Blue-Blocking IOLs vs. Short-Wavelength Visible Light: Hypothesis-Based vs. Evidence-Based Medical Practice

The Effect of Blue-light Filtering Intraocular Lenses on the Development and Progression of Macular Atrophy in Eyes With Neovascular Age-related Macular Degeneration

PURPOSE

To assess the effect of blue-light filtering (BLF) intraocular lenses (IOLs) on the development and progression of macular atrophy (MA) in eyes with neovascular age-related macular degeneration (nAMD).

DESIGN

Retrospective, clinical cohort study.

METHODS

The study included patients with nAMD with anti-vascular endothelial growth factor (VEGF) injections who underwent uneventful cataract surgery between 2007 and 2018 with follow-up until June 2023. Subsequent MA rates were compared between subjects who received a BLF IOL or a non-BLF IOL. All optical coherence tomography scans were manually reviewed in a masked manner regarding patient baseline variables and IOL status by an experienced research technician. By using Heidelberg software, the area of MA was manually evaluated and calculated (mm2) by the program. The overall risk of developing new-onset MA and the effect of IOL type on disease progression were assessed. Death was included as a censoring event.

RESULTS

Included were 373 eyes of 373 patients (mean age, 78.6 ± 6.7 years at surgery; 67.4% were female). BLF IOLs were implanted in 206 eyes, and non-BLF IOLs were implanted in 167 eyes with comparable follow-up times (3164 ± 1420 days vs 3180 ± 1403 days, respectively, P = .908) and other baseline parameters (age, gender, corrected distance visual acuity, macular thickness, cumulative number of anti-VEGF injections). Nine preexisting and 77 new-onset MA cases were detected, with similar distribution between BLF and non-BLF eyes (P = .598 and P = .399, respectively). Both univariate Kaplan-Meier (P = .366) and multivariate Cox regression analyses adjusted for age and gender showed that BLF-IOLs were comparable to non-BLF IOLs regarding hazard for new-onset MA (hazard ratio [HR], 1.236; 95% CI, 0.784-1.949; P = .363). Final MA area at the last visit was 5.14 ± 4.71 mm2 for BLF IOLs and 8.56 ± 9.17 mm2 for non-BLF IOLs (P = .028), with the mean annual MA area increase of 0.78 ± 0.84 mm2 and 1.26 ± 1.32 mm2, respectively (P = .042).

CONCLUSIONS

BLF IOLs did not show added benefit over non-BLF IOLs in terms of MA-free survival but were associated with less progression over time in a cohort of patients with nAMD.

The Effect of Blue-Light Filtering Intraocular Lenses on the Development and Progression of Glaucoma

PRCIS

Among patients who underwent uneventful cataract surgery, an advantage was seen to blue-light filtering (BLF) intraocular lenses (IOLs) in terms of glaucoma-free survival and glaucoma procedure-free survival. Among patients with preexisting glaucoma, no advantage was seen.

PURPOSE

To assess the effect of BLF IOLs on the development and progression of glaucoma after cataract surgery.

PATIENTS AND METHODS

A retrospective cohort study of patients who underwent uneventful cataract surgery between 2007 and 2018 at Kymenlaakso Central Hospital, Finland. Survival analyses for the overall risk of developing glaucoma or undergoing glaucoma procedures were assessed between patients who received a BLF IOL (SN60WF) and a non-BLF IOL (ZA9003 and ZCB00). A separate analysis was performed on patients with preexisting glaucoma.

RESULTS

Included 11,028 eyes of 11,028 patients with a mean age of 75 ± 9 years (62% females). The BLF IOL was used in 5188 eyes (47%) and the non-BLF IOL in 5840 eyes (53%). During the follow-up (mean: 55 ± 34 mo), 316 cases of glaucoma were diagnosed. Glaucoma-free survival rates showed an advantage to the BLF IOL ( P = 0.036). In a Cox regression analysis controlling for age and sex the use of a BLF IOL was again associated with a lower ratio of glaucoma development (hazard ratio:0.778; 95% CI: 0.621-0.975). Furthermore, glaucoma procedure-free survival analysis revealed an advantage to the BLF IOL (hazard ratio:0.616; 95% CI: 0.406-0.935). Among 662 cases, which already had glaucoma at the time of surgery, no significant differences were seen in any outcome.

CONCLUSIONS

Among a large cohort of patients who underwent cataract surgery, the use of BLF IOLs was associated with favorable glaucoma outcomes compared with the use of non-BLF IOLs. Among patients with preexisting glaucoma, no significant advantage was seen.

Blue Light Exposure: Ocular Hazards and Prevention-A Narrative Review

INTRODUCTION

Exposure to blue light has seriously increased in our environment since the arrival of light emitting diodes (LEDs) and, in recent years, the proliferation of digital devices rich in blue light. This raises some questions about its potential deleterious effects on eye health. The aim of this narrative review is to provide an update on the ocular effects of blue light and to discuss the efficiency of methods of protection and prevention against potential blue light-induced ocular injury.

METHODS

The search of relevant English articles was conducted in PubMed, Medline, and Google Scholar databases until December 2022.

RESULTS

Blue light exposure provokes photochemical reactions in most eye tissues, in particular the cornea, the lens, and the retina. In vitro and in vivo studies have shown that certain exposures to blue light (depending on the wavelength or intensity) can cause temporary or permanent damage to some structures of the eye, especially the retina. However, currently, there is no evidence that screen use and LEDs in normal use are deleterious to the human retina. Regarding protection, there is currently no evidence of a beneficial effect of blue blocking lenses for the prevention of eye diseases, in particular age-related macular degeneration (AMD). In humans, macular pigments (composed of lutein and zeaxanthin) represent a natural protection by filtering blue light, and can be increased through increased intake from foods or food supplements. These nutrients are associated with lower risk for AMD and cataract. Antioxidants such as vitamins C, E, or zinc might also contribute to the prevention of photochemical ocular damage by preventing oxidative stress.

