Branching Pattern of Central Artery of Retina on the Optic Disc

Background: The central artery of retina (CRA), on reaching the optic disc, divides into two branches of the first order - superior and inferior. Each of these divides into two branches of the second order – temporal and nasal. Emergence of CRA on the optic disc and further sequence division is not constant. Anomalies in the branching pattern of CRA may be associated with certain optic disc abnormalities like optic disc drusen, optic disc pits, or colobomas. The objectives of the study are: 1) To identify the variations in the number of branches of CRA emerging on the optic disc, 2) to study the variations in the number of branches arising from the main trunk on the optic disc, and 3) to study the variations in the shape of branching pattern of CRA on the optic disc. Methodology: This observational study was carried out at AIIMS, Guwahati, with the approval of the IEC. Sample size is 160 subjects with 320 fundus images. Subjects with diabetes, hypertension, and other vascular diseases are excluded. The fundus examination was carried out with a fundus camera, and digital photographs were taken. Then the images are magnified to get a clear picture of the optic disc. Images are analyzed by two observers. Results: In the present study, the CRA emerged on the optic disc as one (82.8%), two (13.1%), and three (4%) branches. Number of first-degree branches observed on the optic disc is two – superior and inferior (74.7%), three – superior, inferior, and nasal (10.9%), superior, inferior, and macular (8.3%), and four – superior, inferior, nasal, and macular (6%). The shape of branching patterns of the central artery on the optic disc observed are X-shape type I (52.5%), X-shape type II (7.5%), X-shape type III (8.1%), Y-shape (10%), inverted Y-shape (8.1%), double V-shape (7.5%), inverted V-shape (4%), and Zeta-shape (2.1%). Conclusion: Knowledge of the typical branching pattern of the central artery of retina can aid in interpreting diagnostic imaging studies such as fundus photography, fluorescein angiography, indocyanine green (ICG) angiography, fundus autofluorescence, optical coherence tomography, and retinal vascular imaging. It can help in identifying landmarks and interpreting images accurately for diagnostic purposes. KEY WORDS: Central Artery of Retina, Branching, Optic Disc, Variation.