Induced Component Research Articles

Effects of Optical Zone Variation of High-Addition Multifocal Contact Lenses on the Global Flash Multifocal Electroretinography.

To evaluate the retinal response to myopic defocus after the wear of soft multifocal contact lenses with high addition through electroretinography. Twenty-seven participants meeting inclusion criteria were enrolled. Tropicamide 1% drops (2) were instilled. Participants were then fitted with three different contact lenses: a single-vision spherical lens (SE +3.00 D), L1, serving as a control, and two soft multifocal lens designs (SE +3.00 D/add +10 D), one with a central distance zone of 4.0 mm (L2) and one with a central distance zone of 7.0 mm (L3). A global flash multifocal electroretinography was performed. Direct component (DC) amplitude, DC peak time, induced component (IC) amplitude, and IC peak time were recorded. Waveforms were grouped into five concentric areas, covering from 0° to 24° of retinal eccentricity. Differences of L2/L3 versus L1 were analyzed with t tests. Finally, correlations were calculated between the percentage of defocus in the pupil area versus the electroretinography results. Results show that the DC amplitude, caused mainly by photoreceptors and bipolar cells, is not influenced by the design of the lenses. The IC amplitude, however, is significantly decreased when the lens with a smaller optical zone (L2) is worn. This significant difference only concerns the ring 5, which corresponds to a retinal eccentricity of 15.7° to 24.0°. Soft multifocal lens designs influence the peripheral retinal reaction to defocus. A larger treatment zone seems to significantly impact the retinal response to defocus between 15.7° and 24.0° of eccentricity from the macula.

Enhancement of the Inner Foveal Response of Young Adults with Extended-Depth-of-Focus Contact Lens for Myopia Management.

Myopia management contact lenses have been shown to successfully decrease the rate of eye elongation in children by changing the peripheral refractive profile of the retina. Despite the efforts of the scientific community, the retinal response mechanism to defocus is still unknown. The purpose of this study was to evaluate the local electrophysiological response of the retina with a myopia control contact lens (CL) compared to a single-vision CL of the same material. The retinal electrical activity and peripheral refraction of 16 eyes (16 subjects, 27.5 ± 5.7 years, 13 females and 3 males) with myopia between -0.75 D and -6.00 D (astigmatism < 1.00 D) were assessed with two CLs (Filcon 5B): a single-vision (SV) CL and an extended-depth-of-focus (EDOF) CL used for myopia management. The peripheral refraction was assessed with an open-field WAM-5500 auto-refractometer/keratometer in four meridians separated by 45° at 2.50 m distance. The global-flash multifocal electroretinogram (gf-mfERG) was recorded with the Reti-port/scan21 (Roland Consult) using a stimulus of 61 hexagons. The implicit time (in milliseconds) and response density (RD, in nV/deg2) of the direct (DC) and induced (IC) components were used for comparison between lenses in physiological pupil conditions. Although the EDOF decreased both the HCVA and the LCVA (one and two lines, respectively; p < 0.003), it still allowed a good VA. The EDOF lens induced a myopic shift in most retinal areas, with a higher and statistically significant effect on the nasal retina. No differences in the implicit times of the DC and IC components were observed between SV and EDOF. Compared with the SV, the EDOF lens showed a higher RD in the IC component in the foveal region (p = 0.032). In the remaining retinal areas, the EDOF evoked lower, non-statistically significant RD in both the DC and IC components. The EDOF myopia control CL enhanced the response of the inner layers of the fovea. This might suggest that, besides other mechanisms potentially involved, the central foveal retinal activity might be involved in the mechanism of myopia control with these lenses.

