Autoantibodies detection in patients affected by autoimmune retinopathies

OBJECTIVE

Autoimmune retinopathies (ARs) encompass a spectrum of immune diseases that are characterized by the presence of autoantibodies against retinal proteins in the bloodstream. These autoantibodies (AAbs) lead to a progressive and sometimes rapid loss of vision. ARs commonly affect subjects over 50 years of age, but also rare cases of kids under 3 years of age have been reported.

PATIENTS AND METHODS

In this study, 47 unrelated Caucasian patients were enrolled. All subjects showed negative cancer diagnoses and negative results in their genetic screenings. We studied 8 confirmed retinal antigens using Western blotting analysis, with α-enolase followed by carbonic anhydrase II being the two most frequently found in the patients' sera.

RESULTS

Nineteen patients were positive (40.4%), thirteen uncertain (27.7%), and fifteen were negative (31.9%). Their gender did not correlate with the presence of AAbs (p=0.409).

CONCLUSIONS

AAbs are responsible for retinal degeneration in some cases, while in others, they contribute to exacerbating the progression of the disease; however, their detection is crucial to reaching a better diagnosis and developing more effective treatments for these conditions. Moreover, finding good biomarkers is important not only for AR monitoring and prognosis, but also for helping with early cancer diagnosis.

Bioetics Issues of Artificial Placenta and Artificial Womb Technology

Abstract

The worldwide infertility crisis and the increase in mortality and morbidity among infants, due to preterm births and associated complications, have stimulated research into artificial placenta (AP) and artificial womb (AW) technology as novel solutions. These technologies mimic the natural environment provided in the mother's womb, using chambers that ensure the supply of nutrients to the fetus and disposal of waste substances through an appropriate mechanism. This review aims to highlight the background of AP and AW technologies, revisit their historical development and proposed applications, and discuss challenges and bioethical and moral issues. Further research is required to investigate any negative effects of these new technologies, and ethical concerns pertaining to the structure and operation of this newly developed technology must be addressed and resolved prior to its introduction to the public sphere.

Human Cloning: Biology, Ethics, and Social Implications

Abstract

This scholarly article delves into the multifaceted domains of human cloning, encompassing its biological underpinnings, ethical dimensions, and broader societal implications. The exposition commences with a succinct historical and contextual overview of human cloning, segueing into an in-depth exploration of its biological intri-cacies. Central to this biological scrutiny is a comprehensive analysis of somatic cell nuclear transfer (SCNT) and its assorted iterations. The accomplishments and discoveries in cloning technology, such as successful animal cloning operations and advances in the efficiency and viability of cloned embryos, are reviewed. Future improvements, such as reprogramming procedures and gene editing technology, are also discussed. The discourse extends to ethical quandaries intrinsic to human cloning, entailing an extensive contemplation of values such as human dignity, autonomy, and safety. Furthermore, the ramifications of human cloning on a societal plane are subjected to scrutiny, with a dedicated emphasis on ramifications encompassing personal identity, kinship connections, and the fundamental notion of maternity. Culminating the analysis is a reiteration of the imperative to develop and govern human cloning technology judiciously and conscientiously. Finally, it discusses several ethical and practical issues, such as safety concerns, the possibility of exploitation, and the erosion of human dignity, and emphasizes the significance of carefully considering these issues.

In Memory of Professor Derek Pheby

Abstract

Professor Derek Pheby's passing in November 2022 marked a profound loss for the scientific community. Professor Derek Pheby, a stalwart figure in the fields of autoimmune diseases and bioethics, was known for his dedication to scientific research and patients' support, particularly for those affected by paraneoplastic autoimmune syndromes. Professor Pheby made significant contributions to research, especially about Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). His leadership of the ME Biobank and scientific coordination of EUROMENE demonstrated his commitment to pushing boundaries and fostering international collaborations. Professor Pheby's scientific work addressed various aspects of ME/CFS, from physician education to patient needs, the development of a post-mortem tissue bank, and effective treatments. Beyond his medical career, Professor Pheby was a crucial member of the Independent Ethics Committee of MAGI, he was a poet, humanitarian, and advocate for child protection. His generosity and boundless spirit left an enduring legacy, fostering innovative research in the pursuit of combating autoimmune diseases.

Neurofibromatosis type 1-associated optic pathway gliomas: pathogenesis and emerging treatments

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder associated with an increased risk of developing a variety of benign and malignant tumors. Fifteen to 20% of children with NF1 are diagnosed with an optic pathway glioma (NF1-OPG) before 7 years of age, and more than half of them experience visual decline. At present, no effective therapy is available for prevention, restoration, or even stabilization of vision loss in subjects affected by NF1-OPG. This paper aims to review the main emerging pharmacological approaches that have been recently assessed in preclinical and clinical settings. We performed a search of the literature using Embase, PubMed, and Scopus databases to identify articles regarding NF1-OPGs and their treatment up to July 1st, 2022. The reference lists of the analyzed articles were also considered a source of literature information. To search and analyze all relevant English articles, the following keywords were used in various combinations: neurofibromatosis type 1, optic pathway glioma, chemotherapy, precision medicine, MEK inhibitors, VEGF, nerve growth factor. Over the past decade, basic research and the development of genetically engineered mice models of NF1-associated OPG have shed light on the cellular and molecular mechanisms underlying the disease and inspired animal and human testing of several compounds. A promising line of research is focusing on the inhibition of mTOR, a protein kinase controlling proliferation, protein synthesis rate and cell motility that is highly expressed in neoplastic cells. Several mTOR blockers have been tested in clinical trials, the most recent of which employed oral everolimus with encouraging results. A different strategy aims at restoring cAMP levels in neoplastic astrocytes and non-neoplastic neurons, since reduced intracellular cAMP levels contribute to OPG growth and, more importantly, are the major determinant of NF1-OPG-associated visual decline. So far, however, this approach has only been attempted in preclinical studies. Stroma-directed molecular therapies - seeking to target Nf1 heterozygous brain microglia and retinal ganglion cells (RGCs) - are another fascinating field. Microglia-inhibiting strategies have not yet reached clinical trials, but preclinical studies conducted over the last 15 years have provided convincing clues of their potential. The importance of NF1-mutant RGCs in the formation and progression of OPGs also holds promise for clinical translation. The evidence of Vascular Endothelial Growth Factor (VEGF)- Vascular Endothelial Growth Factor (VEGFR) signaling hyperactivity in pediatric low-grade gliomas prompted the use of bevacizumab, an anti-VEGF monoclonal antibody, which was tested in children with low-grade gliomas or OPGs with good clinical results. Neuroprotective agents have also been proposed to preserve and restore RGCs and topical eye administration of nerve growth factor (NGF) has demonstrated encouraging electrophysiological and clinical results in a double-blind, placebo-controlled study. Traditional chemotherapy in patients with NF1-OPGs does not significantly ameliorate visual function, and its effectiveness in halting tumor growth cannot be considered a satisfactory result. Newer lines of research should be pursued with the goal of stabilizing or improving the vision, rather than reducing tumor volume. The growing understanding of the unique cellular and molecular characteristics of NF1-OPG, coupled with the recent publication of promising clinical studies, raise hope for a shift towards precision medicine and targeted therapies as a first-line treatment.

