Mikki Arai

Comparison of Snellen acuity and objective assessment using the spatial frequency sweep PVER

Abstract• Background: We compared the vision objectively assessed by spatial frequency sweep pattern-reversal visual-evoked response (SPVER) with the Snellen acuity in patients. • Methods: SPVER acuity and Snellen acuity were measured in 100 patients with various ocular pathologies, including macular diseases, diffuse retinal degeneration, optic nerve diseases, glaucoma, and high myopia. For SPVER, 10 sinusoidally modulated vertical gratings were presented as stimuli. The responses were averaged and displayed through the discrete Fourier transform on the monitor display. The PVER acuity was determined by extrapolating the SPVER amplitude-spatial frequency function to baseline. • Results: Vision ranged from 20/15 to 20/400 with Snellen acuity, and from 20/25 to 20/190 with SPVER. The overall correlation between the two acuities wasr=0.666. The correlation varied fromr=0.895 in eyes with glaucoma tor=0.436 in eyes with optic nerve disease. Seventy-seven eyes (77%) had a visual acuity agreement of within 1.0 octave between the two measurements. • Conclusion: The SPVER acuity and the Snellen acuity correlated to a certain degree. Discrepancies were found in certain diseases, with the highest disparity in patients with optic nerve disease. We conclude that the SPVER is effective in estimating vision objectively, particularly in patients in whom the standard Snellen test is impossible to perform or yields unreliable results.

Multifocal electroretinogram indicates visual field loss in acute zonal occult outer retinopathy

PURPOSE To report alterations of electrophysiologic tests, including the multifocal electroretinogram, in a case of acute zonal occult outer retinopathy. METHOD We recorded photopic, scotopic, and single-flash electroretinograms and a multifocal electroretinogram in a 47-year-old woman with acute zonal occult outer retinopathy in the right eye. RESULTS Her visual acuity was 20/20 in the right eye throughout the follow-up period. The electroretinograms indicated retinal impairment of the right eye, predominantly in the cones. The multifocal electroretinogram showed reduced responses corresponding to the visual field defect of the static perimetry. CONCLUSIONS In acute zonal occult outer retinopathy, impairment of the retinal area results in a visual field defect. The multifocal electroretinogram can be useful in determining the location of the defect.

Multifocal Electroretinograms in Normal Subjects

Multifocal electroretinography (ERG), developed by Sutter in 1992, is a method of recording the spatial distribution of focal ERG in a short time period using multi-input stimulation. Using this technique, we can detect the spatial extent and severity of damage to the macula. In this study, we recorded multifocal ERGs from 20 eyes of 20 normal subjects and analyzed the topographical properties of responses. In every subject, a negative wave followed by a positive wave could be recorded and we named them the N1-wave and the P1-wave, respectively. The amplitudes of the N1-wave and the P1-wave were the largest in the fovea, and they became smaller with eccentricity. In the P1-wave amplitude, the greatest intersubject variability was observed at the fovea. The N1 and P1 latencies were shorter in the upper retina than in the lower retina. The amplitude was larger in the upper retina than in the lower retina, which suggests the functional superiority of the upper retina. There was no statistical difference in latency and amplitude between the nasal and the temporal retina. We found no statistical difference between the responses of the papillomacular bundle and those of the temporal retinal area. The mapping obtained by multifocal ERG was useful as objective perimetry.

Spatial frequency sweep pattern reversal VER acuity vs Snellen visual acuity: Effect of optical defocus

The effect of artificially induced image defocusing on visual acuities (VAs) measured by spatial frequency sweep pattern reversal visual evoked response (SPVER) and Snellen measurement was studied in six normal subjects. The steady-state SPVER was recorded using vertical gratings of 10 different spatial frequencies ranging from 0.52 to 30.36 c/deg. The SPVER acuity was compared with Snellen acuity (SA) measured under the same conditions of optical defocus. With moderate defocusing [< + 1.0 diopter (D), VA > 20/40], the SPVER acuities were equal to or poorer than the SAs. With more defocus (> + 1.5 D, VA < 20/70), the SPVER acuities became better than the SAs. The discrepancies between the SA and SPVER acuities may be the result of the influence of the parafoveal area on the SPVER at lower visual acuity levels.

