The effect of visual field defects on eye movements and practical fitness to drive

Eye movements of subjects with visual field defects due to ocular pathology were monitored while performing a dot counting task and a visual search task. Subjects with peripheral field defects required more fixations, longer search times, made more errors, and had shorter fixation durations than control subjects. Subjects with central field defects performed less well than control subjects although no specific impairment could be pinpointed. In both groups a monotonous relationship was observed between the visual field impairment and eye movement parameters. The use of eye movement parameters to predict viewing behavior in a complex task (e.g. driving) was limited.     

Integrated visual fields: a new approach to measuring the binocular field of view and visual disability

Background We have developed a method of quantifying the central binocular visual field by merging results from monocular fields (Integrated visual field). This study aims to compare the new measure with the binocular Esterman visual field test in identifying patients with self-reported visual disability.Methods Forty-eight patients with glaucoma each recorded Humphrey 24-2 fields for both eyes and an Esterman on the same day, and each completed a binary forced-choice questionnaire relating to perceived visual disability. Computer software merged sensitivity values from monocular fields to generate an integrated visual field and a related score of the number of defects at the <10 dB and <20 dB level. Receiver operating characteristic (ROC) analysis was used to compare the integrated visual field score and the Esterman disability score with individual responses to the questions on perceived difficulty with visual tasks.Results Comparison of areas under ROC curves revealed that a score based on the integrated visual field was generally better (median area: 0.79) than Esterman scores (median area: 0.70) in classifying patients with or without a self-reported perceived difficulty with visual tasks.Conclusions The integrated visual field offers a rapid assessment of a glaucoma patients binocular visual field without extra perimetric testing. As compared to an actual binocular field test (Esterman), the integrated visual field provides a better prediction of a glaucoma patients perceived inability to perform certain visual tasks.     

Glaucoma and fitness to drive: using binocular visual fields to predict a milestone to blindness

PURPOSE: To use binocular integrated visual field (IVF) measures to predict which patients will lose visual function to a level below the legal standard for driving. METHODS: Data from patients attending a glaucoma clinic were collected longitudinally. The time from baseline until failure to meet the criteria of the driver's license test was modeled with Cox regression. Visual field status at baseline and visual field deterioration rate at 2 years from baseline for various monocular and binocular VF indices were investigated as predictor variables. The model that provided the best fit to the data was validated using bootstrap resampling. RESULTS: Of the patients, 20% (60/299; 95% confidence interval, 16%-25%) failed to meet the visual field criteria to prevent driver's license loss during an average follow-up of 7 years. The median age of patients was 64 years. The binocular IVF measurements gave a better fit to the observed data than the monocular measurements. Initial average visual field sensitivity and rate of visual field loss of sensitivity were significant predictors of failure to meet driver's license test criteria. CONCLUSIONS: The IVF provides a method by which binocular visual fields can be incorporated into patient management and allows, for example, a prediction of future driver's license loss. The rate of binocular IVF sensitivity loss at 2 years of follow-up may help identify patients who could benefit from intensified intervention.     

Visual fitness to drive after stroke or head injury

The visual requirements for driving in Britain are outlined and how they might be compromised following stroke or head injury examined. The role of the optometrist in assessing such patients who wish to resume driving is discussed. Topics discussed include legal considerations, the relationship between visual problems and driving ability and the vision-testing techniques that are most appropriate for use with the brain injured. An illustrative case history is presented.     

Practical recommendations for measuring rates of visual field change in glaucoma

To date, there has been a lack of evidence-based guidance on the frequency of visual field examinations required to identify clinically meaningful rates of change in glaucoma. The objective of this perspective is to provide practical recommendations for this purpose. The primary emphasis is on the period of time and number of examinations required to measure various rates of change in mean deviation (MD) with adequate statistical power. Empirical data were used to obtain variability estimates of MD while statistical modelling techniques derived the required time periods to detect change with various degrees of visual field variability. We provide the frequency of examinations per year required to detect different amounts of change in 2, 3 and 5 years. For instance, three examinations per year are required to identify an overall change in MD of 4 dB over 2 years in a patient with average visual field variability. Recommendations on other issues such as examination type, strategy and quality are also made.     

