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.

Effects of light scatter, defocusing, mean luminosity, contrast, and central scotoma on the PVER amplitude-check size function curve.

We analyzed the effects of various stimulus parameters, ie, light scatter, defocusing, mean luminosity, contrast, and central scotoma, on the normal pattern reversal visual evoked response (PVER), amplitude-check size function curve in six normal subjects. The steady-state PVER was recorded with five check sizes ranging from 160 to 10 min in 1-octave increments. The PVER amplitude, especially with the smaller check sizes, was markedly decreased by light scatter induced by acrylic sheets. The function curve quickly changed to a low pass filter shape when +2.0 diopters of defocus were added, with the decrease most marked in the small check sizes. When the mean luminosity was decreased, the function curve maintained its normal inverted-U shape up to 5 cd/m2, but the shape flattened with lower luminosity. Amplitude decreases were seen with all check sizes in low luminosity. With contrast changes from 95 to 24%, the function curve maintained its normal shape, but with slightly reduced amplitudes. The amplitude decrease was moderate even with the lowest contrast. With a two-degree central scotoma, the PVER amplitude was reduced more with the smaller than the larger check sizes. The function curve became somewhat flatter, with its peak shifting to the larger check sizes. Results indicated that the shape of the PVER amplitude-check size function curve changes in response to different modes of stimulation.

Measuring vision with temporally modulated stripes in infants and children with ROP.

PURPOSE: To determine differences in preferential looking (PL) acuities using stationary and temporally modulated stripe patterns in patients with various stages of retinopathy of prematurity (ROP). METHODS: We measured the PL acuities of 134 patients (ages 4 mo to 13 yr) with various stages of ROP. Patients were divided into six subgroups according to PL vision measured with stationary stripes: (1) equal to or better than 20/200 (n = 24); (2) worse than 20/200 to 20/400 (n = 10); (3) worse than 20/400 to 20/800 (n = 15); (4) worse than 20/800 to 20/1600 (n = 13); (5) worse than 20/1600 to 20/6400 (n = 26); and (6) worse than 20/6400 (n = 46; no stationary vision). RESULTS: In the group with PL acuity equal to or better than 20/200, no difference in vision was apparent between the two methods. In patients with acuities worse than 20/200 to 20/400, the temporally modulated PL acuities were 0.23 octave better than the PL acuities measured with the stationary stripes. The difference increased to 0.86 and 1.12 octaves in the groups with visual acuities worse than 20/400 to 20/800 and worse than 20/800 to 20/1600, respectively. The difference in the group with PL acuities worse than 20/1600 to 20/6400 was 1.69 octaves. The 46 patients with no stationary vision detected only the temporally modulated stripes. CONCLUSIONS: The results suggest that the PL acuity difference between the temporally modulated and stationary stripes increases with visual impairment. Measuring PL acuity with temporally modulated stripes is an important addition to the evaluation of severely visually impaired subjects.

Effect of hemifield stimulation on simultaneous steady-state pattern reversal electroretinogram and visual evoked response.

Steady-state pattern reversal electroretinograms (PERG) and pattern reversal visual evoked responses (PVER) were recorded simultaneously in 4 normal subjects using hemifield stimulation of the upper/lower and nasal/temporal conditions with 95 and 60% stimulus contrasts. A square-wave checker-board pattern (check size 40 min of arc) was used. The temporal frequency (reversal rate) was 6 Hz (12 reversals/s). With nasal/temporal hemifield stimulation, neither the PERG nor the PVER amplitudes differed significantly with either stimulus contrast. With the upper/lower hemifield stimulation, PERG amplitudes were not significantly different; PVER showed a significantly larger amplitude for lower than for upper hemifield stimulation with both contrasts (ANOVA test: p = 0.0064, 95% contrast; p = 0.0018, 60% contrast). PVER amplitudes recorded with lower hemifield stimulation were 2.05 and 2.63 times larger than those elicited with upper hemifield stimulation, for the 95 and 60% contrasts, respectively. The difference in response to the upper/lower hemifield stimulation, observed only in PVER, suggests that the lower stimulus field dominancy may be processed in a visual pathway proximal to the retinal level.

Visual hand display (VHD) as an introductory procedure for measuring vision in infants and young children with visual impairment.

