Crosslinking

Corneal crosslinking (CXL) can safely and effectively be combined with a variety of adjuvant procedures such as intracorneal ring or phakic intraocular lens (IOL) implantation in order to stabilise the cornea and simultaneously deliver good functional vision in selected patients, George Kymionis MD, PhD told delegates attending the 6th EuCornea Congress in Barcelona, Spain.

“Adjuvant-combined procedures, whether Intacs, phakic refractive lenses or ablative procedures, maximise the effect and the benefits of simple CXL. The surgeon can customise the technique according to the patient’s preoperative data as there is no single rule that can be applied to every patient,” he said.

Dr Kymionis said that, while CXL has proven to be an excellent procedure in terms of halting the progression of keratoconic and ectatic corneas, some patients remain dissatisfied after treatment because of poor functional vision.

He cited the example of one of his first patients treated for progressive keratoconus in 2006. Before treatment, her uncorrected visual acuity (UCVA) was 20/100 and she was contact lens- and spectacle-intolerant. She also had a corneal thickness of around 490 microns. Three years after CXL, the topography maps showed that the keratoconus had stabilised or even slightly improved.

“While this made the doctor happy, the patient was still very unhappy as she had both poor UCVA and poor best spectacle-corrected visual acuity (BSCVA), and she was still not able to wear contact lenses or glasses,” said Dr Kymionis, Department
of Ophthalmology, Medical School, National and Kapodistrian University of Athens, Greece.

BETTER FUNCTIONAL VISION

This scenario, where the patient has been effectively “cured” but remains unhappy because of poor quality of vision, prompted Dr Kymionis to experiment with adjuvant refractive treatments that might provide better functional vision for these patients.

Potential combined treatments with CXL, which Dr Kymionis has termed “CXL-plus”, include intrastromal corneal ring segment implantation, photorefractive keratectomy (PRK), transepithelial phototherapeutic keratectomy (PTK), phakic IOL implantation, and multiple combined procedures. CXL treatment in combination with intracorneal ring segment implantation can be an effective treatment, said Dr Kymionis, as the synergic influence of the two procedures can partially reverse the progressive irregular astigmatism and result in favourable outcomes for the patient. The ring segments are placed first, followed by CXL treatment.

Another option to implant a toric intraocular contact lens also worked quite well, but was not effective for treating irregular astigmatism, he said.

Topography-guided PRK followed by CXL has also delivered good results, said Dr Kymionis. Several studies have shown that keratoconic patients treated with simultaneous topography-guided PRK followed by CXL showed significant improvement in best corrected visual acuity, UCVA and keratometric values. In a long-term study of simultaneous topography-guided PRK followed by CXL in a series of keratoconic patients recently published by Dr Kymionis, all patients showed marked improvement of corneal irregularity and visual acuity over the follow-up period.

In a comparative case series of 38 eyes, Dr Kymionis and co-workers showed that epithelial removal using transepithelial PTK during CXL (Cretan protocol) resulted in better visual and refractive outcomes compared with mechanical epithelial debridement.

Because some uncertainty remains as to the optimal strategies for each patient, a decision tree can be usefully employed to ensure optimal patient management, said Dr Kymionis.

After diagnosis of keratoconus, patients with deep scar, very thin corneas, and low visual acuity with rigid gas permeable (RGP) contact lenses are probably likely candidates for deep anterior lamellar keratoplasty (DALK) or penetrating keratoplasty (PKP). If none of these criteria are present and the keratoconus is progressive, then patients with acceptable visual acuity and good contact lens tolerance can undergo CXL.

Poor visual acuity and contact lens intolerance means that CXL-plus may be considered. Likewise, CXL-plus may be an option in cases of no progression with poor visual acuity, said Dr Kymionis.

Summing up, Dr Kymionis said that combined treatments seem to be the way to optimise the result of CXL treatment for keratoconus, although further studies with longer follow-up are needed to confirm the promising results of this approach.

George Kymionis: kymionis@med.uoc.gr