Biomedical subjects

S A Vernon

Publications and source records attributed to S A Vernon.

At least 19 recordsLinked to original sources

PubMed1992

Demand incidence and episode rates of ophthalmic disease in a defined urban population.

OBJECTIVES: To estimate demand incidence and episode rates of ophthalmic disease in a defined urban population over one year. DESIGN: Study of patients presenting with eye problems to general practice and eye casualty department. SETTING: General practice and ophthalmic services in west Nottingham. SUBJECTS: 36,018 people from the combined practice lists of 17 Nottingham general practitioners. MAIN OUTCOME MEASURES: Ophthalmic disorder, age and sex of patient, and where presented. RESULTS: 587 consultations were recorded for ophthalmic problems, 1771 with general practitioners and 816 with eye casualty. Most consultations to general practice were by females (1066 (60%)), whereas men aged 15-44 accounted for most work in eye casualty. These men commonly presented with trauma. Infective conjunctivitis, the commonest condition, had an episode rate of 13.5/1000 population/year. Demand incidence for cataracts was 1.9/1000 population/year. Demand incidence for chronic conditions increased with age. CONCLUSIONS: As the average age of the population increases demand for ophthalmic services will rise. Planning and provision of resources to meet this increased demand should be considered now.

Age Factors↗

PubMed1992

Study of diagnostic accord between general practitioners and an ophthalmologist.

OBJECTIVES: To identify diagnostic accord and disagreement between general practitioners and an ophthalmologist and thereby determine how undergraduate and non-specialist postgraduate ophthalmic training could be improved. DESIGN: Comparison of diagnosis of presenting conditions by general practitioners and one ophthalmologist in patients consulting general practitioners for ophthalmic problems during March 1989 to February 1990. SETTING: 12 general practices in west Nottingham. PATIENTS: 1474 patients presenting to the study general practitioners with new ophthalmic conditions or new episodes of recurrent conditions. MAIN OUTCOME MEASURES: Diagnoses of general practitioners and ophthalmologist. RESULTS: 1121 (76%) of patients with eye problems agreed to see the ophthalmologist and most were seen within three days. Sufficient data for comparison were available on 1103 patients. Diagnostic agreement was found in 638 cases (58%), but potentially serious misdiagnosis was found in only 15 cases; management in three of these cases would have ensured later identification. Most commonly confused conditions were infective and allergic conjunctivitis, blepharitis, and dry eyes. General practitioners assessed visual acuity in only 114 cases yet eight of the 15 patients seriously misdiagnosed had reduced acuity, an important diagnostic sign. CONCLUSIONS: Most ophthalmic disease seen in general practice does not require specialised equipment for diagnosis. Most cases of misdiagnosis have no serious consequences for the patient. Undergraduate and postgraduate training in ophthalmology should ensure that common conditions can be easily differentiated and more serious conditions identified and referred.

Clinical Competence↗

PubMed1992

A comparison of the OKP visual field screening test with the Humphrey field analyser.

In order to determine the loss of retinal sensitivity detectable by oculokinetic perimetry (OKP), we tested 27 eyes of 27 persons with glaucoma and 32 eyes of 32 patients with ocular hypertension with the OKP screener and with a central threshold test on the Humphrey analyser. The threshold at eight locations on the OKP chart between 12.5 degrees and 15 degrees from fixation was compared with the corresponding Humphrey perimetric thresholds. Seventeen eyes from 17 patients with glaucoma failed the OKP screening test by not seeing the target at one or more locations. The mean light sensitivity threshold at points seen on OKP screening was -5.8 dB (SD 4.6 dB) from aged-matched normals (AMN), whereas points missed had a mean threshold -16.1 dB (SD 9.3 dB) from AMN. The sensitivity and specificity with which OKP testing differentiated normal points from abnormal ones in Humphrey testing was 82.5% and 80% respectively, with a threshold criterion of -12 dB from AMN. Ten eyes from 10 patients with glaucomatous defects and all of the ocular hypertensive eyes gave normal responses on the OKP screening test. The glaucomatous eyes that passed were characterized by less severe defects on the Humphrey than those who failed in terms of mean deviation (0.02 < p < 0.05) or corrected pattern standard deviation (0.01 < p < 0.02). Four of the glaucomatous eyes to pass had a nasal step as the primary field defect. None of those to fail failed only on points within 10 degrees of fixation. We suggest further modification of the OKP screening chart to improve its efficiency.

