Glaucoma detection with damato multifixation campimetry online.

PurposeTo evaluate Damato Multifixation Campimetry Online (DMCO), a free-of-charge internet-based visual field test. DMCO exists in three versions: DMCO BASIC, DMCO STANDARD, and DMCO ADVANCED. The main focus was (i) to investigate the sensitivity and the specificity of the existing DMCO versions in the detection of glaucomatous visual field loss and (ii) to define and evaluate algorithms for the interpretation of DMCO results.MethodsThe study design was an evaluation of a diagnostic test and included 97 individuals performing DMCO and white-on-white perimetry. Interpretation algorithms were devised to define abnormality, and these were evaluated using the Glaucoma Staging System as gold standard. Receiver operating characteristic (ROC) curves and area under the ROC (AUC) were calculated.ResultsAUCs from 15 algorithms ranged from 0.79 to 0.90. The most promising algorithm combined results from two successive DMCO STANDARD tests. The sensitivity was highly dependent on the severity of glaucoma. Hence, for eyes with mild, moderate, advanced, and severe glaucoma, the DMCO test demonstrated a sensitivity of 11.8, 71.4, 100, and 100%, respectively. The specificity was as high as 98.1%. Median duration per eye to complete the DMCO STANDARD test was 86 s for the control group and 125 s in participants with glaucoma.ConclusionsDMCO shows promise as a free-of-charge online tool to identify glaucomatous visual field defects in a preselected population. Ongoing studies are evaluating the use of DMCO in a nonselected population.

Photoreceptor Differentiation following Transplantation of Allogeneic Retinal Progenitor Cells to the Dystrophic Rhodopsin Pro347Leu Transgenic Pig.

Purpose. Transplantation of stem, progenitor, or precursor cells has resulted in photoreceptor replacement and evidence of functional efficacy in rodent models of retinal degeneration. Ongoing work has been directed toward the replication of these results in a large animal model, namely, the pig. Methods. Retinal progenitor cells were derived from the neural retina of GFP-transgenic pigs and transplanted to the subretinal space of rhodopsin Pro347Leu-transgenic allorecipients, in the early stage of the degeneration and the absence of immune suppression. Results. Results confirm the survival of allogeneic porcine RPCs without immune suppression in the setting of photoreceptor dystrophy. The expression of multiple photoreceptor markers by grafted cells included the rod outer segment-specific marker ROM-1. Further evidence of photoreceptor differentiation included the presence of numerous photoreceptor rosettes within GFP-positive grafts, indicative of the development of cellular polarity and self-assembly into rudiments of outer retinal tissue. Conclusion. Together, these data support the tolerance of RPCs as allografts and demonstrate the high level of rod photoreceptor development that can be obtained from cultured RPCs following transplantation. Strategies for further progress in this area, together with possible functional implications, are discussed.

The influence of brightness on functional assessment by mferg: a study on scaffolds used in retinal cell transplantation in pigs.

To determine the effect of membrane brightness on multifocal electroretinograms (mfERGs), we implanted poly lactic-co-glycolic acid (PLGA) membranes in the subretinal space of 11 porcine eyes. We compared membranes with their native shiny white color with membranes that were stained with a blue dye (Brilliant Blue). Histological and electrophysiological evaluation of the overlying retina was carried out 6 weeks after implantation. Histologically, both white and blue membranes degraded in a spongiform manner leaving a disrupted outer retina with no preserved photoreceptor segments. Multifocal ERG revealed the white membranes to have a significantly higher P1-amplitude ratio than the blue (P = 0.027), and a correlation between brightness ratio and P1-amplitude ratio was found (r = 0.762). Based on our findings, we conclude that bright subretinal objects can produce normal mfERG amplitude ratios even when the adjacent photoreceptors are missing. Functional assessment with mfERG in scaffold implant studies should therefore be evaluated with care.

Subretinal implantation of electrospun, short nanowire, and smooth poly(ε-caprolactone) scaffolds to the subretinal space of porcine eyes.

