Bifocal Adds and Environmental Temperature

Kragha, I. K. O. K.; Hofstetter, Henry W.

doi:10.1097/00006324-198605000-00009

Cited by 12 publications

(12 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Increases in spectacle reading addition may still be beneficial beyond this age, since the effective magnification provided by shorter reading distances compensates for the loss of visual acuity in the older eye . Pointer has recently reviewed clinical aspects of the measurement of accommodation and the estimation of near additions: his summary plot of mean near addition as a function of age in the United Kingdom is shown in Figure , together with some similar data from the Americas . Clearly various additional factors, such as physical stature, the nature of their visual tasks and working distances, will affect the additions given to individual patients.…”

Section: Changes With Age In Accommodation and Refractionmentioning

confidence: 99%

“…At present there appear to have been no successful demonstrations of strategies, such as diet, which might accomplish this retardation of the loss of accommodation, although nutrient intake is, for example, known to affect the development of early age‐related lens opacities . There is some weak evidence that environmental factors, such as high temperatures or, perhaps, excessive sunlight might modestly accelerate the onset of presbyopia, so that protective measures might perhaps have some benefit, although this remains unproven and the reality of any effect has been challenged by some authors . In any case, it should be remembered that individuals who have just become presbyopic may have many years of life before them, so that the onset of presbyopia needs to be delayed by several years to have a worthwhile impact.…”

Section: General Approaches To Correctionmentioning

confidence: 99%

See 1 more Smart Citation

Developments in the correction of presbyopia I: spectacle and contact lenses

Charman

2013

Ophthalmic Physiologic Optic

147

136

View full text Add to dashboard Cite

Purpose: To outline the refractive problems associated with presbyopia and to review the basis and relative merits of currently-available methods for their correction, with detailed consideration of spectacle and contact lens approaches. Contents: In the developed world, most of the present population will spend roughly half their lives as presbyopes. The well-known presbyopic changes with age in amplitude of accommodation and required near addition are briefly reviewed, together with the less widely acknowledged slow drifts that occur in distance refraction. The desirability of restoring to presbyopes clear vision for objects at any distance, ideally corresponding to vergences within the range of at least 0 to À5 D, in any viewing direction, is stressed. A general outline is given of possible corrective methods. Methods which satisfy the needs of a 50 year-old may not be suitable for the 80 year-old. Corrections may involve both fixed-and variablefocus lens systems, and surgical methods which modify the optics of the cornea, replace the crystalline lens with different fixed optics, or attempt to at least partially restore active accommodation. Some more recent methods of spectacle and contact lens correction are described in more detail. Particular attention is given to recent commercially-developed spectacles in which the corrective power can be varied actively by either mechanical (liquid-filled deformable lenses or Alvarez lenses) or electrical (liquid crystal lenses) means to allow objects at different distances to be seen clearly. Contact lens corrections show less progress and are still preferred only by a minority of older patients, most of whom are early presbyopes. Summary: The rising proportion of presbyopes in the population, covering an age span of around 40 years, represents both a problem for those concerned with giving their patients the best vision possible at both far and near viewing distances and a commercial opportunity. Traditional single-vision distance and near, bifocal, and progressive spectacle lens solutions, together with contact lens modalities for presbyopic correction, are being challenged by a variety of new approaches. It remains to be seen whether the latter will receive wide acceptance in practice.

show abstract

Section: Changes With Age In Accommodation and Refractionmentioning

confidence: 99%

Section: General Approaches To Correctionmentioning

confidence: 99%

Developments in the correction of presbyopia I: spectacle and contact lenses

Charman

2013

Ophthalmic Physiologic Optic

147

136

View full text Add to dashboard Cite

show abstract

“…[173][174][175] Longitudinal studies suggest that individual objective amplitudes fall almost linearly with age to reach zero at about the age of 50, 174,175 although averaged data may show a reduced rate of decline as presbyopia is approached due to the averaging of individual linear declines with different intercepts. 176 There is some suggestion that the intercept may vary with latitude or temperature at the individual's place of residence [177][178][179] but, in general, the striking feature is that the changes with age vary very little between individuals and, unlike many aspects of human physiology, do not appear to have been affected by the changes in nutrition and lifestyle of the modern age. Current amplitude measure-ments are very similar to those recorded by Donders in the 19th Century 171 (although it must be remembered that Donder's results were obtained with maximal convergence and were referred to the nodal point of the eye, seven millimetres behind the cornea, rather than the spectacle plane 180 ).…”

Section: Models Of the Accommodative Mechanismmentioning

confidence: 99%

The eye in focus: accommodation and presbyopia

Charman

2008

Clinical and Experimental Optometry

206

136

View full text Add to dashboard Cite

Current understanding of the anatomy, function and performance of the accommodative system of the young, adult human eye is outlined. Most major current models of the accommodative mechanism are based on Helmholtz's original ideas but, despite of a growing volume of related research, uncertainty continues over the relative contributions made to the overall mechanism by different ocular structures. The changes with age are then discussed. Although the amplitude of accommodation decreases steadily from later childhood, the speed and accuracy of the system within the available amplitude are little impaired until the age of about 40, when the amplitude falls below that needed for normal near work. A review of the available evidence on age-related change in the lens, capsule, ciliary body and other relevant ocular structures confirms that geometric and viscoelastic lenticular changes play major roles in the progressive loss of accommodation. Other factors may also contribute in an, as yet, unquantified way and a full understanding of the origins of presbyopic change remains elusive.

show abstract

“…Although some studies indicated that nearly all individuals aged above 50 are presbyopic, 10 studies in Tanzania 8 and Brazil 7 showed that 31.3% and 13.7% of their 50–64‐year‐old individuals were not presbyopic. Moreover, factors other than age have been proposed by some researches, and it is believed that early presbyopia could be associated with the female gender, hyperopia, an imbalanced nutrition and higher environmental temperatures 7,10–13 . Because little data are available regarding the age of developing presbyopia, its contributing factors and its prevalence in different parts of the world, conducting epidemiological studies can provide us with valuable information in this regard.…”

Section: Introductionmentioning

confidence: 99%