Increase In Implicit Time Research Articles

Влияние исходных структурных нарушений и послеоперационного изменения перфузии на функциональное восстановление сетчатки после хирургического лечения сквозных макулярных разрывов

Purpose. To evaluate effect of preoperative local structural retinal changes and capillary perfusion in idiopathic full-thickness macular holes (FTMH) on the recovery of functional activity of the retina after surgical treatment. Materials and methods. We used optical coherence tomography (OCT) and OCT-angiography (OCT-A), microperimetry, multifocal electroretinography. In 25 eyes with FTMH the density of capillaries in the superficial and deep capillary plexus (SCP and DCP), retinal sensitivity (RS), amplitude and implicit time of P1 were studied at 13 points located at different distances from the fixation point were evaluated. Data were analyzed in the projection of the hole, intraretinal cystic changes (ICC), neuroepithelial detachment (NED) and intact retina before surgical treatment, 7 days, and 3 months after. Results. In the area of hole, ICC, and NED, in comparison with intact areas of the retina, a significant decrease in RS, an increase in implicit time and a decrease in amplitude of P1, and a decrease in capillary density in the SCP and DCP were revealed. Functional restoration of the retina with an increase in its perfusion was noted 3 months after the surgery. The correlation was found between postoperative changes in RS and changes in capillary density in the SCP in the projection of NED (R=0.32, p=0.001) and ICC (R=0.19, p=0.001), as well as in the DCP in the projection of NED and ICC (R=0.31, p=0.001). The change in the amplitude P1 in the postoperative period significantly correlated with the change in perfusion in the SCP in the projection of the NED (R=0.38, p=0.001) and the hole area (R=0.31, p=0.001), as well as in the DCP in the projection of the ICC (R=0.31, p=0.01) and in the area of NED (R=0.28, p=0.001). Conclusion. Thus, when using a multimodal topographically oriented approach, a relationship was found in the postoperative period of changes in functional parameters at various points in the macular area with changes in local perfusion at the level of both SCP and DCP, while the relationship is most significant in the projection of NED along the tear edge and in the areas of ICC. Key words: full-thickness macular hole (FTMH), microperimetry, multifocal electroretinography, multimodal imaging, optical coherence tomography, optical coherence tomography-angiography

Observations for Sjögren’s Pigment Epithelial Reticular Dystrophy in a 16-Year-Old Boy—An Extremely Rare Retinal Case Report

The purpose of this publication is to present an extremely rare case of Sjögren's pigment epithelial reticular dystrophy. So far, 10 such publications have been found in world literature. A 16-year-old boy was diagnosed due to a slight loss of visual acuity, confirmed in static perimetry/24-2/. Abnormal dense clusters of retinal pigment epithelium (RPE) cells forming a reticular network pattern (resembling a fishing net) with marked knots were detected by fundoscopy in the macular area and the mid-periphery of the retina. No abnormalities were found in the anterior segment, intraocular pressure, kinetic perimetry, Ishihara or Farnsworth D-15 tests or OCT. Fluorescein angiography confirmed blocked fluorescence from the choroidal vessels caused by the pigment in RPE. An autofluorescence test showed hypofluorescent foci corresponding to symmetrical and bilateral retinal hyperpigmentation with an RPE reticular pattern. Multifocal ERG (mfERG) revealed slight cone photoreceptor and bipolar bioelectrical dysfunction. Electrooculography (EOG) showed significant asymmetry (Arden Ratio 1.8), suggesting bioelectrical dysfunction of RPE/photoreceptors. Flash ERG (ERG) revealed only slight increase in implicit time of the a and b waves of the rod and cone responses and exclude cone-rod dystrophies. This article highlights the importance of the results of ophthalmoscopy, fluorescein angiography, autofluorescence, mfERG, fERG, EOG and genetic tests for Sjögren's reticular dystrophy with a pathogenic variant in the region of the C2 gene-c.841_849+19del (dbSNP rs9332736).

