Biomedical subjects

E C O'Neill

Publications and source records attributed to E C O'Neill.

At least 19 recordsLinked to original sources

PubMed1999

The SITA perimetric threshold algorithms in glaucoma.

PURPOSE: To determine the within-visit between-algorithm and the within-algorithm between-visit differences in sensitivity for the SITA Standard, SITA Fast, FASTPAC, and Full Threshold algorithms in stable primary open angle glaucoma. METHODS: One designated eye from each of 29 patients (age 67.3 +/- 10.2 years; mean +/- SD) experienced in automated perimetry was examined with the four algorithms on each of three visits, using the Humphrey Field Analyzer 750 and Program 30-2. RESULTS: The group mean Mean Sensitivity was 1.0 dB greater for SITA Standard than Full Threshold (P < 0.001), 0.7 dB greater for SITA Standard than FASTPAC (P < 0.001), 1.6 dB greater for SITA Fast than FASTPAC (P < 0.001), and 0.9 dB greater for SITA Fast than SITA Standard (P < 0.001). The higher pointwise sensitivity for SITA Fast compared to Full Threshold, FASTPAC, and SITA Standard increased with increase in defect depth. The examination duration for SITA Standard was 53% of that for Full Threshold and 50% shorter for SITA Fast compared to FASTPAC (P < 0.001), regardless of age (P = 0.932). The examination duration increased with increase in severity of field loss (P < 0.001), and this increase was proportionately greater for both SITA algorithms (P < 0.001), particularly SITA Fast. The Total and Pattern Deviation probability analyses of both SITA algorithms yielded a statistically greater defect than Full Threshold or FASTPAC (P < 0.001). The within-algorithm between-visit differences were similar between SITA Standard and Full Threshold and between SITA Fast and FASTPAC. CONCLUSIONS: Both SITA algorithms produce a marginally higher differential light sensitivity compared to existing algorithms but with a statistically deeper defect and a marked reduction in examination duration.

Adult↗

PubMed1998

Evaluation of optic disc cupping using high-resolution ocular ultrasound.

BACKGROUND/PURPOSE: The new Biovision B-Scan Probe has greater resolution than its predecessors because of its posteriorly placed focus (25 mm inside the eye) and the consequent reduction in size of the sound field. We investigated the accuracy, reproducibility and test-retest variability of two-dimensional optic cup measurements using this new-generation B-scanner. METHODS: One randomly selected eye of 20 patients underwent five repeated measurements of vertical (VOCD) and horizontal optic cup diameters (HOCD), and optic cup depth, using confocal scanning laser tomography (Heidelberg Retinal Tomograph) and high-resolution ultrasound (Biovision, Chiron Vision, UK) on two separate occasions. There was one operator per instrument who was masked to all clinical data and previous measurements. Accuracy of ultrasound readings was quantified by comparing the results with those of Heidelberg Retinal Tomography (HRT). RESULTS: The 95% confidence interval for the bias of echographic vertical and horizontal cup diameter measurements was -95 +/- 48 microns and -19 +/- 72 microns respectively, and -87 +/- 328 microns for cup depth readings. The indices of reproducibility (mean coefficient of repeatability +/- SD) were: VOCD: 177 +/- 105 microns [B-scan] 209 +/- 100 microns [HRT]; HOCD: 179 +/- 61 microns [B-scan], 205 +/- 101 microns [HRT]; cup depth: 206 +/- 63 microns [B-scan], 204 +/- 124 microns [HRT]. Ninety-five per cent limits of agreements between initial and retest values for ultrasound were 18 +/- 136 microns [VOCD], 2 +/- 144 microns [HOCD] and 4 +/- 156 microns [cup depth], compared with 1 +/- 104 microns [VOCD], 20 +/- 102 microns [HOCD] and 3 +/- 168 microns [cup depth] for scanning laser tomography. CONCLUSION: The results demonstrate that measurements of optic cup diameter and depth using ultrasound correlate strongly with corresponding HRT readings. These echographic measurements are reproducible, and not subject to clinically meaningful test-retest variability. This technique of measuring two-dimensional cup parameters does not require expensive specialist equipment and has many potential clinical applications which are discussed.

Aged↗

PubMed1998

Correlation between the orbital and intraocular portions of the optic nerve in glaucomatous and ocular hypertensive eyes.

