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Biomedical subjects

P K Wishart

Publications and source records attributed to P K Wishart.

At least 19 recordsLinked to original sources
PubMed1998

Is visual field evaluation using multiple correlations and linear regressions useful? An evaluation of Delphi perimetry.

BACKGROUND: Delphi perimetry is a method of visual field examination which produces a statistical estimation of the visual field by testing only four critical points of the central visual field. This study was performed to evaluate this technique for the detection of glaucomatous field loss. METHOD: Patients with glaucoma and ocular hypertension underwent Delphi perimetry and Humphrey visual field analysis (HVFA) program 24-2. The visual field results of both examination were compared. RESULTS: Of 262 eyes from 199 patients, 120 eyes showed glaucomatous defects by HVFA and 142 were normal. Delphi perimetry showed abnormal visual fields in 107 eyes, 13 of which were false-positive results as Humphrey visual fields were normal. Delphi classified 155 fields as normal, of which 26 were false negatives as Humphrey visual fields showed glaucomatous defects. Therefore, the sensitivity of Delphi perimetry for the detection of glaucomatous visual field defect was 78% and the specificity was 91%. In the 26 false-negative eyes, the most common defect missed was an isolated paracentral scotoma or an early nasal step. Furthermore, 27 of the 94 glaucomatous eyes classified as abnormal by Delphi had defects estimated by Delphi perimetry that corresponded poorly to the field loss demonstrated by Humphrey visual field analysis. Therefore, qualitative sensitivity and specificity of Delphi perimetry for producing an accurate representation of the location, extent and defect depth of glaucomatous visual field loss would be 48.8% and 72% respectively. CONCLUSION: In this study Delphi perimetry failed to give an accurate statistical estimation of the visual field in an unacceptably high number of cases; therefore, it cannot be recommended for clinical use.

False Positive Reactions↗
PubMed1998

Long-term intraocular pressure control after cataract extraction with trabeculectomy: phacoemulsification versus extracapsular technique.

PURPOSE: To compare long-term intraocular pressure (IOP) control after extracapsular cataract extraction and intraocular lens (IOL) implantation combined with trabeculectomy (ECCE + TRAB) with that after phacotrabeculectomy and IOL implantation. SETTING: Glaucoma Unit, Royal Liverpool University Hospital, Liverpool, England. METHOD: This retrospective study comprised 32 eyes having ECCE + TRAB and 31 eyes having phacotrabeculectomy with a mean follow-up of 37.5 and 41.0 months, respectively. The need for pressure-lowering medication was recorded. Kaplan-Meier curves were created for each group. RESULTS: At every measurement after 3 weeks of follow-up, significantly fewer eyes in the phacotrabeculectomy group required IOP-lowering medication (P = .04). CONCLUSIONS: After both ECCE + TRAB and phacotrabeculectomy, IOP control was achieved in significantly more eyes on fewer pressure-lowering medications than preoperatively. Phacotrabeculectomy with IOL implantation led to better unaided long-term postoperative IOP control than ECCE + TRAB with IOL implantation.

Aged↗
PubMed1997

Apparent glaucomatous visual field defects caused by dermatochalasis.

We have studied the effects of dermatochalasis on Humphrey automated perimetry of the central 24 degrees visual field. Fifteen visual fields of 9 ocular hypertensive patients (18 eyes) were found to be incongruous with their apparently healthy optic discs. Examination revealed dermatochalasis, which was felt to be responsible for the field defects. This was confirmed by reversal of the defects on repeating the field test (programme 24-2) with the redundant upper lid skin taped up, or in 2 cases following blepharoplasty. The defects always involved the superior visual field. The deepest and largest defects were sited in the supero-temporal quadrant in 13 of the 15 affected fields and the supero-nasal quadrant in 2 fields. The most common pattern was a temporally skewed defect which reflected the tendency of the loose upper lid skin to be greater in extent temporally than nasally. In 7 fields the supero-temporal defect extended to fuse with the blind spot, mimicking a superior arcuate scotoma. Temporal extension of the field defects below the horizontal meridian occurred in 5 fields. In cases where visual field testing was repeated without taping up the lid inter-test fluctuation in scotoma size and depth was observed, although the position of scotomas when present within the visual field remained constant. We conclude that dermatochalasis has the potential to confound diagnostic automated visual field testing for glaucoma.

Aged↗
PubMed1997

A full-thickness scleral graft for the surgical management of a late filtration bleb leak.