Macular function in patients with medium myopia

PurposeThis work aims at assessing whether electrophysiological functional changes in the macular region appear in medium myopia, even in the presence of a normal macular OCT scan and how axial length correlates with macular OCT parameters in medium myopia.MethodsThe study included right eyes of 17 patients with myopia of medium degree (SE < − 6D to > − 3D). Control group consisted of 20 eyes of patients of age and sex that matched healthy controls with normal macular and optic nerve OCT results and normal axial length. Full ophthalmic examination (the distance best-corrected visual acuity, intraocular pressure, refractive error, the anterior and posterior segment of the eye in a slit lamp, the axial length of the eyeball) with OCT of the macular and optic disk and the PERG test were performed in the study and control groups. Only the patients with normal ophthalmic and OCT examination results were qualified. The interview covering questions on risk factors of myopia onset and progression such as prematurity, family history of myopia was carried out in both groups. In myopic group, the question relating to time of near work was also asked. Study and control groups were tested with the use of Shapiro–Wilk, Mann–Whitney, Student’s t test, Pearson and Spearman's rank correlation tests.ResultsAL was significantly longer in myopia group (p < 0.01), and SE value was lower (p < 0.01). Longer implicit time of P50 was found in the study group, but amplitudes of P50 and N95 waves were not significantly reduced (p < 0.05). AL showed correlations with P50 implicit time (p < 0.05) and with reduction in retinal fiber nerve layer and ganglion cells and inner plexus layer (p < 0.05).ConclusionPatients with myopia of medium degree have a dysfunction of retinal cone system of the macular region even when OCT scans show no abnormalities. Elongation of AL correlates with reduction in retinal fiber nerve layer and ganglion cells and inner plexus layer. Longitudinal follow-up studies may answer the question whether this increase in implicit time may be indicative of a faster myopia progression or of myopic retinal pathology, i.e., whether it may help to determine which patient would benefit from earlier or more intensive management of myopia progression.

Differences in Multifocal Electroretinogram Study in Two Populations of Type 1 and Type 2 Diabetes Mellitus Patients without Diabetic Retinopathy.

(1) Background: Diabetic retinopathy (DR) is a diabetes mellitus (DM) complication where neurodegeneration plays a significant role. The aim of our study was to determine the differences between type 1 DM (T1DM) and 2 DM (T2DM) in the multifocal electroretinogram (mERG).; (2) Methods: A mERG study was performed in two groups, a T1DM group with 72 eyes of 36 patients compared with 72 eyes of 36 patients with T2DM, randomly selected from our DM databases, without DR. We studied how HbA1c and DM duration affects amplitude and implicit time of mERG; (3) Results: the study of DM duration shows patients with T1DM have lower amplitude values compared to T2DM patients, although implicit time increases in patients with T2DM. HbA1c over 7% only affects T1DM patients with an increase of implicit time; (4) Conclusions: the retinas of patients with T1DM seem more sensitive to changes in HbA1c levels than in patients with DMT2, although the duration of diabetes affects both types of DM patients.

New criteria for evaluation of electroretinogram in patients with retinitis pigmentosa.

Electroretinogram (ERG) plays an essential role in the diagnosis of retinal disease. Choosing appropriate methods could extract valuable information from ERG. In this study, a new criterion based on time-frequency domain analysis was proposed to investigate the retina in retinitis pigmentosa (RP) patients. The total number of 16 eyes from eight RP patients and 20 eyes from age-matched healthy subjects were assessed. The signals included photopic and scotopic ERGs. Continuous wavelet transform was applied to ERGs. Dominant frequencies were extracted, and the contours related to these dominant frequencies were selected. As a new criterion, the areas related to dominant frequency contours were considered a feature to differentiate the RP and normal groups. To better evaluate the proposed criterion results, the time-domain analysis characteristics of ERG were also considered. The results showed an increase in implicit time and reduced amplitude in RP patients (P < 0.05). A significant decrease of dominant frequencies and increasing their occurrence time were seen in ERG of RP patients. Also, in RP patients, the third dominant frequency was disappeared from the three main frequencies observed in photopic ERGs of normal subjects. The area criterion showed a significant decrease in RP groups (P < 0.05). RP can cause changes in the time and time-frequency components of the ERG. The area index could represent a new view of the characteristics of the ERG in the time-frequency domain. This criterion can help the ophthalmologist to have a better evaluation of retinal disease.

