Antarctica eye study: a prospective study of the effects of overwintering on ocular parameters and visual function

BACKGROUND

In 2013 five polar explorers attempted to complete the first Trans-Antarctic Winter Traverse (TAWT). This study presents the ophthalmological findings for this group, who overwintered in Antarctica as part of the White Mars Human Science Protocol. Antarctic crews are exposed to extreme cold, chronic hypoxia and altered day-night cycles. Previous studies of Antarctic explorers have focused on the prolonged effect of ultraviolet radiation including the development of ultraviolet keratitis and accelerated cataract formation. This is the first study of its kind to investigate the effect of overwintering in Antarctica on the human eye.

METHODS

Pre and post-expedition clinical observations were made including visual acuity, contrast sensitivity, colour vision, auto-refraction, subjective refraction, retinal examination, retinal autofluoresence and retinal thickness, which were graded for comparison. During the expedition additional observations were made on a monthly basis including LogMAR visual acuity, autorefraction and intraocular pressure.

RESULTS

No significant differences between pre and post-expedition observations were found, including visual acuity, contrast sensitivity, colour vision, refraction, visual fields, intraocular pressure and retinal examination. There was a small but statistically significant decrease in retinal thickness across all regions of the retina, except for the macular and fovea, in all explorers. Intra-expedition observations remained within normal limits.

CONCLUSION

Reassuringly, the human eye remains largely unchanged by exposure to the extreme conditions encountered during the Antarctic winter, however, further research is needed to investigate changes in retinal thickness. This may have implications for scientists who spend prolonged periods of time in the polar regions, as well as those who have prolonged exposure to the extreme cold or chronic hypoxia in other settings.

Cyclodestructive procedures for non-refractory glaucoma

BACKGROUND

Glaucoma is a leading cause of blindness worldwide. It results in a progressive loss of peripheral vision and, in late stages, loss of central vision leading to blindness. Early treatment of glaucoma aims to prevent or delay vision loss. Elevated intraocular pressure (IOP) is the main causal modifiable risk factor for glaucoma. Aqueous outflow obstruction is the main cause of IOP elevation, which can be mitigated either by increasing outflow or reducing aqueous humor production. Cyclodestructive procedures use various methods to target and destroy the ciliary body epithelium, the site of aqueous humor production, thereby lowering IOP. The most common approach is laser cyclophotocoagulation.

OBJECTIVES

To assess the effectiveness and safety of cyclodestructive procedures for the management of non-refractory glaucoma (i.e. glaucoma in an eye that has not undergone incisional glaucoma surgery). We also aimed to compare the effect of different routes of administration, laser delivery instruments, and parameters of cyclophotocoagulation with respect to IOP control, visual acuity, pain control, and adverse events.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2017, Issue 8); Ovid MEDLINE; Embase.com; LILACS; the metaRegister of Controlled Trials (mRCT) and ClinicalTrials.gov. The date of the search was 7 August 2017. We also searched the reference lists of reports from included studies.

SELECTION CRITERIA

We included randomized controlled trials of participants who had undergone cyclodestruction as a primary treatment for glaucoma. We included only head-to-head trials that had compared cyclophotocoagulation to other procedural interventions, or compared cyclophotocoagulation using different types of lasers, delivery methods, parameters, or a combination of these factors.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened search results, assessed risks of bias, extracted data, and graded the certainty of the evidence in accordance with Cochrane standards.

MAIN RESULTS

We included one trial (92 eyes of 92 participants) that evaluated the efficacy of diode transscleral cyclophotocoagulation (TSCPC) as primary surgical therapy. We identified no other eligible ongoing or completed trial. The included trial compared low-energy versus high-energy TSCPC in eyes with primary open-angle glaucoma. The trial was conducted in Ghana and had a mean follow-up period of 13.2 months post-treatment. In this trial, low-energy TSCPC was defined as 45.0 J delivered, high-energy as 65.5 J delivered; it is worth noting that other trials have defined high- and low-energy TSCPC differently. We assessed this trial to have had low risk of selection bias and reporting bias, unclear risk of performance bias, and high risk of detection bias and attrition bias. Trial authors excluded 13 participants with missing follow-up data; the analyses therefore included 40 (85%) of 47 participants in the low-energy group and 39 (87%) of 45 participants in the high-energy group.Control of IOP, defined as a decrease in IOP by 20% from baseline value, was achieved in 47% of eyes, at similar rates in the low-energy group and the high-energy groups; the small study size creates uncertainty about the significance of the difference, if any, between energy settings (risk ratio (RR) 1.03, 95% confidence interval (CI) 0.64 to 1.65; 79 participants; low-certainty evidence). The difference in effect between energy settings based on mean decrease in IOP, if any exists, also was uncertain (mean difference (MD) -0.50 mmHg, 95% CI -5.79 to 4.79; 79 participants; low-certainty evidence).Decreased vision was defined as the proportion of participants with a decrease of 2 or more lines on the Snellen chart or one or more categories of visual acuity when unable to read the eye chart. Twenty-three percent of eyes had a decrease in vision. The size of any difference between the low-energy group and the high-energy group was uncertain (RR 1.22, 95% CI 0.54 to 2.76; 79 participants; low-certainty evidence). Data were not available for mean visual acuity and proportion of participants with vision change defined as greater than 1 line on the Snellen chart.The difference in the mean number of glaucoma medications used after cyclophotocoagulation was similar when comparing treatment groups (MD 0.10, 95% CI -0.43 to 0.63; 79 participants; moderate-certainty evidence). Twenty percent of eyes were retreated; the estimated effect of energy settings on the need for retreatment was inconclusive (RR 0.76, 95% CI 0.31 to 1.84; 79 participants; low-certainty evidence). No data for visual field, cost effectiveness, or quality-of-life outcomes were reported by the trial investigators.Adverse events were reported for the total study population, rather than by treatment group. The trial authors stated that most participants reported mild to moderate pain after the procedure, and many had transient conjunctival burns (percentages not reported). Severe iritis occurred in two eyes and hyphema occurred in three eyes. No instances of hypotony or phthisis bulbi were reported. The only adverse outcome that was reported by the treatment group was atonic pupil (RR 0.89 in the low-energy group, 95% CI 0.47 to 1.68; 92 participants; low-certainty evidence).