BACKGROUND/PURPOSE: It has recently been reported that the retrobulbar optic nerve diameter (OND) and cross-sectional area (ONCSA) are reduced in glaucoma. This study was performed to investigate the correlation between the orbital and intraocular portions of the optic nerve. METHODS: One eye of 20 volunteers (16 glaucoma subjects, 4 ocular hypertension subjects) underwent optic disc analysis using Heidelberg retinal tomography, and echographic measurements of the retrobulbar optic nerve. RESULTS: The male-to-female ratio was 6.5:3.5, and the mean age of our sample (+/- SD) was 62.25 +/- 13.7 years. Orbital optic nerve diameter and cross-sectional area correlated significantly and positively with the neuroretinal rim area (Spearman's rank correlation coefficient; OND: rs = 0.488, p = 0.0336; ONCSA: rs = 0.619, p = 0.0079), but not with any other topographical disc data. The retrobulbar optic nerve cross-sectional area-to-disc area ratio (ONCSA/D) was found to have a significant negative correlation with the cup area/disc area ratio (simple regression analysis; r = -3.948, p = 0.046), and a statistically demonstrable positive correlation with the neuroretinal rim area/disc area ratio (r = 0.451, p = 0.046). CONCLUSION: The results of this study indicate that orbital optic nerve dimensions are a reflection of the neuroretinal rim area of the optic disc. Echographic measurements of the retrobulbar nerve may be additive to the traditional triad of raised intraocular pressure, field defects and glaucomatous optic neuropathy that suggests a diagnosis of glaucoma.

Adult↗

PubMed1998

Echographic measurements of the retrobulbar optic nerve in normal and glaucomatous eyes.

AIM: A study was designed to investigate whether measurements of the optic nerve diameter (OND) and cross sectional area (ONCSA), as measured by B-scan ultrasonography, are altered in glaucoma. The reproducibility and test-retest variability of echographic estimates of retrobulbar optic nerve dimensions was also tested. METHODS: One eye of 49 glaucoma patients and 90 control subjects underwent five repeated echographic measurements of the maximal interpial diameter and cross sectional area of the orbital optic nerve on two separate occasions. All measurements were taken by one experienced ultrasonographer. RESULTS: Mean optic nerve diameter (SD) for the control group was 2.86 (0.46) mm, and was independent of height (multiple regression analysis: p = 0.21), axial length (p = 0.74), spherical equivalent (p = 0.97), sex (ANOVA: p = 0.36), or race (p = 0.14), but was inversely related to age (p = 0.01). Reproducibility of OND readings in control subjects was 0.149 mm (coefficient of repeatability). Test-retest variability of interpial diameter was -0.02 (0.29) mm. Mean interpial diameter of the optic nerve was significantly smaller among glaucomatous eyes (2.58 (0.501) mm) than controls (Mann-Whitney U test: p < 0.0001). Glaucomatous optic nerves also had a significantly smaller cross sectional area (6.68 (2.58) mm2) than those of healthy volunteers (8.25 (1.67) mm2) (p = 0.004). CONCLUSION: Echographic measurements of the orbital optic nerve are highly reproducible and not subject to clinically meaningful test-retest variability. Optic nerve interpial diameter and cross sectional area are reduced in glaucomatous eyes, reflecting nerve fibre loss. This technique may be useful in distinguishing between normal and glaucomatous eyes where optic disc morphometry is inconclusive or impossible as a result of opaque media.

Aged↗

PubMed1998

Trabeculectomy augmented with mitomycin C application under the scleral flap.

AIM: The authors investigated the safety and intraocular pressure (IOP) lowering effectiveness of trabeculectomy augmented with mitomycin C application beneath the scleral flap, and assessed the influence of preoperative risk factors on the surgical outcome. METHODS: A retrospective study of 72 consecutive high risk eyes undergoing trabeculectomy with adjunctive mitomycin C (0.2 mg/ml) applied under the scleral flap for 5 minutes was performed. Each eye was ascribed a score based on the number of preoperative risk factors, and categorised into one of three risk factor groups. Success was described as unqualified where IOP was < or = 21 mm Hg without medication and qualified where antiglaucomatous therapy was required to maintain it at such a level. A life table analysis of IOP control was calculated. RESULTS: The mean IOP (SD) fell from a preoperative level of 28.4 (6.9) to a level of 16.63 (8.06) mm Hg at the last follow up (paired Student's t test: p < 0.0001). Fifty two eyes (72%) were classed as unqualified successes. The survival rates did not differ significantly between different risk factor groups (log rank test: chi 2 = 0.967, p > 0.1). The incidence of postoperative complications compared favourably with reports of mitomycin C application between Tenon's capsule and the undissected scleral bed. CONCLUSION: The results illustrate that mitomycin C applied beneath the scleral flap during trabeculectomy in high risk eyes is associated with a success rate comparable to other modes of application. The incidence of potentially serious complications such as conjunctival wound leak and prolonged hypotony was lower than previously published data reporting sub-Tenon's administration of mitomycin C. The number and nature of preoperative risk factors do not appear to influence the surgical outcome. A possible mechanism of action is proposed.

