Intrastromal corneal ring segments (ICRS) improve vision in keratoconus primarily by:

• A Adding refractive power at the cone apex
• B Inducing controlled scarring that stiffens the cone
• C Shortening corneal collagen lamellae arc length, thereby flattening the central cone ✓
• D Replacing the thinned stroma with synthetic tissue

Explanation

Ring segments act on the principle that inserting material into the peripheral stroma shortens the arc length of the overlying lamellae, which flattens the central cornea and reduces myopia and irregular astigmatism. They are additive procedures that do not remove tissue and do not halt progression, so they suit contact lens intolerant patients with clear cones. Scarring is a complication, not the intended mechanism, and CXL remains the progression-halting option.

Reference: Parsons' Diseases of the Eye, 23rd ed.

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Written and medically reviewed by the StethoPrep medical team.