AUTHORS' CONCLUSIONS

There is insufficient evidence to evaluate the relative effectiveness and safety of cyclodestructive procedures for the primary procedural management of non-refractory glaucoma. Results from the one included trial did not compare cyclophotocoagulation to other procedural interventions and yielded uncertainty about any difference in outcomes when comparing low-energy versus high-energy diode TSCPC. Overall, the effect of laser treatment on IOP control was modest and the number of eyes experiencing vision loss was limited. More research is needed specific to the management of non-refractory glaucoma.

Impact of laser pulse duration on the reduction of intraocular pressure during selective laser trabeculoplasty

PURPOSE

To evaluate the efficacy of selective laser trabeculoplasty (SLT) to lower intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG), normal tension glaucoma (NTG) or ocular hypertension (OHT), when performed with laser pulse duration of 1 ns compared with standard 3-5 ns.

METHODS

Bilateral SLT with a 532 nm Q-switched neodymium-doped yttrium aluminium garnet laser was conducted in 30 patients (60 eyes) with POAG (n = 5), NTG (n = 2) or OHT (n = 23). Pulse duration was 1 ns in the right eye (30 eyes; cases) and 3-5 ns in all left eyes (controls). Main outcome measures were IOP at 1 h, 1 day, 8 weeks and 6 months, and the rate of adverse ocular tissue reactions in all eyes.

RESULTS

Mean 1 ns and 3-5 ns SLT IOPs were 24.1 and 24.3 mmHg, respectively, at baseline. No statistically significant difference in mean 1 ns and 3-5 ns SLT IOP was observed at 1 h (P = 0.761), 1 day (P = 0.758), 8 weeks (P = 0.352) and 6 months postoperatively (P = 0.879). No significant difference in postoperative anterior chamber inflammation was observed between the eyes (P = 0.529). Treatment with both laser pulse durations resulted in minor ultrastructural changes in the drainage angle.

CONCLUSIONS

SLT performed with a 1 ns laser pulse duration does not appear to be inferior to SLT performed with the standard 3-5 ns duration at lowering IOP in treatment-naïve patients with POAG, NTG or OHT.

A laser-induced mouse model with long-term intraocular pressure elevation

Purpose

To develop and characterize a mouse model with intraocular pressure (IOP) elevation after laser photocoagulation on the trabecular meshwork (TM), which may serve as a model to investigate the potential of stem cell-based therapies for glaucoma.

Methods

IOP was measured in 281 adult C57BL/6 mice to determine normal IOP range. IOP elevation was induced unilaterally in 50 adult mice, by targeting the TM through the limbus with a 532-nm diode laser. IOP was measured up to 24 weeks post-treatment. The optic nerve damage was detected by electroretinography and assessed by semiautomatic counting of optic nerve axons. Effects of laser treatment on the TM were evaluated by histology, immunofluorescence staining, optical coherence tomography (OCT) and transmission electron microscopy (TEM).

Results

The average IOP of C57BL/6 mice was 14.5±2.6 mmHg (Mean ±SD). After laser treatment, IOP averaged above 20 mmHg throughout the follow-up period of 24 weeks. At 24 weeks, 57% of treated eyes had elevated IOP with the mean IOP of 22.5±2.5 mmHg (Mean ±SED). The difference of average axon count (59.0%) between laser treated and untreated eyes was statistically significant. Photopic negative response (PhNR) by electroretinography was significantly decreased. CD45+ inflammatory cells invaded the TM within 1 week. The expression of SPARC was increased in the TM from 1 to 12 weeks. Histology showed the anterior chamber angle open after laser treatment. OCT indicated that most of the eyes with laser treatment had no synechia in the anterior chamber angles. TEM demonstrated disorganized and compacted extracellular matrix in the TM.

Conclusions

An experimental murine ocular hypertension model with an open angle and optic nerve axon loss was produced with laser photocoagulation, which could be used to investigate stem cell-based therapies for restoration of the outflow pathway integrity for ocular hypertension or glaucoma.

Rod-like microglia are restricted to eyes with laser-induced ocular hypertension but absent from the microglial changes in the contralateral untreated eye

In the mouse model of unilateral laser-induced ocular hypertension (OHT) the microglia in both the treated and the normotensive untreated contralateral eye have morphological signs of activation and up-regulation of MHC-II expression in comparison with naïve. In the brain, rod-like microglia align to less-injured neurons in an effort to limit damage. We investigate whether: i) microglial activation is secondary to laser injury or to a higher IOP and; ii) the presence of rod-like microglia is related to OHT. Three groups of mice were used: age-matched control (naïve, n=15); and two lasered: limbal (OHT, n=15); and non-draining portion of the sclera (scleral, n=3). In the lasered animals, treated eyes as well as contralateral eyes were analysed. Retinal whole-mounts were immunostained with antibodies against, Iba-1, NF-200, MHC-II, CD86, CD68 and Ym1. In the scleral group (normal ocular pressure) no microglial signs of activation were found. Similarly to naïve eyes, OHT-eyes and their contralateral eyes had ramified microglia in the nerve-fibre layer related to the blood vessel. However, only eyes with OHT had rod-like microglia that aligned end-to-end, coupling to form trains of multiple cells running parallel to axons in the retinal surface. Rod-like microglia were CD68+ and were related to retinal ganglion cells (RGCs) showing signs of degeneration (NF-200+RGCs). Although MHC-II expression was up-regulated in the microglia of the NFL both in OHT-eyes and their contralateral eyes, no expression of CD86 and Ym1 was detected in ramified or in rod-like microglia. After 15 days of unilateral lasering of the limbal and the non-draining portion of the sclera, activated microglia was restricted to OHT-eyes and their contralateral eyes. However, rod-like microglia were restricted to eyes with OHT and degenerated NF-200+RGCs and were absent from their contralateral eyes. Thus, rod-like microglia seem be related to the neurodegeneration associated with HTO.