Fixation, Ocular↗

PubMed1992

Deterioration in the accuracy of the pulsair non-contact tonometer with use: need for regular calibration.

The Pulsair non-contact tonometer (Keeler Pulsair: Keeler UK) has been shown to be a versatile instrument particularly suitable for screening for raised intraocular pressure. Although demonstrated to be accurate initially when compared to the Goldmann applanation tonometer no study has examined its long-term accuracy. Comparisons of three Pulsair tonometers with different degrees of usage with the Goldmann tonometer are described. Measurements were obtained from 64, 116, and 223 eyes in three separate comparative studies. Correlation coefficients of between 0.78 and 0.90 were obtained, the least used instrument being significantly more accurate than the two more extensively used instruments. Taking the Goldmann tonometer as the standard tonometer, and the aim to detect intraocular pressures of greater than 21 mmHg, sensitivities of 40%, 48%, and 85% for the three Pulsair tonometers respectively were shown. The Pulsair tonometer appears liable to a long-term drift in accuracy with use, and we suggest that provision is made for the regular re-calibration of the instrument.

Calibration↗

PubMed1992

Blue versus white stimuli in ocular hypertension with the Friedmann Mark 1 Visual Field Analyser.

Fifty eyes of fifty patients with ocular hypertension had their visual fields tested on a Friedmann Mark 1 field analyser whilst wearing a Wratten 47B blue filter in a spectacle frame. All had normal visual fields to a white stimulus. Use of a scoring system with the blue field identified 11 patients (22%) with ocular hypertension as abnormal. The scores from this subgroup were indistinguishable from a group of subjects with early glaucomatous field loss, whilst the remaining scores were similar to normal subjects. These two subgroups of ocular hypertensive patients were similar in age and intraocular pressure. The use of a blue filter in front of the eye may offer a simple test to identify a subgroup of patients with ocular hypertension who are at increased risk of developing field loss.

Color↗

PubMed1992

Passing the DVLC field regulations following bilateral pan-retinal photocoagulation in diabetics.

Twenty-one diabetics who had had bilateral retinal panphotocoagulation preserving a visual acuity sufficient to pass the Driver and Vehicle Licensing Centre (DVLC) requirements were assessed with regard to their ability to satisfy the DVLC visual field requirements. Of the 19 patients treated with the laser alone, 17 met the requirements for a licence to drive a private vehicle. The use of the Xenon photocoagulator and large total burn area following laser was found to be associated with an increased risk of DVLC field test failure. Adequate PRP with 200 micron burns appeared to induce neovascular regression and be compatible with passing the DVLC field regulations in many patients. Panphotocoagulation of patients with early proliferative retinopathy using 200 micron burns does not appear to jeopardise a driving licence. Guidelines for laser treatment in diabetic retinopathy aimed at preserving the driving field are presented.

Automobile Driver Examination↗

PubMed1991

Intraocular pressure asymmetry in a population tested with the Pulsair non-contact tonometer.

Intraocular pressure asymmetry as measured by noncontact tonometry (NCT) was analysed in a population of 874 individuals aged over 50 years. In both males and females the intraocular pressure (IOP) measured in the right eye exceeded that of the left. Pressure asymmetry followed a normal distribution in a population subgroup known to have normal fields, discs and pressures. The 95% confidence intervals for the equation R IOP--L IOP in normals were 0.63+ or -5.46 mmHg when the mean of four pulses per eye were used to calculate the IOP, increasing to 0.80+ or -6.56 mmHg for two pulses per eye (thus expanding the limits by 20%). The range of asymmetry for NCT in normals therefore exceeds that reported for Goldmann applanation tonometry. Asymmetry was greater in females than males. Knowledge of the normal range of IOP asymmetry in each sex will help glaucoma screeners using NCT in their decision as to when to refer. A minimum of four pulses per eye should be used to assess the IOP when screening.

Aged↗

PubMed1991

Maximising the sensitivity and specificity of non-contact tonometry in glaucoma screening.

