Neurovisual abnormalities preceding the retinopathy in patients with long-term type 1 diabetes mellitus.

BACKGROUND: Changes in the retina caused by diabetes may lead to visual impairment in dim light, even with good visual acuity and visual fields. To evaluate the visual abnormalities preceding the retinopathy in patients with type 1 diabetes mellitus (DM), we applied electrophysiological methods. METHODS: The visual evoked responses were recorded with sinusoidally modulated vertical gratings at 10 spatial frequencies presented sequentially on a high-resolution monitor in patients with type 1 DM and in normal volunteers. Similarly, the contrast visual evoked responses of 10 contrast levels were recorded at five spatial frequencies. Both amplitudes at the second harmonic were calculated by discrete Fourier transform. The visual acuity and contrast thresholds were determined objectively. RESULTS: There was dissociation between the Snellen and the estimated visual evoked response acuity measurements in patients with diabetes (r2=0.077, P=0.44). The saturation phenomena were observed at lower levels of contrast stimuli than in normal individuals at. 1.0, 2.0, 4.0 and 8.0 cycles per degree (P=0.0001). The contrast sensitivity function was deeply abnormal in all tested patients despite the metabolic control. The values of the area under the curve of the visual evoked response amplitude-contrast level function at five spatial frequencies were smaller in patients with DM than in the control group (P<0.05) at all spatial frequencies tested. CONCLUSIONS: Patients with type 1 DM without retinopathy showed significant lower amplitude of the visual evoked responses at all spatial frequencies tested, with the saturation phenomena observed at lower level of contrast stimuli. In addition, there was a dissociation between the sweep visual evoked responses and the Snellen acuity measurements. A significant and nonselective neuronal visual loss involving the visual pathway precedes the ophthalmoscopically detectable retinopathy in patients with type 1 DM.

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.

Visual Ability Score -- a new method to analyze ability in visually impaired children.

PURPOSE: We analyzed the correlation between the Preferential Looking (PL) acuities and the Visual Ability Scores (VAS) of 600 patients (many with severe retinopathy of prematurity) to determine their ability to perform various activities within the daily environment. METHODS: Visual acuity was measured by PL. Sixteen visual activities within the environment were analyzed. The VAS (range, 1-16) were calculated from the results of each activity and correlated with PL acuity. RESULTS: The PL acuities of the 600 patients ranged from 20/20 (1.0) to <20/3200 (0.006) [mean, 20/337(006)]. The VAS ranged from 1 to 16 points (mean, 10.65; SD, +/-4.80) and showed a high correlation with the PL acuities (r=0.917, p=0.0001). CONCLUSIONS: In addition to PL vision testing, analyzing the environmental visual behavior of young, severely visually impaired patients is important to accurately evaluate visual abilities. We found the VAS to be an important aid for low-vision specialists, especially for those with no access to a vision evaluation system such as PL.

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

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 was r = 0.666. The correlation varied from r = 0.895 in eyes with glaucoma to r = 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.

Five years' experience with the Grating disc. A simplified method of evaluating vision in young children.

The Grating Disc (GD) is a simplified visual test designed for children 18 months to 4 approximately 5 years. Two hundred pediatric patients (103 males, 97 females; aged 5 months to > 6 years) participated in this study to determined how the GD visual acuity (VA) correlates with the Preferential Looking (PL) VA. Forty-six percent of the patients had varying degrees of retinopathy of prematurity. The PL acuity was determined using the up-and-down staircase procedure. To measure GD acuity, six GDs with vertical gratings equivalent to acuities of 20/1920 to 20/60 were used. The examiner presented one GD simultaneously with the homogeneous disc from 57 cm. The VA was determined by the finest GD that the child could differentiate from the homogeneous disc. The overall correlation between the PL and the GD acuities was very high (R2 = 0.861). One hundred twenty-eight patients (64.0%) had an acuity agreement within 0.5 octave and 178 (89.0%) patients were within 1.0 octave. When the PL acuity was > or = 20/100, the GD and PL acuities showed good agreement. When the PL acuity was poorer, the GD acuity was poorer than the PL acuity. Although the GD acuity tended to be lower than the PL acuity in severely visually impaired patients, the GD acuity agreed with the PL in most visual assessments of young children. GD testing could be a useful alternative when sophisticated assessment systems such as the PL are unavailable.

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

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 participated 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.

Spatial tuning loss of pattern reversal visual evoked response in optic nerve disease.

