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Biomedical subjects

Bradley Johnson

Publications and source records attributed to Bradley Johnson.

2 recordsLinked to original sources

High-order aberrations in pseudophakia with different intraocular lenses.

PURPOSE: To compare high-order aberrations in patients who had cataract surgery and implantation of different types of intraocular lenses (IOLs). SETTING: Sir Charles Gairdner Hospital and Lions Eye Institute, University of Western Australia, Perth, Australia. METHODS: Fifty eyes of 48 patients were included in this study. The optical aberrations were measured with the Hartmann-Shack wavefront sensor (Zyoptix, Bausch & Lomb) before and after surgery using a 5.0 mm wavefront aperture diameter for all comparisons. The eyes were divided into 4 groups according to the type of IOL (material and curvature). A fifth group of 10 eyes of 6 elderly patients with normal crystalline lenses had the same examination. RESULTS: There was no statistical difference in high-order aberrations between the 2 acrylic IOL groups with different curvatures (P>.05) or between the silicone and poly(methyl methacrylate) (PMMA) IOL groups (P>.05). However, the measured high-order aberrations were significantly higher (3rd through 5th order) in the 2 acrylic IOL groups than in the PMMA and silicone IOL groups (P<.05). CONCLUSIONS: An increase in IOL high-order aberrations contributed to the decline in retinal image quality. An IOL modifies the entire aberration pattern of the eye. There was a statistically significant increase in aberrations in patients with an acrylic IOL compared to those with a silicone or PMMA IOL. The exact mechanism is uncertain. Further study is required to optimize IOL design.

Acrylic Resins↗

Olfactomotor activity during imagery mimics that during perception.

Neural representations created in the absence of external sensory stimuli are referred to as imagery, and such representations may be augmented by reenactment of sensorimotor processes. We measured nasal airflow in human subjects while they imagined sights, sounds and smells, and only during olfactory imagery did subjects spontaneously enact the motor component of olfaction--that is, they sniffed. Moreover, as in perception, imagery of pleasant odors involved larger sniffs than imagery of unpleasant odors, suggesting that the act of sniffing has a functional role in creating of olfactory percepts.

Auditory Perception↗