Sunlight and ultraviolet radiation—pertinent retinal implications and current management

Protein expression of nucleolar protein 12 in the retina and its implication in protection of retina from UV irradiation damage

Nucleolar protein 12 (NOL12), one of the nucleolar proteins which are primarily expressed in the nucleolus and play key roles in RNA metabolism, cell proliferation, cell cycle, and cell survival, is widely expressed in various species and multiple organs. Although it has been reported that the mRNA of Drosophila NOL12 homolog viriato is expressed in the eyes of Drosophila, the protein expression of NOL12 in mammalian eyes remains to be elucidated. In this study, we showed through immunohistochemistry that NOL12 was present in the rat retina, with predominant distribution in the cytoplasm of the retinal neuronal cells. In the human retinoblastoma cell line WERI-Rb1, we found that altering NOL12 expression led to a change in WERI-Rb1 cell viability. Knocking down NOL12 expression decreased cell viability. In contrast, overexpressing NOL12 increased cell viability. Furthermore, increasing NOL12 expression inhibited ultraviolet (UV)-induced apoptosis. These findings demonstrated that NOL12 may play an important protective role in retinal cells. In the WERI-Rb1 cells exposed to UV irradiation, we detected that NOL12 was degraded, but this degradation could be attenuated by a pan-Caspase inhibitor. Notably, the inhibitory effect of NOL12 against UV-induced apoptosis could be restrained by increasing the expression of ATR serine/threonine kinase (ATR), a kinase that, when activated by severe DNA damage, can result in apoptosis. We also found that upregulating NOL12 inhibited the activation of ATR caused by UV irradiation. Additionally, inhibiting ATR activity reduced apoptosis resulting from both silencing NOL12 expression and UV exposure. Thus, NOL12 may protect against UV irradiation-induced retinal damage by inhibiting ATR activity.

A wireless battery-free eye modulation patch for high myopia therapy

The proper axial length of the eye is crucial for achieving emmetropia. In this study, we present a wireless battery-free eye modulation patch designed to correct high myopia and prevent relapse. The patch consists of piezoelectric transducers, an electrochemical micro-actuator, a drug microneedle array, μ-LEDs, a flexible circuit, and biocompatible encapsulation. The system can be wirelessly powered and controlled using external ultrasound. The electrochemical micro-actuator plays a key role in precisely shortening the axial length by driving the posterior sclera inward. This ensures accurate scene imaging on the retina for myopia eye. The drug microneedle array delivers riboflavin to the posterior sclera, and μ-LEDs' blue light induces collagen cross-linking, reinforcing sclera strength. In vivo experiments demonstrate that the patch successfully reduces the rabbit eye's axial length by ~1217 μm and increases sclera strength by 387%. The system operates effectively within the body without the need for batteries. Here, we show that the patch offers a promising avenue for clinically treating high myopia.

[Exogenously induced retinopathies]

Exogenously induced retinopathies can be caused by consumation of stimulating substances, systemic or ocular medications, vaccinations, light or irradiation. Some of the effects are transient, whereas other effects induce irreversible toxic reactions. Retinal damage may develop either acutely with obvious relation to the damaging cause, but often may take a long duration of repeated use of a substance or medication. External stimulants (e.g. nicotine, alcohol, poppers, methanol) are the most frequent cause of exogenously induced retinal damage. Side effects from systemic drugs (e.g. hydroxychloroquine, ethambutol, MEK-, ERK-, FLT3-, checkpoint inhibitors, didanosin, pentosanpolysulfat sodium) or intravitreally applied drugs (e.g. antibiotics, VEGF-inhibitors) are less frequent. Ocular side effects associated with vaccinations are rare. Ambient light sources induce no damaging effects on the retina. Incorrect use of technical or medical light sources (e.g. laser pointers) without adherence to safety recommendations or unshielded observation of the sun might induce permanent retinal damage. Local or external irradiation might induce retinal vascular damage resulting in radiation retinopathy.

Exogen bedingte Retinopathien

Exogen bedingte Retinopathien werden am häufigsten durch externe Stimulanzien, seltener durch unerwünschte Arzneimittelwirkungen systemisch oder intravitreal eingesetzter Medikamente und noch seltener durch Impfungen oder die Einwirkung von Lichtstrahlung verursacht. Die Kenntnis exogener Ursachen und ihre mögliche Symptomatik ist zur Prophylaxe oder zur Früherkennung schädigender Wirkungen und zur adäquaten Beratung der Patienten wichtig.

