<prompt> Sclera, the protective covering of the eye, is thinnest at the following site:ApexLimbusIn front of inseion of rectus muscleBehind inseion of rectus muscle  <response>: The sclera is the fibrous outer coating of the eye, consisting almost entirely of collagen. It is 1 mm thick posteriorly, 0.66 mm at the inseions of the rectus muscles, 0.33 mm beneath the rectus muscles and is thinnest just behind their inseions. Ref: Parsons Diseases of the Eye By Ramanjit Sihota Radhika Tandon, 21st edition, Page 218. 