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PubMedDate not supplied

[Physiological mechanisms of the etiology of visual fatigue during work involving visual stress].

Physiological parameters of vision were studied in three professional groups (a total of 1204 subjects): microscope operators, subjects working with magnifying glasses, and computer users. General and specific features of visual system fatigue formation were identified. Because of complete (in microscope operators) or partial (in subjects working with magnifying glasses and display users) "deprivation" of accommodation, these subjects develop early presbyopia (at the age of 30-35 years). In microscope operators long strain of accommodation system leads to professional myopia, while display users develop pseudomyopia. The highest overstrain is observed after 4 years of work in microscope operators, after 5 years in magnifying glass users, and after 6 years in computer users.

Adolescent↗
PubMedDate not supplied

Objective and subjective assessment of a new diffractive trifocal contact lens.

The purpose of this study was to test the objective and subjective performance of the Holo-Or Rigid Gas Permeable (RGP) Multifocal Contact Lens (MFCL), a new trifocal diffractive contact lens. Eleven experienced and two nonexperienced rigid gas permeable contact lens wearers participated in the study. Eleven patients were presbyopic (age 40-57) and two were aphakic (age 12 and 14). All patients were tested both with their best correction for distance and near and trifocal diffractive contact lenses. The follow-up period was 3-8 months. Subjective opinion was also assessed. Statistical analysis was performed using Student's t-test. We did not find any significant difference in visual acuity, measured at 6 m, 80 cm, and 40 cm, between best correction and Holo-Or diffractive contact lenses. Depth of focus improved to a statistically significant extent when using trifocal contact lenses. A small reduction in contrast sensitivity was observed when the patients used multifocal contact lenses. Overall satisfaction and comfort was good to excellent in 10 out of 13 patients. Two additional patients who used a bifocal model of the same contact lens design showed similar results. Holo-Or Trifocal Diffractive Contact Lenses are a satisfactory means of optical correction for patients with presbyopia or accommodative problems.

Adult↗
PubMed2002

The efficacy of computer glasses in reduction of computer worker symptoms.

BACKGROUND: Computer workers with presbyopia are at greater risk for the development of symptoms with a conventional prescription vs. a computer prescription because general-wear multi-focal corrections often do not provide adequate correction for the viewing distances and angles needed at the computer workstation. "Computer glasses," as defined by the American Optometric Association, are specifically designed for the computer workplace and have a different lens design or prescription than general-wear glasses. The purpose of this study is to evaluate the effectiveness of computer glasses in reduction of symptoms of presbyopic computer users. METHODS: Subjects were 26 symptomatic presbyopic computer users who had had an eye examination within the past year and had 20/20 vision at distance and near with habitual glasses. Two interventions in planned alternating order were tested for 3 weeks each on all subjects. One intervention was computer glasses. The comparison intervention was an ergonomic self-assessment tool (ESAT) with their habitual Rx. Symptoms were assessed before and after each intervention. A post-comparative questionnaire asked subjects to reflect on the relative efficacy and ease of use of the two interventions. RESULTS: The computer glasses were significantly more effective at reducing the frequency and severity (p < 0.008) of the symptoms than the ESAT, and 24 of 26 subjects judged the computer glasses to bemore effective. Subjects attributed 80.7% of symptom reduction to the computer glasses and 19.3% to the ESAT. Although the ESAT was judged effective, it was not as effective as the computer glasses. CONCLUSION: Computer glasses have been shown to be effective in reduction of vision-related symptoms of computer users.

Computers↗
PubMed2004

[Geriatric eye diseases].

Ageing of the eye affects all ocular structures. Presbyopia is an early manifestation of physiological ageing resulting in the impossibility to read without additional spectacle correction. Some systemic disorders may interfere with the physiological ageing of the eye and cause blindness. In the western countries blindness is caused by age-related macular degeneration (26%), glaucoma (20.5%), cataract (11.2%), diabetic retinopathy (8.9%) and ischemic optic neuropathy (4 %).

Aged↗
PubMed2004

Age related visual impairment in the elderly.

Visual impairment among the elderly is a major health problem. With advancing age, the normal function of eye tissues decreases and there is an increased incidence of ocular pathology. Demographic studies have shown that age is the best predictor of blindness and visual impairment. The most common causes of age related visual impairment in the elderly are presbyopia, cataracts, age related macular degeneration, primary open angle glaucoma and diabetic retinopathy. Untreated visual impairment leads to physical handicap, increased incidence of fall, depression, social isolation and dependency. Active screening for visual loss in the elderly should be part of the health examination. The elderly should be encouraged to come for formal 1-2 yearly eye assessment for early detection of visual impairment and to treat all associated problems in order to prevent permanent visual loss.

