Automatic optometer for use with the undrugged human eye.
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Adult↗
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The eye as an optical instrument: from camera obscura to Helmholtz's perspective.
The era of modern vision research can be thought of as beginning in the seventeenth century with Johannes Kepler's understanding of the optics of the camera obscura with a lens and its relation to the eye. During the nineteenth century, Helmholtz used "The eye as an optical instrument" as the title for one of his Popular Lectures, and such a conception of the eye is now accepted as a fundamental feature of visual science. In analysing the optics of the eye, Helmholtz constructed some novel optical instruments for studying the eye. The development of optometers, ophthalmometers, and ophthalmoscopes is presented historically, with emphasis on how these instruments and camera analogies helped scientists to understand the functions of the eye, especially the enigma of accommodation. "The laws of optics are so well understood, and the knowledge of the eye, when considered as an optical instrument, has been rendered so perfect, that I do not consider myself capable of making any addition to it; but still there is a power in the eye by which it can adapt itself to different distances far too extensive for the simple mechanism of the parts to effect." (John Hunter in a letter to Joseph Banks in 1793, published by Home 1794, page 24).
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Preliminary report: prescription of prism-glasses by the Measurement and Correction Method of H.-J. Haase or by conventional orthoptic examination: a multicenter, randomized, double-blind, cross-over study.
In a multicenter, randomized, double-blind, cross-over study in the Netherlands, the effectiveness of (prism-)glasses prescribed by the Measurement and Correction Method of H.-J. Haase (MKH) was compared to that of glasses prescribed by conventional orthoptic examination. Nine pairs of MKH-optometrists and orthoptists recruited patients who primarily presented with asthenopia, and each prescribed the patient (prism-)glasses. A questionnaire for asthenopia was developed that rated headache and tired eyes as 0-7 days per week and none-light-medium-severe, respectively. Light sensitivity, problems with focusing, near-work problems and burning eyes were each rated as: never-occasionally-often-always. A patient was eligible if he scored 'medium', 'often' or '5 days a week' twice; or 'medium' (etc.) once and 'light' (etc.) twice. Controls, in contrast to the patients, typically answered 'none' or 'never' to half of the complaints, but 37% of them would have passed the admission criteria. Among other criteria were: 18 to 40 years of age, horizontal angle < 4 degrees, vertical < 1.7 degrees, acuity > or = 0.8, stereopsis threshold disparity < 120". Seventy-two patients fulfilled all criteria and returned sufficient questionnaires. They wore the first glasses for six weeks, were without glasses for two weeks, and then wore the second glasses for six weeks. At the start, halfway and at the end of each 6-week period, questionnaires were filled out; 97% were returned. Only 19 of the orthoptists' glasses contained prisms (14 horizontal, 5 vertical; horizontal average of all glasses 0.49 PD, vertical 0.05 PD). Five of the orthoptists' glasses were plano. All MKH glasses contained prisms, 53 of 72 both horizontal and vertical, 18 only horizontal and one only vertical (horizontal average of all glasses 2.83 PD, vertical 0.79 PD). The starting levels of complaints were high and both glasses improved complaints dramatically. The starting levels were lower, but not significantly, in the second 6-week period and improvement was less outspoken. Because of these differences, the two periods had to be evaluated separately. The primary outcome of the study was defined as the difference between the effect of the MKH glasses and that of the orthoptists' glasses in the first and second 6-week periods. For problems with focusing, in the first 6-week period, and for tired eyes, in the second 6-week period, the difference exceeded the difference that had been defined as clinically significant (one day per week less headache or half the distance light-medium or half the distance occasionally-often), but it did not reach statistical significance. The statistical power was approximately 0.7 for demonstrating this clinically significant difference. Statistical significance was not reached in multivariate repeated measure ANOVA either. Forty-four patients preferred to keep the MKH glasses, 25 the orthoptists' glasses, including one plano. It is striking that 25% of the patients did not prefer the glasses that, according to the questionnaire, improved their complaints the most. A year after the study, the questionnaire was sent again to all patients: The levels of complaints after a year were similar to those at the end of the second 6-week period, whether they had preferred the MKH or the orthoptists' glasses, and were similar to the levels in controls. The most conspicuous finding was that both glasses improved the complaints dramatically. Apart from the prisms, other reasons could be: spherical and cylindrical correction, improved wearing comfort of the frame, placebo effect, Hawthorne effect and regression to the mean.
