Neryla Jolly

Prevalence and causes of amblyopia in an adult population

OBJECTIVE The study aimed to determine the prevalence, causes, and associations with amblyopia in a defined older population. DESIGN In a population-based study, 3654 persons 49 years of age or older from an area west of Sydney, Australia, underwent a detailed eye examination and history, including objective and subjective refraction, cover testing, and retinal and lens photography. Amblyopia was diagnosed in eyes with reduced best-corrected visual acuity in the absence of any other cause. RESULTS Amblyopia was diagnosed in 118 participants, or 3.2% of the population using a visual acuity criterion of 20/30 or less and 2.9% using a visual acuity criterion of 20/40 or less. Using a two-line visual acuity difference between the eyes, the amblyopia prevalence was 2.6% and 2.5%, respectively, for the above criteria. The underlying amblyogenic causes assessed were anisometropia (50%), strabismus (19%), mixed strabismus and anisometropia (27%), and visual deprivation (4%). The visual acuity of the amblyopic eye was 20/200 or worse (19%), 20/80 to 20/160 (19%), 20/40 to 20/63 (52%), and 20/30 (11%). No statistically significant associations were found between amblyopia and gender or eye affected. The most frequent pattern of strabismus was esotropia, whereas hypermetropia was the most frequent refractive error in amblyopic eyes. The mean age at diagnosis was earlier for strabismic and mixed amblyopia (7.4 years) than for anisometropic amblyopia (12.7 years). CONCLUSION This study has provided prevalence and cases of amblyopia in an older population. Amblyopia is a frequent cause of lifelong unilateral visual impairment.

Validity and reliability of the on-road driving assessment with senior drivers.

The on-road driving assessment is widely regarded as the criterion measure for driving performance despite a paucity of evidence concerning its psychometric properties. The purpose of this study was 2-fold. First, we examined the psychometric properties of an on-road driving assessment with 100 senior drivers between 60 and 86 years (80 healthy volunteers and 20 with specific vision deficits) using Rasch modeling. Second, we compared the outcome of the gestalt decision made by trained professionals with that based on weighted error scores from the standardized assessment. Rasch analysis provided good evidence for construct validity and inter-rater reliability of the on-road assessment and some evidence for internal reliability. Goodness of fit statistics for all items were within an acceptable range and the item hierarchy was logical. The test had a moderate reliability index (0.67). The best cut off score yielded sensitivity of 81% and specificity of 95% compared with the gestalt decision. Further research is required with less competent drivers to more fully examine reliability. Healthy senior drivers failed to check blind spots when changing lanes and made errors when asked to report road markings and traffic signs as they drove. In addition unsafe drivers had difficulty negotiating intersections and lane changes.

Visual loss during interocular suppression in normal and strabismic subjects

Visual acuity was measured in one eye during monocular vision, and while the fellow eye viewed stimuli not including the acuity target. The aim was to find how acuity in one eye is reduced by going from monocular to binocular viewing. In normal subjects, acuity was at its lowest during the suppressive phase of binocular rivalry, was reduced less when the fellow eye viewed a contoured nonrivalrous stimulus, and was not reduced at all when the stimulus to the fellow eye consisted of a uniformly lit field. In strabismic subjects, by contrast, acuity was markedly reduced in going from monocular to binocular viewing no matter what stimulus was viewed by the fellow eye. Pathological suppression is therefore largely independent of the inducing stimulus. It was also shown that acuity in the nonstrabismic eye of some of the strabismic subjects was improved by allowing the strabismic eye to view; these were the subjects with the greatest depths of amblyopia.

Current licensing authority standards for peripheral visual field and safe on-road senior aged automobile driving performance

Background:  The current licensing authoritys (Austroads) visual field standards are met when a person demonstrates an intact visual field extending horizontally at least 120 degrees within 10 degrees above and below the horizontal midline. A person cannot be licensed unconditionally if they have a hemianopia, quadrantanopia or any significant visual field loss (scotoma) that is likely to impede driving performance. Despite fairly rigorous implementation of these vision standards by licensing authorities, there is little scientific evidence available to demonstrate that a driver will or will not be safe on road depending on the extent of their visual field.

