Clinical efficacy and safety of a light mask for prevention of dark adaptation in treating and preventing progression of early diabetic macular oedema at 24 months (CLEOPATRA): a multicentre, phase 3, randomised controlled trial.

BACKGROUND: We aimed to assess 24-month outcomes of wearing an organic light-emitting sleep mask as an intervention to treat and prevent progression of non-central diabetic macular oedema. METHODS: CLEOPATRA was a phase 3, single-blind, parallel-group, randomised controlled trial undertaken at 15 ophthalmic centres in the UK. Adults with non-centre-involving diabetic macular oedema were randomly assigned (1:1) to wearing either a light mask during sleep (Noctura 400 Sleep Mask, PolyPhotonix Medical, Sedgefield, UK) or a sham (non-light) mask, for 24 months. Randomisation was by minimisation generated by a central web-based computer system. Outcome assessors were masked technicians and optometrists. The primary outcome was the change in maximum retinal thickness on optical coherence tomography (OCT) at 24 months, analysed using a linear mixed-effects model incorporating 4-monthly measurements and baseline adjustment. Analysis was done using the intention-to-treat principle in all randomised patients with OCT data. Safety was assessed in all patients. This trial is registered with Controlled-Trials.com, number ISRCTN85596558. FINDINGS: Between April 10, 2014, and June 15, 2015, 308 patients were randomly assigned to wearing the light mask (n=155) or a sham mask (n=153). 277 patients (144 assigned the light mask and 133 the sham mask) contributed to the mixed-effects model over time, including 246 patients with OCT data at 24 months. The change in maximum retinal thickness at 24 months did not differ between treatment groups (mean change -9·2 µm [SE 2·5] for the light mask vs -12·9 µm [SE 2·9] for the sham mask; adjusted mean difference -0·65 µm, 95% CI -6·90 to 5·59; p=0·84). Median compliance with wearing the light mask at 24 months was 19·5% (IQR 1·9-51·6). No serious adverse events were related to either mask. The most frequent adverse events related to the assigned treatment were discomfort on the eyes (14 with the light mask vs seven with the sham mask), painful, sticky, or watery eyes (14 vs six), and sleep disturbance (seven vs one). INTERPRETATION: The light mask as used in this study did not confer long-term therapeutic benefit on non-centre-involving diabetic macular oedema and the study does not support its use for this indication. FUNDING: The Efficacy and Mechanism Evaluation Programme, a Medical Research Council and National Institute for Health Research partnership.

Hypoxia and oxidative stress in the causation of diabetic retinopathy.

Diabetic retinopathy is associated with hyperglycemia, and there is convincing evidence that oxidative stress (the overproduction of reactive oxygen species (ROS)) measured indirectly in patients, is related to the severity of diabetic complications. Also, reducing such stress by various means, including drugs and reducing hyperglycemia, decreases the rate of development of diabetic retinopathy (DR). It is therefore supposed that oxidative stress causes DR, and the injuries caused by ROS in retinas of diabetic animals (and in human preparations). But the cells first affected in small animal models of DR are found throughout the inner retina, and not specifically associated with small blood vessels until later in the development of retinopathy. We raise the questions A: why in human disease the small retinal blood vessels are so selectively affected B: what are the processes that induce oxidative damage in the retina. There are difficulties in interpretation of experimental results, because there is no metric which relates the degree of damage to the level of ROS, either in clinical or animal experiments and the relative sensitivity of the different methods employed to demonstrate oxidative damage in experiments on tissues is unquantified. It is also important to note that in addition to oxidative stress, hyperglycemia induces several changes including leucostasis, vasoconstriction and a pro-inflammatory state that also causes hypoxia in the retina. The earliest retinal pathology and the earliest biochemical changes appear to begin within 1 week of the time when the animals become diabetic and are provoked by hyperglycemia. These changes include alterations to the appearance of microglia, the formation of Advanced Glycation Endproducts (AGEs), the overproduction of Vascular Endothelial Growth Factor (VEGF) and its mRNA and consequent leakage of capillary endothelial cells. These early pro-inflammatory changes can directly cause hypoxia in the retina and not necessarily via ROS. Experiments on isolated cells indicate that retinal capillaries are less susceptible to hyperglycemia than other retinal cells, but in vivo are selectively damaged, possibly via paracrine changes. This suggests a new concept: although the changes in blood vessels may be a consequence of gradual and cumulative development of oxidative stress, the preceding paracrine and other changes that cause the development of oxidative stress are highly significant to the understanding and treatment of DR. The clinical importance is that about the time that oxidative stress becomes easily demonstrable, the progress of DR is already irreversible. A number of methods of treatment of DR depend upon the relief of retinal hypoxia. If oxidative stress is considered 'the' determinant of DR, explanation of such findings solely in terms of oxidative stress would require additional hypotheses.

