Statistical Evaluation of ERG Responses: A New Method to Validate Cycle-by-Cycle Recordings in Advanced Retinal Degenerations.

Purpose: To describe and evaluate a novel method to determine the validity of measurements made using cycle-by-cycle (CxC) recording techniques in patients with advanced retinal degenerations (RD) having low-amplitude flicker electroretinogram (ERG) responses. Methods: The method extends the original CxC recording algorithm introduced by Sieving et al., retaining the original recording setup and the preliminary analysis of raw data. Novel features include extended use of spectrum analysis, reduction of errors due to known sources, and a comprehensive statistical assessment using three different tests. The method was applied to ERG recordings from seven patients with RD and two patients with CNGB3 achromatopsia. Results: The method was implemented as a Windows application to processes raw data obtained from a commercial ERG system, and it features a computational toolkit for statistical assessment of ERG recordings with amplitudes as low as 1 µV, commonly found in advanced RD patients. When recorded using conditions specific for eliciting cone responses, none of the CNGB3 patients had a CxC validated response, indicating that no signal artifacts were present with our recording conditions. A comparison of the presented method with conventional 30 Hz ERG was performed. Bland-Altman plots indicated good agreement (mean difference, -0.045 µV; limits of agreement, 0.193 to -0.282 µV) between the resulting amplitudes. Within-session test-retest variability was 15%, comparing favorably to the variability of standard ERG amplitudes. Conclusions: This novel method extracts highly reliable clinical recordings of low-amplitude flicker ERGs and effectively detects artifactual responses. It has potential value both as a cone outcome variable and planning tool in clinical trials on natural history and treatment of advanced RDs.

COVID-19 in Africa: the little we know and the lot we ignore.

COVID has stirred up an information deluge that challenges our capacity to absorb and make sense of data. In this unrelenting flow of information, Africa has been largely off the radar, escaping the attention of the scientific literature and the media. International agencies have been the exception: despite the still low numbers of cases and deaths, they have voiced concerns, often in catastrophic terms, on the health, economic and social impacts of COVID in African countries. These concerns contrast sharply with the optimistic view that Africa may be spared the worst consequences of the pandemic.This paper provides a snapshot of a crisis in evolution: its features could change as new data become available and our understanding improves. The paper examines the epidemic trends, the health impact, the containment measures and their possible side effects. Africa has a long experience of responding to epidemics: relevant lessons learned are outlined. The picture of the epidemic and its narrative are heterogenous, given the differing vulnerabilities of African countries and the diverse contexts within their borders. The paper, therefore, singles out selected countries as illustrative of specific situations and advocates for a transnational and subnational approach to future analyses.The virus has shown a strong capacity to adapt; therefore, a response strategy, in order to be effective, needs to be flexible and able to adapt to changes. The paper concludes with the recommendation that affected communities should be engaged in the response, to maintain or build trust. A lesson from the Ebola outbreak of a few years ago was that epidemiologists and community leaders learned, after initial difficulties, how to dialogue and work together.A summary update of the pandemic has been added, in view of its fast evolution.

Antioxidant Saffron and Central Retinal Function in ABCA4-Related Stargardt Macular Dystrophy.

