How can we improve the detection of glaucoma?
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Glaucoma, Open-Angle↗
Biomedical subjects
R P Crick
Publications and source records attributed to R P Crick.
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.
Age Factors↗
Non-contact tonometry: optometrists' current practice in England and Wales.
A survey of 133 optometrists who used a non-contact tonometer indicates that in only a half of patients tested were more than two readings per eye taken. Most optometrists made the number of readings conditional on the intraocular pressure (IOP) shown by the initial readings. About 1% of patients aged over 40 years were called back for a second IOP test. In a follow-up questionnaire with 90 respondents, only 24 (27%) stated that they had rechecked any patient by Goldmann applanation tonometry during the previous 6 months. Of these 90 optometrists, 20 (22%) had not had their tonometer serviced within the previous 24 months. It was concluded that, whilst non-contact tonometry makes a major contribution to glaucoma detection, improvements could be made in current practice which require little extra time.
Adult↗
Screening for glaucoma: the time taken by primary examiners to conduct visual field tests in practice.
A panel of 101 primary examiners (optometrists or their ancillary staff) in England and Wales prospectively recorded the time taken to examine the central visual fields of each of 10 (or more) of their patients. The results indicate that the time depended not only on the test procedure but on how frequently the examiner conducted such a test. A basic test with semi-automated field screening equipment, applied routinely by 30 examiners on 547 patients, took an average 3.7 min per patient; (lower quartile 2.8 min). For such examiners, a standard extended test took 4.9 min. Similar times applied whether tests were conducted by an optometrist or an assistant. It was concluded that visual field screening in a normal population could reasonably be assumed to take an average 4 min per patient.
Adult↗
Effect of timolol versus pilocarpine on visual field progression in patients with primary open-angle glaucoma.
BACKGROUND: Relatively few studies have been conducted linking decreasing intraocular pressure (IOP) to preservation of visual field. This investigation was conducted to determine if this link could be made and to compare the long-term effect of two ocular hypotensive agents on preservation of visual field. METHODS: In an observer-masked study, 189 patients with primary open-angle glaucoma received either timolol or pilocarpine by random allocation. The dose of antiglaucoma agent was increased from 0.25% to 0.5% twice daily for timolol or from 2% to 4% four times daily for pilocarpine if the initial IOP response was inadequate. After an on-treatment baseline, visual fields were followed every 4 months for 2 years using the Octopus program 32. RESULTS: Compared with timolol, significantly more patients receiving pilocarpine discontinued use because of inadequate IOP control (P < or = 0.01). By comparing the mean visual field scores, it can be seen that the pilocarpine group had a significantly worse score at all timepoints from month 4 to month 24. The pilocarpine group also had a greater mean number of test loci with decreased sensitivity of 5 or more decibels (dB) at all timepoints. The mean within-patient regression slope for timolol was 0.01 dB/month and for pilocarpine was -0.06 dB/month (P < 0.01). The study has shown that over a 2-year period, patients treated with pilocarpine 2% or 4% four times daily experienced a significantly greater visual field deterioration than that seen in patients receiving either 0.25% or 0.5% timolol twice daily. CONCLUSION: Although these data do not support a link between lowering of IOP and visual field preservation, treatment with timolol was associated with significantly less visual field loss than treatment with pilocarpine.
Double-Blind Method↗
Doppler carotid artery studies in asymmetric glaucoma.
Doppler carotid artery studies were performed in 12 glaucoma patients with marked asymmetry in bilateral visual field loss. The resistance index and the pulsatility index of the internal carotid artery velocity waveforms were significantly greater on the same side as the eye with the greater visual field loss. The increased resistance to blood flow in the internal carotid artery on the side with advanced field loss might predispose the eye on this side to the effects of raised intraocular pressure by causing a reduction in the perfusion pressure at the optic nerve head. The role of ocular perfusion pressure in the pathogenesis of glaucoma is discussed. More extensive studies are necessary.
Carotid Arteries↗
Screening for glaucoma: age and sex of referrals and confirmed cases in England and Wales.
This paper is based on a prospective survey covering 275,600 sight tests by optometrists in England and Wales. It analyses the age and sex distribution of 1402 referrals for suspected glaucoma and 456 confirmed cases of the disease. The proportion of sight tests which led to a confirmed case increased with age, for both sexes, to a maximum at approximately 70 years, and then tended to decline. Cases of glaucoma in people aged 36-51 years accounted for about a tenth of the total, which is more than is generally recognized. Wider adoption of routine tonometry for middle aged people would help to ensure that these cases are detected at an early stage. Confirmed cases of glaucoma in which raised intraocular pressure had not been given as a reason for referral, i.e. probable low tension glaucomas, increased from 5% of patients < 51 years old to 13% of patients > 75 years old. Glaucoma was found to be much more common in men.