In vitro cell culture of amniotic fluid keratinocytes on amniotic membrane: the ideal tissue for repairing skin ulcers

OBJECTIVE

The amniotic fluid contains a large population of stem keratinocytes demonstrating minimal immunological rejection. Recent evidence suggests that stem cells from the amniotic fluid can be employed in the field of tissue engineering. In this work we identified precursors of the epithelial cells and expanded them in vitro.

MATERIALS AND METHODS

After collecting samples of amniotic fluid and separating the cells via centrifugation, we seeded a portion of these cells in selection media to analyze the proliferation of epithelial cells. The stem cells precursors of keratinocytes were identified through specific markers. The expression of these markers was evaluated by immunofluorescence and reverse transcription polymerase chain reaction (PCR).

RESULTS

The stem cells demonstrated 90% confluence, after undergoing proliferation in the selection medium for 15 days. Most of these cells tested positive for the keratinocyte-specific markers, but negative for stem cell specific markers. Of note, the identity of the keratinocytes was well established even after several subcultures.

CONCLUSIONS

These results suggested that it is feasible to isolate and expand differentiated cell populations in the amniotic fluid from precursor cells. Furthermore, amniotic membranes can be utilized as scaffolds to grow keratinocytes, which can be potentially exploited in areas of skin ulcer transplantation and tissue engineering interventions.

Taste, olfactory and texture related genes and food choices: implications on health status

OBJECTIVE

The food choices are due to a mixture of sensory signals including gustatory, olfactory, and texture sensations. The aim of this quality review was to update data about studies concerning genetics of taste, olfactory and texture receptors and their influence on the health status in humans.

MATERIALS AND METHODS

An electronic search was conducted in MEDLINE, Pubmed database and Scopus, for articles published in English until December 2018. Two independent researches selected the studies and extracted the data.

RESULTS

The review confirms the importance of inter-individual variations in taste, olfactory and texture related genes on food choices and their implications in the susceptibility to nutrition-related conditions such as obesity, dental caries, diabetes, cardiovascular disease, hypertension, hyperlipidemia and cancer.

CONCLUSIONS

The knowledge of variants in taste, olfactory and texture related genes can contribute to the prevention of diseases related to unhealthy nutrition. Further studies would be useful to identify other variants in the genes involved in these systems.

The value of multifocal electroretinography to predict progressive visual acuity loss in early AMD

BACKGROUND

To investigate, in a prospective study, the role of multifocal electroretinography (mfERG) for predicting visual acuity decline in early age-related macular degeneration (AMD) with time.

METHODS

Twenty-six early AMD patients (12 males and 14 females, mean age 66.9 ± 9.8; range 46-82 years) were included in the study. A complete ophthalmic examination and mfERG (Retiscan, Roland Germany, ISCEV standard protocol) were performed at the study entry (baseline), after 20 and 24 months. The first-order kernel mfERG responses were analyzed by ring analysis. The amplitude density (AD) of the first positive peak (P1, nV/deg(2)), the P1 amplitude (µV) and P1 implicit time (ms) for Rings 1 (central) to 6 (most peripheral) were evaluated. Data were statistically analyzed by analysis of variance and receiver operating characteristic (ROC) curves.

RESULTS

The loss in the mfERG Ring 1 AD from normal control values, recorded at baseline, was correlated with the decrease in ETDRS visual acuity with time (P = 0.004). ROC analysis showed that, after 24 months, the average decline in visual acuity was greater (3 letters vs 0.4 letters, P = 0.0021) in patients whose Ring 1 P1 AD at baseline was equal to or less than 65.9 nV/deg(2), compared to those with higher AD values. Both P1 amplitude and AD of Ring 1 had an area under the curve of 0.702 (95% confidence interval 0.50-0.92) with a sensitivity of 64.3% (35.14-87.24%) and a specificity of 91.7% (61.52-99.79%).

CONCLUSIONS

The present results indicate that mfERG P1 amplitude and AD of Ring 1 may be highly specific to predict visual acuity decline in early AMD.

[Clinic use of Laser Doppler Flowmetry (LDF) in the study of subfoveal choroidal circulation]

Today our knowledge of the choroidal circulation is limited: we know its anatomy, but, on the other hand, its physiopathology remains to be fully. The choroid is involved in a number of important ocular diseases. The Laser Doppler Flowmetry (LDF) is a technique that allows non-invasive measurement of haemodynamic parameters of the subfoveal choroidal circulation. It is easy to use in daily clinic activity. The aim of this mini-review is to describe LDF studies of the choroidal circulation performed in healthy subjects under different environmental conditions, in subjects with ocular diseases, as well as studies of the effects of various drugs can induce on this circulation.

The effects of hypoxia on the ERG in paediatric cerebral malaria

BACKGROUND/AIMS

Cerebral malaria (CM) is a disease of high mortality worldwide. It can be associated with malarial retinopathy (MR) resulting from impaired perfusion within the retinal microvasculature. Areas of capillary non-perfusion (CNP) appear white (retinal whitening) on ophthalmoloscopy. In this study, electrophysiological investigations were performed to investigate the physiological consequences of these hypoxic and ischaemic changes.

METHODS

Children admitted with CM were assessed for inclusion in the study. Those with MR underwent further detailed fundus assessment to quantify retinal whitening and were then designated a severity score. Electrophysiological recordings were performed using a miniganzfeldt stimulator with calibration to the International Society for Clinical Electrophysiology of Visual (ISCEV) standards. ERG data were then analysed with respect to presence of MR and also graded disease severity.

RESULTS

Thirty-one children were recruited with a diagnosis of CM, 20 had MR (group 1), and 11 had absent MR (group 2). Statistical analyses of these two groups showed a significant relationship between reduced single flash cone b wave amplitude (CBWA) and increased severity of retinal whitening/CNP (P<0.05). Cone and maximal response b : a wave ratios remained >1 in all subjects.

CONCLUSION

Retinal whitening/CNP in MR is associated with significant changes in ERG cone b wave function. The relatively high b : a ratio is compatible with the high frequency of MR resolution without sequelae.

Cytidine-5'-diphosphocholine (Citicoline): a pilot study in patients with non-arteritic ischaemic optic neuropathy

BACKGROUND AND PURPOSE

Our work evaluates visual function before and after treatment with cytidine-5-diphosphocholine (Citicoline) in patients with non-arteritic ischaemic optic neuropathy (NION).

METHODS

Twenty-six patients in which at least 6 months elapsed from NION, were randomly divided into two age-similar groups: 14 patients had Citicoline (Cebrolux-Tubilux, Italy, 1600 mg/diem for 60 days, followed by a 120-day period of wash out, days 60-180) (T-NION); 12 patients had no treatment during the same period (NT-NION). At day 180, in T-NION a second period of treatment (days 181-240) followed by a wash-out (days 241-360) was performed. Fourteen age-matched healthy subjects provided normative data. In all patients, pattern-electroretinogram (PERG), visual evoked potentials (VEPs) and visual acuity (VA) measurements were performed at baseline and at days 60 and 180. In T-NION, further measurements were achieved at days 240 and 360.

RESULTS

At baseline, NT-NION and T-NION patients showed abnormal PERGs and VEPs, and reduced VA, compared to controls. At the end of treatment (days 60 and 240), T-NION patients showed improvement (P < 0.01) of PERGs, VEPs parameters and VA, compared to pre-treatment values. After wash out, functional improvements persisted compared to baseline. No changes in NT-NION patients were observed.

