Biomedical subjects
K G Claridge
Publications and source records attributed to K G Claridge.
A 10 year retrospective survey of cataract surgery and endophthalmitis in a single eye unit: injectable lenses lower the incidence of endophthalmitis.
AIM: To study the incidence of endophthalmitis following cataract surgery over a 10 year period, and to examine ways in which this may be related to changes in surgical technique. METHODS: All cases of endophthalmitis occurring over a 10 year period within a single ophthalmic unit in the United Kingdom were reviewed, and possible risk factors identified. RESULTS: During the study period, as the technique of extracapsular cataract surgery was replaced by phacoemulsification, there was a commensurate reduction in the incidence of endophthalmitis. Injectable IOLs were associated with the lowest risk of postoperative endophthalmitis (0.028%). CONCLUSIONS: Injectable intraocular lenses do not make contact with the ocular surface and this may result in the observed lower rate of endophthalmitis. This, and the ease with which they can be inserted through small incisions, support their use as the first line method of lens insertion.
A case of a 360 degree exuberant trabeculectomy bleb.
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Combined radiotherapy and medical immunosuppression in the management of thyroid eye disease.
Although systemic steroids or orbital radiotherapy are effective in limiting the inflammatory response in thyroid eye disease (TED), there are reports of over 70% of treated patients requiring subsequent rehabilitative surgery: either orbital decompression or strabismus correction. This study investigated whether combined immunosuppression with primary orbital radiotherapy together with azathioprine and low-dose prednisolone, applied early in the active disease state, was more effective in treating TED. Forty consecutive patients with active TED were recruited. Orbital MRI (STIR sequence) was used to assess disease activity. Median duration of symptoms was 1.0 year. Subjects were treated with bilateral orbital radiotherapy (20 Gy in 10 fractions) and oral prednisolone and azathioprine. Pre- and post-treatment activity was measured clinically, including uniocular field of fixation, Mourits score and total eye score, until TED became inactive off all treatment. Before treatment, 15 subjects had signs of dysthyroid optic neuropathy, 35 had significant motility restriction and 38 had marked soft tissue signs. On average TED became inactive after 1.2 years (SD 0.7) of immunosuppression, and treatment was well tolerated. One patient required subsequent cosmetic orbital decompression, 6 had successful strabismus surgery and 13 required minor cosmetic lid surgery. Compared with previously reported treatment regimes we think that combined orbital radiotherapy and medical immunosuppression is far more effective than either treatment alone in the management of active TED, and led to fewer side effects of high-dose steroids. In particular there was more than a four-fold reduction in the requirement for orbital decompression and strabismus surgery.
The effect of trabeculectomy on refraction, keratometry and corneal topography.
After successful trabeculectomy patients often complain of reduction in vision even after several months. Amongst other factors, corneal astigmatism appears to be altered. A pilot study measuring, pre- and post-operative corneal topography indicated three types of astigmatic change: some patients develop a relative superior corneal steepening, others a superior flattening and yet others complex regional changes that do not conform to either of these patterns. The present study was designed to evaluate further these patterns of variation in corneal curvature and to look for corresponding refractive and keratometry changes. Twenty-nine patients admitted for trabeculectomy had pre-operative assessment of subjective and automated refraction, manual keratometry and corneal topography from which simulated keratometry values were calculated. A standard trabeculectomy procedure was performed and post-operative measurements of the same parameters were taken at 1 and 3 months after surgery. Similar patterns of corneal topographic change to those found in our pilot study were noted. In both the superior steepening and superior flattening groups there was an increase in vertical keratometry and a shift towards 'with-the-rule' astigmatism. Furthermore a 1 year analysis of 13 patients from our pilot study indicated that the topographic changes lasted for at least 12 months after surgery. We conclude that computer-assisted corneal topography reveals complex regional changes in corneal curvature that are not readily detected from alterations in refraction or keratometry. These changes are sufficiently great to have a significant effect on visual function in some patients.
Should second eye cataract surgery be rationed?
