Fig. 7. Age-related changes in human vitreous collagen. Collagen content (right ordinate) is indicated by solid dots (means) and darkly hatched boxes (height = standard error). Collagen concentration (left ordinate) is indicated by asterisks (means) and lightly hatched boxes (height = standard error). There are no significant changes in vitreous collagen content after the age of 20 years, consistent with the long half-life of this molecule. Vitreous collagen concentration decreases during the first decade of life because there is no synthesis of new collagen during this period of eye growth and increasing vitreous volume. Collagen concentration in the gel vitreous increases after the age of 40 to 50 years, however. This is due to the decrease in gel vitreous volume that occurs during this time, concentrating the remaining collagen in an ever-decreasing volume of gel vitreous. The increase in gel vitreous collagen concentration between the ages of 50 to 60 and 80 to 90 is statistically significant (p < 0.05). (From Balazs EA, Denlinger JL. Aging changes in the vitreous. In Sekular R, Kline D, Dismukes N, eds. Aging and Human Visual Function. New York: Alan R. Liss, 1982:45, with permission)