In comparison to corneal contact lenses, scleral lenses bulge outward considerably more. Pneumatic retinopexy has significantly lower success rates compared to scleral buckle surgery and vitrectomy. Examination of the eyelid conjunctiva is usually more diagnostic than examination of the scleral conjunctiva. The nerves enter the cornea via three levels; "scleral, episcleral and conjunctival". Radial scleral buckle is indicated for U-shaped tears or Fishmouth tears, and posterior breaks. Circumferential scleral buckle is indicated for multiple breaks, anterior breaks and wide breaks. Modern scleral lenses are made of a highly oxygen permeable polymer. The peripheral portions of the retina are sometimes pushed into view using scleral depression. Development of scleral nodule associated with sarcoidosis has been observed. This is sometimes referred to as "scleral icterus". A link between scleral buckles and Adie syndrome may exist. The most common side effect of a scleral operation is myopic shift. A scleral lens is a prototypical lens dating back to the early 1880s. Scleral buckles come in many shapes and sizes. Scleral covering carries with it the risk of transmission of infection, inflammation, and rejection.