Phenol red thread test vs Schirmer's test: a comparative study.

AIM: To measure the agreement between Schirmer's and phenol red thread tests in detecting dry eyes. PATIENTS AND METHODS: A total of 103 patients attending preoperative cataract assessment clinic who agreed to be involved in the study were recruited. Each patient had one eye examined by both tests in a random order by two different investigators who were unaware of the results of the other test. Dry eye symptoms were assessed using an interviewer-administered questionnaire. The data were collected after the study period and analysed using kappa statistics to assess the agreement between the two tests. RESULTS: Schirmer's test was positive in 25 patients when a cutoff point of 5 mm was used and positive in 41 patients with a cutoff point of 10 mm. Phenol red thread test was positive in four patients when a cutoff point of 10 mm was used and in 32 patients with a cutoff point of 20 mm. Kappa ranged from 0.067 to 0.3 indicating very weak agreement between the two tests. In all, 27% of the patients had symptoms of dry eyes; however, the agreement between each test and the symptoms was very poor. CONCLUSION: There is very weak agreement between Schirmer's test and phenol red thread tests and between each test and symptoms of dry eyes.

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.

Excimer-laser-induced degradation of fused silica and calcium fluoride for 193-nm lithographic applications.

We report the initial results of a large-scale evaluation of production-grade fused silica and calcium fluoride to be used in 193-nm lithographic applications. The samples have been provided by many different suppliers of materials. A marathon irradiation chamber permits simultaneous exposure of as many as 36 samples at 800 Hz, at fluences from 0.2 to > or =4 (mJ/cm(2))/pulse and pulse counts in excess of 10(9) . The initial absorption and the laser-induced absorption are found to vary over a wide range. The compaction of each fused-silica sample follows a power law, but its parameters can differ widely from sample to sample.

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.

Primary trabeculectomy with 5-fluorouracil for glaucoma secondary to uveitis.

Raised intraocular pressure occurs in a significant proportion of patients with uveitis, and may lead to glaucomatous visual loss. Medical therapy often proves inadequate in controlling intraocular pressure, necessitating surgical intervention but conventional filtering procedures such as trabeculectomy are known to fail more frequently in this group than in non-inflamed eyes. Adjunctive subconjunctival 5-fluorouracil (5-FU) has been shown to improve the success of trabeculectomy in a variety of secondary glaucomas. This retrospective study examined the effect of postoperative 5-FU administration on the outcome of trabeculectomy in uveitis-related glaucoma in 28 eyes of 26 patients. Eyes treated with adjunctive 5-FU showed a more prolonged control of intraocular pressure, and a longer median time to failure of control than untreated eyes. Trabeculectomy failure was more common and occurred earlier when a limbus-based conjunctival flap had been used, in patients of black ethnic origin, and if there had been previous intraocular surgery. Additional hypotensive therapy with topical ß-blockers was required more frequently in eyes which had not received 5-FU, and where a limbus-based conjunctival flap had been employed, all eyes in the latter group requiring ß-blockers one year after surgery. Intraocular inflammation was under satisfactory control in all patients at the time of surgery, and no deleterious effect on control of uveitis in relation to surgical intervention was observed.

Excimer laser photorefractive keratectomy for myopia: 12 month follow-up.

A prospective study of excimer laser photorefractive keratectomy was performed with the aim of correcting a range of myopic errors between -1.00 and -10.00 dioptres. Corneal healing was monitored through the first post-operative year by serial assessments of refraction, contrast sensitivity, corneal haze, pachymetry and keratometry. Eighty-one patients were recruited for the study. At 12 months 81% were within +/- 1.00 dioptre of desired emmetropia and with unaided vision of 6/12. Contrast sensitivity was found by Pelli-Robson assessment to be reduced throughout the 12 months and regression analysis predicted recovery by 2 years. At 12 months, however, only 15% of patients were found to have lost a single line of best corrected Snellen acuity. Predictability of results was found to be greatest for initial errors less than -4.00 dioptres. No serious complications were observed during the follow-up period, but refraction had not stabilised in all cases and patients remain under review.

The importance of cellular changes in the conjunctiva of patients with uveitic glaucoma undergoing trabeculectomy.

