Maged Habib

REVIEW - A reference data set for retinal vessel profiles

This paper describes REVIEW, a new retinal vessel reference dataset. This dataset includes 16 images with 193 vessel segments, demonstrating a variety of pathologies and vessel types. The vessel edges are marked by three observers using a special drawing tool. The paper also describes the algorithm used to process these segments to produce vessel profiles, against which vessel width measurement algorithms can be assessed. Recommendations are given for use of the dataset in performance assessment. REVIEW can be downloaded from http://ReviewDB.lincoln.ac.uk.

Clinical efficacy of intravitreal aflibercept versus panretinal photocoagulation for best corrected visual acuity in patients with proliferative diabetic retinopathy at 52 weeks (CLARITY): a multicentre, single-blinded, randomised, controlled, phase 2b, non-inferiority trial

BACKGROUND Proliferative diabetic retinopathy is the most common cause of severe sight impairment in people with diabetes. Proliferative diabetic retinopathy has been managed by panretinal laser photocoagulation (PRP) for the past 40 years. We report the 1 year safety and efficacy of intravitreal aflibercept. METHODS In this phase 2b, single-blind, non-inferiority trial (CLARITY), adults (aged ≥18 years) with type 1 or 2 diabetes and previously untreated or post-laser treated active proliferative diabetic retinopathy were recruited from 22 UK ophthalmic centres. Patients were randomly assigned (1:1) to repeated intravitreal aflibercept (2 mg/0·05 mL at baseline, 4 weeks, and 8 weeks, and from week 12 patients were reviewed every 4 weeks and aflibercept injections were given as needed) or PRP standard care (single spot or mutlispot laser at baseline, fractionated fortnightly thereafter, and from week 12 patients were assessed every 8 weeks and treated with PRP as needed) for 52 weeks. Randomisation was by minimisation with a web-based computer generated system. Primary outcome assessors were masked optometrists. The treating ophthalmologists and participants were not masked. The primary outcome was defined as a change in best-corrected visual acuity at 52 weeks with a linear mixed-effect model that estimated adjusted treatment effects at both 12 weeks and 52 weeks, having excluded fluctuations in best corrected visual acuity owing to vitreous haemorrhage. This modified intention-to-treat analysis was reapplied to the per protocol participants. The non-inferiority margin was prespecified as -5 Early Treatment Diabetic Retinopathy Study letters. Safety was assessed in all participants. This trial is registered with ISRCTN registry, number 32207582. FINDINGS We recruited 232 participants (116 per group) between Aug 22, 2014 and Nov 30, 2015. 221 participants (112 in aflibercept group, 109 in PRP group) contributed to the modified intention-to-treat model, and 210 participants (104 in aflibercept group and 106 in PRP group) within per protocol. Aflibercept was non-inferior and superior to PRP in both the modified intention-to-treat population (mean best corrected visual acuity difference 3·9 letters [95% CI 2·3-5·6], p<0·0001) and the per-protocol population (4·0 letters [2·4-5·7], p<0·0001). There were no safety concerns. The 95% CI adjusted difference between groups was more than the prespecified acceptable margin of -5 letters at both 12 weeks and 52 weeks. INTERPRETATION Patients with proliferative diabetic retinopathy who were treated with intravitreal aflibercept had an improved outcome at 1 year compared with those treated with PRP standard care. FUNDING The Efficacy and Mechanism Evaluation Programme, a Medical Research Council and National Institute for Health Research partnership.

Automated analysis of retinal vascular network connectivity

This paper describes an algorithm that forms a retinal vessel graph by analysing the potential connectivity of segmented retinal vessels. Self organizing feature maps (SOFMs) are used to model implicit cost functions for the junction geometry. The algorithm uses these cost functions to resolve the configuration of local sets of segment ends, thus determining the network connectivity. The system includes specialized algorithms to handle overlapping vessels. The algorithm is tested on junctions drawn from the public-domain DRIVE database.

Central scotoma associated with intraocular silicone oil tamponade develops before oil removal