Retinal response to two commercially available contact lenses for myopia control

Aims/Purpose: Myopia control contact lenses (CLs) have shown optimistic results in eye growth retention in children. However, it is still unknown the retinal mechanisms of defocus detection. This study evaluated the electrophysiological response of the retina with two myopia control CLs, compared to single‐vision CLs.Methods: High‐contrast visual acuity (VA) and the retinal activity of 16 eyes (16 subjects, 27.5 ± 5.7 years, 12 female) with myopia (from −0.75 to −6.00 D, astigmatism &gt;1.00 D) were assessed with two single‐vision CLs (Omafilcon A – SVo – and Filcon 5B – SVf) and two myopia control CLs (dual‐focus – DF, Omafilcon A – and extended‐depth‐of‐focus – EDOF, Filcon 5B). The global‐flash multifocal electroretinogram (gf‐mfERG) was recorded with the Reti‐port/scan21 (Roland Consult) with a 61‐hexagons stimulus in physiological pupil conditions. The implicit time (milliseconds) and response density (nV/deg2) of the direct (DC) and induced (IC) components were compared between CLs of matching material.Results: All CLs showed similar VA (p &gt; 0.050). The implicit times did not show statistically significant differences. DF showed higher response density of both DC and IC components at all retinal areas, with a statistically significant difference in the parafoveal DC component (difference of 2.77 [6.23–1.44] nV/deg2, p = 0.038), compared with the SVo. EDOF showed a higher response density of about 13.31 [23.88–3.85] nV/deg2 (p = 0.032) in the foveal IC component, compared with the SVf. The remaining retinal areas did not show statistically significant differences.Conclusions: The retina seems to respond differently to distinct CL's optical designs. The two myopia control CLs increased the electrophysiological response of the retina, but with different effects, without affecting the implicit time of the response. Multifocal contact lenses with peripheral defocus induce different foveal and parafoveal activities that might be involved in the mechanism of myopia control.

Experimentally induced myopia and myopic astigmatism alter retinal electrophysiology in chickens

Myopia (or “short-sightedness”) and astigmatism are major causes of visual impairment worldwide. Significant amounts of astigmatism are frequently observed in infants and have been associated with myopia development. Although it is well established that both myopia and astigmatism are associated with ocular structural changes from anterior to posterior segments, very little is known on how these refractive errors alter retinal functions. This study investigated the effects of experimentally induced myopia and myopic-astigmatism on retinal electrophysiology by using an image-guided, multifocal global flash stimulation in chickens, a widely used animal model for refractive error development. Myopia and myopic-astigmatism were experimentally induced, respectively, by wearing spherical (− 10 D, n = 12) and sphero-cylindrical lenses (− 6.00 DS/− 8.00 DCx90: Hyperopic With-The Rule, H-WTR, n = 15; − 6.00 DS/− 8.00 DCx180: Hyperopic Against-The-Rule, H-ATR, n = 11) monocularly for a week (post-hatching day 5 to 12). An aged-matched control group without any lens treatment provided normal data (n = 12). Multifocal electrophysiological results revealed significant regional variation in the amplitude of induced component (IC) (central greater than peripheral; both p < 0.05) in the normal and H-ATR groups, but not in the – 10 D and H-WTR groups. Most importantly, for the first time, our results showed that both H-WTR and H-ATR groups exhibited a significantly longer implicit time of the inner retinal response at the central region when compared to the normal and – 10 D groups, highlighting a significant role of astigmatism in retinal physiology.

The effect of simultaneous dual-focus integration on the global flash multifocal electroretinogram in the human eye.

To investigate the effect of simultaneous dual-focus (DF) on retinal activities measured by global flash multifocal electroretinogram (mfERG). Thirty adults were recruited for mfERG measurement under three conditions: in-focus (i.e., no defocus), +2.50D DF and +7.50D DF, administered using single vision contact lenses and DF lenses. The direct component (DC) and the induced component (IC) of the mfERG were pooled into central macular (0-8°), para-macular (8-18°) and peri-macular (18-30°) regions, and then compared across the three conditions using two-way, repeated measures ANOVA. Simultaneous DF had a significant effect on the IC amplitude, which was significantly stronger under +7.50 D DF (p<0.01) than for the in-focus condition, which was mostly derived from the central and para-macular regions. No significant effect was observed for the +2.50 D DF condition. Under the effect of relatively strong simultaneous DF integration, the retina showed an enhanced retinal response, which originated from the inner retina. Compared with the peri-macular region, central and para-macular responses appeared to be enhanced.