We compared the pattern reversal visual evoked response (PVER) amplitude-check size functions from 25 eyes (25 normal subjects; visual acuities > or = 20/20) with those from 32 eyes (22 patients; visual acuities 20/15 to 20/50; mean, 20/25.5) with mild optic nerve disease to determine if spatial tuning loss of the PVER occurs in the presence of optic nerve dysfunction. The steady-state PVER was recorded with five check sizes (range, 160 to 10 minutes of arc). To analyze the PVER amplitude-check size function, we calculated the difference between the maximum and minimum PVER amplitudes and then calculated the area of spatial tuning (the area under the function). Values were significantly smaller in patients than in normal subjects (1.81 +/- 1.27 microV versus 5.73 +/- 3.27 microV; F = 41.24, p = 0.0001; 3.87 +/- 2.70 area units versus 12.57 +/- 7.60 area units; F = 38.62, p = 0.0001). There was no shift in the distribution of peak check sizes. Results suggest that a spatial tuning loss occurs in optic nerve disease. The shape of the function, including the area of spatial tuning, appears to be a sensitive indicator of early or mild optic nerve dysfunction.

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.

Tonometry in pediatric patients: a comparative study among Tono-pen, Perkins, and Schiötz tonometers.

Measuring the intraocular pressure (IOP) in children can be difficult. We compared the accuracy of IOP measurements in pediatric patients using three tonometers: Perkins, Schiötz, and Tono-pen. Seventy-seven children (132 eyes; average age, 1 year, 7 months; range, 1 month to 60 months), mainly afflicted with retinopathy of prematurity (107 eyes), were evaluated. A good correlation (r = 0.867) was found between the Tono-pen and the Perkins tonometers. No statistical difference was found between the mean difference of IOP values obtained with the Tono-pen and the Perkins (P > .05). The Schiötz measurements were significantly higher than those obtained with the Perkins and the Tono-pen tonometers (P < .05). We concluded that the Tono-pen tonometer has a higher correlation coefficient, comparable to the Perkins tonometer, and can be used reliably to assess IOP in pediatric patients.

Correlating preferential looking visual acuity and visual behavior in severely visually handicapped children.

We developed a series of questions that reflects the functional abilities of severely visually handicapped children. The study population comprised 100 patients aged 30 to 60 months (mean 43.23), mostly afflicted with retinopathy of prematurity. Visual acuity was measured by preferential looking. Preferential looking acuities of the patients ranged from 20/25 (0.8) to 20/6400 (0.003) (mean 20/470 (0.04)). Ten activities were analyzed and correlated with preferential looking acuity. Among the selected visual activities, when children are not interested in television (p = 0.0001), toys (other than those that make sounds (p = 0.0001), and people (p = 0.001)), their preferential looking acuities were very low. For example, 73 out of 100 patients who were visually interested in television had preferential looking acuities (mean 20/245 (0.082)) that were significantly higher (p = 0.001) than 21 patients not interested in television (mean 20/2806 (0.007)). Patients with nystagmus (n = 79) had significantly lower preferential looking acuities (p = 0.0001) (mean 20/1114 (0.018)) than patients with no nystagmus (mean 20/57 (0.35)). When evaluating visual function in young, severely visually impaired patients, in addition to preferential looking testing, analyzing visual behavior within the environment is important to accurately evaluate their remaining visual abilities.

Contrast visual acuities in cataract patients. III. Changes of contrast acuity profiles in normal and pathological eyes.

We compared pre- and postoperative visual acuities in 45 cataract patients without ocular pathology except lens opacity (group 1) and 20 patients with ocular pathologies and lens opacity (group 2) using Variable Contrast Visual Acuity Charts. Charts 1 and 4 have 90% contrast; chart 4 has white optotypes on a black background (reverse polarity), charts 2 and 3 have 15% and 2.5% contrast, respectively. The mean preoperative visual acuities of groups 1 and 2 measured with the high-contrast Landolt optotypes ranged from 0.02-0.80 and 0.22-0.40, respectively. Visual acuity improvements between the pre- and postoperative periods ranged from 1.37-1.61 and 0.52-1.24 octaves in groups 1 and 2, respectively, with the different charts. Visual acuity improvement was poorest with chart 3. The group 1 mean preoperative visual acuity measured with chart 2 was 1.11 octaves lower than with chart 1. In group 2, the visual acuity reduction was 1.81 octaves. The relation between the visual acuities measured with the high-contrast intermediate-contrast optotypes are important for predicting postoperative visual acuity improvement. An abnormal contrast acuity profile may indicate the presence of additional ocular pathologies.