Neurodegenerative changes of the retina in patients with diabetes

To investigate the morphological and functional state of the outer and inner layers of the retina in patients with diabetes mellitus (DM) and nonproliferative diabetic retinopathy (NPDR), to determine the presence and nature of the relationships between structural and functional changes. The study included 50 patients with subcompensated diabetes and NPDR and 40 people from the control group (healthy). All patients underwent OCT of the retina and optic nerve using RTVue-100 apparatus (Optovue, USA), as well as multifocal electroretinography (mfERG) and pattern electroretinography (PERG) on EP-1000 Multifocal device ('Tomey GmbH', Germany). When analyzing the results of OCT in patients with NPDR, a decrease in the total thickness of the retina and the thickness of its inner layers in the fovea and parafovea regions was found in comparison with the control group (p<0.001), thinning of the retinal ganglion cell (GCS) complex with increased focal losses (FLV) of up to 1.4% (Mann-Whitney test, p=0.001). In the group of patients with diabetes, there was a statistically significant decrease in the density and amplitude of P1 mfERG in all five 'rings' (Mann-Whitney test, p<0.001), increase in implicit time in the first 3 rings, decrease in P50 and N95 amplitude, increase in implicit time of N95 PERG (p=0.001) compared to the control group. The study revealed changes in the structure and functioning of the outer and inner layers of the retina in patients with NPDR, and established a reliable correlation between the morphological parameters (according to the OCT) and electrophysiological parameters (according to the mfERG and PERG data).

Neuroretinal dysfunctions in regular cannabis users: An impact of cannabis on retinal neurotransmission?

IntroductionAlthough cannabis is very widespread worldwide, its brain toxicity is poorly understood. The neuroretina is an accessible extension of the brain and could be a relevant site for investigating neurotransmission abnormalities in neuropsychiatric disorders. The retina has a functional endocannabinoid system involved in the regulation of retinal neurotransmission. In animals, the modulation of this system led to retinal dysfunctions measured with the electroretinogram (ERG).ObjectivesTo assess whether the regular cannabis use could affect the neuroretinal function.AimsAssessments of the neuroretinal function in cannabis users compared with controls.MethodsRecordings of pattern, flash and on-off ERG were performed in 55 cannabis users and 29 controls. The amplitude and implicit time of the following waves were evaluated: N95 (pattern); a – and b – (flash); a –, b- and d1 – (on-off).ResultsCannabis users showed a significant increase in implicit time of the waves N95 (P = 0.0001), a- (P = 0.029) and b – (P = 0.002) for the flash ERG and b – (P = 0.016) and d1 – (P = 0.027) for the on-off ERG, compared with controls. No significant difference was found between groups in terms of wave's amplitudes.ConclusionsThese results show a delay in the response of cones, bipolar and ganglion cells of the on and off pathways to constitute a delay of ≈ 6 ms in the transmission of information from the retina to the brain in cannabis users. Cannabis could disrupt the regulatory role of the cannabinoid system and impair retinal glutamatergic neurotransmission. The consequences on visual perception should be explored in future studies.Disclosure of interestThe authors have not supplied their declaration of competing interest.

ET-1 plasma levels, choroidal thickness and multifocal electroretinogram in retinitis pigmentosa

