The EOG in Best's disease and dominant cystoid macular dystrophy (DCMD)

Novel Presenting Phenotype in a Child With Autosomal Dominant Best's Vitelliform Macular Dystrophy

Best's macular dystrophy (BMD) usually manifests with visual failure in the first or second decade of life; however, there is a large variability in expressivity of the disease, and some patients have no manifestation other than a pathological electro-oculogram (EOG). Autosomal dominant Best's vitelliform macular dystrophy (AD-BVMD) has a very specific phenotype that varies with the stage of the disease. In recent years, the authors have seen description of another clinical entity known as autosomal recessive BMD. Herein, the authors describe a 5-year-old girl referred from a peripheral hospital for investigation with a positive family history of BMD. Clinical findings included best-corrected visual acuity of 0.325 and 0.300 in the right and left eyes, respectively, by Sonksen logMar test, full color vision, normal orthoptic examination, and a small degree of hyperopia consistent with age. Macular optical coherence tomography (OCT) showed intraretinal fluid cysts and EOG showed reduced Arden ratio. Genetic testing was done for the proband and her father, who were found to be heterozygous for c.37C>T p. (Arg13Cys). The proband's younger sister will be reviewed and followed up once of age. The authors identified a new phenotype of AD-BVMD; although this is a single patient, more young children with BMD can now be scanned with the availability of hand-held OCT with better knowledge of the phenotype. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:580-585.].

ELECTROOCULOGRAPHY BASED READING SPEED ANALYSIS AS AN ASSISTIVE TOOL

Dyslexia is a well-known reading disorder that involves difficulty in fluent reading, decoding and processing of words despite adequate intelligence. It is common that the reading speed of dyslexic patients is lower than their normal counterparts, because of slow letter and word processing. Eye movements in dyslexic patients are significantly different from that of normal individuals, in terms of the presence of frequent fixations and stares in the former. This work proposes a Human Computer Interactive system to assist individuals having low reading speed to increase their reading speed by the analysis of eye movements. Eye movement data for different reading speeds is recorded using a laboratory developed Electrooculogram acquisition system. From the data, Adaptive Autoregressive (AAR) parameters, Band Power Estimates and Wavelet Coefficients are extracted as signal features. Reading speeds are classified using different pattern classifiers from which an average accuracy of 94.67% over all classes and participants is obtained using Radial Basis Function (RBF) Support Vector Machine (SVM) Tree classifier and AAR Parameters as features. Friedman test is done to select the best classifier. The trained classifier is used to recognize the reading speeds of a set of new normal individuals. If the reading speeds are less than a preset threshold, that individual is trained repeatedly for 10 days for improvement. An improvement of reading speed is observed by the decrease in the misclassification rate from 45.1% to 9.92% in 10 days for the fastest speed (1 sentence/2 s) over all the subjects. This work is carried out on healthy individuals. However, the results reveal that the proposed system may also be used for training and assisting children with dyslexia or other similar reading disabilities children.

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.

Alcohol- and light-induced electro-oculographic responses in age-related macular degeneration & central serous chorioretinopathy. alcohol- and light-induced EOG responses in ARMD & CSC

The non-photic electro-oculographic (EOG) response induced by alcohol has been proposed as an indicator of retinal pigment epithelial (RPE) integrity, and reported to be abnormal in age-related macular degeneration (ARMD). To evaluate this proposal, we have measured the alcohol-EOG as well as the ISCEV-standard EOG in patients with ARMD (n=11 patients, 4 eyes with drusen, 8 eyes with 'dry' and 7 eyes with 'wet' lesions) and central serous chorioretinopathy (CSC, n=11 patients, 7 eyes with active and 6 eyes with inactive lesions), compared with 29 normal controls. We recorded the alcohol-induced EOG response after a single oral administration of ethanol at 160 mg/kg, followed by an ISCEV-standard EOG. Blood alcohol levels were monitored with a breath analyzer. We found that neither the alcohol-EOG nor the light-induced EOG response showed any difference between either ARMD or CSC patients and normal controls. Nor was there difference among eyes of different ARMD or CSC subgroups. In addition, blood alcohol concentrations near the time of the alcohol-EOG peak showed no obvious relationship with peak/baseline ratios. These data suggest that neither the alcohol- nor the light-induced EOG is a sensitive indicator of these diseases.