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Bankruptcy proceedings against William Harris, Optician, of Cornhill, 1830.
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Bankruptcy↗
The potential impact of a national diabetic retinopathy screening programme on a department of medical illustration.
Diabetic retinopathy screening programmes in the UK vary tremendously in quality, methods used, and frequency of screening. Indeed, many areas have no local screening service at all. The United Kingdom National Screening Committee has compiled and published a series of recommendations for a national risk reduction programme for diabetic retinopathy based on a screening programme. This paper will examine the primary recommendations of the committee and use the diabetic retinopathy screening programme currently running at Brighton Health Care NHS Trust as a model to demonstrate the potential impact the recommendations may have on an established programme. This will also give some indication of the resources required for any department not currently running a service.
Diabetic Retinopathy↗
Do generalized visual training programmes for sport really work? An experimental investigation.
We assessed the effectiveness of two generalized visual training programmes in enhancing visual and motor performance for racquet sports. Forty young participants were assigned equally to groups undertaking visual training using Revien and Gabor's Sports Vision programme (Group 1), visual training using Revien's Eyerobics (Group 2), a placebo condition involving reading (Group 3) and a control condition involving physical practice only (Group 4). Measures of basic visual function and of sport-specific motor performance were obtained from all participants before and immediately after a 4-week training period. Significant pre- to post-training differences were evident on some of the measures; however, these were not group-dependent. Contrary to the claims made by proponents of generalized visual training, we found no evidence that the visual training programmes led to improvements in either vision or motor performance above and beyond those resulting simply from test familiarity.
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The evolution of an eye care program at a university health service.
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Eye Diseases↗
Normal periocular anthropometric measurements in the Turkish population.
PURPOSE: To evaluate the ocular and periocular anthropometric measurements of Turkish subjects. METHODS: Corneal diameter, horizontal and vertical palpebral fissure, vertical brow-nasal distance, inter-outer canthal distance, inter-inner canthal distance, inter-pupillary distance, bridge height, lid crease, brow height, levator function, head circumference and interorbital distance were measured in 706 eyes of 353 subjects. RESULTS: In men, the mean corneal diameter was 10.5 mm, horizontal palpepral fissure was 30.0 mm, vertical palpepral fissure was 9.7 mm, vertical brow-nasal distance was 36.9 mm, inter-outer canthal distance was 91.3 mm, inter-inner canthal distance was 30.7 mm, inter-pupillary distance was 60.6 mm, nasal bridge height was 4.7 mm, lid crease was 6.0 mm, pre-tarsal skin height was 2.3 mm, brow height was 9.7 mm, levator function was 14.4 mm, interorbital distance was 99.1 mm and head circumference was 58.0 cm. In female subjects these measurements were 10.3 mm, 30.0 mm, 9.9 mm, 35.1 mm, 90.1 mm, 30.2 mm, 60.1 mm, 4.3 mm, 5.9 mm, 2.1 mm, 9.9 mm, 14.6 mm, 95.8 mm and 55.9 cm, respectively. CONCLUSION: In this study we obtained the anthropometric measurements of ocular and periocular structures in Turkish subjects. Knowledge of normal values in a population can be important in the manufacture of spectacles and in clinical and surgical practice.
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The effect of an ergonomic intervention on musculoskeletal, psychosocial and visual strain of VDT data entry work: the Norwegian part of the international study.
