in pseudophakic eyes before further improvement of AL measurement accuracy.

Translational Relevance

Our study may help to eliminate the AL measurement error of IOLMaster 700 in pseudophakic eyes.

Influence of lens opacities and cataract severity on quantitative fundus autofluorescence as a secondary outcome of a randomized clinical trial

The aim of this study is to investigate the impact of age-related lens opacities and advanced cataract, quantified by LOCS III grading, on quantitative autofluorescence (qAF) measurements in patients before and after cataract surgery. Images from a randomized controlled trial evaluating the impact of femtosecond-laser assisted cataract surgery (FLACS) on retinal thickness were analyzed post-hoc. One-hundred and twenty eyes from 60 consecutive patients with age-related cataract were included and assessed with qAF and optical coherence tomography (OCT) before, 1, 3 and 6 weeks after cataract surgery (randomized 1:1 to FLACS or phacoemulsification). LOCS III grading was performed before surgery. Pre- to post-surgical qAF values, as well as the impact of LOCS III gradings, surgery technique, gender, axial length and age on post-surgery qAF values was investigated using generalized linear mixed models. For this analysis, 106 eyes from 53 patients were usable. No difference in qAF was found between FLACS and phacoemulsification (p > 0.05) and results were pooled for the total cohort. Mean pre-surgical qAF was 89.45 ± 44.9 qAF units, with a significant mean increase of 178.4–191.6% after surgery (p < 0.001). No significant difference was found between the three follow-up visits after surgery (p > 0.05). Higher LOCS III cortical opacity quantifications were associated with a significantly greater increase in qAF after surgery (estimate: 98.56, p = 0.006) and nuclear opacities showed a trend toward an increased change (estimate: 48.8, p = 0.095). Considerable interactions were identified between baseline qAF and cortical opacities, nuclear opacities and posterior subcapsular opacities, as well as nuclear opacities and cortical opacities (p = 0.012, p = 0.064 and p = 0.069, respectively). Quantitative autofluorescence signals are significantly reconstituted after cataract surgery and LOCS III gradings are well associated with post-surgical qAF values. Careful consideration of age-related lens opacities is vital for the correct interpretation of qAF, especially in retinal diseases affecting the elderly.

ClinicalTrials.gov Identifier: NCT03465124.

Up-Regulation of GATA4 Regulates Human Lens Epithelial Cell Function in Age-Related Cataract

PURPOSE

GATA4 has emerged as a novel regulator that plays a critical role in mediating senescence. However, the role of GATA4 in age-related cataract (ARC), the leading cause of visual impairment, requires further elucidation.

METHODS

GATA4 expression was measured by quantitative RT-PCR and capillary Western immunoassay (WES). The MTT assay, EdU assay, and rhodamine-123/Hoechst and calcein-AM/propidium iodide double staining were used to investigate the role of GATA4 in the viability, proliferation, and apoptosis of cultured human lens epithelial cells (HLECs).

RESULTS

HLECs were subjected to 3 different treatment models, including prolonged exposure to low-dose H2O2, UVB irradiation, and mild heating, to simulate senescence and apoptosis. GATA4 expression was significantly increased in these models in a time- and dose-dependent manner. Overexpression of GATA4 reduced cell viability, accelerated apoptosis development, and reduced the proliferation of HLECs. Furthermore, the expression of GATA4 from ARC was up-regulated at both mRNA and at protein level compared with clear lenses.

CONCLUSION

GATA4 is up-regulated in all 3 models of HLECs in vitro and the cells from ARC lenses in vivo. Up-regulation of GATA4 mediates HLEC dysfunction. GATA4-mediated effects in HLECs would provide a novel insight into the pathogenesis of ARC.

Video recording and light intensity change analysis during cataract surgery using an animal model

PURPOSE

To estimate light exposure changes during cataract surgery through intraoperative images simulated from the "patient's perspective" using an animal model.

METHODS

In this experimental study, a 3-mm maculostomy was performed through the posterior globe's surface of 15 porcine eyes. Eyes were fixated to a glass slide and placed over an iPad camera. Video footage of a cataract surgery was obtained through the maculostomy for each eye, keeping light exposure parameters and focus constant. Seventy-five images, five from each eye, were extracted at pre-determined points, and mean gray value (MGV), a light intensity measure, was calculated. Differences in MGV between discrete surgical steps were evaluated using multiple one-sample t-tests.

