Improving precision for detecting change in the shape of the cornea in patients with keratoconus

To investigate a method for precision analysis to discriminate true corneal change from measurement imprecision in keratoconus (KC). Thirty patients with KC and 30 healthy controls were included. Coefficients of repeatability and limits of agreement (LOA) were compared using multiple measurements for inter-observer and inter-device agreement with the Pentacam HR, Orbscan IIz, and Tomey Casia SS-1000. Correlation of repeated measurements was evaluated using a linear mixed effect model (also called random effect model). A formula was derived for the theoretical expected change in precision and compared with measured change. Correlation between measurements from the same eye was small (R = 0.13). The 99.73% LOA (3 SD) of the mean of three measurements, provided better precision than 95% LOA (2 SD) of single cut-off values as expected from statistical theory for uncorrelated measurements for evidence of a significant change in corneal shape in patients with keratoconus. This enabled the determination of cut-off values for the detection of true change in corneal shape. The mean of three repeated measurements will provide better precision when there is minimal correlation. Three (rather than two) standard deviations provides a precise estimate of the LOA within or between observers and can be used as a reliable measure for identifying stage-independent corneal shape changes (progression) in keratoconus

Microdroplet and spatter contamination during phacoemulsification cataract surgery in the era ofCOVID-19

IMPORTANCE: Determine phacoemulsification cataract surgery risk in a Covid-19 era. BACKGROUND: SARS-CoV-2 (Covid-19) transmission via microdroplet and aerosol-generating procedures presents risk to medical professionals. As the most common elective surgical procedure performed globally; determining contamination risk from phacoemulsification cataract surgery may guide personal protection equipment use. DESIGN: Pilot study involving phacoemulsification cataract surgery on enucleated porcine eyes by experienced ophthalmologists in an ophthalmic operating theatre. PARTICIPANTS: Two ophthalmic surgical teams. METHODS: Standardized phacoemulsification of porcine eyes by two ophthalmologists accompanied by an assistant. Fluorescein incorporated into phacoemulsification irrigation fluid identifying microdroplets and spatter. Contamination documented using a single-lens reflex camera with a 532 nm narrow bandpass (fluorescein) filter, in-conjunction with a wide-field blue light and flat horizontal laser beam (wavelength 532 nm). Quantitative image analysis using Image-J software. MAIN OUTCOME MEASURES: Microdroplet and spatter contamination from cataract phacoemulsification. RESULTS: With phacoemulsification instruments fully within the eye, spatter contamination was limited to 16 cm below the neckline in surgeon 1 and > 5.5 cm below the neckline of surgeon 2. A small tear in the phacoemulsification irrigation sleeve, presented a worse-case scenario the greatest spatter. No contamination above the surgeons' neckline nor contamination of assistant occurred. CONCLUSIONS AND RELEVANCE: Cataract phacoemulsification generates microdroplets and spatter. Until further studies on SARS-CoV-2 transmission via microdroplets or aerosolisation of ocular fluid are reported, this pilot study only supports standard personal protective equipment

Visual function and patient satisfaction after macular hole surgery

Purpose. Over recent years success in macular hole surgery has increased in terms of anatomical closure. However, debate still continues on the benefit to the patient in terms of visual outcome. We designed a prospective study to investigate the outcome of full thickness macular hole (FTMH) surgery in terms of anatomical closure, visual outcome, incidence of complications and patient satisfaction. Methods. Thirty eyes of 30 consecutive patients with FTMH were prospectively studied (stage 2 = 2; stage 3 = 23; stage 4 = 5). All cases had surgery involving vitrectomy, injection of an autologous platelet aggregate over the hole and gas tamponade. At 3 months postoperatively all cases were assessed for closure of the FTMH, Snellen acuity and the incidence of complications. At this stage all patients completed a patient satisfaction questionnaire. Results. Anatomical closure of the hole was achieved in 83% of eases (25/30). Visual improvement of 2 Snellen lines or more occurred in 50% of cases (15/30). A vision of 6/12 or better was achieved in 27% of cases (8/30). A post-operative lens opacity was present in 46% (13/28) of phakic patients and a temporal, peripheral wedge-shaped field defect occurred in 17% (5/30) of cases. In this study, 53%, 70%, 57% and 67% of patients gave a positive response to specific questions about satisfaction with near, intermediate and distance vision and overall visual function respectively. Conclusions. Although the anatomical success of FTMH surgery is high the functional outcome in terms of Snellen acuity is less rewarding. Analysis of patient satisfaction suggests that the arbitrary visual outcome measures presently used may underestimate the functional benefit to the patient. Improved objective measures of visual outcome are required to assess the benefit of surgery in these cases.link_to_subscribed_fulltex