Comparative Single Vesicle Analysis of Aqueous Humor Extracellular Vesicles before and after Radiation in Uveal Melanoma Eyes.

Small extracellular vesicles (sEVs) have been shown to promote tumorigenesis, treatment resistance, and metastasis in multiple cancer types; however, sEVs in the aqueous humor (AH) of uveal melanoma (UM) patients have never previously been profiled. In this study, we used single particle analysis to characterize sEV subpopulations in the AH of UM patients by quantifying their size, concentration, and phenotypes based on cell surface markers, specifically the tetraspanin co-expression patterns of CD9, CD63, and CD81. sEVs were analyzed from paired pre- and post-treatment (brachytherapy, a form of radiation) AH samples collected from 19 UM patients. In post-brachytherapy samples, two subpopulations, CD63/81+ and CD9/63/81+ sEVs, were significantly increased. These trends existed even when stratified by tumor location and GEP class 1 and class 2 (albeit not significant for GEP class 2). In this initial report of single vesicle profiling of sEVs in the AH of UM patients, we demonstrated that sEVs can be detected in the AH. We further identified two subpopulations that were increased post-brachytherapy, which may suggest radiation-induced release of these particles, potentially from tumor cells. Further study of the cargo carried by these sEV subpopulations may uncover important biomarkers and insights into tumorigenesis for UM.

Green Light-Triggered Intraocular Drug Release for Intravenous Chemotherapy of Retinoblastoma.

Retinoblastoma is one of the most severe ocular diseases, of which current chemotherapy is limited to the repetitive intravitreal injections of chemotherapeutics. Systemic drug administration is a less invasive route; however, it is also less efficient for ocular drug delivery because of the existence of blood-retinal barrier and systemic side effects. Here, a photoresponsive drug release system is reported, which is self-assembled from photocleavable trigonal small molecules, to achieve light-triggered intraocular drug accumulation. After intravenous injection of drug-loaded nanocarriers, green light can trigger the disassembly of the nanocarriers in retinal blood vessels, which leads to intraocular drug release and accumulation to suppress retinoblastoma growth. This proof-of-concept study would advance the development of light-triggered drug release systems for the intravenous treatment of eye diseases.

Ultraviolet A light induces DNA damage and estrogen-DNA adducts in Fuchs endothelial corneal dystrophy causing females to be more affected.

Fuchs endothelial corneal dystrophy (FECD) is a leading cause of corneal endothelial (CE) degeneration resulting in impaired visual acuity. It is a genetically complex and age-related disorder, with higher incidence in females. In this study, we established a nongenetic FECD animal model based on the physiologic outcome of CE susceptibility to oxidative stress by demonstrating that corneal exposure to ultraviolet A (UVA) recapitulates the morphological and molecular changes of FECD. Targeted irradiation of mouse corneas with UVA induced reactive oxygen species (ROS) production in the aqueous humor, and caused greater CE cell loss, including loss of ZO-1 junctional contacts and corneal edema, in female than male mice, characteristic of late-onset FECD. UVA irradiation caused greater mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage in female mice, indicative of the sex-driven differential response of the CE to UVA, thus accounting for more severe phenotype in females. The sex-dependent effect of UVA was driven by the activation of estrogen-metabolizing enzyme CYP1B1 and formation of reactive estrogen metabolites and estrogen-DNA adducts in female but not male mice. Supplementation of N-acetylcysteine (NAC), a scavenger of reactive oxygen species (ROS), diminished the morphological and molecular changes induced by UVA in vivo. This study investigates the molecular mechanisms of environmental factors in FECD pathogenesis and demonstrates a strong link between UVA-induced estrogen metabolism and increased susceptibility of females for FECD development.

Breakdown of the blood-eye barrier in choroidal melanoma after proton beam radiotherapy.