Aged↗
PubMed1991

Eyeglasses to maintain flexibility of vision for the older dentist: the Otago dental lookover.

Presbyopia is inability of the eye to accommodate and provide clear images of near objects. It affects all dentists in middle age, when "near point," the nearest point at which the eye can focus accurately, exceeds ideal working distance. Dentistry has unique visual demands and many older dentists have been shown to be working with less-than-optimal visual efficiency and comfort. This paper discusses methods for improving vision in the dental operatory and details a new design for eyeglasses suitable for the presbyopic dentist.

Aged↗
PubMed1991

Physiology of aging and its influence on the contact lens prescription.

The normal progressive physiological and visual effects of aging and its influence on the ability of contact lenses to provide ametropic correction is examined in this article. Of primary significance is the aging eye's perceptual ability especially in the mesopic range of vision. In addition, a recap of current available techniques is included for correction of presbyopia with contact lenses from the perspective of prescribing for an aging patient--not merely a patient who has lost only the ability to accommodate. One of the hallmarks of the profession of optometry has been its traditional support of the premise that patients should be provided with the best possible optical correction. While there are presbyopic patients who can achieve satisfactory vision via the contact lens modalities now in use, the physiological influences discussed here have been generally ignored by the profession. A redefinition of the criteria indicating patient "success" has evolved from achieving satisfaction through excellent vision derived from the optimum optical correction, to satisfaction obtained through patient selection and indoctrination to wear an optically inferior device. Unless the physiological, visual, and psychological effects of aging are adequately compensated by future contact lens designs, most elderly patients will remain likely to return to spectacles as the deficiencies of contact lens correction become progressively more apparent to them.

Accommodation, Ocular↗
PubMed1991

The effect of monovision lenses on the near-point range of single binocular vision.

Monovision (MV) contact lenses are commonly used to provide optical correction for presbyopia. Based on their review of the literature on fusional mechanisms, Erickson and Schor predicted that monocular blur associated with MV should not be sufficient to disrupt binocular fusion. We found that fusional vergence ranges in presbyopes corrected with MV were not substantially different from those measured under full binocular nearpoint correction. There were small but statistically significant tendencies for the phoria and base-in vergences to be less exo under MV conditions. Comparisons of findings between a group of successfully adapted MV patients and a group of patients who were unsuccessful with MV indicated no significant differences, suggesting that there is no adaptation effect for these performance variables and that these tests are not effective predictors of MV success.

Adaptation, Ocular↗
PubMed1991

A clinical study of patient acceptance and satisfaction of Varilux Plus and Varilux Infinity lenses.

An independent study was conducted at the UAB School of Optometry to determine the clinical success with Varilux Plus (Varilux 2) and Varilux Infinity progressive addition lenses (PAL). Two hundred eighty patients (280) were fit between June 1988 and May 1989. The acceptance rate of 97.5 percent was based on the number of lenses ordered versus the number of lenses returned. Patients were contacted by telephone and asked to rate their level of satisfaction with their PALs. A chi-square (non-parametric) test revealed no statistically significant differences in levels of satisfaction with respect to gender, PAL type, or degree of presbyopia. Also, neither refractive error nor previous lens history had a measurable impact on patient satisfaction.

Eyeglasses↗
PubMed1991

A comparative evaluation of Readables to single vision lenses.

Emmetropic presbyopes are often prescribed single vision lenses for near or intermediate work. These lenses limit the usable range of clear vision especially in advanced presbyopia. Readables, a special purpose PAL that emphasizes intermediate and near vision extends the usable range by providing appropriately changing power over the middle 28 millimeters of the lens. A crossover design, randomized controlled clinical trial was undertaken to determine if Readables were perceived to provide better function than the single vision reading lens. Readables were preferred by a ratio of 25:2 and scored significantly better in lens performance measures. The design benefits of Readables are appreciated by the presbyopic patient.

Adult↗
PubMed1991

Posterior attachment of ciliary muscle in young, accommodating old, presbyopic monkeys.

