Specvis: Free and open-source software for visual field examination.

Visual field impairment affects more than 100 million people globally. However, due to the lack of the access to appropriate ophthalmic healthcare in undeveloped regions as a result of associated costs and expertise this number may be an underestimate. Improved access to affordable diagnostic software designed for visual field examination could slow the progression of diseases, such as glaucoma, allowing for early diagnosis and intervention. We have developed Specvis, a free and open-source application written in Java programming language that can run on any personal computer to meet this requirement (http://www.specvis.pl/). Specvis was tested on glaucomatous, retinitis pigmentosa and stroke patients and the results were compared to results using the Medmont M700 Automated Static Perimeter. The application was also tested for inter-test intrapersonal variability. The results from both validation studies indicated low inter-test intrapersonal variability, and suitable reliability for a fast and simple assessment of visual field impairment. Specvis easily identifies visual field areas of zero sensitivity and allows for evaluation of its levels throughout the visual field. Thus, Specvis is a new, reliable application that can be successfully used for visual field examination and can fill the gap between confrontation and perimetry tests. The main advantages of Specvis over existing methods are its availability (free), affordability (runs on any personal computer), and reliability (comparable to high-cost solutions).

Screening for open angle glaucoma: systematic review of cost-effectiveness studies.

PURPOSE: To systematically review current evidence on the cost-effectiveness of screening strategies for open angle glaucoma (OAG). MATERIALS AND METHODS: Studies that reported both costs and outcomes of alternative screening strategies for OAG were identified by a highly sensitive search of electronic databases (eg, MEDLINE, EMBASE, NHS EED, HTA Database), last search December 2005. Data on costs regarding cases and years of visual impairment prevented, cases of blindness prevented, and cases of OAG detected were extracted. Incremental cost-effectiveness ratios were calculated using data provided in the included studies. RESULTS: Four studies met the inclusion criteria. The latest of these was published in 1997. The screening tests and treatments reported in these studies are now not considered to be best practice. Furthermore, data were not reported in sufficient detail to reinterpret the results of the studies in terms of a common outcome measure. Finally, these studies suffered from methodologic weaknesses that further limit their usefulness for decision making. CONCLUSIONS: Currently, there is insufficient economic evidence on which to base recommendations regarding screening for OAG. New technologies, potentially suitable as screening devices, and new treatments are available. Further research, both in terms of economic models and conduct of clinical trials with concurrent economic evaluation, may help inform policy makers regarding cost-effectiveness and acceptability of screening for OAG.

Peristat: a computer-based perimetry self-test for cost-effective population screening of glaucoma.

PURPOSE: Peristat is a virtual perimetry system that allows self-testing on any standard computer monitor via Internet connection. The sensitivity and specificity of Peristat to detect visual-field defects were compared to standard Humphrey Visual Field Analyzer data. MATERIALS AND METHODS: In this prospective, comparative observational case series, 58 eyes of 33 patients were examined. Semiquantitative analyses compared Peristat and Humphrey Visual-Field scores. The study evaluated patients with an established glaucoma diagnosis, as well as glaucoma suspects who had undergone comprehensive ophthalmologic examinations including prior office perimetry evaluation (Humphrey Field Analyzer). Inclusion criteria were (1) diagnosis or suspicion of glaucoma, (2) BCVA better than 20/200, (3) reliable performance on prior standardized office perimetry, and (4) CDR greater than 0.5. Computer literacy was not required, and more than 40% of the patients tested were computer illiterate, with no previous computer or Internet experience. A total of 58 eyes of 33 patients were tested with the Humphrey and the Peristat systems: 10 eyes of 5 patients without documented glaucomatous field loss and 48 eyes of 23 patients with mild-to-severe scotomas by standard 24-2 office perimetry. A standard computer setup was used with a 17" monitor, and the Peristat system was enabled through a remote connection with a server. RESULTS: All patients completed the Peristat test without difficulty. Testing time varied between 2 and 5 min, tending to be longer with more severe visual-field defects. Test results were reviewed, in a masked fashion, by two glaucoma specialists and one general ophthalmologist. The Peristat demonstrated a high degree of correlation with the Humphrey system. Among the three reviewers, sensitivity ranged from 80% to 83%. In a second subanalysis in which cases with mild defects were excluded, the Peristat's sensitivity increased to 84%-86% while specificity remained between 94% and 97% for all three reviewers. Patients performed the Peristat test with similar facility to their Humphrey test. Fixation losses and test reliability were comparable for both tests. CONCLUSIONS: Peristat is a reliable self-test perimetry system that demonstrates high clinical utility for the detection of visual-field defects from glaucoma. Peristat could be a valuable public health tool for cost-effective screening of glaucoma.