PURPOSE: Irradiation of choroidal melanoma is a safe and globe preserving procedure. Chronic inflammatory processes and ischemia are the main reasons for secondary enucleation in the long run. The aim of this study was to determine whether intraocular inflammation and especially inflammatory response after proton beam therapy (PBT) is related to primary tumor characteristics such as height, tumor volume, and initial flare values. METHODS: Twenty-six patients treated for uveal melanoma using PBT were included. All patients were examined for signs of inflammation using laser flare photometry (LFP). Each examination included assessment of the melanoma and fellow eye (which acted as the control) and imaging of the melanoma. RESULTS: Significant differences of flare values between melanoma eyes and control group were found both at baseline (median 17.65 ph/ms (min 4, max 37.10), 7.45 ph/ms (min 0.80, max 16.40), respectively) and during follow-up (median 21.45 ph/ms (min 4.5, max 70.90); 6.05 ph/ms (min 2.40, max 16.40), respectively) (p < 0.001, Wilcoxon test). Flare values in melanoma eyes increased significantly after PBT (p = 0.005, Wilcoxon test) and after a follow-up of 94 days (median, 7-420 days). Flare values of the control group did not change (p = 0.946, Wilcoxon test). The increase of flare values correlated significantly with maximum tumor height and volume (Spearman-Rho 0.633, p = 0.001 and 0.519, p = 0.007, respectively). CONCLUSION: LFP has proven to show significantly higher flare values in melanoma eyes as compared with the control group and provides data on the course of the inflammatory response after treatment. It may ease treatment planning both at baseline and during follow-up.

Enhancement of vitamin D metabolites in the eye following vitamin D3 supplementation and UV-B irradiation.

PURPOSE: This study was designed to measure vitamin D metabolites in the aqueous and vitreous humor and in tear fluid, and to determine if dietary vitamin D3 supplementation affects these levels. We also determined if the corneal epithelium can synthesize vitamin D following UV-B exposure. METHODS: Rabbits were fed a control or vitamin D3 supplemented diet. Pilocarpine-stimulated tear fluid was collected and aqueous and vitreous humor were drawn from enucleated eyes. Plasma vitamin D was also measured. To test for epithelial vitamin D synthesis, a human corneal limbal epithelial cell line was irradiated with two doses of UV-B (10 and 20 mJ/cm(2)/day for 3 days) and vitamin D was measured in control or 7-dehydrocholesterol treated culture medium. Measurements were made using mass spectroscopy. RESULTS: 25(OH)-vitamin D3 and 24,25(OH)(2)-vitamin D3 increased significantly following D3 supplementation in all samples except vitreous humor. Tear fluid and aqueous humor had small but detectable 1,25(OH)(2)-vitamin D3 levels. Vitamin D2 metabolites were observed in all samples. Vitamin D3 levels were below the detection limit for all samples. Minimal vitamin D3 metabolites were observed in control and UV-B-irradiated epithelial culture medium except following 7-dehydrocholesterol treatment, which resulted in a UV-B-dose dependent increase in vitamin D3, 25(OH)-vitamin D3 and 24,25(OH)(2)-vitamin D3. CONCLUSIONS: There are measurable concentrations of vitamin D metabolites in tear fluid and aqueous and vitreous humor, and oral vitamin D supplementation affects vitamin D metabolite concentrations in the anterior segment of the eye. In addition, the UV exposure results lead us to conclude that corneal epithelial cells are likely capable of synthesizing vitamin D3 metabolites in the presence of 7-dehydrocholesterol following UV-B exposure.

Numerical model of heat transfer in the rabbit eye exposed to 60-GHz millimeter wave radiation.

A numerical model of the anterior chamber of the rabbit eye is presented. The model takes into account both the fluid dynamics of the aqueous humor and the realistic boundary conditions at the interface of the cornea with the environment. The model is used to determine the temperature distribution and velocity field under 60-GHz millimeter wave radiation. The maximum predicted temperature (45.8 (°) C for an incident power density of 475 mW/cm(2)) is in good agreement with experimental results. Moreover, the model shows that there is a value for the incident power density (about 100 mW/cm(2)) for which the direction of aqueous humor flow due to buoyancy is inverted, because of the inversion of the temperature gradient in the anterior chamber of the eye. This phenomenon has already been reported from experimental observations and can be numerically studied, if aqueous humor fluid dynamics are taken into account in the heat-transfer model.