Using unsupervised learning with independent component analysis to identify patterns of glaucomatous visual field defects

PURPOSE: Clustering by unsupervised learning with machine learning classifiers was shown to segment clusters of patterns in standard automated perimetry (SAP) for glaucoma in previous publications. In this study, unsupervised learning by independent component analysis decomposed SAP field patterns into axes, and the information represented by these axes was evaluated. METHODS: SAP fields were used that were obtained with the Humphrey Visual Field Analyzer (Carl Zeiss Meditec, Dublin, CA) from 189 normal eyes and 156 eyes with glaucomatous optic neuropathy (GON) determined by masked review with stereoscopic optic disc photographs. The variational Bayesian independent component analysis mixture model (vB-ICA-mm) partitioned the SAP fields into the most informative number of clusters. Simultaneously, the model learned an optimal number of maximally independent axes for each cluster. RESULTS: The most informative number of clusters in the SAP set was two. vB-ICA-mm placed 68.6% of the eyes with GON in a cluster labeled G and 98.4% of the eyes with normal optic discs in a cluster labeled N. Cluster G optimally contained six axes. Post hoc analysis of patterns generated at -1 SD and +2 SD from the cluster G mean on the six axes revealed defects similar to those identified by experts as indicative of glaucoma. SAP fields associated with an axis showed increasing severity, as they were located farther in the positive direction from the cluster G mean. CONCLUSIONS: vB-ICA-mm represented the SAP fields with patterns that were meaningful for glaucoma experts. This process also captured severity in the patterns uncovered. These findings should validate vB-ICA-mm as a data-mining technique for new and unfamiliar complex tests.     

A new technical approach to monkey visual training

To train the monkey for visual task we use the microcomputer and a bicoloured LED. This system is very advantageous in respect of its low cost and the ease of use.     

Detection of visual field progression in glaucoma with standard achromatic perimetry: A review and practical implications

Detection of visual field progression remains a challenging task despite the recent advances for better handling of longitudinal visual field data, some of which are incorporated in currently available perimeters. Standard achromatic perimetry remains the gold standard for detection of visual field progression. The authors present a practical and clinically relevant review of the main issues involved in detection of early glaucoma as well as detection of visual field progression in eyes with pre-existing glaucomatous damage. After discussing some basic concepts in perimetry, the authors present evidence-based recommendations for criteria to detect earliest evidence of glaucomatous damage with perimetry. The authors will review different event- and trend-based criteria and present data with regard to comparative performance of such criteria. Relevance of using absolute versus corrected threshold data with regard to different criteria is also addressed. At the end, the authors provide practical guidelines for detection of visual field progression in a clinical setting and review issues related to clinical trials.     

Detection of visual field defects in patients after anterior temporal lobectomy for mesial temporal sclerosis-establishing eligibility to drive

AIMS: The aim of this study is to quantify visual field defects after temporal lobectomy for mesial temporal sclerosis and to establish eligibility for driving. METHODS: Automated static perimetry was performed on 14 patients who had undergone anterior temporal lobectomy for mesial temporal sclerosis. Perimetry consisted of monocular Humphrey Field Analyser (HFA) 30-2 test and a binocular Esterman 120 test. RESULTS: Of the 14 patients, three had no loss or non-specific loss, eight had partial homonymous quadrantanopia, one had complete homonymous quadrantanopia and two had concentric loss attributable to vigabatrin, which may have masked any loss occurring due to surgery. Of these, only seven passed the standardised DVLA visual fields. Of the seven who failed DVLA visual field, one had complete quadrantanopia, four had partial quadrantanopia and two had concentric loss (due to vigabatrin). CONCLUSIONS: Visual field defects contribute a great deal in the reduction of the quality of life in patients who have had surgery for mesial temporal sclerosis. Potential surgically induced visual field defects that could preclude driving need to be discussed with each patient preoperatively. In our study 50% of patients did not meet the required DVLA standards.     

正常人周边区与中央区图形翻转视觉诱发电位的对比研究

目的了解视觉系统正常人周边区与中央区图形翻转视觉诱发电位的变化规律。方法以图形翻转视觉诱发电位作为研究工具,观察正常人30°以外的上方、下方、鼻侧、颞侧四个方向周边区与中央区的PVEP的波形特征。结果正常人的周边VEP在这四个方向上的N_(75)、P_(100)的潜伏期均随空间频率的增大而增大;N_(75)-P_(100)的峰峰值却有一个最适的空间频率,即N_(75)-P_(100)的峰峰值只在这个最适空间频率下最大;另外周边区VEP N_(75)、P_(100)的潜伏期均较中央区VEP N_(75)、P_(100)的潜伏期明显延长,周边区VEP N_(75)-P_(100)的峰峰值均较中央区VEP N_(75)-P_(100)的峰峰值低。结论正常人周边区与中央区图形翻转视觉诱发电位的是两种不同机制。     

Updating the classical approach to visual acuity

The classical account of visual acuity incorporates optical, anatomical and physiological components. Knowledge of these helps to put into perspective recent scientific advances that have clinical implications. They include the development of active optical devices for neutralising aberrations in peripheral zones of the pupil, with the potential of improving the eye's imagery beyond its customary limit. In another application of modern optical and electronic instrumentation, the quality of retinal images in young eyes has been compared with that in the aged. This has led to a better understanding of the choice of contrast patterns to enhance visual acuity in older patients.