CONCLUSION

Currently, there is no evidence that LEDs in normal use at domestic intensity levels or in screen devices are retinotoxic to the human eye. However, the potential toxicity of long-term cumulative exposure and the dose-response effect are currently unknown.

Association of Blue Light-Filtering Intraocular Lenses With All-Cause and Traffic Accident-Related Injuries Among Patients Undergoing Bilateral Cataract Surgery in Finland

IMPORTANCE

Blue light-filtering (BLF) intraocular lenses (IOLs) have been widely used in clinical practice for more than 20 years and have been implanted in millions of patients with cataracts worldwide. However, little evidence on the association of BLF IOLs with injuries is available.

OBJECTIVE

To assess the association of BLF IOLs with all-cause and traffic accident-related injuries and quality of vision while driving after bilateral cataract surgery.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective registry-based cohort study included patients who underwent bilateral cataract surgery between September 3, 2007, and December 14, 2018, and were followed until December 14, 2021. Surgery was performed at the Department of Ophthalmology, Kymenlaakso Central Hospital, Kotka, Finland. The 4986 participants received non-BLF IOLs (n = 2609) or BLF IOLs (n = 2377) in both eyes. Patients undergoing bilateral surgery between 2015 to 2016 with non-BLF IOLs (n = 102) or BLF IOLs (n = 91) and currently driving a car were interviewed using a structured questionnaire for visual performance while driving.

EXPOSURES

Follow-up for a mean (SD) of 2166 (1110) days after second eye surgery.

MAIN OUTCOMES AND MEASURES

Kaplan-Meier and multivariable Cox proportional hazards regression analyses for the risk of all-cause and traffic accident-related injuries after surgery in the second eye obtained from the patient medical records were assessed. To improve follow-up precision, both death and the end of the follow-up were used as censoring events.

RESULTS

A total of 4986 patients were included in the analysis (1707 [34.2%] men and 3279 [65.8%] women; mean [SD] age, 73.2 [8.6] years at the first surgery and 74.3 [8.8] years at the second). Injury-free survival rates preceding the first eye surgery were comparable between the non-BLF and BLF IOL groups (hazard ratio adjusted for age and sex, 0.95 [95% CI, 0.81-1.13; P = .57]). In multivariable Cox proportional hazards regression analysis controlling for age and sex, the use of BLF IOLs showed no advantage in overall injuries compared with the use of non-BLF IOLs (hazard ratio, 0.99 [95% CI, 0.88-1.11]; P = .85) or in any injury subtype. Subjective visual performance parameters for driving were all comparable between the non-BLF and BLF IOL groups except for glare when driving in the dark (evening or night), which occurred among 9 of 80 patients with BLF IOLs compared with 0 of 83 non-BLF IOLs (P < .001).

CONCLUSIONS AND RELEVANCE

The findings of this cohort study suggest that use of BLF IOLs was not associated with reduced risk of injuries, whereas glare during nighttime driving was significantly worse in the BLF IOL group with pseudophakia.

The Blue Light Hazard Versus Blue Light Hype

PURPOSE

The blue light hazard is the experimental finding that blue light is highly toxic to the retina (photic retinopathy), in brief abnormally intense exposures, including sungazing or vitreoretinal endoillumination. This term has been misused commercially to suggest, falsely, that ambient environmental light exposure causes phototoxicity to the retina, leading to age-related macular degeneration (AMD). We analyze clinical, epidemiologic, and biophysical data regarding blue-filtering optical chromophores.

DESIGN

Perspective.

METHODS

Analysis and integration of data regarding the blue light hazard and blue-blocking filters in ophthalmology and related disciplines.

RESULTS

Large epidemiologic studies show that blue-blocking intraocular lenses (IOLs) do not decrease AMD risk or progression. Blue-filtering lenses cannot reduce disability glare because image and glare illumination are decreased in the same proportion. Blue light essential for optimal rod and retinal ganglion photoreception is decreased by progressive age-related crystalline lens yellowing, pupillary miosis, and rod and retinal ganglion photoreceptor degeneration. Healthful daily environmental blue light exposure decreases in older adults, especially women. Blue light is important in dim environments where inadequate illumination increases risk of falls and associated morbidities.

CONCLUSIONS

The blue light hazard is misused as a marketing stratagem to alarm people into using spectacles and IOLs that restrict blue light. Blue light loss is permanent for pseudophakes with blue-blocking IOLs. Blue light hazard misrepresentation flourishes despite absence of proof that environmental light exposure or cataract surgery causes AMD or that IOL chromophores provide clinical protection. Blue-filtering chromophores suppress blue light critical for good mental and physical health and for optimal scotopic and mesopic vision.

Effect of Blue Light-Filtering Intraocular Lenses on Insomnia After Cataract Surgery: A Nationwide Cohort Study With 10-Year Follow-up

PURPOSE

To compare the incidence of clinically diagnosed insomnia after cataract surgery in pseudophakic eyes with blue light-filtering intraocular lenses (BF-IOLs) and non-BF-IOLs.

DESIGN

Nationwide cohort study using the Taiwan National Health Insurance Research Database.

