Blue light induced ferroptosis via STAT3/GPX4/SLC7A11/FTH1 in conjunctiva epithelium in vivo and in vitro

The prevalence of Light-emitting diodes (LEDs) has exposed us to an excessive amount of blue light (BL) which causes various ophthalmic diseases. Previous studies have shown that conjunctiva is vulnerable to BL. In this study, we aimed to investigate the underlying mechanism of BL-induced injury in conjunctiva. We placed C57BL/6 mice and human conjunctival epithelial cell lines (HCECs) under BL (440 nm ± 15 nm, 0.2 mW/cm2) to establish a BL injury model in vivo and in vitro. Immunohistochemistry and MDA assay were used to identify lipid peroxidation (LPO) in vivo. HE staining was applied to detect morphological damage of conjunctival epithelium. DCFH-DA, C11-BODIPY 581/591, Calcein-AM, and FeRhoNox™-1 probes were performed to identify ferroptosis levels in vitro. Real-time qPCR and Western blotting techniques were employed to uncover signaling pathways of blue light-induced ferroptosis. Our findings demonstrated that BL affected tear film instability and induced conjunctival epithelium injury in vivo. Ferrostatin-1 significantly alleviated blue light-induced ferroptosis in vivo and in vitro. BL downregulates the levels of solute carrier family 7 member 11 (SLC7A11), Ferritin heavy chain (FTH1), and glutathione peroxidase (GPX4) by inhibiting the activation and translocation of the Signal transducer and activator of transcription 3 (STAT3) from inducing Fe2+ burst, ROS and LPO accumulation, ultimately resulting in ferroptosis. This study will offer new insight into BL-induced conjunctival injury and LED-induced dry eye.

Corneal Epithelial Cell Density Is Reduced in Young Adults With Conjunctival Ultraviolet Autofluorescence

PURPOSE

The aim of this study was to investigate the effects of chronic ultraviolet (UV) radiation exposure on the corneal microstructure using conjunctival UV autofluorescence (CUVAF) as a marker of exposure.

METHODS

Young healthy adults aged 18 to 35 years were recruited. Participant's demographics and sun exposure behavior were recorded using questionnaires. Images of the bulbar conjunctiva from the right eye were captured and analyzed for the CUVAF area. Corneal microstructure was assessed by in vivo confocal microscopy and anterior segment optical coherence tomography. The presence of palisades of Vogt in all 4 limbal quadrants was recorded.

RESULTS

CUVAF was observed in 31 of 52 eyes (60%), with a mean (±SD) nasal, temporal, and total CUVAF area of 5.39 ± 4.16 mm 2 , 4.29 ± 4.27 mm 2 , and 9.67 ± 7.01 mm 2 , respectively. Individuals with CUVAF were significantly more likely to report undertaking moderate-intensity to high-intensity outdoor exercise ( P = 0.021). Individuals with CUVAF were less likely to have visible nasal and temporal palisades of Vogt ( P = 0.011). Corneal basal cell densities anterior to the nerve whorl ( P < 0.001) and nasally ( P = 0.005) were lower in individuals with CUVAF. Wing cell density anterior to the nerve whorl was lower in individuals with CUVAF ( P = 0.011). No significant changes in the central and limbal corneal epithelial thickness were observed.

CONCLUSIONS

Significant reductions in corneal epithelial cell density were observed in individuals with CUVAF, a biomarker of chronic UV exposure. This observation suggests that chronic UV exposure is damaging to the corneal microstructure.

Blue Light Induces Impaired Autophagy through Nucleotide-Binding Oligomerization Domain 2 Activation on the Mouse Ocular Surface

In this study, we investigated the effects of blue light exposure on nucleotide-binding oligomerization domain 2 (NOD2) expression on the mouse ocular surface and evaluated the role of NOD2 activation in light-induced cell death. Mice were divided into wild-type (WT), NOD2-knock out (KO), WT + blue light (WT + BL), and NOD2-KO + blue light (NOD2-KO + BL) groups, and the mice in the WT+BL and NOD2-KO + BL groups were exposed to blue light for 10 days. After 10 days of blue light exposure, increased reactive oxygen species and malondialdehyde were observed in the WT + BL and NOD2-KO + BL groups, and the WT + BL group showed a higher expression of NOD2 and autophagy related 16 like 1. Although both WT+BL and NOD2-KO + BL groups showed an increase in the expression of light chain 3-II, NOD2-KO + BL mice had a significantly lower p62 expression than WT + BL mice. In addition, NOD2-KO+BL mice had significantly lower corneal epithelial damage and apoptosis than WT + BL mice. In conclusion, blue light exposure can induce impaired autophagy by activation of NOD2 on the ocular surface. In addition, the reactive oxygen species (ROS)-NOD2-autophagy related 16 like 1 (ATG16L) signaling pathway may be involved in the blue-light-induced autophagy responses, resulting in corneal epithelial apoptosis.

UV damage of the anterior ocular surface - microstructural evidence by in vivo confocal microscopy

PURPOSE

To evaluate and describe the microstructural changes at the ocular surface in response to habitual ocular sun exposure, correlate them with the UV protection habits and follow their dynamics using in vivo confocal microscopy(ICM).

METHODS

For a period of minimum 4 months 200 subjects (400 eyes), aged 28 ± 7.3 years, were recruited with the agreement that they will spend their summer exclusively in the region of the Black Sea coast at 43 °N latitude and will be examined before and after the summer. All subjects filled in a questionnaire about habitual UV protection and were examined clinically and by ICM.

RESULTS

Questionnaire results demonstrated that 83.5% (167 participants) of the subjects considered the sun dangerous for their eyes, but 78% (156 subjects) believed that there is danger exclusively during the summer period. Although no clinical changes were detected, microstructural analysis of the cornea demonstrated statistically significant (p = 0.021) decrease of the basal epithelial density - from 6167 ± 151 cells/mm² before to 5829 ± 168 cells/mm² after the summer period. Microstructural assessment of the conjunctiva demonstrated characteristic cystic lesions with dark centres and bright borders encountered in only 25 eyes(6%) before, and affecting 118 eyes(29.5%) after the summer. The total area of the cysts after the summer increased fivefold. Spearman analysis proved negative correlation between sun protection habits and number of cysts.

CONCLUSION

Summer sun exposure for one season leads to clinically undetectable, microstructural changes affecting the cornea, bulbar and palpebral conjunctiva with transient, but possibly cumulative nature.

Blue light phototoxicity toward human corneal and conjunctival epithelial cells in basal and hyperosmolar conditions

AIMS

The ocular surface is the very first barrier between the visual system and external environment. It protects the eye from the exposure to various light sources that significantly emit in blue spectrum. However, the impact of blue light on the ocular surface has been poorly explored so far. In this study, we investigated in vitro the phototoxicity of blue light illumination in human epithelial cells of the ocular surface. We worked either in basal conditions or under hyperosmolar stress, in order to mimic dry eye disease (DED) that is the most common disease involving the ocular surface.