Perceived color of hallucinations in the Charles Bonnet Syndrome is related to residual color contrast sensitivity.

BACKGROUND: We sought to determine whether the change in cortical excitability secondary to deafferentation in patients with Charles Bonnet Syndrome (CBS) who hallucinate in a predominant color or combination of colors is related to an alteration in color contrast thresholds and whether the change is specific to the color of the hallucination. METHODS: We prospectively categorized each patient's hallucinations using the Institute of Psychiatry Visual Hallucinations Interview. We measured color contrast thresholds with a computerized test designed to assess red-green and blue-yellow color confusion axes against a background of luminance noise. We calculated the ratio of red-green threshold to blue-yellow threshold (R-G/B-Y ratio) for each patient. Because central vision was impaired in all patients, we used a sectoral annular stimulus that projected to the retina at 12.5 degrees eccentricity. RESULTS: There were 10 patients with age-related macular degeneration and CBS who were hallucinating in a predominant color or combination of colors at the time of recruitment. Patients hallucinating in red, green, or a combination of red and green had R-G/B-Y ratios of less than 1.0 (n = 5). Patients hallucinating in blue, yellow, or a combination of blue and yellow had R-G/B-Y ratios of greater than 1.0 (n = 2). Patients hallucinating in purple had ratios between the red-green and blue-yellow hallucinators (n = 2). The 1 patient hallucinating in white had the lowest thresholds for red-green and blue-yellow confusion axes. Comparing the R-G/B-Y ratios for the "red/green hallucinators" and "blue/yellow hallucinators" returned a significant result with Fisher's exact test (P = 0.047, n = 7). CONCLUSIONS: Deafferentation and secondary cortical hyperexcitability in CBS have a correlate in psychophysical threshold. This change in sensitivity relates specifically to the hallucinated color axis rather than across all colors. This is the first published evidence for cerebral hyperexcitability leading to a decrease in color contrast thresholds.

The ChromaTest, a digital color contrast sensitivity analyzer, for diabetic maculopathy: a pilot study.

BACKGROUND: To assess the ability of the Chromatest in investigating diabetic maculopathy. METHOD: Patients with Type 2 diabetes and no concurrent ocular pathology or previous laser photocoagulation were recruited. Visual acuities were assessed followed by colour contrast sensitivity testing of each eye using Chromatest. Dilated fundoscopy with slit lamp biomicroscopy with 78 D lens was then performed to confirm the stage of diabetic retinopathy according to the Early Treatment Diabetic Retinopathy Study. RESULTS: 150 eyes in 150 patients were recruited into this study. 35 eyes with no previous laser photocoagulation were shown to have clinically significant macular oedema (CSMO) and 115 eyes with untreated non-proliferative diabetic retinopathy (NPDR) on fundus biomicroscopy. Statistical significant difference was found between CSMO and NPDR eyes for protan colour contrast threshold (p = 0.01). Statistical significance was found between CSMO and NPDR eyes for tritan colour contrast threshold (p = 0.0002). Sensitivity and specificity for screening of CSMO using pass-fail criterion for age matched TCCT results achieved 71% (95% confidence interval: 53-85%) and 70% (95% confidence interval: 60-78%), respectively. However, threshold levels were derived using the same data set for both training and testing the effectiveness since this was the first study of NPDR using the Chromatest CONCLUSION: The ChromaTest is a simple, cheap, easy to use, and quick test for colour contrast sensitivity. This study did not achieve results to justify use of the Chromatest for screening, but it reinforced the changes seen in tritan colour vision in diabetic retinopathy.

Light and alcohol evoked electro-oculograms in cystic fibrosis.

Cystic fibrosis (CF) is caused by a defect in the cystic fibrosis transmembrane conductance regulator (CFTR) which is a chloride channel. CFTR is expressed in the retinal pigment epithelium (RPE) where it is believed to be important in generating the fast oscillations (FOs) and potentially contributing to the light-electro-oculogram (EOG). The role of CFTR in the alcohol-EOG is unknown. We recruited six individuals with CF (three homozygotes for Delta508 and three heterozygous for Delta508) and recorded the light- and alcohol-EOGs as well as the FOs and compared them to a control group. The results showed that in the CF group the amplitude of the alcohol- and light-EOGs were normal. However, the time to peak of the light- and alcohol-rises were significantly faster than in the control group. We conclude that CFTR is not primarily responsible for the alcohol- or light-rises but is involved in altering the timing of these responses. The FOs showed differences between the homozygotes, heterozygotes and the controls. The amplitudes were significantly higher and the time to the dark troughs were significantly slower in the heterozygote group compared to both controls and the homozygotes. In contrast, the homozygotes did not differ in either amplitude or the timing of the FOs compared to the controls.