Numerical model of heat transfer in the human eye with consideration of fluid dynamics of the aqueous humour.

In this work we present a new 3D numerical model for heat transfer in the human eye, which takes into account the aqueous humour flow in the anterior chamber. We show that consideration of this phenomenon in the calculations alters the temperature distribution on the corneal and lens surfaces, without, however, noticeably changing their absolute values. The most notable effect is that the coolest area of the cornea moves at a point of 2 mm inferior to its geometric centre. The maximum velocity of the fluid in the anterior chamber was found to be 3.36 × 10(-4) m s(-1). The effect of the flow on displacing the cool area of the corneal surface temperature is counterbalanced by assuming anisotropic thermal conductivity. The model was implemented in the case of an artificial intraocular lens to show the resulting temperature variations.

Prevention of UV-induced damage to the anterior segment using class I UV-absorbing hydrogel contact lenses.

PURPOSE: To determine whether class I ultraviolet (UV) light-blocking contact lenses prevent UV-induced pathologic changes in a rabbit model. METHODS: Twelve rabbits were assigned to 1 of 3 treatment groups (n = 4), as follows: senofilcon A (class I UV blocking) contact lenses; lotrafilcon A contact lenses (no reported UV blocking); no contact lens. The contralateral eye was patched without a contact lens. Animals received UV-B (1.667 J/cm(2)) exposure daily for 5 days. Postmortem tissue was examined as follows: in the cornea, the expression of matrix-metalloproteinases (MMPs) was evaluated by zymography, and apoptosis was evaluated by TUNEL and caspase-3 ELISA; ascorbate in the aqueous humor was evaluated by nuclear magnetic resonance spectroscopy; crystalline lens apoptosis was evaluated by TUNEL and caspase-3 ELISA. RESULTS: Exposed corneas showed a significant increase in MMP-2 and -9, TUNEL-positive cells, and caspase-3 activity in the lotrafilcon A group compared with the senofilcon A group (all P = 0.03). A significant decrease in aqueous humor ascorbate was observed in the exposed lotrafilcon A lens-wearing group compared with the exposed senofilcon A lens-wearing group (P = 0.03). Exposed crystalline lenses had significantly increased caspase-3 activity in the lotrafilcon A group compared with the senofilcon A group (P = 0.03). Increased numbers of TUNEL-positive cells were noted in both the lotrafilcon A and the non-contact lens groups. CONCLUSIONS: The authors show that senofilcon A class I UV-blocking contact lenses are capable of protecting the cornea, aqueous humor, and crystalline lens of rabbits from UV-induced pathologic changes.

Protective effect of 4-coumaric acid from UVB ray damage in the rabbit eye.

UV-induced oxidation damage seems to play a major role in a number of specific pathological conditions of intraocular tissues, such as cataract formation and retinal degeneration. Therefore, antioxidant and/or scavenger compounds might protect the eyes from UV-induced cellular damage. We previously reported that 4-coumaric acid (4-CA) is able to protect rabbit corneal-derived cells (SIRC) from UVB-induced oxidation damage. In this study we evaluated the protective effect of 4-CA against UVB-induced cell damage in rabbit cornea in vivo. Twelve male New Zealand albino rabbits were used; four rabbits were used as a control and received vehicle in one eye and 4-CA acid in the contralateral eye; eight rabbits were exposed to UVB rays (79.2mJ/cm(2)) and three days before to UV exposure each animal received 1 drop/day of vehicle in one eye and 1 drop/day of vehicle containing 4-CA (164ng) in the contralateral eye. Corneal and sclera tissues were removed and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) levels were measured. Superoxide dismutase (SOD) and xanthine oxidase (XO) activities were determined in aqueous humour. UVB-induced vessel hyper-reactivity was strongly reduced at 4 and 24h after UVB exposure after local treatment with 4-CA, 8-oxodGuo levels, a marker of oxidative DNA damage, were significantly increased (P<0.05) in sclera and cornea by UVB irradiation, but when 4-CA was administered to the conjunctiva in a buffered solution once a day for 3d before and 6d after UVB exposure, levels of 8-oxodGuo were similar to controls and significantly reduced (P<0.05) compared to UVB-treated corneas. XO activity in the aqueous humour was significantly increased. The administration of 4-CA for 3d before and 6d after UVB irradiation induced a small but significant (P<0.05) reduction of XO compared with control eyes. Our results indicate that the administration of 4-CA protects eye tissues, thus reducing the harmful effect of UVB radiation at low concentration, probably through its free radical scavenging and antioxidant properties. Therefore, 4-CA may be useful in protecting the eye from free radical damage following UVB exposure from sunlight, UV lamps and welding torches.