Glaucoma alters the circadian timing system

Glaucoma is a widespread ocular disease and major cause of blindness characterized by progressive, irreversible damage of the optic nerve. Although the degenerative loss of retinal ganglion cells (RGC) and visual deficits associated with glaucoma have been extensively studied, we hypothesize that glaucoma will also lead to alteration of the circadian timing system. Circadian and non-visual responses to light are mediated by a specialized subset of melanopsin expressing RGCs that provide photic input to mammalian endogenous clock in the suprachiasmatic nucleus (SCN). In order to explore the molecular, anatomical and functional consequences of glaucoma we used a rodent model of chronic ocular hypertension, a primary causal factor of the pathology. Quantitative analysis of retinal projections using sensitive anterograde tracing demonstrates a significant reduction (approximately 50-70%) of RGC axon terminals in all visual and non-visual structures and notably in the SCN. The capacity of glaucomatous rats to entrain to light was challenged by exposure to successive shifts of the light dark (LD) cycle associated with step-wise decreases in light intensity. Although glaucomatous rats are able to entrain their locomotor activity to the LD cycle at all light levels, they require more time to re-adjust to a shifted LD cycle and show significantly greater variability in activity onsets in comparison with normal rats. Quantitative PCR reveals the novel finding that melanopsin as well as rod and cone opsin mRNAs are significantly reduced in glaucomatous retinas. Our findings demonstrate that glaucoma impacts on all these aspects of the circadian timing system. In light of these results, the classical view of glaucoma as pathology unique to the visual system should be extended to include anatomical and functional alterations of the circadian timing system.

[The neuroanatomical and physiological bases of variations in intraocular pressure]

Intraocular pressure displays a distinct circadian rhythm in animals and humans, with an increase at night and a decrease during the daytime. In animals, the IOP rhythm has been reported to be synchronized by environmental light and to persist in constant darkness, demonstrating a circadian component controlled by an endogenous pacemaker. The structures involved in the rhythmic regulation of intraocular pressure include the suprachiasmatic nucleus, which controls the activity of sympathetic and parasympathetic ocular innervation. These effectors are responsible for controlling the production (beta-adrenergic system) and the outflow (alpha1-adrenergic, parasympathetic system, prostaglandin) of aqueous humor. The production of aqueous humor is under adrenergic control (alpha1- and beta-receptors). Many neuropeptides such as vasoactive intestinal peptide, substance P, and the atrial natriuretic peptide are also involved in the regulation of intraocular pressure. A better understanding of the circadian regulation of intraocular pressure is needed for an appropriate treatment of ocular hypertension and glaucoma.

Müller cell response to laser-induced increase in intraocular pressure in rats

The goal of this study was to investigate the reaction of the Müller cells to elevated intraocular pressure (IOP). Elevated IOP is one of the risk factors in glaucomatous retinal ganglion cell (RGC) degeneration. Müller cells play an important role in retinal homeostasis. The reaction of Müller cells was examined by evaluating temporal changes in glutamate aspartate transporter (GLAST), glutamine synthase (GS), glial fibrillary acidic protein (GFAP), and the B-cell lymphoma (Bcl-2) using immunoblotting and immunohistochemical techniques. After IOP was elevated for 4-60 days, there was a time-related decrease in RGC ranging from 6% to 44%. There was also a time-related increase in GLAST protein reaching maximum after 3 weeks of elevated IOP. On the other hand, there was very little change in the expression of GS during the first 2 weeks followed by some increase between 21 and 60 days. An increase in Bcl-2 was biphasic with maximum increase after 4 days followed by decline after 15 and 21 days. GFAP, which is usually not expressed in normal Müller cells, was present at all time points. In all cases, the increase was most intense in the vicinity of the ganglion cells where the astrocytes and endfeet of the Müller cells are located. These results indicate that Müller cells react to the insult of elevated IOP by expressing GFAP and Bcl-2, proteins that are expressed in reactive gliosis and other pathological conditions. The increase in GLAST along with minimum change in GS indicates a disturbance in glutamate homeostasis.

One-Year Follow-Up of Selective Laser Trabeculoplasty in Open-Angle Glaucoma

BACKGROUND

Selective laser trabeculoplasty (SLT) targets the pigmented trabecular meshwork (TM) cells without damage to the adjacent non-pigmented tissue. A study was conducted to evaluate the efficacy and safety of SLT in the treatment of uncontrolled open-angle glaucoma.

METHODS

In a prospective non-randomized study 44 eyes of 31 patients with uncontrolled open-angle glaucoma were treated with a frequency-doubled, Q-switched Nd:YAG laser. A total of approximately 50 spots were placed over 180 degrees of the TM at energy levels ranging from 0.7 to 0.9 mJ. Intraocular pressure (IOP) was measured 1, 2, and 24 h, 1 and 2 weeks and 1, 2, 3, 6, 9, and 12 months after treatment.

RESULTS

The average pre-operative IOP was 25.6 (SD 2.6) mm Hg (range 22-34). The mean IOP reduction from baseline at 24 h, 3, 6 and 12 months was 7.1 mm Hg (SD 3.5) or 27.6%; 4.2 mm Hg (SD 3.5) or 16.4%; 4.7 mm Hg (SD 4.2) or 18.6%, and 4.4 mm Hg (SD 3.8) or 17.1%, respectively. The percent of eyes with IOP reduction of 3 mm Hg or more at 3, 6 and 12 months was 66, 78 and 62%. A pressure spike of 8 mm Hg or more was detected in 4 eyes (9.1%). Anterior chamber reaction was seen 1 h after SLT and was mild to moderate in 16 eyes (40.4%) and marked in 3 eyes (6.8%).

CONCLUSIONS

SLT has shown reasonable efficacy in lowering IOP over 1-year follow-up, but there was a tendency for IOP to increase with a longer follow-up. Long-term follow-up studies with a large sample size are needed to determine whether the IOP lowering effect is sustained over time, and to assess the efficacy of repeated SLT.

Custom-designed plaque radiotherapy for nonresectable iris melanoma in 38 patients: tumor control and ocular complications

PURPOSE

To evaluate plaque radiotherapy for iris melanoma.

DESIGN

Prospective noncomparative interventional case series.

METHODS

For 38 patients, custom-designed plaque radiotherapy using iodine 125 isotope was applied overlying the cornea with a tumor apex dose of 80 Gy. The main outcome measures were tumor control and ocular complications using Kaplan-Meier estimates and Cox proportional hazards regression analysis.