BackgroundUnexplained sudden visual loss after removal of silicone oil from the eye has recently been described. We report the occurrence and features of unexplained central scotoma developing with silicone oil in situ in the vitreous cavity.MethodsA retrospective case series of five patients (from two centres) who reported a central scotoma commencing during silicone oil tamponade was studied. All patients had vitrectomy for macula-on retinal detachment, with ultra-purified silicone oil tamponade (four out of five had giant retinal tear). Investigations included visual acuity, intraocular pressure, optical coherence tomography, fluorescein angiography, visual fields and electrophysiology.ResultsAll patients reported a central scotoma that appeared during oil tamponade. Visual acuity fell by a mean of 0.93 LogMAR units after onset of the scotoma. After cataract extraction and oil removal, vision remained reduced by a mean of 0.8 units. The mean duration of oil in the eye was 2.7 months when the scotoma was noted by the patient. Investigations were performed after removal of oil. Fluorescein angiography (FFA) was performed in two cases and optical coherence tomography (OCT) in five patients. No abnormality was demonstrated. Electrophysiology was performed in five patients with pattern electroretinography suggestive of macular dysfunction in four patients.ConclusionThis is the first case series describing central scotoma associated with silicone oil in situ. Electrophysiology indicated macular dysfunction in most cases. We suggest that early removal of oil in cases with good visual potential should be considered to avoid this sight-threatening complication.

The combination of intravitreal triamcinolone and phacoemulsification surgery in patients with diabeticfoveal oedema and cataract

BackgroundThe management of diabetic patients with refractory macular oedema or patients with no adequate pre-operative view to administer laser treatment provide a challenge to the ophthalmologist. We wished to assess the use, safety and effect of intravitreal triamcinolone injection at the time of cataract surgery in patients with diabetic foveal oedema and sight limiting lens opacities.MethodThis was a longitudinal non-randomised prospective pilot study in 18 eyes (12 patients). All patients had visually significant lens opacities and either persistent diabetic foveal oedema unresponsive to laser treatment-group A, or foveal oedema with no adequate pre-operative view for laser treatment- group B. The cataract surgery was carried out under full aseptic technique using a self-sealing temporal incision and a foldable acrylic lens. Intravitreal triamcinolone was given infratemporally pars plana at the completion of the cataract surgery. The patients were reviewed at day 5, 2 weeks, 2 months and then every 3 months as required. The Wilcoxin matched-pairs test was used to assess the significance of the improvement in visual acuity at 2 months.ResultsTwelve patients with a total of 18 eyes were included in the study. There were 10 patients (15 eyes) in group A and 3 patients (3 eyes) in group B. Preoperatively 16 of the 18 eyes had a visual acuity of 6/24 or worse. Postoperatively 83% of patients had completely dry foveae at 2 weeks. Best-corrected visual acuities at two months review ranged from 6/6 to CF with 9 eyes (50%) achieving 6/12 or better (7 eyes (47%) in group A and 2 eyes (67%) in group B). Three eyes had no recorded improvement in visual acuity, but no eyes had deterioration in acuity. The improvement in visual acuity was significant at p = 0.001. There were no significant sight threatening complications.ConclusionIntravitreal triamcinolone has been shown to lead to an improvement in macular oedema and visual improvement in diabetic patients not undergoing cataract surgery but has not, to our knowledge, been previously used in a study like this one.We suggest that intravitreal injection at the time of cataract surgery could be carried out safely with encouraging visual outcomes in patients with diabetic foveal oedema and cataract.

An automated retinal image quality grading algorithm

This paper introduces an algorithm for the automated assessment of retinal fundus image quality grade. Retinal image quality grading assesses whether the quality of the image is sufficient to allow diagnostic procedures to be applied. Automated quality analysis is an important preprocessing step in algorithmic diagnosis, as it is necessary to ensure that images are sufficiently clear to allow pathologies to be visible. The algorithm is based on standard recommendations for quality analysis by human screeners, examining the clarity of retinal vessels within the macula region. An evaluation against a reference standard data-set is given; it is shown that the algorithms performance correlates closely with that of clinicians manually grading image quality.

Comparison of retinal breaks observed during 23 gauge transconjunctival vitrectomy versus conventional 20 gauge surgery for proliferative diabetic retinopathy.

Background To assess the rate and type of retinal break formation in patients undergoing 23 gauge transconjunctival vitrectomy surgery for complications of proliferative diabetic retinopathy compared with 20 gauge vitrectomy surgery. Methods Retrospective case notes review of two consecutive series of patients who had primary pars plana vitrectomy for complications of proliferative diabetic retinopathy by a single surgeon. The control group had standard 20 gauge vitrectomy surgery whilst the second group had 23 gauge transconjunctival vitrectomy surgery. Results Eighty-five eyes were included in the 20 gauge group and 85 eyes in the 23 gauge group. The groups were well matched for surgical complexity and indications for surgery, as well as a variety of other preoperative variables. There was a significant reduction in the incidence of peripheral sclerotomy-related retinal breaks and lesions suspicious for breaks (4/85 [5%] 23 gauge versus 14/85 [16%] 20 gauge, P = 0.02) and posterior retinal breaks (3/85 [4%] 23 gauge versus 12/85 [14%] 20 gauge, P = 0.03). Six eyes (7%) in total had definite new retinal breaks of any type detected in the 23 gauge group compared with 16 (18.8%) in the 20 gauge group (P = 0.04). One patient in each group experienced a retinal detachment postoperatively related in both cases to a posterior retinal break associated with recurrent traction. Conclusion In this series of patients, 23 gauge transconjunctival vitrectomy surgery was associated with a lower rate of retinal break formation than 20 gauge vitrectomy for proliferative diabetic retinopathy.