BACKGROUND AND OBJECTIVES: Late bleb leak may follow months to years after filtration surgery. This article describes the surgical repair of eight leaking blebs using a full-thickness scleral graft and analyzes the efficacy of the procedure and its effect on intraocular pressure (IOP) control. PATIENTS AND METHODS: The indications for surgical bleb revision were hypotony maculopathy (2 eyes), endophthalmitis (2 eyes), bleb infection (2 eyes), and chronic epiphora and blurring of vision (2 eyes). All eyes were treated surgically through bleb excision and repair of the scleral defect with a full-thickness scleral graft. Conjunctival closure was performed either by its advancement to the limbus or by free conjunctival autograft. Follow-up ranged from 4 months to 7 years. RESULTS: Surgery stopped the leak in all cases, and hypotony was relieved without loss of long-term IOP control. However, early postoperative IOP rises (> 30 mm Hg) occurred in 2 eyes and a pressure-lowering medication was necessary to achieve long-term IOP control (IOP < 22 mm Hg) in 3 eyes. CONCLUSIONS: The technique described is an effective procedure for the treatment of late bleb leaks and is especially useful for the treatment of leaks found in association with full-thickness scleral defects. IOP spikes in the early postoperative period may occur, but long-term IOP control can be expected without the need for further filtration surgery.

Aged↗
PubMed1995

Determining progressive visual field loss in serial Humphrey visual fields.

PURPOSE: To evaluate the three commercially available computerized statistical algorithms for determining progression of glaucomatous field loss in serial Humphrey fields. METHODS: Serial Humphrey fields of 102 ocular hypertensive and glaucomatous eyes were analyzed by linear regression analysis of Statpac, glaucoma change probability and Progressor Programme, and the results compared with a retrospectively determined clinical outcome. RESULTS: Linear regression analysis of Statpac identified progression in 11 field series, glaucoma change probability identified progression in 23 field series, and Progressor Programme identified progression in 27 field series. Clinical outcome identified much less-progression than any of the three algorithms, determining that only seven eyes showed deterioration. There was a wide variation of results from analysis of the same group of field series by the three different algorithms. In contrast to the other two algorithms, which detected progression in similar percentages of both ocular hypertension and glaucoma field series. Progressor Programme detected progression predominantly in glaucoma field series. CONCLUSIONS: There was a high degree of variability among the three different algorithms for determining visual field progression, and none of them correlated well with clinical impression.

Algorithms↗
PubMed1994

Flicker perimetry using a luminance threshold strategy at frequencies from 5-25 Hz in glaucoma, ocular hypertension and normal controls.

A prototype automated flicker perimeter was used to investigate flicker luminance thresholds in glaucoma patients (n = 11), ocular hypertensives (high risk n = 10, low and intermediate risk n = 21) and normal controls (n = 10). Differential light sensitivity was measured for one eye of each subject using a flickering stimulus at frequencies of 5, 10, 15, 20 and 25 Hz at ten test locations of 1 degree in the arcuate and nasal regions of the central 50 degrees of the visual field using a 4-2 dB staircase. The glaucoma patients had significantly reduced sensitivities for all frequencies (p < 0.001) with minimum sensitivity at 15 Hz. The 'high risk' ocular hypertensives had significantly reduced sensitivities at 10 and 15 Hz (p < 0.02). At present the ocular hypertensive patients in this study show no abnormalities demonstrable by conventional automated static perimetry. These findings may represent the earliest of perimetric deficits in patients with glaucomatous optic neuropathy.

Female↗
PubMed1993

Neovascular complications after central retinal vein occlusion.

An 8-year retrospective study of patients suffering a central retinal vein occlusion (CRVO) was undertaken to study secondary new vessel formation and whether pathologies known to predispose to CRVO influenced the occurrence of these neovascular complications and their responsiveness to treatment. Seventy-three patients were studied. Ocular neovascularisation had occurred in 60%. More specifically 39% developed neovascular glaucoma. Panretinal photocoagulation produced regression in only 37% of those with established neovascularisation and was unsuccessful in preventing neovascularisation in five patients treated prophylactically. Patients with pre-existing primary open angle glaucoma (POAG) were statistically more likely to develop ocular neovascularisation (p = 0.02), which was also less responsive to laser therapy (p = 0.02). Adequate prior glaucoma therapy did not protect against this enhanced complication rate. It was concluded that POAG is a significant risk factor for developing ocular neovascularisation after CRVO which will be refractory to laser therapy.

Adult↗
PubMed1993

Is high initial aqueous outflow of benefit in trabeculectomy?

