Expanding role of local anaesthesia in vitreoretinal surgery.

PURPOSE: Local anaesthesia (LA) is increasingly common in vitreoretinal surgery. However, younger patients often have such surgery under general anaesthesia (GA). We reanalysed the anaesthetic practice for vitreoretinal surgery in our unit over a 19-month period. METHODS: A total of 1003 patients undergoing vitreoretinal surgery between August 2000 and February 2002 were studied. Type of surgery, patient pain score to anaesthesia and surgery, need for sedation and incidence of complications related to the local anaesthetic were recorded. Comparisons were made between this case series and previous data from our unit. RESULTS: In total, 920/1003 (91.7%) patients had LA. Total operations comprised 418 vitrectomies, 518 retinopexies with or without vitrectomy and 67 buckling procedures. More patients under the age of 35 years had LA than previously (60.2 vs 35.7%, P<0.001). In 920/920 (100%) of cases, LA was administered via intraconal injection, compared to 164/1221 (13.4%) of procedures previously. Significantly more patients under the age of 35 years required sedation (35.9%) than did older patients (19.2%). Overall, use of sedation was significantly increased since our previous study (20.2 vs 7.8%). Anaesthesia and surgery were well tolerated by patients. There were no cases of orbital haemorrhage or ocular perforation. Complications included bradycardia requiring atropine 1/920 (0.1%) and chemosis 88/920 (9.6%). CONCLUSIONS: LA is well tolerated and effective even in younger patients. Sedation may well be required in younger patients and for procedures involving scleral buckling. The main indication for GA was patient preference. Despite this, such patients accounted for only 5.2% of the total.

Pilot National Electronic Cataract Surgery Survey: I. Method, descriptive, and process features.

AIM: The primary aim of this large pilot survey was to demonstrate the use and benefits of electronic data collection with respect to rapidly monitoring the access, delivery, and outcome of cataract surgery in the NHS and to update benchmark standards for these parameters of care. METHOD: Eight NHS departments that currently use specialty-specific electronic clinical systems or Electronic Patient Records (EPR) to collect a minimum preoperative, operative, and anaesthetic data set for cataract surgery agreed to pool their data. RESULTS: A total of 162 surgeons from 50 consultant teams and eight NHS Trusts agreed to submit their data on a total of 16,541 operations for age-related cataract. This report describes the age, sex, and ethnic profiles of the patients, waiting time for surgery, ocular copathology causing a reason for a guarded visual prognosis, visual impairment on admission, visual acuity in the operated eye, and the characteristics of the anaesthetic and surgical procedures. CONCLUSIONS: This survey has raised the benchmark standards established by the last National Survey in 1997. There has been a near universal switch to day case, phacosurgery under local anaesthesia (all used in > or =99.1% of cases compared with 70, 77, and 86%, respectively in 1997). The visual impairment in the operated eye is lower with 45% having 6 / 12 or better compared with 27% in 1997. Waiting times and visual impairment in the fellow eye have probably improved although data collection for these variables was incomplete. All departments require specialty-specific clinical systems to efficiently collect and analyse these data and this survey proves their potential to form the basis for national electronic surveys in the future.

Effect of video display on the grading of diabetic retinopathy.

PURPOSE: Digital images are increasingly being used in ophthalmology. These may be viewed either on thin-film transistor (TFT) or on cathode-ray tube (CRT) displays. However, there is little data showing which is superior. In this study, we compared the performance of CRT and TFT displays for grading of both compressed and uncompressed images of diabetic retinopathy. METHODS: A total of 49 35 mm transparencies of diabetic retinopathy were scanned and compressed. The images comprised 17 with no retinopathy, eight with background, five with preproliferative, and 19 with proliferative retinopathy. Four levels of compression were used: 0, 70, 80, and 90%. A total of 196 randomised images were presented to two masked graders using both TFT and CRT displays under uniform lighting conditions, 2 months apart. The grade of retinopathy was assessed. Statistical analysis of grading accuracy was performed using receiver operator characteristic curves of sensitivity and specificity and the Stuart-Maxwell test for paired, nonparametric data. RESULTS: Both displays showed high sensitivity and specificity for the detection of any retinopathy. For the specific grade of retinopathy, the CRT performed slightly better with a sensitivity of 0.80 for uncompressed images, compared with 0.75 using the TFT. Compression reduced these sensitivities to 0.73 on the CRT and 0.63 on the TFT. Grading of uncompressed images magnified to four times their original size was more accurate on the TFT. CONCLUSIONS: Grading on both displays met sensitivity and specificity criteria proposed by Diabetes UK (formerly British Diabetic Association) for screening of diabetic retinopathy. The CRT generally performed slightly better than the TFT in relation to the detection of the specific grade of retinopathy.

Fluid flow in the anterior chamber of a human eye.

