Research scientists are assuming more and more of the responsibilities of running optometry programs.
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Education, Medical↗
Biomedical subjects
J P Schoessler
Publications and source records attributed to J P Schoessler.
Ensuring the future of optometry's graduate programs.
Financial burdens, time and family commitments, peer status, insecure feelings concerning academia, and continuing "student" stigma are some of the pressures that discourage optometrists from entering graduate programs in visual science or other fields. In order to ensure the continued future training of optometrists with additional graduate degrees, we must begin to develop better financial packages, proactive recruitment strategies, increased networking opportunities, more secure career opportunities, streamlined graduate programs, and the affirming of the rewards of graduate study by those who have had successful careers.
Education, Graduate↗
Contact lenses and eye closure: comparative analysis using three different methods to induce corneal swelling.
To determine if the methods used to induce closed-eye corneal swelling significantly affect the swelling results, we conducted a randomized, double-masked study of 12 experienced daily wearers of rigid lenses using 3 measurement conditions for closed-eye contact lens wear. In addition to the control (no lens) condition, each of five rigid gas-permeable (RGP) lens types and two soft lens types were worn overnight by each subject at different measurement sessions. The overnight swelling response measured by optical pachymetry immediately at waking (8 h closed-eye) for untaped eyes was not significantly different from the swelling measured when the eye had been taped shut overnight and measured 1 h after the subject was awake (9 h closed-eye). The 3 h closed-eye corneal swelling response was significantly lower (p less than 0.0001) than both of the overnight corneal swelling responses. The average corneal swelling response for the lenses used was inversely proportional to the equivalent oxygen percentage (EOP) of the lenses. A high degree of intersubject variability was observed in the corneal swelling response.
Adult↗
Actual wearing time vs. possession time of contact lenses.
Sixty-two subjects who had never worn contact lenses were fitted with various rigid gas permeable (RGP) contact lenses. Contact lens wearing logs kept by the subjects indicated up to an 8-fold difference in total on-the-eye wearing hours among the subject population. Average daily wearing time for the group during the 7 to 12 month interval was 9.42 h/day. These findings show that persons who have had rigid lenses in their possession for 1 year have widely varied wearing times, and that "time from dispensing" does not accurately reflect patient lens use. Wearing schedule "gaps" are frequently due to broken or lost lenses, and perceived lens comfort seems to affect total wearing time significantly.
Adolescent↗
Corneal endothelial polymegathism after the extended wear of rigid gas-permeable contact lenses.
To determine if there are any corneal endothelial cell size and shape changes in subjects wearing rigid gas-permeable contact lenses for cosmetic extended wear, six unadapted lens wearers were fitted using four different lens materials. Each subject wore one lens extended-wear and the other daily-wear for 3 months. Before lens wear and after 3 months, noncontact endothelial photographs were taken. Cell tracings were analyzed by a digitizing computer. This study showed significant endothelial polymegathism, an increase in maximum cell area to minimum cell area, and a significant decrease in percent frequency of hexagonal cells in the extended-wear eyes. There existed in these subjects a significant correlation between changes in cell size (polymegathism) and cell shape (pleomorphism).
Adult↗
Overnight corneal swelling response in adapted and unadapted extended wear patients.
This investigation compared the overnight swelling response in adapted and unadapted subjects who were wearing a 0.035 mm, low water content hydrogel contact lens. Six subjects who had not worn contact lenses previously (unadapted) and six subjects who had worn extended wear hydrogel lenses for 1.5 years participated in the study. Baseline corneal thickness measurements were taken in the evening and after 7.5 h of sleeping with the lenses on overnight. The unadapted subjects showed more overnight swelling and at each time interval for 3 h the next morning under open-eye conditions. The rate of deswelling was the same for each group.
Adaptation, Physiological↗
Chronic solar radiation exposure and endothelial polymegethism.
Acute exposure of ultraviolet radiation to the cornea has previously been shown to produce endothelial pleomorphism and polymegethism. The reciprocity of exposure intensity and duration typically seen with the photochemical effects of ultraviolet radiation on biological tissue predicts a similar effect with chronic exposure. This was tested by comparing the regularity of the hexagonal endothelial mosaic for a group of workers (n = 9) chronically exposed to solar radiation to that for an age-matched control group (n = 18). Although the mean cell area of the endothelium was similar between groups (p greater than 0.10), a significant difference (p less than 0.01) was demonstrated in the degree of polymegethism. This supports the contention that chronic ultraviolet radiation exposure may contribute to increased polymegethism seen with age.
Adult↗
A theory of corneal endothelial polymegethism and aging.
An analysis of the corneal endothelium of a 23 year old female who had never worn contact lenses but who had unilateral ptosis, showed marked endothelial pleomorphism of the cornea underneath the closed lid. Since corneal hypoxia has been shown to produce corneal endothelial polymegethism in contact lens wearers, and since hypoxic conditions exist under the closed lid, it is reasonable to assume that the polymegethous endothelial changes which occur with aging are a result of chronic corneal exposure to hypoxic conditions under the closed lid during sleep. Corneal hypoxia is apparently not the cause of declining endothelial cell density with age.