METHODS

We enrolled 171,415 patients who underwent cataract surgery in both eyes between 2008 and 2013 and followed them till 2018. Propensity score matching (PSM) was used to balance the baseline characteristics between the 2 IOL groups. The Cox model and cause-specific hazard model were used to estimate the hazard ratios (HRs) and subdistribution hazard ratio (SHR).

RESULTS

Overall, 19,604 (11.4%) and 151,811 (88.6%) patients had BF-IOL and non-BF-IOL implants, respectively. The BF-IOL group tended to be younger and had fewer chronic diseases. Within a mean follow-up period of 6.2 years, the incidence rates of insomnia (per 100 person-years) in the BF-IOL and non-BF-IOL groups were 2.97 and 3.21, respectively. There was no significant difference in the incidence rate of insomnia between the 2 IOL groups after treating all-cause mortality as a competing risk (SHR 0.98, 95% CI 0.95-1.01) and after PSM (HR 0.97, 95% CI 0.92-1.01), respectively. Subgroup analysis revealed no significant difference in the insomnia rate between the 2 IOL groups for various age groups, 2 sex groups, and men with and without benign prostatic hyperplasia.

CONCLUSION

In Taiwan, the use of a BF-IOL for up to 10 years had no apparent disadvantage over non-BF-IOLs with respect to insomnia.

Effect of Blue Light-Filtering Intraocular Lenses on Age-Related Macular Degeneration: A Nationwide Cohort Study With 10-Year Follow-up

PURPOSE

To determine the incidence rate of age-related macular degeneration (AMD) after cataract surgery and compare the relative incidence of AMD in pseudophakes with blue light-filtering intraocular lenses (BF-IOLs) and non-BF-IOLs.

DESIGN

A nationwide cohort study conducted using the Taiwan National Health Insurance Research Database.

METHODS

We enrolled 186,591 patients who underwent cataract surgery in both eyes between 2008 and 2013 and monitored them from the index date (the date of first cataract surgery) until AMD, death, loss to follow-up, or December 31, 2017, whichever occurred first. Propensity score matching (PSM) was used to balance the baseline characteristics between the BF-IOL and non-BF-IOL groups.

RESULTS

BF-IOLs were implanted in 21,126 patients (11.3%) and non-BF-IOLs were implanted in 165,465 patients (88.7%). Patients in the BF-IOL group tended to be younger, with fewer men, different cataract surgery years, higher income, more nonmanual workers, more patients from urban and suburban areas, and fewer chronic diseases compared with the non-BF-IOL group. With a mean follow-up period of 6.1 years (range, 1-10 years) after cataract surgery, 12,533 and 1655 patients developed non-exudative AMD and exudative AMD, respectively. The incidence rate of non-exudative AMD and exudative AMD (per 1000 person-years) was 9.95 and 1.22 for the BF-IOL group and 11.13 and 1.44 for the non-BF-IOL group, respectively. After PSM, no statistical difference in the incidence rate of nonexudative AMD (hazards ratio, 0.95; 95% CI, 0.88-1.03) and exudative AMD (hazard ratio, 0.96; 95% CI, 0.77-1.18) was observed between the BF-IOL and non-BF-IOL groups.

CONCLUSIONS

In Taiwan, the incidence rate of AMD after cataract surgery was 11.59 per 1000 person-years. The use of a BF-IOL for up to 10 years had no apparent advantage over a non-BF-IOL in the incidence of AMD.

Protector role of intraocular lenses under artificial light conditions

INTRODUCTION

The aim of this work is to analyse, in an in vitro model, the possible protective effects of ultraviolet- (UV-) or UV/ blue-filtering intraocular lens (IOLs) under LED lighting conditions.

METHODS

10 models of IOLs were evaluated. Light transmission spectrum was recorded from 300 to 800 nm, in steps of 1 nm. Photodamage in vitro model was induced in ARPE-19 cells by blue LED light (465-475 nm). Changes in cell viability and oxidative stress variables were studied to assess the protective effect of IOLs.

RESULTS

UV/blue-filtering IOLs models block blue light spectrum in different proportion and UV-filtering IOLs blocking wavelength below 400 nm. However, in vitro study under blue LED light exposure does not show protective effects related with mitochondrial dysfunction and oxidative stress of UV/blue-filtering IOLs.

CONCLUSIONS

The current in vitro study suggest that UV/blue filtering IOLs are not useful in terms of photoprotection in artificial light conditions. The results obtained indicate that it is needed to give attention to other IOLs parameters besides the type of filter, as it seems they could have influence also protective role.

Glare and Mobility Performance in Glaucoma: A Pilot Study

PRCIS

Glare disability affects patients with moderate and severe glaucoma. Under glare conditions, mobility performances of glaucoma patients are reduced.

PURPOSE

The aim of this study was to evaluate glare disability and its impact on mobility and orientation in glaucoma patients.

METHODS

Twenty-two glaucoma patients and 12 age-matched control subjects were included. All patients underwent a clinical evaluation of visual function and halo size measurements to determine glare disability with a glare score (GS) of the best eye and worse eye. Mobility was evaluated by 4 mobility courses on an artificial street (StreetLab) under photopic conditions (P) and mesopic conditions with an additional light source in front of the patient to mimic dazzling conditions (M+G). Mobility time, mobility incidents, trajectory segmentation, distance traveled, preferred walking speed on trial (WS) and percentage of preferred walking speed (PPWS) were recorded, and the Nasa task load index (Nasa-TLX) was evaluated.