Estudo comparativo das diferenças entre as estratégias dinâmica e normal com o perímetro Octopus 1-2-3 / Comparative study of the differences between dynamic and normal strategies with Octopus 1-2-3

Objetivo: Analisar os resultados de um estudo comparativo entre as estratégias dinâmica e normal utilizando o perímetro Octopus 1-2-3. Métodos: Utilizando o Octopus 1-2-3 nas estratégias dinâmica e normal foi realizada a perimetria automatizada em 24 pacientes glaucomatosos (8homens e 16 mulheres) com uma média de intervalo de 2 exames de 6 meses. Todos pacientes já haviam sido previamente sunmetidos a pelo menos um exame de perimetria automatizada no Octopus 1-2-3. Os dados comparados, para ambos os olhos, foram: a idade do paciente, número de estimulos, sensibilidade média (MS), defeito médio (MD), perda focalizada (LV), flutuaçäo em curto prazo (SF) e o fator de confiabilidade (RF). Na análise estatística, utilizando o teste t pareado, somente os campos visuais com RF menor que 10 foram incluídos. O nível de significância fi igual a 5 (por cento) (p<0,05). Resultados: Näo houve diferença estatisticamente significativa entre as duas estratégias em relaçäo a idade, LV, SF e RF. Entretanto, houve diferença estatisticamente significativa na duraçäo do teste, número de estímulos, MS MD. A estratégia dinâmica mostrou uma sensibilidade difusa maior e um menor defeito médio quando comparada à estratégia normal. Conclusöes: Nossos resultados indicam que os valores dos limiares medidos pela estratégia dinâmica estäo em concordância com os valores obtidos utilizando a estratégia normal nos pacientes portadores ou suspeitos de glaucoma, cujos campos visuais estäo normais ou limítrofes. Estes resultados também confirmam a reduçäo na duraçäo do exame. Também sugerem que, quando comparamos campos visuais realizados com a estratégia dinâmica com aqueles realizados com a estratégia normal, é necessária cautela em relaçäo aos valores do MS e MD

The cost-effectiveness of various modes of screening for primary open angle glaucoma.

Various modes of screening for glaucoma were defined in terms of different combinations of the three main tests (ophthalmoscopy (O), tonometry (T), and perimetry (P)), together with associated referral criteria. The number of referrals and true positives generated by each mode was estimated for a model population, which was distributed with respect to age, intraocular pressure (IOP), optic disc condition, visual field defects, family history of glaucoma, and myopic status, as indicated by epidemiological studies. The costs of primary examination, and also of the secondary examination of referrals, were estimated for each mode, thus enabling the total cost per true positive to be calculated (in Pound sterling at 1995 UK prices, subsequently converted to US dollars at Pound 1.00 = $1.55.) The modes using O and T routinely, with P either routinely or selectively on all glaucoma high-risk groups, were found to provide the best balance between sensitivity (> or = 80%) and cost per true positive. The latter was around $850 when the cost of ophthalmoscopy could be shared as part of a general eye examination. The calculations assumed a 0.6% prevalence of previously undetected glaucomas in the community: with higher prevalences, costs per true positive would be lower. Screening the 40-59 years age group was found to be about as economic as for older people, when life expectancy was taken into account. It was concluded that glaucoma screening of people over age 40 years could be justifiable, provided that it is worth more than about $850 to detect a new case. Whilst based on UK values, the analysis could be applied to different primary health care settings in other countries.

Cost effectiveness of screening for primary open angle glaucoma.

OBJECTIVES AND SETTING: To determine the cost effectiveness of screening for glaucoma. METHODS: Information on treatment efficacy, diagnostic methods, epidemiological characteristics of glaucoma, and costs were determined from the literature, from administrative databases, and from experts. Scenarios with different screening frequency, age, participation in screening, compliance with treatment, treatment efficacy, and diagnostic tests were examined. RESULTS: The initial scenario comprised three-yearly screening of subjects aged 40-79 by funduscopy and tonometry, followed by perimetry when abnormalities were discovered. The assumption of levels of participation in screening and of compliance with treatment of 75%, and treatment efficacy of 50% resulted in a cost of $C100,000 per year of blindness prevented. A scenario in which screening was restricted to subjects aged 65-79, with the same input variables, would prevent 81% of the cases of blindness prevented with scenario 1, at a cost of $C42,000 per year of blindness prevented. Screening with tonometry only as the initial diagnostic test in subjects aged 65-79 would result in a cost of $C36,000 per year of blindness prevented, but would only prevent 59% of the cases prevented with scenario 1. CONCLUSIONS: There is as yet no proof that treatment of glaucoma or of high intraocular pressure will arrest the progression of glaucoma to blindness. Even when treatment efficacy is assumed to be as high as 50%, however, the cost effectiveness of most glaucoma screening programmes considered would not be competitive.