RESULTS

Corneal and conjunctival epithelial cells suffered the most from violet-blue light but also from longer-wave blue light. Exposure to blue wavebands significantly decreased cellular viability, impacted on cellular morphology and provoked reactive oxygen species (ROS) over-production. Conjunctival epithelial cell line had a greater photosensitivity than the corneal epithelial one. Hyperosmolar stress potentiated the blue light phototoxicity, increasing inflammation, altering mitochondrial membrane potential, and triggering the glutathione-based antioxidant system.

INNOVATION

In human epithelial corneal and conjunctival cells of the ocular surface, we demonstrated the harmful impact of blue light on viability, redox state and inflammation processes, which was modified by hyperosmolarity.

CONCLUSION

Blue light induced cell death and significant ROS production, and altered the expression of inflammatory genes and operation of the cellular defensive system. We established for the first time that hyperosmolar stress impacted phototoxicity, further suggesting that DED patients might be more sensitive to blue light ocular toxicity.

Different Therapeutic Approaches and Outcome in the Treatment of Pterygium

Purpose

This study was initiated to investigate the role of different therapeutic modalities in the outcome of the surgical treatment of pterygium.

Methods

The results of treatment of pterygia with a variety of surgical techniques were studied in 56 eyes (49 patients) operated on at Bristol Eye Hospital during a period of five years. The surgical techniques included simple excision; bare sclera; conjunctival autograft; sliding conjunctival flap; lamellar keratoplasty and penetrating keratoplasty. Twelve eyes received additional beta irradiation in a fractionated total dose of 40 Gys.

Results

The incidence of recurrence was 23.2% for the 43 treated primary pterygia, and 23% for the 13 recurrent pterygia. All recurrences occurred between 2.5 and 11 months postoperatively. None of the 11 cases where additional beta irradiation was used showed any recurrence or other complication within the study period. In the recurrent pterygia group, the cases treated with a combination of surgical excision and beta irradiation, showed significantly lower recurrence rate (p<0.001) compared to those cases treated with surgical excision alone.

Conclusions

Beta irradiation as a complement to surgical treatment of pterygium, is successful in treating high risk cases such as reoperations, whereas for the majority of primary pterygia surgical excision alone is adequate. Additionally, follow up of one year will reveal any recurrences.

Dry eye following cataract surgery: The effect of light exposure using an in-vitro model

PURPOSE

Cataract surgery can lead to the temporary development or worsening of dry eye symptoms. Contributing factors may include corneal incisions, agents used before, during or after surgery, light from the operating microscope, disruption of ocular surface tissues and inflammatory processes. The purpose of this study was to observe the effect of light exposure on conjunctival fibroblasts in order to determine whether light has an effect on wound healing closure, assuming that operating microscopes might have an effect on the ocular surface.

METHOD

An in vitro scratch assay was performed on porcine conjunctival fibroblasts. Ten minutes of light exposure from a light microscope with a halogen bulb was performed after the scratch assay. Fibroblasts were kept in culture for 48 hours post-exposure and the wound closure rates were visualized by live/dead staining. The fibroblasts which were exposed to light were compared to those without light exposure. Cell viability was also analysed by MTT assay.

RESULTS

A Slower wound closure rate was found when fibroblasts were exposed to light compared to the non-light exposed controls. Cell viability reduced by 20% with light exposure compared to controls in p3 cells (p = 0.04; however, the trend was not observed with p4 and p5 cells (p > 0.05).

CONCLUSIONS

These results suggest that light exposure might be one of the possible contributory factors for dry eye after ophthalmic surgery. Further evaluation of light effects should be carried out with different ocular surface cells.

Conjunctival Ultraviolet Autofluorescence as a Measure of Past Sun Exposure in Children

Background: Conjunctival ultraviolet autofluorescence (CUVAF) area detected from UVAF photographs is a recently developed potential marker for past sun exposure, but its relationship with sun-related factors has not been fully investigated.Methods: The study included 339 healthy children ages 5 to 15 years in Melbourne, Australia. Data were collected by questionnaire and examination at school. CUVAF area was measured using a computer program and analyzed as a continuous and dichotomous outcome (any/none).Results: Fifty-three children (15.6%) had detectable CUVAF, and the youngest age at which a child showed sun damage was 8 years. Compared with silicone skin cast score, there was good inter-grader agreement on CUVAF grading, with Cohen kappa 0.85 [95% confidence interval (CI), 0.65-1.00] for total CUVAF area using both eye photographs. Perfect intra-grader agreement was achieved. Fairer pigmentation, including medium/fair skin color [adjusted odds ratio (AOR), 3.42; 95% CI, 1.02-11.48 vs. dark/olive] and blue/gray eye color (AOR, 4.07; 95% CI, 1.73-9.55 vs. brown) was associated with increased odds of CUVAF. Increasing lifetime sunburn number (e.g., AOR, 2.89; 95% CI, 1.14-7.35 and 4.29; 1.04-17.76 for sunburns 2 to 4 and ≥ 5 times, respectively, vs. no sunburns, trend P = 0.004) and freckling by the end of last summer were associated with increased odds of CUVAF.Conclusions: CUVAF area can be an a priori objective measure of past sun exposure in pediatric populations for future research.Impact: To our knowledge, this is the first pediatric study that evaluated associations of sun-related risk factors with CUVAF. Cancer Epidemiol Biomarkers Prev; 26(7); 1146-53. ©2017 AACR.

The Discovery of an Unusual Cause of Indoor Radiation Pollution

The objective of our study is to investigate the reasons why 21 persons suffered erythema and other skin changes, and conjunctivae infection after staying in a closed room for three hours. A multi-disciplinary case study including interviews, building and ventilation inspections, was performed by a multidisciplinary team comprising a medical epidemiologist, and an industrial hygienist. A self-administered questionnaire was designed to determine the magnitude of the health problem of the affected students. By a process of investigative elimination, we deduced that the symptoms were caused by accidental exposure to ultraviolet C radiation where it was radiated from the germicidal ultraviolet lamps. The most common symptoms and signed presented were erythema of skin and conjunctivae infection. The erythema of skin and conjunctivae infection arose from exposure to ultraviolet C radiation and that safeguards are needed to ensure ultraviolet germicidal lamps are not accidentally switched on while a room is occupied.

Changes in the eyelids and conjunctiva caused by ultraviolet radiation

The aim of this study was to show the frequency, sex and age distribution of eyelids skin tumor changes and degen erative changes of the conjunctiva for the period of three years (2011-2013) at the Department of Ophthalmology in Split. We analyzed the eyelids skin lesions in biopsy material at the Department of Pathology and the same were compared with the profession of the patients. In this period there were found 131 tumor changes of the eyelids. The most common tumor was the basal cell carcinoma (118) with the higher frequency in women. There were 10 squamous cell carcinomas with the equal representation among sexes and three melanomas. There were 79 female and 52 male patients. There were 299 pterygiums operated with the higher frequency in women (68.2%). Exposure to UV radiation, particulary UVB radiatiori is the most common causative factor for genetic abnormalities in cells and provoked factor in oncogenesis of skin tumors. In our research we found a correlation between changes in the eyelids and conjunctiva caused by UV radiation with the professional interest of the respondents. Due to high incidence of eyelids skin tumor changes in the population professionally exposed to UV radiation, medical professionals should be aware of the importance of the public education on the etiology of these tumors and the importance of the UVprotection.