RESULTS

In all cases, the melanoma was nonresectable owing to large or discohesive tumor. The tumor configuration was nodular in 24 cases (63%) and flat (diffuse) in 14 (37%). The mean tumor basal diameter was 9 mm (range 4 to 13 mm). Solid tumor extended into the anterior chamber angle in 36 eyes (95%). Tumor seeds were noted on the iris stroma for a mean of 7 clock hours and in the anterior chamber angle for a mean of 4 clock hours. Five-year follow up revealed tumor metastasis in 0% and tumor recurrence in 8% of patients. Visual acuity of 20/200 or worse was found in 16% at 5 years. Radiation-related complications at 5 years included corneal epitheliopathy (9%), cataract (70%), and neovascular glaucoma (8%). No patients developed corneal necrosis, scleral necrosis, retinopathy, or papillopathy. After treatment, the combined incidence of tumor-related and radiation-related elevated intraocular pressure at 5 years was 33%. Enucleation was necessary in 13% at 5 years, for tumor recurrence (n = 3) and patient preference (n = 1).

CONCLUSIONS

Plaque radiotherapy is a useful alternative to enucleation for eyes with nonresectable iris melanoma. Tumor control is 92% at 5 years, but related complications, especially cataract and elevated intraocular pressure, should be anticipated.

[Retrobulbar irradiation for Graves' ophthalmopathy -- long-term results]

BACKGROUND

Significance of retrobulbar irradiation in patients suffering form Graves' ophthalmopathy, though established since almost one century, is subject of scientific debate. The present study investigated the effect of retrobulbar irradiation using a standardized protocol focussing on long term results.

PATIENTS AND METHODS

Between 1981 and 1997, 104 patients treated by retrobulbar irradiation (10 to 20 Gray) due to Graves' disease. Twenty-nine of these underwent irradiation as sole treatment (mean follow-up 57 months), while in the remaining 75, it was combined with a systemic steroid treatment (mean follow-up 40 months). Patients were evaluated regarding proptosis, intraocular pressure, lid signs, motility as well as subjective assessment of double vision and retrobulbar pain.

RESULTS

While proptosis remained unchanged, lid signs, chemosis and intraocular pressure showed slight and statistically significant improvement. However, these findings were considered to be clinically insignificant. Retrobulbar pain was improved in 75 % of patients. 25 % of patients showed improved motility, 75 % remained stable, and in none of them was there a deterioration of ductions. Results proved stable even in long-term follow-up. 25 % per cent of patients underwent a surgical procedure one year after radiotherapy.

CONCLUSIONS

In our series, we could not demonstrate an additional benefit of systemic steroids when combined with retrobulbar irradiation. Up to sixteen years after treatment, no treatment-related adverse reaction was seen. We found a remarkable improvement in ocular motility. This holds even more true in comparison to the natural course of the condition. Retrobulbar irradiation seems to shorten the duration of the disease, thus allowing earlier performance of eventual rehabilitative surgery.

Developing laser-induced glaucoma in rabbits

PURPOSE

An animal mode of glaucoma is necessary for the study of its pathogenesis and treatment. The purpose of this study was to create open-angle glaucoma using a laser in rabbits.

METHODS

The trabecular meshwork of anaesthetized, adult, pigmented and albino rabbits was ablated internally using a diode laser via a gonioscopy lens, or externally through the limbus. In albino rabbits we used Chinese ink to pigment the angle and methylcellulose to open the iridocorneal angle. The eyes were examined weekly and histological assessment was performed.

RESULTS

The success rate of intra-ocular hypertension was low (15%) and a result of synechial angle closure. A narrow angle prevented access of the laser beam to the trabecular meshwork and promoted damage to the ciliary processes located on the posterior iris.

CONCLUSIONS

Due to the unique anatomy of the rabbit eye, laser-induced glaucoma is difficult to achieve. To create a successful model it is necessary to widen the iridocorneal angle, selectively damage the trabecular meshwork and reduce inflammation.

[Successful irradiation of ciliary processes with electrons in therapy refractory aphakic glaucoma]

BACKGROUND

Successful radiation was already reported by Genée and Weitzel (1968): Electrons from a Betatron were used for irradiation of the ciliary epithelium to lower aqueous humor secretion. To our knowledge, no other paper on this topic has been published so far.

PATIENT

A 26-year-old man had history of concussion trauma and cataract surgery in childhood. In adult age, cataract surgery and retinal operations were followed by numerous surgical procedures and maximal medical treatment because of a secondary glaucoma. The patient refused further surgical and medical treatment with the exception of the administered systemic carbo-anhydrase inhibitor. Because of severe side-effects caused by the acetozolamide, irradiation of the ciliary processes with electrons, emitted from a linear accelerator, was performed. The total amount of 12 Gy both on the nasal and on the temporal side of the ciliary body was fractionated in several sessions.

RESULTS

During a follow-up of 22 months without medication, the mean value of i.o. pressure was 22.1 mm Hg. The patient is doing well, corrected VA is 0.8.

CONCLUSION

Irradiation of the ciliary processes with electrons for lowering aqueous humor secretion was effective in an otherwise non treatable case of glaucoma.

Enhanced prostaglandin synthesis after ultraviolet-B exposure modulates DNA synthesis of lens epithelial cells and lowers intraocular pressure in vivo

PURPOSE

To study the functional significance of prostaglandin synthesis after ultraviolet-B (UVB) exposure of cultured human lens epithelial cells and rabbit eyes in vivo.

METHODS

Prostaglandin E2 (PGE2) was assayed using a radioimmunoassay (RIA) and mass spectroscopy. An immortalized human lens epithelial cell line (HLE-B3) was exposed to UV irradiation, and the synthesis of PGE2 was compared with the rabbit lens epithelial cell line N/N1003A. Intact human lenses were exposed to UVB in organ culture. [3H]Thymidine incorporation was measured in cultured lens epithelial cells by incubation with the radiolabel. The effects of isobutyl methyl xanthine (IBMX), an inhibitor of phosphodiesterase and of dibutyryl cyclic adenosine monophosphate (cAMP), an analog of cAMP, on PGE2 synthesis and DNA synthesis, were determined. Rabbit eyes were exposed to UVB radiation in vivo. Intraocular pressure was measured at specific times after exposure. Aqueous humor was remove from rabbit eyes, and its PGE2 content was measured by RIA.