Retinal oxidative damage, associated with an ATP-binding cassette, sub-family A, member 4, also known as ABCA4 gene mutation, has been implicated as a major underlying mechanism for Stargardt disease/fundus flavimaculatus (STG/FF). Recent findings indicate that saffron carotenoid constituents crocins and crocetin may counteract retinal oxidative damage, inflammation and protect retinal cells from apoptosis. This pilot study aimed to evaluate central retinal function following saffron supplementation in STG/FF patients carrying ABCA4 mutations. METHODS: in a randomized, double-blind, placebo-controlled study (clinicaltrials.gov: NCT01278277), 31 patients with ABCA4-related STG/FF and a visual acuity >0.25 were randomly assigned to assume oral saffron (20 mg) or placebo over a six month period and then reverted to P or S for a further six month period. Full ophthalmic examinations, as well as central 18° focal electroretinogram (fERG) recordings, were performed at baseline and after six months of either saffron or placebo. The fERG fundamental harmonic component was isolated by Fourier analysis. Main outcome measures were fERG amplitude (in µV) and phase (in degrees). The secondary outcome measure was visual acuity. RESULTS: supplement was well tolerated by all patients throughout follow-up. After saffron, fERG amplitude was unchanged; after placebo, amplitude tended to decrease from baseline (mean change: -0.18 log µV, p < 0.05). Reverting the treatments, amplitude did not change significantly. fERG phase and visual acuity were unchanged throughout follow-up. CONCLUSIONS: short-term saffron supplementation was well tolerated and had no detrimental effects on the electroretinographic responses of the central retina and visual acuity. The current findings warrant further long-term clinical trials to assess the efficacy of saffron supplementation in slowing down the progression of central retinal dysfunction in ABCA4-related STG/FF.

Understanding Seasonal Changes to Improve Good Practices in Livestock Management.

Background and Aim: Food quality control techniques based on process control methods are increasingly adopted in livestock production systems to fulfill increasing market's expectations toward competitiveness and issues linked to One Health pillars (environment, animal, and human health). Control Charts allow monitoring and systematic investigation of sources of variability in dairy production parameters. These parameters, however, may be affected by seasonal variations that render impractical, biased or ineffective the use statistical control charts. A possible approach to this problem is to adapt seasonal adjustment methods used for the analysis of economic and demographic seasonal time series. The aim of the present work is to evaluate a seasonal decomposition technique called X-11 on milk parameters routinely collected also in small farms (fat, protein, and lactose content, solids-not-fat, freezing point, somatic cell count, total bacterial count) and to test the efficacy of different seasonal removal methods to improve the effectiveness of statistical control charting. Method: Data collection was carried out for 3 years on routinely monitored bulk tank milk parameters of a small farm. Seasonality presence was statistically assessed on milk parameters and, for those parameters showing seasonality, control charts for individuals were applied on raw data, on X-11 seasonally adjusted data, and on data smoothed with a symmetric moving average filter. Correlation of seasonally influenced parameters with daily mean temperature was investigated. Results: Presence of seasonality in milk parameters was statistically assessed for fat, protein, and solids-non-fat components. The X-11 seasonally-adjusted control charts showed a reduced number of violations (false alarms) with respect to non-seasonally adjusted control chart (from 5 to 1 violation for fat, from 17 to 1 violation for protein, and from 9 to none violation for solids-non-fat.). This result was achieved despite stricter control chart limits: with respect to raw data charts, the interval of control chart allowed variation (UCL-LCL) was reduced by 43% for fat, by 33.1% for protein, and by 14.3% for solids-not-fat. Conclusions: X-11 deseasonalization of routinely collected milk parameters was found to be an effective method to improve control chart application effectiveness in farms and milk collecting centers.

Bilateral Symmetry of Visual Function Loss in Cone-Rod Dystrophies.

PURPOSE: To investigate bilateral symmetry of visual impairment in cone-rod dystrophy (CRD) patients and understand the feasibility of clinical trial designs treating one eye and using the untreated eye as an internal control. METHODS: This was a retrospective study of visual function loss measures in 436 CRD patients followed at the Ophthalmology Department of the Catholic University in Rome. Clinical measures considered were best-corrected visual acuity, focal macular cone electroretinogram (fERG), and Ganzfeld cone-mediated and rod-mediated electroretinograms. Interocular agreement in each of these clinical indexes was assessed by t- and Wilcoxon tests for paired samples, structural (Deming) regression analysis, and intraclass correlation. Baseline and follow-up measures were analyzed. A separate analysis was performed on the subset of 61 CRD patients carrying likely disease-causing mutations in the ABCA4 gene. RESULTS: Statistical tests show a very high degree of bilateral symmetry in the extent and progression of visual impairment in the fellow eyes of CRD patients. CONCLUSIONS: These data contribute to a better understanding of CRDs and support the feasibility of clinical trial designs involving unilateral eye treatment with the use of fellow eye as internal control.

