Developmental changes in the balance of disparity, blur and looming/proximity cues to drive ocular alignment and focus

Accurate co-ordination of accommodation and convergence is necessary to view near objects and develop fine motor co-ordination. We used a remote haploscopic videorefraction paradigm to measure longitudinal changes in simultaneous ocular accommodation and vergence to targets at different depths, and to all combinations of blur, binocular disparity, and change-in-size (“proximity”) cues. Infants were followed longitudinally and compared to older children and young adults, with the prediction that sensitivity to different cues would change during development. Mean infant responses to the most naturalistic condition were similar to those of adults from 6-7 weeks (accommodation) and 8-9 weeks (vergence). Proximity cues influenced responses most in infants less than 14 weeks of age, but sensitivity declined thereafter. Between 12-28 weeks of age infants were equally responsive to all three cues, while in older children and adults manipulation of disparity resulted in the greatest changes in response. Despite rapid development of visual acuity (thus increasing availability of blur cues), responses to blur were stable throughout development. Our results suggest that during much of infancy, vergence and accommodation responses are not dependent on the development of specific depth cues, but make use of any cues available to drive appropriate changes in response.

A new calibrated sunspot group series since 1749: statistics of active day fractions

Although the sunspot-number series have existed since the mid-19th century, they are still the subject of intense debate, with the largest uncertainty being related to the "calibration" of the visual acuity of individual observers in the past. Daisy-chain regression methods are applied to inter-calibrate the observers which may lead to significant bias and error accumulation. Here we present a novel method to calibrate the visual acuity of the key observers to the reference data set of Royal Greenwich Observatory sunspot groups for the period 1900-1976, using the statistics of the active-day fraction. For each observer we independently evaluate their observational thresholds [S_S] defined such that the observer is assumed to miss all of the groups with an area smaller than S_S and report all the groups larger than S_S. Next, using a Monte-Carlo method we construct, from the reference data set, a correction matrix for each observer. The correction matrices are significantly non-linear and cannot be approximated by a linear regression or proportionality. We emphasize that corrections based on a linear proportionality between annually averaged data lead to serious biases and distortions of the data. The correction matrices are applied to the original sunspot group records for each day, and finally the composite corrected series is produced for the period since 1748. The corrected series displays secular minima around 1800 (Dalton minimum) and 1900 (Gleissberg minimum), as well as the Modern grand maximum of activity in the second half of the 20th century. The uniqueness of the grand maximum is confirmed for the last 250 years. It is shown that the adoption of a linear relationship between the data of Wolf and Wolfer results in grossly inflated group numbers in the 18th and 19th centuries in some reconstructions.

Corneal graft survival after therapeutic keratoplasty for Acanthamoeba keratitis

Purpose: To describe corneal graft survival and visual outcome after therapeutic penetrating keratoplasty in patients with Acanthamoeba keratitis (AK) that is unresponsive to clinical treatment. Methods: Retrospective study. Thirty-two patients with AK who underwent therapeutic penetrating keratoplasty (tPK) from August 1996 to August 2005 were included. Data relating to clinical features, visual acuity, surgical technique, graft survival and complications were collected. Graft survival was evaluated by the Kaplan-Meier method and comparisons were performed using the Log-rank test. Results: Most patients (62.5%) were female. Mean age [+/- standard deviation (SD)] was 35 (+/- 13) years (range 15-68 years). All patients were contact lens wearers. Eighteen patients (56%) presented paralytic mydriasis and glaucoma during the treatment. Thirteen patients (40%) developed glaucoma after surgery; eight of them (61%) required a second PK because of graft failure. Of the 32 keratoplasty eyes, 56.2% presented graft failure at any follow-up point. Forty-five per cent of graft failures occurred before the 12 month follow-up, so 55% remained clear in the first year after surgery. Twelve patients underwent a second PK; seven of them failed and 45% were clear at 1 year. Two patients presented graft recurrence of amoebic infection. There was no significant difference in graft survival when eyes with or without mydriasis were compared (P = 0.40). Eyes with glaucoma presented a significantly shorter graft survival (P = 0.01). Conclusion: Penetrating keratoplasty is a treatment option for eyes that are unresponsive to clinical treatment infections. However, graft survival is poor; postoperative glaucoma is frequent and is associated with shorter graft survival.

