Biomedical subjects
Publications and source records attributed to R C Drews.
To find out if postoperative astigmatism decays less if Mersilene rather than nylon sutures are used, 25 patients had a standard wound closure with 10-0 nylon in one eye and 11-0 Mersilene in the other. There was no difference in the astigmatism decay over a 6-month period.
This article reviews published formulas for intraocular lens power determination. In the author's opinion, lack of agreement as to which formula is the most accurate is because none of them reduce the fundamental (biological) problem of variation (scatter, or standard deviation) of results. Suggestions are made for wise use.
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Calculations were made comparing a variety of formulas in patients who required unusually high and low power intraocular lenses. Of the formulas tested, the author found the Colenbrander formula to be more accurate for myopic patients and the SRK formula to be more accurate for hyperopic patients.
The elasticity and memory of intraocular lens loops was tested by manufacturing lenses with matching physical properties but with loops of either polypropylene or VS-100 polymethylmethacrylate (PMMA). After establishing the reliability of measurements, these lenses were compressed under physiologic conditions for up to three years. The rates and extent of reexpansion of the loops were then measured. Given loops of equivalent initial flexibility, VS-100 PMMA has less long-term tendency to reexpand to its initial shape than polypropylene.
An easy and successful technique is described for implanting a posterior chamber lens at the time of corneal grafting in patients who have no posterior lens capsule for support. Using the principle of pupil entrapment with the lens optic in the anterior chamber, the lens loops are placed behind the iris and secured with McCannel sutures one at a time. Finally, the lens body is placed behind the pupil and covered with Healon, and then the grafting is completed.
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This new unit has the advantages of motorized aspiration with greater control and far less cost than a console unit. The instrument is small and light enough to fit comfortably in the surgeon's hand. For those who prefer a small light handpiece, the unit is available in two parts. It is simply designed like a manual aspiration system without the disadvantage of two-handed operation.
Seventy patients who received lens implants of unusually high or low power were studied retrospectively. There were 36 myopes and 34 hyperopes. All were followed a minimum of two years. Although both groups of patients presented technical problems at surgery, the visual acuity and general results were good.
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Sodium hyaluronate (Healon) is a valuable adjunct in anterior segment surgery following trauma, including surgical induced trauma. The application of a few principles permits a wide variety of techniques.
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Three series and a control group of patients have been analyzed to study the early and long-term complications of neodymium: YAG laser anterior capsulotomy. In the author's opinion, the results have been favorable, and the procedure is recommended. It is important that a limited number of punctures be made, especially if there is any delay in surgery.
Pathological changes in eyes containing intraocular lenses were studied in the 28 specimens which constitute the collection of eyes with intraocular lenses at Washington University School of Medicine in St Louis. Except for an occasional nest of lymphocytes, local areas of tissue thinning and fibrous reaction where there had been tissue compression, the striking finding in these eyes has been the lack of pathological response. Most of them showed a significant loss of endothelial cells but none had clinical corneal dystrophy.
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Results of threshold static perimetry in nine cases of toxic retinopathy produced by chloroquine phosphate and hydroxychloroquine sulfate are reported. Pericentral visual field defects in an advanced case correlated well with ophthalmoscopically visible defects in the pigment epithelium. In a less advanced case, perifoveal defects in the visual field of one eye were found to be demonstrable in the absence of any fundus abnormalities by either ophthalmoscopy or fluorescein angiography. In both cases, visual field defects were deepest on the superior or vertical meridian, just above the point of fixation. Since defects were found to be deepest along the superior vertical meridian, threshold static perimetry that includes this location should be the most sensitive method of detecting the early stages of visual field damage in chloroquine retinopathy.