Photorefractive Keratectomy Modification of Postkeratoplasty Anisometropic Refractive Errors

Management of post-keratoplasty ametropia

Even after a successful corneal transplant, patients experience severe refractive errors, impeding their rehabilitation and satisfaction. Refractive errors can be caused by recipient pathology and corneal thickness, as well as intraoperative factors such as donor-host discrepancy, recipient's eccentric trephination, vitreous length, wound apposition, technique of suturing, and suture material. Also, wound healing and the interim between keratoplasty and suture removal contribute to astigmatism. Lamellar keratoplasty outperforms penetrating keratoplasty in terms of endothelial cell loss and endothelial graft rejection, yet the risk of developing refractive errors is comparable. Nonsurgical interventions such as spectacles and lenses fail to provide desirable vision in cases with high astigmatism and corneal irregularity. When these limitations are encountered, surgical interventions including incisional keratotomy, wedge resection, laser refractive surgeries, intracorneal segments, and intraocular lens implantation are employed. However, occasionally, none of these approaches deliver the desired effects, leading to the need for a repeat keratoplasty.

Refractive surgery after deep anterior lamellar keratoplasty: a review of the literature

PURPOSE

The main objective of this work is to present an updated review of the different surgical procedures for the correction of residual refractive errors following deep anterior lamellar keratoplasty (DALK) surgery.

METHODS

A review of the literature was conducted using PubMed, Web of Science, and Scopus databases. The search was conducted in January 2022 and was limited to articles published in peer-reviewed journals. The information extracted from each publication included sample size, mean follow-up time, pre- and post-operative uncorrected (UDVA) and corrected distance visual acuity (CDVA), pre- and post-operative refraction and spherical equivalent (SE), safety and efficacy indexes and complications.

RESULTS

Residual ametropias, mainly high astigmatism and myopia, and the resulting anisometropia are likely to occur following DALK. They become a limiting factor and may lead to unsatisfactory visual restoration, therefore affecting patients' quality of vision and life. Alternative surgical interventions may be required to treat this residual ametropia, such as corneal refractive surgery or intraocular lens implantation. A total of 47 relevant articles were studied in detail. Different refractive surgery techniques have been shown to be effective and safe for the correction of ametropia following the DALK procedure and to improve the patient's quality of vision, although more research is needed to confirm long-term results.

CONCLUSION

The final refractive technique will depend on different factors, such as the amount of ametropia, the condition of the cornea or the patient's individual needs, economics, and occupational demands.

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

Supplementary, Sulcus-Fixated Intraocular Lens in the Treatment of Spherical and Astigmatic Refractive Errors in Pseudophakic Eyes After Keratoplasty

PURPOSE

To evaluate the efficacy, refractive outcomes, and complications of supplementary intraocular lens (IOL) implantation in pseudophakic eyes after keratoplasty.

METHODS

This is a retrospective review of pseudophakic postkeratoplasty eyes after implantation of a custom-designed, sulcus-fixated, supplementary "piggyback" IOL to correct refractive errors. The outcome measures included preoperative and postoperative uncorrected distance visual acuity (UDVA), spectacle-corrected distance visual acuity (CDVA), refractive correction, and complications.

RESULTS

This study evaluated 10 eyes (10 patients) with previous penetrating or deep anterior lamellar keratoplasty with a mean follow-up period of 12.2 ± 10.7 months (range, 2-33 months). All eyes showed improved UDVA postoperatively with 70% achieving ≥20/40. Median UDVA (logarithm of the minimum angle of resolution) improved from 1.2 (20/280, range 20/70-20/2000) preoperatively to 0.3 (20/40, range 20/20-20/60) postoperatively at the latest follow-up visit (P < 0.01). Five eyes (50%) had improvement in CDVA by at least 1 line of Snellen acuity with all eyes achieving ≥20/40 and 70% achieving ≥20/25. Median CDVA (logarithm of the minimum angle of resolution) was 0.2 (20/30, range 20/20-20/50) preoperatively compared with 0.1 (20/25, range 20/20-20/40) postoperatively (P = 0.03). In 8 eyes that received toric secondary IOLs, the mean refractive astigmatism decreased by 84% from 5.7 diopters (D) (range, 4-9 D) to 0.9 D (range, 0.2-3.0 D) (P = 0.01). Postoperative refractive astigmatism was ±1 D of predicted astigmatism for 7 of 8 eyes. No eyes lost any lines of UDVA or CDVA, and there were no keratoplasty rejection/failure events.

CONCLUSIONS

Implantation of a supplementary, sulcus-based IOL is an effective approach to reduce spherical and astigmatic refractive errors in pseudophakic eyes after keratoplasty.

Excimer laser surface ablation: a review of recent literature

The aim was to review the recently published literature on excimer laser surface ablation procedures, including photorefractive keratectomy (PRK), laser sub-epithelial keratomileusis (LASEK), microkeratome-assisted PRK (epi-LASIK) and trans-epithelial (laser-assisted) PRK, to help elucidate where and how surface ablation may best fit into current refractive surgical practice. The emphasis was on publications within the last three years and included systemic reviews, meta-analyses and randomised controlled trials. Where such evidence did not exist, selective large series cohort studies, case-controlled studies and case series with follow-up preferably greater than six months were examined and included. Refractive and visual outcomes are excellent and comparable to those after LASIK even in complex cases after previous corneal surgery. Indeed, surface ablation combined with corneal collagen cross-linking may be used in selected eyes with biomechanical instability, where LASIK is contraindicated. In addition, there is evidence to suggest that there may be less induction of higher order aberrations with surface techniques. Long-term stability and safety appear to be extremely satisfactory. The literature supports the use of modern excimer laser surface treatments, with outcomes comparable to those after LASIK and evidence of less induction of higher-order aberrations. Follow-up studies at 10 to 20 years indicate excellent stability and safety.