Biodegradable scaffolds play an important adjunct role in transplantation of retinal progenitor cells (RPCs) to the subretinal space. Poly(ε-Caprolactone) (PCL) scaffolds with different modifications were subretinally implanted in 28 porcine eyes and evaluated by multifocal electroretinography (mfERG) and histology after 6 weeks of observation. PCL Short Nanowire, PCL Electrospun, and PCL Smooth scaffolds were well tolerated in the subretinal space in pigs and caused no inflammation and limited tissue disruption. PCL Short Nanowire had an average rate of preserved overlying outer retina 17% higher than PCL Electrospun and 25% higher than PCL Smooth. Furthermore, PCL Short Nanowire was found to have the most suitable degree of stiffness for surgical delivery to the subretinal space. The membrane-induced photoreceptor damage could be shown on mfERG, but the reductions in P1 amplitude were only significant for the PCL Smooth. We conclude that of the tested scaffolds, PCL Short Nanowire is the best candidate for subretinal implantation.

Toxicity profiles of subretinal indocyanine green, Brilliant Blue G, and triamcinolone acetonide: a comparative study.

BACKGROUND: This study introduces a novel porcine model to examine the histopathological and electrophysiological consequences of retinotoxicity exerted by dyes commonly used for internal limiting membrane (ILM) staining. METHODS: Indocyanine green (ICG) 0.5 mg/ml, Brilliant Blue G (BBG) 0.25 mg/ml and triamcinolone acetonide (TA) 13 mg/ml was injected subretinally in 12 vitrectomized pig eyes. At 6 weeks, retinas were examined by multifocal electroretinography (mfERG), ophthalmoscopy, fluorescein angiograpy, histopathology, and apoptosis assay. RESULTS: mfERG responses were significantly lower in ICG-injected eyes than in healthy fellow eyes (p = 0.039). The ratio between injected eyes and healthy fellow eyes was lower in the ICG group than in the BBG (p = 0.009) and TA group (p = 0.025). No difference between BBG and TA existed. All retinas were reattached, and fluorescein angiographies showed a window defect corresponding to the injected areas but no blood-retina barrier break-down. Histopathology confirmed damage to the outer retina after ICG, but not after BBG and TA. No apoptosis was found at 6 weeks. CONCLUSIONS: Subretinal ICG induces histological and functional damage to the retina, suggesting that ICG should be used with caution in macular hole surgery, where subretinal migration can occur. In contrast, BBG and TA appear safe after subretinal injection.

Pharmacokinetics of intravitreal glial cell line-derived neurotrophic factor: experimental studies in pigs.

The purpose of this study was to establish the intravitreal (ITV) pharmacokinetics of glial cell line-derived neurotrophic factor (GDNF) and observe possible complications after ITV injection. Twenty Danish landrace pigs and 34 eyes were included in the study; 30 were injected with 100 ng of GDNF, two controls were injected without GDNF, and two received no injection. At post-injection time points of 1, 2, 3, 6 hours (h), 1, 2, 4 or 7 days (d) eyes were enucleated and the ITV concentration of GDNF (cGDNF) was determined by enzyme-linked immunosorbent assay, and activity was tested using a retinal ganglion cell line (RGC5) bioassay. Indirect ophthalmoscopy, intraocular pressure assessment, and fundus photography were performed before enucleation. There was initial variability in the cGDNF, but after 24h GDNF was cleared in a monoexponential fashion with a half-life of 37 h (CL 33-43 h). Therapeutic concentrations were present for 15 d (CL 13-18d) when an extrapolation was done. GDNF-injected vitreous samples stimulated increased survival of RGC5s at 24h post-delivery (p=0.002) compared with no-GDNF vitreous controls. This effect was independent of intraocular incubation time when cGDNF was normalized to 5 ng/ml. A semi-logarithmic dose-response curve showed linearity between 0.1 and 10 ng/ml. None of the eyes showed any signs of inflammation or other complications. A single ITV GDNF injection of 100 ng leads to therapeutic levels for 15 days in the porcine eye. The GDNF was stable in the intraocular environment and no adverse events were observed. GDNF might therefore play a role in the future treatment of acute retinal damage.

