Miriam L. Conway

Field-specific visual-evoked potentials Identifying field defects in vigabatrin-treated children

Objective To derive a visual-evoked potential (VEP) technique for identifying visual field defects in children with epilepsy treated with vigabatrin and unable to perform perimetry. Background Studies have linked vigabatrin to a specific pattern of visual field loss. Few studies have included the pediatric population because of difficulties in assessing the visual field by perimetry below a developmental age of 9 years. Methods A field-specific VEP was developed with a central (0° to 5° radius) and peripheral stimulus (30° to 60° radius). Stimuli consisted of black and white checks that increased in size with eccentricity. Checks reversed at different rates, allowing separate central and peripheral responses to be recorded. Five vigabatrin-treated young adults with field defects were identified using this stimulus. Electroretinograms (ERG) were recorded to examine the effects of vigabatrin on retinal function. Thirty-nine children aged 3 to 15 years were included in the study. Twelve patients were examined by both the field-specific stimulus test and perimetry. The diagnostic performance of the field-specific stimulus test was compared with that of perimetry. Results Thirty-five of 39 children complied with the field-specific stimulus, 26 of 39 complied with the ERG, and 12 of 39 complied with perimetry. Using the summed amplitude of the peripheral response from O2 and O1, responses below 10 &mgr;V were deemed abnormal. The field-specific stimulus identified 3 of 4 abnormal perimetry results and 7 of 8 normal perimetry results, giving a sensitivity of 75% and a specificity of 87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude, with a cutoff below 70 &mgr;V, gave a useful indication of visual field loss. Conclusion Field-specific VEP are well tolerated by children older than 2 years of age and are sensitive and specific in identifying vigabatrin-associated peripheral field defects.

Visual Field Severity Indices Demonstrate Dose-Dependent Visual Loss from Vigabatrin Therapy

Purpose: The aims of this study were to develop an algorithm to accurately quantify Vigabatrin (VGB)‐induced central visual field loss and to investigate the relationship between visual field loss and maximum daily dose, cumulative dose and duration of dose.

Ocular blood-flow hemodynamics before and after application of a laser in situ keratomileusis ring

PURPOSE: To evaluate blood‐flow responses before and after microkeratome application. SETTING: School of Life and Health Sciences, Aston University, Birmingham, United Kingdom. METHODS: Hemodynamic responses were measured in eyes of healthy volunteers before and after transient elevation in intraocular pressure (IOP) resulting from microkeratome application. The IOP was elevated above 85 mm Hg for 90 seconds. Blood‐flow responses were measured using color Doppler imaging, Heidelberg retinal flowmetry, and an ocular blood‐flow analyzer. RESULTS: The study included 10 eyes. There was no difference in ocular‐perfusion measurements before or after IOP elevation using any measurement system. CONCLUSION: In normal healthy eyes, once suction was released, blood‐flow responses returned immediately to normal levels. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Investigation of Ocular Hemodynamics in Sturge-Weber Syndrome

Purpose. Sturge-Weber syndrome (SWS) is a condition often associated with facial cutaneous angioma, vascular malformations in the brain, and ocular anomalies such as glaucoma. Reduced cerebral blood flow and ischemia have been well documented. Less is known about ocular blood flow despite the frequent associations between altered hemodynamics and the mechanisms underlying glaucomatous optic neuropathy. The aim of this research was to investigate retrobulbar hemodynamics in patients diagnosed with SWS. Methods. The sample comprised 16 patients diagnosed with SWS and 16 age- and gender-matched normal control subjects. Four patients were diagnosed with both SWS and primary open-angle glaucoma (mean age 34.3 years; SD 26.9 years), three patients with both SWS and closed-angle glaucoma (mean age 23.3 years; SD 18.0 years), and nine patients with SWS and no glaucoma (mean age 17.2 years; SD 9.1 years). Systemic blood pressure and intraocular pressure were measured to determine the mean arterial pressure and ocular perfusion pressure. All patients and subjects underwent ultrasonography of the ophthalmic artery, central retinal artery, and short posterior ciliary arteries. Results. No significant difference between groups for mean arterial pressure or ocular perfusion pressure (p > 0.05) was recorded. Participants diagnosed with SWS and primary open-angle glaucoma showed significantly reduced end-diastolic velocity (mean 0.036 m/s; SD 0.005 m/s) in their central retinal artery (p = 0.016) when compared against their age-matched normal controls (mean 0.054 m/s; SD 0.010 m/s). Participants diagnosed with SWS and no glaucoma also showed significantly reduced end-diastolic velocity (mean 0.038 m/s; SD 0.015 m/s) in their central retinal artery (p = 0.046) when compared against their age-matched normal controls (mean 0.054 m/s; SD 0.014 m/s). Conclusions. Retrobulbar hemodynamics appear to be altered in participants diagnosed with SWS irrespective of their diagnosis of glaucoma. Further research is needed to ascertain whether there are any long-term consequences of such changes to ocular physiology.