RESULTS

This technique allowed for the capture of a full-length cataract surgery through a 3-mm maculostomy. MGV range was 14.21-132.51. Light intensity was similar across surgeries and varied greatly through each procedure. A 24% decrease in MGV between post-hydrodissection and post-phacoemulsification stages was noted (difference - 18.36; 95% CI - 30.50 to - 6.22; p value = 0.006). A 22.4% decrease in light intensity was noted after phacoemulsification in comparison to the starting image (MGV difference - 16.78; 95% CI - 32.45 to - 1.12; p value: 0.0375). Light intensity was similar at the start and end of surgery (difference - 7.15; 95% CI - 19.35 to + 5.05; p value = 0.229).

CONCLUSIONS

Light intensity changes through different steps of cataract surgery and may be minimal after phacoemulsification completion. This video and data may serve as informational and educational tools for surgeons and patients.

Imaging Lenticular Autofluorescence in Older Subjects

Purpose

To evaluate whether a practical method of imaging lenticular autofluorescence (AF) can provide an individualized measure correlated with age-related lens yellowing in older subjects undergoing tests involving shorter wavelength lights.

Methods

Lenticular AF was imaged with 488-nm excitation using a confocal scanning laser ophthalmoscope (cSLO) routinely used for retinal AF imaging. There were 75 older subjects (ages 47–87) at two sites; a small cohort of younger subjects served as controls. At one site, the cSLO was equipped with an internal reference to allow quantitative AF measurements; at the other site, reduced-illuminance AF imaging (RAFI) was used. In a subset of subjects, lens density index was independently estimated from dark-adapted spectral sensitivities performed psychophysically.

Results

Lenticular AF intensity was significantly higher in the older eyes than the younger cohort when measured with the internal reference (59.2 ± 15.4 vs. 134.4 ± 31.7 gray levels; P < 0.05) as well as when recorded with RAFI without the internal reference (10.9 ± 1.5 vs. 26.1 ± 5.7 gray levels; P < 0.05). Lenticular AF was positively correlated with age; however, there could also be large differences between individuals of similar age. Lenticular AF intensity correlated well with lens density indices estimated from psychophysical measures.

Conclusions

Lenticular AF measured with a retinal cSLO can provide a practical and individualized measure of lens yellowing, and may be a good candidate to distinguish between preretinal and retinal deficits involving short-wavelength lights in older eyes.

Expression of DNA repair genes in lens cortex of age-related cortical cataract

The formation and development of age-related cataract (ARC) has been demonstrated to have the involvement of defective DNA repair in lens epithelial cells (LECs). This study aimed to investigate DNA repair genes expression in human lens cortex collected from age-related cortical cataract (ARCC) and controls during surgery. The expression levels of the genes were evaluated by xx genes microarray analysis. The results were further confirmed by Quantitative Real-Time PCR (qRT-PCR). The mRNA levels of 7 genes decreased and 4 genes out of 92 genes increased in lens cortex of ARCCs compared with controls with the fold change >1.5. Using Comet assay, we found the DNA breaks in the LECs of ARCCs were obviously severer than that of controls. The present data provide a global perspective on expression of DNA repair genes that may contribute to cataract pathogenesis. The DNA damage and repair pathway might be an effective target to delay the onset of ARC.

Indication for cataract surgery. Do we have evidence of who will benefit from surgery? A systematic review and meta-analysis

The need for cataract surgery is expected to rise dramatically in the future due to the increasing proportion of elderly citizens and increasing demands for optimum visual function. The aim of this study was to provide an evidence-based recommendation for the indication of cataract surgery based on which group of patients are most likely to benefit from surgery. A systematic literature search was performed in the MEDLINE, CINAHL, EMBASE and COCHRANE LIBRARY databases. Studies evaluating the outcome after cataract surgery according to preoperative visual acuity and visual complaints were included in a meta-analysis. We identified eight observational studies comparing outcome after cataract surgery in patients with poor (<20/40) and fair (>20/40) preoperative visual acuity. We could not find any studies that compared outcome after cataract surgery in patients with few or many preoperative visual complaints. A meta-analysis showed that the outcome of cataract surgery, evaluated as objective and subjective visual improvement, was independent on preoperative visual acuity. There is a lack of scientific evidence to guide the clinician in deciding which patients are most likely to benefit from surgery. To overcome this shortage of evidence, many systems have been developed internationally to prioritize patients on waiting lists for cataract surgery, but the Swedish NIKE (Nationell Indikationsmodell för Katarakt Ekstraktion) is the only system where an association to the preoperative scoring of a patient has been related to outcome of cataract surgery. We advise that clinicians are inspired by the NIKE system when they decide which patients to operate to ensure that surgery is only offered to patients who are expected to benefit from cataract surgery.