[Visual loss under silicone oil]. / Visusminderung unter Silikon.

Silicone oil is used as intravitreal tamponading agent in surgery for rhegmatogenous retinal detachment (RRD) cases complicated with proliferative vitreoretinopathy (PVR). Recently, a number of case series have appeared where profound central visual loss has been found in eyes after uncomplicated vitrectomy with silicone tamponade for RRD in eyes with seemingly good visual potential. Several reports have demonstrated the migration of silicone oil droplets into the retina and the optic nerve, others the widespread loss of myelinated optic nerve fibres. These reports are reviewed, and it is concluded that caution is warranted when silicone oil is used in eyes with good visual potential. Finally the additional danger of central visual loss should be taken into consideration when deciding to use silicone oil or gas as intravitreal tamponade.

Macular morphology and visual acuity after macular hole surgery with or without internal limiting membrane peeling.

AIM: To examine postoperative macular morphology and visual outcome after 12 months in relation to internal limiting membrane (ILM) peeling versus no peeling, indocyanine green (ICG) staining and re-operation in eyes that achieved macular hole closure after surgery. METHODS: Seventy-four eyes with closed stage 2 or 3 macular holes were recruited from a randomised clinical trial comparing: (1) vitrectomy without ILM peeling; (2) vitrectomy with 0.05% isotonic ICG-assisted ILM peeling; and (3) vitrectomy with 0.15% trypan blue-assisted ILM peeling. Contrast-enhanced Stratus optical coherence tomography was used to assess central foveal thickness, central photoreceptor layer thickness (CPRT), central photoreceptor layer discontinuity (PRD) and relative reflectivity of the outer nuclear layer. Outcomes were correlated with best corrected visual acuity (BCVA) 12 months after surgery. RESULTS: BCVA was correlated with CPRT and PRD. Regression analysis and receiver operating characteristics curve analysis showed that CPRT >33 microm (OR 12.5) and PRD <177 microm (OR 9.86) were highly predictive for regaining reading vision (> or =69 Early Treatment of Diabetic Retinopathy Study letters) 12 months after surgery. No significant difference was found in postoperative macular morphology between subgroups. CONCLUSIONS: Poor vision after 12 months despite macular hole closure was associated with attenuation and disruption of the foveolar photoreceptor matrix. The extent of attenuation and disruption was independent of peeling and staining. TRIAL REGISTRATION NUMBER: NCT00302328.

Calcium-independent phospholipase A2 regulates retinal pigment epithelium proliferation and may be important in the pathogenesis of retinal diseases.

Calcium-independent phospholipase A2, group VIA (iPLA2-VIA) is involved in cell proliferation. This study aimed to evaluate the role of iPLA2-VIA in retinal pigment epithelium (RPE) cell proliferation and in retinal diseases involving RPE proliferation. A human RPE cell line (ARPE-19) was used to explore this role in vitro. Proliferating ARPE-19 cells had increased expression and activity of iPLA2-VIA. iPLA2-VIA was found in the nuclei of proliferating ARPE-19 cells, whereas in confluent ARPE-19 cells, with limited proliferation, iPLA2-VIA was primarily found in the cytosol. Inhibition of iPLA2-VIA decreased the rate of proliferation, whereas over expression of iPLA2-VIA increased the rate of proliferation. Using an experimental porcine model of RPE proliferation we demonstrated significant nuclear upregulation of iPLA2-VIA in proliferating RPE cells in vivo. We furthermore evaluated the expression of iPLA2-VIA in proliferative vitreoretinopathy (PVR). PVR membranes revealed nuclear expression of iPLA2-VIA in the RPE cells which had migrated and participated in the formation of the membranes. Overall, the present results point to an important role of iPLA2-VIA in the regulation of RPE proliferation suggesting that iPLA2-VIA may be considered as a possible pharmaceutical target in retinal diseases involving RPE proliferation and migration.