RESULTS

Cultured human lens epithelial cells (HLE), like rabbit lens epithelial cells (RLE), showed a dose-dependent increase in basal PGE2 synthesis 24 hours after UVB exposure. However, the amount of PGE2 synthesis was 2000-fold higher in the rabbit cells. Ultraviolet-B radiation enhanced the incorporation of [3H]thymidine in lens epithelial cells. Pretreatment of cells with indomethacin reduce PGE2 synthesis and [3H]thymidine incorporation. The human and rabbit cells responded in a similar manner to changes in DNA synthesis after UVB exposure. The addition of IBMX or dbcAMP to indomethacin-treated, UVB-exposed cells restored DNA synthesis toward the levels observed in the UVB-exposed cells. An increase in the concentration of cAMP was observed in lens epithelial cells exposed to exogenous PGE2. PGE2 synthesis in intact human lenses also increased twofold 24 hours after UVB exposure. Exposure of the rabbit eye in vivo to an optimal dose of UVB produced an increase in the PGE2 levels of the lens and the aqueous humor. Measurements of the intraocular pressure (IOP) of the animals showed a decrease in IOP by 2.21 +/- 0.66 and 6.45 +/- 0.79 mm Hg (mean +/- SEM, P = 0.004, t-test) at 6 and 24 hours after UVB exposure, respectively. The decrease in IOP was prevented by pretreatment with indomethacin. Exposure of the rabbit lens to UVB radiation in vivo enhanced [3H]thymidine incorporation twofold into the lens. Pretreatment of rabbits with indomethacin before exposure reduced this response.

CONCLUSIONS

Results indicate that UVB exposure enhances PGE2 synthesis in HLE cultures as well as in rabbit lenses irradiated in vivo. This increased PGE2 synthesis is related to the increase in DNA synthesis observed after UVB treatment. The modulation of DNA synthesis in cultured lens epithelial cells after UVB exposure may be mediated by a cAMP-dependent mechanism.

[Histopathological study on the pars plicata of cynomolgus monkey by the CW Nd:YAG laser]

The pars plicata of cynomolgus monkey eyes were coagulated by a continuous wave (CW) Nd:YAG laser contact system. the intraocular pressure and histopathological changes were observed during the following 3 months. the intraocular pressure decreased during the first week to a minimum level and returned gradually to the pre-coagulation level within 1-3 months. Immediately after photocoagulation, both pigment and non-pigmented epithelium of pars plicata were destroyed. Three weeks after the coagulation nonpigmented epithelium and capillaries showed regeneration. Three months after coagulation, the proliferation of non-pigmented epithelium was conspicuous and regenerating pigment epithelium was observed around the merging of the burned lesion. The CW-Nd:YAG laser contact photocoagulation induced localized destruction of ciliary processes. The regeneration of epithelium and capillaries might indicate that the function of ciliary body could recover to a certain extent and it may be comparatively easy to control the degree of coagulation. These findings suggest that it might be possible to apply CW-Nd:YAG laser photocoagulation to various types of glaucoma.

[Effects of argon laser irradiation of the iris on the concentration of aqueous prostaglandins and cyclic AMP]

In order to elucidate the influence of acute ocular inflammation on the aqueous humor dynamics and intraocular pressure (IOP), we carried out argon laser photo-coagulations on the rabbit irises and determined the concentrations of aqueous humor prostaglandins (PGs), cyclic AMP and protein. The IOP changed in a biphasic manner, i.e. initial hypertension and later hypotension. The concentrations of aqueous humor PG E2, PG F2 alpha and protein increased markedly after laser irradiation and then decreased gradually, although the concentrations of PG E2 and protein remained significantly higher than the baseline values at 24 hours after the irradiations. The concentrations of aqueous cyclic AMP of the irradiated eyes and control eyes were 67.8 pmol/ml and 29.3 pmol/ml, respectively. We presumed that the increase in concentration of aqueous cyclic AMP and breakdown of the blood-aqueous barrier by PGs caused the reactive hypotension.

Use of beta radiation to control I.O.P

The use of ophthalmic applicator containing Strontium-90 beta ray was used to bring about a change in I.O.P. by its effect on the ciliary body. The change in I.O.P. depends on the degree of damage done to the ciliary body. The study showed that the change in I.O.P. was directly proportional to the intensity of beta rays application - higher the dose of beta radiation more was the damage and more the reduction in I.O.P.

Microwave cyclodestruction for glaucoma in a rabbit model

Microwave thermotherapy was used to treat experimentally induced glaucoma. Microwave-induced cyclodestruction was successful in reducing intraocular pressure in all treated glaucomatous eyes for 4 weeks. Two additional glaucomatous eyes were left untreated to serve as controls, and were noted to have persistently elevated intraocular pressures. Six additional eyes were then subjected to an equivalent treatment (50 degrees C in five 1-minute applications), which resulted in approximately 180 degrees of heat treatment just posterior to the corneoscleral limbus. These specimens were evaluated with light microscopy at baseline, 24 hours, and 7 days after treatment. Our clinical and histopathologic evaluations suggested that microwave thermotherapy (delivered under thermometry control) allowed for chorioretinal/ciliary body destruction that resulted in reductions of intraocular pressure in glaucomatous eyes.

A new contact neodymium:YAG laser for cyclophotocoagulation

A newly developed compact (40 kg), self-contained contact Neodymium:YAG laser produces high-peak, high-energy (800 mJ/pulse), short (1.0 millisecond) pulses with 1 to 3 pulses/exposure. Energy is delivered via a 320-microns cleaved quartz fiber optic probe. Cyclophotocoagulation was performed in five eyes of three medium-sized Dutch-pigmented rabbits. The eyes received exposures of 1 to 3 pulses/exposure. Energy delivered ranged from 100 to 800 mJ/pulse. Histopathology revealed ciliary body disruption and hemorrhage with no damage to overlying sclera. When used for transscleral cyclodiathermy in the rabbit, the laser created significant ciliary body disruption with minimal scleral injury.

