Effect Of Hydration And Dehydration On Femtosecond Laser-Prepared Corneal Allogenic Intrastromal Ring Segments (Ca) – Comparison Of Thickness Rates

Corneal allogenic intrastromal ring segments (CAIRS) are increasingly used to treat corneal ectasia, especially keratoconus. Surgical effectiveness depends heavily on segment thickness at the time of implantation. However, CAIRS hydration behavior varies by storage medium, and optimal hydration parameters remain unclear. This study compares the thickness changes of femtosecond laser–prepared CAIRS during controlled dehydration and hydration

Experimental study performed at the Lions World Vision Institute

CAIRS 550 µm target thickness; widths 0.75, 1.00, and 2.00 mm were created using a Zimmer 8 femtosecond laser. Segments were placed in sealed, clear containers over a sponge to regulate evaporation:

Group 1 (G1): NS solution (0.75 & 2.00 mm);

Group 2 (G2): Human albumin (0.75 & 1.00 mm);

Group 3 (G3): Air exposure (0.75 mm).

Thickness was measured using OCT during the dehydration and rehydration phases

In G1 (NS), dehydration over 19 days reduced thickness from 658 µm to 220 µm; rehydration over 9 days increased thickness to 465 µm, then plateaued. In G2 (albumin), dehydration reduced thickness from 660 µm to 290 µm in 20 min; hydration increased thickness to 915 µm within 10 min, exceeding original values. In G3 (air), dehydration reduced the thickness from 650 µm to 220 µm in 20 min; hydration increased the thickness to 740 µm within 1 hour.

The hydration medium strongly influences CAIRS thickness. Albumin caused rapid and excessive swelling, air allowed moderate recovery, and saline led to slow, incomplete rehydration. These findings highlight the importance of controlled hydration to achieve a predictable CAIRS thickness before implantation.