The Norwegian MEPS (musculoskeletal--visual--psychosocial--stress) study included 3 groups: data entry, data dialogue (female) and data dialogue (male). Before intervention, the data entry group reported significantly more symptoms and signs of musculoskeletal illness and had longer periods in front of the video display terminal (VDT) without a break. The ergonomic intervention consisted mainly of ergonomic information and training. After intervention, the data dialogue female group reported a significant reduction in shoulder pain in parallel with a reduction in trapezius load. Increasing the understanding in how to adjust the work stand and chair may have been contributing factors to reducing the pain level. There was a significant reduction in eye problems in all groups; the greatest reduction in eye symptoms was seen in the groups who had new optometric corrections.
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The effect of an ergonomic intervention on musculoskeletal, psychosocial, and visual strain of VDT data entry work: the United States part of the international study.
The United States MEPS (musculoskeletal--eyestrain--psychosocial--stress) study consisted of 1 group of 28 female data entry operators. The intervention was in 3 parts: workstation redesign (including advanced ergonomic chairs, motorized adjustable workstations, advanced adjustable keyboards, adjustable copyholders, adjustable footrests, monitor support surfaces) and ergonomic training/coaching and corrective lenses. After the intervention, statistically significant reductions in physical signs (trigger points, neck and shoulder mobility), subjective reports of intensity and frequency of musculoskeletal pain, and subjective reports of visual problems were observed. Static load during the work sample, as assessed by experts, improved after the intervention as did measured postural angles of head and trunk and subjective assessment of users of ergonomic characteristics of the workplaces. For all of these measures, improvements observed 1 month after intervention were also observed in the 1-year follow-up. Trapezius load, as assessed by electromyography (EMG), decreased after intervention, but then increased in the follow-up. The increase was interpreted as a calibration problem.
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A cross-country comparison of short- and long-term effects of an ergonomic intervention on musculoskeletal discomfort, eyestrain and psychosocial stress in VDT operators: selected aspects of the international project.
Three groups of data entry female visual display terminal (VDT) workers from Norway (n = 30), Poland (n = 33) and the USA (n = 29) were compared. Before intervention, the Norwegian group reported more neck pain compared with the Polish group. The Polish group reported less shoulder pain than both the U.S. and the Norwegian groups. The clinical examination documented fewer symptoms and signs of musculoskeletal illness among the Polish participants compared with the Norwegian and the U.S. groups. After intervention, the Norwegian group reported a reduction in neck pain while the U.S. group reported a reduction in shoulder pain. The Polish group reported an increase in neck, shoulder and forearm pain at follow-up compared to after intervention. The Polish group recorded higher flexion of the upper arm at follow-up parallel with an increase of pain in the upper part of the body. Visual discomfort showed variable results in the 3 countries.
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Performance characteristics of digital fundus photography as a screening test for diabetic retinopathy in a low-risk population.
The purpose of the present study was to estimate the sensitivity and specificity of reviewers' assessments of digital fundus photography (DFP) images, using the findings from comprehensive ophthalmologic examination as the criterion standard. One hundred and fifty-two patients with diabetes underwent comprehensive ophthalmologic examination by an active duty U.S. Air Force (ADAF) staff ophthalmologist, and the examination findings were used as the criterion standard for the present study. Eight other ophthalmologists (M.D.'s) and 10 optometrists (O.D.'s), all ADAF providers, each evaluated seven nonstereo standard field DFP images from the left and right eyes (14 images per patient) of the 152 diabetic patients, assessing each patient for evidence of diabetic retinopathy (yes, no, not sure). The sensitivity, specificity, and proportion of "not sure" responses were computed separately for MD and OD reviewers and then compared. O.D. reviewers gave "not sure" responses more frequently than M.D.'s. With "not sure" responses treated as correct (i.e., identical to the results of ophthalmologic examination), both types of providers had 100% sensitivity for cases that are usually treated and 83% sensitivity for cases that are not usually treated but require close follow-up. Specificity (for any diabetic retinopathy) was 92% for M.D.'s and 93% for O.D.'s. With M.D.'s as photographic reviewers, DFP-based screening required only 27 ophthalmologic examinations per 100 patients screened; with O.D.'s as photographic reviewers, 31 ophthalmologic examinations were required per 100 patients screened. Using either ophthalmologists or optometrists as photographic reviewers, DFP-based screening for diabetic retinopathy has very good sensitivity and excellent specificity.