Neuropeptide Y treatment induces retinal vasoconstriction and causes functional and histological retinal damage in a porcine ischaemia model.

To investigate the effects of intravitreal neuropeptide Y (NPY) treatment following acute retinal ischaemia in an invivo porcine model. In addition, we evaluated the vasoconstrictive potential of NPY on porcine retinal arteries exvivo. Twelve pigs underwent induced retinal ischaemia by elevated intraocular pressure clamping the ocular perfusion pressure at 5mmHg for 2hr followed by intravitreal injection of NPY or vehicle. After 4weeks, retinas were evaluated functionally by standard and global-flash multifocal electroretinogram (mfERG) and histologically by thickness of retinal layers and number of ganglion cells. Additionally, the vasoconstrictive effects of NPY and its involved receptors were tested using wire myographs and NPY receptor antagonists on porcine retinal arteries. Intravitreal injection of NPY after induced ischaemia caused a significant reduction in the mean induced component (IC) amplitude ratio (treated/normal eye) compared to vehicle-treated eyes. This reduction was accompanied by histological damage, where NPY treatment reduced the mean thickness of inner retinal layers and number of ganglion cells. In retinal arteries, NPY-induced vasoconstriction to a plateau of approximately 65% of potassium-induced constriction. This effect appeared to be mediated via Y1 and Y2, but not Y5. In seeming contrast to previous invitro studies, intravitreal NPY treatment caused functional and histological damage compared to vehicle after a retinal ischaemic insult. Furthermore, we showed for the first time that NPY induces Y1- and Y2- but not Y5-mediated vasoconstriction in retinal arteries. This constriction could explain the worsening invivo effect induced by NPY treatment following an ischaemic insult and suggests that future studies on exploring the neuroprotective effects of NPY might focus on other receptors than Y1 and Y2.

Subclinical Decrease in Central Inner Retinal Activity Is Associated With Myopia Development in Children.

To investigate the characteristics of retinal electrophysiological activity in relation to early myopia development in children. Fifty-six children aged 6 to 9 years with emmetropic refractive error (defined as ≥ -0.5 diopter [D] and ≤ +0.5 D) were recruited. Cycloplegic refraction, axial length, and global flash multifocal electroretinogram (MOFO mfERG) at 49% and 96% contrast levels were recorded in all children at their first visit. The refraction and axial length measurements were repeated after 1 year. The amplitudes and implicit times of the direct component (DC) and the induced component (IC) of the MOFO mfERG obtained at the initial visit were analyzed. Correlations between the MOFO mfERG parameters and changes in refractive error and axial length were investigated. The mean spherical equivalent refractive error and axial length of the eyes of the children at the first visit were +0.19 ± 0.33 D and 23.14 ± 0.6 mm, respectively. After 1 year, the mean refractive error increased by -0.55 ± 0.53 D, whereas axial length increased by 0.37 ± 0.22 mm. The changes in refractive error and axial length were significantly correlated with the central IC amplitudes at 49% contrast level measured at the initial visit (ρ = 0.46, P < 0.001 and ρ = -0.34, P = 0.01, respectively). The prospective changes we have shown are believed to derive from central inner retina. These changes appear to precede myopia and could be a potential reference for juvenile myopia development.

