Central surface curvatures of postmortem- extracted intact human crystalline lenses: implications for understanding the mechanism of accommodation.
OBJECTIVE
To measure the radii of curvature of postmortem, whole, encapsulated human crystalline lenses, free of all zonular attachments, and to calculate their corresponding optical powers.


METHODS
Experimental study.


METHODS
Thirty human crystalline lenses from donors with a mean age of 33.6+/-14.4 years.


METHODS
Intact clear human crystalline lenses were obtained within an average of 21 hours of death. The lenses were removed from the eye by the contributing eye bank and shipped in Optisol-GS, a physiologic preservative storage medium. These lenses, with intact capsules, were freed of all zonular attachments. The lenses were stored at 7 degrees C and were maintained in the same storage medium during the period that they were held for evaluation. Using a portable Keratron Scout corneal topographer (Eyequip, Ponte Vedra Beach, FL) fixed to an optical bench, the radii of curvatures of the anterior and posterior surfaces of the crystalline lens were measured daily for 10 days after receipt of the tissue. The capsules of the crystalline lenses remained intact, and the lenses were clear throughout the study. Measurements were made at room temperature after removing the lens from storage. Eight repetitions of the topography were made from each surface on each day to determine the accuracy and stability of the measurement. Profile photographs were taken daily to establish the central crystalline lens thickness. The corresponding optical power of each physiologically maintained crystalline lens was calculated.


METHODS
The main outcome measures were the central anterior radius of curvature, the central posterior radius of curvature, the central thickness of each crystalline lens, and the amount of change in these parameters over 10 days.


RESULTS
The means +/- standard deviations of the central anterior and posterior radii of curvatures of the 30 adult lenses were 10.5+/-0.6 mm and 7.1+/-1.0 mm, respectively. The mean +/- standard deviation of the central thickness, as measured from profile photographs, was 3.9+/-0.5 mm. These mean measurements remained stable for up to 5 days after receipt of the tissue. The mean and standard deviation of the calculated optical power of these postmortem, physiologically maintained, intact human crystalline lenses from donors with a mean age of 33.6 years was 19.8+/-1.7 diopters.


CONCLUSIONS
Lenses free of zonular tension are at an optical power that would be associated with optimal distance acuity.
Schachar
Ronald A
RA
University of Texas at Arlington, Arlington, Texas, USA. ron@2ras.com
D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000867:Anterior Chamber / Q000502:physiology; D000886:Anthropometry; D006801:Humans; D007908:Lens, Crystalline / Q000033:anatomy & histology*; D008022:Ligaments / Q000502:physiology*; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology*; D013314:Stress, Mechanical