Hydrocaffeic and p-coumaric acids, natural phenolic compounds, inhibit UV-B damage in WKD human conjunctival cells in vitro and rabbit eye in vivo.

This paper studied the effect on UV-B ocular damage of 10microM hydrocaffeic acid (HCAF) alone and as a mixture (MIX) (5 microM HCAF+5 microM p-coumaric acid). Since ocular UV-B damage is mediated by reactive oxygen species, the aim was to test if HCAF and MIX could reduce oxidation damage in human conjunctival cells (WKD) in vitro and in cornea and sclera of rabbits in vivo. After UVB irradiation (44 J/m(2)) of WKD cells, 8-oxodG levels in DNA were markedly increased and this effect was attenuated by HCAF and MIX. Rabbit eyes were treated by application of HCAF and MIX drops before UV-B exposure (79 J/m(2)). Corneal and scleral DNA oxidation damage, xanthine-oxidase (XO) activity and malondialdehyde levels (MDA) in corneal tissue and prostaglandin E(2) (PGE(2)) in the aqueous humour were reduced by HCAF alone and in combination with p-coumaric acid, showing their potential as a topical treatment against UV-B damage.

Induction of ultraviolet cataracts in vitro: prevention by pyruvate.

Ultraviolet (UV) radiation is one of the important cataract risk factors. The present studies examined the hypothesis that this effect is due to the UV penetration through the cornea and subsequent induction of a photochemical generation of reactive species of oxygen (ROS) in the aqueous and lens. The hypothesis was ascertained by rat lens organ culture studies conducted under UV (365 nm), with media containing micromolar levels of riboflavin, with and without pyruvate, the latter acting as an ROS scavenger. The implication of ROS in the UV-induced damage was confirmed by measurements of peroxide generation. Damage to the lens was assessed physiologically by measuring the decrease in its active transport of rubidium ions. Biochemically, it was assessed by measuring the lowering of adenosine triphosphate and glutathione. The incorporation of pyruvate in the medium protected the lens against these deleterious effects. That the beneficial effect of pyruvate is attributable to its ROS-scavenging property was proven by the peroxide depletion in its presence, commensurate with its own utilization in parallel. A protective effect of this keto acid against UV-induced tissue damage has been shown for the first time, suggesting its clinical usefulness against UV irradiation-induced pathologies. Hence, further studies on the possible protective effects of such alpha-keto acids against UV damage are in progress.

[Quant therapy and the composition of the moister of the eye anterior chamber (an experimental study)]. / Vliianie kvantovoi terapii na sostav vlagi perednei kamery glaza (eksperimental'noe issledovanie).