Adult↗

PubMed1997

Primary open angle glaucoma and hypothyroidism: chance or true association?

The prevalence of hypothyroidism in British patients with primary open angle glaucoma (POAG) was examined. A recently reported study from Montreal had shown a significant increase (p < 0.004) in biochemical hypothyroidism (23.4%) in a population of 64 POAG patients compared with controls (4.7%). Mechanisms for a possible causal association between the two diseases are discussed, including mucopolysaccharide deposition in the trabecular meshwork and vasculopathy altering ocular bloodflow. Reports of improved glaucoma control following treatment of hypothyroidism are discussed. This study examined 100 consecutive patients with POAG in a specialist glaucoma clinic. All patients were questioned regarding symptoms of thyroid dysfunction and previous thyroid disease. All patients not already taking thyroxine underwent an assay of thyroid stimulating hormone. The 4% (95% CI 1.1-9.4%) prevalence of overt hypothyroidism in our study shows no clinically significant increase either over controls in the Montreal study or over our local population. We conclude that in our local population there is no evidence for a clinically important association of hypothyroidism with glaucoma.

Aged↗

PubMed1996

Day-case trabeculectomies: safety and efficacy.

A comparison of 90 day-case and 102 in-patient trabeculectomies is presented. There was no statistically significant difference in the incidence of post-operative hyphaema (Chi-squared test p = 0.84), shallow anterior chamber (p = 0.46), flat bleb (p = 0.84) or hypotony (p = 0.87) between the two groups. Casualty attendances, readmissions and further surgery in the postoperative period were seen with similar frequency in each group. Intraocular pressure control three months following surgery was not compromised by undergoing the procedure as a day-case (p = 0.29). This study demonstrates the safety and efficacy of ambulatory filtration surgery.

Adult↗

PubMed1995

The statistical interpretation of blue-on-yellow visual field loss.

PURPOSE: To evaluate short-wavelength-sensitive perimetry in the detection of glaucomatous field loss. METHODS: The sample consisted of 27 normal subjects, 24 patients with primary open angle glaucoma (POAG), and 27 patients with ocular hypertension (OHT). Blue-on-yellow (B-Y) and standard (W-W) perimetry was undertaken with a modified Humphrey Field Analyzer 640 on one eye of each subject and patient. The B-Y data were corrected for individual ocular media absorption. Results were compared to an age-matched normal database of 50 subjects (age range, 60 to 82 years; mean age, 70.0 years; SD, 6.4 years). Visual field indices and total and pattern deviation probability maps were calculated for both W-W and B-Y fields. RESULTS: The B-Y normal database exhibited increased between-subject variability compared to the W-W normal database (P < 0.001). The greater variability increased with the increase in eccentricity (P < 0.001) and with the increase in age (P = 0.032). All patients with POAG exhibited B-Y field loss; 11 demonstrated greater B-Y loss than the corresponding W-W field. In advanced POAG, the B-Y and the W-W fields were similar. Twenty-five of the 27 normal subjects exhibited normal B-Y fields. Five of the 27 patients with OHT manifested B-Y focal abnormality and a normal W-W field: in two, W-W focal loss subsequently developed. CONCLUSIONS: Short-wavelength-sensitive perimetry can identify visual field loss before that detected by W-W perimetry. However, the increased between-subject variability necessitates stringent statistical analysis in the definition of abnormality.

Aged↗

PubMed1994

The predictive value of post-operative intraocular pressures following trabeculectomy.

