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Biomedical subjects

J M Sparrow

Publications and source records attributed to J M Sparrow.

At least 19 recordsLinked to original sources
PubMed2000

Quantitative comparison of static perimetric strategies in early glaucoma: test-retest variability.

PURPOSE: The aim of this study is to describe and compare test-retest variability of threshold-related suprathreshold and threshold examination strategies. METHODS: Threshold-related suprathreshold and FASTPAC threshold central visual field examinations were performed twice (test and retest) within a 4-week period on 322 subjects with early to moderate primary open-angle glaucoma and glaucoma suspects. For both strategies, defects were quantified by a count, or score, of the number of defective locations within the field as a whole and by hemifield, thereby providing a simple measure of defect extent. This quantification was obtained for the suprathreshold strategy at three suprathreshold increments (5, 8, and 12 dB) and for the full threshold strategy at two levels of pattern deviation probability, although absolute full threshold defect depth was not considered. Mean test-retest score differences and spread of score differences were used to describe variability. An index of relative variability was used to compare the two visual field examination strategies. RESULTS: Marked degrees of defect extent variability were found to exist in both suprathreshold and FASTPAC examination strategies. In general, the suprathreshold strategy exhibited lower test-retest variability of defect extent than the FASTPAC strategy. Suprathreshold test variability was dependent on the suprathreshold increment. FASTPAC examination variability was independent of defect depth when analyzed on the basis of pattern deviation probability values and was also found to be independent of the area of visual field loss. CONCLUSIONS: Suprathreshold examination techniques may provide a reliable perimetric alternative to thresholding strategies for monitoring individuals with early and moderate glaucoma, although they may not be suitable for individuals with advanced glaucomatous visual field loss.

Glaucoma, Open-Angle↗
PubMed2000

Use of vision tests in clinical decision making about cataract surgery: results of a national survey.

AIM: To provide information on the use of vision tests in clinical decision making about cataract surgery in the UK. METHOD: A questionnaire survey was mailed to 703 consultant ophthalmologists. RESULTS: A response rate of 70% was obtained. Monocular distance visual acuity was the only visual function that was tested routinely by all surgeons. Supplementary use of contrast sensitivity and glare testing was low. Many surgeons (35%) were willing to consider surgery at acuity levels better than 6/9 and a small but substantial number (12%) indicated that they did not use an acuity criterion. Being prepared to consider surgery at relatively good levels of acuity was not associated with more common use of other tests of vision. CONCLUSION: Many UK surgeons are prepared to consider cataract extraction at relatively good levels of visual acuity and use other vision tests infrequently.

Aged↗
PubMed2000

The Bristol shared care glaucoma study: outcome at follow up at 2 years.

AIM: To examine the outcome of care for patients with glaucoma followed up by the hospital eye service compared with those followed up by community optometrists. METHODS: A randomised study with patients allocated to follow up by the hospital eye service or community optometrists was carried out in the former county of Avon in south west England. 403 patients with established or suspected primary open angle glaucoma attending Bristol Eye Hospital and meeting defined inclusion and exclusion criteria were studied. The mean number of missed points on visual field testing in the better eye (using a "better/worse" eye analysis) in each group were measured. The visual field was measured using the Henson semiautomated central field analyser (CFA 3000). Measurements were made by the research team on all patients at baseline before randomisation and again 2 years after randomisation. The mean number of missed points on visual field testing in the worse eye, mean intraocular pressure (mm Hg), and cup disc ratio using a "better/worse" eye analysis in each group at 2 years were also measured. Measurements were made by the research team on all patients at baseline before randomisation and again 2 years after randomisation. An analysis of covariance comparing method of follow up taking into account baseline measurements of outcome variables was carried out. Additional control was considered for age, sex, diagnostic group (glaucoma suspect/established primary open angle glaucoma), and treatment (any/none). RESULTS: From examination of patient notes, 2780 patients with established or suspected glaucoma were identified. Of these, 752 (27.1%) fulfilled the entry criteria. For hospital and community follow up group respectively, mean number of missed points on visual field testing at 2 year follow up for better eye was 7.9 points and 6.8 points; for the worse eye 20.2 points and 18.4 points. Similarly, intraocular pressure was 19.3 mm Hg and 19.3 mm Hg (better eye), and 19.1 mm Hg and 19.0 mm Hg (worse eye); cup disc ratio at 2 year follow up was 0.72 and 0.72 (better eye), and 0.74 and 0.74 for hospital and community follow up group respectively. No significant differences in any of the key visual variables were found between the two groups before or after adjusting for baseline values and age, sex, treatment, and type of glaucoma. CONCLUSIONS: It is feasible to set and run shared care schemes for a proportion of patients with suspected and established glaucoma using community optometrists. After 2 years (a relatively short time in the life of a patient with glaucoma), there were no marked or statistically significant differences in outcome between patients followed up in the hospital eye service or by community optometrists. Decisions to implement such schemes need to be based on careful consideration of the costs of such schemes and local circumstances, including geographical access and the current organisation of glaucoma care within the hospital eye service.