[Morphologically reasonable application of 1.44 microm Nd:YAG laser in ocular surgery for distant hemostasis in conjunctival and episcleral vessels]

The article discusses morphological changes in bulbar conjunctiva and episclera after experimental exposure to Nd:YAG laser radiation at 1.44 pm in comparison to the effect of diathermal coagulator Mira TR4000. The results proved the use of 1.44 microm Nd:YAG laser in ocular surgery for distant hemostasis morphologically reasonable. Non-contact and directional laser treatment is more delicate as it produces smaller irradiated area. The depth of penetration and tissue heating is very limited. Neither excessive reparation, nor scarring is found in the exposed area. On the contrary, diathermy is a contact procedure associated with irregular distribution of heat, which causes large tissue burns and necrosis with subsequent adherent scar formation.

The association between pterygium and conjunctival ultraviolet autofluorescence: the Norfolk Island Eye Study

PURPOSE

To investigate the association between conjunctival ultraviolet autofluorescence (UVAF), a biomarker of ocular ultraviolet radiation (UVR) exposure, and prevalent pterygium.

METHODS

We conducted a cross-sectional study on Norfolk Island, South Pacific. All permanent residents aged ≥15 were invited to participate. Participants completed a sun exposure questionnaire and underwent autorefraction and slit lamp biomicroscope examination. Area of conjunctival UVAF (sum of temporal/nasal area in right and left eyes) was determined using computerized methods. Multivariate logistic and linear regression models were used to estimate the associations with pterygia and UVAF, respectively.

RESULTS

Of 641 participants, 70 people (10.9%) had pterygium in one or both eyes, and prevalence was higher in males (15.0% versus 7.7%, p = 0.003). Significant independent associations with pterygium in any eye were UVAF (per 10 mm(2)) [odds ratio (OR) 1.16, 95% confidence interval (CI) 1.16-1.28, p = 0.002], tanning skin phenotype (OR 2.17, 1.20-3.92, p = 0.010) and spending more than three-quarters of the day outside (OR 2.22, 1.20-4.09, p = 0.011). Increasing quartile of UVAF was associated with increased risk of pterygium following adjustment of age, sex and time outdoors (p(Trend) = 0.002). Independent associations with increasing UVAF (per 10 mm(2)) were decreasing age, time outdoors, skin type and male gender (all p < 0.001). UVAF area correlated well with the duration of outdoor activity (p(Trend) < 0.001).

CONCLUSION

Pterygium occurs in approximately one-tenth of Norfolk Islanders. Increasing conjunctival UVAF is associated with prevalent pterygia, confirming earlier epidemiological, laboratory and ray-tracing studies that pterygia are associated with UVR. Protection from the sun should be encouraged to reduce the prevalence of pterygium in the community.

Actinic conjunctivitis in children: Clinical features, relation to sun exposure, and proposed staging and treatment

BACKGROUND

Actinic conjunctivitis is an ocular photosensitivity reaction found mainly in children in certain populations in the Andean regions of South America, Mexico, and in the southwestern United States. Its clinical features, treatment, and possible relation to duration of sun exposure have not been fully described in the ophthalmologic literature.

METHODS

A 20-member ophthalmic team traveled to an Andean region of Ecuador to provide ophthalmic care to children. All children with conjunctivitis were examined. A novel 3-stage classification of actinic conjunctivitis, devised by one of the authors, was used to stage the disease. The parents of each child with actinic conjunctivitis were asked how much time the child spent outside. Histopathological evaluations were performed on children who underwent surgery.

RESULTS

A total of 206 children were examined, of whom 36 had changes consistent with actinic conjunctivitis. Stage 1 disease was diagnosed in 17 children, stage 2 in 9, and stage 3 in 10 in the most severely affected eye. The amount of time the child spent outside correlated with disease severity (r = 0.77, p < 0.001). Histopathologic samples showed an intense inflammatory response with hyperplasia of the vascular endothelium, pigmentary migration, and occasional eosinophilia.

CONCLUSIONS

Actinic conjunctivitis is prevalent among children of the highlands of Ecuador. Although it has an allergic component, our data suggest that the severity of the disease is significantly associated with sun exposure. The finding that the lesions are found only in the exposed conjunctiva supports the hypothesis that UV exposure is the main cause of the disease.

Lymphocytic reaction to ultraviolet radiation on rabbit conjunctiva

We examined the clinical and histological effects of controlled UV radiation on the conjunctiva and cornea of rabbit eyes by duration of exposure (0.5-4 hours daily for 5 consecutive days). Longer UV exposure (day 1-day 5) was associated with increased conjunctival redness, corneal erosion, edema and opacity. This study shows that UV irradiation leads to clinical and histological changes which may reflect an immune reaction to damaged epithelial cells.

Cytoprotective effect against UV-induced DNA damage and oxidative stress: Role of new biological UV filter

The majority of chemical solar filters are cytotoxic, particularly on sensitive ocular cells (corneal and conjunctival cells). Consequently, a non-cytotoxic UV filter would be interesting in dermatology, but more especially in ophthalmology. In fact, light damage to the eye can be avoided thanks to a very efficient ocular antioxidant system; indeed, the chromophores absorb light and dissipate its energy. After middle age, a decrease in the production of antioxidants and antioxidative enzymes appears with accumulation of endogenous molecules that are phototoxic. UV radiations can induce reactive oxygen species formation, leading to various ocular diseases. Because most UV filters are cytotoxic for the eye, we investigated the anti-UV properties of Calophyllum inophyllum oil in order to propose it as a potential vehicle, free of toxicity, with a natural UV filter action in ophthalmic formulation. Calophyllum inophyllum oil, even at low concentration (1/10,000, v/v), exhibited significant UV absorption properties (maximum at 300nm) and was associated with an important sun protection factor (18-22). Oil concentrations up to 1% were not cytotoxic on human conjunctival epithelial cells, and Calophyllum inophyllum oil appeared to act as a cytoprotective agent against oxidative stress and DNA damage (85% of the DNA damage induced by UV radiations were inhibited with 1% Calophyllum oil) and did not induce in vivo ocular irritation (Draize test on New Zealand rabbits). Calophyllum inophyllum oil thus exhibited antioxidant and cytoprotective properties, and therefore might serve, for the first time, as a natural UV filter in ophthalmic preparations.

Differential Mechanisms of Conjunctival Cell Death Induction by Ultraviolet Irradiation and Benzalkonium Chloride

PURPOSE

To determine the molecular mechanisms of conjunctival cell death on exposure to the quaternary ammonium preservative benzalkonium chloride (BAC) and ultraviolet (UV) irradiation.

METHODS

Chang conjunctival cells, either wild-type or stably transfected with various constructs encoding antiapoptotic molecules or transiently transfected with siRNA targeting the beclin-1 gene, were exposed to BAC or UV radiation Cell death was analyzed morphologically with fluorescence and electron microscopy, and molecular mechanisms of death were studied by using immunofluorescence, cell fractionation, caspase substrates, and immunoblot analysis, with or without immunoprecipitation. The main results were controlled in IOBA-NHC cells.