Myopia Progression in Children Is Linked with Reduced Foveal mfERG Response

To study the changes in retinal electrophysiology in children during myopia progression during a 1-year period. Twenty-six children aged from 9 to 13 years were recruited for the global flash multifocal electroretinogram (mfERG) measured at 49% and 96% contrast, in two visits 1 year apart. The amplitudes and implicit times of both direct component (DC) and induced component (IC) measured at these two visits were analyzed and compared. Pearson's correlation was used to study the association between the changes of mfERG response and myopia progression during the test period. Myopia increased by -0.48 ± 0.32 diopter (D) (P < 0.001) during the year, with 24 of 26 children becoming more myopic (range = 0.00 to ∼ -1.38 D); axial length increased by 0.25 ± 0.11 mm (P < 0.001) during the year. The increased myopia was highly correlated with increase in axial length (r = -0.70; P < 0.001). The central DC and IC amplitudes at 49% contrast reduced significantly as myopia progressed and the paracentral implicit times of these two components were reduced considerably. However, the high-contrast responses were virtually unaffected. Our findings suggested that the inner retinal functions in the central retina, with some involvement of the paracentral region, were decreased as myopia progressed in children.

Global flash multifocal electroretinogram: early detection of local functional changes and its correlations with optical coherence tomography and visual field tests in diabetic eyes

To investigate the correlations of the global flash multifocal electroretinogram (MOFO mfERG) with common clinical visual assessments--Humphrey perimetry and Stratus circumpapillary retinal nerve fiber layer (RNFL) thickness measurement in type II diabetic patients. Forty-two diabetic patients participated in the study: Ten were free from diabetic retinopathy (DR), while the remainder suffered from mild to moderate nonproliferative diabetic retinopathy. Fourteen age-matched controls were recruited for comparison. MOFO mfERG measurements were made under high- and low-contrast conditions. Humphrey central 30-2 perimetry and Stratus OCT circumpapillary RNFL thickness measurements were also performed. Correlations between local values of implicit time and amplitude of the mfERG components [direct component (DC) and induced component (IC)], and perimetric sensitivity and RNFL thickness were evaluated by mapping the localized responses for the three subject groups. MOFO mfERG was superior to perimetry and RNFL assessments in showing differences between the diabetic groups (with and without DR) and the controls. All the MOFO mfERG amplitudes (except IC amplitude at high contrast) correlated better with perimetry findings (Pearson's r ranged from 0.23 to 0.36, p < 0.01) than did the mfERG implicit time at both high and low contrasts across all subject groups. No consistent correlation was found between the mfERG and RNFL assessments for any group or contrast conditions. The responses of the local MOFO mfERG correlated with local perimetric sensitivity but not with RNFL thickness. Early functional changes in the diabetic retina seem to occur before morphological changes in the RNFL.

Early local functional changes in the human diabetic retina: a global flash multifocal electroretinogram study

To investigate early functional changes of local retinal defects in type II diabetic patients using the global flash multifocal electroretinogram (MOFO mfERG). Thirty-eight diabetic patients and 14 age-matched controls were recruited. Nine of the diabetics were free from diabetic retinopathy (DR), while the remainder had mild to moderate non-proliferative diabetic retinopathy. The MOFO mfERG was performed at high (98%) and low (46%) contrast levels. MfERG responses were grouped into 35 regions for comparison with DR classification at those locations. Z-scores of the regional mfERG responses were compared across different types of DR defects. The mfERG waveform consisted of the direct component (DC) and the induced component (IC). Local reduction in DC and IC amplitudes were found in diabetic patients with and without DR. With increasing severity of retinopathy, there was a further deterioration in amplitude of both components. Under MOFO mfERG paradigm, amplitude was a useful screening parameter. The MOFO mfERG can help in detecting early functional anomalies before the appearance of visible signs, and may assist in monitoring further functional deterioration in diabetic patients.

The Cellular Origins of Chick Global Flash Multifocal Electroretinogram

Purpose:The aim of this study was to obtain a better understanding of the cellular contributions to the chick global flash mfERG by using a pharmacological dissection method.Method:Global flash mfERGs were recorded from 11 white leghorn chicks (Gallus gallus). The inner retinal response was suppressed by injection of tetrodotoxin (TTX) and N-methyl-D-aspartic acid (NMDA). Responses from ON- and OFF-pathway were isolated by further injection of 2-amino-4-phosphonobutyric acid (APB).Results:The global flash mfERG of white leghorn chicks consist of a direct component (DC) originated from outer retina and a late induced component (IC) originated from the inner retina which are comparable to the global flash mfERG responses from primate, porcine and human. The ON- and OFF- responses found in chicks are also similar to that of porcine and primate with the N1 component is mainly from OFF-bipolar responses and the ON-response contributes mainly in the P1 component.Conclusion:Because of the similarities for the global flash mfERG found in chick to other species, this makes the possibility of using chick retina as a potential animal model for eye research in the area of mfERG.

