Simulation of Vitreous Traction Force and Flow Rate of High Speed Dual-Pneumatic 7500 Cuts Per Minute Vitrectomy Probes.

Purpose: To develop methods to simulate vitreous flow and traction during vitrectomy and qualify these methods using laboratory measurements. Methods: Medium viscosity and phase treatment were adjusted to represent vitreous (Eulerian two-phase flow) or saline solution (single-phase Navier-Stokes flow). Retinal traction was approximated using a one-way fluid-structure interaction simulating cut vitreous volume coupled to a structural simulation of elastic stretching of a cylinder representing vitreous fibers entrained in the flow. Results: Simulated saline solution flow decreased, but vitreous flow increased with increasing cut rate, consistent with experimental trends observed for the 50/50 duty cycle mode. Traction simulations reproduced all trends in variation of traction force with changes in conditions. Simulations reproduced the majority of traction measurements within experimental error. Conclusions: A scientific basis is provided for understanding how flow and traction vary with operational parameters. This model-based analysis serves as a "virtual lab" to determine optimal system settings to maximize flow efficiency while reducing traction. Translational Relevance: The model provides a better understanding regarding how instrument settings can help control a vitrectomy procedure so that it can be made as efficient as possible (maximizing the rate of vitreous removal) while at the same time being made as safe as possible (minimizing retinal traction).

Movement and motor development in ELBW infants at 1 year is related to cognitive and motor abilities at 4 years.

A relationship between motor ability and cognitive performance has been previously reported. This study aimed to investigate the association between movement and cognitive performance at 1 and 4 years corrected age of children born less than 1000 g, and whether developmental testing of movement at 1 year is predictive of cognitive performance at 4 years. Motor development was assessed at both ages using the neurosensory motor developmental assessment (NSMDA) and motor development was classified as normal, or minimal, mild, moderate-severe dysfunction. Cognitive performance was assessed on the Griffith Mental Developmental Scale at 1 year and McCarthy Scales of Children's Abilities at 4 years. Subjects included 198 children of birthweight less than 1000 g. Of these 132 children returned for follow-up at the corrected ages of both 1 and 4 years. The 66 children not included had a slight increase in gestational age, while the mothers were younger and had a lower level of education. A significant association was found between NSMDA group classification at 1 year and cognitive performance at both 1 and 4 years (p<0.001; p<0.0001) and between the subscales of each test (1 year, p<0.0001; 4 years, p<0.001). Group classification of motor development at 1 year was predictive of cognitive performance at 4 years (p<0.0001) and this was independent of biological and social factors and presence of cerebral palsy (CP). The findings support a close link between motor and cognitive development in children born <1000 g and emphasise the advantage of detailed assessment of movement at 1 year.