RESULTS

Both agents induced cytochrome c release from the mitochondria, caspase activation, and nuclear chromatin condensation, suggesting caspase-dependent apoptosis. These events are prevented by stable expression of Bcl-2 protein. Both agents also induced a redistribution of Fas in plasma membrane rafts and the Fas-ligand-independent formation of a death-inducing complex leading to caspase-8 activation. Stable expression of either a dominant negative construct of Fas-associated death domain (FADD) or the long or short isoform of FADD-like interleukin-1-beta-converting enzyme inhibitory protein (FLIP) inhibited caspase-8 activation in response to both UV radiation and BAC. However, these proteins, as well as permeant peptides and baculovirus p35 caspase-inhibitors, delayed more efficiently the UV irradiation-induced than the BAC-induced nuclear chromatin condensation. BAC specifically activated a caspase-independent pathway by inducing the mitochondrial release of apoptosis-inducing factor. BAC-treated cells contain autophagosomes/autolysosomes, a characteristic feature of autophagy, and siRNA-mediated downregulation of the beclin-1 gene, whose product is crucial for autophagy, increases BAC toxicity.

CONCLUSIONS

UV irradiation induces typical, caspase-dependent cell death, whereas death induced by BAC associates features of caspase-dependent and -independent apoptosis counteracted by an autophagic process.

Ultraviolet fluorescence photography to detect early sun damage in the eyes of school-aged children

PURPOSE

To develop a method to detect precursors of ocular sun damage using ultraviolet fluorescence photography (UVFP).

DESIGN

Observational cross-sectional study

METHODS

settings: Preschool, primary, and high school in Sydney, Australia. study population: 71 children ages 3 to 15 years old (both eyes). Inclusion criteria were children attending the schools who gave consent. There were no exclusion criteria. observation procedures: UV and standard (control) photographs were taken of the nasal and temporal interpalpebral regions bilaterally. main outcome measures: Presence of areas of increased fluorescence detected by UVFP, or presence of pinguecula detected by standard photography.

RESULTS

Established pingueculae, on standard photography, were seen in seven of 71 (10%) children; all were 13 years of age or older. On UVFP, all of these pingueculae demonstrated fluorescence. In total, 23 of 71 (32%) had increased fluorescence detected on UVFP, including the seven of 23 (30%) with pingueculae. Of the remaining 16 of 23 (70%), the changes were only detectable using UVFP. Fluorescence on UVFP was seen in children ages 9 years and above, with prevalence increasing with age. The presence of fluorescence (in at least one region) was 0 of 15 (0%) for children ages 3 to 5 years, 0 of 12 (0%) of children ages 6 to 8 years, 6 of 23 (26%) for those ages 9 to 11 years, and 17 of 21 (81%) of those ages 12 to 15 years.

CONCLUSIONS

We hypothesize that the areas seen to fluoresce on UVFP but not detectable on control photography represent precursors for ophthalmohelioses. Our preliminary data strongly suggests that UVFP is a sensitive method for detecting early ocular sun damage occurring many years before clinical manifestations.

Epidermal growth factor receptor signaling is partially responsible for the increased matrix metalloproteinase-1 expression in ocular epithelial cells after UVB radiation

Pterygia are inflammatory, invasive, and proliferative lesions of the human ocular surface in which the matrix metalloproteinase (MMP) collagenase-1 (MMP-1) is highly expressed. Pterygia development may involve MMP-1 activity against interstitial fibrillar collagen, an abundant extracellular matrix component of the cornea, and its induction by ultraviolet light (UVB). We examined the pathways responsible for enhanced expression of MMP-1 in pterygium epithelial cells after UVB exposure and/or treatment with chemical inhibitors of mitogen-activated protein kinases or epidermal growth factor receptor. The induction of MMP-1 by UVB was comparable to that mediated by heparin-binding epidermal growth factor-like growth factor and epidermal growth factor. The epidermal growth factor receptor inhibitor PD153035 partially blocked the UVB-mediated induction of MMP-1 and totally abrogated its production after stimulation with either heparin-binding epidermal growth factor-like growth factor or epidermal growth factor. UVB exposure enhanced the phosphorylated form of ERK1/2 in a time-dependent manner whereas the ERK1/2 inhibitor PD98059 decreased this induction by at least fivefold. Transcripts for c-jun and c-fos were detected as early as 2 hours after UVB exposure and were suppressed by PD98059. The identification of a specific intracellular signaling pathway responsible for the enhanced production of a key enzyme that denatures intact fibrillar collagen has important implications for understanding the pathophysiology and future therapy for pterygia.

The Effect of Octreotide Against Oxidative Damage in Photosensitized Conjunctiva and Cornea of Rabbits

The purpose of this study was to determine the protective effect of octreotide against oxidative damage in rabbit conjunctiva and cornea exposed to ultraviolet radiation. Twenty rabbits weighing 2,500-3,000 g were used and we divided them into 4 groups with randomly selected 5 rabbits. Rabbits were exposed to 2 J/cm(2)/h of ultraviolet A radiation (UVA) in the range 320-405 nm for 12 h per day for 90 days. Group 1 did not receive any treatment or UVA exposure (control group). Group 2 was only exposed to UVA radiation (UVA group). Group 3 received 8-methoxypsoralen and UVA (PUVA group). Group 4 was treated with 8-methoxypsoralen + UVA + octreotide (octreotide group). At the end of 90 days the rabbits were killed by decapitation and then eyes were enucleated. Both eyes of each rabbit were used for histopathologic evaluation. Histopathologic analysis of each group indicated that UVA group and PUVA group showed increasing edema (p<0.01), inflammation (p<0.05), fibroblast proliferation (p<0.05), dysplasia (p<0.05), hyperchromasia (p<0.01) in the conjunctiva. Octreotide group had significant protective effect in comparison with the UVA group and PUVA group. The UVA group and PUVA group showed increasing proliferation (p<0.01), dysplasia (p<0.01), hyperchromasia (p<0.01), pyknosis (p<0.001) and parakeratosis (p<0.01) in the corneal epithelium. Octreotide group showed similar results with control group. We conclude that octreotide which is considered as free radical scavenger protects the eye from the damaging effect of UV exposure.

The protective effect of alpha-lipoic acid against oxidative damage in rabbit conjunctiva and cornea exposed to ultraviolet radiation

PURPOSE

The purpose of this study was to determine the protective effect of alpha-lipoic acid against oxidative damage in rabbit conjunctiva and cornea exposed to ultraviolet radiation.

METHODS

20 rabbits weighing 2,500- 3,000 g were used, and we divided them into 4 groups with 5 randomly selected rabbits. The rabbits were exposed to 2 J/cm(2)/h of ultraviolet A radiation (UVA) in the range of 320-405 nm for 12 h per day within 90 days. The control group did not undergo any procedure, the UVA group was only exposed to UVA radiation. The PUVA group was treated with 8-methoxypsoralen and UVA. The alpha-lipoic acid group was administered 8-methoxypsoralen + UVA + alpha-lipoic acid. At the end of 90 days, the rabbits were killed by decapitation, and the eyes were enucleated. Both eyes of each rabbit were used for biochemical evaluation. Conjunctival and corneal free malondialdehyde (MDA), glutathione peroxidase (GSH-PX) and superoxide dismutase (SOD) levels were compared among the groups.

