Aruna S. Rajagopalan

Visual Performance of Subjects Wearing Presbyopic Contact Lenses

Purpose. The purpose of this study is to assess the visual performance of subjects wearing gas-permeable (GP) multifocal contact lenses, soft bifocal contact lenses, GP monovision lenses and spectacles. Methods. The study included 32 subjects between the ages of 42 and 65 years wearing GP monovision, the Acuvue Bifocal (Vistakon), the Essentials GP Multifocal (Blanchard), and progressive addition lenses (PAL; spectacles group). There were eight subjects in each of these groups who were already wearing these modalities. Binocular low (18%) and high (95%) contrast acuities were recorded using the Bailey-Lovie chart; binocular contrast sensitivity from 1.5 to 18 cycles per degree (cpd) measured with the Vistech VCTS 6500 system, and monocular glare sensitivity at three luminance settings (400, 100, and 12 foot lamberts) was measured using the brightness acuity tester (BAT). Binocular near visual task performance (a modified version of letter counting method used in previous presbyopic studies) was also assessed. Results. For the contact lens-wearing groups, subjects wearing GP multifocals provided the best binocular high and low contrast acuity followed by soft bifocal wearers. There was relative parity between the binocular high and low contrast acuity with PAL and GP multifocal wearers. Monovision acuity, measured binocularly, was determined to be lower than the other three groups with this difference being most significant with high contrast acuity. Among contact lens-wearing groups, it was observed that GP multifocal lens wearers experienced the lowest amount of monocular disability glare followed by soft bifocal wearers and monovision wearers. Subjects wearing soft bifocal lenses and monovision demonstrated slightly reduced binocular contrast sensitivity at all spatial frequencies. In the contact lens groups, GP multifocal lens wearers had the highest binocular contrast sensitivity at all spatial frequencies, on parity with PAL wearers, except at the highest spatial frequency (18 cpd) at which PAL wearers had better vision. Error scores for the binocular near visual task performance between the four groups revealed subjects with GP multifocal lenses and PAL wearers to have the least errors, followed by monovision users and then soft bifocal wearers with the most errors. Conclusion. Subjects wearing GP multifocals, soft bifocals, monovision, and PAL spectacles have good binocular contrast sensitivity, satisfactory binocular low and high contrast acuity, and increased sensitivity to glare. Presbyopic subjects requiring the use of contact lenses under dim light levels could benefit from GP multifocal lenses. Contrast and glare sensitivity evaluations provide significant information regarding the visual performance of the presbyopic contact lenses and should be included in regular presbyopic contact lens fitting.

Fundus findings and longitudinal study of visual acuity loss in patients with X-linked retinoschisis.

Purpose: To determine the presence of fundus findings and natural course of visual acuity change in patients with juvenile X-linked retinoschisis (XLRS). Methods: A retrospective longitudinal study of 38 patients with juvenile XLRS (age range, 9–65 years) was conducted. Best-corrected visual acuity, Goldmann visual fields, and results of slit-lamp biomicroscopy of the anterior segment and dilated fundus examination were obtained for all patients. Visual acuity findings at the most recent and initial visits were compared. Follow-up ranged from 1 year to 28 years (mean, 10.2 years). Twenty-five patients were observed for >5 years, and 11, for ≥15 years. Results: Foveal lesions varied from predominantly radial striations (3%), microcystic lesions (34%), honeycomblike cysts (8%), or their combinations (31%) to non–cystic-appearing foveal changes, such as pigment mottling (8%), loss of the foveal reflex (8%), or an atrophic-appearing lesion (8%). Twelve patients (32%) had situs inversus of their retinal vessels. We observed a superior nasal restriction in the peripheral visual field even in the absence of clinically apparent peripheral retinoschisis. Of the 38 patients who were seen more than once, using logarithm of the minimum angle of resolution (logMAR) comparison, 4 had a decrease in visual acuity of >0.1 logMAR, equivalent to >1 line on an ETDRS chart, in their better seeing eye, and 3 had a reduction in visual acuity of >0.2 logMAR in their better eye. Conclusions: A limited change in visual acuity was observed in our cohort of 38 patients with XLRS even over an extended period. However, those patients with non–cystic-appearing changes within the fovea, including pigment mottling or an atrophic-appearing lesion, tended to have a more appreciable degree of visual acuity impairment compared with those patients with a cystic-appearing foveal change.

