Rings in the Cornea!⁣


Intracorneal Ring Segments⁣




● Two tiny clear crescent-shaped pieces of PMMA 150 degree inserted into the⁣

cornea⁣

● Placed in mid-corneal peripheral stroma at approximately 2⁄3 depth outside⁣

central optical zone to reshape anterior corneal surface while maintaining⁣

prolate profile (positive asphericity) of cornea⁣

● Act as spacer elements between the bundles of corneal lamellae producing a⁣

shortening of the central arc length (arc shortening effect) that is proportional to⁣

thickness of device⁣

● Central portion of anterior corneal surface tends to flatten and peripheral⁣

area adjacent to ring insertion is displaced forward ⁣

Most common type of ICRS : ​INTACS⁣

Hexagonal transverse shape - 8.1 mm external & 6.8 mm internal diameter ⁣

Refractive effect is modulated by thickness (0.25-0.45 mm, with 0.05-mm increments)- current designs have a predicted myopic range of correction from -1.00 to -4.10 D⁣

Incision made with femtosecond laser or mechanically with a diamond knife and a tunnel created by a dissector into which the ring segments are placed⁣

Other types: Ferrara rings, KeraRing, MyoRing, Bisantis Segments⁣

Requirements: Age >21 years⁣

Clear, central cornea⁣

Minimum corneal thickness of 450 microns at incision site⁣

Mesopic pupil size of less than 6 mm⁣

Indications:⁣

Low myopia⁣

Progressive keratoconus⁣

Ectasia after LASIK⁣

Residual myopia after LASIK⁣

Pellucid marginal degeneration⁣

Contraindications:⁣

● Keratoconus patients who can achieve functional vision on a daily basis using contact lenses⁣

● Age <21 y⁣

● Dont have clear central corneas⁣

● Corneal thickness < 450 μ at proposed incision site⁣

● Patients with collagen vascular/autoimmune diseases⁣

● Ocular conditions - recurrent corneal erosions, corneal dystrophy⁣

● Systemic diseases which affect wound healing -diabetes⁣

Advantages:⁣

● Leaves central cornea undisturbed⁣

● Rapid results, predictable⁣

● Reversible⁣

● Corneal asphericity is maintained with minimal adverse effects⁣

Complications:⁣

● Epithelial defects⁣

● Channel haze⁣

● Under/ Over-corrections⁣

● Sterile infiltrates/ epithelial cysts⁣

● Ring extrusion⁣

● Cornea thinning ⁣

● Infectious keratitis


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