CONCLUSIONS

Our results suggest a beneficial effect of oral Citicoline in NION.

Longitudinal assessment of childhood optic gliomas: Relationship between brain imaging and optic pathway function

2087

Background: To evaluate longitudinally the relationship between brain imaging and functional findings in childhood optic gliomas (OG) by comparing over time magnetic resonance imaging (MRI) with flicker visual evoked potential (FVEP) changes. Methods: Fourteen children (median age 3 yrs, range: 2–7) suffering from OGs involving chiasm and retro-chiasmatic visual pathways underwent serial MRI and FVEP examinations over a median follow-up time of 38 months (range 12–76). FVEPs were monocularly recorded in response to 8 Hz sine-wave flicker stimuli presented in a mini-Ganzfeld according to a published technique (Trisciuzzi et al., Clin. Neurophysiol., 2004). MRI examinations were performed according to standard procedures. Longitudinal results of both tests were examined in a blind fashion by independent evaluators. FVEPs were judged to be improved, stable or worsened if changes in the amplitude and/or phase of the fundamental response component exceeded the limits of test-retest variability (±90th percentile) established in the same patients. MRI results were judged to show regression, stabilization or progression of OG based on its changes in size (±20%) or extension. Two to seven pairs (< one month apart) of FVEP/MRI examinations per patient (median: 4, range 2–7) were collected. Agreement between test changes over time were evaluated by K-statistics. Results: Based on a total of 38 pairs of longitudinal FVEP/MRI examinations, both tests agreeed in showing worsening (progression), stabilization and improvement (regression) in 5, 10 and 15 cases, respectively. In 3 cases, FVEPs showed a worsening and MRI a stabilization, while in 5 cases FVEPs showed an improvement and MRI a stabilization. Agreement between FVEP and MRI changes was 78.9% (95% CI: ± 37%, K = 0.67, p < 0.001). Conclusions: The results indicate that changes over time in FVEPs, an objective and non-invasive test of visual function, can accurately predict associated changes in OG size and extension as assessed by MRI, and suggest that the latter changes may have a significant impact on visual function during developmental age.

No significant financial relationships to disclose.

Optical coherence tomography and focal electroretinogram evaluation of cystoid macular edema secondary to retinitis pigmentosa treated with intravitreal triamcinolone: case report

PURPOSE

To assess macular structure and function by optical coherence tomography (OCT) and focal electroretinogram (FERG) before and after intravitreal triamcinolone acetonide (IVTA) administration for cystoid macular edema (CME) in a patient with retinitis pigmentosa (RP).

METHODS

A 33-year-old man with RP and refractory bilateral macular edema was treated with IVTA in his left eye and evaluated with visual acuity, OCT, and FERG for 6 months. RESULTS. Compared to the fellow eye, after IVTA mean retinal thickness significantly decreased, while FERG amplitude and phase did not show significant changes at the end of follow-up. Visual acuity showed a significant tendency to improve.

CONCLUSIONS

In this case report, IVTA improved macular anatomy and visual acuity; this result, however, was not associated with a similar electrophysiologic response.

Molecular genetics of autosomal dominant retinitis pigmentosa (ADRP): a comprehensive study of 43 Italian families

Retinitis pigmentosa is the most common form of retinal degeneration and is heterogeneous both clinically and genetically. The autosomal dominant forms (ADRP) can be caused by mutations in 12 different genes. This report describes the first simultaneous mutation analysis of all the known ADRP genes in the same population, represented by 43 Italian families. This analysis allowed the identification of causative mutations in 12 of the families (28% of the total). Seven different mutations were identified, two of which are novel (458delC and 6901C-->T (P2301S), in the CRX and PRPF8 genes, respectively). Several novel polymorphisms leading to amino acid changes in the FSCN2, NRL, IMPDH1, and RP1 genes were also identified. Analysis of gene prevalences indicates that the relative involvement of the RHO and the RDS genes in the pathogenesis of ADRP is less in Italy than in US and UK populations. As causative mutations were not found in over 70% of the families analysed, this study suggests the presence of further novel genes or sequence elements involved in the pathogenesis of ADRP.

[Diet and management of degenerative diseases of the retina (retinitis pigmentosa)]

Considerable progress has been made in the understanding and management of degenerative diseases of the retina. The dietetic intervention has been favourably proposed in the most common forms of retinitis pigmentosa, a condition potentially leading to blindness. Vitamin A has been shown to be effective in delaying progression of the disease. In these patients such treatment is the only possible therapy, to date, and a lifetime generous supplementation of retinol is advisable, together with a vitamin A-rich diet and/or a dietary supplement (e.g. carrot flour) or pharmacologic supplement of vitamin A. Supply of vitamin A in doses up to 25000 IU (7500 igr/day), even for several years, has so far proved safe from risk of occurrence of liver disease. A possible effect on hypercholesterolemia related to a very prolonged treatment in predisposed individuals can be avoided by using a special diet, particularly enriched with beta-carotene. Guidelines for preparing a diet, specially formulated to provide an elevated weekly supply of vitamin and/or its precursor (equal to 15000 IU or 5000 microg of RE, retinol equivalent) and to control possible risk factors related to dietetic manipulation (supply of fat lower than 30% of total calories, variable levels of cholesterol and polyunsaturated fatty acids n-3, n-6) are presented. As long as resolutive therapy is lacking, dietetic intervention plays a primary role, although underestimated, in the management of the patients suffering from retinitis pigmentosa. The diet is specifically characterized by presence of food with a high content of carotenoids, substances with a favourable and additive effect.

Functionally rodless mice: transgenic models for the investigation of cone function in retinal disease and therapy

Two genetically engineered strains of mice were used to characterize murine cone function electroretinographically, without interference of rod-driven responses: (1) mice with a deletion of the gene for the rod transducin alpha-subunit (transducin alpha-/-), and (2) mice with rod arrestin deleted (arrestin -/-). In the first three months of age, both strains have a normal complement of rods and normal rod structure, but transducin alpha-/- mice have no rod-driven responses to light, while rod-driven activity of arrestin -/- mice can be suppressed by a single intense flash for hours. In response to intense flashes the electroretinograms of these strains of mice showed a readily identifiable, pure-cone a-wave of approximately 10 microV saturating amplitude. A 530 nm background that saturates rod responses of wild type mice was found to desensitize the b-wave responses of mice of both transgenic lines, whether the b-waves were driven by photons captured by M- or UV-cone pigments. The desensitizing effect of the 530 nm background on UV-pigment driven responses provides new evidence in support of the hypothesis of functional co-expression of the M-pigment in cones expressing primarily the UV-pigment.

Correlation of optic nerve head tomography with visual field sensitivity in papilledema

PURPOSE

To quantify the relationship between optic nerve head tomography and perimetric sensitivity in patients with papilledema.

METHODS

Eight patients with variable degrees of recently diagnosed papilledema associated with idiopathic intracranial hypertension (IIH) were evaluated with confocal scanning laser ophthalmoscopy (CSLO) and automated perimetry. Patients were followed up with serial measurements over a period of 5 to 30 months (mean +/- SD, 17.1 +/- 9), while under medical treatment (acetazolamide). The tomographic parameters, volume above reference (VAR), volume above surface (VAS), effective mean height (EMH), and maximum height in contour (MxHC), were obtained by tomography, either globally or from predefined disc sectors. The perimetric indices, mean deviation (MD) and pattern SD (PSD), were evaluated. The results from patients' right eyes and the individual intereye differences in both tomographic and perimetric parameters, were statistically evaluated by nonparametric correlational (Spearman) and repeated measures (Wilcoxon) analyses.