Impairment of retinal adaptive circuitry in the myopic eye

Previous studies have proposed that the inner retina is affected in myopes. This study aimed to investigate the changes in adaptive circuitry of the inner retina in myopia, using the global flash multifocal electroretinogram (global flash mfERG) with different levels of contrast (luminance modulation). Fifty-four myopes had global flash mfERG recorded with different contrasts. The direct component (DC) and the induced component (IC) of the mfERG response were pooled into six regions for analysis. The response amplitudes and implicit times at different contrasts were also analysed. Results showed that myopes had significant reduction in the paracentral DC amplitude for the 29% and 49% contrasts and in the paracentral IC amplitude at all contrasts measured. The peripheral IC amplitude for the 49% contrast was also reduced. No significant change was found in implicit time for either DC or IC response. Refractive error explained about 14% of the variance in DC and 16% of the variance in IC amplitude respectively; axial length could not account for additional variance in either paracentral DC or IC amplitudes in the hierarchical regression models used. We concluded that the paracentral retinal region in myopes showed signs of impaired retinal adaptation, suggesting a functional loss at the inner retinal layer. In addition, functions attributed to the outer retinal layer showed only small changes due to myopia.

Effects of luminance combinations on the characteristics of the global flash multifocal electroretinogram (mfERG)

This study aims to ascertain the characteristics of the response triggered by the global flash multifocal electroretinogram (MOFO mfERG) under various combinations of global and focal flash luminance, and to determine the optimal conditions for this measurement. Ten normal subjects with mean age 23.2 yrs (+/- 1.14 yrs) were recruited for the MOFO mfERG measurement. The visual stimulation consisted of four video frames (stimulus frame with 103 scaled hexagonal focal flashes, followed by a dark frame, a global flash and then another dark frame). The focal and global flash intensities were varied independently for four levels (50, 100, 200 and 400 cd/m(2)). The subjects then underwent measurements with sixteen combinations of focal and global flash luminance. The direct component (DC) and induced component (IC) of the MOFO mfERG were grouped into central and peripheral regions for analysis. The central and peripheral DC amplitude increased with the focal flash luminance under constant global flash luminance. Moreover, the proportion of the global flash and focal flash intensity was shown to be important to achieve an optimal IC response. When the ratio of global flash luminance to focal flash luminance (g/f ratio) was kept at about 2:1, the central and peripheral IC amplitude reached the peak value, and further increasing the global flash luminance would not enhance the IC response magnitude. The implicit time of both central and peripheral DC generally decreased with the increase of g/f ratio. However, the implicit time of central and peripheral IC increased with the g/f ratio. The g/f ratio is important in the MOFO mfERG paradigm, since the DC and IC responses change with this ratio. In order to obtain both optimal DC and IC responses, a g/f ratio of 1:1 with focal flash luminance between 100 cd/m(2) and 200 cd/m(2) would be recommended. As the global flash mfERG paradigm is studying the interaction triggered by both flashes, the g/f ratio is a vital parameter for measurement in future studies.