[Impact of ultraviolet radiation on the retina]

Light has a crucial role in the visual process. For nonvisible radiation in the short-wave spectrum, there are natural mechanisms that protect the human retina from damaging ultraviolet (UV) radiation. Here, the dose (= energy) makes the poison. Damage caused by UV light mainly affects the outer retina, particularly the photoreceptors and the retinal pigment epithelium. While retinal damage due to increased UV radiation exposure can potentially still occur up to the age of 20, in adulthood, exposure of the retina to UV radiation can no longer be assumed, due to decreasing transmission properties of the natural lens. The natural lens, modern intraocular lenses, and wearing of sunglasses with appropriate filter function, particularly in childhood and adolescence, provide a relevant reduction in UV radiation exposure of the retina.

Solar Retinopathy Presenting with Outer Retinal Defects Among Habitants of High Altitude

Solar radiation causes acute foveal injury resulting in outer retinal defects. Symptoms often follow an event of unprotected gazing at a solar eclipse or directly viewing the sun. We encountered a series of cases during winter among habitants of high altitudes who complained of visual field scotomas. All of them had a typical history of prolonged sunbathing but denied gazing at the sun directly. Optical coherence tomography showed outer retinal defects involving the ellipsoid zone characteristic of solar retinopathy in all patients. In this case series, we would like to emphasize the role of geographical factors in the causation of solar retinopathy.

[Change of transcription level of photoreceptor-specific CRX gene in the peripheral blood of the participants of an arctic world oceanic international flight]

The CRX gene encoding the cone-rod homeobox protein is a specific photoreceptor transcription factor crucial for retinal function. Persons temporarily residing in the Arctic zone during the polar summer may suffer from disturbances associated with extremely high ambient illumination. These environmental changes are mediated by retinal photoreceptors; therefore, it is important to study the expression of retinal genes in order to assess individual capacities of sensory adaptation to polar day conditions.

PURPOSE

To reveal the dynamics of CRX expression level in humans after a prolonged temporary exposure to polar day conditions.

MATERIAL AND METHODS

The study included 6 pilots (males from 39 to 69 y.o.) who participated in the Arctic World Oceanic International Flight Sever Vash (West to East, from 62°N 74°E to 72°N 114°E). Samples of peripheral blood for RNA isolation were collected at the start and at the end of the flight. The level of mRNA in the samples was evaluated based on the data of quantitative real-time PCR of the CRX gene, as well as the b2M and TBP housekeeping genes (reference).

RESULTS

Expression of the CRX gene in the studied group (p<0.01) was revealed; the total average level of mRNA was about 3 times higher prior to, and approximately 7 times higher after normalization to the b2M gene. Five pilots had increased expression of the CRX gene within the range of -1.53 to -3.07 (Z-score of <0 before the flight and >0 after the flight). In one pilot, the level of CRX expression was higher at the start, but it reduced by the end of the circumnavigation flight.

CONCLUSIONS

The results confirm the hypothesis that the CRX gene is expressed after a prolonged temporary exposure to polar day conditions. It was also revealed that during rapid adaptation, equal changes in the illumination of retinal photoreceptors lead to different individual dynamics of CRX expression.

Safety profiles of terahertz scanning in ophthalmology

Terahertz (THz) technology has emerged recently as a potential novel imaging modality in biomedical fields, including ophthalmology. However, the ocular biological responses after THz electromagnetic exposure have not been investigated. We conducted a rabbit study to evaluate the safety profiles of THz scanning on eyes, at a tissue, cellular, structural and functional level. Eight animals (16 eyes) were analysed after excessive THz exposure (control, 1 h, 4 h, and 1 week after continuous 4-h exposure; THz frequency = 0.3 THz with continuous pulse generated at 40 µW). We found that at all the time points, the corneas and lens remained clear with no corneal haze or lens opacity formation clinically and histopathologically. No thermal effect, assessed by thermographer, was observed. The rod and cone cell-mediated electroretinography responses were not significantly altered, and the corneal keratocytes activity as well as endothelial viability, assessed by in-vivo confocal microscopy, was not affected. Post-exposed corneas, lens and retinas exhibited no significant changes in the mRNA expression of heat shock protein (HSP)90AB1), DNA damage inducible transcript 3 (DDIT3), and early growth response (EGR)1. These tissues were also negative for the inflammatory (CD11b), fibrotic (fibronectin and α-smooth muscle actin), stress (HSP-47) and apoptotic (TUNEL assay) responses on the immunohistochemical analyses. The optical transmittance of corneas did not change significantly, and the inter-fibrillar distances of the corneal stroma evaluated with transmission electron microscopy were not significantly altered after THz exposure. These results provide the basis for future research work on the development of THz imaging system for its application in ophthalmology.

