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PubMed1982

Age-dependent loss of accommodative amplitude in rhesus monkeys: an animal model for presbyopia.

The refractive power and axial dimensions of the eye were measured under resting and fully accommodated conditions in 123 caged rhesus monkeys ranging in age from 0.5 to greater than 30 years. The mean resting refraction measured under ketamine anesthesia was -5 diopters. Accommodative amplitude, calculated as the difference between resting refraction and the most negative refraction measured 0.5 to 1 hr after topical application of a maximally effective dose of a cholinomimetic, showed an age-dependent decline. The mean accommodative amplitude of 1- to 5-year-old rhesus monkeys was a remarkable 34 D, while animals over 25 years of age averaged 5 D of accommodation. Some greater than 25-year-old animals showed no measurable change in refraction regardless of the dose or the type of cholinomimetic (carbachol, pilocarpine, or echothiophate) used. The resting axial thickness of the lens was found to increase with age throughout adulthood, well past the end of the growth period. A strong correlation was found between pharmacologically induced change in the refractive power of the eye and change in lenticular thickness. These similarities to the human condition suggest that the rhesus monkey represents a highly suitable animal model for the study of accommodation and presbyopia.

Accommodation, Ocular↗

PubMed1981

[Compensating presbyopia: a new physiological progressive lens (author's transl)].

After discussing the functional disadvantages arising after correction of presbyopia with uni--or multifocal lenses, the authors describe the optical and physiological advantages of a lens with progressively increasing power. The principal qualities of these physiologically progressive lenses are studies, and the results of a preliminary survey concerning their use are analysed. The indications for, and adaptation and tolerance of these lenses are outlined.

Aged↗

PubMed1995

Broken down by age and sex. The optical correction of presbyopia revisited.

New transverse clinical data are presented which describe the time course of presbyopia, as indicated by the temporal change in magnitude of the binocular spectacle add, in normally sighted male and female Caucasian subjects. An initial steep increase in add requirement beginning in the early forties becomes relatively slower but still of significance beyond the mid-fifties. This observation is correlated with the age-related progressive decline in the amplitude of accommodation, itself a consequence of physiological changes in the crystalline lens and capsule. The continuing need for an increase, albeit at a reduced rate, in the positive near supplement beyond the mid-to-late fifties (by which time little or no useful accommodation is available), is now attributed to the visually disruptive effects within the high spatial frequency domain of progressive age-related lenticular changes. The magnification afforded by the positive add increases spatial grain and thereby enhances visibility of detail in an ageing visual system free of any gross senile pathology. A small but consistent gender difference (congruent to 0.1 D) is revealed in presbyopic corrections: physiological and (more probable) physical bases are suggested for the observation that females require an add of greater magnitude than their age-matched male counterparts.

Accommodation, Ocular↗

PubMed1996

Presbyopia.

The need for bifocals causes more angst, fear, depression, denial, searching for alternatives, and needless self-pity than any other benign intervention in all of medicine. To many, this is the first sign they are on the other side of the hill of life. I will try to explain, with a minimum of numbers and equations, what presbyopia is and how it is managed (and perhaps even cured in the near future) in an understandable way. I will also present a few clinical situations which the primary care physician often meets. I suspect many of you are already wearing bifocals or are delaying the acquisition of them.

Accommodation, Ocular↗

PubMed1997

The AC/A ratio, age and presbyopia.

Previous reports concerning the effect of age on the AC/A ratio have been equivocal. Therefore, the present study investigated both the stimulus (AC/As) and response (AC/Ar) ratios using a subjective haploscope-optometer in a relatively large sample of subjects (n = 42) over a wide range of ages (22-65 years). The AC/As showed a small but significant decrease with age (approximately 0.04 delta/D/year). When the older subjects (> 45 years of age) were excluded, however, there was no systematic age effect. The AC/Ar exhibited a small but significant increase with age (approximately 0.08 delta/D/year) for subjects under 45 years of age. However, when the older pre-presbyopes and younger presbyopes (35-44 years of age) were excluded, there was no systematic age effect. In subjects 45 years of age and older, the AC/Ar could not be reliably assessed. This was attributed to physiological and instrumentation noise as a result of the minimal change in accommodative response. In the mid-aged subjects (35-44 years of age), the apparent increase in AC/Ar with age was speculated to be due to neural adaptation of the crosslink gain from the accommodative to the vergence system and/or slight intrusion into the upper non-linear response region of accommodation with the measurements. The finding of AC/Ar constancy with age when mid-aged pre-presbyopes and early presbyopes were excluded supports the non-linearity hypothesis, and thus there appears to be no real change in AC/Ar with increased age. The results support the Hess-Gullstrand theory of presbyopia.

Accommodation, Ocular↗

PubMed1997

[How to correct presbyopia].

The appropriate addition correcting a patient's presbyopia can be determined by many ways. It depends on the amplitude of accommodation and convergence, ametropia and age of the patient but also on the kind of work and on the subjectively comfortable distance at which it is performed.

Accommodation, Ocular↗

PubMed1976

[Convergent strabismus in the age of presbyopia (author's transl)].

Based on 15 case reports it can be shown, that the onset of a convergent squint is even possible in the age of presbyopia, independent of the patient's refraction. The clinical picture resembles that of a divergence paralysis or the convergent strabismus of the Bielschowsky type. In 13 cases the decompensation of a previous esophoria may have caused this distance-esodeviation; a divergence paralysis is not probable. In two cases change of orthophoria to esotropia could be observed. Therefore we share the opinion of v. Graefe, that an increased tonicity of the internal recti induced for compensation of weak convergence in aged individuals may cause esotropia. Treatment with prisms for distant vision is easy and effective. No case required surgery.

Aged↗

PubMed1962