Adult↗
Contact lens wear and the corneal endothelium.
Contact lenses produce transient and permanent effects on the corneal endothelium in relationship to the lens oxygen transmissibility and how the contact lenses are worn. There is concern, as well as growing evidence, that contact lens-induced corneal endothelial pleomorphism causes a reduction in the endothelial functional capacity. This, in turn, may place an eye at risk for uncontrolled corneal swelling if the eye is under sufficient environmental or surgical stress. Use of lens materials and designs which promote high oxygen transmissibility, and patient wear of lenses during waking hours only, are ways to slow the development of permanent corneal endothelial pleomorphism.
Contact Lenses↗
Corneal endothelial polymegathism induced by PMMA contact lens wear.
Central corneal endothelial photographs were taken for 15 persons who had worn polymethylmethacrylate (PMMA) contact lenses for 7-15 yr and for a nonwearing control group matched for age and sex. An individual cell area analysis was made from the cell tracings. Significant endothelial polymegathism was noted for each member of the contact lens wearing group. PMMA wearers showed an average coefficient of variation of 0.445 for central corneal endothelial cell area compared to 0.245 for nonwearers (81.6% increase in polymegathism). The average maximum/minimum cell size ratio was 8.06 for the PMMA wearers vs 3.42 for the nonwearing control group. The frequency distributions for the cell areas reveal that the contact lens wearer develops cells that are much smaller and larger than normal.
Adult↗
Human corneal epithelial oxygen demand--population characteristics.
Observed differences in corneal response to contact lens wear have been attributed to variations in individual corneal oxygen requirements. Anterior corneal oxygen flux was measured on 100 human eyes using a polarographic oxygen sensor to determine if differences could be measured among subjects. A distribution in corneal epithelial oxygen use was found to exist in the population.
Adolescent↗
Solubility effects on corneal oxygen measurement.
Various membrane materials have been attached to oxygen sensors during measurement of corneal oxygen uptake. Differences in the oxygen solubility characteristics of these membranes directly affect resulting flux values. Human corneal epithelial oxygen uptake values were obtained using an oxygen sensor in conjunction with polyethylene, Teflon, and polypropylene membranes attached to its tip. Conversion coefficients were calculated to relate findings obtained with each membrane-sensor system. New solubility constants were derived for polyethylene, Teflon, and polypropylene based on previous findings obtained with a saline (hydrophilic lens) membrane reservoir.
Cornea↗
Corneal thickness changes associated with daily and extended contact lens wear.
Human corneal thickness was measured during daily wear of hydrogel contact lenses and then during the initial 2 weeks extended wear of hyper-thin (0.035 mm), low water content (38.6%), hydrogel lenses (polymacon). Results show that subjects wearing standard thickness (0.12 mm) and ultra-thin (0.07 mm) hydrogel lenses of low water content for daily wear will exhibit a diurnal swelling of the cornea. Subjects wearing hyper-thin (0.035 mm) low minus power hydrogel contact lenses of low water content for extended wear will exhibit overnight (closed eye) swelling of the cornea followed by a deswelling throughout the day (open eye). The degree of swelling and deswelling can vary greatly among individual subjects.
Circadian Rhythm↗
Transient endothelial changes produced by hydrophilic contact lenses.
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Adaptation, Ocular↗
Flatter than "K," on "K," steeper than "K": does the cornea know the difference?
Twenty-nine subjects were fitted with PMMA contact lenses of equal overall diameter, optical zone diameter, and z-value in a double-masked clinical trial. Five different treatment groups were analyzed and a one-way analysis of variance was used to determine whether significant differences in corneal thickness change existed between the treatment groups. Lenses fitted 1 D flatter than "K" caused the least amount of corneal thickness change.
Contact Lenses↗
Measurement of corneal oxygen uptake.
Because of the importance of the rate of oxygen uptake by the cornea, various techniques have been used to measure the oxygen utilization. A probe covered by a polyethylene membrane can be placed against the unanesthetized cornea and the rate of change in oxygen tension recorded. The rate can be converted to indicate the rate of oxygen flow from the polyethylene membrane to the cornea.
Contact Lenses↗
Corneal endothelial response to rigid contact lenses.
Through modifications of the Nikon slitlamp, a system for repeatable central corneal endothelial photography was devised using the Holden-Zantos technique. The time course of the endothelial bleb response was charted for rigid contact lens wear and was found to reach a maximum at 10 to 50 min after lens insertion in the unadapted eye.
Contact Lenses↗
Disparity-induced vergence responses in normal and strabismic subjects.
Latencies of vergence responses were obtained by presenting vertical line stimuli for 0.5 sec to the fovea of one eye and to various retinal locations of the other eye of four subjects with normal binocular vision, one exotrope with normal retinal correspondence, and four esotropes with anomalous correspondence. Vergence latencies were larger for squinters than nonsquinters and were especially long for the squinters with anomalous correspondence. For three of the four anomalous corresponders, the direction of the vergence movement (convergence or divergence) was based on the location of the stimulus with respect to the anomalous retinal point in the deviating eye--not with respect to the fovea as occurred for the subjects with normal correspondence.
Esotropia↗