Cone phototransduction and growth of the ERG b-wave during light adaptation

The purpose of this study was to determine whether cone redepolarization accounts for the amplitude increase of the b-wave of the human electroretinogram (ERG) during light adaptation. The time course of the b-wave amplitude increase was compared to the time course of the change in the activation phase of cone phototransduction, as derived from a delayed Gaussian model applied to the leading edge of the ERG a-wave. ERG recordings were obtained from five visually normal subjects, alternately in the presence of the adapting field (adapt-on condition) and 300ms after its temporary extinction (adapt-off condition). The proportional increase in amplitude was less for R(mp3) (maximum amplitude of P3, the massed cone photoreceptor response) than for the b-wave for both adaptation conditions, and the time course of the amplitude increase for R(mp3) was faster than that for the b-wave in the adapt-off condition. The results demonstrate that time-dependent changes in the activation phase of cone phototransduction have only a minimal role in governing the increase in the amplitude of the human cone-derived ERG b-wave during light adaptation. In addition, the systematic increase in b-wave amplitude and the decrease in b-wave implicit time in the adapt-off condition indicates that the ERG response measured shortly after adapting field offset does not necessarily represent the waveform of the dark-adapted cone ERG.

Contrast sensitivity with presbyopic contact lenses

The purpose of the work was to assess the contrast sensitivity function of individuals wearing gas permeable (GP) multifocal contact lenses, soft bifocal contact lenses, and GP monovision lenses. Twenty-six females and six males between the ages of 42 and 65 participated in this study. The study included subjects wearing monovision (N = 8), the Acuvue Bifocal (Johnson & Johnson) (N = 8), Essential GP Multifocal (Blanchard) lenses (N = 8) and progressive addition spectacle lenses (PAL) (N = 8), with PAL wearers forming the control group. Measurements of binocular contrast sensitivity were obtained using the VISTECH 6500 system. Thresholds for each spatial frequency were fit to the equation CS(k) = ak exp(−bk) [1 + c exp(bk)]−1/2, to describe the human contrast sensitivity function. The area under the contrast sensitivity function (CSF) curve was calculated for all four groups and compared. An index of performance was obtained, which was defined as the ratio of CSF with the contact lens correction to the CSF with spectacles. Of the contact lens wearing groups, GP multifocal contact lens wearers had the highest contrast sensitivity at all the spatial frequencies. Soft bifocal contact lens wearers exhibited higher contrast sensitivity than monovision wearers at all spatial frequencies. Subjects wearing GP multifocals had the largest area under the CSF; followed by those wearing soft bifocals, with monovision wearers having the smallest area. GP multifocals have the best visual function at 0.98, soft bifocals have an index of 0.65 and monovision has an index of 0.59. This study quantifies the visual performance of the three lens systems by measuring the area under the CSF curve. In addition, it provides indices of visual function with the contact lenses that will be helpful for analyses and comparisons in future studies.

Activation phase of cone phototransduction and the flicker electroretinogram in retinitis pigmentosa.

This study examined the relationship between the activation phase of cone phototransduction and the flicker electroretinogram (ERG) in 15 patients with retinitis pigmentosa (RP) and 12 age-equivalent, visually normal control subjects. Values of Rmp3 (maximum amplitude of P3, the massed cone photoreceptor response) and S (sensitivity of cone phototransduction) were derived from a delayed Gaussian model applied to the leading edge of the ERG a-wave. Fundamental amplitude and phase of the flicker ERG were derived from responses to sinusoidal flicker presented at temporal frequencies ranging from 7.8 to 100 Hz. Patients with RP who had a reduced value of Rmp3 alone had an overall reduction in flicker ERG amplitude with a normal response phase across temporal frequency. Patients with RP who had a reduced value of S, whether or not Rmp3 was reduced, had the greatest amplitude reduction at temporal frequencies above 40 Hz and phase lags across a range of temporal frequencies. At high temporal frequencies, the amplitude reduction of the flicker ERG was predicted by the product of Rmp3 and S for all of the subjects except the three patients with RP who had the lowest fundamental amplitudes. The results indicate that there is a systematic relationship between the derived parameters of the activation phase of cone phototransduction and the characteristics of the flicker ERG in patients with RP, although the phase changes in the flicker ERG were generally greater than predicted by the derived parameters alone.