RESULTS

At baseline, all tomographic parameters were negatively correlated with MD in global (r = -0.8) and sectorial (r = -0.6) evaluations. The interocular differences in overall tomographic parameters were correlated with corresponding differences in perimetric MD (r = -0.8) and PSD (r = 0.6). During the follow-up period, volumetric disc parameters decreased (P < 0.02), whereas perimetric MD increased (P = 0.02) at comparable times.

CONCLUSIONS

In patients with recently diagnosed papilledema, optic nerve head tomographic abnormalities are quantitatively correlated with visual field sensitivity losses. Therapeutic improvement of volumetric parameters may be paralleled by recovery in perimetric sensitivity. The data support the possible use of both techniques in combination to monitor the amount of papilledema and the effectiveness of treatments designed to reduce intracranial hypertension.

[Effect of chromatic flicker on circulation of the optic nerve]

PURPOSE

To determine the response of human optic nerve head (ONH) blood flow (delta F) to heterochromatic equiluminant flicker modulation (eql-fl) and compare it to the response induced by pure luminance flicker (l-fl).

METHODS

In 5 normal volunteers the ONH blood flow was measured by conventional laser Doppler flowmetry. Stimuli were generated by green and red light emitting diodes and delivered to the eye through a fundus camera illumination optic. Both green and red illuminances were square wave modulated in counter phase at different frequencies between 2 and 40 Hz. delta F was defined as the ratio between the ONH blood flow after 1 min stimulation and a baseline blood flow measured prior to the stimulation.

RESULTS

In response to a 2 Hz eql-fl, ONH blood flow increases by 36% in average. delta F versus flicker frequency displayed the characteristics of a low-pass function with a cutoff frequency of 10 Hz for an eql-fl and a band-pass function with broad maximum around 10 Hz for the I-fl.

CONCLUSIONS

delta F in human ONH can be evoked by heterochromatic equiluminant flicker modulation. The blood flow frequency response to eql-fl and I-fl are similar to the neural activity dominated by the Parvo- and Magno-cellular activity, respectively. These findings offer a new approach to study the neurovascular coupling at the ONH in both physiological and diseased conditions involving predominantly or selectively the Magno- and Parvo-pathways.

Diagnosis and classification of macular degenerations: an approach based on retinal function testing

The results from literature concerning some aspects of retinal function in macular degenerations (MDs) were reviewed in order to evaluate whether (a) specific patterns of retinal dysfunction may be linked to different clinical phenotypes, and (b) distinct functional profiles may help in orienting molecular diagnosis of diseases. Examined clinical phenotypes included: Stargardt disease/fundus flavimaculatus (St/FF), age-related maculopathy (ARM) and macular degeneration (AMD), pattern dystrophies (PD), Best vitelliform dystrophy (BVD), Sorsby's fundus dystrophy (SFD), autosomal cone-rod dystrophies (CRD). The following functional tests were evaluated: (1) electroretinogram (ERG) (scotopic and photopic according to ISCEV standards, rod and cone photoresponses, rod and cone b-wave intensity-response function, focal ERGs); (2) dark adaptometry (pre-bleach sensitivity and post-bleach recovery kinetics); (3) fundus reflectometry (pigment density and regeneration kinetics). Specific patterns of retinal dysfunction were identified for St/FF, ARM/AMD, SFD and BVD, whereas partially overlapping profiles were found for PD and CRD. Specific functional patterns were associated with different peripherin/RDS gene mutations, as well as with CRX mutations. Combined analysis of different retinal function tests may help to identify different phenotypes of MD, and to orient molecular diagnosis for selected genotypes.

Flicker-evoked responses of human optic nerve head blood flow: luminance versus chromatic modulation

PURPOSE

To determine the response of human optic nerve head blood flow (R:F(onh)) to heterochromatic equiluminant flicker modulation and compare it to the response induced by pure luminance flicker.

METHODS

In five normal volunteers, F(onh) measured at the neuroretinal rim was monitored continuously by laser Doppler flowmetry. Stimuli were generated by green and red light emitting diodes and delivered to the fundus in Maxwellian view (field of 25(o)). Both green (G:) and red (R:) illuminances were square-wave modulated, 180(o) out of phase, with a maximum value of 10.4 for G: and 2.64 lux for R: Flicker frequency was varied from 2 Hz to 40 Hz. R:F(onh) was defined as the change in F(onh) during stimulation relative to the prestimulus F(onh).

RESULTS

Defining the color ratio r as R:/(R: + G:), the R:F(onh), measured for a 15-Hz flicker, was largest at pure luminance (r = 0 and 1), declined at mixed luminance and chromatic modulations, and reached a secondary maximum at r = 0.45, the value of psychophysical equiluminance. R:F(onh) versus flicker frequency displayed the characteristics of a low-pass function for the equiluminance flicker stimulus and of a band-pass function, with a maximum at intermediate frequencies, for the luminance flicker stimulus.

CONCLUSIONS

R:F(onh) in humans can be evoked by heterochromatic flicker, modulated either in luminance or chromatic equiluminant conditions. R:F(onh) may be specific for luminance and chromatic modulations, similar to neural responses dominated by the magno- and parvocellular activity, respectively. These findings offer a new approach to study the neurovascular coupling at the optic nerve head in both physiological and diseased conditions involving predominantly or selectively the magno- and parvocellular pathways.

Photopic negative response of the human ERG: losses associated with glaucomatous damage

PURPOSE

To evaluate in glaucomatous eyes the photopic electroretinogram (ERG) negative response (PhNR), a component that follows the b-wave peak and is thought to be correlated with inner retinal activity.

METHODS

Eleven patients with open-angle glaucoma (OAG) and moderate field loss (Humphrey 30-2 [Humphrey Instruments, San Leandro, CA] mean deviation < or = -6 dB), eight with ocular hypertension (OHT), and eight age-matched normal subjects were tested. Optic discs of patients and control subjects were evaluated by confocal scanning laser ophthalmoscopy. ERGs were recorded to long-duration stimuli (250 msec) of photopic luminance (78 candelas [cd] /m2), presented in the macular region (12 degrees x 12 degrees field size) on a steady, adapting background. Amplitudes of the a-wave and b-wave and the PhNR were measured. Pattern reversal ERGs to 30-minute checkerboards were also recorded from patients and control subjects.

RESULTS

Compared with control subjects, patients with OAG showed reduced PhNR (average reduction: 62%, P < 0.01), but normal a- and b-wave amplitudes. In patients with OHT, PhNR and a- and b-wave amplitudes did not differ from control values. In individual patients with OAG, PhNR amplitudes were correlated positively with pattern ERG amplitudes (r = 0.80; P < 0.01) and central (12 degrees) perimetric mean deviations (r = 0.68; P < 0.05) and negatively with cup-to-disc area ratios (r = -0.79; P < 0.01) and cup shape measures (r = -0.78; P < 0.01).