Comparison of preferential looking acuity and pattern reversal visual evoked response acuity in pediatric patients

Abstract• Background: We compared the visual acuities obtained with preferential looking (PL), the most widely used method of pediatric vision assessment, with those obtained with the spatial frequency sweep pattern-reversal visual evoked response (SPVER). • Methods: Eighty patients (ages 1.5 months to 12 years) with various ocular pathologies pariticipated in this study. The PL acuity was determined using the up-and-down staircase procedure. The PVER was recorded with the spatial frequency sweep method using 10 spatial frequencies; the acuity was determined by placing the best-fit regression line on the descending slope of the PVER amplitude-spatial frequency function toward the higher spatial frequency to the baseline. • Results: The PL acuities ranged from 20/25 to <20/1600 (mean 20/155). The correlation between the two methods was good (r=0.847). Fifty-six patients (70%) had an acuity agreement within 1.0 octave. When the PL acuity was >20/128, it was on average better than the PVER acuity. When the PL acuity was lower, the PVER acuity was usually better. This tendency was marked when the visual acuities were very poor (y=0.552x+0.362). • Conclusion: The methods correlate well, although there is a dissociation of acuities in the presence of very low vision. PVER may be a useful addition to PL in assessment of vision in infants and young children.

Effects of stimulus blocking, light scattering, and distortion on multifocal electroretinogram.

PURPOSE To investigate how the multifocal electroretinogram (ERG) is altered in conditions of blocking, light scattering, or distortion of the stimulus that are seen in ocular pathologies. METHODS A central 40 degree-diameter stimulus pattern consisting of 61 hexagons was presented on a cathode ray tube monitor at a rate of 75 Hz according to the pseudo-random binary M sequence by the Veris computer program. Localized responses corresponding to each hexagon and ERG topographies were displayed on the computer screen. Central scotoma was simulated by blocking the central area of the stimulus, visual field constriction by blocking the outer area of the stimulus, mild cataract by using acrylic filters that caused light scatter, and epiretinal membrane by using a wavy plastic plate that produced metamorphopsia. RESULTS The responses from the blocked area were nonrecordable whether blockage was central or peripheral; responses from the adjacent unblocked area had a larger amplitude when large areas of the stimulus were blocked. The light scatter that decreased vision from 20/20 to 20/70 did not significantly decrease response amplitudes. Responses from areas in which the stimulus pattern was distorted were minimally affected. CONCLUSIONS The results show that the system records local ERGs from the macula and outside the macula. It can detect the area where the stimulus is blocked. Moderate light scattering and distortion do not cause loss of local ERG characteristics.

Objective measurement of contrast sensitivity function using contrast sweep visual evoked responses

AIM/BACKGROUND The contrast sensitivity function (CSF) measurement provides information that is not accessible by standard visual acuity determinations. The contrast sweep pattern reversal visual evoked responses (CSVER) technique was used to objectively measure the CSF in clinical practice. METHODS The contrast thresholds were measured at five spatial frequencies in 10 normal subjects. The CSVER were recorded with sinusoidally modulated vertical gratings at 10 contrast levels (96, 64, 48, 32, 16, 8, 4, 2, 1, and 0.5%) presented in five spatial frequencies (0.5, 1.0, 2.0, 4.0, and 8.0 cycles per degree). Each of 10 contrast levels was displayed for 2 seconds at the desired spatial frequency. The CSVER amplitudes at the second harmonic were calculated by discrete Fourier transform. The results were compared with those obtained using a psychophysical method. RESULTS An inverted U-shaped CSF which peaked at 2.0 cycles per degree with a contrast sensitivity of 34.5 (contrast, 2.9%) was observed. The CSF assessed electrophysiologically was 0.62 to 0.79 log units lower than the sensitivity measured using the psychophysical method. However, the overall shapes were highly correlated. CONCLUSION One can objectively measure CSF with CSVER and this may be useful in patients in whom the psychophysical method is limited.

