Tuesday, March 21, 2006

What are the landmarks of the limbus?

The limbus is a transition zone where the cornea meets with elements of the sclera; both contribute. The transition zone begins at a line (the green arrow in the figure) designated by the termination of Bowman's layer and Descemet's membrane. The transition ends at a line (the red line in the figure)designated by the scleral spur drawn perpendicular to the ocular surface. The transition zone with these limits is then a donut that is about 1.5 mm in width. The surgical limbus has been stated in many books to have clear landmarks that include Bowman's layer. Since Bowman's layer is not readily visible in the slit lamp consider the limbus as the blue region overlying clear cornea and extending back to the scleral spur. The limbus is an important landmark for surgical procedures for cataract extraction, glaucoma filtration surgery etc. . Because the trabecular meshwork is encompassed in this region, the limbus has implications in the laser treatment for glaucoma.


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