ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Purpose.Some knowledge of the orientation position of toric soft lenses is required as part of the fitting process. Although it is known that factors such as lid anatomy, lens design, and fit are important, there is little detailed understanding of how these relate to toric lens orientation. The purpose of this study was to evaluate various patient and lens factors that might influence toric soft lens fit and to determine the predictor variables for lens orientation.Methods.This was a clinical study in which 45 subjects were fitted with a prism-stabilized, mid-water, cast-molded, back surface toric soft lens. The lens was representative of commonly used designs for frequent replacement toric soft lenses. Patient and lens fit variables were assessed, including a range of lid topography features, which were measured using a digital photographic technique.Results.The main patient factors associated with lens orientation and stability were degree of myopia, palpebral aperture, and several angles relating to lid anatomy. Greater upward incline of the temporal lids was associated with increasing inferior-temporal lens orientation; lower myopia and smaller palpebral aperture size were associated with more stable lens orientation. The principal lens fit characteristics affecting lens orientation were postblink movement and lens tightness. Less movement was associated with more stable lens orientation, and increased tightness was associated with slower reorientation speed. Weaker but significant correlations were also shown between a number of other patient and lens variables.Conclusions.A number of patient factors and lens fit characteristics influencing toric soft lens orientation were identified. The findings fall short of allowing practitioners to accurately predict toric lens orientation; however, they do provide some factors to consider when fitting toric soft lenses.

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Purpose.The purpose of this study was to determine the factors that contribute to corneal staining in hydrogel lens wearers by examining the following variables: type of lens worn, wearing time and lens replacement schedule, lens care system, and topical and systemic medication use.Methods.Five hundred full-time, successful hydrogel contact lens wearers were evaluated for corneal fluorescein staining at 20 clinical sites. Corneal staining was evaluated in five regions and was graded on a scale of 0 (no staining) to 4 (severe staining) in 0.5 steps for severity.Results.Corneal fluorescein staining was present in at least one eye in 55.7% of the hydrogel lens wearers examined in this study, and 8.0% had moderate-to-severe staining (defined as a cumulative staining score of ≥3 with at least one quadrant score ≥2). Staining was most severe for the inferior portion of the cornea (mean ± SD; OD: 0.34 ± 0.57, OS: 0.30 ± 0.54). All other areas of the cornea showed lesser amounts of staining, all of which were approximately equal (mean range, 0.13 to 0.16). Staining was observed in two or more quadrants in 24% of right eyes and 22.4% of left eyes. When questioned about care system compliance, 81.1% of subjects reported compliance. Patients who were noncompliant with their lens care system (&khgr;2p = 0.0037), used rewetting drops (&khgr;2p = 0.0005), or wore conventional lenses without a planned replacement schedule (&khgr;2p = 0.0008) were more likely to have some degree of corneal staining. Noncompliance with care system (&khgr;2p = 0.0147), replacement schedule (&khgr;2p = 0.0039), and lens power (&khgr;2p = 0.0224) were associated with moderate-to-severe staining. The following factors were not significantly associated with corneal staining: patient age, gender, medication use including oral contraceptives, type of wear (extended, flexible, or daily), average wearing time, wearing time at the examination, lens type (spherical or toric), water content of lenses (high or low water content), type of care system, use of enzymes, and pinching the contact lens directly off the cornea.Conclusions.Staining occurs to some extent in many hydrogel contact lens patients, and is influenced by many factors. Moderate-to-severe staining, which may be more clinically significant, is associated with noncompliance with care system, a conventional replacement schedule, and lens power.

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Population-based vision screening studies of the prevalence rate of low vision and blindness in the U.S. are reviewed to evaluate the sources of disagreement among studies. The major reasons that studies disagree on prevalence rate estimates are differences in best-corrected visual acuity criteria for low vision and differences in the age range of the oldest age category. When corrections are made for these differences, the results of all prevalence rate studies, except the Mud Creek Valley Study, fit the same prevalence rate vs. age function. The greater prevalence rate of low vision and blindness for each age category that was observed in the Mud Creek Valley Study can be attributed to the higher prevalence rate of cataract associated with a paucity of health care services in the Mud Creek Valley population. The time-derivative of the prevalence rate vs. age function fit to the data provided an estimate of the annual incidence rate of low vision and blindness vs. age. The estimated annual incidence agreed with estimates from unpublished 8-year incidence data of the Baltimore Eye Survey. The incidence rate of low vision and blindness for Americans aged 40 to 60 years is higher among blacks than among whites. For Americans greater than age 60 years, the incidence rate for whites exceeds that for blacks. This observation probably reflects the different natural histories of glaucoma, a leading cause of low vision and blindness among black Americans, and age-related macular degeneration, a leading cause of low vision and blindness among white Americans. Using the age-dependent models of prevalence rate of low vision and blindness for white and black populations, an estimated 1.5 million Americans over age 45 years have a best-corrected visual acuity in the better eye that is ≤20/70. Based on the incidence rate estimates, approximately 240,000 new cases of low vision and blindness occur each year. With the aging of the U.S. population, that number is expected to double over the next 25 years.

ISSN:1040-5488    

出版商:OVID    

年代:2002

数据来源: OVID