A 37-year-old man with keratoconus (Fig. 1A) could not tolerate RGP lens-wearing and did not want to have a corneal transplant or other corneal surgeries. He had been using RGP contact lenses in both eyes for 10 years. He was diagnosed with unilateral keratoconus of the left eye. Stable keratoconus was confirmed with refraction and corneal topography for 7 years (Fig. 1B and 1C). In the right eye, the UCVA was 0.04 and the BSCVA was 0.7 with -3.75 -3.00 × 155A. In the left eye, the UCVA was 0.02, and the BSCVA was 0.4 with -12.00 -3.50 × 30A. The corneal refractive power was 58.40 / 48.70 diopters × 117A in the left eye (Fig. 1C). With manifest refraction, a BSCVA of 0.4 was achieved. He was told that the maximal possible visual correction would be 0.4 or less because irregular astigmatism could not be corrected with toric ICL implantation. With informed consent, toric ICL implantation was performed without any surgical complications. After surgery, the manifest refraction became -0.75 × 180A with a UCVA of 0.5 and BSCVA of 0.7 at 1 month, which then shifted to +2.25 -0.50 × 180A with a UCVA of 0.4 and BSCVA of 0.7 at 9 months, and to -1.75 × 180A with a UCVA of 0.2 and BSCVA of 0.5 at 20 months. The anterior chamber depth, from the endothelium to the ICL, decreased from 2.21 mm at 1 month to 2.13 mm at 9 months follow-up, corresponding with mild corneal flattening and transient hyperopic changes (Fig. 1D), without any vault changes (Fig. 1E and 1F). At the last follow-up, 20 months after surgery, the ICL vault was decreased, resulting in mild deepening of the ACD from 2.13 mm to 2.17 mm, and the manifest refraction results finally stabilized at mild myopic astigmatism (Fig. 1G). The efficacy and safety index were 1.0 and 1.75 at 9 months and 0.5 and 1.25 at 20 months (Table 1). Postoperative contrast sensitivity was also enhanced (Fig. 1H).

Toric ICL has been used as an alternative for the correction of high myopic astigmatism in eyes with stable keratoconus, though irregular astigmatism is a concern due to its ability to interfere with visual rehabilitation [15]. The two-step procedure of combining intrastromal corneal rings and phakic intraocular lens implantation may be another alternative treatment option for keratoconus with high myopic astigmatism. Toric ICL may have advantages in terms of expense, time, and being a one-step procedure. Toric ICL implantation can improve clinically useful vision even if perfect vision cannot be achieved in patients with advanced stable keratoconus. In our case, the patient was satisfied with partial visual rehabilitation because his daily activities could be comfortably performed with his spectacles-corrected vision with his ICL implants.

There are still issues regarding toric ICL target diopter, which may not be precisely calculated exactly in keratoconus and postoperative refractive changes due to keratoconus progression. We used the astigmatism decomposition method recommended by the manufacturer (STAAR Surgical) to perform the toric ICL power calculation [17]. Exact calculation of the target diopter, however, is more difficult in keratoconus than in other high myopic astigmatism conditions due to the difficulty of achieving a precise keratometric reading and manifest refraction. Moshirfar et al. [18] reported that phakic ICL selection for emmetropia in keratoconus eyes with high myopic astigmatism may lead to hyperopia. Our patient had a transient hyperopic shift that appeared to be associated with a suspicious progression of scarring that resulted in flattening of the cornea and subsequent shallowing of the anterior chamber depth. This hyperopic change resolved with decreasing the ICL vault and the refraction stabilized by 20 months follow-up. Despite transient refractive changes during the follow-up, the visual improvement with correction was maintained, and the patient was satisfied with the postoperative vision and the lack of postoperative complications. It is important that the patient is well informed before the surgery of possible visual fluctuations and only a partial restoration of vision.

Because toric ICL aims to correct spherical and cylindrical errors, it cannot correct a large amount of high order aberrations caused by irregular shapes of the cornea. After a toric ICL implantation, our patient still had a similar amount of high order aberrations despite correcting the high myopic astigmatism.

It is important to choose adequate candidates for toric ICL implantation. Examples include patients with RGP intolerance, stable keratoconus, or fear of corneal surgery. To select suitable candidates, correction of high myopia and astigmatism with spectacles before the surgery should be tried in the clinic.

Recently, to reduce both irregular astigmatism and high myopia, cross-linking, or corneal ring implantation combined with toric ICL, has been newly adapted for treating keratoconus. Nevertheless, our case report suggests that toric ICL implantation may be a possible alternative surgical option for the partial visual rehabilitation of high myopic astigmatism in keratoconus patients with RGP contact lens intolerance who do not want to have a corneal transplant or other corneal surgeries.