We examined 12 rabbits, 6 of whom (12 eyes) were exposed to magneto-infrared laser radiation (MILR) and another 6 (12 eyes) were controls. The parameters of pulse and continuous infrared LED radiation were as follows: wavelength--860 nm, pulse capacity--2 W, mean radiation capacity--10 mW, magnetic field strength--up to 17 mTl. A study of the moister of the anterior chamber showed a MILR-induced activated metabolism, i.e. a better acid-base balance (ABB), more intense oxygenation in the ocular tissues and decreased acidosis. Higher concentrations of buffer bases (ABEe and SBEc) cause shifts in ABB towards metabolic alkalosis. A lower concentration of glucose denotes intensified processes related with its utilization. A lack of changes in the quantity of salts in the moister of the anterior chamber rules out the possibility of that the content of glucose would go down due to its dissolution with a big volume of newly produced moister. A lack of an increase in the concentration of whole protein, as observed after MILR, can be regarded as indirect evidence to absence of any adverse effect on the vascular wall.

Effect of UV-A and UV-B irradiation on the metabolic profile of aqueous humor in rabbits analyzed by 1H NMR spectroscopy.

PURPOSE: This study was conducted to investigate metabolic changes in aqueous humor from rabbit eyes exposed to either UV-A or -B radiation, by using (1)H nuclear magnetic resonance (NMR) spectroscopy and unsupervised pattern recognition METHODS: methods. Both eyes of adult albino rabbits were irradiated with UV-A (366 nm, 0.589 J/cm(2)) or UV-B (312 nm, 1.667 J/cm(2)) radiation for 8 minutes, once a day for 5 days. Three days after the last irradiation, samples of aqueous humor were aspirated, and the metabolic profiles analyzed with (1)H NMR spectroscopy. The metabolic concentrations in the exposed and control materials were statistically analyzed and compared, with multivariate methods and one-way ANOVA. RESULTS: UV-B radiation caused statistically significant alterations of betaine, glucose, ascorbate, valine, isoleucine, and formate in the rabbit aqueous humor. By using principal component analysis, the UV-B-irradiated samples were clearly separated from the UV-A-irradiated samples and the control group. No significant metabolic changes were detected in UV-A-irradiated samples. CONCLUSIONS: This study demonstrates the potential of using unsupervised pattern recognition methods to extract valuable metabolic information from complex (1)H NMR spectra. UV-B irradiation of rabbit eyes led to significant metabolic changes in the aqueous humor detected 3 days after the last exposure.

Interactions between endothelia of the trabecular meshwork and of Schlemm's canal: a new insight into the regulation of aqueous outflow in the eye.

PURPOSE: To test the hypothesis that trabecular meshwork endothelial cells (TMEs) regulate aqueous outflow by actively releasing ligands that upon binding to Schlemm's canal endothelial cells (SCEs) increase transendothelial flow, thereby facilitating the egress of aqueous. METHODS: We tested our hypothesis by (1) activating the TMEs in vitro using a laser procedure known to increase aqueous outflow in vivo; (2) demonstrating that lasered TMEs become activated at the genome-wide level and synthesize ligands; (3) ascertaining that media conditioned by laser-activated TMEs and ligands therein increase transendothelial flow when added to SCEs; and (4) determining that ligands identified as synthesized by TMEs increase permeability when added to SCEs. RESULTS: We find that adding either media conditioned by lasered TMEs or ligands synthesized by TMEs to naïve control SCEs increases permeability. Adding media boiled, diluted, or conditioned by nonlasered TMEs abrogates these permeability effects. Media conditioned by either lasered TMEs or SCEs (TME-cm/SCE-cm), when added to untreated controls of each cell type, induce congruous gene expression and flow effects: TME-cm induces far more differentially expressed genes (829 in control TMEs and 1,120 in control SCEs) than does the SCE-cm (12 in control TMEs and 328 in control SCEs), and TME-cm also increases flow much more (more than 11-fold in control TMEs and more than fourfold in control SCEs) than does the SCE-cm (fivefold in control TMEs and twofold in control SCEs). CONCLUSIONS: As postulated, the TMEs release factors that regulate SCE permeability. Derangement of this TME-driven process may play an important role in the pathogenesis of glaucoma. Ligands identified, which regulate permeability, have potential use for glaucoma therapy.

UV-Absorbing compounds in the aqueous humor from aquatic mammals and various non-mammalian vertebrates.