Components of visual acuity loss in strabismus

Strabismus, the misalignment of the visual axis of one eye relative to that of the other eye, reduces visual acuity in the affected eye. Several processes contributing to that loss are: amblyopia, which results in a chronic acuity loss whether or not the fellow eye is viewing; strabismic deviation, which shifts the image of an acuity target onto more peripheral, and therefore less acute, retina when the fellow eye fixates; interocular suppression and binocular masking, which reduce visibility in the strabismic eye due to neural influences from the other eye. We measured the losses due to these processes in nine small-angle strabismic subjects. Amblyopia reduced acuity by a median of 34% relative to its value in subjects with normal binocular vision, and strabismic deviation produced a loss of 44%. Suppression and masking together reduced acuity by 20%, and therefore had substantially less effect than the other factors.

On-road assessment of driving performance in bilateral vestibular-deficient patients.

This study measured on‐road driving behavior in subjects with bilateral vestibular loss (BVL). Data included point‐of‐regard (what the driver is looking at and attending to), gaze stability (the performance of the vestibulo‐ocular reflex), and head movement, during complex maneuvers such as changing lanes, cornering, pulling into traffic, and parking. Subjective and objective measures showed few differences between BVL subjects and age‐matched controls, and that it is possible to drive well with little or no peripheral vestibular function. This has important implications for driver licensing, road‐safety policy, and for the potential successful rehabilitation of vestibular patients. Patients with unilateral vestibular dysfunction may have more difficulty driving than their bilateral counterparts.

Towards Gaining the Best Information About Vision to Assist the Recovery of a Patient with Stroke

Abstract Aim: The aim of this paper is to report on the development and evaluation of a tool, to be used by any healthcare practitioner, to screen for the presence of eye issues and problems in patients who have been diagnosed to have had a stroke. Practitioners caring for patients with stroke often detect stroke-related vision defects but miss pre-existing eye diseases, the need for glasses, and reduced acuity. In stroke units where orthoptists are employed the detection of eye conditions is high (83%) . The availability of orthoptists to work in stroke units is limited, so affected patients are likely to have undetected vision-based problems that may decrease the responsiveness to rehabilitation or prevent adaptations being made that can assist the patient with tasks. Research design: A retrospective study using patient data collected from 100 patient case histories. Methodology: The tool is a single page, tick-box checklist. It has 3 sections, each with actions to be implemented as required. The sections are: a. questions about ocular history and symptoms b. observation of ocular conditions (red eye, ptosis) c. tests requiring responses that could be affected by vision defects (ability to fix and follow) The tool was tested against 100 case histories of patients admitted to hospital following a stroke, comparing the ocular information noted by nonorthoptic healthcare practitioners and information from the orthoptic assessment. Results: Of the 498 ocular conditions found by the orthoptic assessment, the tool identified 309 (62%). Nonorthoptic healthcare practitioners identified 85 (17%) ocular conditions. Conclusion: In the absence of orthoptic services, the tool has the capacity to enable improved detection of vision conditions resulting in improved management as well as enhancing the response for rehabilitation. The study has at all times followed the principles as outlined in the Declaration of Helsinki.

Assessment of diplopia using saccades and pursuits and its relation to driving performance

of the development of an electrochemical cell reaction between the IOFB and the retina, leading either to direct reduction of the retinal components by electrons, or saponification of the retinal cell membranes in the nerve fibre layer. The acceleration of the chemical reaction during vitrectomy occurs as a result of bimetallic electrochemistry, with ion generation within the eye following gel removal and replacement with an electrolytic irrigating fluid. Rosseinsky et al. have since identified that changing the irrigating fluid does not alter the vigour of the electrochemical reaction. A ‘tunnel’ vitrectomy’ approach was therefore developed to try and reduce peroperative iatrogenic retinal damage with our two new cases, by limiting the movement of the IOFB within the eye until it could be removed as early as possible during the course of the operation. This strategy was associated with good visual outcomes and may be particularly suited to small IOFBs in younger patients with formed vitreous. An alternative strategy might be to use a rare Earth magnet to stabilize the IOFB before removal, but this was not available to us. Consideration could also be given to the use of Triamcinolone to help delineate the tunnel, but we were hesitant to introduce a steroid into a potentially infected vitreous cavity. In summary, galvanized steel foreign bodies behave differently to simple steel IOFBs. Surgeons should be aware that intraocular galvanized steel is electrochemically active and toxic, with the potential to cause permanent visual loss, and this risk increases during the operation to remove the IOFB. Management involves early surgery, in contrast to a recent trend towards delayed removal of intraocular foreign bodies. All attempts should be made to prevent accidental iatrogenic retinal injury by reducing the risk of the IOFB migrating to the macula area before or during the operation. Finally, both our cases were fortunate in that their IOFBs were eccentric to the macula; they also highlight the need for preventative education, as neither patient was wearing eye protection of any sort.