Visual evoked potentials in subgroups of migraine with aura patients.

BACKGROUND: Patients suffering from migraine with aura can have either pure visual auras or complex auras with sensory disturbances and dysphasia, or both. Few studies have searched for possible pathophysiological differences between these two subgroups of patients. METHODS: Methods - Forty-seven migraine with aura patients were subdivided in a subgroup with exclusively visual auras (MA, N = 27) and another with complex neurological auras (MA+, N = 20). We recorded pattern-reversal visual evoked potentials (VEP: 15 min of arc cheques, 3.1 reversal per second, 600 sweeps) and measured amplitude and habituation (slope of the linear regression line of amplitude changes from the 1st to 6th block of 100 sweeps) for the N1-P1 and P1-N2 components in patients and, for comparison, in 30 healthy volunteers (HV) of similar age and gender distribution. RESULTS: VEP N1-P1 habituation, i.e. amplitude decrement between 1st and 6th block, which was obvious in most HV (mean slope -0.50), was deficient in both MA (slope +0.01, p = 0.0001) and MA+ (-0.0049, p = 0.001) patients. However, VEP N1-P1 amplitudes across blocks were normal in MA patients, while they were significantly greater in MA+ patients than in HVs. CONCLUSIONS: Our findings suggest that in migraine with aura patients different aura phenotypes may be underpinned by different pathophysiological mechanisms. Pre-activation cortical excitability could be higher in patients with complex neurological auras than in those having pure visual auras or in healthy volunteers.

Optical Coherence Tomography in Alzheimer's Disease: A Meta-Analysis.

BACKGROUND: Alzheimer's disease (AD) is a neurodegenerative disorder, which is likely to start as mild cognitive impairment (MCI) several years before the its full-blown clinical manifestation. Optical coherence tomography (OCT) has been used to detect a loss in peripapillary retina nerve fiber layer (RNFL) and a reduction in macular thickness and volume of people affected by MCI or AD. Here, we performed an aggregate meta-analysis combining results from different studies. METHODS AND FINDINGS: Data sources were case-control studies published between January 2001 and August 2014 (identified through PubMed and Google Scholar databases) that examined the RNFL thickness by means of OCT in AD and MCI patients compared with cognitively healthy controls. RESULTS: 11 studies were identified, including 380 patients with AD, 68 with MCI and 293 healthy controls (HC). The studies suggest that the mean RNFL thickness is reduced in MCI (weighted mean differences in µm, WMD = -13.39, 95% CI: -17.34 to -9.45, p = 0.031) and, even more so, in AD (WMD = -15.95, 95% CI: -21.65 to -10.21, p<0.0001) patients compared to HC. RNFL in the 4 quadrants were all significantly thinner in AD superior (superior WMD = -24.0, 95% CI: -34.9 to -13.1, p<0.0001; inferior WMD = -20.8, 95% CI: -32.0 to -9.7, p<0.0001; nasal WMD = -14.7, 95% CI: -23.9 to -5.5, p<0.0001; and temporal WMD = -10.7, 95% CI: -19.9 to -1.4, p<0.0001); the same significant reduction in quadrant RNFL was observed in MCI patients compared with HC (Inferior WMD = -20.22, 95% CI: -30.41 to -10.03, p = 0.0001; nasal WMD = -7.4, 95% CI: -10.08 to -4.7, p = 0.0000; and temporal WMD = -6.88, 95% CI: -12.62 to -1.13, p = 0.01), with the exception of superior quadrant (WMD = -19.45, 95% CI: -40.23 to 1.32, p = 0.06). CONCLUSION: Results from the meta-analysis support the important role of OCT for RNFL analysis in monitoring the progression of AD and in assessing the effectiveness of purported AD treatments.