Value of internal limiting membrane peeling in surgery for idiopathic macular hole stage 2 and 3: a randomised clinical trial.

AIM: To determine the effect of internal limiting membrane (ILM) peeling on anatomical and functional success rates in stage 2 and 3 idiopathic macular hole surgery (MHS). METHODS: Randomised clinical trial of stage 2 and 3 idiopathic macular hole without visible epiretinal fibrosis and with less than 1 year's duration of symptoms. Eyes were randomised to (1) vitrectomy alone without retinal surface manipulation, (2) vitrectomy plus 0.05% isotonic Indocyanine Green (ICG)-assisted ILM peeling or (3) vitrectomy plus 0.15% Trypan Blue (TB)-assisted ILM peeling. Main outcomes were hole closure after 3 and 12 months and best-corrected visual acuity after 12 months. RESULTS: 78 eyes were enrolled. Primary closure rates were significantly higher with ILM peeling than without peeling for both stage 2 holes (ICG peeling 100%, non-peeling 55%, p = 0.014) and for stage 3 holes (ICG peeling 91%, TB peeling 89%, non-peeling 36%, p<0.001). Visual outcomes in eyes with primary hole closure were not significantly different between the groups. CONCLUSIONS: Dye-assisted ILM peeling was associated with significantly higher closure rates than non-peeling in both stage 2 and 3 MHS. Intraoperative ILM staining with 0.05% isotonic ICG was not associated with a significantly different visual outcome than non-peeling or TB peeling in eyes with primary hole closure. TRIAL REGISTRATION NUMBER: NCT00302328.

Normative data of outer photoreceptor layer thickness obtained by software image enhancing based on Stratus optical coherence tomography images.

AIM: To present normative data of outer photoreceptor layer thickness obtained by a new semiautomatic image analysis algorithm operating on contrast-enhanced optical coherence tomography (OCT) images. METHODS: Eight Stratus OCT3 scans from identical retinal locations from 25 normal eyes were registered and combined to form a contrast-enhanced average image. Utilising the vertical intensity gradients of the enhanced OCT images to demarcate retinal layers, thickness measurements of the outer photoreceptor- and retinal pigment epithelium layer (RPE-OS(complex)) were obtained. Additionally backscattered light within the outer nuclear layer (ONL) in the fovea was registered and compared with backscattered light within the ONL in the peripheral part of the macula (I(ratio)-ONL). RESULTS: The mean RPE-OS(complex) thickness in the foveal centre was 77.2 microm (SD = 3.95). The RPE-OS(complex) thickness in the superior macula 0.5-3 mm of the centre was significantly increased as compared with the corresponding inferior retina. In healthy subjects, the I(ratio)-ONL was 1.06. CONCLUSIONS: Contrast-enhanced OCT images enable quantification of outer photoreceptor layer thickness, and normative values may help understanding better the relationship between functional outcome and photoreceptor morphology in retinal diseases.

Indomethacin decreases optic nerve oxygen tension by a mechanism other than cyclo-oxygenase inhibition.

AIMS: We investigated the effect of several Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), on the preoptic nerve oxygen tension (ONPO2), as indomethacin previously has demonstrated a strong decreasing effect on ONPO2. We tested whether these NSAIDs, like indomethacin, also reduce the increasing effect of dorzolamide on ONPO2. METHODS: ONPO2 was measured 0.5 mm above the optic disc in 23 domestic pigs (26-36 kg) with a polarographic oxygen-sensitive electrode. One of the following NSAIDs was administered intravenously as increasing doses or as one large dose: indomethacin, ibuprofen, diclofenac, ketoprofen, parecyclo-oxygenase-2 inhibitor and lornoxicam. Indomethacin was both tested alone and after preceding administration of the other NSAIDs. Dorzolamide was also tested after preceding administration of NSAIDs different from indomethacin. RESULTS: Indomethacin decreased ONPO2 significantly in a dose-dependent manner. None of the other NSAIDs produced any effect on the ONPO2 (p>>0.05; n = 17). No difference was found between the effect of indomethacin injected alone, and after preceding administration of the other NSAIDs. Intravenous dorzolamide (500 mg) increased ONPO2 by 32 (7)% (n = 7; p<0.001) after preceding administration of several NSAIDs different from indomethacin. CONCLUSIONS: Indomethacin decreased ONPO2, while the other NSAIDs showed no effect on ONPO2, and they did not affect the effect of indomethacin. The hypoxic effect of indomethacin must be due to another mechanism than cyclo-oxygenase inhibition. The effect of dorzolamide on ONPO2 is not related to prostaglandin production.