Geelong Osteoporosis Study Health Database

The database contains the following clinical, questionnaire and socio-demographic data suitable for cross-sectional and longitudinal analyses:
-Body composition: dual-energy x-ray absorptiometry (DXA) measures of the lumbar spine (posterior-anterior projection), proximal femur, whole body and forearm (ultradistal forearm and distal 33%)
-Other clinical assessments: body weight, height, arm span, waist and hip circumferences, blood pressure, visual acuity, muscle strength, functional reach test and timed ‘up-&-go’ test.
-Mental health: Major axis psychiatric disorders diagnosed using a Structured Clinical Interview.
-Blood and urine collections: blood and urine collected after an overnight fast.
-Questionnaires: exposure to disease, use of medications and supplements, diet, mobility, physical activity, sleep, sun exposure, falls and fractures, alcohol and tobacco use, reproductive history, family history of fractures and disease, quality of life, pain, anxiety and depression.
-Socio-demographics: Country of birth, ethnicity, marital status, education, housing and employment status, occupation, socioeconomic Index for Areas (SEIFA) scores.

Clinical performance of an innovative back surface multifocal contact lens in correcting presbyopia

Purpose: This prospective study was designed to subjectively and objectively evaluate the performance of an aspheric multifocal back surface rigid gas permeable (RGP) contact lens. The multifocal element of this lens design consisted of an aspheric optical zone that varied according to the patient's ametropia, corneal topography, and required reading addition.

Methods: We fit 28 presbyopic subjects with an aspheric multifocal back surface RGP contact lens (age range: 45 to 68 years). Reading additions ranged from +0.75 D to +2.50 D. Subjects were assessed initially and at 2, 6, and 12 weeks for ocular changes, visual performance, and subjective responses.

Results: We required 116 RGP lenses to achieve an acceptable fit and visual acuity in 28 subjects (55 eyes). At the final visit, the distance logMAR acuity with the multifocal contact lens (+0.12 +/-0.10) was not statistically different (t=-0.623, P= 0.5388) from spectacle acuity at the initial visit (+0.10 +/-0.12). The near logMAR acuity with the multifocal contact lens at the final visit (0.36 +/- 0.12) was not statistically different from that for near acuity with spectacles at the initial visit (0.33 +/- 0.13). No slit lamp signs worsened during the study. A reduction in myopia of 0.67 D was noted by the final visit. Spectacle blur was noted if the acuity at the initial refraction was compared to the acuity with the same refraction at the final visit (t= -3.287, P= 0.0028) but not when the refractive changes were incorporated (t= 1.058, P= 0.3127). All subjects rated the performance of the lenses very highly: comfort, 86%; distance acuity, 83%; near acuity, 73%; and stability of vision, 74%. Twenty-four subjects (86%) chose the multifocal contact lens as their preference.

Conclusion: We demonstrated that a multifocal design is able to provide acceptable distance and near correction for presbyopic patients. The aspheric geometry required can be optimized for a given patient by considering his/her degree of ametropia, as well as the corneal topography.

An investigation of the efficacy of a novel ocular lubricant

Objective: To investigate the efficacy of a novel ocular lubricant compared with a commercially marketed ocular lubricant in a group of noncontact lens wearers currently using over-the-counter products for the management of symptoms of moderate to severe dry eye.

Methods: This was a prospective, double-masked study that randomized 110 subjects in a ratio of 1:1 to receive a novel ocular lubricant (test group) or a marketed ocular lubricant (control group). Subjects were instructed to instill the lubricant eye drops at least three times daily. After enrollment, subjects were evaluated at baseline and at 7 and 30 days. They were also required to complete a series of home-based subjective questionnaires after 15 days. Main outcomes were subjective symptoms and objective clinical assessment at 7 and 30 days.

Results: The test group had higher overall comfort ratings than the control group (P = 0.012). Seventy-one percent of the test group and 57% of the control group said the drops used “somewhat” or “definitely” improved ocular comfort; 62% of the test group had greater end-of-day comfort compared with 45% of the control group (P = 0.015). There were no between-group differences in visual acuity, tear quality or quantity, corneal staining, conjunctival staining, or bulbar and limbal conjunctival hyperemia.

Conclusions: The novel ocular lubricant offers equivalent or superior comfort compared with a marketed lubricant eye drop. Objective clinical outcomes were not statistically significantly different between the two groups.

Glaucoma and on-road driving performance

PURPOSE. To investigate the on-road driving performance of patients with glaucoma.

METHODS. The sample comprised 20 patients with glaucoma and 20 subjects with normal vision, all licensed drivers, matched for age and sex. Driving performance was tested over a 10-km route incorporating 55 standardized maneuvers and skills through residential and business districts of Halifax, Nova Scotia, Canada. Testing was conducted by a professional driving instructor and assessed by an occupational therapist certified in driver rehabilitation, masked to participant group membership and level of vision. Main outcome measures were total number of satisfactory maneuvers and skills, overall rating, and incidence of at-fault critical interventions (application of the dual brake and/or steering override by the driving instructor to prevent a potentially unsafe maneuver). Measures of visual function included visual acuity, contrast sensitivity, and visual fields (Humphrey Field Analyzer; Carl Zeiss Meditec, Inc., Dublin, CA; mean deviation [MD] and binocular Esterman points).