Sleep disturbances are related to decreased transmission of blue light to the retina caused by lens yellowing

STUDY OBJECTIVES

Sleep pattern and circadian rhythms are regulated via the retinohypothalamic tract in response to stimulation of a subset of retinal ganglion cells, predominantly by blue light (450-490 nm). With age, the transmission of blue light to the retina is reduced because of the aging process of the human lens, and this may impair the photoentrainment of circadian rhythm leading to sleep disorders. The aim of the study was to examine the association between lens aging and sleep disorders.

DESIGN

Cross-sectional population based study.

SETTING

The study was performed at the Research Center for Prevention and Health, Glostrup Hospital, Denmark and at the Department of Ophthalmology, Herlev Hospital, Denmark.

PARTICIPANTS

An age- and sex-stratified sample of 970 persons aged 30 to 60 years of age drawn from a sample randomly selected from the background population.

INTERVENTIONS

Not applicable.

MEASUREMENTS AND RESULTS

Sleep disturbances were evaluated by a combination of questionnaire and the use of prescription sleeping medication. Lens aging (transmission and yellowing) was measured objectively by lens autofluorometry. The risk of sleep disturbances was significantly increased when the transmission of blue light to the retina was low, even after correction for the effect of age and other confounding factors such as smoking habits, diabetes mellitus, gender, and the risk of ischemic heart disease (P < 0.0001).

CONCLUSIONS

Filtration of blue light by the aging lens was significantly associated with an increased risk of sleep disturbances. We propose that this is a result of disturbance of photoentrainment of circadian rhythms.

Lens autofluorescence is not increased at high altitude

PURPOSE

To study the relation between ambient environmental ultraviolet radiation exposure and lens fluorescence.

METHODS

Non-invasive lens fluorometry measurements were compared in healthy Bolivian and Danish subjects. Background ultraviolet radiation was 4.5 times higher in Bolivia than in Denmark.

RESULTS

No significant differences in lens fluorescence or transmittance were found between Bolivian and Danish volunteers.

CONCLUSION

Age-corrected lens fluorescence and transmittance were comparable for healthy participants living at high altitude near the equator and healthy volunteers living at sea level at 55 degrees northern latitude. These results suggest that lens ageing, as assessed by lens autofluorometry, is independent of exposure to ultraviolet radiation.

Inhibition of crystallin ascorbylation by nucleophilic compounds in the hSVCT2 mouse model of lenticular aging

PURPOSE

Senile cataracts are associated with oxidation, fragmentation, cross-linking, insolubilization, and yellow pigmentation of lens crystallins. This process is partially explained by advanced glycation end products (AGEs) from ascorbic acid (ASA), as the authors unequivocally demonstrated in an hSVCT2 transgenic mouse. The authors present the first pharmacologic intervention study against ascorbylation in these mice.

METHODS

Five groups of mice from 2 to 9 months of age (10 mice/group) were fed a diet containing 0.1% (wt/wt) aminoguanidine, pyridoxamine, penicillamine, and nucleophilic compounds NC-I and NC-II. AGEs were determined in crystallin digests using high-performance liquid chromatography, liquid chromatography-mass spectrometry, or gas chromatography-mass spectrometry. Lens protein extract was incubated in vitro with ASA or dehydroascorbic acid.