Porcine global flash multifocal electroretinogram: Possible mechanisms for the glaucomatous changes in contrast response function

Purpose The aim of this study was to obtain a better understanding of the cellular contributions to the porcine global flash mfERG by using a pharmacologic dissection method, together with the method using variation of stimulus contrast which has been used to demonstrate mfERG changes in human glaucoma. Methods Global flash mfERGs with different stimulus-contrast settings (99%, 65%, 49% or 29%) were recorded from 14 eyes of ten 6-week-old Yorkshire pigs in control conditions and after suppression of inner retinal responses with inhalation of isoflurance (ISO), and injections of tetrodotoxin (TTX) and N-methyl- d-aspartic acid (NMDA). ON- and OFF-pathway responses were isolated by injection of 2-amino-4-phosphonobutyric acid (APB) and cis-2,3-piperidinedicarboylic acid (PDA). Results The porcine global flash mfERG consisted of an early direct component (DC) and a late induced component (IC). ISO and TTX removed inner retinal contributions to the IC; NMDA application further abolished the oscillatory wavelets in the DC and removed the residual IC waveform. The inner retina contributed regular oscillation-like wavelets (W1, W2 and W3) to the DC and shaped the IC. After removing the inner retinal contributions, the porcine global flash mfERG waveform becomes comparable to that obtained with conventional mfERG stimulation. The remaining waveform (smoothed DC) was mainly contributed by the ON- and OFF-bipolar cells as revealed after APB or PDA injection. Photoreceptors contributed a small signal to the leading edge of N1. The characteristic of contrast response function of DC was demonstrated to be contributed by the inner retinal oscillation-like wavelets. Conclusion We believe that the DC of the porcine global flash mfERG is mainly composed of contributions from photoreceptors, and ON- and OFF-bipolar cells, where inner retinal activity partially shaped the DC with superimposed regular wavelets. However, the IC is dominated by inner retinal activity. The contrast response functions of DC consisted of both outer retinal response and oscillation-like wavelets of the inner retinal response. Both contain different characteristics during contrast modulation of the stimulus, where the changes of W2 of the inner retinal response seem independent of contrast modulation. The DC contrast response feature depends mainly on the relative contribution of inner retinal activities; the loss of inner retinal cells may alter the DC contrast response function, making it tend toward linearity.

Luminance-Modulated Adaptation of Global Flash mfERG: Fellow Eye Losses in Asymmetric Glaucoma

To use the global flash multifocal electroretinogram (mfERG) in patients with asymmetric glaucoma to determine whether retinal function is affected in fellow eyes that have no glaucomatous visual field defects. Forty normal subjects and 12 patients with asymmetric glaucoma were recruited for visual field and mfERG measurement. The mfERG was assessed by using a global-flash stimulation paradigm with four video frames: 103 scaled hexagonal elements followed by a dark frame, a global-flash frame, and a dark frame. The localized luminance difference was set at 96%, 65%, 49%, and 29% display contrast during the four different test conditions, respectively. The first-order kernel response was measured, and the "adaptive index" which has been used previously was calculated. In fellow eyes with normal visual fields, the amplitude of the induced component (IC) was significantly reduced, and the adaptive index was reduced by a factor of almost 10 (P < 0.0001), as it was in the glaucomatous eyes. Although the adaptive index in the better (fellow) eye of the patients with glaucoma was slightly higher than in the eyes with diagnosed glaucoma, these differences were not statistically significant. The significant reduction of the adaptive index in the better eyes in subjects with asymmetric glaucoma shows that the fast adaptive mechanism(s) were reduced in these eyes. This implies that eyes that have functionally normal visual acuity and visual fields have abnormal fast-adaptive mechanisms.

Retinal adaptation responses revealed by global flash multifocal electroretinogram are dependent on the degree of myopic refractive error

Purpose There is evidence that the inner retina is involved in eye growth control processes and the development of myopia. We sought to investigate the response dynamics of the inner retina of adult emmetropes and myopes using the global flash multifocal electroretinogram (mfERG) paradigm. Methods Fourteen myopes and 10 emmetropic subjects (mean age: 21.0 ± 2.8 years) underwent mfERG testing using VERIS 5.1.5X. The global flash stimulus array consisted of 103-scaled hexagons which flickered according to a pseudorandom binary m-sequence (2 13 − 1). The stimulation sequence was modified by inserting three frames, a dark frame, a global (full screen) flash, and another dark frame. The amplitude and implicit time of the two distinct waveform features, an early direct component (DC) and a later induced component (IC) of the first-order kernel were analyzed. Retinal responses were averaged over rings of increasing eccentricity, or into nasal and temporal hemifields. Results There was a significant correlation between the DC and IC response amplitude and myopic refractive error, i.e., the greater the myopic error, the greater the response amplitude. However, when comparing between the two refractive error groups, DC and IC response amplitudes of emmetropes and myopes were similar, even after compensating for the effect of axial length. There were no significant differences in implicit times of the DC and IC in emmetropes and myopes. Conclusions Global flash mfERG responses of emmetropes and myopes were not found to be significantly different. The measured retinal adaptation response however varied according to the degree of myopia. We hypothesize that dopamine, a neurotransmitter that plays a key role in retinal adaptation and is known to be reduced in myopic eyes, may be involved in the retinal adaptation effect observed.