Age Distribution↗
PubMed2000

Screening for refractive errors with the Topcon PR2000 Pediatric Refractometer.

PURPOSE: The PR2000 (Topcon, Tokyo, Japan) is a photorefractor that has been used in a population study comparing different methods of screening preschool children. The present study was conducted to determine the accuracy of the device in a largely clinical population. METHODS: Two hundred twenty-two children less than 8 years of age were included. All children were examined by an orthoptist using the PR2000 without inducing cycloplegia. All children then underwent retinoscopy with cycloplegia by an examiner who was unaware of the results from the PR2000 examination. RESULTS: The PR2000 gave a numerical reading for 90% of the children's right eyes and the message "Out of range" for a further 5%. The readings underestimated the amount of hypermetropic or astigmatic refractive error found on retinoscopy by an amount proportional to the magnitude of the refractive error. Agreement with retinoscopy for the axis of astigmatism more than 0.75 D was moderately good (intraclass correlation coefficient [ICC] = 0.63). The PR2000 was more useful as a screener, especially for anisometropia for which it was 91% sensitive and 92% specific. The repeatability was good for sphere (ICC = 0.74), less so for astigmatism (ICC = 0.59), and better than the optometrist for anisometropia (ICC = 0.38). The presence of nonrefractive diagnoses and the age of the children examined made little difference in the screening results. CONCLUSIONS: The PR2000 underestimated hypermetropic refractive errors when used without cycloplegia. However, it was at least as good a screening device as other similar instruments, especially when judged by its ability to detect anisometropia and the repeatability of the results.

Child↗
PubMed1999

The National Diabetic Retinopathy Laser Treatment Audit. III. Clinical outcomes.

PURPOSE: To describe the short-term clinical outcomes for a cohort of patients undergoing first photocoagulation treatment for proliferative retinopathy or maculopathy in the United Kingdom. METHOD: Nine-month follow-up of the Royal College of Ophthalmologists' national audit of laser treatment for diabetic retinopathy. RESULTS: For eyes with maculopathy, 9.2% had had a deterioration in visual acuity equivalent to a doubling of the visual angle and 3.3% of eyes had a visual acuity of less than 6/60 at follow-up. There had been an improvement in the macular oedema or exudate in 64.6% and 77.3% respectively. Prognostic factors for a poorer visual acuity at follow-up were worse visual acuity at baseline, the presence of diffuse (vs focal) oedema and grid (vs focal) treatment. For eyes with proliferative retinopathy, the retinal neovascularisation had regressed fully in 50.8% of cases, whilst there had been no change or a deterioration in 10.3%. A visual acuity of less than 6/60 at follow-up was present in 8.6% of eyes. There was a poor morphological outcome at follow-up (as defined by rubeosis, new tractional detachment or having had a vitrectomy) in 7.2%. Risk factors for poor morphological outcome were the presence of 'high-risk characteristics', female sex and the presence of concurrent maculopathy at baseline. Regression of neovascularisation was associated with greater areas of retinal ablation at the initial treatment session. Although some eyes with proliferative retinopathy appeared to be undertreated initially compared with DRS and ETDRS protocols, some of these eyes did respond to lower amounts of treatment. CONCLUSION: For maculopathy, poorer outcome was related to worse visual acuity at baseline, diffuse (vs focal) maculopathy, and grid treatment. For proliferative retinopathy, poorer outcome was related to 'high-risk characteristics' and coexistence of maculopathy at baseline, and improvement was related to larger areas of ablation. The relationship of poor outcome with worse initial disease argues for earlier detection of retinopathy.

Diabetic Retinopathy↗
PubMed1999

Proposed classification for topographic patterns seen after penetrating keratoplasty.