The results of trabeculectomy in patients with glaucoma secondary to uveitis are poor, but the exact cause of this remains unknown. Therefore, a study was undertaken to determine differences between conjunctiva from patients with glaucoma secondary to uveitis and that from patients with primary open angle glaucoma. Conjunctival biopsies from three patient groups were quantitatively analysed by light microscopy. Group A consisted of 10 patients with glaucoma secondary to uveitis who, prior to surgery, had been treated with topical steroids and topical beta-blocker drugs. Control groups (groups B and C) each consisted of 10 patients with primary open angle glaucoma for whom primary trabeculectomy (group B) or trabeculectomy following failure of topical beta-blockers alone (group C) was planned. Treatment with topical beta-blocker drugs was found to redistribute mast cells within the conjunctiva but to have no significant effect on cell numbers. In comparison with either control group, uveitic conjunctiva was found to contain significantly more fibroblasts, lymphocytes and macrophages. It is possible that these differences are responsible for an enhanced risk of excessive external bleb fibrosis, failure of filtration surgery and poor results with adjunctive 5-fluorouracil.

Radial keratotomy: a review of 300 cases.

Three hundred consecutive cases of radial keratotomy performed between 1985 and 1990 were reviewed. There were no sight threatening complications of surgery and no patient lost one or more lines of corrected Snellen acuity. Overall 78.7% saw 6/12 or better unaided postoperatively and 51.7% saw 6/6 or better. Refraction showed 61.3% to be within 1 dioptre of emmetropia and 86.7% were within 2 dioptres. Further analysis demonstrated that results of unaided acuity and proximity to emmetropia were much better for low (< -2.87 D) and moderate (-3.0 to -5.87 D) than for high (> -6.0 D) myopes.

Congenital lacrimal fistula.

Congenital lacrimal fistula is a rare developmental condition. Patients may be asymptomatic or have tearing from the fistula, the eye or both. The clinical features of 60 patients are reviewed, including presenting symptoms, presence of other lacrimal or systemic anomalies and morphology of the fistula. A detailed description is given of the surgical technique utilised in patients whose symptoms warrant surgical intervention. The results of this technique are presented and alternative treatment strategies are discussed. Theories of the aetiology of the condition are reviewed and morphological and histological evidence is presented to support our belief that congenital lacrimal fistulae represent aberrant canaliculi.

Modelling of changes in the corneal endothelium after cataract surgery and penetrating keratoplasty.

Long term changes in endothelial cell density were monitored in three groups of patients after surgery. One group underwent uncomplicated cataract surgery, one group complicated cataract surgery which eventually progressed to corneal decompensation, and one group penetrating keratoplasty. A mathematical model is presented which describes endothelial cell loss after surgery as an exponential decay process towards an asymptote with constant rate of cell loss over time. When fitted to the data from the three groups there is excellent agreement in each case. Discriminant analysis techniques were applied to model predictions to assess the likelihood of late corneal decompensation after surgery. From measurements of endothelial cell density before and after surgery we were able to correctly assign patients undergoing cataract surgery to decompensation or non-decompensation groups in 85.7% and 92.7% of cases respectively.

Surgical management of essential blepharospasm.

We have reviewed the surgical management of essential blepharospasm over the last 15 years, comparing the results from facial nerve avulsion with those from orbicularis muscle stripping. After facial nerve avulsion 50% of patients remained free of troublesome spasm for 15 months after surgery, but only 25% remained so for more than two years. Following orbicularis oculi myectomy 50% of patients were free of troublesome spasms for 30 months after surgery and 55% of patients had relief from spasm for more than two years. Secondary effects of the two procedures are compared and are found to be fewer after orbicularis myectomy. There were no major complications after either form of surgery. Botulinum toxin is the treatment of first choice for this condition. If this becomes ineffective or inconvenient, surgical treatment is warranted and should not be deferred for fear of severe side effects of treatment, since these are rare. Protractor myectomy gives longer relief from blepharospasm than facial nerve avulsion and has fewer complications. However, it is technically difficult, time consuming, and has greater peroperative morbidity. Facial nerve avulsion may therefore still have a role in selected patients.

