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Anatomical Study of Schlemm's Canal and Aqueous Veins by means of Neoprene Casts : III. Arterial Relations of Schlemm's Canal

1953; BMJ; Volume: 37; Issue: 10 Linguagem: Inglês

10.1136/bjo.37.10.577

1468-2079

Nicholas J. Ashton, Richard Smith,

Vascular anomalies and interventions

IN previous studies of this region (Ashton 1951, 1952), it has been shown that the canal of Schlemm and its efferent connections may be clearly demon- strated by Neoprene latex casts, prepared by direct injection of the canal followed by enzyme digestion of the ocular tissues.Over 200 casts have now been studied by this technique and while the preparations in the main confirm the anatomical accounts of earlier workers, who used serial sections or injections of ink and gelatin followed by clearing, they have the advantage of showing the exact anatomy of the canal in its entirety and in a stereoscopic way that can be readily appreciated.The study has revealed some minor but important deviations from the classical descriptions and these will be discussed in a subsequent communication dealing in detail with the structure and connections of the canal itself.It is the purpose of this paper to describe the arterial relationships of Schlemm's canal as observed in cast preparations.The vessels involved are the anterior ciliary and the long posterior ciliary arteries which originate indirectly from the ophthalmic artery and meet again at the major circle of the iris, the anterior having pursued a mainly extra- ocular and the posterior a mainly intra-ocular course.According to the classical description of Leber (1903), anterior ciliary arteries run forward on the tendons of the rectus muscles; there are usually two on each of the recti, except the lateral on which there is only one.Uncommonly one of the arteries may be derived from the vessels in the eyelid.As the vessels approach the limbus, they divide and subdivide into smaller and smaller branches.The larger divisions pass into the eye through perforating scleral channels to join the arterial circle of the iris.The smallest remain in the episclera and pass forward to the limbus, where they loop backward to contribute to the anterior conjunctival arteries, while others dip down through the sclera to reach the deeper parts of the corneal limbus immediately external to the canal, or extend more deeply towards the canal itself.The further destination of these latter arterial twigs is a matter of great interest and considerable controversy.According to Maggiore (1917) and Dvorak-Theobald (1934) they tend to run in a circular fashion, accompanying the canal to form an incomplete arterial circle in close association with it, so close, in fact, that they may cause irregularities in the canal wall; indeed, Wolff (1945) has depicted a small artery apparently lying within its lumen.