AIMS: To create a clinically useful classification for post-keratoplasty corneas based on corneal topography. METHODS: A total of 360 topographic maps obtained with the TMS-1, from 95 eyes that had undergone penetrating keratoplasty (PKP), were reviewed independently by two examiners in a masked fashion, and were categorised according to a proposed classification scheme. RESULTS: A high interobserver agreement (88% in the first categorisation) was achieved. At 12 months post-PKP, a regular astigmatic pattern was observed in 20/85 cases (24%). This was subclassified as oval in three cases (4%), oblate symmetric bow tie in six cases (7%), prolate asymmetric bow tie in six cases (7%), and oblate asymmetric bow tie in five cases (6%). An irregular astigmatic pattern was observed in 61/85 cases (72%), subclassified as prolate irregular in five cases (6%), oblate irregular in four cases (5%), mixed in seven cases (8%), steep/flat in 11 cases (13%), localised steepness in 16 cases (19%), and triple pattern in three cases (4%). Regular astigmatic patterns were associated with significantly higher astigmatism measurements. The surface asymmetry index was significantly lower in the regular astigmatic patterns. CONCLUSIONS: In post-PKP corneas, the prevalence of irregular astigmatism is about double that of regular astigmatism, with a trend for increase of the irregular patterns over time.

Astigmatism↗
PubMed1999

The Bristol Shared Care Glaucoma Study: reliability of community optometric and hospital eye service test measures.

BACKGROUND/AIMS: Primary open angle glaucoma patients and glaucoma suspects make up a considerable proportion of outpatient ophthalmological attendances and require lifelong review. Community optometrists can be suitably trained for assessment of glaucoma. This randomised controlled trial aims to assess the ability of community optometrists in the monitoring of this group of patients. METHODS: Measures of cup to disc ratio, visual field score, and intraocular pressure were taken by community optometrists, the hospital eye service and a research clinic reference "gold" standard in 405 stable glaucoma patients and ocular hypertensives. Agreement between and within the three centres was assessed using mean differences and intraclass correlation coefficients. Tolerance limits for a change in status at the level of individual pairs of measurements were also calculated. RESULTS: Compared with a research clinic reference standard, measurements made by community optometrists and those made in the routine hospital eye service were similar. Mean measurement differences and variability were similar across all three groups compared for each of the test variables (IOP, cup to disc ratio, and visual field). Overall, the visual field was found to be the most reliable measurement and the cup to disc ratio the least. CONCLUSIONS: Trained community optometrists are able to make reliable measurements of the factors important in the assessment of glaucoma patients and glaucoma suspects. This clinical ability should allow those optometrists with appropriate training to play a role in the monitoring of suitable patients.

Community Health Services↗
PubMed1998

Randomised trial of effectiveness of second eye cataract surgery.

BACKGROUND: The effectiveness of cataract surgery on one eye is well established, but concerns over health-care expenditure have called into question the value of cataract surgery on the second eye. We examined the effects of second eye surgery in terms of patient perceptions as well as through visual acuity, contrast sensitivity, and stereoacuity tests. METHODS: 208 otherwise healthy patients awaiting second eye cataract surgery were recruited into our randomised trial. At randomisation participants were allocated expedited surgery (planned to take place within 6 weeks) or routine surgery (routine waiting time, 7-12 months). Assessments were made at randomisation and again at review after about 6 months. Eight primary trial outcomes consisted of four questionnaire items and four visual function tests, done with both eyes open. FINDINGS: Traditional clinical tests of success in cataract surgery (visual acuity and contrast sensitivity) showed only slight differences in binocular vision in favour of the expedited-surgery group. There were major benefits for the expedited-surgery group in terms of reported visual symptoms and effects on quality of life. At review, differences in self-reported vision related difficulties between the two groups ranged from 11% (95% CI 4.4-17%, activities) to 30% (19-41%, reading). Stereoacuity was better in the expedited surgery group, the difference between the groups for the proportions with stereoacuity of 3000 s of arc or worse was 58% (47-69%). INTERPRETATION: This trial has shown that there is a clear benefit from second eye cataract surgery.

Adult↗
PubMed1998

The National Diabetic Retinopathy Laser Treatment Audit. I. Maculopathy.

The National Diabetic Retinopathy Laser Treatment Audit is a prospective survey of laser treatment for diabetic retinopathy throughout the United Kingdom. This paper describes the methodology of the study and presents data on 546 patients who were undergoing their first photocoagulation treatment for diabetic maculopathy (without proliferative retinopathy) during a 2 month period in 1995. Validation of the level of participation, patient demographic features, sources of referral, the level of systematic screening and waiting times are described. Maculopathy was detected as a result of systematic screening in 65.2%, whilst 12.3% of cases presented symptomatically. The percentage of cases treated within 8 weeks of listing was 83.1%, whilst 7% waited for more than 12 weeks for their laser treatment. The retinopathy features and the type of treatment given are also described. The maculopathy was said to be predominantly exudative in nature in 69.8% of cases, and 96.2% of these eyes were treated with focal macular laser. The maculopathy was said to be diffusely oedematous in nature in 8.6% of cases, and 78.7% of these eyes were treated with grid macular laser.

