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Biomedical subjects

Kenneth J Hoffer

Publications and source records attributed to Kenneth J Hoffer.

3 recordsLinked to original sources
PubMed2003

Ultrasound axial length measurement in biphakic eyes.

To determine the calculations to correct the error in ultrasound measurement of a phakic eye with a phakic intraocular lens (IOL) (biphakic eye) to increase the accuracy of IOL power calculation should cataract surgery become necessary. Mathematical derivations were performed to calculate the error caused by a phakic IOL while measuring an eye using an average sound velocity. A simple model was developed to allow correction of the axial length (AL). If the eye is measured at an average velocity of 1555 meters/second, the following calculation can be used depending on the material of the phakic IOL: AL(corrected) = AL(1555) + X x T, where T is the central thickness of the phakic IOL and X = +0.42 (0.41 - 0.42) for poly(methyl methacrylate), -0.59 (0.56 - 0.59) for silicone, +0.11 (0.10 - 0.12) for Collamer, and +0.23 (0.23 - 0.24) for acrylic. By obtaining the dioptric power of the phakic IOL and central thickness from the manufacturer and knowing the material of the lens, a mathematical correction can be made to arrive at the true ultrasound AL in a biphakic eye.

Body Weights and Measures↗
PubMed2002

Phakic refractive lens experience in Spain.

PURPOSE: To evaluate the efficacy, predictability, and safety of a phakic refractive lens (PRL) for high myopia and hyperopia. SETTING: Instituto Oftalmológico Hoyos, Barcelona, Spain. METHODS: A PRL was implanted in 31 eyes (17 myopic, 14 hyperopic) with a mean preoperative spherical equivalent (SE) of -18.46 diopters (D) (range -11.85 to -26.00 D) for myopia and +7.77 D (range +5.25 to +11.00 D) for hyperopia. All eyes had a thorough ophthalmologic examination before and after surgery. The follow-up was at least 12 months. RESULTS: At 1 year, the mean postoperative SE in the myopic group was -0.22 D +/- 0.87 (SD) and 82% were within +/-1.00 D of the desired refraction. The mean postoperative SE in the hyperopic group was -0.38 +/- 0.82 D, and 79% were within +/-1.00 D. Snellen lines of visual acuity were gained in 65% of the myopic eyes (8 eyes gained 1 line, 3 eyes gained 2 lines), and no eye lost lines. In the hyperopic group, 1 eye gained 1 line of acuity and 1 eye lost 1 line. In the hyperopic group, complications included pupillary block in 2 eyes and pigment dispersion signs without intraocular hypertension in 1 eye. In the myopic group, 1 eye had a corticosteroid-induced intraocular pressure rise, 1 eye had a spot of anterior cortical lens opacity immediately after surgery that did not progress, and 3 eyes with the PRL model 100 had decentration that required replacement of the lens. Four patients (2 myopic, 2 hyperopic) reported night halos in both eyes. CONCLUSIONS: Results indicate that PRL implantation to correct high myopia and hyperopia is a relatively rapid, safe, predictable, and stable method that in many cases also improves the best corrected visual acuity. Complications such as visually significant progressive cataract and pigmentary glaucoma were not observed.

Adult↗