To conserve limited resources, healthcare purchasers are questioning whether they should ration second eye cataract surgery after successful unilateral extraction. The effect this would have on overall cataract workload is unknown. The clinical indications for performing second eye cataract extraction were recorded from the medical notes of a random group of patients undergoing second eye surgery over a 1 year period. Twenty-six per cent of all cataract operations were on second eyes and, of these, 21.5% of operations were on patients with coexistent ocular pathology, requiring clear optical media for disease monitoring, and 18.4% were on patients who had failed to achieve a satisfactory result after unilateral cataract surgery (visual acuity 6/18 or worse). Another 43.6% had severe binocular visual disability due to their remaining cataract. Only 4.4% of all cataract operations performed during the study period were on second eyes of patients with no other ocular pathology who had had successful unilateral surgery and had only mild symptoms from their remaining cataract (visual acuity 6/12 or better in second eye). Therefore, the overall savings made by rationing second eye cataract surgery to those patients who have only mild visual disability would be slight. If the proportion of cataract operations performed as daycases under local anaesthetic were increased, sufficient resources would be released to enable all patients to achieve maximum binocular visual rehabilitation.
Diurnal variation in pulsatile ocular blood flow in normal and glaucomatous eyes.
Ocular blood flow, in particular to the optic nerve head, is considered important in determining the extent of glaucomatous damage. The 24-hour variation in the pulsatile component of ocular blood flow (POBF) was measured using a pneumotonometer linked to the Langham Ocular Blood Flow System. Intraocular pressure (IOP), ocular pulse amplitude, POBF, systemic blood pressure and heart rate were recorded at three-hourly intervals over a 24-hour period in 10 ocular hypertensives, eight patients with primary open angle glaucoma (POAG) treated with timolol eyedrops (G timolol 0.25%), and eight ocular normotensive control subjects. The POAG subjects were readmitted for a second set of 24-hour measurements after temporarily discontinuing G timolol for two weeks. The POBF showed no significant diurnal variation in any of the patient groups, the POAG values being taken from the "off treatment" period. By contrast, there were overnight falls in IOP, ocular pulse amplitude, blood pressure and heart rate, which reached significance in some groups. This suggests that overall there are compensatory changes in IOP, blood pressure, heart rate, and perhaps ocular vascular resistance, to preserve POBF overnight. Within all groups there was much individual variation, with some subjects showing an overnight fall in POBF, suggesting a lack of autoregulation in these cases who might prove to be at greater risk of developing nocturnal glaucomatous damage. When timolol was withdrawn from POAG subjects, there was no change in POBF despite an increase in IOP, implying that timolol, though effective as ocular hypotensive, did not alter POBF.
Ocular pulse measurements to assess pulsatile blood flow in carotid artery disease.
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The effect of topical pilocarpine on pulsatile ocular blood flow.
Ocular blood flow is considered an important factor in determining the extent of visual damage occurring in primary open angle glaucoma (POAG). The effect of topical pilocarpine, a parasympathomimetic vasodilator, on the pulsatile ocular blood flow (POBF) in POAG subjects was studied. A pneumotonometer linked to the Langham Ocular Blood Flow System recorded the intraocular pressure (IOP) pulse from which POBF was calculated. Measurements were taken from 18 POAG subjects treated with both G pilocarpine and G timolol, 2 weeks after withdrawing G pilocarpine and again 1 week after reinstituting full treatment. Recordings from 20 POAG patients treated with only G timolol were taken as control values. There was no significant difference in the IOP or POBF between the controls and POAG patients on dual therapy. Furthermore when G pilocarpine was temporarily withdrawn there was no significant change in POBF despite a significant rise in IOP. The results imply that aqueous pilocarpine has no direct effect on the pulsatile component of ocular blood.
Refsum disease: the presentation and ophthalmic aspects of Refsum disease in a series of 23 patients.
Refsum disease (heredopathia atactica polyneuritiformis) was first described in 1946 and is a rare recessively inherited metabolic disease affecting phytanic acid metabolism. It causes retinitis pigmentosa, cataracts, a chronic polyneuropathy, cerebellar ataxia and cardiac arrhythmias amongst other clinical signs. By limiting dietary intake, plasma phytanic acid levels fall with an improvement in the neurological signs. The onset of retinitis pigmentosa usually precedes biochemical diagnosis by several years by which time the retinal damage is severe. A series of 23 patients have been reviewed. There was an average delay of 11 years (range 1-28 years) between the patient presenting to the ophthalmologist and being diagnosed as having Refsum disease. Although serial examinations have failed to show a definite change in the course of visual deterioration with treatment, early diagnosis is important to prevent the development of neurological disease.