RESULTS

Conjunctival free MDA levels were lower in the alpha-lipoic acid group compared with the UVA and PUVA groups (p < 0.05, p < 0.001, respectively). Both conjunctival SOD levels (p < 0.05, p < 0.01, respectively) and conjunctival GSH-PX levels (p < 0.01, p < 0.001, respectively) were higher in the alpha-lipoic acid group compared with other groups. Corneal free MDA levels were lower in the alpha-lipoic acid group compared with the UVA and PUVA groups (p < 0.01, p < 0.001, respectively). Both corneal SOD levels (p < 0.01, p < 0.01, respectively) and corneal GSH-PX levels (p < 0.01, p < 0.01, respectively) were higher in the alpha-lipoic acid group compared with the other groups.

CONCLUSION

alpha-Lipoic acid which is considered as potent antioxidant protects the eye from the damaging effect of ultraviolet exposure.

Iodide protection from UVB irradiation-induced degradation of hyaluronate and against UVB-damage of human conjunctival fibroblasts

BACKGROUND

To determine whether iodide protects from UVB irradiation-induced destruction of hyaluronate and against UVB injury of cultured human conjunctival fibroblasts.

METHODS

Hyaluronate and primary cultured human conjunctival fibroblasts were incubated with various concentrations of iodide and then exposed to UV light irradiation of 312 nm. Hyaluronate destruction was determined by viscosity measurements. Cell viability was assessed with MTT assay.

RESULTS

Iodide protects hyaluronate from UVB light-induced degradation of this macromolecule in a concentration-dependent manner. Incubation of human conjunctival fibroblasts with iodide inhibited cells from damage by UVB light.

CONCLUSION

Iodide protects hyaluronate, a component of tear fluid and tissues of the anterior part of the eye, against UVB light-induced degradation. Also, injury of human conjunctival cells can be prevented by incubation with iodide before UVB irradiation. The mechanism of protection is likely to include an antioxidative reaction. To support the natural defence mechanisms of the eyes, the administration of an antioxidant such as iodide to artificial tears, for example, may help to prevent the damage of the eye provoked by oxidative stress.

Photokeratitis and other phototoxic effects on the cornea and conjunctiva

Except when sleeping, the cornea and interpalpebral conjunctiva are exposed to the ambient environment, both natural and man-made. Levels of solar ultraviolet irradiance reaching the eye may exceed the damage threshold under a number of circumstances. The consequences of overexposure may be acute after a latent period, sequelae to an acute exposure, or long-term chronic effects. Previously derived action spectra for photokeratitis and photoconjunctivitis due to incoherent ultraviolet are presented. These reveal interspecies similarities for the levels of radiant energy reaching each tissue. The initial in vivo (clinical) signs of photokeratitis are due to lost or damaged epithelial cells with other signs produced by this primary response. The conjunctival signs include injection and chemosis. Chronic exposure to solar ultraviolet is a factor in climatic droplet keratopathy and pterygium. Phototoxic compounds or their by-products potentially can reach the cornea from the air, via the tears or aqueous humor, or from the limbal capillaries. However, the human cornea appears to be much less susceptible to the influence of phototoxic agents than the skin.

UVB-mediated induction of interleukin-6 and -8 in pterygia and cultured human pterygium epithelial cells

PURPOSE

Pterygia are common ocular surface lesions that are thought to be induced by exposure to ultraviolet (UV) radiation. The hypothesis tested in the current study is that UV radiation modulates the expression of interleukin (IL)-6 and -8, which could promote the neovascularization and chronic inflammation regularly observed in pterygia.

METHODS

Immunohistochemical analysis was performed on 10 pterygia and 14 specimens of normal conjunctiva (4 of which contained limbus), to identify the cellular source of these cytokines. Pterygium epithelial cells were exposed to UVB (0-100 mJ/cm(2)) and the expression of cytokine mRNA and protein was determined by reverse transcription-polymerase chain reaction (RT-PCR), RNase protection assay (RPA), and enzyme immunoassay. Similarly, pterygium tissue in organ culture was UVB irradiated and the supernatants analyzed for cytokine production.

RESULTS

IL-6 and -8 proteins were abundantly expressed, predominantly by the pterygium epithelium, with additional IL-8 immunoreactivity associated with the vascular endothelium. In contrast, significantly less staining for both cytokines was observed in normal conjunctiva, cornea, and limbus. Expression of both IL-6 and -8 mRNA and protein was induced in UVB-irradiated pterygium epithelial cells in a time- and dose-dependent manner. Similarly, IL-6 and -8 proteins were significantly elevated in UVB-treated compared with nonirradiated pterygia.

CONCLUSIONS

This study provides the first direct experimental evidence that implicates UV in the pathogenesis of pterygia. The two proinflammatory cytokines that are induced by UV radiation may play a key role in the development of pterygia, by initiating blood vessel formation, cellular proliferation, tissue invasion, and inflammation. Strategies aimed at reducing ocular exposure to UV light may decrease the incidence and recurrence of pterygia.

Telomerase activity and p53 expression in pterygia

PURPOSE

To investigate tolomerase activity and p53 expression in pterygial tissue.

METHODS

Pterygia tissue was obtained during excisional surgery fr om 35 eyes of 35 patients, and superior bulbar conjunctival tissue from the same eye was also sampled as control when possible. Fluorescence telomeric repeat amplification protocol was used to measure telomerase activity in whole pterygium samples from 9 cases and in the epithelium and stroma of pterygium from another 10 cases. p53 protein content was measured by enzyme-linked immunosorbent assay (ELISA) in tissues obtained from 7 eyes, as well as in epithelial cell suspensions collected by brush cytology in 8 eyes. Six samples were also analyzed for UV-specific mutations in the p53 gene by the single-strand conformation polymorphism technique and DNA sequencing. A conjunctival epithelial cell line was irradiated with sublethal levels of UV-B to investigate whether telomerase activity can be induced in vitro.

RESULTS

In all, 63% of pterygia samples demonstrated telomerase activity, whereas all 10 paired conjunctival control samples were negative (P = 0.05, chi-square test). Of the 10 samples in which telomerase activity was measured separately in the epithelium and stroma of pterygia, 5 samples were positive in the epithelium, only 1 of which had activity in the stroma. Average telomerase activity in positive samples was 18.44 +/- 8.77 U/microg protein, compared with telomerase activity measured in a carcinoma in situ patient (33.73 U/microg), and in an immortalized conjunctival epithelial cell line (50.72 +/- 15.55 U/microg). Telomerase activity was not upregulated in this cell line by UV-B exposure. All 6 pterygia samples tested for p53 mutations did not reveal the UV-specific mutations in exons 5, 6, 7, or 8. No statistical significance was observed in the pterygium or conjunctiva p53 protein levels in epithelial cells collected by brush cytology, while p53 protein level was lower in pterygia when measured in whole tissue samples.

CONCLUSIONS

Telomerase activity was detected in some pterygia, mostly in the epithelium. Pterygia was not associated with an increase in epithelial p53 protein content measured by ELISA.

[Microcirculatory changes in patients with ischemic heart disease under the influence of laser irradiation]

As shown by conjunctival biomicroscopy, microcirculatory picture in 176 patients with coronary heart disease (CHD) compared to that of 76 healthy controls exhibited gross changes in the terminal vascular bed. 36 CHD patients have received laser treatment. Positive trends correlating with clinical response were registered in these laser-treated patients.