Scrutinizing incident reporting in anaesthesia: why is an incident perceived as critical?

BACKGROUND: The purpose of the present study was to measure the incidence and type of incidents that occurred in relation to anaesthesia and surgery during a 1-year period in six Danish hospitals. Furthermore, we wanted to identify risk factors for incidents, as well as risk factors for incidents being deemed critical. METHODS: A four-page questionnaire describing patient data, type of anaesthesia and surgery, and occurrence of incidents was filled in for all anaesthesias in the period, and subsequently processed. The incident reporting form incorporated 59 predefined adverse events. The occurrence of one or more of these events described the incident. When the reporting anaesthetist deemed that an incident had harmed the patient, that incident was defined as critical. RESULTS: A total of 64,312 anaesthesias were reported, and in 7754 of them one or more incidents occurred. A total of 8510 incidents occurred, 4077 of them were solely related to the anaesthetic procedure, 3702 described events related to physiological alterations in the patient (physiological incidents). Three hundred and twenty-three of the incidents were deemed critical. High ASA score, high age, abdominal surgery, urgent surgery, and complex anaesthetic procedure were significant risk factors for physiological incidents and critical incidents. We could not identify a simple subset of adverse events that could adequately be used to describe the critical incidents. However, complex incidents, i.e. incidents involving more than one adverse event, were more likely to be deemed critical than simple incidents. CONCLUSION: The incidence of incidents was 12.1%, and the incidence of critical incidents was 0.5%. Incidents were more likely to be deemed critical in patients with an ASA score of III and above undergoing urgent surgery.

Indomethacin lowers optic nerve oxygen tension and reduces the effect of carbonic anhydrase inhibition and carbon dioxide breathing.

BACKGROUND/AIMS: Prostaglandins are important in blood flow regulation. Carbon dioxide (CO(2)) breathing and carbonic anhydrase inhibition increase the oxygen tension in the retina and optic nerve. To study the mechanism of this effect and the role of cyclo-oxygenase in the regulation of optic nerve oxygen tension (ONPO(2)), the authors investigated how indomethacin affects ONPO(2) and the ONPO(2) increases caused by CO(2) breathing and carbonic anhydrase inhibition in the pig. METHODS: Optic nerve oxygen tension was measured in 11 pigs with a polarographic oxygen electrode. The tip of the electrode was placed 0.5 mm above the optic disc. The effects of indomethacin, CO(2) breathing (3%) before and after indomethacin treatment, and carbonic anhydrase inhibition with or without indomethacin treatment were investigated. RESULTS: Administration of 300 mg indomethacin decreased optic nerve oxygen tension significantly. Carbonic anhydrase inhibition and CO(2) breathing increased ONPO(2) significantly. After indomethacin had been given, the rise in ONPO(2) caused by CO(2) breathing and carbonic anhydrase inhibition was significantly reduced. CONCLUSION: Systemic administration of indomethacin decreases the optic nerve oxygen tension; this is probably the result of decreased blood flow through vasoconstriction of vessels in the optic nerve. Additionally, indomethacin diminishes the ONPO(2) increasing effect of CO(2) breathing and carbonic anhydrase inhibition, thus affecting the reactivity of vessels in the optic nerve.

Optic nerve oxygen tension: the effects of timolol and dorzolamide.