A modification of the trabeculectomy technique was designed in an attempt to increase the outflow of aqueous into the subconjunctival space in the early post-operative period. This 'high flow' method was compared with a control group of eyes undergoing a standard trabeculectomy. Fifty-three eyes of 44 patients were recruited to this study. Follow-up was for a minimum of 12 months (mean 20 months). The high flow method resulted in lower intraocular pressures (IOP) on days 1 and 2 and shallower anterior chambers without increased incidence of conjunctival wound leak, suggesting that high outflow was indeed achieved. However, long-term control of IOP was not better than that achieved by the conventional technique. IOP control (IOP < 21 mmHg) was achieved in 64.2% of eyes (34 eyes) without additional topical medication. IOP control with topical medication was satisfactory in the remaining 19 eyes, and no patient required further drainage surgery. Further analysis of the data showed that the most important factor determining success or failure of trabeculectomy in controlling IOP was the duration and number of prior topical medications. The success rate for trabeculectomy was significantly higher in those eyes with a shorter duration and quantity of prior topical therapy.

Aged↗
PubMed1993

Oculokinetic perimetry compared with Humphrey visual field analysis in the detection of glaucomatous visual field loss.

The ability of oculokinetic perimetry (OKP) to detect glaucomatous central visual field loss was assessed by comparison with the results of Humphrey visual field analysis (HVFA) in a group of patients attending a glaucoma clinic. Fifty-six patients with stable visual fields and good reliability indices on previous automated perimetry examinations underwent programmes 24-1 or 24-2 of the Humphrey visual field analyser and the results compared with those of a field test using a hand-held OKP chart. Forty-three patients had a glaucomatous visual field defect demonstrated by HVFA, and 35 showed a defect to OKP. Thirteen patients were shown to have normal fields on HVFA, and in 21 patients the OKP test was normal. Comparison of the two test results showed that of the 35 patients with abnormal OKP tests, in 26 the result was a true positive (HVFA also abnormal) and in 9 a false positive (HVFA normal). In the 21 patients with negative OKP tests the results were judged false negatives in 13 (HFVA showed glaucomatous visual field loss) while in 8 they were true negatives (HVFA normal). Therefore the sensitivity of OKP for the detection of glaucomatous visual field loss was 60.5% and the specificity for the identification of individuals with glaucomatous visual field loss was 61.5%. In the 26 patients with true positive results there were 36 eyes with positive OKP charts corresponding to defects on HVFA. Correlation of the number of defects on OKP with the mean deviation and corrected pattern standard deviation of their respective HVFA charts showed a near linear correlation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Combined cataract extraction and trabeculectomy: phacoemulsification compared with extracapsular technique.

Thirty-four eyes undergoing phacoemulsification and trabeculectomy (PHACO + TRAB) were followed prospectively for 1 year postoperatively. The results of surgery were compared with those, obtained retrospectively, of the previous 34 extracapsular cataract extractions with trabeculectomy (ECCE + TRAB) performed by the same surgical team. All eyes received posterior chamber intraocular lens implants. Preoperatively, the two groups did not differ significantly in terms of age, gender distribution, or degree and duration of glaucoma and cataract. Mean postoperative follow up for the ECCE+TRAB group was 13.6 months; for the PHACO + TRAB group, 12.6 months (P = .1). As compared with the ECCE + TRAB group, the PHACO + TRAB group had earlier visual rehabilitation, less postoperative astigmatism (P < .001), and improved long-term intraocular pressure control (P = .04). Early postoperative pressure spikes occurred in 32% of the ECCE + TRAB eyes and in 23.5% of the PHACO + TRAB eyes (P = .2). Other postoperative complications occurred more commonly in the ECCE + TRAB group: hyphema (P < .001), fibrinous iritis (P < .01), choroidal detachment (P < .05), and hypotony (P < .05). Posterior capsular opacification was significantly more common in the ECCE + TRAB group (P < .02). These major differences probably are attributable primarily to the small incision used in phacoemulsification, which is associated with sustained IOP control during the operation, a small stable wound with low postoperative astigmatism, and early stabilization of refraction.

Aged↗
PubMed1993

Reformation of the anterior chamber following trabeculectomy.

Sixteen eyes requiring surgical reformation of the anterior chamber (AC) in our Unit from December 1987 to August 1991 were studied retrospectively to determine the incidence of the problem in our hospital and to evaluate the operative measures used to restore the AC. The mean preoperative AC depth of these 16 eyes was 1.92 mm (range, 1.50 to 2.50 mm). Nine had a history of angle-closure glaucoma. Poor surgical technique was a contributing factor in the development of a flat AC in 3. Of the remaining 13 eyes, 11 had a trabeculectomy with a fornix-based, and 2 with a limbus-based, conjunctival flap. Wound leaks occurred in 10 eyes with fornix-based flaps, but in none of the eyes with limbus-based flaps. Factors associated significantly with the development of flat AC following trabeculectomy were: a preoperative shallow AC, a history of angle-closure glaucoma, and the use of a fornix-based conjunctival flap. Avoiding wound leakage when performing trabeculectomy in eyes with a shallow AC or a history of angle-closure glaucoma by using a limbus-based flap may help prevent postoperative flat AC.