A simple model is presented to analyse fluid flow in the anterior chamber of a human eye. It is shown that under normal conditions such flow inevitably occurs. The flow, whose reduced Reynolds number is small, is viscosity dominated and is driven by buoyancy effects which are present because of the temperature difference between the front and back of the anterior chamber. In cases of severe eye trauma or as a result of certain diseases and medical conditions, particulate matter may be introduced into the anterior chamber. The motion and distribution of such particles is analysed and it is shown that the model is capable of predicting well-established and observed features that may be present in a traumatized eye such as hyphemas, keratic precipitates, hypopyons and Krukenberg spindles.

Effect of digital image compression on screening for diabetic retinopathy.

BACKGROUND/AIMS: Digital imaging is widely used for diabetic retinopathy screening. The storage and transmission of digital images can be facilitated by image compression. The authors aimed to assess the effect of image compression on the accuracy of grading diabetic retinopathy. METHODS: Forty nine 35 mm transparencies (17 with no retinopathy, eight with background, five with preproliferative, and 19 with proliferative retinopathy) were digitised and subjected to JPEG compression by 90%, 80%, 70%, and 0%. The 196 images were randomised and graded on a portable computer. Two masked graders assessed the images for grade of retinopathy and image quality (0-10). The sensitivity and specificity of retinopathy grading were calculated with a weighted kappa for grading agreement between levels of compression. RESULTS: The sensitivity of retinopathy grading was reduced by JPEG compression. At 90%, 80%, 70%, and 0% compression the sensitivities were 0.38, 0.50, 0.65, and 0.72, respectively; the specificity results were 1.00, 1.00, 0.83, and 0.84, respectively; and the weighted kappa scores were 0.60, 0.75, 0.77, and 0.84, respectively. The quality scores for 90%, 80%, 70%, 0% compression were 2.9 (SD 1.1, 95% CI; 2.7-3.2), 4.6 (SD 1.1, 95% CI; 3.0-5.6), 5.8 (SD1.5, 95% CI 5.0-6.6), 6.3 (SD1.4, 95% CI; 5.4-7.2) (p<0.01 for each intergroup comparison). CONCLUSION: The results demonstrate significant loss of sensitivity to the features of diabetic retinopathy with JPEG compression; this was compounded by the thin film transistor (TFT) screen. The authors found the quality of uncompressed images on TFT screens too poor to give grading sensitivities which reach current guidelines for diabetic retinopathy screening.

Local anaesthesia for 1221 vitreoretinal procedures.

BACKGROUND: Vitreoretinal (VR) surgery has been increasingly performed under local anaesthesia (LA) in this unit. The results of an audit monitoring this change are presented. METHODS: Data were collected on 1497 patients including type, volume, and position of the anaesthetic block, type of surgery, complications, and patient reactions. RESULTS: 1221/1479 (82%) patients had LA. They were older than those having general anaesthesia (GA) 63.5 years v 45.9 years; 146 (10.6%) blocks were intracone, 130 (10.6%) peribulbar, and 927 (75.9%) combined. Operations included 436 vitrectomies, 545 retinopexy with or without vitrectomy, and 238 buckling procedures. Some pain was felt by 9.4%, 8.8%, and 19.7% of patients during vitrectomy, retinopexy with or without vitrectomy, and buckling surgery respectively. CONCLUSION: Local anaesthesia for VR surgery is well tolerated by patients, being effective throughout longer and more stimulating ocular surgery.

Local anaesthesia for vitreoretinal surgery: an audit of patient and surgical experience.

PURPOSE: Local anaesthesia for vitreoretinal surgery is little used as these procedures are deemed to be too long and uncomfortable for patients to tolerate. In this unit anterior intraconal local anaesthesia is used for most routine surgery. We undertook an audit to ensure that surgical standards and patient acceptability were not compromised. METHODS: A prospective observational audit was performed. Audit data included: Grade of anaesthetist and surgeon; details of anaesthetic and operation; compliance of patient; operating conditions and pain scores. Anaesthesia was provided with a combined peribulbar and intraconal anaesthetic, using bicarbonate buffered lignocaine and bupivacaine 50:50 mixture. RESULTS: 135 (76%) had local anaesthesia alone, 13 (7%) had local anaesthesia with sedation and 29 (16%) had general anaesthesia. 96.4% of patients were compliant and 98.8% of operating conditions were good or excellent. The mean perioperative pain score was 0.1 (range of 0-1), 97% said they would choose local anaesthesia again. CONCLUSIONS: LA for vitreoretinal surgery is a useful and flexible method of anaesthesia, which has been shown to have excellent patient tolerance.

Ophthalmologists with conjunctivitis: are they fit to work?