RESULTS. There was no significant difference between patients with glaucoma (mean MD = −1.7 dB [SD 2.2] and −6.5 dB [SD 4.9], better and worse eyes, respectively) and control subjects in total satisfactory maneuvers and skills (P = 0.65), or overall rating (P = 0.60). However, 12 (60%) patients with glaucoma had one or more at-fault critical interventions, compared with 4 (20%) control subjects (odds ratio = 6.00, 95% CI, 1.46–24.69; higher still after adjustment for age, sex, medications and driving exposure), the predominant reason being failure to see and yield to a pedestrian. In the glaucoma group, worse-eye MD was associated with the overall rating of driving (r = 0.66, P = 0.002).

CONCLUSIONS. This sample of patients with glaucoma with slight to moderate visual field impairment performed many real-world driving maneuvers safely. However, they were six times as likely as subjects with normal vision to have a driving instructor intervene for reasons suggesting difficulty with detection of peripheral obstacles and hazards and reaction to unexpected events.

Risk of falls and motor vehicle collisions in glaucoma

PURPOSE. To investigate the risk of falls and motor vehicle collisions (MVCs) in patients with glaucoma.

METHODS. The sample comprised 48 patients with glaucoma (mean visual field mean deviation [MD] in the better eye = −3.9 dB; 5.1 dB SD) and 47 age-matched normal control subjects, who were recruited from a university-based hospital eye care clinic and are enrolled in an ongoing prospective study of risk factors for falls, risk factors for MVCs, and on-road driving performance in glaucoma. Main outcome measures at baseline were previous self-reported falls and MVCs, and police-reported MVCs. Demographic and medical data were obtained. In addition, functional independence in daily living, physical activity level and balance were assessed. Clinical vision measures included visual acuity, contrast sensitivity, standard automated perimetry, useful field of view (UFOV), and stereopsis. Analyses of falls and MVCs were adjusted to account for the possible confounding effects of demographic characteristics, medications, and visual field impairment. MVC analyses were also adjusted for kilometers driven per week.

RESULTS. There were no significant differences between patients with glaucoma and control subjects with respect to number of systemic medical conditions, body mass index, functional independence, and physical activity level (P > 0.10). At baseline, 40 (83%) patients with glaucoma and 44 (94%) control subjects were driving. Compared with control subjects, patients with glaucoma were over three times more likely to have fallen in the previous year (odds ratio [OR]adjusted = 3.71; 95% CI, 1.14–12.05), over six times more likely to have been involved in one or more MVCs in the previous 5 years (ORadjusted = 6.62; 95% CI, 1.40–31.23), and more likely to have been at fault (ORadjusted = 12.44; 95% CI, 1.08–143.99). The strongest risk factor for MVCs in patients with glaucoma was impaired UFOV selective attention (ORadjusted = 10.29; 95% CI, 1.10–96.62; for selective attention >350 ms compared with ≤350 ms).

CONCLUSIONS. There is an increased risk of falls and MVCs in patients with glaucoma.

Relationship between vision impairment and ability to perform activities of daily living

Purpose: To determine the relationship between clinical measures of vision impairment and the ability to perform activities of daily living (ADLs).

Methods: One hundred and twenty subjects with low vision from a variety of causes participated in the study. Vision impairment was assessed under binocular conditions by measuring distance visual acuity, near word acuity, Melbourne Edge Test contrast sensitivity, Pelli–Robson Chart contrast sensitivity and visual fields. The ADL performance was assessed using the Melbourne Low Vision ADL Index (MLVAI), which is in part an observed performance assessment of instrumental ADLs and in part a self-report assessment of basic self-care ADLs.

Results: All vision measures had a high, statistically significant correlation with MLVAI total score. Near word acuity, had the strongest correlation (rs=−0.86, p < 0.001), followed by Melbourne Edge Test contrast sensitivity (rs=0.80, p < 0.001). Visual field had the weakest correlation (rs=0.56, p < 0.001). Together, age, near word acuity, Melbourne Edge Test contrast sensitivity and visual field accounted for 82.2% (adjusted R2, p < 0.001) of the variance in MLVAI total score. All correlations obtained were higher for the observed performance assessment of instrumental ADLs than for the self-report assessment of basic self-care ADLs.

Conclusions: Clinical vision impairment measures are highly correlated with capacity to perform ADLs, as measured by the MLVAI.

Investigation of the performance of the menifocal Z gas-permeable bifocal contact lens during continuous wear

Purpose. The Menifocal Z is an alternating vision, concentric, bifocal gas-permeable (GP) contact lens; center distance is connected to near periphery by a smooth transition zone. The lens is produced using tisilfocon A (Menicon Z material), which is approved for up to 30 days of continuous wear (CW). The aim of this study was to evaluate the clinical performance of the Menifocal Z when worn for up to 30 days of CW for 6 months.