Test time and efficiency of the dynamic strategy in glaucoma perimetry.

The dynamic strategy is a perimetric measurement procedure where by the luminance-step sizes are optimized according to physiological data. In contrast to the traditional 4- to 2-dB strategy, the step sizes are not constant but vary between 2 and 10 dB depending on the sensitivity. We examined 40 eyes of 40 glaucoma patients with both the traditional and the dynamic strategy using a modified Octopus 1-2-3 perimeter. A total of 16 visual field locations were examined using both strategies 3 times each in alternation. The order of the initial strategy was randomized. The variance of the three measurements was calculated as a measure of reproducibility. The quantity of presented stimuli was recorded as a measure of test time. After the elimination of starting points, absolute scotomata, and series of fields showing a significant trend during the session, 255 measured locations of 27 series were available for evaluation. The mean number of presentations (indicating test time) was 46% (dynamic strategy versus traditional strategy). The variance of the three measurements depended on the sensitivity. In the normal sensitivity range, the dynamic strategy had a markedly lower variance (58%). For relative defects, the variance was higher (141%-156%). According to a benefit/cost calculation, the efficiency of the dynamic strategy was better in all sensitivity ranges and reached a factor of 3 for high sensitivities. The dynamic strategy is considerably more efficient than the traditional strategy using fixed step sizes.

Use of visual field tests in glaucoma detection by optometrists in England and Wales.

This paper is based on a survey of 241 optometrists (5% of the national total) in England and Wales, which covered many aspects of glaucoma detection. There were 45 optometrists (19%) who did not use a field screener. Of the 196 who did, 173 reported their criteria for deciding which patients to test: 17 (estimated at 8% of the original sample) used a field screener routinely in patients over 40 years; 40 (19%) selectively tested all patients with intraocular pressure > 20 mmHg, together with most others in whom any glaucoma risk factor was present, (this required a visual field test in only one in five patients aged over 40 years and may be relatively cost-effective); the remaining 116 (55%) on average tested less than one in ten of their patients with a field screener, practice which is shown to contribute little to the number of glaucomas detected. Routine field testers had the highest glaucoma detection rates, and those of the selective testers were not significantly lower.

Evaluating the applications of the spatially adaptive program (SAPRO) in clinical perimetry: Part I.

Some clinical application possibilities of a spatially adaptive program (SAPRO) are presented and analyzed. Due to the ability of the program to adapt operationally to the visual field situation that is encountered, useful clinical findings can be obtained, even in patients with complicated visual field disturbances. The spatially adaptive detection mechanism, as well as a simplified bracketing strategy, make it possible to keep the cost/benefit ratio down. Short- and long-term fluctuations, especially when these are large, may compromise the validity of the examination results or place them in doubt. Their effects can be diminished using data reduction methods (averaging). In cases where averaging cannot be applied, one can nevertheless achieve useful results by the appropriate selection of the perimetric visual fields (or portions thereof) that are measured.

Advantages and limitations of the spatially adaptive program SAPRO in clinical perimetry.

The SAPRO program devised for the OCTOPUS 201 automated perimeter, consists of a number of program components. It is designed to be used on the Octopus 201 computer. In its measurement mode, it employs an algorithm which achieves high speed and efficiency. This is made possible by a threshold bracketing strategy which is simpler than the normal OCTOPUS bracketing. Moreover, three grids with test location distributions of increasing resolution are superimposed in succession on the whole or on part of the visual field to be analyzed. Out of the distribution of test locations, only those which fulfill a number of criteria are actually utilized. These criteria must be given and are adaptable to any given clinical problem. As a result, despite the high spatial resolution achieved, only a fraction of the test locations are utilized using SAPRO as compared with a program using a fixed pattern of test locations. The algorithm is thus able to imitate human intelligence, which tends to concentrate stimuli at places which appear to be relevant for the solution of a problem. The results of program SAPRO are disturbed by short- and long-term fluctuations. Their validity is limited, in a manner similar to that encountered in any other threshold determination procedure. A number of printout modes is available which are oriented towards an optimal understanding of the information contained in various examinations. These principles will be illustrated by one case of inactive disseminated chorioretinitis.

