Disposable contact lenses and their complications

Disposable soft contact lenses (DSCLs) have been marketed as a safer alternative to conventional soft lenses. Extended-wear DSCLs are designed for one or two weeks of continuous use before disposal. Those for daily wear are designed for use as conventional daily wear soft lenses, with daily removal and storage for 2 to 4 weeks before disposal. Beside minor complications, such as corneal abrasion, giant papillary conjunctivitis and toxic epithelial reactions to contact lens solutions, the most serious complication occurring in contact lens users is ulcerative keratitis. Several case-control studies performed over the last years, demonstrated that disposable contact lenses were associated with a 14-fold excess risk of ulcerative keratitis compared with that for patients wearing conventional daily-wear soft contact lenses and a 13-fold excess risk compared with that for wearers of rigid gas permeable contact lenses. However, the major risk factor for corneal ulceration in contact lens wearers is overnight lens wear of 1 to 3 nights. It was estimated that 49 to 74% of cases of contact lens associated ulcerative keratitis could be prevented by eliminating overnight wear.     

Uniocular aphakia--conventional contact lenses and aniseikonia

Ehrich and Kolbegger show in their papers that aniseikonia should not prevent binocular functions in a uniocular aphakia. This is contrary to our own experiences. In this paper we suggest that the results of Ehrich and Kolbegger must be worse in spite of their final conclusions. Their hypotheses are discussed.     

Iridocapsular lenses versus iris-clip lenses: comparison of the results and complications of 100 of each

The results and complications of implantation of 100 iridocapsular and 100 iris-clip lenses are evaluated. The follow-up period for the first group varied from one to 25 months (mean 12 months) and from one to 43 months (mean 27 months) for the second group. I performed all of the operations and most of the follow-up examinations. Of the patients with iridocapsular lenses, 86 percent and of those with iris-clip lenses, 87 percent obtained a visual acuity of 0.5 (6/12) or better. Binocular vision, positive depth perception, and a small degree of aniseikonia (3% or less) are evident optical benefits. The complicatioons most frequently necessitating a second operation were retained lens material (17%) and repositioning the pseudophakos (6%) in the iridocapsular group. The four-loop lenses caused fewer problems; in one case, posterior luxation necessitated its removal.     

Teenage driving fatalities

BACKGROUND/PURPOSE: A recent legislative effort in New Hampshire to institute a graduated licensing system for teenagers (TA) led to an analysis of state data on fatal crashes involving TA drivers. This provides an overview of these events and suggests possible prevention strategies. METHODS: Data on fatal crashes involving TA drivers was obtained for the years 1991 through 1996 from the Fatal Accident Unit, Division of State Police, New Hampshire Department of Safety. RESULTS: From 1991 through 1996, there were 100 events resulting in 109 total deaths, of which 76 were TA. Five involved motorcycles. Four drivers struck pedestrians, and two struck children on bicycles. In one case, an object fell from a truck, crushing a car. The remaining 88 were single- or multiple-car crashes, and these were analyzed further. Two thirds of the drivers were boys. The driver breakdown by age was 15 years, 3; 16 years, 21; 17 years, 26; 18 years, 20; 19 years, 18. The TA driver was killed in 47% of the events. Nineteen percent resulted in the death of the driver of another car. In 62 events, there were passengers in the TA's car, and in 55% of these, a passenger was killed. Twenty percent of the crashes involved drugs or alcohol, and almost two thirds of these occurred between 10:00 PM and 6:00 AM. Seat belts were not used by at least 72% of those injured fatally. In 59%, known traffic violations, usually speeding, contributed. More detailed data were available for 1995 through 1996, during which there were 30 crashes resulting in 33 deaths. Speed limit did not correlate with number of crashes. One-car crashes outnumbered multiple-car, 57% to 43%. Ninety percent occurred on single-lane roads. Most significantly, 63% of the drivers had been licensed less than 1 year and 47% less than 6 months. In this latter group, drugs and alcohol played no role, and none occurred between 11:00 PM and 6:00 AM. CONCLUSIONS: Two at-risk groups exist. The first is inexperienced sober TA drivers on single-lane roads during conventional hours. As experience increases, the second group appears: TA who have been drinking and are out late at night. Prevention strategies must take into account these two groups.     

Aging, dementia and automobile driving

According to Norwegian law, drivers 70 years and older must carry a health certificate. This is issued by a general practitioner. If the patient is not supposed to drive because of a medical condition, the doctor should report this to the County Health Officer. This can be problematic, not only because assessing whether a patient fulfills the criteria for driving is difficult, but also because the doctor has obligations to both the public and his patient. These problems are discussed, based on assessment of available literature and on personal experience. Dementia is common in old age and affects approximately 15% of persons aged 75 and older. Patients with moderate and severe dementia should certainly not drive. However, some patients with mild dementia can nevertheless be safe drivers. The problem, however, is to identify the safe drivers among patients with mild dementia. The current regulations on dementia and driving are presented briefly.     

Aberrations of spherocylindrical spectacle lenses

A procedure has been developed for tracing a bundle of rays through and ophthalmic lens and a schematic eye with its primary line of sight pointed through various parts of the lens. A bundle of eight rays can provide data for assessing the quality of the image formed by such a system. To test the procedure and to generate data which can help in selecting a method for evaluating image quality, we selected a single lens as an example. The lens selected has a spherical back surface (-5.00 diopters) and a toric front surface (+15.00 diopters in the vertical and /10.00 diopters in the horizontal). It has a center thickness of 5 mm and glass of index 1.523. Spot diagrams were generated with the eye pointed in various directions through the ophthalmic lens. The data generated showed that peripheral bundles which fall between the principal meridians emerge as astigmatic bundles. This leads to the proposal that blur circle theory can be used for evaluating the quality of the optical image and that it suffices in the case of a spherocylindrical ophthalmic lens to base the tolerances for refractive power on measurements made in the principal meridians.     

Scleral suturing of intraocular lenses

This paper describes a simple, safe, and reproducible method for scleral suturing intraocular lenses. The method uses standard tools and equipment.