CONCLUSIONS

Similar to that found in monkeys with experimentally induced glaucoma, the PhNR is selectively altered in human glaucoma. The correlation between PhNR losses and clinical parameter abnormalities suggests that this component depends on inner retina integrity and may be of clinical value for detecting glaucomatous damage.

[Effect of dark adaptation on retinal blood flow]

PURPOSE

Laser Doppler measurements performed immediately after the transition from dark adaptation (DA) to light led to the hypothesis that retinal blood flow, Fret, is increased during DA, but the use of visible lasers had prevented measurements during DA. Our aim was to test this hypothesis by measuring Fret during and after DA.

MATERIAL AND METHODS

Fret in retinal vessels at the optic disk surface was recorded quasi-continuously in one eye of 6 normal subjects (age 27 to 60 years) using a laser Doppler flowmeter in the near-infrared (810 nm). Measurements were performed during light (baseline), various periods of DA and again during light. DA lasted between 2 and 32 min.

RESULTS

Average Fret for the 6 subjects did not change significantly (-2.7 +/- 8% sd, p > 0.05) during the various periods of DA, as determined from linear regressions of the flux versus time. Following the transition from DA to light, there was, in most cases, a rapid transient increase of the flux, which reached an average value of 37 +/- 10% above the pre-transition value and peaked at 30-60 sec after the transition.

CONCLUSIONS

These results do not support the hypothesis that Fret in normal volunteers is increased during DA. Rather, they strongly suggest that the transient increase in flux observed after DA is induced by the transition from dark to light (FNSRS #3200-043157 et CNR, It. #95.01715.CT04).

Retinal sensitivity to flicker modulation: reduced by early age-related maculopathy

PURPOSE

To evaluate retinal, cone-mediated flicker sensitivity (CFS) in age-related maculopathy (ARM) by quantifying response gain and threshold of the focal electroretinogram (FERG) to flicker modulation.

METHODS

Nineteen patients with ARM (visual acuity > or =20/30) and 11 age-matched control subjects were examined. Twelve patients had less than 20 soft drusen in the macular region and no hyper-/hypopigmentation (early lesion), whereas seven had more than 20 soft drusen and/or focal hyper-/hypopigmentation (advanced lesion). Macular (18 degree ) FERGs were elicited by a sinusoidally flickering (41 Hz) uniform field (on a light-adapting background) whose modulation depth was varied between 16.5% and 94%. Amplitude and phase of the response's fundamental harmonic were measured.

RESULTS

In both control subjects and patients with ARM, log FERG amplitude increased with log stimulus modulation depth with a straight line (power law) relation. However, the slope (or gain) of the function was, on average, steeper in control subjects than in patients with either early or advanced lesions. Mean FERG threshold, estimated from the value of the log modulation depth that yielded a criterion response, did not differ between control subjects and patients with early lesions but was increased (0.35 log units) compared with control subjects in those with advanced lesions. In both patient groups, but not in control subjects, mean FERG phase tended to delay with decreasing stimulus modulation depth.

CONCLUSIONS

Retinal CFS losses can be detected in ARM by evaluating the FERG as a function of flicker modulation depth. Reduced response gain and phase delays, with normal thresholds, are associated with early lesions. Increased response thresholds, in addition to gain and phase abnormalities, may reflect more advanced lesions. Evaluating CFS by FERG may directly document different stages of macular dysfunction in ARM.

The fundamental and second harmonic of the photopic flicker electroretinogram: temporal frequency-dependent abnormalities in retinitis pigmentosa

OBJECTIVES

The flicker electroretinogram (FERG) consists mainly of a linear (fundamental, 1F) and a non linear (second harmonic, 2F) component. Previous results indicate that 2F originates more proximally in the retina than 1F, and that retinitis pigmentosa (RP) may affect 2F to a greater extent than 1F. The aim of this study was to evaluate FERG 1F and 2F abnormalities in RP as a function of the stimulus temporal frequency (TF).

METHODS

Twelve patients with typical RP and 10 age-matched controls were examined. FERGs were recorded in response to uniform fields (18 degrees) presented in the macula on a light-adapting background. Stimuli were flickered sinusoidally at different, closely spaced TFs between 3.7 and 52 Hz. Amplitudes and phases of the Fourier analysed 1F and 2F components were measured. Components' apparent latencies were estimated from the rate at which phase lagged with TF.

RESULTS

When compared to controls, mean 1F amplitudes of patients were reduced at both low (3.7-12.6 Hz) and high (14-52 Hz) TFs, with greatest losses (0.5 log units) around the peaks (3.7 and 41 Hz) of the normal TF function. Mean 2F amplitudes were reduced mainly at low TFs, with greatest losses (0.5 log units) at 5-8 Hz. On average, the shape of the 2F, but not 1F amplitude versus TF function, differed between patients and controls, showing a selective attenuation at low TFs. Mean 1F apparent latencies were delayed at both low and high TFs, with greater delays at low (85 ms) than at high (33 ms) TFs. Mean 2F apparent latencies were delayed only at low TFs (58 ms).

CONCLUSIONS

In RP, 1F and 2F phase delays as well as 2F amplitude losses are dependent on TF, suggesting that FERG generators' subpopulations in both distal and proximal retina are differentially affected. Analysis of the FERG TF response is potentially useful to characterize cone system dysfunction in different genetic subtypes of RP.

Correlation of pattern electroretinogram with optic disc cup shape in ocular hypertension

PURPOSE

To evaluate the correlation of pattern electroretinogram (PERG), an index of inner retinal function, with confocal scanning laser (CSLO) optic disc structural parameters in ocular hypertension (OHT).

METHODS

Thirty-four patients with OHT, normal white-on-white (Humphrey 30-2) perimetry, and normal clinical optic discs were examined with PERG and CSLO disc analysis. Two groups of normal subjects (n = 38 and 18, for PERG and CSLO, respectively) and a group of 12 patients with early open-angle glaucoma (EOAG) were also tested. Pattern electroretinogram amplitudes were measured in response to sinusoidal gratings of variable spatial frequency (0.58-5.8 cycles/degree), modulated in counter-phase at 7.5 Hz. Morphometric optic disc parameters were obtained by the Heidelberg Retina Tomograph (HRT), either globally or from predefined disc sectors. In addition to standard parameters, the cup shape measure, an index of depth variation and steepness of the cup walls, was determined.

RESULTS

In individual OHT patients, PERG amplitudes at 2.6 cycles/degree were negatively correlated with cup shape measures (r = -0.43, P < 0.01) obtained from analysis of the inferotemporal (IT) sector. No significant correlations were found for the other parameters. On average, the cup shape measures derived from IT sector or global analysis were significantly (P < 0.01) worse, and closer to the measures of EOAG patients, in OHT patients with abnormal PERG compared with those with normal PERGs. The cup shape measure displayed a low sensitivity (20%) and a high specificity (100%) in predicting PERG abnormalities in individual OHT patients.

CONCLUSIONS

The results indicate that in OHT there is a significant although weak correlation between PERG amplitude and the shape of the optic disc cup, suggesting a parallel involvement of both function and morphology. Combined PERG and optic disc cup structural analysis is of potential diagnostic value to detect early damage to optic nerve head in individual OHT patients.