Data from a glaucoma screening study involving 88.5% of the population age 50 and over of a single handed general practitioner were reanalysed to determine the effect of altering the protocol for intraocular pressure assessment and the effect of changing the referral threshold. The predictive power of the Keeler Pulsair noncontact tonometer was found to decrease from 22.5% at four pulses per eye to 12.3% when only one pulse per eye was used, with a reduction of sensitivity from 91.7% to 75%. The sensitivity of the same device fell from 91.7% if all patients with an IOP greater than 21 mmHg were deemed as having a positive screen, to 41.6% when only patients with an IOP greater than 26 mmHg were considered for referral. To create a balance between high sensitivity and acceptable predictive power of a positive result in a population where 50% of glaucoma sufferers are known prior to screening, we advise that four pulses per eye should be used with an IOP of greater than 22 mmHg used as the significant finding indicating that the patient required referral.

Glaucoma↗

PubMed1991

Dermatomyositis responding to treatment of associated toxoplasmosis.

We report a 59-year-old woman with severe dermatomyositis in association with high serum toxoplasma antibody titres who was successfully treated with pyrimethamine and sulphadiazine. This case supports an aetiological role for toxoplasmosis in the pathogenesis of some cases of dermatomyositis.

Dermatomyositis↗

PubMed1991

Use of a blue filter in visual field analysis.

One hundred and twenty seven eyes of 127 patients were studied by means of a Kodak 47B Wratten blue gelatin filter in conjunction with the Friedmann Mark 1 visual field analyser. There were 49 patients in the normal group, 50 patients in the ocular hypertension group, and 28 patients in a group with early glaucoma. A simple scoring system did not show a useful difference between these three groups. However, use of a derived threshold value for each target group designated by the letters B to P (giving selective blue field scores) differentiated between normal subjects and those with early glaucomatous field loss. When used with a calculated upper limit of normal to give a specificity of 96%, this test had a sensitivity of 64%. Of the ocular hypertension group 22% gave abnormal results in comparison with normal persons. This simple adaptation to the Friedmann protocol may aid the ophthalmologist in the detection and confirmation of early glaucoma.

Evaluation Studies as Topic↗

PubMed1991

A camera that directly measures physical parameters.

Accurate measurement of physical parameters is essential for the practice of modern medicine and ophthalmology in particular. A measuring device is presented that combines a single lens reflex (SLR) camera body incorporating two aligned in-camera grids with a calibrated macrozoom attachment. The device has multiple applications wherever accurate measurements are required. The ability to measure and record physical parameters in both health and disease is essential to modern medical practice. This is particularly so in ophthalmology. Despite the relative accessibility of external structures, the clinician's measuring equipment often takes the form of a clear plastic ruler with the ever present possibility of inaccuracy from parallax and perspective. Indeed, even in the hands of expert observers, the results from the commercially produced Hertel exophthalmometer are prone to significant variation. Various photographic methods of measurement have been described using a fixed focal length lens system, and recently evaluated. These, however, require processing of the photographs before measurements can be taken. We present a simple, relatively inexpensive multi-purpose device which can measure physical parameters directly and record photographic evidence of these measurements. In essence, the device consists of a single lens reflex (SLR) camera fitted with two carefully aligned grids, linked to a calibrated macrozoom lens.

Anthropometry↗

PubMed1991

Levels of visual impairment in a day centre for people with a mental handicap.

A prospective study screening for visual impairment in a day centre for people with a mental handicap showed that 30% required spectacles or registration as blind or partially-sighted and a further 20% had previously unknown pathology. Carers were not reliable in identifying visual problems in their charges, and routine screening should be encouraged. High Street optometrists should be able to measure visual acuity in the individuals in this sample excluding those cared for in special care units for whom screening may be less beneficial.

Adolescent↗

PubMed1991

Screening siblings for glaucoma in the UK.

The current practice and ideals of ophthalmologists when alerting and screening siblings at risk of chronic simple glaucoma were assessed by means of a questionnaire. Seventy-nine per cent of Trent Region consultants responded, and of these, 18% do not attempt to alert siblings of glaucoma sufferers. Those who do rely on the probands to alert their siblings and the high street optometrists to screen. Under more favourable conditions, all respondents would advise screening for siblings over 40 years of age. Fifty-nine per cent would then advocate the letter as the optimum method of communication and 78% would prefer that an ophthalmologist screen this high risk group. In a pilot study of a hospital-based screening service, siblings living within a 15 mile radius of the hospital were invited by letter to attend for screening. Ninety per cent attended, of whom 12.5% required treatment and a further 11% careful observation. The cost of detecting a case of treatable disease by this strategy was estimated at 138 pounds.