AimTo assess the relationship between both photoreceptor function and choroidal thickness and endothelin-1 (ET-1) plasma levels in patients with early stage retinitis pigmentosa (RP). Main methodsWe compared 24 RP patients (14 males and 10 females), 25 to 42years of age (mean age: 34±7years) with 24 healthy controls (12 males and 12 females) aged between 28 and 45years (mean 36±6.8years). All patients underwent visual field test, electroretinogram and multifocal-electroretinogram and choroidal thickness measurement by using spectral domain optical coherence tomography. Key findingsRP patients had a visual acuity of 0.95, a mean defect of the visual field of −7.90±1.75dB, a pattern standard deviation index of 6.09±4.22dB and a b-wave ERG amplitude of 45.08±8.24μV. Notably RP subjects showed significantly increased ET-1 plasma levels and reduced choroidal thickness compared with controls: respectively, 2.143±0.258pg/ml vs. 1.219±0.236pg/ml; p<0.002 and 226.75±76.37μm vs. 303.9±39.87μm; p<0.03. Spearman's correlation test highlighted that the increase of ET-1 plasma levels was related with the decrease of choroidal thickness (r=−0.702; p<0.023) and the increase of implicit time in both ring 2 (r=−0.669; p<0.034) and ring 3 (r=−0.883; p<0.007) of mfERG. SignificanceIncreased ET-1 plasma levels may play a key role in the impairment of retinal and choroidal blood flow due to the vasoconstriction induced by ET-1. This could lead to worsening of the abiotrophic process of the macular photoreceptors.

Unilateral Retinitis Pigmentosa: A Proposal of Genetic Pathogenic Mechanisms

To investigate and integrate anatomic and physiologic findings from a group of patients who present retinitis pigmentosa affecting just one eye and use this information to propose mechanisms of disease pathogenesis. This prospective cross-sectional study examined 5 patients, all female, from 8 to 60 years old. The study was conducted in 4 university hospitals. The patients were selected according to the characteristics of ocular involvement, notably unilateral presentation of similar anatomic and functional abnormalities. Full-field electroretinogram, fundus photography, fundus autofluorescence, infrared imaging, optical coherence tomography, and genetic testing were performed. Full-field electroretinogram showed unilateral decrease in amplitude and increase in implicit time; autofluorescence showed unilateral areas of decreased intensity. The USH2AW4149R mutation was confirmed in one patient. Imaging and functional testing are important in elucidating the unilateral pattern of the disease and in monitoring these individuals. Mosaicism or somatic mutation may cause unilateral genetic disease presentation.

Diffuse retinal injury from a non-penetrating TASER dart

To describe a non-penetrating TASER gun injury resulting in a small exudative retinal detachment but significant visual acuity and retinal function loss as demonstrated by electroretinography (ERG). A 39-year-old man presented to the emergency department with a TASER barb embedded in his right lower lid. A complete clinical ophthalmologic examination and surgical extrication were performed, as well as radiologic imaging and Ganzfeld electroretinography. No scleral penetration was observed on surgical exploration. Retinal examination showed a peripheral exudative detachment. Subsequent follow-up revealed progressive resolution of the detachment and improvement in visual acuity. The ERG showed a 63-70% decrease in rod a- and b-waves, while isolated cone responses were reduced by only 10%, with a minimal increase in implicit time. This case shows that periocular TASER injuries, even if apparently superficial, may result in significant ocular damage. ERG may be useful in the diagnosis of visual loss attributed to disturbance in photoreceptor function, in the absence of anatomically evident damage.

Age-Related Changes in Retinal Functional Topography

To perform a detailed topographical analysis of functional age-related changes over the retina. Fifty-nine normal phakic subjects aged 10 to 69 years were divided into six groups, according to decade of age. mfERG traces were recorded from the central 60 degrees of the retina, with a resolution of 61 and 103 scaled hexagons. Group medians of peak amplitude and latency of the first- and second-order (first slice) responses were used to generate 3-D topographical maps. With age, there was a continuous loss of amplitude and delay of implicit time of the first- and the second-order response components, but the topography of the loss was not uniform across the retina. Trend analyses on ring group data showed a significant decrease in amplitude of first- and second-order responses although the age relationship of second-order responses was more complex. The loss of first-order kernel amplitude was generally accompanied by a rise in implicit time. Second-order kernel latencies showed no uniform alteration with age. Consistent with previous work, a steady loss of amplitude and increase of implicit time was observed with age. The topographical 3-D data, however, reveal age-related functional alterations in the retina beyond those found in ring averages, suggesting that these are masked by the standard analysis. Thus, the choice of physiologically coherent regions of interest may increase the sensitivity of detecting age-related change in multifocal analysis of retinal function.