Retinal ganglion cell dysfunction in humans following post-geniculate lesions: specific spatio-temporal losses revealed by pattern ERG

Nasal and temporal hemifield (14 x 24 degrees) pattern electroretinograms (PERGs) were recorded in eight patients (age range: 21-72 years) suffering from different post-geniculate lesions (documented by CT scan and/or MRI of the brain) and homonymous hemianopia at visual field testing. In total eight age-matched normal subjects served as controls. PERGs were elicited by alternating, sinusoidal gratings (90% contrast), whose spatial and temporal characteristics, 6 Hz-5 c deg-1 and 15 Hz-0.58 c deg-1, were chosen to enhance the relative contributions of parvo- (P) and magno- (M) retinal ganglion cell (GC) subsystems, respectively. Amplitudes and phases of the Fourier analyzed PERG 2nd harmonics were measured. In normal subjects, PERG amplitudes to 15 Hz-0.58 c deg-1, but not those of the 6 Hz-5 c deg-1 stimuli were on average larger (P < 0.05) in nasal than in temporal hemiretinae. In hemianopic patients, PERG amplitudes of 6 Hz-5 c deg-1 stimuli were on average reduced (P < 0.05) in the hemiretinae corresponding to blind hemifields, in comparison to those in the hemiretinae corresponding to functional hemifields. No differences between hemiretinae were observed for responses of the 15 Hz-0.58 c deg-1 stimuli. In both normal subjects and patients, average PERG phases did not differ between hemiretinae, while changing significantly (P < 0.01) across stimulus conditions. The PERG naso-temporal asymmetries observed in normal subjects are consistent with the reported asymmetries in GC density observed histologically (Curcio & Allen. (1990). Journal of Comparative Neurology, 300, 5-25). The results in patients indicate that the PERGs to specific spatio-temporal stimuli (i.e. of relatively low-temporal and high-spatial frequency), presented in the hemianopic field, are reduced in amplitude. This suggests, in agreement with the experimental findings in monkeys (Cowey & Stoerig. (1991). Trends in Neuroscience, 14, 140-145), that retrograde trans-synaptic dysfunction of P-GCs, with relative sparing of the M-subsystem, may occur in humans following lesions of post-geniculate pathways.

Focal electroretinograms and fundus appearance in nonexudative age-related macular degeneration. Quantitative relationship between retinal morphology and function

BACKGROUND

The aim of this study was to evaluate the focal electroretinogram (FERG), an objective indicator of outer retinal function, in nonexudative age-related macular degeneration (NE-AMD), and to compare FERG results with morphological lesions assessed by stereoscopic fundus photographs and fluorescein angiograms.

METHODS

Twenty-five patients (25 eyes) with bilateral NE-AMD (visual acuity of the study eyes > or = 0.4) as well as 10 age- and sex-matched control subjects (10 eyes) were evaluated. FERGs were recorded from the macular region (9 degrees) in response to sinusoidal stimuli flickered at 32 Hz. Amplitude and phase angle of the Fourier-analyzed FERG fundamental component were measured. Fundus lesions were graded from color slides according to the Wisconsin age-related maculopathy grading system . Fluorescein angiograms were evaluated by an image analysis technique to compute the area with pathological hyperfluorescence (associated with drusen and/or retinal pigment epithelial atrophy) within the macular (approximately 9 degrees x 9 degrees) region.

RESULTS

Compared to control eyes, NE-AMD eyes had a reduction in the mean FERG amplitude (57% loss, P<0.001) with no phase changes. Amplitudes of individual affected eyes were negatively correlated with either the Wisconsin grading score (r = -0.63, P < 0.001) or the percentage area of pathological hyperfluorescence (r = -0.70, P<0.01). Eyes with minimal NE-AMD lesions (Wisconsin score < or = 6) and normal acuity had a lower mean amplitude (47% loss, P < 0.05) than that of control eyes.

CONCLUSIONS

The results indicate that, in NE-AMD, the FERG is altered in parallel with the extent and severity of fundus lesions. However, a functional impairment of outer macular layers, which is detected by FERG losses, could precede morphological changes typical of more advanced disease.

The spatial tuning of steady state pattern electroretinogram in multiple sclerosis

In normal subjects, the steady-state electroretinogram in response to contrast reversing gratings (PERG), is spatially band-pass tuned in amplitude, with a maximum at intermediate spatial frequencies and an attenuation at lower and higher ones. The amplitude attenuation at low spatial frequencies is believed to reflect centre-surround antagonistic interactions in the receptive fields of inner retinal neurons. The aim of this study was to evaluate the PERG spatial tuning in multiple sclerosis (MS) patients without a previous optic neuritis history. Steady- state PERGs in response to counterphase-modulated (8 Hz) sinusoidal gratings of variable spatial frequency (0.6, 1.0, 1.4, 2.2 and 4.8 c/deg), were recorded from 18 patients with definite or probable MS and no history of optic neuritis (ON-). Nine of them had no signs of subclinical optic nerve demyelination (asymptomatic) in either eye, while nine had symptoms or signs of optic pathways involvement (symptomatic) in one or both eyes. Results were compared with those obtained from 10 MS patients with a previous history of optic neuritis (ON+) in one or both eyes, as well as from 21 age-matched controls. The amplitudes and phases of the responses' 2nd harmonics were measured. Compared with the controls, asymptomatic ON- patients showed selective losses in mean PERG amplitudes at medium and high (1.0-4.8 c/deg) spatial frequencies. Symptomatic ON- patients and ON+ patients had reductions in mean PERG amplitudes, with respect to controls, involving the whole spatial frequency range, but with greater losses at medium-high (1.0-4.8 c/deg) than at lower spatial frequencies. In all patients' groups, the average PERG spatial tuning function differed significantly from that of the controls, assuming a low-pass instead of the normal band-pass shape. The PERG phase was delayed in ON+ but not in ON- patients, as compared to controls. However, the phase delay was independent of spatial frequency. In both ON- and ON+ patients, losses in PERG amplitude and spatial tuning tended to be associated with corresponding abnormalities in perimetric sensitivity, visual acuity, colour vision and transient visual evoked potential (VEP) latency. The results indicate that abnormalities of the spatial tuning of steady-state PERG can be found in MS patients without either optic neuritis or signs of subclinical optic nerve demyelination. These changes may reflect a retinal dysfunction, developing early in the course of MS, due to a loss of specific subpopulations of inner neurons, changes in lateral interactions of their receptive fields, or both.

Pattern electroretinogram and optic nerve topography in ocular hypertension

It is known that changes in pattern electroretinogram (PERG) and optic disk morphology may both precede the onset of visual field damage in glaucomatous disease. However, the relationship between PERG and optic disk morphometry in ocular hypertension (OHT) has not yet been evaluated in detail. This study of PERG amplitude in a group of OHT patients indicates its significant correlation with various optic disk morphometric parameters, in particular, those of optic disk sectors considered at risk for early glaucomatous damage. Analysis of individual data points to the possibility that, while functional abnormalities may often precede optic disk morphologic changes, in a much lower number of cases it seems to be the other way around.