P-Glycoprotein expression in human retinal pigment epithelium cell lines.

P-Glycoprotein (P-gp), an active efflux transporter encoded by the MDR1 gene, has recently been identified in the human and pig retinal pigment epithelium (RPE) in situ. Efflux pumps such as P-gp are major barriers to drug delivery in several tissues. We wished to establish whether human RPE cell lines express P-gp under the culture conditions recommended for each cell line so as to determine their suitability as in vitro models for predicting drug transport across the outer blood-retinal barrier. Three human RPE cell lines, ARPE19, D407 and h1RPE were investigated. Reverse transcriptase-polymerase chain reaction (RT-PCR) was carried out to determine the expression of MDR1 mRNA. Immunocytochemistry using the P-gp-specific antibody C219 was undertaken to investigate the presence of P-gp protein in each cell type. Uptake of rhodamine 123, a P-gp substrate, in the presence or absence of pre-treatment with a P-gp inhibitor, verapamil, was measured in each cell line to determine functional expression of P-gp. For all experiments, MDCK cells stably transfected with the human MDR1 gene (MDCK-MDR1) were used as a positive control. ARPE19 cells were consistently negative for P-gp as assessed by RT-PCR and immunocytochemistry. By contrast, RT-PCR of D407 and h1RPE samples yielded weak bands corresponding to MDR1; P-gp protein expression, as demonstrated by C219 immunoreactivity, was also present. Rhodamine uptake after treatment with verapamil was significantly greater in D407 and MDCK-MDR1, indicating functional expression of P-gp in these two cell lines. No evidence of functional P-gp was found in ARPE19 and h1RPE. In conclusion, D407 and h1RPE cells express P-gp, though functional activity was demonstrable only in D407 cells. ARPE19 cells do not express P-gp. Of these human RPE cells lines D407 could be considered as a suitable model for in vitro drug transport studies, particularly those involving P-gp substrates, without modification of their usual culture conditions.

The electro-oculogram.

The retinal pigment epithelium (RPE) lying distal to the retina regulates the extracellular environment and provides metabolic support to the outer retina. RPE abnormalities are closely associated with retinal death and it has been claimed several of the most important diseases causing blindness are degenerations of the RPE. Therefore, the study of the RPE is important in Ophthalmology. Although visualisation of the RPE is part of clinical investigations, there are a limited number of methods which have been used to investigate RPE function. One of the most important is a study of the current generated by the RPE. In this it is similar to other secretory epithelia. The RPE current is large and varies as retinal activity alters. It is also affected by drugs and disease. The RPE currents can be studied in cell culture, in animal experimentation but also in clinical situations. The object of this review is to summarise this work, to relate it to the molecular membrane mechanisms of the RPE and to possible mechanisms of disease states.

The multifocal pattern electroretinogram in chloroquine retinopathy.

PURPOSE: Optimal screening for ocular toxicity caused by chloroquine and hydroxychloroquine is still controversial. With the multifocal pattern electroretinogram (mfPERG), a new electrophysiological technique has recently become available to detect early changes of ganglion cells. In this study this new technique is applied to a series of 10 patients seen consecutively receiving long-term chloroquine medication. METHODS: In 10 patients receiving chloroquine medication, clinical examination, Amsler visual field testing and computerized color vision testing were performed. If toxicity was suspected, automated perimetry was carried out. In addition, in all patients conventional pattern electroretinogram (PERG) and mfPERG testing were performed. RESULTS: On clinical examination 8 patients showed no chloroquine-associated maculopathy, while 2 patients did. Of these 2, only 1 reported abnormalities when viewing the Amsler chart, while automated perimetry showed typical, ring-like paracentral scotomas in both affected patients and color vision was significantly abnormal. In the normal patients, 4 of 8 had a mild color vision disturbance, which correlated to age-related macular changes. The amplitudes of the PERG and the central (approximately 10 degrees ) responses of the mfPERG were markedly reduced in chloroquine maculopathy, while the latencies were unchanged. The peripheral rings of mfPERG (ranging to 48 degrees ) were not affected by chloroquine toxicity. Both PERG and mfPERG were less affected by age-related macular changes. CONCLUSIONS: The reduction of PERG and central mfPERG responses in chloroquine maculopathy may help with the early detection of toxicity.

Two components of the human alcohol electro-oculogram.