The authors studied the posterior attachment of the ciliary muscle in seven young (3-10 yr) and five old (26-34 yr) rhesus monkeys by light microscopy and electron microscopy. Posterior attachment of the muscle bundles consisted of elastic tendons, exclusively. The elastic tendons were continuous with the elastic lamina of Bruch's membrane and were also connected by smaller elastic fibers to an elastic meshwork that surrounds the pars plana vessels. In some areas, the tendons formed focal contacts with the endothelial cells. The authors found that in old eyes, the tendons and the elastic fibers of the posterior ciliary body showed pronounced structural changes. The tendons appeared thickened, showed increased amounts of associated microfibrils, and were surrounded by dense layers of thick collagen fibrils. An increased amount of collagen fibrils was also seen between the elastic layer of Bruch's membrane and the pigmented epithelium. A mechanical link between those collagen fibrils and the elastic fibers is suggested by the presence of osmiophilic points of contact. The age-related increase in elastic fibrillar material could cause decreased compliance of the posterior insertion of ciliary muscle and could be an essential factor for presbyopia in rhesus monkeys.

Accommodation, Ocular↗
PubMedDate not supplied

Clinical evaluation of three bifocal contact lenses.

The ACC, Alges, and Tangent Streak bifocal contact lenses were fit in separate populations of presbyopic patients, some of whom had not previously worn contact lenses. Complete eye examinations were performed on fitting and at 6 and 12 months after fitting to determine how effectively the lenses corrected presbyopic symptoms. Patients were examined for subjective comfort, visual acuity, contrast sensitivity, and by slit lamp. Sixteen of the 24 ACC lens wearers (67%), 23 of 31 Alges lens wearers (74%), and 25 of 27 Tangent Streak lens wearers (93%) wore their lenses comfortably after 12 months. Nine of 18 failures (50%) were successfully refit in one of the other bifocal lenses. Most patients read 20/25 and J1 with contrast sensitivity in the normal range at distance and near. Twelve of 16 patients (75%) with no prior contact lens experience continued to wear the lenses at 12 months. We believe that bifocal contact lenses provide an acceptable alternative for the correction of presbyopia. Lens fitting requirements and patient selection are discussed.

Adult↗
PubMed1988

Hexagonal keratotomy for corneal steepening.

Hexagonal keratotomy is evaluated for treatment of hyperopia, presbyopia, and radial keratotomy over-response. Initial indications are that this modality appears promising. Sixteen patients were evaluated and one complication is discussed.

Cornea↗
PubMed1988

Potential range of clear vision in monovision.

A possible limitation for monovision contact lens treatment of presbyopia is that an intermediate correction cannot be incorporated into the prescription without compromising distance or near vision. A simple model using a standard prescription strategy for the add and a conservative estimate for the static depth of focus of the eye was used to predict the range of clear vision with monovision lenses. For adds up to 2D, little compromise in visual acuity was predicted for any gaze position.

Accommodation, Ocular↗
PubMed1987

Effect of defocus on visual field measurement.

Defocus increased visual field contrast thresholds for stimuli equal to or smaller than Goldmann perimeter target III (26 min arc diameter). Beyond 30 degrees-40 degrees from the centre of the visual field, defocus had little effect on contrast thresholds. For accurate clinical perimetry, ametropia and presbyopia should be corrected for small targets (less than or equal to target III) within 30 degrees-40 degrees of fixation with either a spectacle lens (if required power less than +/- 10 D) or a contact lens. Larger stimuli are little affected by defocus. Outside this central 30 degrees-40 degrees field, correction with contact lenses should be provided if fixation is poor due to ametropia. Scotomata for which no cause is evident should be further investigated to find whether they have a refractive basis.

Contact Lenses↗
PubMed1986

Visual characteristics of rural Central and South Americans.

Rural inhabitants of Venezuela, Ecuador and Honduras were examined by volunteer optometry student interns. The resulting data indicate significantly lower best-corrected distance visual acuities, a greater prevalence of many ocular pathologies, less frequent occurrence of myopia, and an earlier onset of presbyopia than is found in the general United States population.

Adult↗
PubMed1985

[Meridian photopic and mesopic color perimetry in normal, young and presbyopic subjects].

The authors report their results of static color perimetry performed with the Harms perimeter. Photopic testing was performed among 10 young normal subjects and then with 10 presbyopes with otherwise unremarkable ocular examinations. Mesopic testing was done with 9 young subjects. Three thresholds of perception were stated: achromatic, minimally colored, and chromatic. Using photopic testing, red perception was far more sensitive in central vision, and the inverse was found in peripheral vision. Tritanomaly exists in the fovea, and at 15 degrees nasal to the fovea, the 3 color curves cross. In presbyopia, age is responsible for decreased sensation of red and green compared to white, and, all color perception disappears beyond the blind spot. The decrease in sensitivity for blue is even more significant realising a foveal tritanopia. At a lower luminance level, mesopic testing revealed an achromatic threshold for green and blue with central lowering of sensitivity. Deductions are made concerning the anatomo-physiologic mechanisms involved.

Adaptation, Ocular↗