Quantitative CW Nd:YAG pars plana transscleral photocoagulation in postmortem eyes

The effect of different types of burns and numbers of lesions on, and the role of initial pressure head in, the rate of aqueous outflow was studied in enucleated human and porcine eyes. Noncontact and contact CW Nd:YAG laser applied to human eyes 3 mm posterior to the limbus produced a 34% and 51% increase, respectively, in outflow as compared with controls (P = .01). In porcine eyes, outflow increased directly with the number of noncontact burns as well as with the amount of perfusion pressure. Our results suggest that intraocular pressure and outflow are functions of both the intensity of irradiation and the surface area treated, and that each individual pressure head may require an optimal pars plana area of treatment of therapeutic degree to lower pressure and yet prevent overfiltration and phthisis. Our results also suggest that there may be a passive transneuroepithelial and transscleral outflow component in clinical laser cycloablation and, therefore, a need to grade laser treatments in order to prevent visual loss through unnecessary injury.

Biphasic intraocular pressure response to Q-switched Nd:YAG laser irradiation of the iris and the apparent mediatory role of prostaglandins

In rabbits, laser irradiation of the iris causes an immediate rise in intraocular pressure (IOP), with a concomitant increase of prostaglandins (PGs) in the aqueous humor. We studied IOP responses to Q-switched Nd:YAG laser application to the iris in unanesthetized rabbits, and found that a prolonged IOP reduction lasting for 6-24 hr invariably followed the transient IOP rise of 0.5-2 hr duration. The magnitude of both the IOP rise and reduction was dependent on the level of laser energy. A masked, randomized study revealed that the intraperitoneal administration of indomethacin (50 mg kg-1) prior to laser application significantly reduced the ocular hypertensive and hypotensive responses to laser irradiation (energy: 24 mJ). The maximum IOP rise from baseline was 5.4 +/- 3.0 mmHg (n = 10) with the intraperitoneal vehicle and 1.5 +/- 4.2 mmHg (n = 10) with intraperitoneal indomethacin administration. Thus, the difference was statistically significant (P less than 0.025, Student's t-test). The maximum IOP reduction from baseline was -8.5 +/- 2.6 mmHg (n = 10) with the intraperitoneal vehicle and -4.0 +/- 2.4 mmHg (n = 10) with intraperitoneal indomethacin (P less than 0.001, Student's t-test). The concentration of PGE2 in the aqueous humor, as determined by radioimmunoassay on samples obtained at 2 and 4 hr after laser application, was found to be significantly increased in rabbits that received the vehicle solution but not in animals that were pretreated with intraperitoneal injection of indomethacin. This suggests that this PG or other cyclooxygenase products are involved with mediation of the initial IOP increase and the prolonged decrease in IOP that follows laser irradiation of the iris.

Apraclonidine effects on ocular responses to YAG laser irradiation to the rabbit iris

Apraclonidine (p-aminoclonidine) ophthalmic solution effectively reduces the rise in intraocular pressure (IOP) following anterior segment laser surgery. We tested the effect of topical 0.5% apraclonidine on intraocular pressure and on protein and prostaglandin (PG) E2 concentrations in aqueous humor following Q-switched Nd:YAG laser irradiation to the iris of albino rabbits, at an energy level of 2 to 200 mJ. IOP was measured prior to and for 24 hr after irradiation. Aqueous humor was withdrawn before and 1 hr after laser irradiation for determining protein (Lowry method) and PGE2 (radioimmunoassay). Four to seven rabbits were used for each experiment. The increase in IOP and protein concentration following laser irradiation was demonstrated to be dependent on the amount of laser energy. Apraclonidine completely abolished the IOP rise, and significantly reduced the elevation of protein content. Apraclonidine failed to affect the increase in PGE2.

[Krypton laser coagulation in idiopathic macular holes]

Twenty-six eyes with acute idiopathic senile macular holes and visual acuity of between 0.02 and 0.5 were treated by laser coagulation with krypton red. The laser burns were placed in a ring around the hole, at the border of the retinal detachment. A few weeks after treatment marked regression of the detachment was seen. During the follow-up period (3-18 months) visual acuity improved in 18 eyes, deteriorated in 1 and was unchanged in 7.

Clinical, structural and molecular phototherapy effects of laser irradiation on the trabecular meshwork of human glaucomatous eyes

The effects of argon laser trabeculoplasty (LTP) on intraocular pressure (IOP), outflow facility, the morphology of the trabecular meshwork (TM), and the pattern of extracellular glycoprotein fibronectin in trabeculum were studied in 46 eyes of patients with primary open-angle glaucoma (POAG). The LTP was done with informed consent, anticipating that trabeculectomy would be carried out at a scheduled time (2 h to several months following laser therapy). We found that the magnitude of IOP reduction and the improvement in the facility of outflow achieved are directly dependent on the time course after LTP and laser-induced structural changes in trabecular tissue. Light microscopic and immunohistochemical evaluations of the TM specimens at earlier intervals after LTP revealed evidence of heat effects, with disruption and shrinkage of the TM collagenous components and accumulation of fibronectin deposits in the aqueous drainage channels as compared with the TMs of matched patients with POAG who did not receive laser treatment. Within 24 h after LTP, proteins of glaucomatous TMs excised from patients incorporated increased amounts of [3H]-leucine radioactive label; however, the amount of [3H]-leucine-labeled material was significantly depressed in later periods of evaluation. The specimens obtained at longer intervals after LTP showed partial or total occlusion of the intertrabecular spaces by extracellular debris; however, the amount of trabecular fibronectin was not significantly different from that measured 24 h after LTP. At least two potential mechanisms are proposed for the TM tissue response to laser treatment, including heat-induced stretching of the collagen in lamellae and fibronectin-mediated attachment of beams supporting an adhesive tightening of the trabecular components caused by LTP. The changes in laser-induced tissue responses appear to be the result of morphological repair of irradiation-injured trabecular tissue.