Light onset or drinking alcohol causes the standing potential of the eye to rise and then fall to a trough (the EOG). After allowing for the time for the alcohol to be absorbed into the blood stream, the changes of current with time are identical for the two agents but each acts through a separate pathway, on the same effector mechanism. We have shown that +ve and -ve processes of the alcohol-EOG may be differentially affected in disease. We have now determined the separate dose-response relationship of the two voltage changes. Alcohol diluted with water was given by mouth to fasting dark-adapted subjects. Recordings continued until both the positive peak and the later negative trough were well-characterised. Doses of alcohol ranged from 3.54 to 450 mg Kg(-1) of body weight. Experiments were carried out on three normal subjects, 4-8th decade. The results are consistent with the hypothesis that each voltage change is determined by the relation: [EtOH] x [R] <--> [EtOH.R], where <--> represents a reversible reaction. For the +ve peak, semi-saturation occurs at approximately 35 mg Kg(-l). For the -ve trough it is smaller, 11 mg Kg(-l). Therefore the result is consistent with there being 2 distinct processes, and the human EOG cannot be a single 'damped oscillation'. During the short period when change of blood alcohol concentration is effective in causing the EOG sequence (using doses which provoke large voltage changes), the computed blood concentration varies from 0.01 to 0.1 mM, i.e. is > 2 orders of magnitude less than the levels required for intoxication.

The multifocal pattern electroretinogram in glaucoma.

BACKGROUND: The pattern ERG can be used to detect early glaucomatous change, because the response of cells in the inner retina from (typically) 20 degrees -40 degrees of area is reduced before perimetric abnormality is certain. The multifocal pattern electroretinogram (mfPERG) allows analysis of many local regions within this area. The aim of this study was to investigate whether in patients with presumed glaucoma the mfPERG permits diagnosis and discrimination from normals. METHODS: Measurements on 25 age-related normal eyes were compared to those on 23 eyes with different stages of glaucoma. A RETIScan system was used to generate a stimulus pattern of 19 hexagons, each consisting of six triangles. The triangles pattern-reversed black to white at 75 Hz. Those 19 hexagons were grouped into three stimulus regions: a central field, a middle, and a peripheral ring. The complete array subtended 48 degrees at the eye. The hexagons alternated between black and white, in a temporal pattern that followed a corrected binary m-sequence (length 512, 10 cycles with 39 s each). The amplitudes and latencies of positive responses at approximately 50 ms (P-50) and negative responses at approximately 95 ms (N-95) were analyzed. RESULTS: In patients with glaucoma the P-50 and N-95 components of the mfPERG were significantly reduced for the central area and both outer rings compared to normal volunteers (p<0.001, Mann-Whitney-U). The most distinct reduction was observed for N-95 and the central ring. Changes in latencies were not conclusive. The reduction of the components increased with the stage of glaucoma. A predictive model for detecting early glaucomatous changes was designed based on P-50-N-95 with 88% sensitivity and 76% specificity. CONCLUSION: In glaucoma a marked reduction of components, especially centrally is observed in the mfPERG. This hints to an early involvement of central ganglion cells and may be useful for future functional tests.

Differential effects of light and alcohol on the electro-oculographic responses of patients with age-related macular disease.

PURPOSE: Alcohol (EtOH) affects the electro-oculogram (EOG) in ways very similar to light, although the two agents act on the RPE through different routes. Are the EOGs to light and to alcohol affected similarly in age-related macular degeneration (AMD) and age-related maculopathy (ARM)? METHODS: Standard eye movements and recording of EOGs were used. After 26 minutes of baseline recording in darkness, subjects were either exposed to 30 cd/m(2) light or drank 226 mg/kg alcohol (7.1% vol/vol) in water. RESULTS: In 17 patients with ARM and AMD (aged 67-86 years; mean, 77), the light-EOG was slowed in comparison to normal, and the voltage changes were somewhat reduced. The mean reduction in the alcohol-EOG (EtOH-EOG) was much greater. The reduction was equal in the two eyes, regardless of uniocular foveal impairment. Some EtOH-EOG loss occurred in patients with minor fundus changes and no loss of acuity, but the loss was greater in patients with "wet" or "dry" ARM and AMD. Grading of RPE changes correlated with the decrease in EtOH-EOG responsiveness, but not with light-EOG responsiveness. CONCLUSIONS: EtOH- and light-EOGs are affected differentially. In ARM, even with minor fundus changes, patients appear to have a general abnormality in the RPE. The alcohol response abnormality is correlated to the fundus appearance, but not with age. These results provide further evidence that EtOH acts by a pathway different from that governing the action of light. These results support histologic and other evidence that in ARM there is a functional barrier between the choroid and the RPE-retina.