Are rehabilitation services for patients in UK eye clinics adequate? A survey of eye care professionals

PurposeThe purpose of this study is to determine whether specific services such as emotional and family support are currently available in the United Kingdom for people with visual impairment.MethodsA validated online survey was created and distributed to clinical staff in eye clinics (for example, ophthalmologists and optometrists) and rehabilitation staff (for example, social and rehabilitation workers) in the community, who worked with people with visual impairment. A total of 67 clinical and 42 rehabilitation staff completed the entire survey online.ResultsOnly 67% of the respondents claimed their clinics provide emotional support and 44% of respondent’s clinics provided family support. Clinical and rehabilitation staff have differences in opinion over what constitutes an essential service for a visually impaired patient. Rehabilitation staff considered emotional support and referral to social services as essential more often than clinical staff (P<0.05). There is some confusion over the type of personnel who provides each type of service, with some services showing substantial repetition.ConclusionIn the clinics sampled, there appears to be an underprovision of emotional support (attentive listening plus constructive suggestions) and family support (emotional support and advice for family members) for visually impaired patients in the United Kingdom. There also seems to be some discrepancy in services that eye care professionals feel are available and previous reports by visually impaired patients of the service they receive. There is a need to develop standardised pathways across the United Kingdom, to solve some of these issues.

Coloured overlays and precision-tinted lenses: poor repeatability in a sample of adults diagnosed with visual stress

Visual stress consists of perceived distortions or discomfort while reading. It is claimed that these symptoms are alleviated by viewing through coloured lenses or overlays, with a specific colour required for each individual. This has been explained on the basis of altered visual cortex excitation as affected by the spectral content of the viewing light. If symptoms are indeed alleviated by a particular colour that has an impact on the individuals visual system, we would expect that selection of the most beneficial colour would be repeatable. The aim of this study was to determine whether this is the case.

Is the Aligning Prism Measured with the Mallett Unit Correlated with Fusional Vergence Reserves

Background The Mallett Unit is a clinical test designed to detect the fixation disparity that is most likely to occur in the presence of a decompensated heterophoria. It measures the associated phoria, which is the “aligning prism” needed to nullify the subjective disparity. The technique has gained widespread acceptance within professions such as optometry, for investigating suspected cases of decompensating heterophoria; it is, however, rarely used by orthoptists and ophthalmologists. The aim of this study was to investigate whether fusional vergence reserves, measured routinely by both orthoptists and ophthalmologists to detect heterophoria decompensation, were correlated with aligning prism (associated phoria) in a normal clinical population. Methodology/Principal Findings Aligning prism (using the Mallett Unit) and fusional vergence reserves (using a prism bar) were measured in 500 participants (mean 41.63 years; standard deviation 11.86 years) at 40 cm and 6 m. At 40 cm a strong correlation (p<0.001) between base in aligning prism (Exo FD) and positive fusional reserves was found. Of the participants with zero aligning prism 30% had reduced fusional reserves. At 6 m a weak correlation between base out aligning prism (Eso FD) and negative fusional reserves was found to break (p = 0.01) and to recovery (p = 0.048). Of the participants with zero aligning prism 12% reported reduced fusional reserves. Conclusions/Significance For near vision testing, the strong inverse correlation between base in aligning prism (Exo FD) and fusional vergence reserves supports the notion that both measures are indicators of decompensation of heterophoria. For distance vision testing and for those patients reporting zero aligning prism further research is required to determine why the relationship appears to be weak/non-existent?