UV- and midwave-sensitive cone-driven retinal responses of the mouse: a possible phenotype for coexpression of cone photopigments

Molecular biological, histological and flicker electroretinographic results have established that mice have two cone photopigments, one peaking near 350 nm (UV-cone pigment) and a second near 510 nm [midwave (M)-cone pigment]. The goal of this investigation was to measure the action spectra and absolute sensitivities of the UV-cone- and M-cone-driven b-wave responses of C57BL/6 mice. To achieve this goal, we suppressed rod-driven signals with steady or flashed backgrounds and obtained intensity-response relations for cone-driven b-waves elicited by narrowband flashes between 340 and 600 nm. The derived cone action spectra can be described as retinal1 pigments with peaks at 355 and 508 nm. The UV peak had an absolute sensitivity of approximately 8 nV/(photon microm2) at the cornea, approximately fourfold higher than the M peak. In an attempt to isolate UV-cone-driven responses, it was discovered that an orange conditioning flash (lambda > 530 nm) completely suppressed ERG signals driven by both M pigment- and UV pigment-containing cones. Analysis showed that the orange flash could not have produced a detectable response in the UV-cone pathway were their no linkage between M pigment- and UV pigment-generated signals. Because cones containing predominantly the UV and M pigments have been shown to be located largely in separate parts of the mouse retina (), the most probable linkage is coexpression of M pigment in cones primarily expressing UV pigment. New histological evidence supports this interpretation (). Our data are consistent with an upper bound of approximately 3% coexpression of M pigment in the cones that express mostly the UV pigment.

Electrophysiological evaluation of the macular cone system: focal electroretinography and visual evoked potentials after photostress

In this article, the methodologies and clinical applications of two electrophysiological tests, the focal electroretinogram (FERG) and the visual evoked potentials (VEPs) after photostress, are described. These techniques provide somewhat complementary results about macular function because they tap the activity of different neural substrates along the pathway of the cone system and allow evaluation of the macular function under steady-state (ie, the FERG) or dynamic (ie, the VEPs after photostress) conditions. The results obtained in patients with different macular pathologies indicate that while the FERG provides direct information about the extent and sites of macular dysfunction, the VEPs after photostress represent an objective, although not specific, index of the dynamic properties of macular performance after exposure to intense light stimulation. The combined use of both techniques appears to be promising for gaining further insights into the diagnosis and pathophysiology of macular diseases.

Precision LED-based stimulator for focal electroretinography

The authors discuss the technical problems commonly encountered in the design of devices used in the functional analysis of the central retina (macula) and its neuronal elements. They present a simple effective solution for introducing some of the most recent and interesting results of neurophysiological and psychophysical research into the eye clinic.

The pattern electroretinogram (PERG) after laser treatment of the peripheral or central retina

PURPOSE

To understand whether laser photocoagulation of the retina for the treatment of diabetic retinopathy (DR) alters directly or indirectly the function of the macular region.

METHODS

Transient pattern electroretinograms (PERGs) to 30' checks have been recorded in DR patients before and 7-10 days after one treatment session (established protocol with Argon laser) of either the peripheral retina (panretinal treatment) or the central retina (paramacular focal treatment).

RESULTS

Treatment of the peripheral retina causes, in most eyes, a small increase (about 15% on average) of the PERG amplitude. Focal paramacular treatment causes a marked decrement (about 40% on average) of the PERG amplitude. Simulated retinal amputation induced by focal treatment, obtained by means of adequate stimulus masking, resulted in a 15-20% PERG decrement only.

CONCLUSIONS

The PERG increase after peripheral treatment may be due to rearrangement of both retinal and choroideal hemodynamics and does not necessarily result in useful long term changes. The PERG decrease after focal, paramacular treatment is far larger than that expected on the basis of the amputated area only. This may result from thermal and/or toxic damaging effects spreading outside the treated area. The results are relevant for both a better monitoring of central retinal function in the course of laser treatment and a better evaluation of the cost/benefit ratio after photocoagulation in DR.

Transiently raised intraocular pressure reveals pattern electroretinogram losses in ocular hypertension

PURPOSE

It is known that the pattern electroretinogram (PERG) of normal subjects is reduced temporarily after short-term elevation of intraocular pressure (IOP). The authors evaluated PERG changes in ocular hypertension during and after transient IOP elevation.

METHODS

Steady state (8 Hz) PERGs to sinusoidal gratings (1.7 cyc/deg spatial frequency) were recorded in seven untreated patients with ocular hypertension at medium risk (maximum IOP, 22 to 25 mm Hg; cup-disk ratio, 0.6 to 0.7; normal Humphrey 30-2 visual field results; positive family history), as well as in six age-matched normal subjects. Recordings were obtained for the baseline condition during a short-term (6-minute) IOP elevation (to 30 mm Hg) by using a suction cup apparatus and during a 6-minute recovery period after removal of the apparatus.

RESULTS

During IOP elevation, PERG amplitudes were reduced significantly from baseline values in normal subjects and patients. However, PERG losses were significantly greater in patients (average loss from baseline after 4 minutes of IOP elevation: 72% +/- 7.6%) compared to controls (average loss after 2 minutes of IOP elevation: 40% +/- 7.5%). In the recovery phase, mean PERG amplitude returned to baseline values in normal subjects but not in patients, whose recovery took longer. In normal subjects, PERG phase did not change either during or after IOP elevation. In patients, however, PERG phase showed a delay from baseline during and after IOP elevation (average delay after 6 minutes of recovery: -41.1 degrees +/- 13 degrees).

CONCLUSIONS

Results indicate that increasing IOP with scleral suction produces greater PERG losses in eyes with ocular hypertension than in normal eyes. This suggests that the inner retina of eyes with ocular hypertension may have a heightened sensitivity to vascular or mechanical changes induced by transient IOP elevation.

The temporal frequency response function of pattern ERG and VEP: changes in optic neuritis

Steady-state pattern electroretinograms (PERGs) and visual evoked potentials (VEPs) in response to sinusoidal gratings (2 c/deg), sinusoidally counterphased at closely spaced temporal frequencies (TFs) between 4 and 28 Hz, were recorded from 11 patients with unilateral optic neuritis (ON; 11 affected eyes and 10 healthy fellow eyes) and 7 age-matched normal subjects (7 eyes). Amplitude and phase of responses' second harmonics were measured. Responses' apparent latencies were estimated from the rate at which phase lagged with TF. When compared to control values, mean PERG and VEP amplitudes of ON eyes were reduced (by about 0.4 log units) at both low (5-10 Hz) and high (16-20 Hz) TFs. Mean PERG amplitudes of fellow eyes were selectively reduced at low TFs (by about 0.3 log units). Mean PERG apparent latencies of both ON and fellow eyes were delayed (by 15 and 9 ms, respectively). Mean VEP apparent latency of ON eyes was delayed at both low and high TFs (by 24 and 30 ms, respectively), while that of fellow eyes was selectively delayed at high TFs (by 28 ms). The results in ON eyes indicate non-selective abnormalities of PERG and VEP generators responding at both low and high TFs. VEP TF losses may be in part accounted for by corresponding PERG losses. In the fellow eyes of patients, more selective PERG and VEP TF abnormalities may suggest differential impairment of retinal and postretinal subsystems responding better to low and high TFs (i.e. parvo- and magnocellular streams).

Optic nerve diameters and perimetric thresholds in idiopathic intracranial hypertension

AIMS/BACKGROUND

Idiopathic intracranial hypertension (IIH) is a central nervous disorder characterised by abnormally increased cerebrospinal fluid (CSF) pressure leading to optic nerve compression. An indirect estimate of increased CSF pressure can be obtained by the ultrasonographic determination of optic nerve sheaths diameters. Computerised static perimetry is regarded as the method of choice for monitoring the course of the optic neuropathy in IIH. The aims were to compare the echographic optic nerve diameters (ONDs) and the perimetric thresholds of patients with IIH with those of age-matched controls, and to examine the correlation between these two variables in individual patients with papilloedema.