Alcohol- and light-induced electro-oculographic responses: variability and clinical utility

The alcohol-induced electro-oculographic (EOG) response has been proposed by Arden as an indicator of retinal pigment epithelial (RPE) integrity. We have evaluated the consistency of the alcohol-EOG with respect to clinical applicability and compared this response to the ISCEV-standard EOG. We recorded, in a group of normal subjects (n=29, 14 men with mean age 42+/-11 years and 15 women with mean age 36+/-13 years), the alcohol response to a single oral dose of ethanol at 160 mg/kg (as 40 proof vodka, drunk in 15 s after 12 h of fasting), followed by an ISCEV-standard EOG 90 min after alcohol administration. Blood alcohol levels were monitored at regular intervals with a breath analyzer. We found a wide range of amplitudes in both light and alcohol responses among participants, from minimal to large values. Subjects had a wide range of blood alcohol concentrations from 0.02 to 0.10%; near the time of the response peak, but there was no relationship between alcohol levels and peak/baseline ratios. In addition, there was no relationship between alcohol peak/baseline ratio and the Arden ratio. Neither the alcohol nor the light response parameters showed any relationship with age or gender. Some of the inter-individual variability in the EOG response to alcohol may reflect variable absorption of oral alcohol. The alcohol-induced EOG has too broad a range of responses to be useful clinically for the one-time evaluation of individual patients. We have similar concerns regarding clinical applications of the standard light-induced EOG.

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.

Genotype-phenotype correlations and differential diagnosis in autosomal dominant macular disease

In the past few years, great progress has been made in the understanding of macular diseases. A number of disease-causing genes have been cloned, and numerous loci for other conditions have been mapped. The purpose of this article is to provide an overview of the current understanding of the genotype-phenotype correlations in autosomal dominant macular diseases with an emphasis on differential diagnostic issues. Whenever possible, the molecular correlates have been reviewed and the implications for age-related macular degeneration have been discussed. The many similarities of these diseases to age-related macular degeneration of the atrophic or exudative type, which can be misleading in elderly subjects, have also been addressed. While some conditions yield disease truly confined to the macula, others show widespread retinal involvement on functional testing. Clear-cut genotype-phenotype correlations are possible only for some forms of macular diseases. To further complicate the diagnostic process, there is a considerable degree of clinical overlap between many of them, making the differential diagnostic process potentially challenging. Functional testing, careful assessment of family history and extensive family work-up are essential in differentiating at the clinical level most, but not all, of these disease entities. Awareness of all of these conditions is required to direct correctly diagnostic investigations, to formulate an accurate prognosis, and for proper genetic counseling.

Effect of alcohol and light on the retinal pigment epithelium of normal subjects and patients with retinal dystrophies

BACKGROUND

Light absorbed by photoreceptors causes oscillations in the voltage across the retinal pigment epithelium (RPE). This is the basis of the clinical test, electro-oculography (EOG). We have previously shown that alcohol causes a sequence of voltage changes which are so precisely the same as those caused by light that they must be produced by the same RPE machinery. There is good evidence that alcohol produces its effect by a direct action on the RPE. Consequently, in diseases associated with loss of photoreceptors, alcohol should continue to produce the voltage changes of the EOG unless secondary changes have occurred in the RPE.

METHODS

The alcohol response in patients with retinitis pigmentosa (RP) was investigated using EOG.

RESULTS

In no patient with RP was there any alcohol rise.

CONCLUSION

In patients with RP secondary abnormalities of function of the RPE must occur.