William Wykes

The role of haemorrhage and exudate detection in automated grading of diabetic retinopathy

Background/aims Automated grading has the potential to improve the efficiency of diabetic retinopathy screening services. While disease/no disease grading can be performed using only microaneurysm detection and image-quality assessment, automated recognition of other types of lesions may be advantageous. This study investigated whether inclusion of automated recognition of exudates and haemorrhages improves the detection of observable/referable diabetic retinopathy. Methods Images from 1253 patients with observable/referable retinopathy and 6333 patients with non-referable retinopathy were obtained from three grading centres. All images were reference-graded, and automated disease/no disease assessments were made based on microaneurysm detection and combined microaneurysm, exudate and haemorrhage detection. Results Introduction of algorithms for exudates and haemorrhages resulted in a statistically significant increase in the sensitivity for detection of observable/referable retinopathy from 94.9% (95% CI 93.5 to 96.0) to 96.6% (95.4 to 97.4) without affecting manual grading workload. Conclusion Automated detection of exudates and haemorrhages improved the detection of observable/referable retinopathy.

Costs and consequences of automated algorithms versus manual grading for the detection of referable diabetic retinopathy.

Aims To assess the cost-effectiveness of an improved automated grading algorithm for diabetic retinopathy against a previously described algorithm, and in comparison with manual grading. Methods Efficacy of the alternative algorithms was assessed using a reference graded set of images from three screening centres in Scotland (1253 cases with observable/referable retinopathy and 6333 individuals with mild or no retinopathy). Screening outcomes and grading and diagnosis costs were modelled for a cohort of 180 000 people, with prevalence of referable retinopathy at 4%. Algorithm (b), which combines image quality assessment with detection algorithms for microaneurysms (MA), blot haemorrhages and exudates, was compared with a simpler algorithm (a) (using image quality assessment and MA/dot haemorrhage (DH) detection), and the current practice of manual grading. Results Compared with algorithm (a), algorithm (b) would identify an additional 113 cases of referable retinopathy for an incremental cost of £68 per additional case. Compared with manual grading, automated grading would be expected to identify between 54 and 123 fewer referable cases, for a grading cost saving between £3834 and £1727 per case missed. Extrapolation modelling over a 20-year time horizon suggests manual grading would cost between £25 676 and £267 115 per additional quality adjusted life year gained. Conclusions Algorithm (b) is more cost-effective than the algorithm based on quality assessment and MA/DH detection. With respect to the value of introducing automated detection systems into screening programmes, automated grading operates within the recommended national standards in Scotland and is likely to be considered a cost-effective alternative to manual disease/no disease grading.

The efficacy of 5% povidone-iodine for 3 minutes prior to cataract surgery.

Purpose To evaluate the efficacy of 3 minutes of 5% povidone-iodine for skin and conjunctival antisepsis prior to cataract surgery as recommended by the European Society of Cataract and Refractive Surgeons. Methods A prospective controlled study of 54 patients undergoing unilateral cataract surgery by phacoemulsification was undertaken. The eye undergoing surgery was prepared with 5% povidone-iodine for 3 minutes. The other eye served as control. Swabs were taken from both eyes prior to application of 5% povidone-iodine and 3 minutes after. Proportion of culture-positive swabs, mean number of species, and growth of isolates on culture were compared at different times and between the two groups. Results Coagulase-negative Staphylococcus (CoNS) was the main species isolated from culture-positive swabs. Use of 5% povidone-iodine for 3 minutes resulted in a statistically significant reduction in proportion of culture-positive swabs (87% vs 30%, p<0.001), mean number of species (0.96±0.47 vs 0.30±0.46, p<0.001), and growth of CoNS (heavy: 30% vs 0%, moderate: 23% vs 6%, light: 47% vs 94%, p=0.004). No such changes were observed in the control group. Conclusions Use of 5% povidone-iodine for 3 minutes prior to cataract surgery achieves a significant reduction in organisms such as CoNS from lid and conjunctival flora.

