This study reviews performance criteria adequate to validate simulation models through the comparison of two quantitative data sets, concerning historical and simulated data. The criteria reviewed were organized according to its characteristics into the groups: error‐based measures, information theory measures, information criteria, parametric tests, non‐parametric tests, distance‐based measures and combined measures. Each criterion is reviewed through its mathematic definition, its applications in literature and the identification of its advantages and drawbacks. The features assessed by each criterion are identified and discussed. This study provides a concise outline over the criteria reviewed, which can be used as a guide to help developers of simulation models into the decision on the most appropriate criteria to validate their models.

Analysis of refractive outcomes, using biometry data collected with a new biometer (Pentacam-AXL, OCULUS, Germany) and a reference biometer (Lenstar LS 900, HAAG-STREIT AG, Switzerland), in order to assess differences in the predicted and actual refraction using different formulas. Prospective, institutional study, in which intraocular lens (IOL) calculation was performed using the Haigis, SRK/T and Hoffer Q formulas with the two systems in patients undergoing cataract surgery between November 2016 and August 2017. Four to 6 weeks after surgery, the spherical equivalent (SE) was derived from objective refraction. Mean prediction error (PE), mean absolute error (MAE) and the median absolute error (MedAE) were calculated. The percentage of eyes within ± 0.25, ± 0.50, ± 1.00, and ± 2.00 D of MAE was determined. 104 eyes from 76 patients, 35 males (46.1%), underwent uneventful phacoemulsification with IOL implantation. Mean SE after surgery was − 0.29 ± 0.46 D. Mean prediction error (PE) using the SRK/T, Haigis and Hoffer Q formulas with the Lenstar was significantly different (p > 0.0001) from PE calculated with the Pentacam in all three formulas. Percentage of eyes within ± 0.25 D MAE were larger with the Lenstar device, using all three formulas. The difference between the actual refractive error and the predicted refractive error is consistently lower when using Lenstar. The Pentacam-AXL user should be alert to the critical necessity of constant optimization in order to obtain optimal refractive results.

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Objective To describe how a fixed regimen of intravitreal injections (IVI) was helpful to continue activity during the COVID-19 outbreak and lockdown and to address basic conditions to resume activity. Methods A fixed regimen of IVI was conceived to significantly reduce the number of visits while keeping a number of injections related to the best outcomes. We retrospectively collected data of surgeries performed in 2019 and in the first seven months of 2020 and from OCTs in the first semester of 2020. Results IVI per month, from January to July 2020, were 304, 291, 256, 204, 276, 297 and 322, respectively. Phacoemulsification surgeries in the same period were 397, 408, 171, 0, 304, 391 and 389. Posterior vitrectomies were 23, 21, 17, 10, 21, 28 and 25. Laser sessions were 44, 26, 33, 17, 23 and 33, respectively. OCTs dropped from a mean of 25.7 per day in the first half of March 2020 to 5.8 per day in the second half of March. A mean of 6.5 OCTs per day was made in April, rising to 19.1 in May and 39.5 in June. Conclusion It was possible to keep the ophthalmological activity during the pandemic outbreak due to the existence of a pre-scheduled fixed regimen for IVI and to the availability of personal protective equipment. The air-borne nature of the peril we are facing addresses the need to evaluate the physical conditions of health facilities, including ventilation, size of waiting and consult rooms and the need to avoid elevators.

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