Abstract
Abstract: :
Purpose: To develop a metric technique assessing the morphology of the zonular apparatus, measure size, distribution and anchorage location of individual zonules with respect to the lens equator, in function of age, sex, and species. Methods: 10 human (55–82 y/o, 3–5 days PMT) and 7 cynomolgus (4–7 y/o, 1 to 3.5hrs PMT) postmortem eyes were used. After 24hrs formalin fixation, an aluminum ring machined to conform the globe was bonded with cyanoacrylate to the scleral wall at the level of the crystalline lens, and using an operation microscope, the posterior pole and corneoscleral rim were sectioned and vitreous and iris removed. The metal mounted tissue section was post fixed for >24hrs in 2.5% glutaraldehyde, post–fixed in osmium, transferred in 5 different grades of alcohol, washed in PBS twice for 5 min and underwent stepped critical point–drying. To assess the posterior face of the zonular apparatus, the hyaloid membrane was peeled after completion of the fixation process using #5 jeweler forceps under the operation microscope at 20x. The ring–tissue assembly was gold coated. Results: The technique was successful in 14 of 17 eyes showing the zonular apparatus under normal physiological tension. Even though degassing was done in a gradual manner, splits occurred in lenses with high PMT but not in fresh ones. Measured at the middle–point between capsule anchorage and ciliary body processes, zonule bundle diameter varied from 6 to 35 µm in human and 3.5 to 50µm in cynos. At the lens capsule anchorage zone, they split in finer strands varying from <1 to 7 µm in human and <0.5 to 15µm in cynos. The anterior zonules were larger than the posterior zonules in human than in cynos. The density of zonules was approximately 10 % higher in cynos than in human. The technique will also be used on paired eyes to study the effect of ex–vivo lens stretching (Denham et al, ARVO’02) and lens refilling (Parel et al, ARVO’03). Conclusions:This new technique is reproducible and allows clear morphological assessment of the zonular apparatus. CR: None Support: NIH EY14225; Vision CRC Sydney, Australia; Florida Lions Eye Bank; Research to Prevent Blindness, Diabetic Research Institute (Dr N Kenyon); UM DVR (Dr P Gulett and Dr B Collins); Henri and Flore Lesieur Foundation.
Keywords: anatomy • microscopy: electron microscopy • comparative anatomy