Glaucoma Detection Is Facilitated by Luminance Modulation of the Global Flash Multifocal Electroretinogram

To investigate the variation of retinal electrophysiological function in glaucoma by using the global flash multifocal electroretinogram (mfERG) stimulation with altered differences in the stimulus luminance of the multifocal flashes, in an attempt to alter the levels of inner retinal contributions. The mfERG was assessed with a visual stimulus in steps of four video frames, which consisted of 103 scaled hexagonal elements followed by a dark frame, global flash, and dark frame. The localized luminance difference was set at 96%, 65%, 49%, or 29% stimulus contrast. Thirty subjects with glaucoma and 30 age-matched normal subjects were recruited for visual field and mfERG measurements. This stimulus induces complex local first-order responses with an early direct component (DC) and a later induced component (IC). The luminance-modulated response functions of the DC and IC responses showed markedly different behavior. The peripheral IC showed a linear dependence on luminance difference, whereas the peripheral DC was saturated for higher luminance differences. This saturation became less obvious in subjects with glaucoma, mostly because of greater reduction of the response amplitude in the mid luminance-difference level. An "adaptive index" was calculated from the luminance-difference dependence of the peripheral DC, and it showed a sensitivity of 93%, with a specificity of 95% for differentiating normal from glaucomatous eyes, and also had a significant correlation (r = 0.58) with the glaucomatous visual field defect. The peripheral DC luminance-modulated response function is altered by the adaptive mechanism that is induced by the global flash; the reduction of the adaptive index may thus relate to an abnormal adaptive mechanism, presumably due to inner retinal damage. Glaucoma appears to produce large reductions of the adaptive index which correlate with field defects.

Adaptation Responses in Early Age-Related Maculopathy

To investigate the global-flash multifocal electroretinogram (mfERG) in early age-related maculopathy (ARM). Thirty-two eyes from 20 healthy control subjects and 12 age-matched subjects with early ARM were investigated with the conventional and the global-flash mfERG. Early ARM subjects were graded according to an international grading system. The conventional mfERG consisted of 103 hexagons flickering according to a pseudorandom m-sequence. The global-flash mfERG paradigm used four frames starting with the conventional m-sequence stimulation, followed by a dark frame, a global flash, and another dark frame. The responses include a direct response (DR) and a later induced component (IC). The first-order kernel peak-to-trough response densities of the conventional mfERG (N1P1), the global-flash DR and IC, and the implicit times of the conventional P1, global-flash DR, and IC peak were analyzed after averaging the results into five groups according to five field locations: a central area and four quadrants. There was a significant reduction of the global-flash mfERG DR response density (P < or = 0.05) in the early ARM group compared with the control group. Neither the IC response density nor DR and IC implicit times were significantly impaired. However, the superior retina showed longer implicit times than did the inferior retina for the DR in the early ARM group. There was no significant correlation between funduscopic features and the central averaged responses of the global-flash mfERG (for the DR response density: r = -0.19, P = 0.3, or for the DR implicit time: r = -0.18, P = 0.3). None of the conventional mfERG parameters was significantly different between the two groups. The global-flash mfERG detects deficits in early ARM before the conventional mfERG. Retinal ischemia may play a role in producing function impairment in ARM.