Refractive power in the eye is contributed primarily by two visual components - the cornea, which provides a large fixed refractive contribution, and the crystalline lens, which provides a smaller variable contribution that allows focus from infinity to near points. This process - accommodation - results from a carefully controlled change in crystalline lens thickness, sharpness of anterior and posterior curvatures, and distance between the cornea and anterior lens surface. With increasing age, the amplitude of the accommodative response gradually decreases, resulting in the need for optical prostheses for near vision. The long-range goal of this work is to characterize fully the human accommodative mechanism and the factor(s) leading to age-dependent accommodative loss, using data obtained non-invasively from human subjects. Previous non-invasive studies of accommodation and accommodative loss in humans have led to the characterization of this process as functions of age and accommodative state, and the development of a mathematical model that both describes the process and makes predictions that can be tested experimentally. This model will be used in the next funding period to characterize fully both accommodation and the factors leading to accommodative loss, utilizing lens shape information from Scheimpflug slit-lamp photography, anterior segment and globe parameters from standard ophthalmological techniques such as pachymetry and A-scan ultrasonography, and viscoelastic data obtained from studies of post-mortem human lenses. This work will be extended by the initiation of new studies on the dynamics of accommodation in youthful and adult eyes, using a newly developed video-Scheimpflug technique; the rate of accommodation and disaccommodation will be characterized as a function of accommodative task and subject age, and correlated both with static (equilibrium) accommodation processes and with the viscoelastic properties of the lens itself. Finally, the recent characterization of human lens development in youthful eyes indicates that the accommodation mechanism may differ significantly at ages less than 18 yr; static and dynamic comparisons between data obtained from youths and adults will allow the full characterization of accommodation and the development of presbyopia in the human eye.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY002195-17
Application #
2158378
Study Section
Special Emphasis Panel (ZRG1-VISB (02))
Project Start
1978-02-01
Project End
2000-06-30
Budget Start
1996-07-01
Budget End
2000-06-30
Support Year
17
Fiscal Year
1996
Total Cost
Indirect Cost
Name
Rensselaer Polytechnic Institute
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
002430742
City
Troy
State
NY
Country
United States
Zip Code
12180
Koretz, Jane F; Cook, Christopher A; Kaufman, Paul L (2002) Aging of the human lens: changes in lens shape upon accommodation and with accommodative loss. J Opt Soc Am A Opt Image Sci Vis 19:144-51
Koretz, J F; Cook, C A; Kaufman, P L (2001) Aging of the human lens: changes in lens shape at zero-diopter accommodation. J Opt Soc Am A Opt Image Sci Vis 18:265-72
Koretz, J F; Cook, C A (2001) Aging of the optics of the human eye: lens refraction models and principal plane locations. Optom Vis Sci 78:396-404
Cook, C A; Koretz, J F (1998) Methods to obtain quantitative parametric descriptions of the optical surfaces of the human crystalline lens from Scheimpflug slit-lamp images. I. Image processing methods. J Opt Soc Am A Opt Image Sci Vis 15:1473-85
Koretz, J F; Cook, C A; Kaufman, P L (1997) Accommodation and presbyopia in the human eye. Changes in the anterior segment and crystalline lens with focus. Invest Ophthalmol Vis Sci 38:569-78
Koretz, J F; Rogot, A; Kaufman, P L (1995) Physiological strategies for emmetropia. Trans Am Ophthalmol Soc 93:105-18;discussion 118-22
Cook, C A; Koretz, J F; Pfahnl, A et al. (1994) Aging of the human crystalline lens and anterior segment. Vision Res 34:2945-54
Koretz, J F; Cook, C A; Kuszak, J R (1994) The zones of discontinuity in the human lens: development and distribution with age. Vision Res 34:2955-62
Russell, P; Koretz, J; Epstein, D L (1993) Is primary open angle glaucoma caused by small proteins? Med Hypotheses 41:455-8
Radlick, L W; Koretz, J F (1992) Biophysical characterization of alpha-crystallin aggregates: validation of the micelle hypothesis. Biochim Biophys Acta 1120:193-200

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