Solar retinopathy: a new setting of red, green, and blue channels

Purpose:

To introduce a new color imaging technique using improved settings of red, green, and blue channels for improved delineation of retinal damage in patients with solar retinopathy.

Method:

A retrospective case series of patients with poor vision secondary to solar retinopathy were analyzed. All patients underwent visual acuity, refraction, and dilated fundus examination. A spectral domain–optical coherence tomography of the macula and color fundus imaging using optimized red, green, and blue color setting was performed. Patients were reviewed over a 6-month period. The data were analyzed for statistical significance using an independent t test and a receiver operating characteristic curve.

Results:

In total, 20 eyes of 10 patients were included between 2009 and 2017. The mean age was 24.9 ± 18.1 years. Best corrected visual acuity at first consultation was 0.78 ± 0.11 and after 6 months was 0.83 ± 0.09. Spectral domain–optical coherence tomography demonstrated retinal abnormalities at the myoid zone, ellipsoid zone, and the outer segment of photoreceptors. Receiver operating characteristic curve analysis showed an improving effect (area under the curve = 0.62; 95% confidence interval = 0.42–0.79). The color channels parameters, which improve visualization of the lesions were found to be 67-0.98-255 for the R-guided setting, 19-0.63-121 for the B-guided setting, and 7-1.00-129 for the G-guided setting. The ideal red, green, and blue setting was in 24-0.82-229.

Conclusion:

The use of a new setting of red, green, and blue channels could improve the diagnosis and monitoring of solar retinopathy, hence improving patient care.

Solar retinal phototoxicity masquerading as self-inflicted handheld laser-induced lesions

PURPOSE

To report multimodal imaging of lesions due to the unprotected observation of the sun with an astronomical telescope, mimicking self-inflicted handheld laser-induced macular lesions.

OBSERVATION

A 44-year old man was diagnosed with chronic central serous chorioretinopathy leaving a relative scotoma in his left eye, with visual acuity limited to 20/40. He complained of a sudden visual loss to 20/400. Fundus examination showed a yellowish discoloration of the fovea. Fundus autofluorescence pictures showed hyper-autofluorescent spots that were hyperfluorescent both on fluorescein and indocyanine-green angiography. Spectral-domain optical coherence tomography (SD-OCT) showed hyper-reflective foveal outer layers, and OCT-angiography showed dark areas at the choriocapillaris. Multimodal imaging was highly suggestive of self-inflicted handheld laser-induced lesions that were ruled out by the patient. He remembered having observed the sun during an astronomical session, looking for solar winds. The main astronomical telescope was protected by a specific filter, but the aiming side-telescope was incidentally not protected by any filter.

CONCLUSION AND IMPORTANCE

The unprotected observation of the sun with an astronomical telescope may result in visual loss due to macular burns that may mimic self-inflicted handheld laser-induced lesions. This hypothesis should be searched before concluding denied self-injuries.

Spectral Evaluation of Eyeglass Blocking Efficiency of Ultraviolet/High-energy Visible Blue Light for Ocular Protection

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SIGNIFICANCE

We investigated, for safety and awareness, ultraviolet and high-energy violet light–blocking protection provided by assorted types of eyewear. Ultraviolet and high-energy violet light–filtering efficiency varied and did not correlate with price or advertised claims. Standardization of methods and specifications for lens spectral transmission evaluation is recommended.

PURPOSE

Studies have linked exposure of high-energy visible blue light to effect and damage on retinal epithelial cells, photoreceptors, and ganglion cells. “Blue light” is more accurately differentiated into “high-energy visible blue-violet light” and “circadian rhythm blue-turquoise light.” This study measured and compared spectral transmission of ultraviolet and high-energy violet light of low-, medium-, and high-priced sunglasses.

METHODS

Sunglasses and lens blanks were obtained from the University of Texas Medical Branch Optical Shop and vendors. Groups were based on promotional, retail, designer sunglasses, or “blue blocker” lenses. The percent transmittance of ultraviolet/visible spectral scans (800 to 350 nm) was measured using an Agilent Cary 50 spectrophotometer. High-energy violet/blue light was defined as 400 to 450 nm.

