Customized Cairs In The Treatment Of Keratoconic Eye In Hong Kong: A Case Report

In this case report, we present our first case of Customized Corneal Allogenic Intrastromal Ring Segments (CAIRS) as a safe and effective treatment for keratoconus. This minimally invasive procedure offers an alternative for patients with keratoconus who have failed conservative measures, providing good visual and keratometric outcomes.

A 34-year-old Chinese man was referred to our clinic for blurred vision in his right eye, which affected his daily activities. He had previously tried rigid contact lenses but discontinued them due to lens-related discomfort. He was diagnosed with right eye keratoconus at stage two and the left eye at stage one, according to the Amsler-Krumeich classification.

His preoperative uncorrected visual acuity was 0.1 in the right eye and 0.05 in the left eye. Preoperative refraction was -6.5/-5.0x 50 with best corrected visual acuity (BCVA) of 1.0 in the right eye, and -4.75/-1.5x 150 with BCVA of 1.0 in the left eye. The average (Kmean) and maximum keratometry (KMax) of the right eye were 48.9 diopters(D) and 57.5D, respectively, with the thinnest corneal thickness of 465μm. The corneal topography showed asymmetric cones, with inferior cones being steeper.

Customized CAIRS for the right eye was performed. The donor corneal tissue, denuded of epithelium and endothelium, was trephined using a 6.5/8 mm double-blade system (Jacob CAIRS Trephine, Madhu Instruments). The tissue was then removed from the trephine and placed on the CAIRS customizer™ to mark and cut it to a 150-degree arc length and taper length. An intracorneal tunnel with an inner diameter of 4.6mm, a tunnel width of 1.5 mm, and a depth of 280μm was created using the LDV 8 femtosecond laser platform (Ziemer Ophthalmic Systems AG). The segment was inserted manually, ensuring that the total arc length and taper zone were well aligned with the marks placed on the patient’s cornea according to the topographic plan.

At eight months postoperatively, his unaided distance visual acuity was 0.15. The refraction was -2.5/-3.0x 32 with BCVA of 0.7 postoperatively. The patient was able to fit scleral contact lenses six months after the procedure, giving him BCVA of 0.7. Kmean, Kmax and the thinnest corneal thickness improved to 47.1D, 54.6D and 491μm, respectively. Higher-order Aberrations (HOA) and vertical coma, however, increased from 2.104μm to 2.886μm and from -1.858μm to -2.412μm, respectively. The patient experienced no surgical complications, and serial anterior segment Optical Coherence Tomography demonstrated that the ring segment was correctly positioned without extrusion.

This is the first report published in Hong Kong highlighting the effectiveness of customized CAIRS in a patient with keratoconus. The quality of visual acuity improved after surgery despite the increase in HOA. Larger studies with randomized controlled trials and longer follow-up are needed to further evaluate the long-term stability, safety, and optimal indications for customized CAIRS.