摘要:

AbstractThe only practical means of making a clinical measurement of oxygen flux into a cornea under a contact lens is by pressing a Clark-type oxygen sensor to the anterior surface of the lens. The earlier limitation to lenses of low water content has been removed and a general method suitable for soft lenses of all transmissibility is presented here. The procedure allows an estimate of oxygen tension under the lens and oxygen flux into the cornea. The method requires a minimum amount of calculation and does not require a prior calibration on the contact lens wearer, but instead gives a direct, absolute measurement of oxygen tension and flux.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractThis study examined the short-term hydration changes of hydrogel contact lenses with wear. Changes in the water content of 12 new Bausch & Lomb hydrogel contact lenses were calculated from the change in weight of the lenses after they were worn. The mean of the calculated water contents after wear was 27.9%. This compares with the 38.6% water content of new, fully hydrated lenses.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractMost ophthalmic preparations contain preservatives. Some are toxic to healthy corneal epithelium or retard healing of corneas from which part or all of the epithelium has been removed leaving an intact basement membrane. In this paper, the effect of commonly used concentrations of benzalkonium chloride (BAC), thimerosal, and ethylenediaminetetracetic acid (EDTA) upon the healing of rabbit corneas after partial lamellar keratectomy is investigated. This model has not been used previously for a study of preservative toxicity. Thimerosal (0.004%), BAC (0.01 %), or EDTA (0.1%) applied four times per day had no significant effect on the corneal healing or epithelial migration rates. A slight retardation occurred when BAC (0.01%) and EDTA (0.1%) were used together, while healing failed to occur as long as benzalkonium chloride (0.02%) was administered.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractThe effect of a variety of vergence training procedures on the visual system of 35 asymptomatic young adults with normal binocularity was evaluated. The visual training took place on the weekdays of three consecutive weeks. Vergence ranges were measured before the study began and at the end of the 3-week period. Subpopulations were evaluated at one week and at 6 months to document further the course of the effects. Positive fusional vergence training significantly increased the vergence ranges after 1 week of training; a greater effect was measured after 3 weeks. The vergence capability was found to have decreased 6 months later, but the effects of the training were still apparent. Negative fusional vergence training was less effective; however, significant increases were demonstrable after 3 weeks of training. The phorias and accommodative amplitude were not affected by the orthoptics. We conclude that relatively short periods of training can provide long-lasting increases in the vergence ability of a group of binocular normals. The implications of such findings relative to possible neural control mechanisms and clinical visual training situations are discussed.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractA group of 15 subjects were fitted with truncated toric soft lenses varying in cylinder power from 1 to 4 D, in 1 D steps, with axes 90 and 180°. After 30 min of wear, the location of the truncation was measured from a slitlamp photograph and calculated from a spherocylindrical over-refraction. Blink-initiated rotation of the lenses was measured by slitlamp photography. Comparison of the location of the truncation of lenses with cylinder at axes 90 and 180° showed no significant difference using matched pair analysis, nor was cylinder power found to effect truncation location. However, analysis of the incidence of acceptable location (truncation within 25° of the horizontal) showed significantly more acceptable locations for those toric lenses with the cylinder at axis 90° (against-the-rule). A significant product moment correlation between the amount of mislocation of the axis and blink-initiated rotation was found. A high correlation was found between axis location measured from photographs and that calculated from over-refraction. However, because of the large variance of the differences between the two values, over-refraction is not considered to be a clinically acceptable method of determining toric lens axis location. The significance of the results of this study are discussed with respect to toric lens design.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractMonocular Estimate Method (MEM) dynamic retinoscopy is an objective clinical method for determining the accommodative response to a fixed accommodative stimulus. Although MEM has been used in many clinical investigations, it has never been compared with the measurement of accommodative response by. the haploscope. This report compares the accommodative responses obtained by MEM and by a haploscopic instrument, the phoroaccommodometer. Linear regression analysis indicates that MEM consistently provides a close approximation to the phoroaccommodometer finding (r = 0.975, p ≤ 0.001). A conversion table has been generated so MEM findings may be adjusted to correspond with the phoroaccommodometer at higher stimulus values.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractWhen equally spaced, vertical, parallel straight lines are rotated about a horizontal axis perpendicular to the plane of the grid, the horizontal separation between the lines increases with the angle of rotation. With the grid presented binocularly, the increase in horizontal separation between the lines can be used to measure the vergence limits of subjects. Results obtained by this method were compared with those obtained by Risley prisms and by a haploscope. The new method has advantages over the traditional methods: it is not affected by the aberrations and distortions generated by prisms and it presents a more natural stimulus situation than the tubular haploscope.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractLaser speckle stimuli were used to examine the contribution of the central retina to the visual evoked response (VER). The foveally fixated test stimuli were either small circular spots or annular targets with dark centers. The speckle elements were shifted seven times per second. Reliable responses could be recorded for even the smallest (1°) target size. In addition, it was clearly evident that for spots up to 5° in diameter, VER amplitude increased linearly with stimulus area. However, data from annular targets revealed that this result was not strictly dependent upon stimulus area. In many instances, large annular stimuli evoked responses with smaller amplitude than spot stimuli with less area. This result may be due to a center-surround antagonistic interaction. These experiments suggest a potential value for laser speckle VER techniques in the assessment of discrete lesions of the macula.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractThe relation of accommodative to visual-motor perceptual abilities was investigated. Patients between 5 and 13 years of age manifesting both accommodative and visual-motor perceptual deficits were given accommodative therapy. The effect of this therapy was analyzed, and the results indicated that improvement in the visual and motor perceptual abilities occurred in the 5 to 7 years, 11 month age group.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID

摘要:

AbstractPrevious investigators have shown that thin polymethyl methacrylate (PMMA) contact lenses (≤0.12 mm) flex on toric corneas, thereby altering the residual astigmatism. The present study was designed to evaluate the flexure and residual astigmatism of gas permeable Polycon contact lenses on toric corneas and compare the results with those obtained with PMMA lenses on the same corneas. Eight subjects (16 eyes) with corneal toricities ranging from 1.25 to 4.25 D wore four pairs of identical Polycon and PMMA lenses. The only lens parameter that varied was center thickness, which ranged from 0.07 to 0.16 mm. Flexure and residual astigmatism were measured on all corneas with all lenses in a double-masked fashion. Our results indicate that Polycon lenses undergo significantly more flexure and alter residual astigmatism more on toric corneas than PMMA lenses at all center thicknesses evaluated. For both materials, flexure and residual astigmatism increased as center thickness decreased. The clinical implications of these findings are discussed.

ISSN:0093-7002    

出版商:OVID    

年代:1982

数据来源: OVID