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The Bristol Shared Care Glaucoma Study--validity of measurements and patient satisfaction.
BACKGROUND: The aims of the study were to determine (1) whether community optometrists are able to make valid measurements of visual parameters in patients with established or suspect primary open angle glaucoma and (2) patient satisfaction with follow-up by community optometrists. METHODS: A randomized study was carried out in the former county of Avon in South West England with patients allocated to follow-up by the hospital eye service or by community optometrists. The subjects were 403 patients with established or suspected primary open angle glaucoma attending Bristol Eye Hospital and meeting defined inclusion and exclusion criteria. The main outcome measures were 91) measurements of key visual parameters (intraocular pressure, visual fields and cup/disc ratio) made by hospital eye service and community optometrists, compared with a research clinic reference standard at baseline, and (2) patient satisfaction at baseline and at six months. RESULTS: Community optometrists were able to make measurements of comparable accuracy to those made in the hospital eye service. Patients were significantly more satisfied with a number of aspects of care provided by community optometrists, particularly those relating to waiting times, compared with those from the hospital eye service. CONCLUSIONS: Community optometrists are able to make measurements of key visual parameters in patients with established or suspect primary open angle glaucoma which are of comparable quality to the hospital eye service. Follow-up by community optometrists is acceptable to patients. The costs of each option are reported elsewhere.
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An evaluation of diabetic retinopathy screening models.
BACKGROUND: The aim of the study was to evaluate three models of diabetic retinopathy screening in a North London Health Authority so as to advise on setting up a comprehensive screening programme. The study evaluated the models against their own objectives and standards published by the British Diabetic Association (BDA) and the Royal Colleges for diabetic retinopathy screening, and assessed service user and provider satisfaction. METHODS: Methods used were: analysis of the patient database and a case note review on uptake and coverage; follow-up for abnormal findings; comparisons of positive predictive values; postal questionnaire survey of service user satisfaction; semi-structured interviews of service providers. RESULTS: A total of 2230 people with diabetes were screened between March 1998 and August 2000. The general practitioner (GP) led model achieved 63 per cent coverage and the two optometrist models 24 per cent. The detection rate for sight-threatening diabetic retinopathy was 6 per cent and 2.5 per cent for the optometrists and GP models, respectively. Positive predictive values of 94 per cent, 90 per cent and 60 per cent, respectively, were established for the GP-led model, the optometrists using the retinal camera and the optometrists using indirect ophthalmoscopy only. Twenty-eight (45 per cent) of the 62 people with sight-threatening diabetic retinopathy failed to attend for further investigation. Service user and service provider satisfaction were high for all three models. CONCLUSION: The evaluation confirmed that all three methods of screening provided an effective service. The implementation of a district-wide diabetic retinopathy screening programme requires the establishment of a systematic call and recall system to achieve attendance for screening. A formal follow-up of people referred for specialist assessment and treatment should be part of the service.
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The TMS-1 corneal topography measurement applied to calibrated ellipsoidal convex surfaces.
The purpose of this report is to assess the accuracy of the TMS-1 videokeratoscope (Computed Anatomy Inc.) by using convex ellipsoidal surfaces. The ellipsoids were calibrated using Form Talysurf analysis, which allowed for subsequent calculation of the vertex radius and p value. The videokeratoscope was used to examine the same ellipsoids. The data provided by the instrument software were used to plot a graph of r2 verses y2, where r is the measured radius at y, the distance from the corneal point being measured to the optical axis of the instrument. The intercept on the ordinate of this graph gives the vertex radius, and the slope give the p value. The results arising from the Talysurf and the TMS-1 techniques were compared. The TMS-1 videokeratoscope gave readings for the vertex radius that were generally higher than those of the Talysurf analysis. The vertex radius was up to 0.09 mm greater. The p value results were similar by the two methods for p values of approximately 0.8; however, the TMS-1 results were higher, and the discrepancy increased as the p value approached that of a paraboloid. Although the videokeratoscope may be useful in comparative studies of the cornea, there must be some doubt about the absolute values displayed as the surface becomes increasingly aspheric.
