Age differences in Vistech near contrast sensitivity

Dry eye in post-menopausal women using hormone replacement therapy

PURPOSE

To evaluate the effect of hormone replacement therapy (HRT) on dry eye in post-menopausal women.

METHODS

Forty post-menopausal women with dry eye (20 patients, group 1) and without dry eye (20 patients, group 2), and planning to receive HRT (estrogen plus progesterone), were recruited as the study groups. Forty age-matched untreated women were enrolled as controls (group 3 with dry eye, 5 patients; group 4 without dry eye, 35 patients). Patients having at least one of the symptoms (dryness, itching, photophobia, foreign body sensation, and tearing) together with two of the tests with positive results for dry eye (tear film break-up time (BUT), fluorescein staining of the cornea, analysis of the meibomian gland, and Schirmer I test) in both eyes were considered dry eye positive. Hormonal assay for follicle stimulating hormone, luteinizing hormone, estradiol, and free testosterone was performed. Dry eye statuses in the groups were evaluated statistically.

RESULTS

Four patients with incomplete follow-up data were excluded. HRT use increased estradiol levels in the groups. Mean ages of patients (50.2+/-4.8 and 50.7+/-3.9 years, and 50.0+/-4.6 and 53.0+/-3.9 years) were similar (p=0.67). Duration of menopause in groups 1 and 2 (3.2+/-2.2 and 1.4+/-1.2 years; p=0.01), and in groups 3 and 4 (3.0+/-1.6 and 1.7+/-1.3 years; p=0.014) were different. At the third month examinations, all of the patients in group 1, and 11 patients (61.1%) in group 2 had dry eye (p=0.003).

CONCLUSION

Duration of menopause and use of HRT may increase the incidence of dry eye in post-menopausal woman.

Age differences in search of web pages: the effects of link size, link number, and clutter

Reaction time, eye movements, and errors were measured during visual search of Web pages to determine age-related differences in performance as a function of link size, link number, link location, and clutter. Participants (15 young adults, M = 23 years; 14 older adults, M = 57 years) searched Web pages for target links that varied from trial to trial. During one half of the trials, links were enlarged from 10-point to 12-point font. Target location was distributed among the left, center, and bottom portions of the screen. Clutter was manipulated according to the percentage of used space, including graphics and text, and the number of potentially distracting nontarget links was varied. Increased link size improved performance, whereas increased clutter and links hampered search, especially for older adults. Results also showed that links located in the left region of the page were found most easily. Actual or potential applications of this research include Web site design to increase usability, particularly for older adults.

Visual function in menopause: the role of hormone replacement therapy

OBJECTIVE

To assess the effects of hormone replacement therapy (HRT) on visual function after menopause.

DESIGN

This study was conducted on 80 postmenopausal women aged 52 to 70 years. Women were randomly divided into two groups: 40 women were treated by oral HRT (equine conjugated estrogens 0.625 mg/day + dydrogesterone 5 mg/day in a continuous combined regimen), and 40 women were not treated with hormones (control group). Each woman underwent a contrast sensitivity test, a Schirmer test, and an evaluation of intraocular pressure before starting the study and 1 year after the beginning of the study. Statistical analysis was performed by Student's test and Fisher's exact test.

RESULTS

Contrast sensitivity function was significantly improved in all spatial frequencies (1.5, 3, 6, and 12 cycles per degree) with the exception of 18 cycles per degree in the HRT group 1 year after the beginning of treatment, whereas the control group demonstrated significant impairment at the lowest spatial frequencies (1.5, 3, and 6 cycles per degree). Tear production was significantly improved in the HRT group 1 year after the beginning of treatment, and intraocular pressure was similar in the two groups before and after the beginning of the study.

CONCLUSIONS

HRT improves visual function, promoting a better contrast sensitivity and a higher tear production, but does not modify intraocular pressure.

Structural modeling of contrast sensitivity in adulthood

Structural equation modeling was used to assess the utility of the sensorineural model of contrast sensitivity proposed by Sekuler et al. [Vision Res. 24, 689 (1984)] to account for spatial vision in adulthood. In Study 1, visual acuity and contrast sensitivity (1.5-18 c/deg) were measured in 84 people between the ages of 19 and 81 yr. No three-filter model fitted the data well. Although a two-filter model was associated with good fit indices, parameter estimates for both filters were inconsistent with physiological and behavioral data. In Study 2, acuity and contrast sensitivity (1.5-18 c/deg) were assessed in 95 observers between the ages of 23 and 73 yr. All measures were gathered once per month over a three-month period. The Sekuler et al. three-filter model did not fit the data from any time of measure, but a two-filter, bandpass model provided a consistent and excellent fit for all three waves. The model suggests that age-related change in the neural mechanisms underlying contrast sensitivity is minimal once acuity is controlled. Discrepancies between this conclusion and that reported by Sekuler et al. may be related to test type, psychophysical method, reliability, and sample selection.