[The blood circulation and microcirculation in the diagnosis of the DIC syndrome in cerebral circulatory disorders in subjects exposed to the effect of ionizing radiation]

A clinical and laboratory investigation was done in 103 patients presenting with early cerebral circulation disorders, who took part in the elimination of the effects of the Chernobyl accident. Clinical features were studied as was the state of homeostasis and of microcirculation. Employment of a complex of clinical-and-biochemical and microcirculatory techniques permits diagnosing DBC syndrome manifestable both in acute and chronic post-radiation cerebral dyscirculation. Biomicroscopy of the bulbar conjunctiva vessels and investigation into the molecular and cellular homeostasis allow the signs of syndrome development to be revealed, its further course to be prognosticated, control over the efficiency of the treatments administered to be exercised.

Transscleral ciliary body photodynamic therapy using phthalocyanine and a diode laser: functional and morphologic implications in albino rabbits

BACKGROUND AND OBJECTIVES

To evaluate the morphologic and functional effects of ciliary body photodynamic therapy (PDT) using phthalocyanine and a diode laser.

MATERIALS AND METHODS

The upper half of the left eye ciliary body of 16 albino rabbits was irradiated transsclerally using a 670-nm diode laser (400 mW/cm2) after intravenous injection of phthalocyanine (6 mg/kg). The animals were observed for a maximum of 2 months by means of tonometry, biomicroscopy, and fundus examination. At the end of the follow-up period, they were killed and their eyes were prepared for light and electron microscopy.

RESULTS

Transscleral PDT resulted in intraocular pressure (IOP) reduction in the treated eye, which lasted about 2 weeks. During this time, the treated eye had IOP values that were significantly lower than its baseline IOP values and the IOP values of the untreated eye (P < .05). One month after the procedure, the IOP had returned to baseline values. Histologic examination revealed vascular endothelial cell damage causing vascular thrombosis in the treated areas. The architecture of the two ciliary epithelium layers showed a significant abnormality. Disappearance of epithelial apical junction complexes and loss of the normal b-cytomembrane enfolding were observed in the course of electron microscopic examination. Large intercellular spaces between epithelial cells were noticed. All of these changes had subsided by the end of the second postoperative month.

CONCLUSION

Transscleral phthalocyanine-mediated PDT with the parameters used in this experiment results in significant but temporary functional and morphologic alterations in the ciliary bodies of albino rabbits.

An unusual case of elastofibroma oculi

A 22-year-old female college student from the southwestern United States was first seen with progressive fluffy white growths over both corneas nasally and a history of chronic allergies and extensive sun, wind, and chlorine exposure as a competitive swimmer. The lesions were superficial, elevated, crescent-shaped, vascularized, and extended from the limbal conjunctiva onto the peripheral cornea nasally. The lesions were composed of an unencapsulated thick fibrovascular pannus with numerous fibrocytes, chronic inflammatory cells and mast cells, and abundant linear and wavy elastinophilic profiles, but no adipose tissue. Ultrastructurally, the elastinophilic structures were immature elastic fibers arranged in globules and bundles within a thick collagenous matrix. No mature elastic fibers were found. A few areas of elastotic degeneration were also found. This lesion resembled elastofibromas that have been reported more commonly in the subcapsular region and only once in the ocular region. Previous reports debated whether the elastic material in elastofibromas is derived from excessive production of elastic fibers by activated fibrocytes or from elastotic degeneration of collagen. In our case, both processes occur and are presumed to result from excessive ultraviolet radiation, wind and chlorine exposure, and perhaps, chronic inflammation; features that have been ascribed to the pathogenesis of pingueculae and pterygia.

The role of prostaglandins E2 and F2 alpha in ultraviolet radiation-induced cortical cataracts in vivo

PURPOSE

Previous work has shown that exposure of lens epithelial cells or rabbit eyes in vivo to ultraviolet B (UVB) radiation enhanced prostaglandin (PG)E2 synthesis. Such enhanced PGE2 synthesis was related to the increased DNA synthesis that followed UVB exposure. The current study examined the relationship between enhanced prostaglandin synthesis and UVB-induced cataract formation.

METHODS

Seventy albino (New Zealand white) rabbit eyes were exposed to UVB radiation in vivo. Fluence of radiation at the cornea was 2.8 J/cm2, 5.6 J/cm2, or 11.2 J/cm2. Eyes were examined 24 hours after UVB exposure and for as long as 10 days by slit lamp biomicroscopy. Mass spectrometry was used to measure PGE2, PGF2 alpha, and 6-keto-PGF1 alpha content of the lens and iris-ciliary body using authentic standards. To determine the effect of inhibition of prostaglandin synthesis on UVB-induced cataract formation, animals were given indomethacin intraperitoneally. Other pharmacologic agents, such as PGE2, PGF2 alpha, and misoprostol, were applied topically to the eye. The effect of UVB on K+ pump was determined by incubating isolated lenses with [86Rb+].

RESULTS

Twenty-four hours after UVB exposure, PGE2 and PGF2 alpha concentrations in aqueous humor were increased by 100- and 30-fold, respectively. Lens PGE2 and PGF2 alpha increased by 6- and 4-fold, respectively, after UVB radiation exposure. Pretreatment of animals with indomethacin prevented the rise in lens and aqueous humor PGE2 and PGF2 alpha levels. Furthermore, indomethacin was partially protective against UVB cataract formation and lowered cataract severity from stage 3 to stage 1, but it did not prevent UVB-induced lens changes completely. Topical application of PGE2 before UVB exposure completely prevented cataract formation in the UVB-exposed eye. In contrast, topical administration of PGF2 alpha increased cataract severity. UVB-induced cataract formation preceded changes in [86Rb]+ uptake in lenses subsequently incubated in K(+)-free Tyrode's.

CONCLUSIONS

Enhanced synthesis of cyclooxygenase products of arachidonic acid metabolism in the lens is associated with UVB-induced cataract formation in albino rabbit eyes, and inhibition of cyclooxygenase by indomethacin decreased the severity of cataracts. PGE2, the principal arachidonic acid metabolite, appears to have a protective role because pretreatment of the eye with topical PGE2 completely prevented UVB-induced cataract formation, whereas PGF2 alpha increased the severity of the cataract. The evidence presented for a role of PGF2 alpha in the development of cataract suggests that caution be exercised in the use of PGF2 alpha derivatives in the therapy of glaucoma.

Microwave cyclodestruction: evaluation on human eyes

AIMS

The study was set up to evaluate the effect of microwave cyclodestruction on human eyes.

METHODS

Two human eyes were studied. For treatment a horn shaped 5.8 GHz microwave applicator and fibre optic thermometry were used. Just before enucleation, the rectangular (2 x 3 mm) microwave aperture was placed onto the conjunctiva at a position 1-2 mm posterior to the corneal scleral limbus. Each of three to four treatment spots was targeted to receive a thermal dose of 54 degrees C for 1 minute. Clinical, gross, and histopathological evaluations were performed.