Incidence and visual outcome of acute endophthalmitis after cataract surgery—the experience of an eye department in Scotland

Aim: Endophthalmitis remains one of the most dreaded complications of modern cataract surgery. Its incidence in the UK has been estimated but accurate published data on the incidence at a regional level are scarce. This audit examines the incidence and visual outcome of endophthalmitis from a single eye department in Scotland (UK) over a 7-year period. Findings are compared with those from other series. Methods: A retrospective consecutive audit of all cases of acute endophthalmitis treated between 1 January 2000 and 31 December 2006 at the Southern General Hospital in Glasgow (Scotland, UK) was undertaken. Details of each case (presentation, treatment and outcome of endophthalmitis) were recorded. Cross-tabulations were performed to identify prognostic factors of visual outcome. Results: Twenty-five patients were treated for endophthalmitis over the audit period. The incidence of endophthalmitis was 0.20% (95% CI 0.10 to 0.30%). There were 12 (48%) culture-positive cases with coagulase-negative staphylococcus accounting for 58%. After treatment, 16 patients (64%) achieved driving-standard vision or better. Poor vision at presentation and streptococcal endophthalmitis were associated with poor visual outcome. Conclusion: The incidence of endophthalmitis in this series is comparable to larger studies, suggesting that accepted benchmarks, despite being estimates, reflect UK practice. Visual outcome, with treatment, can be favourable in a significant proportion of patients.

A comparison of visual performance between a rigid PMMA and a foldable acrylic intraocular lens.

Purpose To examine post-operative visual outcomes when using micro-incision surgery and a three-piece, foldable acrylic intraocular lens (IOL) and when using small-incision surgery and a one-piece, rigid polymethyl-methacrylate (PMMA) IOL.Methods Phacoemulsification and IOL implantation was conducted by one surgeon on 86 subjects (aged 50-89 years) with cataracts. Of these subjects, 67 completed the study. Subjects were implanted either with a foldable IOL (n = 38) or a rigid IOL (n = 29). Best corrected Snellen visual acuity and contrast sensitivity (2-28 cycles/degree) were measured approximately 2 months post-operatively. Comparisons were made between the pseudophakic groups and an additional group of 28 age-matched, normal subjects (aged 58-81 years). Non-parametric (Kruskal-Wallis and Mann-Whitney u) as well as parametric (ANOVA and Pearson) statistics tests were used in the analysis of results.Results All pseudophakes had corrected visual acuity of 6/9 or better. There were no significant differences in visual acuity (Kruskal-Wallis, p = 0.61) or contrast sensitivity (ANOVA, p = 0.33) between the three groups. The mean residual refractive error of the foldable IOL group was hypermetropic in comparison with the rigid IOL group but not significant at the 99% level of probability (Mann-Whitney u, p = 0.02). There was no significant difference in astigmatism between the groups.Conclusions Implanting a foldable acrylic IOL gave no post-operative benefit in visual acuity and contrast sensitivity to pseudophakes over a less expensive rigid PMMA IOL, within this post-operative period. This study did not provide a comparison between the two lenses regarding post-operative complications, in particular the important long-term complication of posterior capsular opacification (PCO). Until and if any particular advantage of a given IOL in reduced incidence of PCO is confirmed, it appears more economical to implant the conventional rigid PMMA IOL using small-incision surgery.

A comparison of colour Doppler imaging of orbital vessels and other methods of blood flow assessment

Abstract• Background: Comparison of the haemodynamic measurements obtained by colour Doppler imaging and other methods of ocular blood flow measurements was desired. • Methods: The blood velocity findings from colour Doppler imaging of patients with central retinal vein occlusion were compared to the results of fluorescein video-angiography, continuous tonography and ophthalmodynamometry. • Results: Patients with low or undetectable blood velocities in the central retinal vein had longer retinal dye transit times on fluorescein video-angiography. Tonography showed a positive correlation with the velocities in the ophthalmic artery, but ophthalmo-dynamometry showed a negative correlation with these velocities. • Conclusion: The relationships between the blood velocities in orbital vessels and other blood flow measurements emphasise that there is a complex interaction of the blood flow parameters. Care must therefore be taken when interpreting the results of studies.