Improving the effectiveness of the infant contrast sensitivity card procedure

Based on results from an earlier prototype, custom software and printing techniques were developed to construct a new card-based test of contrast sensitivity (CS) for nonverbal subjects. Compared with the prototype, the new CS card test contains three improvements: (1) larger, more salient test gratings; (2) higher contrast warm-up cards for each spatial frequency set; and (3) smaller contrast step size between adjacent cards. The success of the new cards was evaluated by testing 3.5- and 12-month-old human infants. Results indicated that the new version of the test required little time to complete (mean, 6.5 min) and provided accurate estimates of visual acuity. Also, group contrast sensitivity functions (CSFs) showed substantial development from 3.5 to 12 months of age. Surprisingly, however, group CSFs obtained with the new cards were lower than those obtained with the prototype, a discrepancy that may be due to differences in space average luminance between the two sets of cards. In all, the new CS card procedure possesses several merits that give it potential as an option for assessing spatial vision in infants, toddlers, and subjects with multiple impairments.

Aging effects on vernier hyperacuity: a function of oscillation rate but not target contrast

PURPOSE

Most previous studies have shown static vernier acuity for high-contrast targets to be largely unaffected by aging; those examining adult age differences on oscillatory displacement thresholds have consistently reported marked age deficits. The goals of this study were to (1) measure the age deficit on oscillatory discrimination beyond that attributable to any change in spatial discrimination by using the same target configuration for both task types and (2) determine whether an age-related change in the contrast response of the visual system contributes to age differences on static or oscillatory discrimination.

METHODS

The displacement thresholds of young and old observers for a vernier task configuration were determined at two target contrast levels (0.08 and 0.64) for static and oscillating targets (2 and 6 Hz)

RESULTS

No age differences were seen on static displacement thresholds at either high or low contrast. A marked age deficit that emerged when oscillation was increased was unrelated to target contrast or observer contrast sensitivity.

CONCLUSIONS

Age-related declines in oscillatory discrimination beyond those attributable to spatial discrimination do not appear to be attributable to optical factors nor to a decline in the contrast response of the senescent visual system. These findings are discussed in terms of a functional decline in the magnocellular pathway, or "neural entropy," possibly due to random cell loss.

Effects of ageing on spatial aspects of the pattern electroretinogram in male and female quail

This study deals with age-related functional changes in the eye of quail. Measurements of lens refractive state and transmission, as well as pupil diameter, showed that the quail's eye became more myopic with increasing age, but no change could be detected in lens transmission and pupil diameter. Three aspects of the pattern electroretinogram (PERG) were studied after correcting for ocular refraction: (i) spatial characteristics (visual acuity and contrast sensitivity); (ii) maximal amplitude; and (iii) peak latency. The PERG results suggested that the visual acuity was age-independent for both sexes. However, the contrast sensitivity of the old quail (16-20 months) was much lower (1.5-3 times) than that of the young (3-6 months) at low to intermediate (< 2 c/d), but not at high spatial frequencies. The peak latency of the PERG response was 3-4 msec longer in the old birds compared with the young, while the maximal amplitude of the PERG response was age-independent. These results clearly suggested that at least some of the age-induced changes are located in the neural retina.

Paired comparison of contrast sensitivity in diffractive multifocal IOLs and conventional monofocal IOLs

Multifocal intraocular lens (IOL) optics produce a retinal image of reduced contrast, which results from splitting incoming light between multiple focal points. This study sought to determine whether the reduced-contrast image results in functional loss of contrast sensitivity. Contrast sensitivity was measured in patients in the US Food and Drug Administration (FDA) study of the 3M Diffractive IOL, using the Pelli-Robson Letter Chart. Fifty-eight of these patients, including six from our clinic, were 'best-case' patients with no pathology, and also had paired multifocal/monofocal implants. Data from these 'best-care' patients with paired eyes indicate no functional difference in contrast sensitivity. Additional data obtained on our six patients with the Regan Low Contrast Charts suggest small predictable differences may exist for some patients at very low contrast levels. Further study is needed to determine whether these differences have functional significance.

Age differences in the temporal continuity of gratings as a function of their spatial frequency

This study compared young and elderly observers on the continuity of sinusoidal grating-pairs as a function of interstimulus interval (ISI) and spatial frequency (.5, 1.0, 2.0, 4.0, 8.0, and 12.0 c/deg). Consistent with prior research, the maximum ISI over which pattern continuity was maintained increased with spatial frequency. In addition, among older observers, grating continuity occurred at significantly longer ISI's at the two lowest spatial frequencies; no age difference was observed at the higher spatial frequencies. These results could not be attributed to an age difference in retinal illumination associated with pupillary miosis. However, they do indicate an age-related decline in detecting visual offset and are consistent with the hypothesis of a decline in the effectiveness of the transient visual channels.