Higher-order wavefront aberrations in retinitis pigmentosa

Purpose. The purpose of this study was to characterize higher-order wavefront aberrations associated with posterior subcapsular (PSC) cataracts in patients with retinitis pigmentosa (RP). Methods. Wavefront aberrations were measured by Shack-Hartmann (SH) aberrometry in eight patients with RP who had PSC cataracts, 10 patients with RP who had minimal or no PSC cataracts, and 16 age-equivalent visually normal control subjects. Higher-order wavefront aberrations for 3-mm and 6-mm pupil diameters were defined as the root mean square (RMS) of the wavefront aberration functions. Results. For a 6-mm pupil diameter, the mean RMS for total higher-order wavefront aberrations was significantly larger for the patients with RP than for the control subjects, both for patients with PSC cataract (F = 17.30, p < 0.001) and for those with minimal or no PSC cataract (F = 4.80, p < 0.05). The mean RMS for third-order aberrations was not significantly different for patients with RP than for the control subjects. However, the mean RMS for fourth-order aberrations was significantly larger for the patients with RP than for the control subjects, both for patients with PSC cataract (F = 8.85, p < 0.01) and those with minimal or no PSC cataract (F = 5.07, p < 0.05). There were no significant differences in higher-order aberrations between the patients with RP and the control subjects for a 3-mm pupil diameter. Conclusions. Increased higher-order wavefront aberrations were present in patients with RP with and without clinically observable PSC cataracts. The measurement of wavefront aberrations in patients with RP provides an objective and quantitative method for detecting and monitoring disease-related changes in the optics of the eye.

A method for differentiating ocular higher- order aberrations from light scatter applied to retinitis pigmentosa

Purpose. The purpose of this study is to report a method for differentiating ocular higher-order aberrations and intraocular light scatter based on a deconvolution technique. Methods. An optical system was used to image a laser slit on the retina and also to perform Shack-Hartmann wavefront sensing. From the laser slit image, the line spread function, incorporating both ocular higher-order aberrations and light scatter, was derived. The laser slit image was deconvolved with a point spread function obtained from the Shack-Hartmann image. The area under the line spread function that was derived from the laser slit image after deconvolution provided a measurement of intraocular light scatter. The deconvolution technique was applied to images obtained in a group of 13 patients (mean age ± 1 standard deviation: 42 ± 12 years) with retinitis pigmentosa (RP), a retinal disease in which, by clinical examination, changes in the lens of the eye can be manifested. Measurements were compared with those obtained from 20 visually normal control subjects (mean age ± 1 standard deviation: 43 ± 17 years). Results. Combined higher-order aberrations and light scatter, measured as the area under the line spread function derived from the laser slit image, were increased significantly in the patients with RP as compared with the control subjects (p = 0.004). Ocular higher-order aberrations obtained from the Shack-Hartmann images were higher in the patients with RP than in the control subjects (p = 0.05). Intraocular light scatter derived from the deconvolved laser slit image was significantly higher in the patients with RP than in the control subjects (p = 0.009). Minimizing the contribution of ocular higher-order aberrations by deconvolution reduced the area under the line spread function in the control subjects and patients with RP, denoting an improvement in retinal image quality. Conclusions. A method for differentiating ocular higher-order aberrations and intraocular light scatter based on deconvolution was developed that may be useful for determining the level of improvement in retinal image quality that can be anticipated by the application of adaptive optics to aging and diseased human eyes.