PURPOSE: To establish current opinion as to whether ophthalmologists with conjunctivitis are fit to work. METHODS: One hundred and sixty ophthalmology units in the United Kingdom were sent a postal survey enquiring about work practices when an ophthalmologist contracts conjunctivitis. RESULTS: One hundred and five replies were received. Twenty-nine per cent of respondents said the ophthalmologist should stay off work while 7% said he or she should continue as usual. There was no concordance as to whether viral or bacterial conjunctivitis posed a greater problem. There is evidence that ophthalmologists have been implicated in the spread of epidemics of viral conjunctivitis but also reports of ophthalmologists who have continued to work with no reported spread of infection. CONCLUSION: In view of the lack of consensus the authors are unable to recommend evidence-based clinical guidelines, but would suggest that use of modern diagnostic laboratory techniques may help in making the decision as to whether to continue at work or not.

Pulfrich's phenomenon in unilateral cataract.

AIMS: To determine whether unilateral cataract causes a pathological Pulfrich's phenomenon. METHODS: 29 subjects with unilateral cataract and contralateral pseudophakia were assessed on their ability to perceive the Pulfrich phenomenon. Using a computer generated pendulum image, and graded neutral density filters, a series of forced choice trials were performed in which the subject was required to describe the direction of any apparent pendulum rotation. A pathological Pulfrich effect was said to occur when apparent rotation was perceived in the presence of a zero strength neutral density filter. The size of any pathological Pulfrich effect which was present was quantified by neutralising the perceived pendulum rotation with neutral density filters of varying strength placed before the better seeing eye. RESULTS: 20 out of 29 subjects were able to perceive apparent pendulum rotation when uniocular filtering was performed. In the group (n = 12) which was tested both before and after cataract extraction with intraocular lens implantation, a statistically significant pathological Pulfrich effect was demonstrated preoperatively, compared with a group of normal control subjects. This effect was abolished after cataract extraction (p = 0.009). The median size of the effect was equivalent to a 0.25 log unit neutral density filter over the non-cataractous eye. The subjects who were unable to perceive the Pulfrich phenomenon at all had a significantly greater difference in the visual acuity of each eye (p = 0.045) and significantly worse stereoacuity than those who were able to perceive the effect (p = 0.002). CONCLUSIONS: Unilateral cataract can cause a pathological Pulfrich phenomenon. This finding may explain why some patients with unilateral cataract complain of visual symptoms that are not easily accounted for in terms of visual acuity, contrast sensitivity, or stereoacuity.

The effect of prophylactic acetazolamide in patients undergoing extensive retinal detachment repair.

Encirclement of the eye as part of a retinal detachment repair is known to raise the post-operative intraocular pressure. We studied the effect of anticipating this pressure rise by giving perioperative acetazolamide to patients having vitrectomy and encirclement procedures. Two groups (9 with acetazolamide and 14 without) were matched for biographic variables, type of detachment and operation variables. The group given acetazolamide had lower day 1 post-operative intraocular pressures (mean 22.11 mmHg vs 36.36 mmHg, p = 0.002) and were able to go home sooner (mean 1.56 days vs 3.29 days, p = 0.001). No adverse effects of short-term acetazolamide use were noted in this study. We conclude that patients having extensive scleral buckling procedures should all receive prophylactic acetazolamide unless it is specifically contraindicated.

Survey of colour contrast sensitivity in non-ophthalmic users of blue-green wavelength argon lasers.

BACKGROUND: Previous studies have shown that ophthalmologists using blue-green argon laser may suffer subtle defects in their colour vision. A reduction in colour contrast sensitivity in the tritan colour confusion axis, an early manifestation of blue cone photoreceptor injury by the high energy photons of the laser, has been demonstrated and has prompted a reappraisal of laser safety in ophthalmology. Argon laser is also frequently used in scientific research, often at higher power output and for longer periods than is used in clinical practice. The scientists operating these lasers are at risk of developing similar phototoxic retinal injury. METHODS: The colour contrast sensitivity of 18 scientists who regularly use short wavelength argon laser was investigated. RESULTS: Eye protection was infrequently used and individuals had been subjected to between 580 and 7200 hours of cumulative laser exposure during the course of their research. CONCLUSION: The use of blue-green argon laser by the scientists investigated was not associated with a significant reduction in colour contrast sensitivity.

A comparison of the efficacy of Holmium laser sclerostomy ab externo versus trabeculectomy in the treatment of glaucoma.

We compared 15 patients who had undergone Holmium laser sclerostomy ab externo with 15 who had had trabeculectomy. In the short term, laser sclerostomy led to adequate control of intraocular pressure, but in the longer term it compared unfavourably with trabeculectomy in terms of efficacy, complications and reoperation rate. At 1 year follow-up, 8 patients in the laser group had had to undergo a second operation compared with none in the control trabeculectomy group, and 7 were still on glaucoma medication compared with 2 in the control group. Iris prolapse into the internal sclerostomy ostium within 2 months accounted for most failures, and was only partially amenable to Nd:YAG peripheral iridectomy. This common complication seems to be related to anterior chamber depth. There also appears to be a tendency for blockage of the sclerostomy with cellular or fibrinous debris. Recent literature is reviewed and modifying strategies discussed.