Risk of infection from sleeping with contact lenses on: causes of risk.

Although the risks associated with extended wear contact lenses are well-known, there has not been an adequate explanation of why sleeping with the lenses on increases the risk of infection. It is contended that the reduction in the available oxygen caused by contact lenses does not in itself explain the high rate of corneal infection caused by wearing the lenses while sleeping. This paper examines the contribution that the mechanism of sleep itself makes to the risk of infection, based on patient studies in two optometric practices. The results show that the risk of ocular infection, particularly corneal ulcers, is substantially increased with overnight wear of lenses. A review of the role of oxygen deprivation, atmospheric pollution, bacterial survival strategies, infection-resistant defenses during wakefulness, and patterns of sleep indicates that oxygen deprivation of the cornea is not the only factor in the increased risk associated with wearing the lenses while sleeping. It is suggested that the combination of the introduction of airborne pollutants to the contact lens during the day, the reduced oxygen transmission through contact lenses and closed lids, and the lack of eye and lid movement during sleep together create the conditions in which bacterial infection is most likely to occur.

Role of the optometrist in age-related maculopathy.

The increasing aging segment of our population presents both a challenge and an opportunity for optometry. The challenge is to provide sufficient manpower skilled in the problems of the aging and to assure participation in any therapeutic program. The opportunity is to help those with maculopathy to achieve the required visual performance. This entails prevention measures, detection diagnosis, and referral for medical care when indicated. When medical therapy is not helpful, the optometrist employs low vision techniques to surmount the visual handicaps to achieve visual performance commensurate with lifestyle needs. A discussion of retinal performance to aid in understanding age-related maculopathy (ARM) is presented. Similarly, the various low vision techniques used to aid the patient with ARM are considered.

A case in point extended.

No visual examination can be considered complete without visual field investigation. Garmizo suggests at least a hand confrontation, and Goodlaw urges a refinement of this procedure using a wand with a 3" by 3" background to a 3mm target. There is also a question of body clues to hand location when the hand is the target. This suggested procedure circumvents this by using a 6" to 8" long handle on the target.

Three binocularity evaluation methods.

Determining effort expended in binocular seeing is usually accomplished by equating dissociated phoria with total vergence ability. Fixation disparity testing by disclosing failure of precise binocular alignment is a second method which helps to assess both direction and quantity of prism power needed to accomplish alignment. Neither of these two methods delineates the foveal role as a sensory fusional lock in binocularity. The third is the Goodlaw test in which the exact focus of the eyes is disturbed through plus and/or minus lenses, provides this information and further directs therapy.

Rehabilitating a patient with bitemporal hemianopia.

For those with large field defects, employing totally reflecting mirrors or prisms to reflect information from non-seen areas also blocks out areas within the remaining functional field. A patient with large field defects commonly resists further encroachment upon any part of his limited field. Employing a 30 percent reflectance mirror retains the remaining field unencumbered (because this type of mirror is also semi-transparent) and provides information from the blind area by reflection.

Assessing field defects of the low-vision patient.

Field losses are of particular significance to the low-vision patient, so it is incumbent upon the low-vision clinician to determine the degree, location, and extent of this field loss. Optometrists prefer to map the fields carefully for quantitative analysis, but if fatigue or debility prevent this a simplified technique is required. Devices and techniques are described which are shown to be effective.

Spectacles for the emmetropic presbyopic optometrist.

Presbyopia brings special seeing problems for an emmetropic optometrist. Incorporating the bifocal into a half-glass offers several advantages. The best parameters for this spectacle form are derived from experience, and also by comparing it to single-vision half-glasses, bifocals, and trifocals. Particular facility in both prescribing and fabricating derives from the great number of power and size relations between upper and lower segments available. One can extrapolate similar benefits in this spectacle form for other occupations and hobbies as well as for presbyopic wearers of single-vision contact lenses.

Headborne illuminator for the partially sighted.

An inexpensive, headborne device is described that provides a bright spot of light on reading material even when the material is brought within 1 or 2 cm of the viewing eye. This aid has been used with great success by one of the authors for about 2 yr. This illuminator, or modifications of it, should prove valuable to other partially sighted people.