RESULTS

Clinical evaluations of the treatment sites (immediately after microwave application) revealed no evidence of conjunctival or scleral damage. Trace fluorescein 2% uptake was noted within the targeted zones. The first eye was sectioned along the equatorial axis. Examination of the ciliary body and pars plana revealed whitening of the ciliary processes and depigmentation. Histopathological evaluations revealed ciliary epithelial necrosis with pigment dispersion. The vascularity of the ciliary processes showed focal disruption and haemorrhage. The underlying ciliary muscle and sclera appeared to be unaffected. No other findings could be attributed to microwave cyclodestruction.

CONCLUSION

The results of this phase I toxicity study suggest that microwave heating can be used to damage preferentially the epithelial layers of the human ciliary body.

[Effects of low-intensity laser irradiation on several parameters of microcirculation in the bulbar conjunctiva of patients with scleroderma]

Computer-aided analytical system of TV images (CASTI) of the anterior segment of the eye revealed an appreciable increase of the level of aggregation gradient in arterioles and venules of the bulbar conjunctiva of 37 children suffering from various forms of scleroderma, as against 18 healthy children. Exposure to low-energy laser of a close infrared band (approximately 890 nm) had a favorable impact on blood aggregation in patients with scleroderma. CASTI of the anterior segment of the eye proved to be an objective and highly informative method for the diagnosis and monitoring of the efficacy of various treatment modalities.

Another look at pterygium surgery with postoperative beta radiation

Although complications associated with the use of beta radiation after pterygium surgery can occur, the author has found the use of beta radiation to be beneficial in preventing recurrences when used with pterygium surgery. An effective surgical regime of pterygium surgery is presented. A procedure made up of steps that tend to prevent revascularization of the operative site after pterygium surgery will decrease the recurrence rate. The use of strontium 90 and the mechanism of action of beta ray therapy in treatment of the pterygium is discussed. Few complications have occurred in > 200 surgically treated cases of pterygium with postoperative beta radiation administered with a strontium 90 applicator. No cases of radiation cataract have been observed.

A model for pterygium formation

The formation of a pterygium is modelled using a population balance model of corneal and limbal epithelial production. Scattered light incident at the temporal limbus is focused at the nasal limbus with a peak intensity > or = 20 times. We hypothesize that this causes a focal alteration of corneal epithelial stem cells (which play a role in maintaining a barrier between corneal and conjunctival epithelia). Normative rabbit corneal data were used. Light-induced conjunctival epithelial proliferation was implemented by amplifying normal epithelial cell production along a nasal sector of the limbal circumference. A ten-fold normal peak in stimulation was assumed at the nasal zero azimuth (3 o'clock position in the right eye) with a quadratic attenuation to zero stimulation (normal) at the circumferential limits. Adjacent points on the outer limbus were assumed to be independent generators of epithelial cells that migrated in centripetal streams into the cornea. Normalization of the attrition rate for a net surface accumulation of the proliferating cells was embedded into the computational algorithm. The localized conjunctival mass was allowed to travel the predicted distance along the surface before the final shape was computed. The result shows a wing-shaped mass with a curved leading edge (corneal side). It is proposed that the initial biologic event in pterygium pathogenesis is an alteration of limbal stem cells due to chronic ultraviolet light exposure. The concomitant breakdown of the limbal barrier and subsequent conjunctivalization of the cornea explain the shape and formation of a primary pterygium.

Photodamage of the conjunctiva in patients with porphyria cutanea tarda

Ninety two patients with porphyria cutanea tarda (PCT) were examined ophthalmically in a paired case control study. The incidence of pinguecula and of pterygium was 8 and 2 times higher respectively, in PCT patients than in the control group. The photodamage to the conjunctiva is considered to be a result of the photoactivity of uroporphyrin in the tissues.

The effect of varying wavelength on subconjunctival scleral laser suture lysis in rabbits

We studied laser suture lysis of subconjunctival scleral sutures in a rabbit eye using selected wavelengths from a dye and diode laser to determine which wavelength caused the least conjunctival damage. We found an oval shaped area of coagulation necrosis surrounding the suture track in the conjunctival substantia propria measuring in depth 61.0 mu for 488 + 514 nm (blue-green), 105.7 mu for 514 nm (green), 148.3 mu for 630 nm (red), and 29.0 mu with 780 + 830 nm (infrared) wavelengths. No observable damage was noted with 585 nm (yellow) or 610 nm (orange) wavelengths. The energy intensity required for suture lysis was similar across each wavelength studied. No damage was observed in the sclera or conjunctival epithelium. These findings suggest that using the yellow or orange wavelength, when performing laser suture lysis clinically, potentially may limit conjunctival damage.

The radioprotective effects of WR-2721 on radiation-induced goblet cell loss

We assessed the efficacy of the radioprotective effects of WR-2721 in radiation-induced goblet cell loss. Fourteen female New Zealand white rabbits were divided into radioprotected, radiounprotected, and control groups. Ten rabbits received 5,000 rad of beta irradiation to the temporal conjunctiva of both eyes. The right eyes were pretreated with topical applications of WR-2721 30 minutes and 1 minute before irradiation. The left eyes received irradiation only. Four additional rabbits received neither irradiation nor pretreatment with WR-2721. After a 2-month waiting period, each animal was killed and goblet cell densities per high-power field (GCD/HPF) were determined over the areas in question and compared using paired sample t tests. The mean GCD/HPF for the radioprotected, unprotected, and control groups were 10.93, 4.68, 23.15 (right eye), and 26.25 (left eye). Paired sample t tests showed a significant radioprotective effect when comparing WR-2721-treated animals with those receiving radiation only (p less than 0.003). Independent sample t tests showed significant goblet cell loss in both the radioprotected (p less than 0.018) and radiounprotected eyes (p less than 0) when compared with control groups. These data suggest a radioprotective effect of WR-2721 in radiation-induced goblet cell loss.

[The conjunctival lymphatic bed of the rabbit in exposure to ultraviolet radiation]

Morphofunctional state of the lymphatic bed of the conjunctiva has been studied under effect of ultraviolet radiation. A comparative characteristics of development of the clinical picture and morphological criteria of the harmful effect of the ultraviolet radiation is presented. When all clinical symptoms disappear, there is no complete restoration of the capacitance function of the lymphatic vessels and intracellular regeneration of ultra-microscopical structures of endotheliocytes.

Transscleral microwave cyclodestruction

A 4.6-gigahertz (GHz) microwave applicator was used to ablate the ciliary body in rabbit eyes. High-frequency electromagnetic radiation provides a favorable dose distribution to induce local heating of the ciliary body. For treatment, a 3-mm diameter disc-shaped applicator was placed on the conjunctiva and over the ciliary body. Conjunctival temperatures were monitored during treatment with a built-in thermocouple thermometer located at the center of the disc-shaped antenna. This allowed direct measurement (dosimetry) of the conjunctival temperature during treatment. Using this microwave-based heat-delivery system, doses in a range of 60 degrees for 30 or 60 seconds appeared to cause ciliary body damage with relative sparing of the conjunctiva and sclera.