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Survey of preferred tests for diagnosis of the tear film and dry eye.
PURPOSE: To survey practitioners in the tear film/dry eye field for their preferred diagnostic methods for the evaluation of the tear film and dry eye syndrome. METHODS: A survey was given to 36 optometrists and 41 ophthalmologists with backgrounds in the area of tear film and dry eye syndrome to find their preferred test if only one diagnostic option was available for tear film evaluation. Second, third, and fourth choices were also recorded, as well as any additional comments. RESULTS: Sixty-eight practitioners completed the survey. No one single test was a dominant first choice of the majority of respondents in either profession. History and/or dry eye questionnaire was the most frequent response to the question addressing the use of only one test (28%). The second most frequently chosen test was fluorescein break-up time (FBUT) (19%), followed by fluorescein staining (13%), and rose bengal (10%). The Schirmer test was most frequently included as one of the four choices (62%), although it was the first choice of only 9%. CONCLUSION: The importance of multiple tests in the evaluation of tear film disorders is overwhelmingly acknowledged, with patient history/dry eye questionnaires, FBUT, ocular surface staining, and the Schirmer test being the preferred diagnostic tools.
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Characterization of ocular surface symptoms from optometric practices in North America.
PURPOSE: This study characterized ocular symptoms typical of dry eye in an unselected optometric clinical population in the United States and Canada. METHODS: Self-administered dry eye questionnaires, one for non-contact lens wearers (dry eye questionnaire) and one for contact lens wearers (contact lens dry eye questionnaire), were completed at six clinical sites in North America. Both questionnaires included categoric scales to measure the prevalence, frequency, diurnal severity, and intrusiveness of nine ocular surface symptoms. The questionnaires also asked how much these ocular symptoms affected daily activities and contained questions about computer use, medications, and allergies. The examining doctors, who were masked to questionnaire responses, recorded a nondirected dry eye diagnosis for each patient, based on their own diagnostic criteria. RESULTS: The dry eye questionnaires were completed by 1,054 patients. The most common ocular symptom was discomfort, with 64% of non--contact lens wearers and 79% of contact lens wearers reporting the symptom at least infrequently. There was a diurnal increase in the intensity of many symptoms, with symptoms such as discomfort, dryness, and visual changes reported to be more intense in the evening. The 22% percent of non-contact lens wearers and 15% of contact lens wearers diagnosed with dry eye (most in the mild to moderate categories) reported symptoms at a greater frequency than those not diagnosed with dry eye. CONCLUSIONS: Our results show that symptoms of ocular irritation and visual disturbances were relatively common in this unselected clinical population. The intensity of many ocular symptoms increased late in the day, which suggested that environmental factors played a role in the etiology of the symptoms.
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A profile of keratoconus in New Zealand.
PURPOSE: To examine the characteristics and risk factors for keratoconus in a New Zealand population. METHODS: A one-page questionnaire was designed and sent to optometrists and ophthalmologists in New Zealand. Eye care practitioners then issued questionnaires to their keratoconic patients over a 6-month period. RESULTS: A total of 673 completed questionnaires were received from patients with keratoconus. A male bias (59%) was apparent in the sample. In line with previous work, a high proportion of the keratoconic cohort rubbed their eyes and suffered from atopy. A familial rate of 23.5% was evident, with several families reporting multiple keratoconus cases. Eleven pairs of twins were identified with at least one keratoconic sibling. Multivariate statistical analysis revealed significant independent correlations between the early development of keratoconus and gender, allergy, asthma, and latitude of childhood domicile. CONCLUSION: Results from the survey concur with a previous local report that keratoconus affects males more frequently and earlier in life than females in New Zealand. The concurrence of atopic disease and eye rubbing with keratoconus was as expected, and an association between the early development of the disease and latitude of the childhood domicile emerged. A strong familial component, exceeding previously reported figures, was evident in the cohort.
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