Adult↗
Efficiency of referral for suspected glaucoma.
OBJECTIVE: To examine the efficiency of referral for suspected glaucoma to general practitioners and consultants by optometrists. DESIGN: A prospective survey covering 5% of all sight tests performed by optometrists in England and Wales over six months, with analysis of referred patients. SETTING: 241 optometrists' practices in areas representative of England and Wales in socioeconomic terms. SUBJECTS: Of 275,600 people attending for a sight test, 1505 were referred with suspected glaucoma (0.9% of those aged over 4%). Outcomes were recorded for 1228 patients, 1103 (90%) of whom attended for examination by a consultant ophthalmologist (8% on a private basis). The analysis was confined to the 704 cases in which the information on diagnosis was received directly from a consultant or general practitioner. MAIN OUTCOME MEASURES: Diagnoses reported by consultant ophthalmologists. Waiting times before an appointment for examination by a consultant ophthalmologist. RESULTS: Glaucoma was confirmed in 283 of the 704 referred patients, and another 222 patients were considered to require further monitoring. In all, 112 (41%) of 275 confirmed cases of glaucoma were in patients with intraocular pressures greater than or equal to 30 mm Hg. At all levels of intraocular pressure the accuracy of referral was greater when the optometrist also recorded the presence of suspicious optic discs or loss of visual field, or both; but only 331 (47%) out of the 704 referred patients had been tested with a field screener. The median waiting time for an NHS clinic appointment was nine weeks. Almost a 10th of confirmed cases of glaucoma were in people in a high risk category for glaucoma who had to wait at least 14 weeks for an appointment. CONCLUSIONS: Closer cooperation, especially at the local level, among consultants, general practitioners, and optometrists is needed to improve testing and referral for suspected glaucoma. Optometrists should be encouraged to perform all the three main tests--ophthalmoscopy, tonometry, and perimetry--in patients before referral and to report precisely on reasons for referral to help prioritisation. The optometrist's referral letter to the general practitioner should always be passed on to the consultant. Similarly, the diagnosis should always be reported back to the optometrist.
Aged↗
The progress of the visual field in chronic simple glaucoma and ocular hypertension treated topically with pilocarpine or with timolol.
It is theoretically possible that the vascular effects of topical sympathetic beta-blocking therapy in chronic simple glaucoma (CSG) might tend to neutralise the beneficial effect of a reduced intraocular pressure on the preservation of the visual field. We therefore followed the progress of 422 right eyes and 420 left eyes of 483 patients with CSG and 119 right eyes and 132 left eyes of 151 patients with an original diagnosis of ocular hypertension (OH). These patients were observed for a minimum of one year and up to 13 years, being followed for an average of 5.1 years in the case of CSG and of 4.5 years in OH. The majority of eyes with CSG were treated topically with a miotic and 38% of these received beta blocking therapy in the form of topical timolol. It was concluded that despite suggestions that beta blockers might reduce vascular perfusion of the optic nerve head, which might in turn cause an adverse effect on the visual field progress, the results of this analysis showed that there was less mean deterioration of visual field in eyes treated with beta blocker plus miotic treatment compared with those on miotic therapy alone.
Administration, Topical↗
Association between intraocular pressure and loss of visual field in chronic simple glaucoma.
This paper reports the analyses on data from 747 patients with chronic simple glaucoma (CSG) recorded in the King's College Hospital glaucoma data base between January 1970 and February 1985, having a mean follow-up time of 5.1 years (mode 8 years) with the object of determining the relationship of intraocular pressure (IOP) and visual field loss in CSG. A highly significant negative relationship was found between the presenting visual field coefficient (FC) and the untreated IOP (r = -0.26, p = 0.0001) - that is, the higher the IOP on detection, the worse is the visual field. A weak negative correlation was present between the change of FC per year and the treated IOP (r = -0.06), p = less than 0.05). At treated IOPs less than or equal to 18 mmHg visual field loss averaged 0.6 unit per year and for IOPs greater than 18 mmHg the average loss was 1.2 units per year. The data confirm both the importance of a raised IOP in the causation of chronic glaucomatous visual field loss and the importance of reducing the IOP in patients with chronic simple glaucoma.