RESULTS

GS of the worse eye and GS of the best eye were significantly higher in glaucoma patients than in the control group (P=0.001 and 0.003). It was significantly different between moderate glaucoma patients and controls (P=0.001 and 0.010, respectively) and between severe glaucoma patients and controls (P=0.049 and 0.016). In locomotion tasks, comparing performance under M+G and P conditions, mobility performance was significantly different concerning mobility time (P=0.010), distance traveled (P=0.008), WS (P=0.007), PPWS (P=0.006), and Nasa-TLX (P=0.017) in the glaucoma group. Under M+G lighting conditions, mobility performance for glaucoma patients was significantly worse than controls with regard to WS (P=0.038), PPWS (P=0.0498), mobility time (P=0.046), and Nasa-TLX (P=0.006).

CONCLUSION

Glare disability was observed in patients with moderate and severe glaucoma and had an impact on their mobility performance.

The Influence of Blue-Filtering Intraocular Lenses Implant on Exudative Age-Related Macular Degeneration: A Case-Control Study

Purpose

To determine whether the use of a blue light-filtering intraocular lens (IOL) prevents the onset of wet age-related macular degeneration (AMD). More precisely, we examined the proportion of blue light-filtering IOL in a wet AMD patients’ sample and compared it with a general North American pseudophakic population sample.

Design

Retrospective case–control study.

Methods

Case patients were diagnosed and treated for wet AMD and had prior IOL implantation at least 3 years before the diagnosis of wet AMD. Control patients were randomly selected among patients who had cataract surgery at our institution. They were exempt of AMD and paired for the year of surgery, sex and age at cataract surgery. A total of 196 patients were included in each study group.

Results

Among patients with wet AMD, 62.8% had a blue light-filtering IOL compared with 63.3% among control patients (p = 0.92). Mean time between implantation and injection of anti-VEGF in AMD patients was 6.62 years (95% confidence interval (CI): 6.04–7.19) in non-blue light-filtering IOL group and 5.76 years (95% CI: 5.41–6.11) in blue light-filtering IOL group (p = 0.0120).

Conclusion

No correlations could be established between the presence of a blue light filter in the IOL and the occurrence of wet AMD. AMD patients without blue light-filtering IOL were injected significantly later than patients with an IOL filtering blue light, which contradict the potential clinical benefit of the blue light filter.

Comparison of the Ultraviolet Light Filtering across Different Intraocular Lenses

SIGNIFICANCE

We have analyzed the ultraviolet transmittance of some commercial intraocular lenses (IOLs). The results show differences of wavelength cutoff among them.

PURPOSE

The purpose of this study was to measure and compare the ultraviolet light transmittance of different IOLs made out of acrylic hydrophobic, hydrophilic, and hydrophilic with hydrophobic surface materials from different manufacturers.

METHODS

The spectral transmission curves of eight monofocal IOLs with the same dioptric power of +20.0 diopters were measured using a PerkinElmer Lambda 35 ultraviolet/visible spectrometer. Two IOLs of each type were tested three times. The ultraviolet cutoff wavelength at 10% transmission and the mean values were calculated.

RESULTS

All lenses prevented transmission of ultraviolet C (200 to 280 nm) and B radiation (280 to 315 nm). However, not all IOLs provided the same filtering properties in ultraviolet A (315 to 380 nm). Within the ultraviolet A range, the ultraviolet radiation cutoff wavelength of 10% ranges from approximately 360 to 400 nm. HOYA iSert 250 provided a cutoff wavelength of 398.4 nm; AcrySof SA60AT, 396.2 nm; AcrySof SA60WF, 395.7 nm; CT Asphina 404, 378.34 nm; Tecnis ZCB00, 377.70 nm; CT Lucia 607P, 379 nm; C-Flex 570C, 377 nm; and enVista MX60, 360 nm.

CONCLUSIONS

Intraocular lenses of different materials and manufacturers have different ultraviolet transmission characteristics. AcrySof (SA60AT and SA60WF) and HOYA iSert 250 provided the highest ultraviolet radiation transmission; the cutoff wavelength of 10% is close to 400 nm. In contrast, enVista IOL showed the lowest ultraviolet radiation cutoff.

Analysis of a Systematic Review About Blue Light-Filtering Intraocular Lenses for Retinal Protection: Understanding the Limitations of the Evidence

Importance

Cataract surgery, with intraocular lens (IOL) implantation, is the most common ocular surgical procedure worldwide. It has been suggested that IOLs that selectively attenuate short wavelength visible light (blue light-filtering IOLs) may be beneficial for macular health. Whether blue light-filtering IOLs impart retinal photoprotection is of public health relevance, particularly in the context of aging demographics and the increasing global prevalence of age-related macular degeneration. This review analyzes and interprets the key findings, including consideration of the implications for practice and future research, of a 2018 Cochrane systematic review that evaluated the efficacy and safety of blue light-filtering IOLs for providing protection to macular health and function.

Observations

The Cochrane systematic review included 51 randomized controlled trials that were performed in 17 countries. The trials involved adults undergoing cataract surgery in which a blue light-filtering IOL was compared with an equivalent non-blue light-filtering IOL. Study follow-up periods ranged from 1 month to 5 years. Together, these studies considered clinical outcomes in more than 5000 eyes. There was limited ability to combine data across trials (to draw overall conclusions) because of the use of different measurement techniques for outcomes, incomplete reporting of data, and/or varied follow-up periods. We identified substantial shortcomings in the internal validity of many of the included studies, particularly regarding trial design, conduct, and reporting. We propose several avenues for improving the rigor of potential future research in the field, including developing a core set of outcome measures, the inclusion of sample size calculations, the masking of trial participants and outcome assessors, and prospective clinical trial registration.

