Orthopaedic workforce studies: 1980 to 1985.

A committee was appointed by the American Academy of Orthopaedic Surgeons in 1981 to continue the orthopaedic workforce studies begun by D. Kay Clawson a decade earlier. The committee found that the rapid increase in orthopaedists graduating from residency programs between 1970 and 1982 had resulted in a workforce in which fully 1/2 of practicing orthopaedists certified by the American Board of Orthopaedic Surgery were younger than 45 years. At that time, orthopaedists graduated at the rate of 700 per year. If that rate continued and if nothing else changed, it was calculated that the number of practicing board-certified orthopaedists per 100,000 people in the United States would continue to increase for at least 20 more years. The effect of reducing resident output by 10% increments also was projected with the hope that this information might influence future planning. In fact, a 10% reduction in resident output was achieved and the current ratio of board-certified orthopaedists per 100,000 population is very close to that predicted. In addition, the 1981 orthopaedic workforce committee developed a map of the United States that showed the number of board-certified orthopaedists in each major zip code. This map was distributed to every allopathic residency program in the United States in the hope that displaying this map might encourage graduating residents to choose more underserved areas in which to begin their practices. Evidence obtained subsequently by interviewing candidates taking Part II of the American Board of Orthopaedic Surgery certifying examinations showed this map seemed to have had very little effect in correcting workforce maldistribution.

Effects of coatings on the fracture resistance of ophthalmic lenses.

BACKGROUND: Scratch-resistant (SR) and anti-reflective (AR) coatings are commonly applied to plastic ophthalmic lenses. Fracture resistance is greatly affected by surface characteristics, and coatings may have a weakening effect. Static load testing is an efficient, quantifiable alternative to the drop ball test and has been suggested as useful for comparing lenses of a given material. METHODS: An Instron static load tester was used to test the fracture resistance of 140 CR-39 lenses divided into 4 groups: uncoated, prepared for AR coating but not actually coated, AR coated, and factory SR coated. RESULTS: Compared to the control uncoated group, AR coating reduced the required fracture energy by 63% and SR coating by 57%. Preparation for AR coating had no significant effect. CONCLUSIONS: These results are at least qualitatively consistent with drop ball testing and have significant implications as new plastic materials are developed, made thinner, and variously coated.

Low vision magnifiers--their optical parameters and methods for prescribing.

Information provided by manufacturers of low vision magnifiers is usually insufficient to allow the clinician to predict accurately the resolution improvement that patients may be expected to achieve. We have measured and tabulated the key optical parameters of 92 stand magnifiers and 53 hand-held magnifiers. For the fixed focus stand magnifiers, the image location and the equivalent power of the lens system have been determined and the enlargement ratio has been derived. For each magnifier, 3 different eye-to-lens distances (2.5, 10, and 25 cm) have been considered and, for each of these, the Equivalent Viewing Distance (EVD), the eye-to-image distance, and the theoretically predicted field width have been computed. The EVD is useful in predicting resolution performance because, for a given patient, the visual resolution limit will be directly proportional to the EVD. The eye-to-image distances allow the clinician to consider whether the patient will be in satisfactory focus or whether adjustments need to be made to the power of any reading addition. The stand magnifiers are listed in order of the EVD they give when the eye is a moderate (10 cm) distance from the magnifier. For the hand-held magnifiers, the equivalent powers have been measured. The EVD for a hand-held magnifier will be the same as the equivalent focal length of the magnifier if the lens is used so that the image is at or close to infinity. The tables include supplementary information on the size of the magnifier lenses and whether the magnifiers incorporate battery, electric, incandescent, or halogen lighting systems. Examples are presented to illustrate how the tables might be used in the selection of magnifiers to meet the resolution and other needs of individual patients.