Biomedical subjects
Publications and source records attributed to G D Faulkner.
Cataract, a leading cause of blindness, has been successfully treated by surgery since ancient times. Surgical methods have evolved from couching, to extraction, to phacoemulsification. Cataract surgery is now an outpatient procedure that can be performed with topical anesthesia. Intraocular lens implants restore natural vision without thick glasses and contact lenses. Current procedures are highly successful in restoring vision.
Central corneal endothelial cell loss was compared following primary insertion of folded posterior chamber silicone intraocular lenses (IOLs) in 29 eyes and Sinskey-style polymethylmethacrylate posterior chamber IOLs in 20 eyes. Cataracts were removed by phacoemulsification and sodium hyaluronate was used in all cases. The mean follow-up time was greater than seven months. The average cell loss was 9.6% and 10.9%, respectively. There was no significant difference in cell loss or visual results in the two groups. The amount of cell loss compares favorably with other series in which cell loss was determined following cataract surgery with and without IOL implantation.
A two-forceps system for folding and inserting silicone lens implants and the method for using them is described. Other methods and instruments currently available are reviewed, and requirements for folding and inserting silicone intraocular lenses are discussed.
The eyes of an 89-year-old male were obtained for postmortem examination five months after implantation of a foldable silicone elastic lens implant. Two months after surgery, the implant had been repositioned from capsular bag to ciliary sulcus fixation to correct postoperative decentration and tilt. Pathological examination showed both haptics located in the ciliary sulcus. There was no significant inflammatory reaction in the adjacent uveal tissue and no erosion of the haptics into the iris or ciliary body.
Silicone elastic intraocular lens implants (STAAR Model B) were implanted in 18 human eyes following extracapsular cataract extraction by phacoemulsification. Visual acuity of 20/40 or better was obtained in 17 eyes which had no preexisting pathology. Implants decentered and tilted in five of six eyes in which implants were placed in the bag. This was the only significant complication observed and is prevented by avoiding in-the-bag placement of the implant.
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Single-plane posterior chamber lenses cannot be used when the posterior capsule is not intact. Use of a two-lane posterior chamber lens is independent of capsular integrity and retains the advantages of a posteriorly positioned optic. This acapsular posterior chamber lens has two posterior J-loops on the same plane as the optic and two anterior closed loops which are positioned in front of the iris. Use of this lens in 28 cases was associated with minimal subluxation and pseudophakodonesis.
A new form of cholinesterases has been discovered in rabbit liver; the new enzymes are monomeric butyrylcholinesterases (EC 3.1.1.8), mBuChE I and mBuChE II. These enzymes are inhibited reversibly by chlorpromazine in the pharmacologically active concentration range and they exhibit mixed competitive-noncompetitive inhibition patterns. The apparent competitive inhibition constants, Ki with chlorpromazine, are 1.8 x 10(-6) M for mBuChE I and 7.6 x 10(-6) M for mBuChE II, whereas the noncompetitive inhibition constant is 1.1 x 10(-5) M for mBuChE II as determined by spectrophotometric assay with n-butyrylthiocholine iodide substrate. Although inhibition of mBuChE I also exhibited noncompetitive behavior, a binding constant could not be determined. Human serum oligometric butyrylcholinesterase (oBuChE) was employed as a control cholinesterase and also demonstrated mixed inhibition kinetics. The competitive inhibition constant for the oBuChE was 5.5 x 10(-7) M in the low substrate region, whereas the apparent noncompetitive binding constant was 1.6 x 10(-5) M in the activated higher substrate region with n-butyrylthiocholine iodide as the substrate and chlorpromazine as the reversible inhibitor. The presence of a noncompetitive binding component indicates the presence of an operative modifier or allosteric site binding the inhibitor on both mBuChEs and the oBuChE. The inhibition constants were calculated assuming that the enzymes followed simple Michaelian kinetics.