Conclusions and Relevance

Using blue light-filtering IOLs to impart benefits to the macula is currently not supported by the best available clinical research evidence, and it is important that clinicians are mindful of this evidence limitation when adopting these devices in clinical practice.

Blue-light filtering intraocular lenses (IOLs) for protecting macular health

BACKGROUND

An intraocular lens (IOL) is a synthetic lens that is surgically implanted within the eye following removal of the crystalline lens, during cataract surgery. While all modern IOLs attenuate the transmission of ultra-violet (UV) light, some IOLs, called blue-blocking or blue-light filtering IOLs, also reduce short-wavelength visible light transmission. The rationale for blue-light filtering IOLs derives primarily from cell culture and animal studies, which suggest that short-wavelength visible light can induce retinal photoxicity. Blue-light filtering IOLs have been suggested to impart retinal protection and potentially prevent the development and progression of age-related macular degeneration (AMD). We sought to investigate the evidence relating to these suggested benefits of blue-light filtering IOLs, and to consider any potential adverse effects.

OBJECTIVES

To assess the effects of blue-light filtering IOLs compared with non-blue-light filtering IOLs, with respect to providing protection to macular health and function.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 9); Ovid MEDLINE; Ovid Embase; LILACS; the ISRCTN registry; ClinicalTrials.gov and the ICTRP. The date of the search was 25 October 2017.

SELECTION CRITERIA

We included randomised controlled trials (RCTs), involving adult participants undergoing cataract extraction, where a blue-light filtering IOL was compared with an equivalent non-blue-light filtering IOL.

DATA COLLECTION AND ANALYSIS

The prespecified primary outcome was the change in distance best-corrected visual acuity (BCVA), as a continuous outcome, between baseline and 12 months of follow-up. Prespecified secondary outcomes included postoperative contrast sensitivity, colour discrimination, macular pigment optical density (MPOD), proportion of eyes with a pathological finding at the macula (including, but not limited to the development or progression of AMD, or both), daytime alertness, reaction time and patient satisfaction. We evaluated findings related to ocular and systemic adverse effects.Two review authors independently screened abstracts and full-text articles, extracted data from eligible RCTs and judged the risk of bias using the Cochrane tool. We reached a consensus on any disagreements by discussion. Where appropriate, we pooled data relating to outcomes and used random-effects or fixed-effect models for the meta-analyses. We summarised the overall certainty of the evidence using GRADE.

MAIN RESULTS

We included 51 RCTs from 17 different countries, although most studies either did not report relevant outcomes, or provided data in a format that could not be extracted. Together, the included studies considered the outcomes of IOL implantation in over 5000 eyes. The number of participants ranged from 13 to 300, and the follow-up period ranged from one month to five years. Only two of the studies had a trial registry record and no studies referred to a published protocol. We did not judge any of the studies to have a low risk of bias in all seven domains. We judged approximately two-thirds of the studies to have a high risk of bias in domains relating to 'blinding of participants and personnel' (performance bias) and 'blinding of outcome assessment' (detection bias).We found with moderate certainty, that distance BCVA with a blue-light filtering IOL, at six to 18 months postoperatively, and measured in logMAR, was not clearly different to distance BCVA with a non-blue-light filtering IOL (mean difference (MD) -0.01 logMAR, 95% confidence interval (CI) -0.03 to 0.02, P = 0.48; 2 studies, 131 eyes).There was very low-certainty evidence relating to any potential inter-intervention difference for the proportion of eyes that developed late-stage AMD at three years of follow-up, or any stage of AMD at one year of follow-up, as data derived from one trial and two trials respectively, and there were no events in either IOL intervention group, for either outcome. There was very low-certainty evidence for the outcome for the proportion of participants who lost 15 or more letters of distance BCVA at six months of follow-up; two trials that considered a total of 63 eyes reported no events, in either IOL intervention group.There were no relevant, combinable data available for outcomes relating to the effect on contrast sensitivity at six months, the proportion of eyes with a measurable loss of colour discrimination from baseline at six months, or the proportion of participants with adverse events with a probable causal link with the study interventions after six months.We were unable to draw reliable conclusions on the relative equivalence or superiority of blue-light filtering IOLs versus non-blue-light filtering IOLs in relation to longer-term effects on macular health. We were also not able to determine with any certainty whether blue-light filtering IOLs have any significant effects on MPOD, contrast sensitivity, colour discrimination, daytime alertness, reaction time or patient satisfaction, relative to non-blue-light filtering IOLs.

AUTHORS' CONCLUSIONS

This systematic review shows with moderate certainty that there is no clinically meaningful difference in short-term BCVA with the two types of IOLs. Further, based upon available data, these findings suggest that there is no clinically meaningful difference in short-term contrast sensitivity with the two interventions, although there was a low level of certainty for this outcome due to a small number of included studies and their inherent risk of bias. Based upon current, best-available research evidence, it is unclear whether blue-light filtering IOLs preserve macular health or alter risks associated with the development and progression of AMD, or both. Further research is required to fully understand the effects of blue-light filtering IOLs for providing protection to macular health and function.

VISUALIZING RETINAL PIGMENT EPITHELIUM PHENOTYPES IN THE TRANSITION TO GEOGRAPHIC ATROPHY IN AGE-RELATED MACULAR DEGENERATION

PURPOSE

To inform the interpretation of clinical optical coherence tomography and fundus autofluorescence imaging in geographic atrophy (GA) of age-related macular degeneration by determining the distribution of retinal pigment epithelium (RPE) phenotypes in the transition from health to atrophy in donor eyes.