Early detection of central visual function decline in cone-rod dystrophy by the use of macular focal cone electroretinogram.

PURPOSE: To evaluate macular focal cone ERG (fERG) as a tool for reliable and early detection of central retinal function decay in cone-rod dystrophy (CRD). METHODS: A retrospective study of the time course of fERG amplitude and its relation to visual acuity alterations was performed in 47 CRD patients followed yearly for 6.0 ± 3.1 years. Macular focal cone ERG was evoked by a flickering uniform red field overlaying the central 18° of visual field. RESULTS: Macular focal cone ERG follow-up allowed a clear-cut identification of CRD patients as stationary or progressive, in agreement with visual acuity follow-up. In all progressive patients, fERG declined whenever visual acuity declined, and--in 50% of the cases--fERG loss anticipated acuity loss of several years. CONCLUSIONS: Macular focal cone ERG represents a sensitive assay to detect, categorize, and follow the progression of central retinal dysfunction in CRD. Its use as a diagnostic tool in CRD may help anticipate, for an individual patient, the likelihood and rate of further disease progression before visual acuity loss has occurred.

Functional effect of Saffron supplementation and risk genotypes in early age-related macular degeneration: a preliminary report.

BACKGROUND: To determine whether the functional effects of oral supplementation with Saffron, a natural compound that proved to be neuroprotective in early age-related macular degeneration, are influenced by complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2) risk genotypes. METHODS: Thirty-three early AMD patients, screened for CFH (rs1061170) and ARMS2 (rs10490924) polymorphisms and receiving Saffron oral supplementation (20 mg/day) over an average period of treatment of 11 months (range, 6-12), were longitudinally evaluated by clinical examination and focal electroretinogram (fERG)-derived macular (18°) flicker sensitivity estimate. fERG amplitude and macular sensitivity, the reciprocal value of the estimated fERG amplitude threshold, were the main outcome measures. RESULTS: After three months of supplementation, mean fERG amplitude and fERG sensitivity improved significantly when compared to baseline values (p < 0.01). These changes were stable throughout the follow-up period. No significant differences in clinical and fERG improvements were observed across different CFH or ARMS2 genotypes. CONCLUSIONS: The present results indicate that the functional effect of Saffron supplementation in individual AMD patients is not related to the major risk genotypes of disease.

A road map to a comprehensive regulation on ventilation technology for operating rooms.

Among strategies to reduce surgical site infection (SSI) risk, we concentrate on the optimization of the air quality through the heating, ventilation, and air conditioning (HVAC) system. Current ventilation standards applied by some European countries have been compared and show uncertainty in the criteria for dimensioning the HVAC system. The development of a comprehensive regulation needs further discussion.

Reduced habituation of the retinal ganglion cell response to sustained pattern stimulation in multiple sclerosis patients.

OBJECTIVE: Sustained pattern stimulation in normal subjects induces adaptive changes in pattern electroretinogram (PERG), an effect that has been interpreted as a response of glial cells and retinal ganglion cells (RGC). The aim of this study was to compare the effect in normal subjects and in multiple sclerosis patients without previous optic neuritis. METHODS: PERGs were elicited by a 7.5 Hz pattern stimulus, presented continuously over 152 s. Response cycles were averaged in 20 packets of 60 events each and amplitude and phase of the 2nd harmonic response was measured. Adaptive changes are expressed as amplitude reduction over the full examination time. RESULTS: In normal subjects PERG amplitude declined progressively to a plateau (dA=-0.46 µV, SE=0.09 µV); in patients the effect size was severely reduced (dA=-0.20 µV, SE=0.04 µV). No significant difference was found in mean amplitude. CONCLUSIONS: The results show reduced RGC habituation in patients, suggesting an abnormal gain and sensitivity control in the inner retina, even in absence of clinical optic neuritis. Recent findings in astrocyte biology and indications drawn from a mathematical model point to a key role of glial cells in this process. SIGNIFICANCE: The proposed methodology may have implications in the assessment of MS patients and in understanding the pathophysiology of neurological and retinal disorders.