Functional characteristic of the retina in glaucoma

Abstract Purpose: Purpose: To investigate bioelectrical activity of the retina in normal subjects and patients with primary open angle glaucoma (POAG). Methods: Methods: 40 eyes of 20 normal subjects and 80 eyes of 45 patients with different stages of glaucoma were examined with electroretinogram (full‐field, flicker, pattern, multifocal ERG, ERG to long duration stimulus and chromatic ERG to red, green and blue stimulus). Intraocular pressure was 21 mm Hg or less in all patients. All patients were also tested on HRT II. Results: Full‐field ERG recordings showed a decrease of b‐wave amplitude and an increase of implicit time in advanced and late stages of POAG. Macular chromatic ERG to red stimulus of 15° area was subnormal in all stages of POAG (p&lt;0,01). The density of retinal responses of multifocal ERG was progressively decreased in all stages. An amplitude of P50 component of pattern ERG in initial stage of glaucoma was decreased (p&lt;0,05). In advanced stage of glaucoma a significant decrease of amplitudes of P50 and N95 components and prolonged implicit time of N95 component were observed.The off‐component of long duration stimulus flash ERG in all stages was subnormal. The on‐component in early stage was supernormal, whereas in advanced and late stages was subnormal. A damage of off‐cone system of the retina was the first symptom of retinal changes in glaucoma. In initial stage of glaucoma ERG symptoms of glaucomatous neuropathy were first detected even before changes on HRT test. Conclusions: The retinal pathology presented in ERG symptoms may probably reflect some pathogenetic mechanisms of development of glaucomatous damage, including excitotoxcic factors and ischemia.

Changes in Implicit Time of the Multifocal Electroretinogram Response Following Contrast Adaptation

Purpose: Contrast adaptation, produced by prolonged viewing of high contrast gratings, has been suggested to occur at both retinal and cortical locations within the visual pathway. We sought to investigate the characteristics of retinal contrast adaptation using the multifocal electroretinogram (mfERG). Methods: Twenty subjects, with a mean age of 27.8 ± 5.3 years, underwent mfERG testing using VERIS I. The mfERG was measured after 10 minutes of adaptation to 94% contrast, 5 cyc/deg, sinusoidal, vertical gratings and to an equi-luminance blank control. The mfERG stimulus array consisted of 61-scaled hexagons and flickered according to a pseudorandom binary m-sequence (213−1). Changes in amplitude and implicit time of the first-order kernel were analyzed to determine the effect of contrast adaptation on retinal responses. Results: Adaptation to the vertical grating pattern produced a 2.5 ms increase in implicit time, and the response delay was greatest in the more peripheral parts of the retina (7.6° to 30°). Contrast adaptation did not produce statistically significant changes to the amplitude of the mfERG waveform. Conclusions: Contrast adaptation produced by prolonged viewing of high contrast gratings had a significant effect on retinal responses. It has been suggested that contrast adaptation may play a role in the development of nearwork induced myopia; further work investigating retinal contrast adaptation in myopic individuals may be of interest.

Multifocal electroretinogram: age-related changes for different luminance levels.

Age-related changes in the first-order multifocal electroretinogram (mfERG) responses were measured for two different luminance levels (200 and 700 cd.m(-2)). The relative contribution of optical and neural factors to senescent change in response was evaluated. Data were obtained from one eye of each of 71 normal phakic subjects, age 9-80 years. The mfERG responses were recorded with the 7" stimulus-refractor unit (EDI) and VERIS 4.3 using the following protocol: bipolar contact lens, 103 hexagons, consecutive stimulation with 200 and 700 cd.m(-2), pupils > or =6 mm, amplification of 10(5), filter cut-offs at 10 and 300 Hz. Age-correlated decreases in amplitude and response density and increases in P1 implicit time were found for both luminance levels. The mean response density (nV.deg(-2)) was higher for the 700 cd.m(-2) stimulus, but the rate of change with age was not significantly different from that obtained with the 200 cd.m(-2) stimulus. Implicit time was not significantly different for the two light levels, nor was the rate of change with age. The decrease in response density and the increase in implicit time with age were significant across all retinal regions, dividing the 50 deg stimulus into six concentric rings. Age-related change in response density was greatest for the central retina and decreased with increasing retinal eccentricity. Log mfERG response changes linearly as a function of age. Analyses of the effects of reduced ocular media transmission and increased stray light, along with ancillary data obtained from pseudophakes, imply that age-related changes in the mfERG are due to both optical and neural factors.

