Comparison of droplet spread in standard and laminar flow operating theatres: SPRAY study group.

BACKGROUND: Reducing COVID-19 transmission relies on controlling droplet and aerosol spread. Fluorescein staining reveals microscopic droplets. AIM: To compare the droplet spread in non-laminar and laminar air flow operating theatres. METHODS: A 'cough-generator' was fixed to a theatre trolley at 45°. Fluorescein-stained 'secretions' were projected on to a series of calibrated targets. These were photographed under UV light and 'source detection' software measured droplet splatter size and distance. FINDINGS: The smallest droplet detected was ∼120 µm and the largest ∼24,000 µm. An average of 25,862 spots was detected in the non-laminar theatre, compared with 11,430 in the laminar theatre (56% reduction). The laminar air flow mainly affected the smaller droplets (<1000 µm). The surface area covered with droplets was: 6% at 50 cm, 1% at 2 m, and 0.5% at 3 m in the non-laminar air flow; and 3%, 0.5%, and 0.2% in the laminar air flow, respectively. CONCLUSION: Accurate mapping of droplet spread in clinical environments is possible using fluorescein staining and image analysis. The laminar air flow affected the smaller droplets but had limited effect on larger droplets in our 'aerosol-generating procedure' cough model. Our results indicate that the laminar air flow theatre requires similar post-surgery cleaning to the non-laminar, and staff should consider full personal protective equipment for medium- and high-risk patients.

An analysis of the CFH Y402H genotype in AMD patients and controls from the UK, and response to PDT treatment.

AIM: Mutation in the complement factor H (CFH) gene is an important risk factor for age-related macular degeneration (AMD). In this study, we identified the strength of the CFH Y402H gene variant association in a UK AMD cohort and tested the hypothesis that this variant may influence the biological response of choroidal neovascularisation (CNV) following photodynamic therapy (PDT) for CNV. METHODS: A total of 557 cases with AMD and 551 normal controls were genotyped for the CFH Y402H (1277 C/T) variant using the 5' nuclease TaqMan assay for allelic discrimination. The CFH gene association for AMD, for the different CNV subtypes and for patients needing PDT was estimated. Twenty-seven PDT-treated patients were followed up for 15 months with ETDRS-derived vision, clinical examination, and fundus angiography. Individuals with different CFH genotypes were then analysed for any association with visual change following PDT. RESULTS: The risk association for AMD with the CFH CC genotype (odd ratio (OR)=3.62, Pc<0.0001) was similar to that reported in other Caucasian cohorts. The magnitude and strength of this association was stronger in AREDS stages 2-4 (ORs=4.48, 2.69, and 5.17). ORs for the risk of predominantly classic CNV were significantly raised for both the CC (OR=17.87, P<0.0001) and CT (OR=9.06, P=0.0002) genotypes. The number of patients carrying the high-risk C allele was 70.4% in those requiring PDT as compared to 52.3% in the non-PDT group (OR=2.16, P=0.011), and presence of the CC genotype significantly increased the risk of PDT (OR=5.48, P=0.015). The degree of visual loss following PDT was significantly higher in the CFH CC genotype group (P=0.038); 50% of CC cases (n=13) and 45% of the CT cases (n=12) lost 15 or more ETDRS letters at final follow-up. CONCLUSION: In this UK cohort of AMD patients, the CFH Y402H variant was significantly enriched in patients with predominantly classic CNV. Patients homozygous for the CFH Y402H genotype seem to have worse visual acuity after PDT.

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.