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

Area of Science:

• Ophthalmology
• Human Anatomy
• Aging Research

Background:

• The aging human eye undergoes various structural and functional changes.
• Understanding age-related alterations in the ciliary muscle is crucial for ocular health.
• Previous studies have indicated changes in the aging lens, but ciliary muscle dynamics require further investigation.

Purpose of the Study:

• To investigate age-related histological changes in the human ciliary muscle.
• To correlate these changes with age across a wide adult age range.
• To explore potential functional implications of these age-related modifications.

Main Methods:

• Histological analysis of meridional sections from 85 melanoma and 10 normal human donor eyes (ages 33-87).
• Quantification of total muscle area, length, and the areas of its longitudinal, reticular, and circular portions.
• Measurement of the distance from the inner apex of the ciliary muscle to the scleral spur.

Main Results:

• Total ciliary muscle area and length significantly decrease with age.
• The longitudinal and reticular portions decrease in area, while the circular portion increases.
• The ciliary muscle shifts anteriorly and inward with age, similar to a contracted state.

Conclusions:

• The aging human ciliary muscle undergoes significant structural remodeling, characterized by decreased overall size and altered proportions.
• This age-related anterior-inward shift of the ciliary muscle may contribute to age-related changes in lens shape, such as the 'lens paradox'.