Pattern-reversal visual-evoked response in bull's eye maculopathy associated with Stargardt's disease.

Using steady-state pattern-reversal visual-evoked response (PVER), we studied the macular function in patients with bull's eye maculopathy. The results were correlated with fluorescein angiography. Study patients with an established (25 eyes of 14 patients) and a suspected (8 eyes of 4 patients) diagnosis of Stargardt's disease with bull's eye maculopathy were divided into group G (good vision group: 15 eyes with visual acuity of 20/40 or better) and group P (poor vision group: 18 eyes with visual acuity of 20/50 or worse). The diameters of the atrophic area and the normal or less affected central area of the bull's eye were measured form the fluorescein angiograms. The mean diameter of the central area in group G (2.0 degrees) was significantly larger than that in group P (0.6 degrees; d.f. = 17, p = 0.0227). The PVER amplitudes were reduced in the patient groups with all check sizes and the amplitude-check size functions were flat. Amplitude differences were observed between the patient groups with the 20' checks (d.f. = 17, p = 0.0638), probably due to the difference in the mean central diameters (2.0 degrees vs. 0.6 degrees). Patients with a perifoveal abnormality can have an abnormal PVER despite relatively good visual acuity. We also recorded the PVER in 7 normal controls tested with simulated ring-shaped scotomas, the sizes of which matched the mean diameters of the scotomas in the patient groups (7.0 degrees x 0.6 degrees and 7.0 degrees x 2.0 degrees). The controls also showed markedly reduced responses with all check sizes.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation of electroretinographic and fluorescein angiographic findings in unilateral central retinal vein obstruction.

BACKGROUND: In central retinal vein obstruction (CRVO), electroretinogram (ERG) abnormalities and extensive retinal capillary dropout (CD) in the fluorescein angiogram (FA) are good indicators of retinal ischemia. We retrospectively studied patients with unilateral CRVO and compared the ERG and FA results. METHODS: Single white flash ERG, photopic ERG, scotopic ERG and flicker ERG were recorded in 30 cases of unilateral CRVO. We analyzed the correlation between the ERG results and the presence/absence of extensive CD. RESULTS: The ERG b/a-wave amplitude ratios, photopic and scotopic b-wave amplitudes, and flicker amplitudes were significantly smaller (P < 0.05) in eyes with extensive CD (n = 12, 40%), than in eyes without (n = 18, 60%). When the photopic or scotopic b-wave amplitudes were normal or supernormal, extensive CD on FA was absent in all eyes. When the b/a-wave ratios were > or = 1.0 or when the b-wave amplitudes with white flash or flicker amplitudes were normal or supernormal, extensive CD was present in less than 32% of eyes. CONCLUSION: These results suggest that the ERG results, especially the b/a-wave amplitude ratio, are significantly correlated with the presence/absence of CD on FA in CRVO.

Pattern reversal visual evoked response and Snellen visual acuity.

Because the pattern-reversal visual evoked response (PVER) reflects the central retinal function, PVER results generally agree with those of psychophysical tests. The visual acuities (VAs) calculated from PVER recordings and Snellen acuity (SA) measurements were compared in 500 eyes (261 patients; ages 8 to 88 years; mean, 44.5 years). The best-corrected VA was measured using the ETDRS chart, and the PVER acuity was determined by the smallest check size that produced a definite PVER (critical check size). In 288 eyes with a critical check size of 10 min of arc, the SAs ranged from 20/15 to 20/800 (mean 20/38). In 68 eyes with a critical check size of 20 min, the SAs ranged from 20/15 to 20/800 (mean 20/97). In 70 eyes with a critical check size of 40 min, the SAs ranged from 20/20 to 20/1600 (mean 20/156). In 29 eyes with a critical check size of 80 min and 14 eyes with a critical check size of 160 min, the SAs ranged from 20/50 to 20/1600 (mean 20/312 and 20/398, respectively). In 31 eyes in which the PVER was non-recordable, the SAs ranged from 20/70 to 20/3200 (mean 20/1177). The PVER acuity using the smallest check size seemed to agree with the SA, but large deviations were observed in certain subjects.

Electroretinogram b/a wave ratio improvement in central retinal vein obstruction.