Adult↗
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

Ocular hypertension: correlation of anterior chamber angle width and risk of progression to glaucoma.

Twenty five patients with ocular hypertension (OH) and a narrow angle and 34 patients with OH and an open angle were followed for an average of six years. One eye of each patient had been randomly assigned to treatment with topical timolol. A shallow axial anterior chamber depth and a narrow angle (van Herick Grade 2 or less) was associated with the development of angle-closure glaucoma (ACG) in the narrow angle group, but the open angle group developed significantly more visual field loss. Nine patients (36%) in the narrow angle group developed ACG, and nine patients (26.5%) in the open angle group developed glaucomatous discs and field loss. The reduction in intraocular pressure due to topical timolol was equal in the narrow angle and the open angle groups, but topical timolol did not protect against the development of angle-closure glaucoma or visual field loss.

Aged↗
PubMed1992

Intraocular pressure measurement in children using the Keeler Pulsair tonometer.

A study to determine whether Keeler Pulsair tonometry is a feasible alternative to tonometry under general anaesthesia in children was undertaken. We recruited 53 children aged from 6 months to 9 years old. Readings were obtainable from 78% and a complete set of four readings from each eye was obtained from 45% of the group in an out-patient setting. Averaged Pulsair measurements agreed well with Perkins applanation tonometry values under general anaesthesia. Techniques to improve compliance are discussed. In conclusion, the Pulsair tonometer is a viable method for obtaining estimates of intraocular pressure in children in this age-group.

Anesthesia, General↗
PubMed1991

Can the pilocarpine phenylephrine provocative test be used to detect covert angle closure?

Mapstone introduced the term 'partial angle closure' to describe how eyes with apparently open angles could be damaged by a covert angle closing mechanism, identifiable by a positive result of the pilocarpine phenylephrine provocative test (PPPT). This paper presents a 10-year follow-up of 68 patients with narrow but open anterior chamber angles who, on the basis of a positive PPPT, underwent peripheral iridectomy (PI) or laser iridotomy LI). In the 42 patients with glaucoma or ocular hypertension the mean intraocular pressure (IOP) was unchanged following iridectomy; 45% of eyes which showed glaucomatous optic disc damage at presentation and 25.6% of ocular hypertensive eyes subsequently required trabeculectomy to achieve IOP control. In 16 patients with no ocular abnormality other than a narrow angle 19 eyes had positive PPPTs and underwent PI. After a 10-year follow-up only one of the 13 untreated fellow eyes developed angle closure glaucoma. As this is usually bilateral, many of the positive tests in this group of patients may therefore have been false positives. This study shows that eyes with narrow angles which had positive PPPT results did not benefit from PI iridectomy or LI and therefore a positive PPPT is not indicative of the presence of an angle closing mechanism.

Follow-Up Studies↗
PubMed1991

Does the pilocarpine phenylephrine provocative test help in the management of acute and subacute angle closure glaucoma?

The pilocarpine phenylephrine provocative test (PPPT) has been described as a highly sensitive method to identify eyes suffering from or at risk of angle closure glaucoma (ACG). This paper reports on average 10 years follow-up of the outcome of cases of primary acute ACG and subacute ACG in which the management was determined by the result of the PPPT--a positive result indicating the need for a peripheral iridectomy, a negative result conservative treatment. In spite of a negative PPPT the fellow eyes of cases of acute ACG treated conservatively had a high rate (40%) of development of ACG. Similarly, in eyes with a history of subacute ACG with a negative PPPT, ACG developed at some stage during the follow-up in 60%. Peripheral iridectomy alone resulted in normal intraocular pressure in 63% of eyes that had suffered an attack of acute ACG. In hypertensive eyes that presented with subacute ACG, however, only one eye became normotensive following peripheral iridectomy alone. In the subacute ACG group a positive PPPT was closely related to the presence of glaucomatous optic disc damage. These results indicate that the PPPT lacks sensitivity in detecting eyes at risk of angle closure glaucoma, and a positive result is likely in eyes with damaged outflow that will not respond to peripheral iridectomy.

Adult↗