摘要:

Records were selected from a data pool of myopic private practice patients to study the relation of refractive error change and keratometer power change in young adulthood. Selection was on the basis of three or more refractions and keratometer readings at and/ or after 18 years of age. There were significant correlations between rate of myopia progression and rate of keratometer power change. Linear regression slopes of rate of refractive error change on rate of keratometer power change were in the neighborhood of 0.7. These findings were in contrast to the lack of correlation between myopia increase and corneal steepening in childhood myopia progression. Young adulthood myopia progression also appeared to be accompanied by a slight tendency toward a with-the-rule astigmatic shift.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

In a randomized clinical trial designed to test the efficacy of bifocal lenses for the control of juvenile myopia, each of 207 children between the ages of 6 and 15 years wore single vision lenses, +1.00 D add bifocals, or +2.00 D add bifocals for a period of 3 years. For the 124 subjects who completed the study, the mean changes in refraction were found to be −0.34 D per year for subjects wearing single vision lenses, −0.36 D per year for those wearing +1.00 D add bifocals, and −0.34 D per year for those wearing +2.00 D add bifocals. These differences were not statistically significant. When subjects in all three treatment groups were combined, it was found that the rate of progression tended to be the most rapid for subjects who entered the study at an early age with a large amount of myopia, and tended to be the least rapid for subjects who entered the study at a later age with a small amount of myopia. It was also found that subjects having with-the-rule astigmatism progressed more slowly than those having no astigmatism or against-the-rule astigmatism.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

An objective infrared optometer was used to investigate the influence of cognitive demand on tonic accommodation (TA) for two groups of young emmetropes (N = 15) and late-onset myopes (N = 15). TA was measured under a passive condition and while subjects carried out a reverse counting task. The TA of myopes under the passive condition (mean = 0.81 D, SD= 0.46 D) was shown to have lower values than the TA of emmetropes (mean = 1.14 D, SD = 0.46 D). For the myopic group the counting task induced a positive shift in TA (mean = +0.35 D, SD = 0.31 D) that was significantly higher than that for the emmetropic group (mean = +0.07 D, SD = 0.27 D). The implications for theories of refractive error development are discussed.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Color constancy refers to the phenomenon that the perceived colors of objects are largely unaltered by changes in the illuminant or by viewing through colored filters. Deviations from perfect constancy, induced by filters similar to ophthalmic tints, were investigated in this study. Munsell color chips were forced-choice categorized into R, Y, G, or B. This accurately located the boundaries between these colors on the chip color circle. Testing was performed through 23 different adaptive conditions and chromaticity shifts created by filters. The technique simulates real world situations in which the chromaticity of the objects and the adaptation of the observer both change. Generally, color constancy held quite well. The boundaries between the four colors shifted for some filters, indicating some deviation from perfect constancy. Red filters resulted in more color chips appearing red, blue and green filters resulted in more chips appearing blue, and filters along the Planckian locus resulted in more chips appearing green.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Fixation disparity has been shown to be produced by prism stress, and it has therefore been proposed that its presence constitutes a sign that binocular vision is under stress (de-compensated heterophoria). Fixation disparity can be present in the absence of any other indication of stress, and therefore may have a physiological basis. This study investigates the effect on fixation disparity and visual discomfort of placing the visual system under a different type of stress, that of requiring the subject to read under conditions of inadequate illumination. In 50 young adults, it was found that fixation disparity increased under inadequate illumination and that this was accompanied by symptoms in the form of visual discomfort. After a period of rest from any near-vision task, the fixation disparity decreased and the symptoms were reduced.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Contrast sensitivity functions and complete eye examinations were obtained from 103 normal, healthy young adults (ages 21 to 40 years). Descriptive statistics were compiled for the group in order to provide normative information. Subsets of the population were evaluated with respect to the relations among the attributes of accommodation, visual acuity, refraction, spectacle wear, and contrast sensitivity. The influence of age in this restricted population was seen only at 16 cpd. In those subjects with better than 6/6 (20/20) Snellen acuity, there were statistically significant relations with the parameters of the contrast sensitivity function as compared to those observers with 6/6 (20/20) or poorer acuity. High spatial frequency resolution was significantly better for those observers with better than 6/6 (20/20) acuity in either eye. In addition, this study provides a broad base of normative data for variability from a large population confined to a specific age range and with refractive errors that ranged from minimal to more than average.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

Lid pressure may affect corneal curvature. A change in lid pressure due to a Meibomian cyst may cause a change in corneal topography and possibly in refractive status. External infection or epithelial surface disruption may affect the stability of the precomeal tear film by causing changes in tear formation or an increase in the rate of evaporation of water from this film. This report concerns a male patient who showed changes in corneal topography and tear film stability due to a Meibomian cyst.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

This report compares the refractive status, visual acuity, binocular status, vergence/accommodation facility, perceptual skills, and ocular health of 261 children with learning difficulties (LD) and 496 No-LD children, all between the ages of 6 and 12 years. Data reveal that among conditions diagnosed routinely by optometrists, hyperopia and perceptual skills dysfunction were more prevalent in LD children and myopia in No-LD children. No other significant between-group differences were found.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID

摘要:

We studied the extent of dehydration of hydrogel lenses during overnight wear. Seven subjects used a hand refractometer to measure the water content of five different lenses (Hydron zero-6 (nominal water content 38.6%), −0.50 D; Snoflex 50 (52.5%), −0.50 and +15.00 D, and Hydron Z-67 (67.5%), −0.50 and +15.00 D) before and after 7 h of both open- and closed-eye wear. No statistically significant difference was observed in dehydration between open and closed eye lens wear. Thick and thin lenses made of the same material were found to dehydrate to an equal extent. Contrary to expectations, the medium water content Snoflex 50 lenses displayed a greater absolute decrease in water content than the higher water content Hydron Z-67 lenses (p < 0.01). Factors that may influence the extent of dehydration under open- and closed-eye wearing conditions, and the clinical implications of these results, are discussed.

ISSN:0093-7002    

出版商:OVID    

年代:1987

数据来源: OVID