Adult↗
PubMed1998

The National Diabetic Retinopathy Laser Treatment Audit. II. Proliferative retinopathy.

The National Diabetic Retinopathy Laser Treatment Audit is a prospective survey of laser treatment for diabetic retinopathy throughout the United Kingdom. This paper presents data on 284 patients who were undergoing their first panretinal photocoagulation for proliferative retinopathy during a 2 month period in 1995, describing the demographic features, the level of systematic screening, the sources of referral, and the waiting times. For those cases where proliferative retinopathy was present at the first ophthalmology outpatient visit, the retinopathy was detected as a result of systematic screening in 46.8%, whilst 28.7% presented symptomatically. Of these patients 28.4% waited for more than 12 weeks from referral to the time of laser treatment, but once the patient had been listed for laser treatment this was performed within 8 weeks in 95.3%. The retinopathy features and the type of treatment given are also described. Compared with the DRS and ETDRS recommendations, at least 32.5-40.2% of eyes may be undertreated initially, and for those with high-risk characteristics these figures were at least 30.8-38.5%.

Adolescent↗
PubMed1998

Development of a questionnaire for measurement of vision-related quality of life.

PURPOSE: To define vision-related quality of life, to outline the development of a vision-specific quality of life instrument and to present the characteristics of a 10-item 'core' questionnaire. METHOD: A standard method included: 1. Generation of relevant issues by individual interviews with 38 visually impaired adults, consultation with 37 professionals and support workers and literature review. 2. Operationalisation, involving 58 ophthalmic patients. 3. Pre-testing, to maximise face validity and content validity, involving 184 individuals with a variety of different visual problems and social backgrounds. 4. Adoption of a modular approach to item selection. 5. Formal piloting in 92 individuals to establish reliability and construct validity. RESULTS: More than 232 items were tested of which 139 were considered suitable for a final question pool or 'parent' questionnaire (the VQOL). From this parent questionnaire individual items or groups of items can be selected. Ten broadly applicable items referring to physical, social and psychological issues were selected for the core questionnaire (the VCM1). The VCM1 has high reliability (alpha = 0.93) and validity. CONCLUSIONS: Any self-reported problem relating to vision may constitute a quality of life issue. A modular approach to item selection may provide the flexibility to investigate vision-related quality of life in a wide range of clinical settings, allowing detailed assessment of specific problems and also cross-study comparisons where appropriate.

Adult↗
PubMed1998

Clinical evaluation of scanning laser polarimetry: I. Intraoperator reproducibility and design of a blood vessel removal algorithm.

AIMS: To evaluate the reproducibility of the retardation values (change in polarisation) obtained with the scanning-laser polarimeter in a series of normal subjects and glaucoma patients. To improve the analysis of the raw data by devising and evaluating a blood vessel removal algorithm. METHODS: Scanning laser polarimetry was performed on 10 normal subjects and 10 glaucoma patients. A series of six images was obtained from each eye. The normal subjects were re-imaged 3 months after their initial assessment. The retardation values obtained from each eye were analysed using the authors' own methods, including the use of an algorithm to remove blood vessels from the polar profiles. The reproducibility of these measurements and the performance of the blood vessel removal algorithm were assessed. RESULTS: The "individual point" coefficient of variation was approximately 12.5% for normal subjects and 17.0% for glaucoma patients. The "integral" coefficient of variation for these groups was approximately 5.5% and 9.5% respectively. The reproducibility of the measurements did not improve with an increased number of measurements. There was no difference in the reproducibility of the measurements in normal subjects over time. The blood vessel removal algorithm improved the reproducibility of the measurements when the shape of the profile was assessed. CONCLUSION: The intraoperator reproducibility of retardation values obtained with the scanning laser polarimeter is satisfactory for its use as a clinical tool. The use of a blood vessel removal algorithm improves the reproducibility of the measurements and also assists the clinician in the interpretation of the polar profiles. Furthermore, it allows the construction of normal database polar profiles, thereby enabling the identification, location and quantification of retinal nerve fibre layer damage in an "at risk" individual's polar profile.

Algorithms↗
PubMed1998

Clinical evaluation of scanning laser polarimetry: II. Polar profile shape analysis.

