In vivo comparison of three different porous materials intended for use in a keratoprosthesis.

Aim: The goal was to compare the biological response of the corneal stroma with three porous materials: a melt blown microfibre web of polybutylene:polypropylene (80:20); a polyester spun laced fabric (polyethylene terephthalate), and an expanded polytetrafluoroethylene. Fifty per cent of each of the materials were modified using argon radio frequency.

Methods: Discs (6 mm in diameter) were inserted into interlamellar stromal pockets and followed for a period of 12 weeks.

The assured clear distance ahead rule: implications for nighttime traffic safety and the law.

The assured clear distance ahead (ACDA) rule holds the operator of a motor vehicle responsible to avoid collision with any obstacle that might appear in the vehicle's path. Although widely considered a fundamental responsibility of safe driving, the ACDA rule is routinely violated by most drivers under nighttime conditions. This fact does not necessarily imply reckless disregard for public safety, however.

Advances in polyvinyl alcohol hydrogel keratoprostheses: protection against ultraviolet light and fabrication by a molding process.

Our goal was to: 1) modify poly(vinyl alcohol) hydrogels intended for use in a synthetic cornea to absorb ultraviolet light and 2) develop molding procedures for the fabrication of the device. Two ultraviolet light-absorbing monomers were incorporated by copolymerization. The resulting hydrogels protected against ultraviolet light, were not toxic to corneal fibroblasts, and the protection did not diminish during prolonged aqueous exposure.

Intraocular pressure-raising potential of 1.0% rimexolone in patients responding to corticosteroids.

Objective: To compare the intraocular pressure (IOP) elevating potential of 1.0% rimexolone and 0.1% fluorometholone alcohol ophthalmic suspensions in patients known to have responded to corticosteroids.

The symbiosis between basic and applied research.

To illustrate the interdependence between the solution of practical problems and the search for fundamental mechanisms, their relationship within the contexts of the history of night myopia and the problem of nighttime traffic accidents is discussed. Night myopia, or nearsightedness at night, which has been a problem since the late 18th century, was shown to be the result of a recently discovered oculomotor mechanism, the intermediate resting position of accommodation. With this knowledge, the handicap of nearsightedness at night ( a major problem in nighttime viewing such as driving and military operations) is readily amenable to solution.

The effect of tilted stripes in an optokinetic drum on gastric myoelectric activity and subjective reports of motion sickness.

Background: The effects of tilted and vertical optokinetic drum stripes on self-reports of motion sickness and electrogastrograms (EGG's) were measured to investigate possible differences in the effects of stripe orientation. The EGG is a non-invasive measure of gastric myoelectric activity. The normal frequency is 3 cpm, and dysrhythmic 4-9 cpm activity, gastric tachyarrhythmia, has been found to be associated with motion sickness symptoms, particularly nausea.

Effects of moderate dose alcohol on visual contrast sensitivity for stationary and moving targets.

Objective: Contrast sensitivity involves distinguishing threshold luminance differences and is usually assessed using static sine-wave gratings over a range of different spatial frequencies. The purpose of this study was to determine the effects of various levels of acute alcohol intoxication on contrast sensitivity to stationary and moving sine-wave gratings. Moving gratings required the subjects to make pursuit eye movements.

A behavioral link between the oculomotor and cardiovascular systems.

Although the eyes and the heart serve very different purposes, each receives autonomic innervation. Capitalizing on recent theoretical and technological innovations in the understanding and assessment of oculomotor and cardiovascular behavior, three experiments measured behavioral covariation between the oculomotor and cardiovascular systems. Measures of dark focus and dark vergence indexed oculomotor tone, and the spectral decomposition of variations in heart rate indexed cardiovascular control mechanisms.

Measuring and predicting the effects of alcohol consumption on contrast sensitivity for stationary and moving gratings.

Contrast sensitivity was measured for 12 healthy young males while sober, after ingestion of an alcohol placebo, and after ingestion of alcohol (95% grain alcohol; mean estimated blood alcohol level = .088%). Observations were made for both stationary gratings and gratings that traveled through a circular path and required pursuit eye movements.

Effect of pretreating porous webs on stromal fibroplasia in vivo.

We have previously demonstrated that keratocytes penetrate and deposit collagen after a porous web is inserted into interlamellar corneal pockets. In these studies our goal was to determine whether pretreatment of the porous discs would enhance wound healing. We have evaluated four methods of pretreating the porous disc prior to its placement in the stroma.

Evidence for the persistence of visual guidance information.

