Biomaterial Database

Presbyopia and the changes with age in the human crystalline lens. 1973

R F Fisher

1. A method of determining the distribution of capsular moulding pressure is described. This includes:(a) measuring the decrease in polar depth of the lens from photographed lens profiles before and after the capsule has been cut around the entire equator of the lens,(b) measuring the elastic properties of the lens substance by subjecting the lens to known centrifugal forces and photographing the polar strain so produced.2. A method of determining the relationship between capsular and lenticular strain is described. This includes (a) measuring the elastic properties of the capsule (b) measuring the elastic properties of the lens substance and (c) measuring the profiles of the photographed lens. The ratio of the strain of lens substance to capsule is expressed as a dimensionless parameter, the lens number.3. The decrease in the amplitude of accommodation with increasing age is proportional to the lens number divided by the square of the radius of the accommodated lens, assuming that the movement of the capsulozonular attachments of the lens remains unimpaired in the ageing eye.4. Ageing changes in the human crystalline lens are sufficient to account for a total loss of accommodation by the age of 61 years.

UI	MeSH Term	Description	Entries
D007231	Infant, Newborn	An infant during the first 28 days after birth.	Neonate,Newborns,Infants, Newborn,Neonates,Newborn,Newborn Infant,Newborn Infants
D007908	Lens, Crystalline	A transparent, biconvex structure of the EYE, enclosed in a capsule and situated behind the IRIS and in front of the vitreous humor (VITREOUS BODY). It is slightly overlapped at its margin by the ciliary processes. Adaptation by the CILIARY BODY is crucial for OCULAR ACCOMMODATION.	Eye Lens,Lens, Eye,Crystalline Lens
D008722	Methods	A series of steps taken in order to conduct research.	Techniques,Methodological Studies,Methodological Study,Procedures,Studies, Methodological,Study, Methodological,Method,Procedure,Technique
D008875	Middle Aged	An adult aged 45 - 64 years.	Middle Age
D010781	Photography	Method of making images on a sensitized surface by exposure to light or other radiant energy.	Photographies
D011305	Presbyopia	The normal decreasing elasticity of the crystalline lens that leads to loss of accommodation.	Presbyopias
D011312	Pressure	A type of stress exerted uniformly in all directions. Its measure is the force exerted per unit area. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Pressures
D002498	Centrifugation	Process of using a rotating machine to generate centrifugal force to separate substances of different densities, remove moisture, or simulate gravitational effects. It employs a large motor-driven apparatus with a long arm, at the end of which human and animal subjects, biological specimens, or equipment can be revolved and rotated at various speeds to study gravitational effects. (From Websters, 10th ed; McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
D002648	Child	A person 6 to 12 years of age. An individual 2 to 5 years old is CHILD, PRESCHOOL.	Children
D004548	Elasticity	Resistance and recovery from distortion of shape.