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Results for “PRESBYOPIA”

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At least 541 records · Page 30Linked to original sources
PubMed1976

Contraction of a perifoveal epiretinal membrane simulating a macular hole.

Four patients observed for a three- to four-year period had a hole in an epiretinal membrane overlying the macula that mimicked a macular hole. In two patients the clinical appearance remained essentially constant. In one, the epiretinal membrane contracted further, reducing the apparent macular hole to a slit and causing the typical appearance of a macular pucker. In the fourth patient, the epiretinal membrane peeled spontaneously causing the apparent hole to disappear. None of the patients had static perimetric findings that suggested a true macular hole. All of the patients had normal or nearly normal visual acuity when first seen. This was maintained except in the patient who suffered further membrane contraction. Fluorescein angiography demonstrated a slight fluorescence in the base of the hole in three of the four patients; however, it was not as pronounced as one sees in true macular holes. Lamellar macular holes characteristically show no fluorescence in the area of the hole.

Aged↗
PubMedDate not supplied

Clinical evaluation of 14 patients with the Charles Bonnet syndrome (isolated visual hallucinations).

A group of 14 patients with isolated visual hallucinations who met the criteria proposed by Gold and Rabins for Charles Bonnet syndrome (with the exception of the criterion "hallucinations are stereotyped") underwent psychiatric, neurologic, and ophthalmologic tests. Additional common characteristics of the hallucinations included the absence of personal meaning of the content of the hallucinations and the disappearance of the hallucinations when the patients closed their eyes. There was no evidence for a relationship of the syndrome to psychiatric disorders. In the majority of cases, ocular pathology and neurologic disturbances were diagnosed. There was also evidence that most patients were suffering from social isolation. From these data it is concluded that a combination of factors is probably responsible for the Charles Bonnet syndrome.

Aged↗
PubMed1986

Dynamics of accommodation: measurements for clinical application.

Accommodation dynamics have not been used in clinical diagnosis as have eye movement and pupillary dynamics; the difficulty of clinical observation is matched by limitations in measurement methods. An instrument suitable for clinical use is described that allows measurement of step response latencies and especially time constants. With computer analysis, phase plane trajectories, and noise spectra can be quickly obtained also. The utility of these dynamical parameters for clinical diagnosis is illustrated by a study of changes of time constants with age in prepresbyopia.

Accommodation, Ocular↗
PubMed1989

A comparison of self-assessed satisfaction among wearers of dentures, hearing aids, and eyeglasses.

Patient assessment of dental prostheses, hearing aids, and eyeglasses can provide valuable data regarding adaptability of geriatric patients. This article describes a cross-modality evaluation of patient satisfaction with dental, hearing, and vision prostheses. Three hundred ninety-one subjects with recently placed prostheses were evaluated for self-assessed satisfaction and other related information. Patient satisfaction was compared with, age, type of prosthesis, and level of impairment. No statistical evidence of an age-related dissatisfaction with prostheses was found. Significant differences in levels of satisfaction were noted between different types of prostheses. Irrespective of level of impairment, patients expressed greatest satisfaction with dental prostheses and least satisfaction with hearing aids.

Aged↗
PubMedDate not supplied

Ophthalmology in the United States at the time of the revolution.

At the time of the American Revolution, understanding of diseases of the eye was rudimentary, treatment of ocular problems was largely ineffective, and American physicians were highly dependent on their European colleagues for training and development. Knowledge of optics, light and color was somewhat more advanced. The author reviews the state of eye care during the Revolutionary period, historically and anecdotally, with references to the literature of that time.

Blindness↗
PubMedDate not supplied

Vertical prisms. How to avoid them.

Prescribing vertical prisms not infrequently leads to unsightly spectacles at best, and computing them may lead to errors at worst. Prismatic compensation for a particular reading point is of little value when the patient uses other eccentric portions of the lens, and it is not necessary if the patient learns to use (or continues to use) the optical centers. Clinical evaluation of eye-head posture and vertical phorias may reveal tell-tale clues in managing vertical imbalances in general and the anisometropic presbyope in particular.

Eyeglasses↗
PubMedDate not supplied

Refraction problems after refractive surgery.

While refractive surgery such as radial keratotomy, epikeratophakia, and corneal relaxing incisions offer many potential benefits to patients, they can also generate optical problems such as overcorrection or undercorrection of the prior refractive error and variable vision. The authors offer suggestions for avoiding problems through proper patient selection; candid preoperative communication with the patient about possible difficulties and limitations; understanding of the physiological changes that may occur; and optical techniques for alleviating postoperative vision problems.

Contact Lenses↗
PubMed1978

Chromoretinoscopy.

Explore the source record for details and available documents.

Accommodation, Ocular↗
PubMedDate not supplied

Application of a simple mechanical model of accommodation to the aging eye.