RESULTS

The ASA level increased approximately 10-fold in all groups and was unaffected by treatment. AGEs were increased several-fold in transgenic compared with control lenses. Body weight, food intake, lenticular glutathione, and glycated lysine level were unaltered. In vitro, all compounds inhibited AGE formation. In vivo, NC-I and NC-II significantly decreased protein fluorescence at lambda(ex)335/(em)385 (P = 0.045, P = 0.017, respectively) and lambda(ex)370/(em)440 (P = 0.029, P = 0.007, respectively). Other inhibitors had no effect. After 7 months, only NC-I and NC-II induced a 50% reduction in pentosidine (P = NS for NC-I; P = 0.035 for NC-II). NC-I also decreased carboxymethyllysine (P = 0.032) and carboxyethyllysine (P = NS). Fluorescent cross-link K2P was decreased by NC-I, NC-II, aminoguanidine, and pyridoxamine (P = NS).

CONCLUSIONS

Pharmacologically blocking protein ascorbylation with absorbable guanidino compounds is feasible and may represent a new strategy for the delay of age-related nuclear sclerosis of the lens.

Vitamin C-mediated Maillard reaction in the lens probed in a transgenic-mouse model

Aging human lens crystallins are progressively modified by yellow glycation, oxidation, and cross-linked carbonyl compounds that have deleterious properties on protein structure and stability. In order to test the hypothesis that some of these compounds originate from oxidized vitamin C, we have overexpressed the human vitamin C transporter 2 (hSCVT2) in the mouse lens. We find that levels of ascorbic and dehydroascorbic acid are highly elevated compared to the wild type and that the lenses have accumulated yellow color and advanced Maillard reaction products identical with those of the human lens. Treatment of the mice with nucleophilic inhibitors can slow down the process, opening new avenues for the pharmacological prevention of senile cataractogenesis.

Vitamin C mediates chemical aging of lens crystallins by the Maillard reaction in a humanized mouse model

Senile cataracts are associated with progressive oxidation, fragmentation, cross-linking, insolubilization, and yellow pigmentation of lens crystallins. We hypothesized that the Maillard reaction, which leads browning and aroma development during the baking of foods, would occur between the lens proteins and the highly reactive oxidation products of vitamin C. To test this hypothesis, we engineered a mouse that selectively overexpresses the human vitamin C transporter SVCT2 in the lens. Consequently, lenticular levels of vitamin C and its oxidation products were 5- to 15-fold elevated, resulting in a highly compressed aging process and accelerated formation of several protein-bound advanced Maillard reaction products identical with those of aging human lens proteins. These data strongly implicate vitamin C in lens crystallin aging and may serve as a model for protein aging in other tissues particularly rich in vitamin C, such as the hippocampal neurons and the adrenal gland. The hSVCT2 mouse is expected to facilitate the search for drugs that inhibit damage by vitamin C oxidation products.

Early lens aging is accelerated in subjects with a high risk of ischemic heart disease: an epidemiologic study

BACKGROUND

Ischemic heart disease (IHD) is one of the most important causes of mortality and morbidity in the Western world. There is a relationship between aging of the lens of the human eye and cardiovascular disease. The present study was conducted to examine if the risk of ischemic heart disease could be estimated by fluorophotometric assessment of lens aging.

METHODS

A total of 421 subjects were included. Risk of IHD was estimated from non-ocular data using the Precard software. Lens aging was quantified by lens fluorometry.

RESULTS

The risk of IHD was strongly related to lens fluorophore accumulation (p = 0.001). The relationship between IHD and lens aging was attributable to tobacco smoking and dysglycemia.

CONCLUSION

The risk of ischemic heart disease related to smoking and diabetes mellitus can be estimated using the aging of the lens of the eye as a biomarker for generalized tissue-damage.

