KERATOCONUS TREATMENT

A combination of modalities stops keratoconus progression and provides improved refraction

A succession of refractive treatments involving intracorneal ring segments, collagen cross-linking and a toric ICL can stop the progression of keratoconus, reduce corneal irregularity and fine-tune refraction if the patient is contact lens intolerant, said Efekan Coskunseven MD, at a special meeting at the Dunya Eye Hospital, Istanbul, Turkey, devoted to the treatment of keratoconus.

'Our first choice when dealing with keratoconus should be contact lenses and cross-linking. In patients who are not good candidates for contact lenses, we can combine the ring with cross-linking. There are many studies about this combination. We can also combine the ring, cross-linking, and implantation of a phakic IOL,' he said.

Dr Coskunseven presented the results of a study in which 14 eyes of nine patients with keratoconus underwent intracorneal ring segment implantation, using the Keraring (Mediphacos), followed by corneal cross-linking and implantation of a toric ICL over a period of around 13.5 months.

He noted that the mean uncorrected visual acuity improved from a preoperative value of 0.01 to 0.06 following intracorneal ring segment implantation, to 0.08 following collagen cross-linking and to 0.46 following implantation of the toric ICL. Best-corrected visual acuity improved from 0.16 preoperatively to 0.41 following implantation of the intracorneal ring, to 0.48 following cross-linking and to 0.58 following ICL implantation.

Furthermore, mean cylinder improved from a preoperative value of -4.73 D to -2.36 D following intracorneal ring segment implantation, to -1.8 D following cross-linking and to -0.96 D following ICL implantation. In addition, spherical equivalent improved from a preoperative value of -16.4 D to -9.81 D following intracorneal ring implantation, to -9.56 following cross-linking, and to -0.8 D following ICL implantation.

The inclusion criteria for the study were stage I through stage III keratoconus, age of more than 18 years, contact lens intolerance, corneal thickness of at least 400 microns where the tunnels were created for implantation of the intracorneal ring segments, and anterior chamber depth greater than 2.8mm.

Patients were excluded from the study if they had keratometry readings of 65 D or more, or if they had corneal dystrophies, hydrops, corneal opacities, or herpetic keratitis. Also excluded were severely atopic patients and those with collagen, vascular or autoimmune diseases or other systemic diseases.

The mean interval between the implantation of the intracorneal ring and collagen cross-linking was seven months and the mean interval between collagen cross-linking and ICL Toric implantation was 8.4 months. The mean follow-up period was 7.2 months.

Dr Coskunseven created the channels with an IntraLase FS 60 femtosecond laser in a procedure that took 15 seconds with the depth adjusted to 80 per cent of the thinnest point at the tunnel's location. He created the corneal incision at the steep axis and implanted ring segments ranging from 4.4 to 5.6mm in length.

He performed collagen cross-linking by applying to the cornea 0.1 per cent riboflavin in 20 per cent dextran T-500 for 30 minutes and then exposing it to three milliwatts/cm² ultraviolet light at a wavelength of 370 nm for 30 minutes. He based his ICL calculation refraction on the eye's refraction following intracorneal ring implantation and collagen cross-linking.

Many combined approaches possible Dr Coskunseven noted that the Keraring, cross-linking and toric phakic IOL combination is only one of several approaches that employ a combination of modalities for the treatment of keratoconus.

Another approach that has shown efficacy is the use of a simple combination of the toric ICL and collagen cross-linking. In a study by Mohamed Shafik MD, PhD, University of Alexandria, the mean best-corrected visual acuity increased from 0.56 to 0.89 and the mean uncorrected visual acuity increased from 0.3 to 0.88, Dr Coskunseven noted. However, he pointed out that in some cases the irregularity of cornea in some keratoconus patients would be too much for this treatment to work.

In stable keratoconus patients, intracorneal ring segments and toric IOLs without cross-linking can produce good results, he noted. In a study he and his associates conducted the combination of Intacs and the toric ICL brought two highly myopic keratoconus patients to within one dioptre of emmetropia. The treatment combination also reduced the mean manifest refractive spherical equivalent refraction from −18.50 D to 0.42 D and improved uncorrected visual acuity by seven lines and best corrected visual acuity by four lines.

Another approach Dr Coskunseven has used is intracorneal ring segment implantation followed by collagen cross-linking and topography-guided transepithelial PRK. In a study involving 16 eyes of 10 patients with keratoconus that underwent that combination of treatments UCVA improved from 0.1 to 0.58, and BSCVA improved from 0.21 to 0.74.

Dr Coskunseven noted that the range of treatments now available are bringing keratoconus patients with high amounts of irregularity and refractive error closer and closer to emmetropia, with all of the treatment options having an additive effect when used in combination.

'Maybe we should combine all of them to get better results,' he said.