The effect of topical dexamethasone and preoperative beta irradiation on a model of glaucoma fistulizing surgery in the rabbit

We studied the effect of topical dexamethasone (1%) and preoperative beta irradiation on a model of glaucoma fistulizing surgery in the rabbit. Intraocular pressure and gross facility of aqueous outflow following surgery were not influenced by either treatment, although blebs persisted longer in the irradiated eyes. Steroids reduced clinically observable inflammation as well as the number of inflammatory cells identifiable by microscopy. Fibroblast production temporarily slowed, and ultra-structural examination demonstrated lipid-filled vacuoles and dilated mitochondria in these eyes. Also, the scar was thinner at 24 days. Beta irradiation delayed wound healing and the scar was thinner in the early postoperative stages, but the light microscopic appearance of the scar was unaltered at 59 days. Inflammation was more pronounced initially, with abundant fibrin in the wound. Recovery of the conjunctival epithelium was delayed. The delay in fibroblast recruitment and wound contraction, the thinner scar tissue, and the increased survival of the bleb are all factors that suggest that beta irradiation may be a useful adjunct to glaucoma surgery.

Platelet-activating factor and laser trauma of the iris

Local application of platelet-activating factor (PAF) on the rabbit eye caused a dose-dependent significant increase in intraocular pressure (IOP). After laser irradiation of the iris the IOP showed a hypertensive phase of about 3 hr. Prophylactic treatment with the PAF antagonist BN 52021 but not with indomethacin abolished the hypertensive phase. Elevated levels of protein (10.6 +/- 0.9 g/l) and prostaglandin E2 (PGE2, 1.7 +/- 0.2 ng/ml) were measured in the aqueous humor 2 hr after laser irradiation of the iris. Prophylactic treatment with BN 52021 showed lower levels of protein (6.1 +/- 0.7) and PGE2 (1.1 +/- 0.02); with indomethacin pretreatment the level of protein was 3.4 +/- 0.7 g/l and of PGE2 0.10 +/- 0.02 ng/ml. A role of PAF as a mediator in ocular inflammatory response is suggested.

A comparison of CW Nd:YAG contact transscleral cyclophotocoagulation with cyclocryopexy

The cyclodestructive and inflammatory effects of CW Nd:YAG contact laser were compared to those of conventional cryopexy. CW Nd:YAG light transmitted by fiber optic cable and sapphire crystal was applied transsclerally to the ciliary body of pigmented and albino rabbits. Cyclocryopexy was given to a comparable second group. The intraocular pressure (IOP), flare, iritis, cells and conjunctival hyperemia were monitored clinically up to 3 weeks. The breakdown of the blood-aqueous barrier and time course of ocular inflammation was similar for both modalities and IOP was -12.2 +/- 4.2 mm Hg for laser cyclopexy and -15.1 +/- 5.4 mm Hg for cyclocryopexy at 3 weeks. Ciliary body lesions were noted in both groups. Overall, albino rabbits showed less histological damage and faster recovery of IOP. Contact cyclophotocoagulation and cyclocryopexy can be considered models of ocular injury. The similarities in ocular irritative response suggest a similar pathophysiologic mechanism underlying the pressure behavior in both thermal mode injuries.

The effect of therapeutic ultrasound on the average of multiple intraocular pressures throughout the day in therapy-resistant glaucoma

The effect of therapeutic ultrasound was evaluated in 17 patients with therapy-resistant glaucoma by comparing average intraocular pressure (IOP) curves measured before and 3-4 months after insonification. The insonification regimen was standardized; the medication was identical during both pressure curve measurements. The average IOP decrease was 44% +/- 24 SD (range, 73% decrease to 6% increase). In 82% of the patients the IOP decrease was more than 34%. There was no correlation between the percentage of IOP decrease and the average IOP before insonification (correlation coefficient, 0.21; P = 0.41).

Effect of melatonin on intraocular pressure

We studied the effect of orally administered melatonin on intraocular pressure in humans. We suppressed serum melatonin levels by exposing our subjects to bright light. Our experiments suggest that melatonin lowers intraocular pressure in man. This may prove to be a therapeutically useful agent since melatonin appears to be relatively free of side effects and is effective in small quantities.

A controlled five-year follow-up study of laser trabeculoplasty as primary therapy for open-angle glaucoma

We followed up 32 eyes of 32 patients with early glaucoma (22 with capsular glaucoma and ten with simple glaucoma) who received laser trabeculoplasty as a primary therapy. These eyes were compared with a matched control group of 32 eyes treated with medication initially. The success rate (intraocular pressure below 22 mm Hg with laser alone or medication alone) at five years was 50% (16 of 32 eyes) in the laser-treated group and 22% (seven of 32 eyes) in the control group (P less than .02). The control group required more modifications of their therapy to control intraocular pressure. The neuroretinal rim area in the control eyes decreased 2.5 times as much as in the laser group (P = .017). Changes in the Friedmann visual fields did not differ significantly between the two groups.

Factors affecting the results of argon laser trabeculoplasty in open-angle glaucoma

Argon laser trabeculoplasty (ALT) was performed in 232 eyes of 180 patients affected by uncontrolled primary open-angle glaucoma (POAG), exfoliation syndrome glaucoma (ESG) or pigment dispersion syndrome glaucoma (PDSG). Mean follow-up was 9 months (3-22). Mean IOP change was -21.6% (+/- 19) from the initial value. The effect of IOP was larger in patients with ESG, PDSG, and in POAG cases with more pigmented trabecular meshwork. No relationship was found between IOP changes and age or refraction of patients; the association with iridoplasty did not influence final results. An Octopus computerized perimeter was used for pre and post-treatment visual field tests. In 113 eyes Octopus exams met the requirements for quantitative analysis. In this group 17% of visual field improved, 64% remained stable and 19% worsened. A good functional response was more frequent among the eyes with less advanced disease.

Treatment of glaucoma with high-intensity focused ultrasound

This report is a summary of results for 170 eyes of patients with refractory glaucoma treated with high-intensity focused ultrasound. The results are analyzed in terms of the effectiveness of various treatment regimens, complications, and classifications of the patient population according to such factors as age and etiology. The mean pretreatment intraocular pressure (IOP) for the ensemble of patients treated with optimal intensity levels was 38.6 mmHg. Whereas only 10% of these patients had an IOP of 25 mmHg or less prior to treatment, 90% had an IOP of 25 mmHg or less within 3 months of treatment. At 1 year after a single treatment, 65% of patients still maintained intraocular pressures of 25 mmHg or less, and 56% had pressures of 22 mmHg or less. The effectiveness of retreatment of failed or unresponsive cases was also investigated and found to have a degree of success comparable to that of initial treatments.