AIMS: To devise a method to describe and quantify the shape of polar profiles obtained with the scanning laser polarimeter and to compare this measurement with other polar profile measurements in a series of normal subjects and glaucoma patients. METHODS: Scanning laser polarimetry was performed on 54 normal subjects and 74 glaucoma patients. The retardation values obtained from one randomly chosen eye of each subject were analysed using our own methods, including the use of an algorithm to remove blood vessels from the polar profiles, an algorithm to standardise the glaucoma profiles to a normal database, and a further algorithm to evaluate the profile shape. The measurements of profile shape were compared with measurements of the absolute and standardised retinal nerve fibre layer thickness obtained with the scanning laser polarimeter. RESULTS: There was no significant difference between the mean retardation values for the normal and glaucomatous subjects in either hemiretina. However, standardisation of the glaucoma retardation values to a normal database produced significant differences at p < 1 x 10-8 in the mean retardation values for these two groups in both hemiretinas. Profile shape measurement analysis produced similar significant differences between the mean retardation values for the normal and glaucomatous subjects in both hemiretinas, although the degree of separation was greater following standardisation of the retardation values. CONCLUSION: The use of an algorithm to standardise an individual's retardation values in conjunction with a blood vessel removal algorithm enables an improvement in the ability of the scanning laser polarimeter to discriminate between normal and glaucomatous patients. The polar profile shape algorithm is independent of standardisation and significantly improves the discrimination between normal and glaucomatous patients, as well as providing additional information regarding the retinal nerve fibre layer.

Adult↗
PubMed1998

Clinical evaluation of keratometry and computerised videokeratography: intraobserver and interobserver variability on normal and astigmatic corneas.

AIMS: To evaluate intra- and interobserver variability in measurements on normal and astigmatic corneas with keratometry and computerized videokeratography. METHODS: Keratometric readings with the 10 SL/O Zeiss keratometer and topographic maps with the TMS-1 were obtained by two independent examiners on 32 normal and 33 postkeratoplasty corneas. Inter- and intraobserver coefficients of variability (COR) for measurements of steep and flat meridian power and location, in addition to the magnitude of astigmatism, were assessed. RESULTS: Compared with TMS-1, the 10 SL/O keratometer showed a superior repeatability in measuring normal corneas (intraobserver COR for keratometry and TMS-1 respectively: 0.22 and 0.30 D for steep meridian power; 0.18 and 0.44 D for flat meridian power; 0.26 and 0.40 D for astigmatism; 5 degrees and 26 degrees for steep meridian location; 5 degrees and 13 degrees for flat meridian location). Astigmatism intraobserver COR (0.20 D and 0.26 D for the two observers) and interobserver COR (0.28 D) of the keratometer for normal corneas was very good and not affected by observers' experience. Repeatability of the TMS-1 on normal corneas was found to be: (a) observer related, and (b) astigmatism related. A novice observer showed a much greater COR (1.62 D for astigmatism, 30 degrees for flat meridian location) compared with the experienced examiner (0.40 D for astigmatism, 13 degrees for flat meridian location). Higher deviation scores were observed for corneas with higher astigmatism. For the postkeratoplasty corneas, again the keratometer achieved superior reproducibility (astigmatism interobserver COR 1.12 D for keratometry, 4.06 D for TMS-1; steep meridian location interobserver COR 10 degrees for keratometry, 34 degrees for TMS-1). CONCLUSION: Keratometric readings are more reproducible than topographic data both for normal and postkeratoplasty corneas. The two instruments should not be used interchangeably especially on highly astigmatic corneas. For the TMS-1, users with the same level of experience should be employed in clinical or experimental studies.

Adult↗
PubMed1998

Variability in glaucomatous visual fields: implications for shared care schemes.

The purpose of this study was to establish the extent of variability in the visual fields of patients with glaucoma using a suprathreshold perimetric test strategy. The visual fields of 104 patients (126 eyes) were measured twice, on separate days, with a Henson CFA3000 central visual field analyser. All eyes had a diagnosis of glaucoma and had a minimum of three stimuli missed at 12 dB above their threshold estimate derived at the beginning of the first suprathreshold examination. The perimeter tested 132 locations within the central 25 degrees with a multiple stimulus suprathreshold strategy. Data were analysed on the basis of the difference in the number of recorded missed stimuli between the two visits. Large amounts of variability were found in the visual field results. Variability was largest when all levels of defect were included (> = 5 dB) and was found to be independent of the overall extent of loss. Results from the superior hemifield were found to be more variable than those from the inferior hemifield. The results highlight the problem of differentiating real change in visual field status from the enhanced variability seen in patients with glaucomatous visual field loss. The results from this study can be used to establish return-referral criteria for shared care schemes. The advantages of duplicate measures of the visual field are highlighted.

Glaucoma↗