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Biomedical subjects

R P Crick

Publications and source records attributed to R P Crick.

32 records · Page 2Linked to original sources
PubMed1990

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↗
PubMed1990

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↗
PubMed1989

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↗
PubMed1984

[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↗
PubMed1982

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↗
PubMed1981

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↗
PubMed1980

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↗
PubMed1980

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↗
PubMed1975

Prevention of blindness from glaucoma using the King's College Hospital computerized problem orientated medical record.

(1) Chronic glaucoma accounts for a high proportion of blindness which is preventable and calls for energetic action because existing knowledge is not applied as it should be because of the indifference of the Department of Health and Social Security to the glaucoma problem. (2) The condition is frequently insidious and advanced before being identified, and requires life-long supervision. (3) When diagnosed, the management of glaucoma is frequently inadequate and intermittent for a variety of reasons. (4) AtKing's College Hospital, a Glaucoma Centre has been initiated to supervise accurately and regularly a large number of glaucoma patients, assisted by numerical recording and computer analysis. While we are fortunate in having a computer in the hospital, it is important to emphasize that the system can be operated without this facility, either by employing manual methods, or by batch processing. It would be both possible and desirable to organize recording a nd analysis on a regional basis in collaboration with hospitals wishing to participiate. (5) Attempts are being made to improve the early diagnosis ofglaucoma by better communication between the hospital ophthalmologists, and other members of the medical, optical, and ancillary professions by lectures, demonstrations, and publications. (6) Research is always hampered by the absence of factual knowledge. It is planned to use fully the opportunity for research into glaucoma made possible by this basic organization. At present however, we consider it more important to carry out investigations into the problems of organizing the investigation, treatment, and follow-up of glaucoma patients than t o embark on a few individual projects of research. We are serously hampered in our work by shortage of funds for staff and facilities, but we look forward confidently to the time when, with the essential support of the Department of Health, these methods will give us access to the facts of glaucoma, which besides enabling us to give a high standard of treatment to our patients, will give us an unprecedented opportunity of wide ranging research into all aspects of this important disorder.

Blindness↗