A simple model for the mechanics of accommodation in the human eye, previously proposed, is applied to the eye at different ages. Data from work by R. F. Fisher is used to derive values for the elasticity of lens-plus-zonules and data from work by G. W. H. M. van Alphen and W. Graebel is used to derive values for the elasticity of the choroid, each at a series of ages. The model is applied in two ways: (i) the elasticity of one component is allowed to change with age, while the other (and also ciliary muscle force) is held constant and the effect on accommodative amplitude is estimated; (ii) both elasticities are allowed to change with age, and muscle force is assumed to take on values producing a constant change in the radius of the "ciliary ring". It is shown that, in principle, age-related changes in choroid could account for a substantial component of the observed loss of accommodative amplitude, and it is suggested that this may be the case for monkeys, but not for humans. For the case of "all components changing", which is probably the case for humans, the ciliary muscle is likely to become stronger with age.

Accommodation, Ocular↗
PubMed1992

Age-related changes of the human ciliary muscle. A quantitative morphometric study.

The age-related changes of the ciliary muscle of human eyes (33-87 years) were studied on histological meridional sections. Eighty-five melanoma eyes and 10 eyes of normal donors were investigated. The total area and the length of the muscle, the area of the three main portions and the distance of the inner apex of the muscle to the scleral spur were determined and correlated with age. Total area and length of the muscle show a continuous and significant decrease with age. The area of the longitudinal and reticular portion continuously decreases, whereas the area of the circular portion significantly increases with age. The decrease in area is more pronounced in the longitudinal portion than in the reticular portion of the muscle, which shows an age-related increase in connective tissue. In addition, the distance of the inner apex of the muscle to the scleral spur shortens continuously. Thus, with increasing age the ciliary muscle adopts an anterior-inward position. A similar form is seen in young eyes after ciliary muscle contraction only. There might be a functional relationship between the observed age-changes in the ciliary muscle system and the phenomenon of the so-called 'lens paradox' (steepening of the anterior and posterior curvatures of the disaccommodated lens with age).

Adult↗
PubMed2006

Dynamic performance of accommodating intraocular lenses in a negative feedback control system: a simulation-based study.

A dynamic model of ocular accommodation is used to simulate the stability and dynamic performance of accommodating intraocular lenses (A-IOLs) that replace the hardened natural ocular lens that is unable to change focus. Accommodation simulations of an older eye with A-IOL materials having biomechanical properties of a younger eye illustrate overshoots and oscillations resulting from decreased visco-elasticity of the A-IOL. Stable dynamics of an A-IOL are restored by adaptation of phasic and tonic neural-control properties of accommodation. Simulations indicate that neural control must be recalibrated to avoid unstable dynamic accommodation with A-IOLs. An interactive web-model of A-IOL illustrating these properties is available at http://schorlab.berkeley.edu.

Accommodation, Ocular↗
PubMed2005

Comparison of pilocarpine-induced and stimulus-driven accommodation in phakic eyes.

With the recent introduction of potentially accommodative intraocular lenses (IOL), there is a need for methods to evaluate their accommodative potential. In most studies assessing IOL movement, pilocarpine is used to stimulate contraction of the ciliary muscle. The aim of this study is to determine if pilocarpine-induced ciliary muscle contraction is comparable to physiological stimulus-driven accommodation in young and presbyopic subjects. Ten emmetropic young subjects (23-25 years) and 11 emmetropic presbyopic subjects (51-62 years) were included in this study. Anterior chamber depth (ACD) and lens thickness (LT) were assessed with partial coherence interferometry (PCI). A moveable stimulus was coupled to the PCI equipment for measurement of biometric lens changes. ACD was measured with the stimulus at infinity and then at the subjects individual nearpoint, and after application of two drops of 2% pilocarpine. In young subjects, there was no significant difference in lens change between nearpoint and pilocarpine stimulation. Presbyopic subjects showed no relevant lens change when accommodating at the nearpoint, however, under pharmacologically induced ciliary muscle contraction with pilocarpine, there was a significant forward shift of the anterior and posterior lens pole, leading to a translational forward lens shift of about 150 microm. This study demonstrates that pilocarpine acts "physiologically" in young phakic subjects, but is a "superstimulus" in presbyopic phakic subjects. Therefore, IOL movement may be overestimated when using pilocarpine to stimulate accommodation.

Accommodation, Ocular↗
PubMed2003

Understanding the accommodating intraocular lens.

PURPOSE: To review current accommodating intraocular lens (IOL) designs and introduce a new design consisting of a plus lens and a minus lens. SETTING: Cornea Consultants of Boston, Boston, Massachusetts, USA. METHODS: Computer simulation studies of a model eye calculated the pseudoaccommodation range with different powers of 1 IOL or of 2 IOLs acting as a doublet. RESULTS: The doublet consisting of a convex (plus) lens and a concave (minus) lens gave a greater range of power change than a single convex lens or a doublet consisting of 2 convex lenses. The greater range of power results from the plus lens moving forward. CONCLUSION: The results show that an IOL design consisting of positive and negative lenses that move closer or farther from each other offers a greater range of pseudoaccommodation than other designs.

Accommodation, Ocular↗