Evaluating the usefulness in neuro-ophthalmology of visual field examinations peripheral to 30 degrees.

The value of the information obtained from Goldmann manual kinetic perimetry beyond 30 degrees was examined. Of 229 randomly selected patients in a University eye clinic who had visual fields performed for reasons other than glaucoma or ocular hypertension only 3 patients had abnormalities confined to the PVF of one or both eyes. In none of these three patients was the PVF necessary to detect disease (Graves' disease, 2 cases; retinoschisis, 1 case). The PVF was useful in determining the localization of the disorder and/or the therapeutic management in 14 patients of whom 4 of these had retinitis pigmentosa and 5 had other disorders where the PVF showed the extent of the retinal damage. For ergo-ophthalmologic purposes the PVF was useful in 45 patients; most frequently because the extent of abnormality provided a basis for warning the patient. In some cases the PVF was considered to be useful for economic disability determination or to exclude significant PVF defects in a patient with only one visually useful eye. In 77 patients the PVF of each eye was abnormal but not of ergo-ophthalmologic significance. If these data can be extrapolated to automated static perimetry, there will be a very great incremental cost for any clinically useful information obtained from the examination of the PVF. Because the cost-effectiveness of the examination must be compared with competing methods of obtaining information, it is proposed that the PVF be examined (1) whenever indicated for ergo-ophthalmologic reasons, or (2) when the CVF examination does not resolve a clinical problem for which there is a reasonably high probability that (a) additional clinically useful information will be obtained by examination of the PVF after the results of the CVF examination have been analyzed, or (b) the eye is likely to have a condition that can be detected or followed best by PVF examination.

Screening for visual field abnormalities with automated perimetry.

Recent studies indicate that automated perimetry can serve as an effective method of screening for visual field abnormalities associated with ophthalmologic and neurologic disorders. The techniques have been successfully applied to the private practitioner's office for screening of patients and to mass visual field screening of the general population. This paper describes the principles underlying automated perimetric screening, evaluates the capabilities and limitations of such techniques, and provides some general guidelines for using automated perimetric screening procedures.

Cost-benefit analysis in screening. Unexplained visual loss.

Cost-effectiveness analysis (CEA) and cost-benefit analysis (CBA) are accounting techniques that have been applied to medical decision-making. These techniques are applied here to two alternative diagnostic strategies in the work-up of patients with "unexplained visual loss." The first uses the results of visual field examination to decide if patients should have a CT scan ("visual field strategy"), the second bypasses visual fields and orders a CT scan on all patients ("CT strategy"). The analysis reveals that the visual field strategy is cost-effective only if perimetrists are able to identify hemianopic field defects in more than 80% of cases. It is doubtful that perimetrists are presently as accurate as that. These conclusions must be considered tentative since the epidemiologic data that support them are often weak. Another drawback in applying such an analysis to medical problem-solving is that costs may not accurately reflect patient valuations and choices. Nevertheless, in forcing a more comprehensive consideration of the effects of medical decisions, CEA/CBA is likely to promote increased cost-consciousness and epidemiologic research.

Glaucoma screening. A cost-effectiveness analysis.

We designed an intricate model of the process of glaucoma screening, diagnosis, and treatment in order to evaluate the medical care costs of such efforts in relation to the benefits in terms of quality-adjusted years of vision saved, utilizing the economic principles of cost-effectiveness analysis. Although a relatively limited data base and numerous assumptions concerning the accuracy of diagnostic tests, the natural history of ocular hypertension and glaucoma, and the effectiveness of available treatment modalities, limit our ability to draw definitive conclusions concerning the cost-effectiveness of various glaucoma screening options, our analysis indicates that glaucoma screening is probably cost-effective when targeted at certain subgroups of the population. Our analysis suggests that changes in several aspects of existing screening policies may be appropriate if cost-effectiveness is to be used as one of the criteria for the efficient allocation of resources to and within screening programs. Specifically, combinations of screening tests and screening targeted at high risk populations such as blacks, diabetics, and relatives of glaucoma patients are probably more cost-effective than screening of the general population with a single test. In younger populations, the importance of detecting ocular hypertension argues for the use of tonometry. Ophthalmoscopy may be more cost-effective in older age groups in whom the higher prevalence of glaucoma outweighs the need for identifying ocular hypertensives. In the very elderly, automated perimetry becomes cost-effective since the detection of established field loss will have greater yield. In addition, it is evident that diversion of resources away from actual screening efforts and towards efforts aimed at improving follow-up and compliance would be an additional cost-effective strategy.