Long-term decline of central cone function in retinitis pigmentosa evaluated by focal electroretinogram.

PURPOSE: We evaluated long-term changes of central cone-mediated function in retinitis pigmentosa (RP) patients by recording focal electroretinograms (fERG). METHODS: A cohort of 43 RP patients was followed from 4 to 16 years (average follow-up 9.3 years, average 10 examinations/patient) by recording the fERG response to a flickering uniform red field overlaying the central 18° of visual field (VF). Statistical censoring led to a reduced dataset of 32 patients (autosomal dominant 9, recessive 5, sporadic 5, x-linked 1, Usher II 12), from which long-term decay rates were estimated by global fitting of individual fERG amplitude time-curves. RESULTS: Long-term follow-up of central cone FERG amplitude showed two main features: short-term variability and long-term decline. fERG short-term variability range was 0.14 to 0.2 log units. Mean yearly decay rate of central fERG was 5.6% (95% confidence interval [CI] 4%-7%). Yearly decline depended on inheritance pattern, being significantly greater in autosomal recessive and sporadic compared to autosomal dominant RP. The degree of central cone fERG decline was unrelated to the size of the residual VF. CONCLUSIONS: The decline of central cone function is significantly slower than global cone function decline in RP. Central cone fERG loss is independent of residual VF.

Retinal function and CFH-ARMS2 polymorphisms analysis: a pilot study in Italian AMD patients.

Two major susceptibility genes, complement factor H (CFH) and age-related maculopathy susceptibility 2 (ARMS2), have been implicated in age-related macular degeneration (AMD) pathogenesis. We analyzed the association between CFH rs1061170 and/or ARMS2 rs10490924 polymorphisms with central retinal function properties, as evaluated by focal electroretinogram (fERG). Forty early AMD patients, with preserved visual acuity and typical macular lesions, underwent fERG recording (in response to 41 Hz flicker stimuli presented to the central 18 degrees) and CFH/ARMS2 genotyping. Mean fERG amplitude and sensitivity decreased in patients carrying CFH rs1061170 polymorphism (p < 0.01), compared with wild type ones, although visual acuity and funduscopic features were similar across the 2 groups. No significant fERG phase changes were observed. No association was detected between ARMS2 (rs10490924) polymorphism and fERG parameters. Our findings indicate that CFH (rs1061170) polymorphism impacts significantly on retinal function in early AMD patients, and support the hypothesis that dysfunctional CFH might result in early retinal function loss due to a reduction in the immune antioxidant defense mechanism.

Subfoveal choroidal blood flow and central retinal function in early glaucoma.

PURPOSE: To assess subfoveal choroidal blood flow (ChBF) in patients with early manifest glaucoma (EMG) and to compare blood flow with functional measures of central retinal integrity, standard automated perimetry (SAP) and pattern electroretinogram (PERG). METHODS: Subfoveal ChBF was determined by confocal, real-time laser Doppler flowmetry in 24 patients with EMG [>-6 dB mean deviation (MD), age range: 29-77 years, visual acuity: 20/25-20/20] and 23 age-matched control subjects. All patients had a therapeutically (topical beta-blockers with or without prostaglandin analogues) controlled intraocular pressure (IOP < 20 mmHg). Subfoveal choroidal blood volume (ChBVol), velocity (ChBVel) and ChBF were determined as the average of three 60 second recordings. In all patients and controls, the PERG and SAP (Humphrey 30-2), following standardized protocols, were also recorded. RESULTS: In patients with EMG, reductions in average ChBVel and ChBF were roughly equal, respectively, by 30% and 33.4% (p < 0.01), when compared to control subjects, so that there was no significant difference in ChBVol between the two groups. Pattern electroretinogram amplitudes were reduced by 46% (p < 0.01) in patients compared to controls. No correlation was found between any of the ChBF parameters and PERG amplitude, or Humphrey 30-2 MD and pattern standard deviation. CONCLUSION: The results suggest a significant alteration of both ChBVel and ChBF in EMG, which does not appear to be associated with the severity of central retinal dysfunction. These findings may contribute to a better understanding of the pathophysiology of early glaucomatous damage in EMG and have implications for the treatment of this pathologic condition.