Does Gender Influence Colour Choice in the Treatment of Visual Stress

Purpose Visual Stress (VS) is a condition in which words appear blurred, in motion, or otherwise distorted when reading. Some people diagnosed with VS find that viewing black text on white paper through coloured overlays or precision tinted lenses (PTLs) reduces symptoms attributed to VS. The aim of the present study is to determine whether the choice of colour of overlays or PTLs is influenced by a patient’s gender. Methods Records of all patients attending a VS assessment in two optometry practices between 2009 and 2014 were reviewed retrospectively. Patients who reported a significant and consistent reduction in symptoms with either overlay and or PTL were included in the analysis. Overlays and PTLs were categorized as stereotypical male, female or neutral colours based on gender preferences as described in the literature. Chi-square analysis was carried out to determine whether gender (across all ages or within age groups) was associated with overlay or PTL colour choice. Results 279 patients (133 males and 146 females, mean age 17 years) consistently showed a reduction in symptoms with an overlay and were included. Chi-square analysis revealed no significant association between the colour of overlay chosen and male or female gender (Chi-square 0.788, p = 0.674). 244 patients (120 males and 124 females, mean age 24.5 years) consistently showed a reduction in symptoms with PTLs and were included. Chi-square analysis revealed a significant association between stereotypical male/female/neutral colours of PTLs chosen and male/female gender (Chi-square 6.46, p = 0.040). More males preferred stereotypical male colour PTLs including blue and green while more females preferred stereotypical female colour PTLs including pink and purple. Conclusions For some VS patients, the choice of PTL colour is influenced not only by the alleviation of symptoms but also by other non-visual factors such as gender.

Efficacy of coloured overlays and lenses for treating reading difficulty: an overview of systematic reviews: Coloured filters for reading difficulty Suttle, Lawrenson and Conway

Coloured overlays or lenses are widely available for use by children and adults with difficulties or discomfort while reading. In recent years, systematic reviews have been conducted in an attempt to establish the strength of the evidence base for this intervention. The aim of this overview is to systematically review these reviews. The methodology was published prospectively as a protocol (Prospero CRD42017059172). Online databases Medline, Cinahl, Embase and the Cochrane Library were searched for systematic reviews on the efficacy of coloured overlays or lenses for the alleviation of reading difficulty or discomfort. Included studies were appraised using the AMSTAR 2 checklist. Characteristics of included studies such as aspects of methods, results and conclusions were recorded. Both processes were conducted independently by two reviewers and any discrepancies were resolved by discussion. Thirty‐one studies were found via databases and other sources. After excluding duplicates and those not fitting the inclusion criteria, four reviews were included in the analysis. While all reviews were systematic, their methodology, results and conclusions differed. Three of the four concluded that there is insufficient good quality evidence to support the use of coloured overlays or lenses for reading difficulty, while one concluded that, despite research limitations, the evidence does support their use. On balance, systematic reviews to date indicate that there is not yet a reliable evidence base on which to recommend coloured overlays or lenses for the alleviation of reading difficulty or discomfort. High quality, low bias research is needed to investigate their effectiveness in different forms of reading difficulty and discomfort for adults and children.

Eye care in young children: a parent survey exploring access and barriers: Survey of eye care in young children Donaldson, Subramanian and Conway

A questionnaire was designed to investigate the attitudes of parents toward eye care for their young children (4–6‐year‐olds) and possible barriers to accessing eye care for this age group. An exploration was undertaken to determine whether these beliefs and barriers are influenced by certain demographic factors such as ethnicity, level of parental income, level of parental education, confidence with speaking English and a reported family history of eye problems.