RESULTS

Promotional sunglasses (tinted polycarbonate) blocked 100% ultraviolet and 67 to 99.8% high-energy violet blue light. Retail sunglasses filtered out 95 to 100% ultraviolet A and 67% high-energy violet light. The tested designer sunglasses varied widely in their optical transmissibility with respect to their ultraviolet A and high-energy violet light–blocking properties, with some not blocking ultraviolet A. Clear and colorless Kodak Total Blue provided maximal high-energy violet protection, whereas clear Essilor Crizal Prevencia provided less high-energy violet blocking between 400 and 450 nm.

CONCLUSIONS

The ultraviolet and high-energy violet (400 to 450 nm) light–filtering efficiency varied between sunglasses and clear lenses and did not correlate with price or advertised claims. Standardization of methods and specifications for lens spectral transmission evaluation is recommended.

Effects of an antioxidant protective topical formulation on retinal tissue of UV-exposed rabbits

PURPOSE

The aim of this study has been to evaluate the protective effect of a topical antioxidant formulation containing riboflavin, d-α-tocopheryl polyethylene glycol (TPGS vitamin E), proline, glycine, lysine, and leucine against UV-B-induced damage in in vivo rabbit retina.

METHODS

Twenty male albino rabbits were used. Animals were divided into four groups of five animals each. Control group did not receive any UV irradiation. The first group (IG) was irradiated with a UV-A lamp for 30 min; the second (IG30) and the third (IG60) groups received UV irradiation for 30 and 60 min, respectively, and were topically treated with 1 drop (approximately 50 µl) of the antioxidant formulation, every 15 min, starting 1 h before irradiation, until the end of the UC exposure.

RESULTS

The retina of IG group showed extensive destruction of the retinal pigment epithelium (RPE) and of the cones and rods layer. The retina of G30 group showed a lesser destruction of both RPE and cones and rods layer. In the G60 group, retina showed an irregular thickening of the RPE, with massive edema of the inner and outer layer immediately adjacent together with a significant reduction of the photoreceptor number.

CONCLUSION

Our results demonstrate that a topical application of eye drops containing riboflavin, d-α-tocopheryl polyethylene glycol (TPGS vitamin E), proline, glycine, lysine, and leucine counteracts UV retinal injury in exposed retina rabbits.

Tobacco smoking is an independent factor associated with retinal damage in systemic lupus erythematosus: a cross-sectional and retrospective study

To analyze the influence of tobacco smoking on systemic lupus erythematosus (SLE) clinical features and damage. Cross-sectional and retrospective, case-control study comparing SLE patients with and without tobacco exposure. Cumulative clinical data and comorbidities were collected, and severity (Katz index) and damage (SLICC/ACR damage index) (SDI) indices were calculated. Pack-years (PY) was used to estimate lifetime tobacco exposure. A logistic regression was carried out to explore the impact of tobacco use on retinal damage. 216 patients were included. The mean age was 49 years (± 12.7), 93% were females, and median disease duration was 17 years [interquartile range (IQR):9-25]. Fifty-three percent of patients were smokers at some point. The median PY was 13 (IQR: 6-20.5). Only 54.8% of active smokers recalled having been informed of the negative effects of smoking, versus 83.3% of never smokers (< 0.001). In a bivariant analysis, an association between tobacco use at any time and discoid lupus [OR: 3.5(95%CI 1.5-8.9); p = 0.002] photosensitivity [OR: 2.06(95%CI 1.16-3.7); p = 0.01] and peripheral arteriopathy (p = 0.007) was found. Considering SDI item by item, a significant association with retinal damage, adjusted for age [OR: 1.03(95%CI 1-1.07); p = 0.04], was found. Using PYs, an association was found with discoid lupus (p = 0.01), photosensitivity (p = 0.03) and peripheral arteriopathy (p = 0.01), global SDI > 0 (p = 0.002) and retinal damage (p = 0.02). In a multivariate analysis exploring factors associated with retinal damage, any previous smoking history and SDI remained associated with retinal damage. Tobacco smoking is associated with cutaneous manifestations and damage and is an independent predictor of retinal damage in SLE patients.

Blue light-filtering and violet light-filtering hydrophobic acrylic foldable intraocular lenses: Intraindividual comparison

PURPOSE

To compare the clinical outcomes after cataract surgery and implantation of a blue light-filtering IOL (AcrySof IQ SN60WF) or a violet light-filtering intraocular lens (IOL) (OptiBlue ZCB00V).