The value of post-operative intraocular pressure (IOP) in predicting the outcome of trabeculectomy was investigated in a retrospective study of single eyes of 203 Caucasian patients with uncomplicated chronic open angle glaucoma from the Birmingham and Midland Eye Hospital. Post-operative IOPs were recorded on day 1, at 2 weeks, and at 3, 6, 12 and 24 months. Surgical failure, defined as an IOP of 21 mmHg or above throughout the study period, occurred in 66 eyes by 24 months (32.5% failure). Discriminant analysis for the first day post-operative IOP showed a reliability of prediction of success (RPS) and failure (RPF) of 76.4% and 74.4% respectively, with an accuracy of prediction of success (APS) and failure (APF) of 92.6% and 42.6%. At 2 weeks, APS remained high (90.3%) and APF increased with time (63.2%). Certainty of success prediction at any stage is high and certainty of failure prediction becomes greater with time. In terms of IOP on the first post-operative day, 92.6% of successes may be correctly predicted if the IOP < 17 mmHg and 42.6% of failures may be predicted if the IOP > or = 17 mmHg. This study suggests that identification of patients at risk of failure on the basis of IOP in the early post-operative period is possible and that closer follow-up and early medical or surgical intervention may be indicated.

Adult↗

PubMed1994

Fatigue effects during a single session of automated static threshold perimetry.

PURPOSE: To determine using a routine clinical program the time course of the fatigue effect in both eyes at a given examination, the influence of rest periods during the examination, and the differences in the fatigue effect between persons with ocular hypertension and age-matched normal subjects. METHODS: Perimetry was undertaken for both eyes of 20 normal persons and 20 persons with ocular hypertension using Program G1X (Interzeag AG, Schlieren, Switzerland) of the Octopus 1-2-3 perimeter. Global mean defect and loss variance were calculated for each of the eight individual stages and global SF was calculated for stages 5 to 8. The superoinferior and nasotemporal hemifield indices and those for within and beyond 17 degrees eccentricity were calculated separately to investigate the locus of the fatigue effect. RESULTS: Group mean mean defect and loss variance deteriorated over stages (P < 0.001) and between eyes for both groups (P < 0.001; P < 0.004). The deterioration in the mean defect was more marked peripherally (P < 0.001) and inferiorly with age and group (P < 0.001) whereas the localized loss was more pronounced peripherally (P < 0.001), superiorly (P < 0.010) and nasally (P < 0.001). A 1-minute break during the examination of a given eye and a 3-minute break between eyes was insufficient to overcome the fatigue effect. The performance of the two groups was almost indistinguishable. CONCLUSIONS: The deterioration in the visual field indices mean defect and loss variance challenges the currently accepted ideal length of a perimetric examination with the conventional algorithms. Confidence limits for the definition of abnormality with these algorithms should reflect the presence of the fatigue effect and be different for the second eye.

Aged↗

PubMed1993

The influence of stimulus parameters on the visual field indices by automated projection perimetry.

The various stimulus parameters offered by two standard automated projection perimeters [Humphrey Field Analyser 630 (HFA) and Octopus 201], namely, stimulus size and location and the interaction of adaptation level and stimulus duration, were compared in a sample of 20 patients attending a glaucoma clinic using the visual field indices mean defect (MD), loss variance (LV), short-term fluctuation (SF) and corrected loss variance (CLV). LV and SF were greater with Octopus program 32 compared with Octopus program G1 (P < 0.02). No difference in the indices was found between stimulus sizes I and III for HFA program 30-2. MD was greater for program 30-2 compared with program 32 (P < 0.002) when expressed in terms of log (L/delta L) whereas LV (P < 0.02) and SF (P < 0.02) were greater for program 32. All differences were considered to be negligible in the clinical sense.

Adaptation, Ocular↗

PubMed1993

Evaluation of FASTPAC: a new strategy for threshold estimation with the Humphrey Field Analyser.

A new strategy for threshold estimation, FASTPAC, has been introduced for the Humphrey Field Analyser with the aim of improving the efficiency of visual field examination without loss of accuracy. FASTPAC was compared to the standard 4-2 double staircase strategy in 98 normal volunteers (age 23-83 years). One eye of each subject was examined with both strategies on two visits using Program 30-2. The order of strategy was randomised. FASTPAC examination time was 43% faster than the standard algorithm, but the mean sensitivities were similar. Short-term fluctuation was 24% higher with FASTPAC (P < 0.001). Most parameters were adversely affected by increasing age. FASTPAC offers a valid alternative to the standard strategy in the examination of suspected normal fields and should always be considered as an alternative to the threshold-related screening strategies. The performance of the algorithm in the identification of field loss and in areas of reduced sensitivity awaits further study.

Adult↗

PubMed1991

Time-related variation in normal automated static perimetry.