[State of the organ of vision and behavior of rats after action on the eye of increased doses of UV-irradiation]

Male Wistar rats, weighing on the average 200 g, were used to investigate the clinical picture of photokerato-conjunctivitis and behavioral responses to the open field test after exposing their eyes to UV-radiation with an emission maximum at 302 nm. The development threshold for conjunctivitis was 0.6 kJ/m2 and that for keratitis was 0.8 kJ/m2. The corneal lesions such as perforation and formation of persistent (up to 60 days) changes emerged beginning with the dose 3 kJ/m2 (in 50% of animals). This dose is a minimally acting dose in terms of behavior. At the dose of 10 kJ/m2 the decrease of the horizontal motor activity, which was significant from day 14, became irreversible. Thus when the organ of vision is exposed to UV-radiation, it is important to take into consideration not only structural changes but also potential functional disorders, which are associated with enhancement of inhibitory processes in the CNS.

Infectious bovine keratoconjunctivitis: seasonal variation in cultural, biochemical and immunoreactive properties of Moraxella bovis isolated from the eyes of cattle

The eyes of 20 young cattle were examined over an 18 month period in which 12 members of the group contracted infectious bovine keratoconjunctivitis (IBK). On each of 23 occasions cultural, biochemical and immunoreactive properties of up to 6 isolates of Moraxella bovis derived from each eye were determined. Relationships between the clinical response of eyes, phenotypic properties of M. bovis and annual variations in the level of solar ultraviolet radiation of 280 to 320 nm wavelength were examined. M. bovis was isolated from all IBK-affected and some unaffected eyes less than one month after the maximum annual level of the mean weekly UV radiation (2,840 mWh.m-2 X nm-1) was recorded. A high proportion of M. bovis from IBK lesions were simultaneously active in haemolysis, agar corrosion, gelatin liquefaction and litmus milk peptonisation. Some of these characteristics showed marked dissociation despite consistent reactivity in the fluorescent antibody test, which had a sensitivity and specificity of 95%. Fall in the mean weekly level of UV radiation below 1,438 mWh X m-2 X nm-1 in autumn was accompanied by healing of ulcers, persistent scar formation and a decline in the number of M. bovis isolated from affected eyes. A slower decline in the number of M. bovis isolated from apparently healthy eyes occurred in the winter and occasional fresh IBK lesions occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Solar radiation and the eye: a review of knowledge relevant to eye care

Solar radiation has been implicated, with a variety of evidence, as a causative agent in photokeratoconjunctivitis, pinguecula and pterygium, nodular band keratopathies, epidermoid carcinoma, cataract, solar retinopathy, and macular degeneration. Much of the support for claims relating to chronic conditions having serious consequences and significant prevalence in the United States rests on investigations using animals and short-time exposures at high intensities. The direct applicability of these studies to humans in natural environments is uncertain, but they have been relied on because one cannot deliberately induce significant trauma in humans. The use of animal data is made difficult by the need to convert animal thresholds to human equivalents, to equate laboratory cycles and magnitudes of exposure to those in the natural environment, and to quantify the impact of avoidance and protective mechanisms. Risk can be assessed adequately only by epidemiological studies, but their potential has been only partially realized because of poorly controlled confounding variables. Epidemiologic evidence suggests that corneal trauma from ultraviolet radiation (UVR) is a risk of prolonged exposure in regions containing much ultraviolet (UV) or in highly reflective environments. The impact of UV-B on cataractogenesis has been investigated inadequately and no evidence exists for retinal trauma arising from routine exposure in even the brightest surroundings. However, there can be no question that enough solar energy reaches the earth to harm the eye if unattenuated. Damage to vision as a result of direct solar viewing demonstrates that unequivocally. The lack of clear evidence of radiation damage occurring other than in regions of high reflectivity and/or low horizons suggests that in normal surroundings there is little or no risk to the eye, although more careful epidemiological investigation is required before all concern can be ruled out completely. The major improvement required is the quantification of individual exposure histories. This step is necessary if we are to make significant progress toward better understanding the practical impact of solar radiation on the eye.

The effects of ionizing radiation on the dividing cells of the conjunctival epithelium

The influence of an X-ray dose of 10 Gy (1000 rads) on mitosis in the rat conjunctival epithelium was assessed. A mitotic inhibition began 1 hour postirradiation and continued for 4 days. The mitotic index was depressed to 10% of control values. After 5 days postirradiation, the mitotic index surpassed the control values peaking at 7 days postirradiation. The spindle axes of cells in telophase of the perilimbal rat conjunctival epithelium assume a characteristic, three dimensional orientation relative to the limbus. Ionizing radiation did not disrupt this organization at any time postirradiation. In fact, the frequency of mitotic figures preferentially aligned in irradiated tissue was enhanced during the mitotic rebound.

Alterations to eye structures in hairless mice by long-term ultraviolet irradiation. A histopathological study

The eyes of 75 Hr/Hr hairless mice were irradiated with one minimal erythema dose/day of UV light for a period of 12 months, and then observed for a further 6 months. The mice were divide into 3 subgroups, - one without protectans, - one protected by the sun protection lotion Sea and Ski, factor 5, - and one by Piz Buin, Factor 6. The eyes of 75 non-irradiated mice of the same type, subdivided into 3 comparable groups, served as controls. Animals which died during the test period were examined immediately. After the 18 months period, eyes and adnexa of the surviving animals were examined macroscopically and by light microscopy. The lifespan of unprotected, irradiated mice was significantly shorter than the protected groups. The eyelids of irradiated mice presented hyperplasia, actinic keratosis and invasive carcinoma, the latter in 20%. No melanotic tumours were recorded. Since the sun lotion protected animals had a significantly longer lifespan they showed a higher number of palpebral tumours. No irradiation lesions could be demonstrated in the lens, the vitreous or the retina.

Biological effect of ultraviolet radiation on cattle: bovine ocular squamous cell carcinoma

The relationship between bovine ocular squamous cell carcinoma and ultraviolet radiation was studied. Experimental procedures were devised to irradiate cattle with predetermined quantities of ultraviolet beta. Irradiation induced a preneoplastic ocular growth in one of four irradiated cattle. An epizootiologic study indicates that since 1950 the occurrence of bovine ocular squamous cel carcinoma reported at slaughter has increased. This increase was real and not due to an increase in numbers of cattle.

The use of strontium-90 in the treatment of carcinoma in situ of the conjunctiva

Four patients with carcinoma in situ were treated with strontium-90 beta ray application. The dose used was 4,500 rads after surgical removal or with small recurrent tumor and 7,000 rads for primary treatment. All patients were disease-free at follow-up periods of 48 to 320 months after treatment. One patient required superficial x-ray treatment for recurrent disease. No serious complications developed with the treatment and no progressive cataracts have occurred.

Keratitis in reindeer. Relation to the presence of 1st instar larvae of the nostril fly (Cephenomyia trompe L) in the conjunctival sac and to natural ultraviolet radiation

The significance of the presence of 1st instar larvae of the reindeer nostril fly (Cephenomyia trompe L) in the conjunctival sac of reindeer was investigated. The influences of natural ultraviolet radiation upon the development of inflammatory reactions of the eyes was also studied. It is stated that both 1st instar larvae of the Cephenomyia fly, when deposited on the eye, and natural ultraviolet radiation may act as predisposing or enhancing factors in the etiology of keratitis in reindeer. In certain cases keratitis may develop when both parameters are present.