SETTING

Four surgical sites in Japan.

DESIGN

Prospective case series.

METHODS

One eye of patients with bilateral cataract was randomly allocated to the blue light-filtering IOL and the fellow eye to the violet light-filtering IOL. Visual acuity and contrast sensitivity were assessed over 3 months. The incidence of cyanopsia was evaluated using the neutralization method.

RESULTS

The study enrolled 110 eyes of 55 patients. There was no significant difference in visual acuity between the two IOLs. Based on the neutralization results 1 week postoperatively, 15 cases (27.8%) with the light-filtering IOL and 8 cases (14.8%) with the violent light-filtering IOL had cyanopsia; the difference reached statistical significance (P = .049). After 2 weeks, the difference in the incidence of cyanopsia was not significant. Postoperative contrast sensitivity under photopic condition at 1 week and 3 months and contrast sensitivity under mesopic conditions at 3 months were significantly better with the violet light-filtering IOL than with the blue light-filtering IOL (P < .05).

CONCLUSIONS

The violet light-filtering IOL yielded highly satisfactory clinical outcomes, including reduction of cyanopsia and a potential improvement in contrast sensitivity. The different chromophores of the IOL and its different material and design might have contributed.

Suspected macular light damage caused by excessive use of smartphone

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Chronic photodamage in the chicken retina using 650-nm semiconductor laser

AIM

To investigate the occurrence of chronic photodamage in the cone-based retina, following long-term exposure to a 650-nm semiconductor laser (power: 2 mW).

METHODS

Chickens fed for 1mo under natural light after hatching were irradiated with 650-nm laser light at different times each day. Fifteen animals were included in each group. Group A was a control group, irradiated with natural light during the entire study. Group B was irradiated with laser for 3 min/d. Group C was irradiated with laser for 6 min/d. Group D was irradiated with laser for 30 min/d. The duration of the light experiment was 6mo. We obtained data at 1, 3, and 6mo, including measuring the retinal thickness in vivo using optical coherence tomography, hematoxylin and eosin staining, TUNEL assay, apoptosis staining, malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, and Western blotting to detect changes in L/M opsins and rhodopsin.

RESULTS

At 1mo, the MDA content in Group D was higher than that observed in Group A (P=0.019). At 3mo the MDA content in Groups C and D was higher than that reported in Group A (P=0.026, 0.003). At 6mo, the MDA content in Groups B, C, and D was higher than that observed in Group A (P=0.038, 0.032, 0.000, respectively). There was no difference in SOD activity, and L/M opsin and rhodopsin content between the groups at 1 and 3mo. The SOD activity in group D was significantly decreased at 6mo (P=0.000), as was the content of rhodopsin. There was no significant reduction observed in retinal thickness, abnormal cell arrangement, and positive staining of TUNEL in the groups during the 6-month study period.

CONCLUSION

Irradiation using a 650 nm semiconductor laser (power: 2 mW) for 6min per day over 6mo do not cause photodamage. Similarly, a 3-month exposure of 30min per day do not cause damage. However, irradiation for 6mo resulted in a significant increase in the content of free radicals and a decrease in the content of rhodopsin in the retina, suggesting the presence of photodamage.

Long-Term Multimodal Imaging of Solar Retinopathy

This is a rare, multimodal imaging report spanning a decade of monitoring in a patient with chronic solar retinopathy showing the natural course of the disease. Spectral-domain optical coherence tomography (SD-OCT) showed mild widening of subfoveal loss of ellipsoid and interdigitation zones bilaterally, progressive retinal pigment epithelial thinning in the right eye, and hyperplasia in the left eye. Structural en face OCT showed subfoveal tissue loss bilaterally. There was no leakage on fluorescein angiography and OCT angiography (OCTA), and dense B-scan OCTA images were unremarkable. Microperimetry revealed bilateral decreased central sensitivity and eccentric fixation in the left eye. Vision remained stable throughout. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:388-392.].

Drone retinopathy

Purpose

To report a case of solar retinopathy due to inadvertent exposure to the sun while piloting a drone without protective eyewear.

Methods

A 29-year-old male underwent a complete eye exam including optical coherence tomography (OCT) of the macula.

Results

Bilateral juxtafoveal outer retinal microcystic cavities present on OCT consistent with solar retinopathy.

Conclusion

With the increasing popularity of unmanned aircrafts, eye protection awareness during drone use is essential.