The role of case mix in the relation of volume and outcome in phacoemulsification

Background/aim: The authors previously demonstrated a decrease in complication rate with an increase in volume of cases performed by a surgeon. All studies of volume and outcome are potentially hampered by the issue of case mix, in that some lower volume surgeons may in fact do fewer cases because they have more complex patients. This study was designed to assess the influence of case mix on the volume-outcome relation in phacoemulsification surgery that had previously been demonstrated. Methods: This study took place wholly in Sunderland Eye Infirmary. 667 cases from between 1996 and 2001 were randomly selected from the operative lists of the six surgeons involved in a previous study. The case complexity was assessed using a potential difficulty score (PDS) devised from preoperative data predictive of potential surgical difficulty. The PDS was validated by a retrospective analysis of a sample of 100 cases. Results: 528 complete sets of notes were retrieved. The overall PDS scores ranged from 1 to 6. There was a difference between the proportions of patients with each PDS value (p = 0.015) in the two groups, which suggested that the low volume surgeons were doing potentially more difficult cases. The median PDS for each volume group were the same ( = 1.0). Retrospective validation analysis of the PDS score revealed higher mean and median values in complicated cases compared to uncomplicated cases. Conclusion: This follow up study re-emphasises the importance of case mix adjustment in comparative assessment of healthcare quality. These results may explain in part the trend previously demonstrated of lower complication rates for higher volume surgeons.

Opposite clear corneal incisions on the steep meridian in phacoemulsification: Early effects on the cornea

Purpose: To evaluate the effect of on‐axis opposite clear corneal incisions (OCCIs) in phacoemulsification on reducing preoperative corneal astigmatism and to predict the astigmatic outcome of the incisions. Setting: Royal Eye Infirmary, Dorset County Hospital, and Winterbourne Hospital, Dorchester, Dorset, and the Department of Ophthalmology, East Somerset Hospital, Yeovil, Somerset, United Kingdom. Methods: This prospective study included all patients (n = 103) who had on‐axis OCCIs as a part of routine phacoemulsification with foldable intraocular lens (IOL) implantation performed by 1 surgeon during 2000. Keratometry was done 6 to 8 weeks postoperatively. The differences in the preoperative and postoperative corneal astigmatism and corneal spherical equivalent (SE) were recorded. Surgically induced astigmatism (SIA) was calculated using vector analysis. Results: The mean reduction in corneal astigmatism was 0.50 diopter (D) (P<.001). The mean SIA was 1.57 D (95% confidence interval [CI], 1.42 to 1.71). There was a weak association between the SIA and the patients age and axis of preoperative astigmatism. The mean change in SE was +0.02 D (95% CI, −0.08 to +0.12). Conclusions: Results indicate that on‐axis OCCIs are a reliable and practical way of reducing preexisting corneal astigmatism. The change in SE was negligible and thus can be ignored during biometry.

The relation of volume with outcome in phacoemulsification surgery

Background/aims: High case volume has been associated with better health outcomes for a variety of procedures and conditions including coronary angioplasty, carotid endarterectomy, colorectal surgery, and various types of cancer surgery. The association of volume and outcome has important implications for patient safety and healthcare delivery planning. The relation between surgical volume and outcome has not, as far as is known, been looked at for phacoemulsification alone. Methods: All cataract surgery performed from 1996 to 2001 by six consultant surgeons was reviewed. Using theatre logbooks and cross checking with the hospital database, the total number of phacoemulsification procedures performed per surgeon per year was calculated. The total number of operations in which it was judged that significant intraoperative complications occurred was also counted. Results: When the data were pooled for all the surgeons there was evidence that complication rate decreased over time (Spearman’s rho = −0.319, p = 0.058). If the data were pooled from all the years and all the surgeons then there was strong evidence of a decrease in complication rate with an increase in the number of cases (Spearman’s rho = −0.63, p<0.01). Conclusions: This study is the first to describe a possible relation between volume of surgery and the outcome (as measured by complication rates) for phacoemulsification. There are however some caveats in that the issue of case mix was not addressed and that the results are from a single unit and may not necessarily be generalisable