Topical nerve growth factor as a visual rescue strategy in pediatric optic gliomas: a pilot study including electrophysiology.

BACKGROUND: To date, no specific therapy is available for optic glioma (OG)-induced visual loss. OBJECTIVE: To evaluate the effects on visual function of murine nerve growth factor (NGF) eye drop administration in children with severe visual impairment due to low-grade OGs. METHODS: Five patients with OGs and advanced optic nerve atrophy were assessed before and after a single 10-day course of 1 mg murine NGF topical administration by clinical evaluation, visual evoked potentials (VEPs), and brain magnetic resonance imaging (MRI). VEPs, the main functional outcome measure, were recorded at baseline and 1, 30, 45, 90, and 180 days posttreatment. MRI examinations were performed at baseline and at 180 days after NGF treatment. Six untreated control patients with OGs also underwent serial VEPs, clinical testing, and MRI assessments. RESULTS: After NGF treatment, median VEPs amplitude showed a progressive increase from the baseline values (P < .01). VEPs reached a maximum amplitude at 90 days (170% increase) and declined at 180 days, still remaining above the baseline level. Perception of spontaneous visual phosphenes was noted in all patients after NGF administration. MRI showed stable tumor size. In controls, clinical findings and VEPs did not show any significant change over the observation period. CONCLUSIONS: The findings from the study show that NGF administration may be an effective and safe adjunct therapy in children with optic atrophy due to OGs. The beneficial effect on optic nerve function suggests a visual rescuing mechanism exerted by murine NGF on the residual viable optic pathways.

Subfoveal choroidal blood flow and central retinal function in retinitis pigmentosa.

PURPOSE: To determine whether subfoveal choroidal blood flow is altered in retinitis pigmentosa (RP) and whether this alteration is associated with central cone-mediated dysfunction. METHODS: In 31 RP patients (age range, 15-72 years) with preserved visual acuity (range: 20/30-20/20), subfoveal choroidal blood flow was measured by real-time, confocal laser Doppler flowmetry, and focal macular (18°) electroretinograms (FERGs) were elicited by 41 Hz flickering stimuli. Twenty normal subjects served as controls. The following average blood flow parameters were determined based on three 60-second recordings: volume (ChBVol), velocity (ChBVel), and flow (ChBF), the last being proportional to blood flow if the hematocrit remains constant. The amplitude and phase of the FERG first harmonic component were measured. RESULTS: On average, ChBF and ChBVel were reduced by 26% (P ≤ 0.02) in RP patients compared to controls, whereas ChBVol was similar in the two groups. FERG amplitudes were reduced by 60% (P < 0.01) in patients compared with controls. FERG phases of patients tended to be delayed (P < 0.08) compared with their values in the controls. In patients, FERG phase delays were correlated (r = 0.50, P < 0.01) with ChBF and ChBVel values. FERG amplitudes were correlated (r = 0.49, P < 0.01) with ChBVol values. CONCLUSIONS: These data indicate significant alterations of subfoveal choroidal hemodynamic in RP and suggest a link between the alteration of ChBF and the RP-associated central cone-mediated dysfunction as assessed by the FERG.

Influence of saffron supplementation on retinal flicker sensitivity in early age-related macular degeneration.