Isolated superior ophthalmic vein thrombosis with orbital congestion: a variant of idiopathic orbital inflammatory disease?

Isolated superior ophthalmic vein thrombosis with orbital congestion: a variant of idiopathic orbital inflammatory disease?

Economic costs of cataract surgery using a rigid and a foldable intraocular lens

Optimal delivery of healthcare requires consideration of various costs. A foldable intraocular lens (IOL) is more expensive than an equivalent rigid IOL. However, surgical and post‐operative costs may make a foldable IOL economically preferable. We compared the economic costs of cataract surgery plus implantation of a foldable IOL with implantation of a rigid IOL. Prospective audit of the clinical records of 82 pseudophakes; 39 implanted with a rigid IOL and 43 implanted with a foldable IOL by one surgeon. Average follow‐up periods were 25±7 months and 23±5 months respectively. There was no difference between the two groups for the follow‐up period (P=0.55), number of post‐operative complications (P=0.25) or cost of post‐operative visits (P=0.83). The cost of single‐use theatre equipment was greater for the rigid‐IOL group (P=0.0001). The total identified cost per patient was greater for the foldable‐IOL group (P=0.0001). Despite possible technical advantages, implantation of the foldable IOL did not provide an economic benefit, either in the initial cost or in the costs of post‐operative care. Over the 2‐year period, implanting with the rigid IOL cost, on average, £57 less per patient. Despite this economic difference, a cost‐benefit analysis is required, since other factors may be more important.

Herpes zoster ophthalmicus

A 65 year old woman attends your practice with a two day history of a vesicular rash around her right eye. She also reports a general feeling of fatigue and malaise and has been slightly feverish over the past week. She had noticed a pain around her right eye even before the skin eruption began. ### What is it and why has she got it? After an attack of chickenpox the virus (varicella zoster) remains dormant in the body. This virus is kept in check by the immune system. However, in 20% of people the virus is reactivated, resulting in a localised painful rash with blisters (shingles). The commonest cause is a weakening of the immune system with age; most patients are aged over 50 years. Other causes include stress, fatigue, and a weakening of the immune system from other illnesses or from medical treatment (such as chemotherapy or immunosuppression). When the eruption involves the area around the eye (the ophthalmic or first division of the trigeminal nerve), this is called herpes zoster ophthalmicus, irrespective of whether the actual eye itself is involved. Ophthalmic herpes zoster accounts for 10-25% of all cases of shingles. ### Have I got the right diagnosis? The main differential diagnosis is herpes simplex infection. In herpes simplex the patients are usually young, and the rash will not follow a dermatome, nor will …

Subclinical operating microscope retinopathy: The use of static perimetry in its detection

Focal retinal pathology and dysfunction as a sequel to manifest damage due to operating microscope illumination is well recognised. We wished to determine whether retinal dysfunction could be identified in the absence of clinically visible lesions. We therefore have conducted a prospective controlled study on 36 patients undergoing cataract surgery and 27 control subjects. A Wild M690 zoom operating microscope was used for each procedure. No filters were used. The Humphrey visual field equipment was employed to determine threshold retinal sensitivity at predetermined loci above and below fixation in both groups. No clinically visible retinal lesions were seen in any patient. However, post-operative investigation revealed a statistically significant depression in retinal sensitivity at points most exposed to operating microscope illumination (p<0.05). This was most noticeable following longer total operating times and in patients with the longest time intervals between lens extraction and completion of the procedure. It is concluded that operating microscope position and centration, and the position of the eye, should be adjusted to place the image of the illuminating element away from the foveola. Also retinal illumination should be kept to a minimum, particularly after an intraocular lens has been implanted.