Age-related nuclear cataract—oxidation is the key

Age is by far the biggest risk factor for cataract, and it is sometimes assumed that cataract is simply an amplification of this aging process. This appears not to be the case, since the lens changes associated with aging and cataract are distinct. Oxidation is the hallmark of age-related nuclear (ARN) cataract. Loss of protein sulfhydryl groups, and the oxidation of methionine residues, are progressive and increase as the cataract worsens until >90% of cysteine and half the methionine residues are oxidised in the most advanced form. By contrast, there may be no significant oxidation of proteins in the centre of the lens with advancing age, even past age 80. The key factor in preventing oxidation seems to be the concentration of nuclear glutathione (GSH). Provided that nuclear GSH levels can be maintained above 2 mm, it appears that significant protein oxidation and posttranslational modification by reactive small molecules, such as ascorbate or UV filter degradation products, is not observed. Adequate coupling of the metabolically-active cortex, the source of antioxidants such as GSH, to the quiescent nucleus, is crucial especially since it would appear that the cortex remains viable in old lenses, and even possibly in ARN cataract lenses. Therefore it is vital to understand the reason for the onset of the lens barrier. This barrier, which becomes apparent in middle age, acts to impede the flow of small molecules between the cortex and the nucleus. The barrier, rather than nuclear compaction (which is not observed in human lenses), may contribute to the lowered concentration of GSH in the lens nucleus after middle age. By extending the residence time within the lens centre, the barrier also facilitates the decomposition of intrinsically unstable metabolites and may exacerbate the formation of H(2)O(2) in the nucleus. This hypothesis, which is based on the generation of reactive oxygen species and reactive molecules within the nucleus itself, shifts the focus away from theories for cataract that postulated a primary role for oxidants generated outside of the lens. Unfortunately, due to marked variability in the lenses of different species, there appears at present to be no ideal animal model system for studying human ARN cataract.

Topical dorzolamide increases pericentral visual function in age-related maculopathy: pilot study findings with short-wavelength automated perimetry

PURPOSE

Numerous studies have confirmed the enhancement of ocular circulation by carbonic anhydrase inhibitors (CAIs). Topical CAI treatment with dorzolamide averts the significant pericentral visual function loss accompanying retinal and choroidal vasoconstriction during acute hyperventilation-induced hypocapnia. This study was designed to discern whether dorzolamide might similarly enhance macular function in patients with age-related maculopathy (ARM).

METHODS

In a masked, placebo-controlled study, 40 patients with ARM and acuity > 20/50 were randomized to receive either dorzolamide or placebo for 12 weeks, thrice daily. After pre-study perimetric training, pericentral function (mean sensitivity) was quantified using Humphrey 10-2 short-wavelength automated perimetry (SWAP), before and after 12 weeks of topical therapy.

RESULTS

Dorzolamide-treated eyes demonstrated a significant increase in mean sensitivity of + 1.55 dB (p = 0.04); placebo-treated eyes showed no significant change (+ 0.58 dB; p = 0.10). Given the non-significant increase of mean sensitivity in the placebo-treated group, fewer than 100 subjects per group would be required to afford > 70% power to yield a significant direct comparative difference between treatment and placebo in a prospective, randomized study of equally short duration.

CONCLUSIONS

This study demonstrated a significant increase in short-wavelength sensitivity in ARM with dorzolamide and the lack thereof with placebo. These encouraging pilot study data suggest a potential role for topical CAIs in ARM patients, and establish objective parameters for prospective studies to further evaluate the effects of dorzolamide in ARM.

Short-wavelength automated perimetry in patients with diabetes mellitus without macular edema

BACKGROUND

The short-wavelength-sensitive (SWS) cone-mediated sensitivity is a sensitive indicator of functional changes of the macula in diabetic maculopathy. This study was performed to investigate whether functional losses of the macula are detectable in patients without a significant macular edema.

METHODS

In 45 patients with diabetes mellitus with clear optical media and no macular edema, conventional white-on-white perimetry (WWP) and short-wavelength automated perimetry (SWAP) were performed in the central 10-deg field. Fifty-eight healthy subjects ranging in age from 16 to 62 years served as controls. The two groups did not differ in age.

RESULTS

Variance analysis (ANOVA) revealed significantly lower sensitivity in patients with diabetes than in controls. SWAP thresholds were significantly more greatly reduced by diabetes than those of WWP (ANOVA interaction: P=0.003). Post-hoc testing revealed a sensitivity reduction of 2.8 dB ( P=0.0003) in patients with diabetes for SWAP versus 0.46 for WWP ( P=0.15). Subgroup analysis revealed that mean thresholds of SWAP and WWP predominantly were reduced in patients with advanced disease. In patients with no retinopathy, sensitivity was not affected at all.

CONCLUSION

SWS sensitivity may be affected in patients with diabetic retinopathy without clinically significant macular edema. Sensitivity loss was pronounced with increasing severity of retinopathy, reflecting the global status of the eye.