The effects of phase of eye test and order of eye examined were investigated in 38 normal subjects using a customized 30-point central threshold program of the Humphrey Field Analyzer 640. This program, designed to be completed within 5 minutes, was successively repeated three times for each eye (i.e., three phases for each eye) at two visits separated by an interval of approximately 2 weeks. Both global and pointwise group mean sensitivity decreased in a time-related manner, deterioration being greater for the second eye at each visit, for both 200 ms and 100 ms stimulus durations.

Adult↗

PubMed1991

Long-term follow-up of baseline learning and fatigue effects in the automated perimetry of glaucoma and ocular hypertensive patients.

The detection of change in the visual field is confounded by factors associated with the patient response. Sixteen patients who had previously undergone a training regime in automated perimetry over a short time period were followed up to evaluate the longer term learning and fatigue effects. The patients, all attending a glaucoma clinic, were originally naive to automated perimetry. The training period had comprised examination of the right followed by that of the left eye with the Humphrey Field Analyser 630 on each of 3 successive days and again after an interval of 12 days. The follow-up study comprised two examinations on 2 successive days after a follow-up period of between 5 and 15 months (mean 8.7 months). The learning effects present over the initial training period were not observed at the follow-up whilst the fatigue effects in the fellow eye were still apparent.

Adult↗

PubMed1990

The influence of forward light scatter on the visual field indices in glaucoma.

Light scatter was induced in 15 glaucoma patients, exhibiting clear media and moderate field loss, using cells containing varying concentrations of 0.5 microns diameter latex beads in distilled water. The right eye was examined with program G1 on the Octopus 201, and with a 45 degrees threshold profile on the Dicon AP3000, with and without a given cell. Forward light scatter due to the cell was assessed by measuring the depression of contrast sensitivity, with the Nicolet CS2000, under glare conditions. Perimetric mean sensitivity decreased linearly and loss variance decreased curvilinearly with increase in forward scatter. Threshold values for 26 glaucoma patients, determined in the absence of induced scatter, were then corrected for the effects of naturally occurring intraocular light scatter. The recalculated mean defect decreased linearly while loss variance remained essentially unchanged. Forward light scatter therefore predominantly exaggerates diffuse loss; the apparent underestimation of focal defects caused by induced scatter is partly a computational artefact resulting from inapplicable age-matched normal reference data.

Aged↗

PubMed1989

The flash stimulated VEP in the diagnosis of glaucoma.

The Visual Evoked Potential using pattern stimulation has been used in recent years as an attempt to make an early diagnosis of glaucoma. However because of the macular dominance of responses obtained by this method, only diseases involving the papillomacular bundle reveal abnormality; such conditions do not occur in glaucoma. In this study we report the use of the early component (P1) of the flash stimulated visual evoked potential in the diagnosis of primary open angle glaucoma. It appears to provide an objective, accurate and repeatable screening technique. The size of P1 correlates well with the size of optic disc cupping, and field loss. The relationships between systemic vascular disease, P1 reductions, and glaucoma, lend support to the ischaemic origins of the disease.

Adult↗

PubMed1989

The influence of the learning effect on automated perimetry in patients with suspected glaucoma.

The influence of the learning effect on the outcome of automated perimetry was studied as a function of eccentricity. The same comprised 20 patients with suspected glaucoma who were all naive to automated perimetry. Visual field examination of the right eye followed by that of the left eye was undertaken on each of three successive days and after a further interval of 12 days using a customized full-field program of the Humphrey Field Analyser 630 (stimulus size III). The program comprised 60 points out to an eccentricity of 60 degrees with an interstimulus grid of 12 degrees. Global, central, peripheral, superior and inferior mean sensitivity each significantly increased (P less than or equal to 0.01) from the first to the second right eye examinations and from the third to the fourth left eye examinations (P less than or equal to 0.01). The global short-term fluctuation, central mean defect and number of stimulus presentations decreased from the first to the second right eye examination (P 0.01). The order of examination between eyes and the interval between examination sessions influences the response recorded by automated perimetry.

Clinical Competence↗

PubMed1989

Posterior synechiae in intercapsular cataract surgery.

Sixty-eight patients (76 eyes) who had undergone standard intercapsular cataract extraction and posterior chamber lens implantation were reviewed for the presence of posterior synechiae between the anterior capsule remnants and the iris. Thirty-five eyes (46%) had such synechiae, the characteristics of which are described. Risk factors for the development of posterior synechiae in this type of surgery include intraoperative trauma, postoperative inflammation, and the size of the anterior capsulectomy.

Cataract Extraction↗