Q-switched neodymium: YAG laser surgery of the vitreous

Fifty-nine eyes underwent vitreous surgery (vitreolysis) with the Q-switched Nd: YAG laser. This was used to cut vitreoretinal bands and membranes in 16 eyes and to clear persistent vitreous opacities in 25 eyes. The use of appropriate specialized contact lenses and modification of the standard slit-lamp delivery system were essential for vitreous YAG laser surgery. Successful results occurred in eyes where the target tissues were located at distances greater than 2 mm from the crystalline lens and the retina. Vision was improved in 18 eyes, unchanged in 40 eyes, and worse in 1. Complications included focal opacities of the crystalline lens in 5 eyes, retinal holes with detachment in 1 eye, and minor retinal hemorrhages in 4. Methods of preventing complications are discussed.

The effect of argon laser trabeculoplasty on the rate of filtering surgery

We examined the impact of argon laser trabeculoplasty (ALT) on the overall rate of filtering surgery on a resident service. From 1981 through 1984, 121 eyes underwent ALT for treatment of uncontrolled primary open-angle glaucoma despite maximum tolerated medical therapy. Mean intraocular pressure decreased from 27 +/- 4 mmHg to 20 +/- 5 mmHg (median follow-up, 9 months). From 1978 through 1981, the mean annual rate of filtering surgery was 16. Only one filtering procedure was performed in 1982, the first full year of ALT use. However, 15 filtering procedures were performed in 1983 and 18 were performed in 1984. Despite a large number of apparently effective ALT treatments and despite an overall reduction in outpatient visits of 20%, the rate of filtering surgery has returned to the pre-ALT level. This suggests that ALT may be effective in delaying the need for surgery, but in many cases it probably does not prevent surgery.

Timolol and intra-ocular pressure elevation following neodymium: YAG laser surgery

The intra-ocular pressure in 76 patients, undergoing Neodymium: YAG laser surgery was measured just before treatment, and one and two hours afterwards. The fellow eye served as a control. Serious elevation of the intra-ocular pressure was demonstrated, especially in capsulotomy in the aphakic eye, to a lesser extent in pseudophakic eyes. Intra-ocular pressure elevation of more than 20 mm was seen in iridectomies. Timolol 1/2% eyedrops given before Neodymium: YAG laser treatment minimized the elevation of the intra-ocular pressure. Prolonged follow-up of the intra-ocular pressure is recommended.

Laser iridectomy. A controlled study comparing argon and neodymium: YAG

Laser peripheral iridectomies were performed on both eyes of 38 patients with acute or chronic primary angle-closure glaucoma or with narrow angles capable of closure. The right eye was treated with the neodymium YAG laser (Nd:YAG) and the left eye with the argon laser. Patients were followed for a minimum of eight months. The mean number of applications to produce iris penetration was six with the Nd:YAG laser and 73 with the argon laser. Visual acuity, postoperative intraocular pressure (IOP), corneal changes, and pigment dispersion were similar in the two groups. Microhyphema was more prevalent in the Nd:YAG iridectomy group. Pupillary distortion, iritis, and late failure of patency were more frequent in the argon laser group. Nd:YAG laser iridectomies require fewer applications and produce less inflammation. This controlled study demonstrates that when properly and carefully performed, the Nd:YAG laser is at least as effective and appears to be as safe as the argon laser for performing peripheral iridectomies.

Use of the YAG laser with a seven-micron spot in pseudophakic eyes

We report on 216 cases of posterior capsulotomy performed with a LASAG Microruptor II YAG laser in patients with posterior chamber intraocular lenses. In 108 cases, the YAG laser was used in multimode with a 70-micron spot and 3.5 mJ to 5.0 mJ of energy; in the other 108 cases, the laser was used in fundamental mode with a 7-micron spot and 0.7 mJ to 1.2 mJ of energy. In the first group, IOL damage was seen in 10.2% of cases, uveitis developed in 0.4% of patients, and transient eye pressure elevation was noted in 6.5% of patients. In the second group, neither IOL damage nor uveitis occurred, and only two cases (1.8%) developed transient pressure elevation.

Secondary surgical and neodymium-YAG laser discissions

Between November 1978 and June 1984, 161 surgical and 102 neodymium-YAG laser discissions were performed. The incidence of discission in patients with a mean three-year follow-up after extracapsular surgery was 22.1% (39 of 176 eyes) after extracapsular cataract extraction alone and 14.5% (81 of 558 eyes) after extracapsular cataract extraction with intraocular lens implantation (P less than .02); the incidence was 25.5% (47 of 184 eyes) with the transiridectomy clip lens and 9.1% (33 of 364 eyes) with the posterior chamber lens (P less than .001). The average interval between cataract surgery and the discission was 2.4 years. The intraocular pressure was increased in 51% (48 eyes) of the eyes two to five hours after YAG laser discission and was unpredictable in most patients. After surgical discission, the intraocular pressure was increased on the first postoperative day in 13% (18 eyes) of the eyes. With surgical discission, significant complications included vitreous manipulation, wound leak, and intraocular inflammation. Intraocular lens pitting occurred in 20 patients undergoing YAG laser discission. Complications with both procedures included cystoid macular edema, retinal detachment, glaucoma, and closure of a previously adequate discission opening.

Complications associated with the use of the neodymium:YAG laser

The neodymium:YAG laser was used in a consecutive series of 93 eyes. Diagnosis was opacified posterior capsule in 81 eyes of which 52 were pseudophakic, with cystoid macular edema and vitreous strands in eight eyes, pigmented anterior hyaloid in two eyes, opacified anterior capsular flap in one eye and vitreous strand blocking an anterior chamber tube shunt to an encircling band tube in one eye. Despite significant visual improvement and reduction of cystoid macular edema, a variety of complications were seen. These included pitting of the implant in 26 eyes and cracks in four, two of which developed a vitreitis. These occurred more frequently in our earlier cases. Also seen was elevated IOP in six eyes, pupillary block in two, vitreous face rupture in five, cystoid macular edema in four, hyphemas in four, corneal injury in two and acute peripheral retinal hemorrhage in one eye.