Methods. Thirty-five existing GP lens wearers were enrolled in the study. Subjects were fitted with Menifocal Z lenses and follow-up visits were conducted after 2 weeks of daily wear and 1 day, 1 week, 6 weeks, 3 and 6 months of CW. A range of objective and subjective clinical performance measures were assessed, including distance and near visual acuity, the physiological response to CW, and subjective evaluation of vision and comfort.

Results. Twenty-seven subjects (77%) completed the study and eight (23%) discontinued: five (14%) as a result of lens-related problems (four vision, one comfort) and three (9%) as a result of non-lens related reasons. Average CW time achieved by the subjects was 22 ± 2 days. Mean binocular logarithm of the minimum angle of resolution (logMAR) acuities at 6 months were: high contrast distance 0.03 (20/20-), low contrast distance 0.63 (20/80-), and high contrast near 0.26 (20/25, N4). Adverse responses and lens binding were minimal, and there were no significant increases in corneal staining, corneal vascularization, or superior palpebral conjunctival papillae over time (p > 0.05). Problems with night vision (distance and near) with the lenses were the most common difficulties reported by the subjects.

Conclusions. The Menifocal Z appears to be a promising option for presbyopic vision correction, providing successful correction of distance and near vision in a group of experienced GP lens wearers. The hyper Dk tisilfocon A (Menicon Z) material allowed for safe wear of the lenses on a CW basis.

Comparison of functional mobility performance with clinical vision measures in simulated Retinitis Pigmentosa

Simulations of retinitis pigmentosa (RP) under various conditions of retinal illuminance were designed and investigated in order that they might be used in the mobility training of clients with early RP. Goggles incorporating a 2.5 neutral density (ND) filter with a 0.5-mm diameter pinhole were found to be a potentially useful simulation device for this purpose. This investigation also compared mobility performance with clinical vision measures under photopic, mesopic, and scotopic conditions of retinal illuminance. Although none of the clinical vision measures we used was entirely predictive of mobility performance, some measures were better predictors than others. For a severe constriction of the visual field and decreasing retinal illuminance, both edge contrast sensitivity and visual acuity, measured outdoors, accounted for a greater proportion of the variance in mobility performance than did low contrast visual acuity measured under the same circumstances. The same clinical vision measures, taken in-doors, were of no value in predicting outdoor mobility performance.

Relationship between Clinical Macular Changes and Retinal Function in Age-Related Macular Degeneration

Purpose

Refractive errors in students from Middle Eastern backgrounds living and undertaking schooling in Australia

Background:  Environmental factors associated with schooling systems in various countries have been implicated in the rising prevalence of myopia, making the comparison of prevalence of refractive errors in migrant populations of interest. This study aims to determine the prevalence of refractive errors in children of Middle Eastern descent, raised and living in urban Australia but actively maintaining strong ties to their ethnic culture, and to compare them with those in the Middle East where myopia prevalence is generally low.Methods:  A total of 354 out of a possible 384 late primary/early secondary schoolchildren attending a private school attracting children of Middle Eastern background in Melbourne were assessed for refractive error and visual acuity. A Shin Nippon open-field NVision-K5001 autorefractor was used to carry out non-cycloplegic autorefraction while viewing a distant target. For statistical analyses students were divided into three age groups: 10–11 years (n = 93); 12–13 years (n = 158); and 14–15 years (n = 102).Results:  All children were bilingual and classified as of Middle Eastern (96.3 per cent) or Egyptian (3.7 per cent) origin. Ages ranged from 10 to 15 years, with a mean of 13.17 ± 0.8 (SEM) years. Mean spherical equivalent refraction (SER) for the right eye was +0.09 ± 0.07 D (SEM) with a range from -7.77 D to +5.85 D. The prevalence of myopia, defined as a spherical equivalent refraction 0.50 D or more of myopia, was 14.7 per cent. The prevalence of hyperopia, defined as a spherical equivalent refraction of +0.75 D or greater, was 16.4 per cent, while hyperopia of +1.50 D or greater was 5.4 per cent. A significant difference in SER was seen as a function of age; however, no significant gender difference was seen.Conclusions:  This is the first study to report the prevalence of refractive errors for second-generation Australian schoolchildren coming from a predominantly Lebanese Middle Eastern Arabic background, who endeavour to maintain their ethnic ties. The relatively low prevalence of myopia is similar to that found for other metropolitan Australian school children but higher than that reported in the Middle East. These results suggest that lifestyle and educational practices may be a significant influence in the progression of myopic refractive errors.