The interrelationship of lens anatomy and optical quality. I. Non-primate lenses.

We have quantified the influence of 'Y' sutures on lens optical quality (spherical aberration, i.e. focal length variability) as a function of age. Young (n = 6) and old (group 1, n = 5; and group 2, n = 4) bovine lenses were initially scanned by a low-power (2 mW) helium-neon laser beam passed either through or at a series of acute angles to suture branches. In all lenses, focal length variability was least when the beam was passed through areas of the lens devoid of sutures and greatest when passed through sutures. In older lenses, variability was also significantly increased in all locations though to a greater degree at sutures. Correlative morphological analysis by scanning electron microscopic (SEM) and three dimensional (3-D) computer-assisted drawings (CADs) revealed the following: (1) young lenses had uniformly hexagonal fibers arranged in parallel radial cell columns (RCCs), while old lenses had nonuniformly hexagonal fibers arranged in variably parallel RCCs; (2) the irregularly-sized and -shaped ends of young fibers overlapped within growth shells to form complementary anterior and posterior symmetrical 'Y' suture patterns, while larger and more irregularly-shaped ends of older lenses overlapped to form asymmetrical 'Y' patterns; and (3) the identical suture patterns in successive shells of young lenses resulted in inverted triangular suture planes extending from the embryonic nucleus to the lens periphery, while the progressively wider and more serpentine suture branches of old lenses resulted in inverted pyramidal suture planes with narrow apices oriented towards the embryonic nucleus and broad irregular bases oriented toward the lens periphery. Thus, there is a significant interrelationship between lens optical quality and structure that varies as a function of age. These results extend and confirm the results of our earlier studies on lenses with simpler 'line' sutures and preface our studies of primate lenses with more complex 'star' sutures. All of these studies show that lens sutural anatomy should be considered when evaluating the optical quality of normal and pathological lenses.