Microbial keratitis after penetrating keratoplasty.

Thirty cases of microbial keratitis after penetrating keratoplasty were reviewed to examine the associated risk factors, the spectrum of pathogens and the prognosis for graft survival and visual outcome. The indications for keratoplasty in this group differed markedly from those for all corneal grafts performed with a much higher incidence of previous microbial keratitis and of herpes simplex keratitis. A positive culture was obtained in 93% of cases and in contrast to microbial keratitis overall, Gram positive organisms predominated particularly streptococcus pneumoniae and staphylococcus aureus. Risk factors identified were loose or broken sutures, graft decompensation and a poor ocular surface environment. There was a poor prognosis for graft survival with only 23% of cases retaining a clear graft. Overall 53% of cases were regrafted.

Changing indications for keratoplasty.

The indications for keratoplasty at Moorfields Eye Hospital were reviewed for the period 1985-1987. There were 500 consecutive cases of which 472 underwent penetrating keratoplasty and 28 lamellar keratoplasty; of the grafts performed 31 were acute procedures. The most common indication for penetrating keratoplasty was keratoconus accounting for 34.2% of cases and for lamellar keratoplasty corneal dystrophies accounting for 28.6% of cases. This contrasts with other studies which have found pseudophakic bullous keratopathy to be the leading indication for penetrating keratoplasty. Possible reasons for this difference are discussed and the current series is compared to two previous series presented from this hospital in 1959 and 1974.

'Sterile' corneal infiltrates in contact lens wearers.

Ninety four patients with 'sterile' keratitis presenting consecutively over a nine month period to the Accident and Emergency Department of Moorfields Eye Hospital were studied. This condition was found to account for 0.49% of all new casualties. A significant association was found in these patients, compared with controls, with contact lens hygiene, particularly for daily wear soft contact lenses, and contact lens case contamination by bacteria suggesting that these may be important factors in the aetiology of 'sterile' keratitis. Compared to gas permeable hard contact lenses the relative risk of developing 'sterile' keratitis in our patients was found to be 2.3 times higher with extended wear soft contact lenses, 1.56 times higher with daily wear soft contact lenses and 0.509 with polymethylmethacrylate lenses (test of trend p-value less than 0.05). The results indicate that 'sterile' corneal infiltrates are related to contact lens hygiene and in part to contact lens case contamination by bacteria and also to the type of lens worn.

Positive correlation of corneal thickness and endothelial cell loss. Serial measurements after cataract surgery.

A significant linear correlation was found between increase in corneal thickness (delta CT) in the immediate postoperative period and percentage of cell loss one and six months after surgery in a prospective study on cataract surgery. Eyes were grouped according to delta CT, and the groups were compared according to the percentage of cell loss. Eyes with delta CT of 0.1 mm or more at five days lost significantly more cells at one and six months than eyes with delta CT of less than 0.025 mm. Eyes were then regrouped according to the percentage of cell loss. Those with cell loss of 30% or more were found to have significantly greater delta CT at 48 hours and five days than eyes with cell loss of less than 30%. The derived probability of cell loss of 30% or more increases the greater the value of delta CT. For delta CT of 100 micron or more at five days, the probability of high cell loss is 30%; this is nearly three times the likelihood that high cell loss had occurred when delta CT is less than 100 micron. Our results suggest that delta CT could be a useful clinical indicator of endothelial cell loss.

Bullous keratopathy: a study of endothelial cell morphology in patients undergoing cataract surgery.

Preoperative and postoperative endothelial cell morphology was examined in three types of patients participating in a randomised, controlled trial of cataract surgery. The first sustained modest endothelial cell loss and served as controls, the second and third sustained high cell loss, but only the latter progressed to bullous keratopathy. The technique of examining endothelial cell morphology is described and its validity assessed. Measures of cell area, number of sides, side length, and variation in cell size and cell shape were utilised. No significant differences were found between the three groups by any of the preoperative morphological measures. Furthermore, postoperative values of variation in cell shape and cell size did not differ significantly between the groups. No evidence was found in our patients to support the hypothesis that eyes at particular risk of developing bullous keratopathy may be differentiated on the basis of their preoperative or early postoperative endothelial cell morphology.