During implantation of intracorneal ring segments (Intacs) for keratoconus, the segments are inserted into tunnels created at approximately what depth of the cornea, relative to the thinnest point pachymetry?
- A 25 percent
- B 40 percent
- C 60 to 70 percent ✓
- D 90 percent, just above Descemet membrane
Correct answer: C. 60 to 70 percent
Explanation
Intracorneal ring segments are placed in stromal tunnels at roughly 60 to 70 percent depth measured from the thinnest corneal point, deep enough to avoid extrusion and superficial vascularisation yet safely away from Descemet membrane. By adding mass to the mid-periphery the arcs shorten the arc length of the cone, flattening the apex centrally and reducing irregular astigmatism. Too shallow a tunnel leads to segment extrusion or erosion, a recognised complication.
Reference: AAO Basic and Clinical Science Course, Section 13: Refractive Surgery, 2022-2023 ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.