We developed the Visual Hand Display (VHD) to measure vision in visually impaired infants and young children. The VHD is a circular fabric mitten, which is held easily by inserting the hand between the two surfaces. Black-and-white stripes are attached to one surface, 25, 15, 10, 4, and 2 mm per stripe. The VHD acuity is determined by the shortest test distance and the smallest stripes that the patient can detect. The VHD acuities were compared with preferential looking (PL) staircase acuities in 130 patients (53 males, 77 females; age range, 2 to 13 years; median, 21.0 months). Of these, 107 (82.3%) had various degrees of retinopathy of prematurity. The correlation between the VHD and the PL acuities was high (R2 = 0.849). PL acuities were better than the VHD acuities in 98/130 patients (75.4%), with an average difference of 0.51 (SD = 0.70) octave. The visual acuity differences were more pronounced in subjects with slight visual impairment and much less in subjects with severe visual impairment. The VHD seems to be an effective introductory method to evaluate visual acuity in severely visually impaired infants and young children. This method also would be effective with severely mentally and physically disabled patients who cannot undergo PL testing.

Effect of light scatter on the pattern reversal visual evoked response: comparison with psychophysical results.

The effect of light scatter on the pattern reversal visual evoked response (PVER) was studied in 6 normal subjects. The results were compared with contrast visual acuity, contrast sensitivity function, and glare disability. Light scatter was induced by translucent acrylic sheets. Visual acuity measured with the low-contrast charts decreased significantly (P < 0.0001) even with a small degree of light scatter. Contrast sensitivity decreased with a small degree of light scatter especially for high spatial frequencies. PVER amplitudes decreased especially at the smaller checks with its peak shifted to larger checks. PVER was equally sensitive to light scatter compared to psychophysical tests.

[A mechanism for reducing intraocular pressure in normal volunteers using UF-021, a prostaglandin-related compound].

The mechanism of reduction of intraocular pressure (IOP) and other ocular effects were studies after topical application of prostaglandin (PG) F2 alpha and UF-021, a new PG related compound, in eight normal volunteers. IOP, aqueous humor flow rate and outflow rate were evaluated during a period of four hours after the application. Both PGF2 alpha and UF-021 caused significant and similar IOP reduction for four hours. Neither compound produced any significant change in the aqueous humor flow rate or outflow rate, suggesting the increase of unconventional outflow rate as being the possible mechanism of IOP reduction in normal human eyes.

Effect of stimulus contrast on simultaneous steady-state pattern reversal electroretinogram and visual evoked response.

We studied the effect of stimulus pattern contrast on the simultaneously recorded pattern reversal electroretinogram (PERG) and pattern reversal visual evoked response (PVER) at 5 check sizes. The stimulus contrast ranged from 24 to 95% in 6 steps of 0.1- or 0.15-log unit increments. PERG amplitude showed a linear increase with an increase in pattern contrast at all check sizes. PVER amplitude showed an increase up to a certain pattern contrast, but was saturated upon further increase in stimulus contrast at all check sizes. The PERG amplitude-check size function curve showed a flattened, inverted-U shape only with the highest contrast and low-pass filter shape or flat shape with lower contrasts. The PVER amplitude-check size function curve showed an inverted-U shape (bandpass filter shape) at all contrasts. These characteristics to the changes in contrast and the spatial frequency tuning suggest that PVER is processed in a different location of visual pathway than PERG.

Development of vision in retinopathy of prematurity.

Serial measures (range, two to eight) of preferential-looking grating acuities of 52 infants with retinopathy of prematurity were made. Group 1 patients (n = 11), who had little or no macular displacement, had normal preferential-looking acuity except for two who had mild acuity deficits. None of the group 2 patients (n = 12), who had dragged maculas, ever had normal acuity. On the average, their acuities, which ranged from 1 to 6 octaves less than normal, gradually increased at a rate not significantly different from normal. Group 3 patients (n = 29), who had undergone open-sky vitrectomy, had significantly lower acuity despite reattachment of the retina.

Electrophysiological findings in peripheral uveitis.

Nine patients with peripheral uveitis were studied clinically and electrophysiologically. Electroretinographic findings varied widely from supernormal to nonrecordable responses, depending on the disease duration and severity. These results suggest that the pathology in peripheral uveitis is not necessarily limited to the inferior pars plana but can be diffuse and widespread. In the final stage of the disease, the fundus showed extensive pigmentation and narrow retinal arteries associated with a nonrecordable electroretinogram, similar to retinitis pigmentosa. Burned-out peripheral uveitis should be considered in the differential diagnosis of secondary pigmentary degeneration.