METHODS

In RPE-Bruch membrane flat mounts of two GA eyes, the terminations of organized RPE cytoskeleton and autofluorescent material were compared. In high-resolution histological sections of 13 GA eyes, RPE phenotypes were assessed at ±500 and ±100 μm from the descent of the external limiting membrane (ELM) toward Bruch membrane. The ELM descent was defined as curved, reflected, or oblique in shape. Thicknesses of RPE, basal laminar deposit (BLamD), and RPE plus BLamD were measured.

RESULTS

A border of atrophy that can be precisely delimited is the ELM descent, as opposed to the termination of the RPE layer itself, because of dissociated RPE in the atrophic area. Approaching the ELM descent, the percentage of abnormal RPE morphologies increases, the percentage of age-normal cells decreases, overall RPE thickens, and BLamD does not thin. The combination of RPE plus BLamD is 19.7% thicker at -100 μm from the ELM descent than that at -500 μm (23.1 ± 10.7 μm vs. 19.3 ± 8.2 μm; P = 0.05).

CONCLUSION

The distribution of RPE phenotypes at the GA transition supports the idea that these morphologies represent defined stages of a degeneration sequence. The idea that RPE dysmorphia including rounding and stacking helps explain variable autofluorescence patterns in GA is supported. The ELM descent and RPE plus BLamD thickness profile may have utility as spectral domain optical coherence tomography metrics in clinical trials.

Photoprotection and photoreception of intraocular lenses under xenon and white LED illumination

OBJECTIVE

To analyze the photoprotection and phototransmission that various intraocular lenses (IOLs) provide under the illumination of a xenon (Xe) lamp and white LEDs (light emitting diode).

METHODS

The spectral transmission curves of six representative IOLs were measured using a Perkin-Elmer Lambda 35 UV/VIS spectrometer. Various filtering simulations were performed using a Xe lamp and white LEDs. The spectral emissions of these lamps were measured with an ILT-950 spectroradiometer.

RESULTS

The IOLs analyzed primarily show transmission of nearly 100% in the visible spectrum. In the ultraviolet (UV) region, the filters incorporated in the various IOLs did not filter equally, and some of them let an appreciable amount of UV through. The Xe lamp presented a strong emission of ultraviolet A (UVA), and its emission under 300nm was not negligible. The white LED did not present an appreciable emission under 380nm.

CONCLUSIONS

The cut-off wavelength of most filters is between 380 and 400nm (Physiol Hydriol60C(®), IOLTECH E4T(®), Alcon SA60AT(®), Alcon IQ SN60WF(®)), so that their UV protection is very effective. Nonetheless, the IOL OPHTEC Oculaid(®) contains a filter that, when a Xe lamp is used, lets through up to 20% for 350nm and up to 15% for 300nm, which at this point is ultraviolet B (UVB). The OPHTEC(®) Artisan IOL has a transmission peak below 300nm, which must be taken into account under Xe illumination. White LEDs do not emit energy below 380nm, so no special protection is required in the UV region.

Light damage to the retina: an historical approach

A brief review of retinal light damage is presented. Thermal damage requires a local rise in temperature of at least 10 °C, causing an instant denaturation of proteins. The primary absorber is melanin. Photochemical damage occurs at body temperature and involves cellular damage by reactive forms of oxygen. The photosensitizers are photoproducts of the visual pigments. First indications that non-thermal damage might exist, in particular in the case of eclipse blindness, was presented by Vos in 1962. Attribution thereof to photochemical action was presented in 1966 by Noell et al who also measured the first action spectrum, in rat. It turned out to be identical to the absorption spectrum of rhodopsin. However, in 1976 and 1982 Ham et al found a quite different spectrum in monkeys, peaking at short wavelengths. The latter spectrum, but not the former, was confirmed since in numerous publications with animal models including rat. In ophthalmological practice a 'sunburn' was at first the only complaint caused by light damage. To avoid this, patients with dilated pupils should always be advised to wear sunglasses. Since the invention of the laser accidents have been reported, the most recent development is youth playfully pointing a strong laser pen in their eyes with marked consequences. The operation microscope and endoilluminators should always be used as brief as possible to avoid photochemical damage. Arguments for implant lenses that block not only the UV but also part of the visible spectrum seem too weak to justify extra costs.

Attenuating Photostress and Glare Disability in Pseudophakic Patients through the Addition of a Short-Wave Absorbing Filter

To evaluate the effects of filtering short wavelength light on visual performance under intense light conditions among pseudophakic patients previously implanted with a clear intraocular lens (IOL). This was a patient-masked, randomized crossover study conducted at 6 clinical sites in the United States between September 2013 and January 2014. One hundred fifty-four bilaterally pseudophakic patients were recruited. Photostress recovery time and glare disability thresholds were measured with clip-on blue-light-filtering and placebo (clear; no blue-light filtration) glasses worn over patients' habitual correction. Photostress recovery time was quantified as the time necessary to regain sight of a grating target after intense light exposure. Glare disability threshold was assessed as the intensity of a white-light annulus necessary to obscure a central target. The order of filter used and test eye were randomized across patients. Photostress recovery time and glare disability thresholds were significantly improved (both P < 0.0001) when patients used blue-light-filtering glasses compared with clear, nonfiltering glasses. Compared with a nonfiltering placebo, adding a clip-on blue-absorbing filter to the glasses of pseudophakic patients implanted with clear IOLs significantly increased their ability to cope with glare and to recover normal viewing after an intensive photostress. This result implies that IOL designs with blue-light-filtering characteristics may be beneficial under intense light conditions.

