ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Contact lenses can be a practical and visually efficient corrective modality in aqueous surface and subsurface environments. Even though contact lenses have many advantages for the ametropic individual, in certain situations there may also be disadvantages such as the risk of lens loss, ocular injury, or infection. In order to be able to wear contact lenses in these environments both prescribing practitioners and contact lens wearers must know when the risks of contact lens wear in these environments are minimal. In addition, they must know what precautions to take to minimize risks.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

We compared the theoretical peripheral power errors and oblique astigmatism of eyes corrected with commercially available intraocular lenses (lOL's) with experimental data of normal phakic eyes. The peripheral power errors and the oblique astigmatism of the pseudophakic eye are larger than those of phakic eyes. The most sensitive component of the optical system of the pseudophakic eye to the peripheral power errors is the shape of the IOL, but only if the lens is away from the iris. The corneal and the retinal surfaces do not affect the peripheral power errors and oblique astigmatism significantly. A plano-convex lens with the flat surface facing the cornea gives the least peripheral power errors and oblique astigmatism and thus the value closest to the experimental data of phakic eyes. However, this design does not give the minimum spherical aberration. Therefore, eyes corrected with lOL's are expected to have poorer peripheral retinal image quality than normal phakic eyes.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The study complements and extends our previous investigation and reports that late-onset myopes (LOM's, N=15) exhibit differences in adaptation of tonic accommodation (TA) to sustained visual tasks when compared to emmetropes (EMM's, N=15). Pre- and posttask TA was measured with a modified Canon R-1 objective infra-red optometer under darkroom conditions. Post-task TA was measured immediately after a 10-min counting task and at 1-s intervals over a period of 90 s; the task was located at distances equivalent to 1, 3, and 5 D. The pattern of regression back to the pre-task TA level was used to assess the degree of adaptation generated by the task. The data indicate substantial differences between regression patterns for EMM's and for LOM's which were enhanced as accommodation stimulus levels increased. Using a twofactor split-plot analysis of variance, statistically significant differences between EMM's and LOM's could be attributed to the rates of change of post-task accommodative levels to pre-task TA levels for both the 3 and 5 D tasks.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

We investigated task variables that may influence the incidence of visual discomfort amongst subjects who routinely spent a proportion of their day working with visual display terminals (VDT's). A diary was kept by subjects over five consecutive working days, in which they recorded visual symptoms, the visual tasks undertaken, the amount of time spent on workbreaks, work pressure, work interest, and personal moderating factors which may have influenced the symptoms recorded. The symptoms recorded by subjects were then treated as dependent variables in multiple regression analyses with the diary findings (task-related factors) as independent variables. The incidence of some types of symptoms was significantly associated with specific categories of work tasks, personal moderating influences, work pressure, work interest, time of day, and day of week.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Using a computer plotting technique, we designed four variable-contrast visual acuity charts. The contrast of the first 3 is 90, 15, and 2.5%, respectively. The fourth is 90%, but the luminance of the optotypes and background are the reverse of the first chart. The main features of these charts are as follows. Both contrast sensitivity and spatial frequency are in geometric gradation, which observes the laws of Weber and Fechner. The mean average luminance, (Lmax+ Lmin)/2, is constant for all four charts, which follows the concept of contrast sensitivity function (CSF). Charts 1 and 4, which have the same contrasts but different glare backgrounds, measure the glare that is related to the transparency of the refractive media of the eye. Because the charts are rotatable, patient memorization and guessing are minimized. Results compare with those of the conventional visual acuity test and are understandable by patients and eye care practitioners. The charts, which are simple, easy, and require little time, are inexpensive and portable.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Farnsworth's standard D15 and L'Anthony's desaturated D15 panel tests were administered to 99 congenital red-green color defective subjects. The results were analyzed in three ways: (1) by summing the color differences between adjacent caps according to Bowman, (2) by averaging color difference vectors (CDV) according to Vingrys and King-Smith, and (3) by visually inspecting and counting the crossings. The Bowman measure was highly correlated with one of the CDV measures but provides less information regarding a cap arrangement. The desaturated D15 test can be expected to misclassify 5% of dichromats by type (protan/deutan) compared to a type misclassification rate of <0.1% for the D15 panel test. The correct diagnostic rates for type were 45% for the standard D15 test and 58% for the desaturated D15 test. However, the improvement in correct diagnostic rate for the latter test was accompanied by an increase in the misdiagnostic rate from 2 to 10%. The main value of the desaturated D15 test in congenital color vision diagnosis would seem to be in providing classification of those subjects who pass the standard D15 test. Quantitative scoring of the tests provides a good estimate of severity of defect. Visual inspection provides a similar diagnostic rate to CDV analysis, but has a lower type misdiagnostic rate at the desaturated D15 test and is more likely to be correct when the two methods disagree. We suggest that quantitative scoring techniques are of limited benefit for the clinical diagnosis of congenital color vision defects but that they are of use in clinical trials or for the monitoring of changes in color vision over time. A protocol for the clinical use of panel D15 tests in detection and diagnosis of congenital color vision defects is suggested.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Previous studies measuring accommodative facility have been confined to young adults and children. Standard test procedures were used to measure interactive facility (i.e., binocular accommodative flip test) in a sample of 45 adults from 30 to 42 years of age. The results showed a marked reduction in the average number of cycles per minute performed for the ±2.00 D flip test. Symptoms in the sample were also tabulated and their relation with interactive facility investigated. We found no direct relation between symptoms and accommodative facility. Further studies are needed to establish normative data for accommodative facility for adults approaching presbyopia.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

We present five case reports of the clinical manifestations of talc retinopathy. Photographs illustrate the typical intravascular location of these crystalline deposits which are evident only after repeated injections of street drugs. Discussion includes differential diagnosis, systemic complications, and ophthalmic management of this condition.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The effect of diet on tear function is illustrated clearly by malnutrition-induced xerophthalmia. Dietary habits in well nourished North American society have been implicated as a cause of some tear dysfunction. A review of the ocular literature suggests that sufficient dietary protein, vitamins A, B6and C, potassium, and zinc may be necessary for normal tear function. Excesses of dietary fats, salt, cholesterol, alcohol, protein, and sucrose have been associated with or suggested as causes of tear dysfunction. No unequivocal link has been established between diet and remission of dry eye states in a well nourished population.

ISSN:1040-5488    

出版商:OVID    

年代:1991

数据来源: OVID