BACKGROUND/AIMS: The authors have previously reported that carbonic anhydrase inhibitors such as acetazolamide and dorzolamide raise optic nerve oxygen tension (ONPO(2)) in pigs. The purpose of the present study was to investigate whether timolol, which belongs to another group of glaucoma drugs called beta blockers, has a similar effect. In addition, the effect of dorzolamide and timolol in combination was studied. METHODS: Polarographic oxygen electrodes were placed transvitreally over the optic disc in anaesthetised pigs and ONPO(2) was recorded continually. Drugs were administered intravenously either as 100 mg timolol followed by 500 mg dorzolamide (n = 5), 500 mg dorzolamide followed by 100 mg timolol (n = 5), or 100 mg timolol and 500 mg dorzolamide given simultaneously (n = 5). Arterial blood pressure, blood gasses, and heart rate were recorded. RESULTS: ONPO(2) was unaffected by administration of 100 mg timolol as an intravenous injection (n = 5). Administration of 500 mg dorzolamide by itself significantly increased ONPO(2) from 2.96 (SD 0.62) kPa to 3.69 (SD 0.88) kPa (n = 4, p = 0.035). The dorzolamide induced ONPO(2) increase was not significantly different from the ONPO(2) increases were seen when dorzolamide was administered simultaneous with (n = 5) or 35 minutes (n = 5) after 100 mg timolol. CONCLUSION: Systemic administration of timolol does not affect the optic nerve oxygen tension despite its lowering effect on the intraocular pressure. Additionally, timolol does not affect the ONPO(2) increasing effect of dorzolamide.

Superantigen presentation by human retinal pigment epithelial cells to T cells is dependent on CD2-CD58 and CD18-CD54 molecule interactions.

Human retinal pigment epithelial (RPE) cells are capable of presenting bacterial superantigens (SAg) to T cells in vitro by ligation of MHC class II molecules on RPE cells with the T cell receptor. The purpose of this study was to evaluate the involvement of adhesion molecules in presentation of SAg. Cultured human fetal and adult RPE cells were treated with interferon-gamma (IFN-gamma, 500 U ml(-1) for 72 hr) and afterwards pulsed with the SAg staphylococcal enterotoxin A (SEA, 500 ng ml(-1) for 2 hr) followed by coculture with freshly obtained T cells isolated from peripheral blood. Proliferation was measured by (3)H-thymidine incorporation assay. In selected experiments, either RPE or T cells were pre-treated with blocking antibodies specific for cell surface molecules. For comparison, dendritic cells were used as superantigen presenting cells for T cells. This study showed that presentation of SEA by RPE cells to resting T cells was dependent on the presence of the molecules CD2, CD58 and CD18, CD54. The cycling status of T cells was decisive, thus resting T cells but not activated T cells were capable to proliferate in response to SEA presentation. Proliferation of T cells induced by adult RPE cells was comparable to the proliferation induced by dendritic cells at concentrations of SAg above 100 ng ml(-1), but at concentrations of SAg below 10 ng ml(-1) the response was significantly lower for SAg presented by RPE cells compared to dendritic cells. The results demonstrate that CD2-CD58 and CD18-CD54 interactions are critical for SAg presentation by RPE cells to T cells. The findings thus suggest that also presentation of peptides to resting T cells by RPE cells may be dependent upon these interactions.

The prevalence and causes of bilateral and unilateral blindness in an elderly urban Danish population. The Copenhagen City Eye Study.