The electroretinogram (ERG), especially the b/a wave ratio, is considered a good indicator of retinal ischaemia in central retinal vein obstruction (CRVO). Seven CRVO patients who showed b/a wave ratio improvement from < 1.0 [negative type (-) ERG] to > or = 1.0 and one from 1.07 to 1.53 were studied. Three mechanisms of change were observed: firstly, the b-wave amplitude increased without an a-wave amplitude decrease (group A, n = 2); secondly, the b-wave amplitude increased with an a-wave amplitude decrease (group B, n = 4); and, thirdly, both decreased, but the a-wave amplitude decreased more markedly (group C, n = 2). In group A, the visual acuities improved markedly. In group B, the visual acuities improved in two cases in which the b-wave amplitude reached the normal range; the visual acuities did not improve in two cases in which the b-wave amplitude did not reach the normal range. In group C, the visual acuities remained poor. The negative (-) ERG or significantly reduced b/a wave ratio is associated with ischaemic CRVO and did not occur because of the filtering effect of the haemorrhage, which may reduce the stimulus light for the ERG. Improvement of the reduced b/a wave ratio with an increased b-wave amplitude was accompanied by improvements in fundus appearance and visual acuity in CRVO. The results suggest that the retinal ischaemia in CRVO, as revealed by the ERG and fluorescein angiogram, may be reversible in some cases.

Prognostic value of initial electroretinogram in central retinal vein obstruction.

We retrospectively studied the correlation between the initial electroretinogram (ERG) recordings and the final visual acuities (VA) of 47 patients with central retinal vein obstruction (CRVO) after follow-up of more than 1 year. The a- and b-wave amplitudes and the b/a ratio with white flash were significantly larger in patients with good vision (VA > 20/200) than in those with poor vision (VA < or = 20/200). The b/a ratio and b-wave amplitude with white flash showed sensitivity and specificity of more than 78% for visual prognosis. The latest VA was < or = 20/200 in all 20 patients with a subnormal b-wave amplitude and in all 15 with b/a ratio < 1.05. These results suggest that the ERG recorded soon after (CRVO) onset correlates strongly with visual prognosis.

Snellen visual acuity versus pattern reversal visual-evoked response acuity in clinical applications.

We compared the best-corrected Snellen acuity (SA) and the pattern reversal visual-evoked response (PVER) acuity in normal subjects and patients. Forty-two eyes of 42 normal subjects were controls; 457 eyes of 329 patients comprised the patient group. A steady-state stimulus with five check sizes ranging from 160 to 10 min in 1.0-octave steps was used. The PVER acuity was derived from the best-fit linear function relating the amplitude to the log-adjusted check size. Three intercepts of 0, 1 and 2 microV were used in both groups, and the PVER acuities were called P0, P1 and P2. The SAs in normal subjects ranged from 20/15 to 20/20 (mean, 20/18.3) and in patients from 20/15 to 20/1,600 (mean, 20/56.9). In normals, the P0 showed the best agreement with the SA (mean acuity difference, +0.34 octave). The SA and P0 agreed within +/- 2.0 octaves in 33/42 (78.6%) eyes. In patients, the P0 also showed the best agreement with the SA; 306/457 (67.0%) eyes showed an acuity difference within +/- 2.0 octaves. Unlike normals, 83/457 (18.2%) eyes showed an acuity difference > -3.0 octaves. These eyes mostly had optic nerve disease with a flattened PVER amplitude-check size function curve. The P0 seems to correlate better with SA than P1 and P2, but this analytical method may be less effective in the presence of certain pathologic conditions.

Stargardt's disease/fundus flavimaculatus: psychophysical and electrophysiologic results.

Retinal functions were analyzed psychophysically and electrophysiologically in 73 patients (146 eyes) with Stargardt's disease/fundus flavimaculatus. Patients were classified into types 1, 2, 3, and 4; patients with type 3 were subdivided into 3E and 3L (early and late onset of initial symptoms). Most had visual acuity (VA) of 20/200 or greater at initial testing. VA declined 0.25 octave/year during follow-up (mean, 6.1 years). Four of 16 patients (25%) older than 40 years had VA of 20/200 or less in the stronger eye. Psychophysical tests (flicker profile, central scotoma, dark adaptation) showed variable degrees of abnormalities. Electrophysiological tests showed significant photopic b-wave amplitude decreases, particularly in type 3E (42.2% of normal). The electro-oculogram light peak/dark trough ratio was abnormal in 60 of 132 eyes (45.5%), especially in type 3E (25 of 34 eyes, 73.5%). Visual prognosis and overall visual function varied depending upon disease type, location of retinal lesions, and age of onset. In Type 3E, overall retinal function was poorest and accompanied by the most severe decline of central vision and function in the surrounding macula.