Through-focus visual performance measurements and predictions with multifocal contact lenses

We measured high-contrast visual acuity (VA) and 12 c/deg contrast sensitivity (CS) through-focus functions (TFF) of four eyes of four cyclopleged subjects in three conditions: naked eye, with a center-distance and center-near Proclear® multifocal addition 2D contact lens. In all conditions, an adaptive optics system statically compensated the astigmatism of the subject’s eye alone. Multifocal contact lenses enlarged the width of the curve of through-focus visual performance but reduced the peak performance. We investigated the ability of image quality metrics based on wave-aberration measurements to predict VA and CS TFF. CS₁₂ metric through-focus and measured through-focus contrast sensitivities were well correlated (r² = 0.74). Even if visual acuity metrics were often poorer than measured ones, the shapes of the measured through-focus curves and rMTFa_5-15 through-focus were quite comparable (r² = 0.67).     

Kinetic visual disturbances with contact lenses

Kinetic (variable) visual disturbances in contact lens wearers may be generated optically or mechanically. These disturbances are categorized in two groups: 1) those affecting both phakic and aphakic contact lens wearers; and 2) those peculiar to aphakic patients. Within each category disturbances vary with the types of lens used. In this review, the optical and mechanical bases for the various problems are discussed, as are possible solutions. It is emphasized that the ophthalmologist prescribing contact lenses should be aware of the patient's work hazards and requirements, and weight the advantages and disadvantages of contact lenses. For example, is the patient exposed to high temperatures, heavy or fast-moving equipment, altered barometric conditions, etc.? Is physical exertion required? Employers and fellow workers should be aware of the contact lens wearers in their work force.     

Prolonged-wear contact lenses in aphakia

While prolonged wear of contact lenses is possible for the aphakic patient, careful consideration must be given to patient selection and to the potential complications of such use. Currently available lenses are far from ideal and, if used at all, must be carefully monitored. The newer lenses, specifically designed for extended wear, more closely fit our needs. Several manufacturers are testing their devices under strict FDA supervision. FDA guidelines dictate a minimum of two years follow-up before a determination will be made as to which lenses are safe and effective enough for prolonged wear in aphakic eyes.     

Extended-wear lenses. An update

Extended-wear lenses present problems to be overcome by both the lens fitter and the patient. Guidelines are given for selecting patients and lenses, fitting the lenses, educating the patient, and handling complications. It is emphasized that patients who are happy with their day-wear lenses should not be urged to change to extended-wear lenses, and that if extended-wear lenses are worn, conscientious followup is crucial.     

The influence of lens conditioning on signs and symptoms with new hydrogel contact lenses

Background: Daily disposable contact lenses are considered to be the pinnacle of safe contact lens wear, yet it has been suggested that it takes some period of wear for the lens surface to reach optimal compatibility with the ocular surface. This study assesses the influence of brief treatment with a conditioning drop on the ocular response to new contact lenses over a single day of wear. Methods: The study was a single‐masked, paired (contralateral) comparison of the signs and symptoms with wear of new Acuvue 2 contact lenses pretreated with a conditioning agent containing carboxymethylcellulose (carmellose, CMC) against new lenses inserted directly from the blister pack. Sixty‐one subjects participated in the study, of whom 59 were considered eligible for data analysis. Subjects were also divided into symptomatic and asymptomatic lens wearers based on their overall comfort level in lens wear. Symptoms and signs were recorded at lens delivery and following eight hours of wear. Results: A set of slitlamp signs, comprising corneal staining (p < 0.05), limbal redness (p < 0.05), bulbar conjunctival hyperaemia (p < 0.05), bulbar conjunctival staining (p < 0.01) and palpebral conjunctival redness (p < 0.05) showed small but statistically significant (p < 0.05) end‐ofday mean values in favour of the lens that was conditioned with the rewetting agent. These data were supported by the proportion of subjects showing lower gradings with conditioned lenses versus unconditioned lenses, as follows: corneal staining (35 per cent versus 12 per cent, p <0.05), limbal redness (43 per cent versus 22 per cent, p < 0.05), bulbar conjunctival hyperaemia (50 per cent versus 15 per cent, p < 0.05), bulbar conjunctival staining (46 per cent versus 30 per cent, p < 0.1) and palpebral conjunctival hyperaemia (28 per cent versus 17 per cent, NS). For those subjects reporting symptoms with lens wear (n = 12), there was a statistically significant (p < 0.05) preference in terms of comfort as a result of preconditioning. Conclusions: The results of the investigation suggest that use of a conditioning agent can provide a more physiologically suitable environment for a new lens, thereby reducing the clinical signs associated with lens discomfort. The protocol used here, which is based on a statistical paradigm using standard pictorial grading scales, allows high sensitivity in detecting small changes in ocular parameters.     