OBJECTIVE: To evaluate the absorbance of ultraviolet radiation (UVR) in the aqueous humor of various animal species in relation to the ambient radiation of their respective habitats, and to identify substances responsible for this absorbance. Representatives of all five classes (fish, amphibian, reptile, bird, and mammal) have been tested. METHODS: Absorbance was recorded using a spectrophotometer. The ascorbic and uric acid concentrations were determined by HPLC, and the amino acid profiles with an automatic analyzer. Screening for potential UV-absorbing substances was performed by HPLC and a total of 12 species were examined, 7 of them birds. RESULTS: UV-absorbing substances in the aqueous humor were proteins, tryptophan, tyrosine and ascorbic and uric acid. In addition, an unknown UV-absorbing component present in bird aqueous humor caused a high, red-shifted UV-absorbance spectrum, particularly in tentatively heavily exposed species such as goose when migrating at 10,000 m altitude. By comparison, the UV absorbance above the 288-nm wavelength was low in the aqueous humor of fish, frogs, aquatic mammals and two ground-living birds. The crocodile, whose aqueous humor contained significant amounts of both ascorbic and uric acid, revealed a concentration mechanism for ascorbic acid. CONCLUSIONS: The UV absorbance of aqueous humor varies considerably from one species to the next, and independent of class. It is noteworthy that the species being at highest risk for high-dose UV exposure, the migrating goose, showed the most red-shifted spectrum.

Impact of the environment on the mammalian corneal epithelium.

PURPOSE: To evaluate whether the content of ascorbic acid in the corneal epithelium and aqueous humor reflects seasonal fluctuations in parallel with environmental changes. METHODS: Reindeer, cattle, rabbits, and humans were examined, to cover a broad spectrum of overlapping habitats. Ascorbic acid was determined by high-performance liquid chromatography. The thickness of the corneal epithelium was measured, and the number of cells was counted in the tissue sections. RESULTS: Three groups of reindeer eyes were used, two of them collected during summer, the third group during winter. Ascorbate content did not show seasonal variation in either the corneal epithelium or the aqueous humor, whereas epithelial thickness and number of cells decreased significantly from summer to winter. In cattle, ascorbate content, thickness of the epithelium, and number of cells were lower in animals tended indoors compared with those tended outdoors, whereas ascorbate level in the aqueous humor remained similar in both cases. The rabbit showed significantly reduced ascorbate content in the corneal epithelium but not in the aqueous humor in tarsorrhaphy-treated eyes. This procedure did not change epithelial thickness, but the number of cells was slightly increased. The mean epithelial thickness in human corneas successively decreased with increasing latitude and decreasing radiation exposure from the summer season in Oslo to the midnight sun, polar night, conditions in Tromsø, 10 degrees far north, although the differences did not reach statistical significance. CONCLUSIONS: Ambient radiation is needed to sustain high ascorbic acid concentration in the corneal epithelium. Corneal epithelial thickness and number of cells are prone to seasonal fluctuations regulated by ambient radiation. In contrast, ascorbate content of the aqueous humor is uninfluenced by environmental change. It is suggested that seasonal adaptation of mammalian corneal epithelium in response to variation in ambient radiation may be nature's strategy for countering radiation damage to the eye.

Effect of He-Ne laser treatment on the level of lipid peroxidation products in experimental cataract of rabbit eyes.

The effect of low-intensity laser irradiation on the processes of lipid peroxidation in lens homogenate and aqueous humor during experimental diquat-induced cataract of rabbit eyes was studied. The levels of primary and secondary products of lipid peroxidation (LPO), conjugated dienes and thiobarbituric acid reactive substances (TBARS), were evaluated. We found that the experimental cataract model leads to a significant increase in the content of conjugated dienes and in the content of TBARS both in lens homogenate and in aqueous humor. The data obtained support the important role of oxidative stress in the development of the diquat-induced cataract model. Low-intensity laser treatment does not provoke a significant decrease in conjugated dienes or in TBARS in either lens homogenate or aqueous humor. Although our therapeutic scheme led to a slightly decreased level of LPO products, we conclude that the effect of low-intensity laser-irradiation may depend on the dose applied, individual tissues and other factors.