An earlier study from our laboratory provided initial support for the hypothesis that information facilitating visual guidance persists in the absence of retinal stimulation. The present study supports and extends this hypothesis with three experiments in which visually occluded subjects positioned a point of light at the location of a previously viewed target and also walked in the direction of a previously viewed path. In both tasks, performance was possible following occlusion, and in all cases, performance slowly and significantly decreased with longer durations of occlusion.

Quantitative perceptual estimates: verbal versus nonverbal retrieval techniques.

Examples of the inaccessibility of mental processes by means of verbal recall are described with particular reference to the accuracy of quantitative estimates of size, distance, and duration. Evidence is presented in support of the hypothesis that nonverbal retrieval techniques are more accurate than quantitative verbal estimates. Implications for the judicial process are considered.

The effects of visual factors and head orientation on postural steadiness in women 55 to 70 years of age.

This study was designed to establish reference data for the effects of head position and visual conditions on the standing posture of healthy women ages 55 to 70. Center of pressure (CoP) data were analyzed using ANOVA models. Total CoP displacement was 45% greater (significant, p less than .

Age differences in dynamic contrast thresholds.

Contrast thresholds for sinusoidal gratings of 1.5-18 cpd were measured in young (M = 24 years) and older adults (M = 69 years). Thresholds were determined for stationary gratings, and for gratings that traveled along a circular path at 5, 10, and 15 deg/sec.

Comparative anti-inflammatory efficacy of topical corticosteroids with low glaucoma-inducing potential.

Fluorometholone and clobetasone butyrate have been developed as ophthalmic corticosteroids because of their lesser potential to elevate intraocular pressure. Nevertheless, their primary use is the inhibition of an inflammatory response. Quantification of their anti-inflammatory effect in the rabbit cornea indicates that 0.

In vivo fibroplasia of a porous polymer in the cornea.

We have developed a melt-blown fibrous construction of polybutylene/polypropylene in which we previously demonstrated keratocyte ingrowth and collagen synthesis in vitro. In the present studies, we evaluated this material in vivo in interlamellar corneal pockets for periods of up to six months. By day 42, the porous interstices of the disc were heavily populated with keratocytes.

The influence of visual factors on fall-related kinematic variables during stair descent by older women.

Despite the documented health hazards associated with stair descent, the mechanisms of falling on stairs remain relatively unexamined. The objectives of this study were to define kinematic variables that could be used to describe foot-stair spatial relationships during the mid-stair phase of stair descent, and to investigate the effects of various visual and environmental conditions on those variables in a group of 36 healthy women between the ages of 55 and 70. Foot clearance and foot placement were measured through high-speed film analysis.

Clinical evaluation of ciprofloxacin 0.3% ophthalmic solution for treatment of bacterial keratitis.

A multicenter, prospective clinical study of 148 culture-proven cases of bacterial keratitis, treated with ciprofloxacin 0.3% ophthalmic solution, compared its clinical and antibacterial efficacy with the standard therapy regimen of each investigator. Most often, this consisted of topically administered fortified cefazolin (33 mg/ml) and fortified gentamicin or tobramycin (14 mg/ml).

Antibacterial effectiveness of ciprofloxacin 0.3% ophthalmic solution in the treatment of bacterial conjunctivitis.

Two hundred eighty-eight cases of culture-proven bacterial conjunctivities were evaluated as part of two multicentered, randomized, prospective clinical studies comparing the antibacterial efficacy of topically administered ciprofloxacin 0.3% either with a placebo or with tobramycin 0.3%.

Can normal outdoor activities be carried out during civil twilight?

Ambient illumination during civil twilight, which occurs approximately a half hour before sunrise and after sunset, has traditionally been characterized as posing no restriction on normal visual activities. However, consideration of the selective degradation of visual-recognition functions and the concurrent sparing of visual-guidance functions at the prevailing (relevant) luminance levels suggests that this characterization of civil twilight is no longer appropriate, particularly in light of the visual demands of industrialized society. Rather, special notice should be taken of the implications of selective degradation of visual recognition during civil twilight for traffic safety and other visually demanding hazardous tasks.

Effect of luminance on the relation between accommodation and convergence.

When luminance is lowered, both vergence and accommodation tend to shift toward different and individually characteristic resting postures, commonly referred to as dark-vergence and dark-focus. In order to determine the luminance level at which these two mechanisms correspond to a target distance, subjects viewed a light spot 0.4 mm in diameter, corresponding to 1.