Adult↗

PubMed1990

Screening for glaucoma in the community by non-ophthalmologically trained staff using semi automated equipment.

Eighty-nine and a half per cent of the population of a general practice over the age of 49 years were screened for glaucoma and high risk ocular hypertension requiring treatment. Screening took place using semi-automated intraocular pressure and visual field equipment operated by non-ophthalmologically trained staff. An experienced ophthalmologist examined all patients in a single blind manner to reduce false negatives to a minimum. Patients suspected of requiring treatment on the grounds of raised intraocular pressure, abnormal visual fields or suspicious optic discs were subsequently examined in a hospital clinic. Treatment criteria, as commonly practiced, were carefully defined and the sensitivities and specificities of the methods of screening used were calculated. One and three tenths per cent of the practice population were known to be receiving treatment prior to the study and a further 1.4% were found to require treatment after screening. The sensitivity and specificity of the non-contact tonometer were 91.7% and 95.6% respectively with a predictive power of 22.5% for a positive result. The mean time taken to perform the test in both eyes was two minutes. Seventy per cent of the patients with pressures over 22 mmHg in both eyes on screening were found to require treatment. The routine use of the field screener did not increase either the sensitivity or specificity of the screening process but its use in cases with raised intraocular pressure is advised to indicate the degree of urgency of the referral. An algorithm based on the results of the study is suggested when planning the use of semi-automated equipment to screen for ocular disease related to raised intraocular pressure.

Aged↗

PubMed1990

Corneal epithelial oxygen uptake rate in diabetes mellitus.

Corneal epithelial oxygen uptake rate (CEOUR) has been measured using a non-invasive polarographic electrode technique in patients with diabetes mellitus (DM), all with varying degrees of retinopathy. CEOUR was found to be significantly reduced in diabetic patients when compared to age-matched non-diabetic controls--Type I diabetics p less than 0.001; Type 2 diabetics p less than 0.01. Known duration of DM and assay of instantaneous, medium and long term glycaemic control showed no significant correlation with CEOUR in the patients studied. These results give further evidence of abnormal corneal metabolism in DM. Reduced CEOUR may be a contributory factor in the pathogenesis of diabetic corneal epitheliopathy.

Adult↗

PubMed1990

Costing a community based screening programme for the detection of glaucoma.

The cost of detecting a case of glaucoma in a community based screening programme was calculated using data from a pilot study on a population aged 50 and over. The cost per screen was estimated at 3.35 pounds with a total cost of 311 pounds per case detected. These estimates include the cost of both the algorithmically based screening programme and the hospital assessment of true and false positives. These costs are considered to compare favourably with the potential costs incurred by paying optometrists to screen high risk groups whilst providing the opportunity to detect over twice the number of cases of occult glaucoma.

Community Health Services↗

PubMed1990

White light interferometry in amblyopic children--a pilot study.

Interferometric acuity using the IRAS white light interferometer was compared with Snellen acuity in nine amblyopic children between the ages of five and nine years, and nine aged matched controls. All of the amblyopic eyes achieved better grating acuities than Snellen acuities. Fifty-seven per cent of the amblyopes with a best corrected Snellen acuity of 6/18 or less in their amblyopic eye, achieved grating acuities indistinguishable from normal. The hand held white light interferometer may have a role in the assessment of meridional amblyopia and in children with high astigmatic errors.

Amblyopia↗

PubMed1990

The development of cataract following trabeculectomy.

OBJECTIVE: To determine the risk of cataract development following trabeculectomy. DESIGN: A prospective follow-up study of patients seen pre-operatively and at one, three, six and 12 months following surgery and subsequently at yearly intervals. SETTING: Ophthalmology Department of Nottingham University Hospital. PATIENTS: Fifty-seven patients with primary open angle glaucoma, including pseudoexfoliation, undergoing trabeculectomy. MAIN OUTCOME MEASURES: Increases in lens opacity measured by the Lens Opacity Meter 701, the Keeler Projectoscopy and clinical grading. RESULTS: Of 35 patients seen at six months post-operatively, none had lost two Snellen lines of visual acuity due to lens opacity, although three patients showed evidence of increasing lens opacity on all three parameters. CONCLUSION: There is no evidence of visually significant lens opacity occurring at six months post-operative follow-up.

Adult↗