PURPOSE: To evaluate the functional effect of short-term supplementation of saffron, a spice containing the antioxidant carotenoids crocin and crocetin, in early age-related macular degeneration (AMD). METHODS: Twenty-five patients with AMD were randomly assigned to oral saffron 20 mg/d or placebo supplementation over a 3-month period and then reverted to placebo or saffron for a further 3 months. Focal electroretinograms (fERGs) and clinical findings were recorded at baseline and after 3 months of saffron or placebo supplementation. fERGs were recorded in response to a sinusoidally modulated (41 Hz), uniform field presented to the macular region (18°) at different modulations between 16.5% and 93.5%. Main outcome measures were fERG amplitude (in microvolts), phase (in degrees), and modulation thresholds. RESULTS: After saffron, patients' fERGs were increased in amplitude, compared with either baseline or values found after placebo supplementation (mean change after saffron, 0.25 log µV; mean change after placebo, -0.003 log µV; P < 0.01). fERG thresholds were decreased after saffron supplementation but not placebo, compared with baseline (mean change after saffron, -0.26 log units; mean change after placebo, 0.0003 log units). CONCLUSIONS: The results indicate that short-term saffron supplementation improves retinal flicker sensitivity in early AMD. Although the results must be further replicated and the clinical significance is yet to be evaluated, they provide important clues that nutritional carotenoids may affect AMD in novel and unexpected ways, possibly beyond their antioxidant properties. (ClinicalTrials.gov number, NCT00951288.).

Lack of habituation in the light adapted flicker electroretinogram of normal subjects: a comparison with pattern electroretinogram.

OBJECTIVE: Sustained pattern stimulation (SPS) induces habituation in the normal pattern electroretinogram (PERG). In this study, the authors evaluated whether sustained flicker stimulation (SFS) induces habituation in the normal flicker ERG (FERG). METHODS: FERGs were elicited in normal volunteers by an 8Hz flicker stimulus, presented continuously over 3 min after 20 min of light adaptation. One stimulus temporal period was sampled and averaged in packets (n=20) of 60 events, each of 8s duration. Amplitudes and phases of the response 1st and 2nd harmonics (1F and 2F, respectively) were measured. FERG results were compared with those obtained by recording PERGs with a similar SPS paradigm. RESULTS: During SFS, FERG 2F showed a modest increase in amplitude (about 25%, p<0.05). No changes were observed for the 1F amplitude and for the phase of both components. In contrast, PERG amplitude showed SPS-induced habituation, described by an exponential decay with a time constant of approximately 20s. CONCLUSIONS: The normal FERG, unlike PERG, does not show habituation, suggesting that the adaptive changes of retinal neurons underlying FERG are different from those of PERG generators. SIGNIFICANCE: Our findings may have implications for diagnosis and/or pathophysiology of retinal disorders involving the inner retina.

Regional cone-mediated dysfunction in age-related maculopathy evaluated by focal electroretinograms: relationship with retinal morphology and perimetric sensitivity.

PURPOSE: To assess regional cone-mediated function in age-related maculopathy (ARM) by focal electroretinograms (FERGs), and to compare FERGs with morphologic changes and perimetric sensitivity at corresponding locations. METHODS: Twenty-six ARM patients and 12 age-matched controls were evaluated. FERGs were elicited by either a central (0-2.25 degrees , C) or a paracentral annular (2.25-9 degrees , PC) flickering (41 Hz) field, presented on a light-adapting background. Morphological changes (soft drusen and/or retinal pigment epithelium defects) at matched locations were assessed by fundus photography and fluorescein angiography. Perimetric sensitivity was measured by Octopus 10 degrees program (tM2). RESULTS: When compared to controls, mean C and PC FERG amplitudes of patients were reduced (p < 0.01), and the mean PC FERG phase was delayed (p < 0.01). Both FERG delays and morphologic lesions tended to involve to a greater extent the PC compared to the C region. In the C region, perimetric losses were correlated with the extent of morphologic lesions (p < 0.05). In the PC region, perimetric losses were correlated with FERG amplitudes (p < 0.05). CONCLUSIONS: In ARM, FERG losses are eccentricity-dependent, not quantitatively linked to retinal morphology, and correlated with perimetric losses, suggesting a heterogeneous dysfunction with loss of both C and PC perimetric sensitivities.