Comparison of depth of focus and low-contrast acuities for monofocal versus multifocal intraocular lens patients at 1 year.

PURPOSE: Multifocal lenses have been shown to produce enhanced near and intermediate vision. The division of incoming light into more than one focal point must physically produce retinal images of reduced contrast. The purpose of this report is to provide quantitative data on the increased depth of focus and decreased contrast sensitivity demonstrated in patients receiving the 3M diffractive multifocal lens versus the parent monofocal control lens. METHODS: Uncorrected and best-corrected distance and near acuities, Regan and Pelli-Robson contrast sensitivity measurements, and defocus curves were obtained on 22 eyes with monofocal and 16 eyes with multifocal age-matched, pathology-free implants at 1 year after surgery. FINDINGS: Visual acuity data demonstrated significantly improved (P < 0.001) near acuities in multifocal patients with manifest refraction in place. No difference was noted between implants for other acuity measures. A statistically significant reduction (P < 0.05) in contrast sensitivity was measured for multifocal implants at the limits of contrast and resolution (Regan 4%); however, careful patient questioning revealed no clinical impact. Defocus curves demonstrated significantly increased (P < 0.0001) depth of focus at the 20/40 acuity level of 3.8 diopters (D) in multifocal patients versus 1.8 D in monofocal patients. CONCLUSION: The quantifiable and expected loss of contrast sensitivity in the examining lane, not manifest in patient awareness, appears to be an acceptable tradeoff for enhanced near/intermediate vision and depth of focus.

A prospective, randomized, double-masked comparison of a zonal-progressive multifocal intraocular lens and a monofocal intraocular lens.

INTRODUCTION: Multifocal intraocular lenses (IOLs) have been designed to provide improved near visual acuity without spectacles compared with monofocal IOLs. Early studies have reported variables amounts of decreased visual acuity and contrast sensitivity with multifocal IOLs, and some patients have experienced halos and glare. METHODS: The authors performed a prospective, double-masked, multicenter evaluation of 62 patients randomized between a new zonal-progressive optic multifocal IOL and a monofocal IOL. RESULTS: Mean postoperative spherical equivalent, astigmatism, and uncorrected and best-corrected distance visual acuity were similar between the two groups. Patients with a multifocal IOL achieved significantly better uncorrected near visual acuity than patients with monofocal IOLs (J3+ versus J7; P less than 0.0001). With distance correction only, mean near visual acuity was J2 versus J5- (P = 0.0001). Best-corrected near visual acuity was J1 for both groups, with 1.36 diopters (D) for the multifocal group versus 2.37 D for the monofocal group (P less than 0.0001). Regan contrast sensitivity was lower for the multifocal patients at all contrast levels, and achieved statistical significance at very low contrast (11% contrast; P = 0.0024). Fifty-two percent of patients with a multifocal IOL reported that they did not need spectacles at all or used them only for their fellow eye, compared with 25% of the patients with monofocal IOLs. CONCLUSION: Both monofocal and multifocal implant patients were very satisfied with the results of their cataract extraction and IOL implant surgery. A small loss of contrast sensitivity with the multifocal IOL was demonstrated, consistent with theoretical predictions. The functional significance of the loss of contrast sensitivity appears to be small and counterbalanced by the advantage of improved uncorrected near visual acuity.

Production of low molecular weight cadmium-binding proteins in rabbit lung following exposure to cadmium chloride.

Low molecular weight cadmium-binding proteins were studed in lung tissue from rabbits exposed to aerosols of CdCl2. Lungs obtained from animals exposed by inhalation to aerosols of 800 or 1600 micrograms/m3 CdCl2 for 2-hr periods/day, every other day for a 5-day period, were found to contain at least three low molecular weight cadmium-binding proteins, two of which were similar electrophoretically and spectrally to rabbit liver metallothionein. The third protein(s), which accounted for the majority of the cadmium in the soluble fraction of the tissue, did not bind to an anionic exchange gel and did not appear to be a polymerized form of metallothionein. Translocation studies of lung cadmium suggest a long half-life for cadmium in lung tissue following inhalation exposure, due perhaps to the high affinity of cadmium for specific lung cadmium-binding proteins. A small but significant redistribution of lung cadmium did occur to both kidney and liver tissue with time.