Intraocular Use of Hydrogel Tissue Adhesive in Rabbit Eyes

PurposeTo evaluate the safety and efficacy of newly developed hydrogel glue to treat rhegmatogenous retinal detachments in in vitro and in vivo studies.MethodsIn the in vitro study, the solid hydrogel glue was soaked in a balanced salt solution (BSS). The pH was measured periodically, and the dissolution time was recorded. In the in vivo study in six albino rabbits, 0.1 ml of hydrogel glue was injected into the right vitreous cavity, and 0.1 ml BSS was injected into the left vitreous, as the control. Clinical, electroretinography (ERG) and histological examinations were performed. Retinal detachment with a retinal hole was created in 12 albino rabbits after vitrectomy. After fluid–air exchange, the hydrogel glue was applied to the hole in nine rabbits; three other rabbits were used as controls. Clinical and histological examinations were performed.ResultsThe pH ranged from 6.65 to 8.14. The glue remained solid in BSS for 7 weeks. The glue injection did not induce inflammation. There was no significant difference between the study and control eyes in the ERG amplitude or the implicit times of the a and b waves. No significant histological abnormality was detected. The retina was reattached with glue in three of nine eyes. The histological examination showed glue under the retina.ConclusionsHydrogel glue, which seemed to be minimally toxic to the eye, can be used to patch retinal breaks. However, methods to mix a small amount of each solution completely and a more effective intraocular delivery system for the glue are needed. Jpn J Ophthalmol 2007;51:89–95

In Vivo and In Vitro Feasibility Studies of Intraocular Use of Polyethylene Glycol-Based Synthetic Sealant to Close Retinal Breaks in Porcine and Rabbit Eyes.

PURPOSE Absorbable polyethylene glycol-based synthetic sealant (PEG sealant) polymerizes under xenon illumination and forms a clear, flexible, and firmly adherent hydrogel. The intraocular biocompatibility of PEG sealant and efficacy for closing retinal breaks were evaluated. METHODS In an in vitro study, retinal detachment with a tear was created in porcine eyecups after vitreous gel removal. Polyethylene glycol-based synthetic sealant was applied to cover the tear and polymerized with a 40-second application of xenon light. Retinal adhesion strength was tested by forcefully squirting balanced salt solution (BSS) onto the retinal tear. Polyethylene glycol-based synthetic sealant was soaked in the BSS, incubated at 37°C, and the pH measured periodically over 72 hours. In an in vivo study, PEG sealant was injected into the vitreous cavity of the left eyes of rabbits. Ophthalmologic examinations were performed and bilateral ERGs were recorded simultaneously before and 28 days after injection. The eyes were enucleated for histological evaluation. RESULTS Adhesion of PEG sealant to the retina was good in BSS. A forceful squirt of BSS onto the retinal tear covered with PEG sealant did not detach the retina; the retinal tear without PEG sealant detached immediately. The pH of the BSS containing PEG sealant was between 7.2 and 8.2. No inflammatory reaction was observed in the eyes throughout 28 days of follow-up. The ERGs recorded before and after injection showed typical patterns. Histological examinations did not reveal any abnormality or inflammation. CONCLUSIONS Polyethylene glycol-based synthetic sealant appeared to effectively seal retinal breaks and was not toxic to the eye.

Multifocal electroretinograms in Stargardt's disease/fundus flavimaculatus.

Purpose: To determine whether the characteristics of multifocal electroretinograms (mfERGs) were correlated with the ophthalmic appearance of the fundus in patients with Stargardts disease/fundus flavimaculatus (SFF). Methods: Full-field ERGs, mfERGs, and general ophthalmic examinations were performed on 49 eyes with SFF. Results: The SFF patients were divided into four subtypes according to the classification of Noble and Carr [Arch Ophthalmol 1979;97:1281-1285]. The patients with type 1 SFF had severely reduced mfERGs in the macular area and reduced and delayed responses in the mid-periphery. The type 2 SFF patients had reduced but recordable mfERGs from the center of the macula with more depressed responses in the paramacular area, and the type 3 SFF patients had reduced and delayed mfERGs both in the macula and periphery. The patients with type 4 SFF had normal mfERGs in the macular area and delayed responses in all outer zones. Conclusions: These mfERG findings indicate that each subtype of SFF has unique characteristics corresponding to the abnormal retinal functions.