Photo-damage, photo-protection and age-related macular degeneration

The course of Age-related Macular Degeneration (AMD) is described as the effect of light (400–580 nm) on various molecular targets in photoreceptors and the retinal pigment epithelium (RPE). Photo-damage is followed by inflammation, increasing oxidative stress and, probably, unveiling new photosensitive molecules.

Oxidative photodegradation of ocular tissues: beneficial effects of filtering and exogenous antioxidants

The fact that light is necessary for life is generally accepted as an axiom. The extent to which light interacts and influences human biology, however, is often not fully appreciated. Exposure to sunlight, for instance, can both promote and degrade human health. There is now general scientific consensus that, although the eye evolved to respond to light, it is also damaged by excessive exposure. Light-mediated ocular damage is involved in the pathophysiology of many common forms of blindness. The type of ocular tissue damage induced by light exposure depends on the extent of exposure and wavelength. The tissues of the lens, cornea, and retina contain specific chemical moieties that have been proven to exhibit light-mediated oxidative degradation. Proteins and lipids present in the cornea, lens, and retina, meet all of the physical requirements known to initiate the process of oxidative photodegradation upon exposure to solar radiation. As such, different mechanisms have evolved in the lens, cornea, and retina to ameliorate such light-mediated oxidative damage. It appears, however, that such mechanisms are ill-matched to handle modern conditions: namely, poor diet and longer life-spans (and the degenerative diseases that accompany them). Hence, steps must be taken to protect the eye from the damaging effects of light. Preventative measures include minimizing actinic light exposure, providing exogenous filtering (e.g., through the use of protective lenses), and enhancing antioxidant defenses (e.g., through increased dietary intake of antioxidants). These strategies may yield long-term benefits in terms of reducing oxidative photodegradation of the ocular tissues.

Quantitative autofluorescence and cell density maps of the human retinal pigment epithelium

PURPOSE

Lipofuscin (LF) accumulation within RPE cells is considered pathogenic in AMD. To test whether LF contributes to RPE cell loss in aging and to provide a cellular basis for fundus autofluorescence (AF) we created maps of human RPE cell number and histologic AF.

METHODS

Retinal pigment epithelium-Bruch's membrane flat mounts were prepared from 20 donor eyes (10 ≤ 51 and 10 > 80 years; postmortem: ≤4.2 hours; no retinal pathologies), preserving foveal position. Phalloidin-binding RPE cytoskeleton and LF-AF (488-nm excitation) were imaged at up to 90 predefined positions. Maps were assembled from 83,330 cells in 1470 locations. From Voronoi regions representing each cell, the number of neighbors, cell area, and total AF intensity normalized to an AF standard was determined.

RESULTS

Highly variable between individuals, RPE-AF increases significantly with age. A perifoveal ring of high AF mirrors rod photoreceptor topography and fundus-AF. Retinal pigment epithelium cell density peaks at the fovea, independent of age, yet no net RPE cell loss is detectable. The RPE monolayer undergoes considerable lifelong re-modeling. The relationship of cell size and AF, a surrogate for LF concentration, is orderly and linear in both groups. Autofluorescence topography differs distinctly from the topography of age-related rod loss.

CONCLUSIONS

Digital maps of quantitative AF, cell density, and packing geometry provide metrics for cellular-resolution clinical imaging and model systems. The uncoupling of RPE LF content, cell number, and photoreceptor topography in aging challenges LF's role in AMD.

Effect of the Blue Filter Intraocular Lens on the Progression of Geographic Atrophy

Purpose

To clinically evaluate the effect of blue light–filtering intraocular lenses (IOLs) on disease progression in patients with geographic atrophy (GA).

Methods

Clinical data from 66 eyes of 40 patients were investigated, 27 with a blue filter and 39 with a non–blue filter IOL. Spectral-domain optical coherence tomography technology and the advanced retinal pigment epithelium analysis software tool were used to measure lesion size and monitor its progression over 1 year.

Results

The mean and median baseline area of GA for the total sample was 5.55 ± 4.72 mm2 and 4.40 mm2, respectively. There was a statistically significant difference of the mean (p = 0.0002) and median (p<0.0001) GA progression in 1 year between the blue filter and non–blue filter IOL group (0.72 ± 0.39 SD mm2 mean and 0.70 mm2 median compared to 1.48 ± 0.88 SD mm2 and 1.30 mm2, respectively).

Conclusions

The clinical data strongly support a photoprotective role of blue light–filtering IOLs on the progression of the atrophic form of dry age-related macular degeneration after cataract surgery.

Clinical properties of a novel, glistening-free, single-piece, hydrophobic acrylic IOL

A new, single-piece, hydrophobic acrylic lens – the first constructed with a lens optic and haptics comprised of a hydroxyethyl methacrylate-polyethylene glycol phenyl ether acrylate–styrene copolymer, cross-linked with ethylene glycol dimethacrylate, and labeled as “glistening-free” – was recently introduced globally. Glistenings have been a significant source of clinical concern with previous hydrophobic lens designs. This new monofocal lens provides enhanced, clear optics for lens-based surgery. The superior optical clarity of this lens is achieved through the elimination of glistenings, enhanced surface durability, high refractive index, a high Abbe number, and an aspheric design. Additionally, the lens design reduces the risk of developing posterior capsule opacification.

Glare's causes, consequences, and clinical challenges after a century of ophthalmic study

PURPOSE

To provide a multidisciplinary synthesis of scientific information on disability, discomfort, dazzling, and scotomatic (photostress) glare.

DESIGN

Perspective.

METHODS

Analysis and integration of relevant historical and contemporary publications on glare in ophthalmology, illumination engineering, neurology, and other relevant disciplines.