Adolescent↗
The visual field in chronic simple glaucoma and ocular hypertension; its character, progress, relationship to the level of intraocular pressure and response to treatment.
Nine hundred and twenty-nine patients with chronic simple glaucoma or ocular hypertension were followed for one to thirteen years using the King's College Hospital glaucoma data base. The 30 degree visual field was divided into twelve clinical zones. The field sensitivity and its change as measured by the mean differential threshold both in these zones and overall was followed to determine the pattern and progress of field loss in eyes diagnosed initially as chronic simple glaucoma or ocular hypertension. The findings were related to other similar analyses in which the mean differential threshold in chronic glaucoma was found to correlate significantly with the initial intraocular pressure and its progress with the mean follow-up intraocular pressure under treatment. Inferences were drawn regarding the nature of chronic simple glaucoma and ocular hypertension and their management.
Adult↗
[Intraocular pressure and primary open-angle glaucoma. Epidemiologic technics in practice].
It is the object of this paper to familiarize the ophthalmologist with some modern epidemiological techniques and to present examples of their application to a consideration of the influence of the level of intraocular pressure on the development of the type of visual field loss characteristic of primary open angle glaucoma. Epidemiological methods are particularly required in chronic multifactorial diseases such as primary open angle glaucoma and arterial hypertension to obtain reliable guidance on practical measures for their treatment or control. Two basic requirements are reliable uniform data suitable for computer manipulation and epidemiological methods to exploit the data and yield conclusions as free of bias and confounding as possible. An example of a glaucoma data base is described and types of enquiry and the importance of standardising prevalence estimations are discussed. Analyses by the four-fold table, risk ratios, the effect of stratification, sensitivity, specifity and the decision curve are described. Attributable risk (potential for prevention) is indicated as yielding information suitable for public health programmes. The life table method is described when relating initial observations to subsequent progressive visual field loss. The factors to be considered in epidemiological work generally and the inferences concerning the early diagnosis of primary open angle glaucoma are discussed.
Age Factors↗
Risk factors for rate of progression of glaucomatous visual field loss: a computer-based analysis.
Factors affecting the progression of visual field loss were examined in 57 patients with bilateral open angle glaucoma. patients who already had marked visual field loss experienced further field loss at a greatly accelerated rate. Family history of glaucoma, sex, and initial registration intraocular pressure were also important prognostic factors for progressive visual field loss, whereas age and systemic blood pressure were not found to affect rate of visual field loss. Follow-up data from these patients were drawn from a computer-based clinic record system that may serve as a prototype for the collection of information on the natural history of ophthalmic diseases.
Age Factors↗
Effect of refractive error on the risk of ocular hypertension and open angle glaucoma.
From a case-control study of out-patients attending an ophthalmic clinic no relationship (relative risk = 1) was found between refractive error and ocular tension. The deconfounded effect of refractive error on open angle glaucoma (field loss) increased at higher levels of myopia (relative risk = 1.18; refractive error -0.2) The combined effects of myopia and severe ocular hypertension were found to be synergistic (interactive risk ratio = 2.2).
Glaucoma, Open-Angle↗
Effect of sotalol on normal intraocular pressure.
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Administration, Topical↗
Epidemiological aids to clinical decision making in primary open angle glaucoma.
We have described the epidemiological analysis of one aspect of the King's College Hospital computerized data base; namely initial intraocular pressure as an indicator of visual field loss. The methods involved the use of the four-fold table to determine sensitivity and specificity at different pressure levels. From these results (1) the changes in the pre and post test probability of field loss are calculated and (2) a 'sensitivity/specificity trade off curve' or 'decision curve' is constructed. In this way the optimal 'cut-off level' or 'operating point' for a population of specific type and composition can be determined. The factors concerned in decision making are always complex but such an approach allows a rational and quantifiable alternative to reliance on clinical impression and intuition. The results have significance in relation to decisions on the management of patients and on population screening programmes for glaucoma.
Computers↗
Blindness prevention through control of ocular hypertension: an epidemiological assessment.
From a case-control study we have quantified the effect (relative risk) of presenting intraocular pressure on visual field loss in primary open angle glaucoma. We found this effect to be modified by both age and sex. Using these effect values we have estimated the potential for prevention of glaucomatous blindness in clinical and community settings. The clinical, public health, and research implications of these findings and estimates are discussed.
Age Factors↗