关于接触镜专用标准透镜的探讨

目的：证实采用接触镜专用标准透镜组标实的焦度计不能准确测定被测角膜接触镜的顶焦度。方法：①认识焦度计测定值的属性,从而分析目前采用通用的标准透镜组标定的焦度计何以不能表征接触镜专用标准透镜组的顶焦度。②比较接触镜专用标准透镜组与角膜接触镜的参数差异,从而分析采用接触专用标准透镜组标定的焦度计何以不能测定角膜接解镜的顶焦度。结果：以采用接触镜专用标准透镜组标定后的焦度计为尺度来检测和规范角膜接触镜的顶焦度,无论远视还是近视焦度都会降低,导致配戴眼视力下降。结论：采用接触镜专用标准透镜组标定的焦度计检测接触镜顶焦度的作法值得商榷。     

Aspheric contact lenses used to control convergence excess

A 15-year-old female patient presented wearing progressive addition spectacle lenses to help control a condition of convergence excess. She was fitted with aspheric, multifocal, rigid gas permeable contact lenses for cosmetic reasons. The lenses were fitted 1.5 dioptres steeper than the flatter keratometer reading, and incorporated an eccentricity value of 0.7. Visual acuities through these lenses were 6/7.5 at both distance and near in each eye. Phorias through the lenses were measured using two methods. The cover test revealed 1 D of esophoria at 6 m and 3 D of esophoria at 40 cm. The Maddox rod also yielded 3 D of esophoria at 40 cm. (Clin Exp Optom 1993; 76.4: 141–142)     

Visual performance with simultaneous vision multifocal contact lenses

Purpose: The aim was to assess visual performance after PureVision high addition multifocal contact lens (PM) fitting through contrast sensitivity measured under different illumination levels for both distance and near. Methods: In a cross‐over study, 20 presbyopic patients were randomly assigned to PM or spectacles. Near contrast sensitivity was measured with the Vistech VCTS 6500 system. Distance contrast sensitivity and distance visual acuity (VA) were measured with the Functional Vision Analyser under photopic (85 cd/m²) and mesopic (3.0 cd/m²) conditions, the latter also under two levels of induced glare: 1.0 lux and 28 lux. Near VA was measured by logMAR charts under approximately 80 cd/m² luminance settings. Results: Average monocular spectacle corrected and PM VA were ‐0.02 ± 0.05 and 0.03 ± 0.05 logMAR for distance photopic, 0.16 ± 0.10 and 0.23 ± 0.07 logMAR for distance mesopic and ‐0.03 ± 0.05 and 0.05 ± 0.06 logMAR for near photopic, respectively. Average binocular spectacle corrected and PM VA were ‐0.05 ± 0.07 and ‐0.01 ± 0.03 logMAR for distance photopic, 0.10 ± 0.06 and 0.18 ± 0.05 logMAR for distance mesopic and ‐0.08 ± 0.06 and 0.02 ± 0.05 logMAR for near photopic, respectively. Statistically significant differences were found between the contrast sensitivity with the two types of correction for both distance and near, with spectacle correction being better in all cases. Conclusion: PureVision multifocal contact lenses preserve good VA and good visual performance under real‐life conditions.     

色盲隐形眼镜矫正色觉障碍的临床研究

目的 :观察研究色盲隐形眼镜矫正色觉障碍患者的辨色能力。方法 :用色盲检查图谱 ,在自然或日光灯下 ,检查佩戴色盲隐形眼镜前后的辨读正确率进行统计分析 ,观察矫正效果。结果 :3 6例患者除了 2例无效外 ,3 4例有效 ,有效率占 90 % ,平均提高识别率 2 4 48%± 10 63 %。结论 :色盲隐形眼镜矫正色觉障碍中的红、绿色盲和色弱患者是有效、安全的 ,而且与患者的严重程度有关 ,色盲越严重 ,提高识别率就越高。     

Tear film,contact lenses and tear biomarkers

This article summarises research undertaken since 1993 in the Willcox laboratory at the University of New South Wales, Sydney on the tear film, its interactions with contact lenses, and the use of tears as a source of biomarkers for ocular and non‐ocular diseases. The proteome, lipidome and glycome of tears all contribute to important aspects of the tear film, including its structure, its ability to defend the ocular surface against microbes and to help heal ocular surface injuries. The tear film interacts with contact lenses in vivo and interactions between tears and lenses can affect the biocompatibility of lenses, and may be important in mediating discomfort responses during lens wear. Suggestions are made for follow‐up research.