Age-related changes in the first order Weiner kernel visual evoked potential

Visual evoked potentials were obtained from 112 subjects (215 eyes) aged 5 to 79 years with fast random stimuli. The stimulus (the presence or absence of the initiation of a reversal) and response (voltage measurements) were used in calculating the first order Wiener kernels to obtain the visual evoked potentials. Five check sizes were used to stimulate each eye. The implicit time of the major negative wave showed a significant increase with age for each check size used. Regression lines for the implicit time vs age data for male subjects were significantly different from those of females. The y-intercepts were lower and the slope of the regression lines were consistently steeper for males. Thus the rate of increase in implicit time was higher in males. The relationship of the amplitude of the major wave to age did not appear to be linear. The data suggested that a second-order polynomial curve might be an appropriate representation of the relationship.

Visually evoked response (VER) in amblyopia: A diagnostic and prognostic indicator?

A study comprising 15 cases of anisometropic amblyopia and 15 cases of strabismic amblyopia was undertaken to analyse the alterations in the visually evoked response (VER) in amblyopia. Ten normal cases were taken to standardize the technique. A Nicolet Clinical Averager CA100 was used to record the VER. A full ophthalmic check up including cycloplegic refraction, visual acuity recording and fixation pattern by visuscope was carried out in all the cases.In normal cases the amplitude and implicit time of VER showed no statistically significant difference between the two eyes. However, a wide inter-subject variability was observed. the maximum amplitude was seen with a check size of 60′. In amblyopic eyes (both strabismic and anisometropic) there was a significant reduction in the amplitude and a significant increase in the implicit time when compared to the normal fellow eye. A significant amplitude difference of more than 5 μV, as also a significant increase of implicit time (more than 10 msec) was notice...

Modification of pattern reversal VERs by ocular accommodation

The amplitudes and implicit times of the P-1 component of monocular transient pattern VERs elicited by reversing checkerboard targets were measured in 6 conditions: (1) Ocular accommodation (Ao) elicited by minus power ophthalmic lenses; (2) Ao stimulated by minus lenses with the natural pupil of the test eye dilated and replaced by an artificial pupil; (3) accommodative demand and pupil size fixed with retinal image size (I r) changed by afocal minifying lenses, (4) accommodative demand andI r fixed but pupil size changed; (5) Ao elicited by minus lenses for three sizes of reversing checkerboards, and (6) Ao elicited by minus lenses for a constant checkerboard size with three check sizes. The observed decrease in VER amplitude with Ao could not be attributed entirely to the effects of pupil size orI r. The rate at which the amplitude of P-1 decreased with Ao was not affected by checkerboard check size, but was closely correlated with checkerboard field size. The implicit time of P-1 first decreased slightly below baseline values at low and moderate levels of Ao and then tended to increase significantly at higher levels. The increase in implicit time at high levels of Ao could be explained adequately by the effects of pupil size alone on the VER. However, where Ao occurred without pupillary miosis, the increase in implicit time could only be explained by focusing error.

Effect of Accommodation on Visually Evoked Response

Accommodation causes variation in both visually evoked response (VER) amplitude and implicit time. Measurements indicate an average decrease in amplitude of about 1 muV per diopter and an increase in implicit time of about 1.5 msec per diopter for increasing amounts of accommodation. Care should be taken to eliminate any accommodative stimulus which could alter the normal VER response during clinical evaluation.