{'fraction_non_alphanumeric': 0.03863134657836645, 'fraction_numerical': 0.0380794701986755, 'mean_word_length': 5.043333333333333, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
LUMINAL CHARACTERISTICS OF CENTRAL RETINAL VESSELS IN THE ANTERIOR OPTIC NERVE OF THE YOUNG HUMAN

Purpose To study the luminal characteristics of the central retinal vessels of young humans where the vessels pass through the anterior optic nerve. Methods Serial sections of nine central retinal arteries (CRAs) and 13 central retinal veins (CRVs) from 12 eyes of 12 young donors (aged 20–29 years) without known ocular disease or anatomic malformation were examined by image analysis to determine their luminal dimensional differences right at, anterior to, and posterior to the lamina cribrosa. Results The average values of the mean area of the CRAs in the prelaminar, laminar, and retrolaminar portions were 16.5 × 103 &mgr;m2, 17.2 × 103 &mgr;m2, and 15.2 × 103 &mgr;m2, and mean perimetric lengths were 541 &mgr;m, 528 &mgr;m, and 492 &mgr;m, respectively. Differences were detected in perimetric length and theoretical luminal area between the laminar and retrolaminar portions, but not the prelaminar and laminar portions. The average values of the mean area of the CRVs in the prelaminar, laminar, and retrolaminar portions were 24.6 × 103 &mgr;m2, 13.3 × 103 &mgr;m2, and 7.8 × 103 &mgr;m2, and mean perimetric lengths were 689 &mgr;m, 544 &mgr;m, and 411 &mgr;m, respectively. There were marked differences between the prelaminar and laminar values and between the laminar and retrolaminar values in terms of the perimetric lengths and theoretical luminal areas. Conclusions The results suggest that the resistance of blood flow in CRAs decreases when the blood enters the eye. The gradual constriction of CRVs from the prelaminar to the retrolaminar portion may act as a throttle mechanism in controlling the outflow of the blood and in maintaining the patency of the retinal venules and capillaries.