RESULTS

Disability glare is caused by scattered intraocular light (straylight) not useful for vision. Straylight casts a veiling luminance on the retina, reducing image contrast and impairing vision. In common environments, glare and target illumination sources have the same or similar spectra. Colored spectacle or intraocular lens filters reduce both proportionately, so they do not increase retinal image contrast or decrease disability glare. Discomfort glare is caused by situational illumination too intense or variable. Dazzling glare occurs when high illuminances are spread across the retina. Neurophysiological research is clarifying how discomfort and dazzling glare depend on different retinal photoreceptors and nociceptive brain pathways involving the trigeminal ganglion and thalamus. Photostress is caused by excessive local retinal photopigment bleaching uncommon in ordinary situations. Optical glare countermeasures are available for daytime driving but not oncoming automobile headlights at night. Filters that decrease daytime discomfort or dazzling glare also reduce nighttime mesopic and scotopic sensitivity.

CONCLUSIONS

Glare is problematic for patients and clinicians despite a century of scientific research. Advances in understanding glare have been hampered by its complex, multidisciplinary nature and limited interdisciplinary communication. We provide one pathway through the forest of glare nomenclature and mechanisms. Improved diagnostic and therapeutic methodologies await continuing progress in understanding glare.

There is insufficient evidence to recommend lens extraction as a treatment for primary open-angle glaucoma: an evidence-based perspective

Cataract extraction in primary open-angle glaucoma has not been thought to provide a clinically useful or predictable decrease in IOP. This concept has now been challenged, with the opposite belief being promulgated: namely, that lens exchange should be considered as treatment for glaucoma. This revelation could bring a significant change in the glaucoma treatment paradigm. There are no randomised controlled trials to guide the role of lens extraction in primary open-angle glaucoma. The available evidence suggests at most a modest reduction in IOP from cataract extraction - greater in the presence of pseudoexfoliation - which is likely to be of marginal benefit, and only in milder forms of open-angle glaucoma. There is currently no evidence of any quality to suggest that lens extraction routinely represents a clinically useful treatment for primary open-angle glaucoma.

Intraocular and crystalline lens protection from ultraviolet damage

OBJECTIVES

Although the risks of excess solar ultraviolet (UV) exposure of the skin are well recognized, the need for eye protection is frequently overlooked, or when sunglasses are also recommended, specific guidance is wrong or is not explained. Guidance from the World Health Organization at its InterSun webpage advises people to wear "wrap-around" sunglasses under many conditions. The objective of this study was to examine the need for UV filtration in prescription lenses, contact lenses, and sunglasses.

METHODS

The geometry of UV exposure of both eyes, solar position, ground reflection, pupil size, and lid opening were studied. Because an accurate determination of cumulative ocular exposure is difficult, the cornea itself can serve as a biologic dosimeter, because photokeratitis is not experienced on a daily basis but does under certain ground-surface and sunlight conditions. From a knowledge of the UV-threshold dose required to produce photokeratitis, we have an upper level of routine ocular exposure to ambient UV.

RESULTS

From ambient UV measurements and observed photokeratitis, the upper limits of UV exposure of the crystalline lens or an intraocular lens implant are estimated. The risk of excess UV exposure of the germinative cells of the lens is greatest from the side. Sunglasses can actually increase UV exposure of the germinative region of the crystalline lens and the corneal limbus by disabling the eyes' natural protective mechanisms of lid closure and pupil constriction! The level of UV-A risk is difficult to define.

CONCLUSIONS

Proper UV-absorbing contact lenses offer the best mode for filtering needless exposure of UV radiation of the lens and limbus.

Measurements of transmission spectrums and estimation of retinal blue-light irradiance values of currently available clear and yellow-tinted intraocular lenses

PURPOSE

To compare the spectral transmission characteristics of currently available, foldable, clear and yellow-tinted intraocular lenses (IOLs), and evaluate the protective effects they provide against retinal damage by sunlight.

METHODS

We measured the spectral transmittance in the wavelength range of 300-800 nm using a spectrophotometer for 63 IOLs including three clear IOLs (N4-18B, Nidek; X-60, Santen; KS-3Ai, Staar Japan) and four yellow-tinted IOLs (N4-18YG, Nidek; NX-60, Santen; KS-AiN, Staar Japan; NM-1, Hoya) with three different lens powers. The blue-light irradiance (BLI) values through the IOLs were calculated as the retinal hazard index for sungazing. The data from three clear IOLs (SA60AT, Alcon Japan; VA-60BBR, Hoya; AU6K, Kowa) and three yellow-tinted IOLs (SN60AT, Alcon Japan; YA-60BBR, Hoya; AU6N, Kowa) reported previously were also discussed.

RESULTS

Except for the X-60, the clear IOLs completely absorbed ultraviolet (UV) light and nearly completely transmitted visible light at wavelengths longer than 440 nm. Yellow-tinted IOLs absorbed more in the blue-light range (400-500 nm) than clear IOLs. All IOLs had lower BLI values than aphakic eyes, and all yellow-tinted IOLs had lower BLI values than phakic eyes. The BLI values of the NX-60, KS-AiN, NM-1, SN60AT and YA-60BBR IOLs decreased with the increase in lens power.

CONCLUSIONS

Compared to aphakic eyes, currently available UV-blocking clear and yellow-tinted IOLs reduce the BLI values by 43-82%. However, the data presented in this study are not directly applicable to humans implanted with IOLs or for the use of IOLs in a clinical situation, since in those cases the balance between photoprotection and photoreception must be taken into account.