METHODS

Standardised A-scan echography of the mid orbital optic nerve transverse diameters and automated threshold perimetry (Humphrey 30-2) were performed in 20 patients with IIH with variable degree of papilloedema (according to the Frisén scheme) and no concomitant ocular diseases. Echographic and perimetric results were compared with those obtained from 20 age-matched controls.

RESULTS

When compared with controls, patients with IIH showed a significant increase in mean ONDs and significantly reduced mean perimetric sensitivities. In individual patients with papilloedema, the transverse ONDs correlated negatively with Humphrey mean deviation values and positively with pattern standard deviation values.

CONCLUSION

These results indicate that OND changes in IIH are associated with perimetric threshold losses, and suggest that IIH functional deficits may be related to the degree of distension of optic nerve sheaths as a result of an increased CSF pressure.

Macular flicker electroretinograms in Best vitelliform dystrophy

PURPOSE

The aim of this study was to evaluate the function of the neurosensory retina in Best vitelliform macular dystrophy (BMD) by recording the focal electroretinogram (ERG) fundamental and 2nd harmonic components, which are known to be dominated by receptoral and postreceptoral activity, respectively.

METHODS

FERGs were recorded in response to a uniform field (9 x 9 deg) flickered sinusoidally at either 8 Hz or 32 Hz (peak frequencies for the 2nd and fundamental harmonic, respectively). The fundamental component of the response to the 32-Hz stimulus and the 2nd harmonic of the response to the 8-Hz stimulus were measured in their amplitudes and phases. The fundamental-2nd harmonic amplitude ratio was taken as an index of the relative changes in the FERG components. Eleven patients with BMD and vitelliform stage macular lesions were evaluated. Results were compared with those obtained from 13 patients with Type 2 Stargardt macular dystrophy (STD) according to the Noble and Carr Classification, and 29 normal control subjects. Four BMD and four STD patients were also followed electrophysiologically over a 48 month period.

RESULTS

Compared to controls, BMD patients showed losses of both FERG fundamental and 2nd harmonic amplitudes, and an increase in the fundamental and increase in the fundamental-2nd harmonic ratio. STD patients also showed losses of both fundamental and 2nd harmonic, but the fundamental-2nd harmonic ratio was normal. In BMD patients, but not in those with STD, the fundamental amplitude tended to decrease over the follow-up period.

CONCLUSIONS

The results indicate that BMD involves neurosensory abnormalities early in the disease process. The increased fundamental-2nd harmonic ratio suggests that a postreceptoral dysfunction may be present in addition to that of photoreceptors. This differs from STD, where losses appear to affect primarily the receptoral retina. Receptoral losses in BMD may progress throughout the medium-term follow up.

[Wolfram syndrome. Personal experience]

We report on a young patient who suffered from diabetes mellitus and neurosensorial deafness from the age of two. One year later she was noted to have deteriorated vision and the diagnosis of optic atrophy was made, her visual acuity decreased progressively. At the age of six she was admitted to our hospital because of thiamine responsive megaloblastic anemia, a rare clinical feature of Wolfram's syndrome (only 13 cases have been reported to date). Thiamine (75 mg/day) was commenced at a single oral dose with a rapid increase of Hb level after a few days of therapy. The insulin requirement didn't decrease during thiamine therapy, the C-peptide level after glucagon remained almost indosable. No improvement was observed in the deafness and in the optic atrophy. These findings suggest that diabetes mellitus and optic atrophy, in Wolfram's syndrome are not related to thiamine metabolism.

Spatial-temporal interactions in the steady-state pattern electroretinogram

It is currently assumed that steady-state pattern electroretinograms can be obtained only at high rates of pattern reversal. However, steady-state responses can also be obtained at very low temporal frequencies (less than 1 Hz), provided that the reversal is sinusoidal. In five healthy volunteers, we studied the frequency characteristics of the pattern-reversal electroretinogram in response to sinusoidal gratings of 0.4 and 4 c/deg, reversed sinusoidally in contrast at frequencies ranging from 1 to 27 Hz. Steady-state responses dominated by the second harmonic component were obtained at all temporal frequencies tested; the amplitude of the second harmonic changed with stimulus temporal frequency. In the low-temporal-frequency range, stimuli of high spatial frequency appear to elicit larger contribution of generators with sustained or tonic characteristics compared with stimuli of low spatial frequency.

Detection of glaucomatous damage in patients with osteo-odontokeratoprosthesis

BACKGROUND

Osteo-odontokeratoprosthesis (OOKP) is an autologous transplantation procedure in which the cornea is replaced by an optical cylinder glued to a biological support. Patients undergoing OOKP surgery may develop a secondary glaucoma whose diagnosis, by means of standard diagnostic procedures, is often doubtful.

METHODS

In the present study pattern electroretinograms (PERGs), visual evoked potentials (VEPs), contrast sensitivity, and automated threshold perimetry (Humphrey 30-2) were evaluated in 19 OOKP treated patients with postoperative visual acuities > or = 0.8. Nine patients had had a preoperative secondary glaucoma, while the remaining 10 had no history of glaucoma and normal posterior pole.

RESULTS

Results were compared with those obtained from either normal control subjects or from ordinary glaucoma patients. PERG amplitudes and contrast and perimetric sensitivities were reduced in both groups of OOKP patients when compared with normal controls. However, these losses were significantly greater in OOKP patients with glaucoma compared with those with normal posterior pole. VEPs were reduced, compared with controls, only in OOKP patients with glaucoma. These VEP losses were similar to those found in ordinary glaucoma patients.

CONCLUSION

Among the tests employed, VEPs showed the best accuracy (79%) in discriminating between glaucomatous and non-glaucomatous OOKP treated eyes. The present results suggest a possible use of the VEP technique for detecting glaucomatous dysfunction after OOKP.

The first and second harmonics of the macular flicker electroretinogram: differential effects of retinal diseases

We evaluated the effects of retinal diseases on the macular electroretinogram first and second harmonic components, which are dominated by outer and inner retinal activity, respectively. Macular electroretinograms in response to a uniform field (9 degrees x 9 degrees) flickering sinusoidally at either 32 or 8 Hz (peak frequencies of the first and second harmonics, respectively) were recorded in 14 patients with maculopathies involving photoreceptors (e.g., age-related macular degeneration), in 16 patients with postreceptoral macular diseases (e.g., branch occlusion of central retinal artery), and in 38 normal controls. Amplitude and phase of the first and second harmonic response components were evaluated by Fourier analysis. When compared to controls, patients with photoreceptor diseases had reduction in both first and second harmonic mean amplitudes and second harmonic phase delay; patients with postreceptoral diseases had normal first harmonic components but reduced and delayed second harmonic components. A discriminant analysis, by using first and second harmonic values, correctly classified 13 of 14 patients with photoreceptor diseases and 14 of 16 patients with postreceptoral disorders. These results indicate that combined evaluation of the macular electroretinogram first and second harmonic components is a useful test for identifying the site(s) of retinal dysfunction in patients with macular diseases.