PURPOSE: To study the prevalence and causes of bilateral and unilateral blindness in an elderly urban Danish population. METHODS: Data originated from a Danish epidemiologic cross-sectional random sample population eye survey conducted during the years 1986-1988. The population consisted of 1,000 inhabitants aged 60 to 80 years in Copenhagen. The participants underwent an extensive ophthalmologic examination. A participation rate of 96.9% was achieved. Any blindness was defined as best-corrected visual acuity (VA) worse than 0.05 (the WHO criteria) and VA of 0.1 or worse (the National criteria (NC) of blindness). RESULTS: The prevalence rates of bilateral and unilateral blindness were, respectively, 0.53% and 3.38% according to WHO, but 1.06% and 4.44% using NC. Bilateral blindness rose significantly with age (p=0.02). According to NC, age-related macular degeneration (AMD) was the leading cause of bilateral blindness, accounting for 60% of all blind persons. Glaucoma, myopic macular degeneration, cataract and retinitis pigmentosa were jointly the second most common cause, each accounting for 10% of all bilaterally blind persons. Diabetic retinopathy was not a cause of bilateral blindness. Amblyopia was the most frequent, AMD the second most frequent, and diabetic retinopathy was among the third most common cause of unilateral blindness accounting for, respectively, 28.60%, 16.66% and 9.52% of all unilateral blindness. CONCLUSIONS: Blindness was associated with increasing age. A calculation indicates that among Danes aged 60 to 80 years 7,736 are bilaterally blind and 35,503 suffer from unilateral blindness. This study highlights AMD as the most important cause.

[Age related macular degeneration. A widespread disease]. / Aldersrelateret maculadegeneration. En folkesygdom.

Age-related macular degeneration, AMD, is the commonest cause of legal blindness in the industrialised world. Epidemiological data suggest that in Denmark more than 80,000 persons suffer impaired vision in at least one eye, because of AMD. More than 4000 are legally blind owing to this disease. AMD has two major phenotypes: wet and dry. Most severe visual losses are caused by wet AMD, where new blood vessels form under the macula. A new treatment of this condition is now available. Photodynamic therapy with verteporfin has been investigated in a double-blind, randomised clinical trial with more than 600 patients. This study has been scrutinised by a Cochrane review, which has recommended criteria for the treatment. For eyes meeting these inclusion criteria, photodynamic therapy can reduce the occurrence of moderate and severe visual loss over a two-year period by more than 60%. It is estimated that around 1000 eyes in Denmark will meet the inclusion criteria for photodynamic therapy.

The anterior lens capsule used as support material in RPE cell-transplantation.

PURPOSE: To investigate the use of an ocular basement membrane as support material for transplanted porcine RPE cells. METHODS: Porcine RPE cells were grown on bovine corneal extracellular matrix (ECM), isolated bovine- and porcine lens capsules, and tissue culture plastic. Cell density, and cell morphology were studied by phase contrast microscopy and transmission electron microscopy. RESULTS: RPE cells grown on porcine anterior lens capsule and on ECM obtained better morphology and higher final cell density than cells grown on plastic and on bovine anterior lens capsule. It was possible to transplant the porcine anterior lens capsule to the subretinal space in pigs. Within two weeks of observation, the lens capsule was well tolerated in the subretinal space. CONCLUSION: The anterior lens capsule seems to be promising as support material for use in RPE cell-transplantation.

Optic nerve oxygen tension: effects of intraocular pressure and dorzolamide.

AIM: To investigate the influence of acute changes in intraocular pressure on the oxygen tension in the vicinity of the optic nerve head under control conditions and after intravenous administration of 500 mg of the carbonic anhydrase inhibitor dorzolamide. METHODS: Domestic pigs were used as experimental animals. Oxygen tension was measured by means of a polarographic electrode in the vitreous 0.5 mm anterior to the optic disc. This entity is called the optic nerve oxygen tension. Intraocular pressure was controlled by a hypodermic needle inserted into the anterior chamber and connected to a saline reservoir. RESULTS: When the intraocular pressure was clamped at 20 cm H2O optic nerve oxygen tension was 20 (5) mm Hg (n=8). Intravenous administration of dorzolamide caused an increase in optic nerve oxygen tension of 43 (8)% (n=6). Both before and after administration of dorzolamide optic nerve oxygen tension was unaffected by changes in intraocular pressure, as long as this pressure remained below 60 cm H2O. At intraocular pressures of 60 cm H(2)O and below, dorzolamide significantly increased optic nerve oxygen tension. CONCLUSION: Intravenous administration of 500 mg dorzolamide increases the oxygen tension at the optic nerve head during acute increases in intraocular pressure.