Water soluble antioxidants in mammalian aqueous humor: interaction with UV B and hydrogen peroxide.

HPLC/electrochemical detection was used to identify five major low MW water soluble electrochemically active molecules from the aqueous humor of three species of mammals: New Zealand White rabbits and humans (diurnal) and Sprague-Dawley rats (nocturnal). These molecules are L-cysteine (CYS), L-ascorbic acid (AA), glutathione (GSH), uric acid (UA) and L-tyrosine (TYR); all of these molecules have known antioxidant properties. Nocturnal rat aqueous humor is concentrated in two thiols: GSH (125 microM; n = 24 pooled eyes) and CYS (63 microM), in contradistinction to diurnal species which have high concentrations of AA. No deterioration of any of these antioxidants occurs in a synthetic aqueous humor mixture irradiated with a physiologically relevant spectral UV B dose of 30 mJ/cm2/h (5.5 UV equivalent sunlight hours). The same result occurred with addition of the endogenous aqueous humor UV B photosensitizer L-tryptophan. In a second set of experiments, human synthetic aqueous humor was subjected to hydrogen peroxide induced oxidant stress. The decay of antioxidants was CYS > GSH > AA > UA > TYR. The second highest concentrated antioxidant in human aqueous humor is TYR. Yet TYR failed to protect AA against H2O2-induced free radical damage in a synthetic aqueous humor model system (P = 0.10; ANOVA). The existence of multiple electrochemically active constituents and their thermodynamic interactions must be recognized when choosing animal models to evaluate human aqueous humor antioxidant defense.

Free radical production by Nd:YAG laser photodisruption.

BACKGROUND AND OBJECTIVES: Plasma and cavitation bubble formation during optical breakdown in aqueous media may produce hydroxyl (*OH) radicals. The authors' objectives were to detect *OH produced by a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser photodisruptor and to determine *OH concentration in relation to laser energy. MATERIALS AND METHODS: *OH was assayed by measuring absorbance of triiodide (I3-) in a potassium iodide (KI) solution exposed to optical breakdown by an Nd:YAG laser. The concentration-dependent reduction of radical production in relation to cystamine concentration was evaluated. RESULTS: I3- concentration increased linearly with total irradiation energy and decreased exponentially with increasing cystamine concentration. *OH concentration was calculated using extinction coefficients of I3- and chemical equations relating I3- formation to *OH. CONCLUSIONS: The authors calculated that approximately 4 x 10(-12) moles of *OH are produced in a typical posterior capsulotomy of 100 mJ of total energy. This *OH concentration could produce strand breaks in approximately 0.4% of vitreous hyaluronic acid molecules, but is unlikely to produce clinical effects.

Modulation of the blood-aqueous barrier by light exposure in patients with uveitis.

OBJECTIVE: To evaluate the effect of light deprivation on flare measurements in patients with uveitis. DESIGN: Prospective study. SETTING: Eye clinic providing tertiary ophthalmic care in Calgary. PATIENTS: Five consecutive patients with a history of long-standing uveitis. INTERVENTIONS: Flare measurements were obtained with the Kowa FC-1000 flare-cell meter before and after 24 hours of monocular occlusion, and before and after wearing sunglasses during waking hours in a 24-hour period. OUTCOME MEASURE: Aqueous flare. RESULTS: A significant decrease in flare was observed after 24 hours of occlusion in all patients (p < 0.01). One patient showed an interesting change in response when her steroid treatment was tapered and subsequently stopped. Two of three patients showed a decrease in flare after wearing sunglasses. CONCLUSIONS: These preliminary results suggest that sunlight causes breakdown of the blood-ocular barrier in certain cases of uveitis. Further investigation is needed to determine the extent and mechanisms of light-induced breakdown of the blood-aqueous barrier as well as the role of sunglasses and anti-inflammatory medications as potential modulators of light-induced inflammation.