Customized photorefractive keratectomy to correct high ametropia after penetrating keratoplasty: A pilot study

Outcomes of Photorefractive Keratectomy After Corneal Graft: Brief Review

PURPOSE

The purpose of this brief review is to analyze the outcomes of customized photorefractive keratectomy in the correction of refractive errors and irregular astigmatism after corneal graft surgery.

METHODS

Two reviewers (M.S.K. and J.L.A.) independently performed a literature search in the MEDLINE/PubMed database, Google Scholar, and ResearchGate from January 2001 to October 2023. To analyze the efficacy, safety, and predictability of the procedure, primary outcomes such as mean change in uncorrected distance visual acuity, corrected distance visual acuity, and root mean square value (RMS) of higher order aberrations were studied. The complications and adverse reactions were analyzed to predict the safety of this procedure.

RESULTS

We identified those studies where customized (topography guided/wavefront guided) photograph refractive keratectomy was performed in patients with postkeratoplasty. Significant change in uncorrected distance visual acuity, corrected distance visual acuity, RMS of higher order aberrations, refractive cylinder, and mean spherical equivalent were observed. Corneal haze was the most common complication documented; however, this was more commonly documented by authors who have not used Mitomycin C in their patients.

CONCLUSIONS

We found out that customized photograph refractive keratectomy is a safe, effective, and predictable method of treatment for refractive error and irregular astigmatism after keratoplasty.

[Surgical technique of keratoplasty with simultaneous implantation of a continuous ring or ring segment into the graft]

The article presents the surgical technique of penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) with femtosecond-laser assistance involving simultaneous implantation of an intracorneal continuous ring (ICCR) or an intracorneal ring segment (ICRS) into the graft. Surgical technique no. 1 - keratoplasty with simultaneous implantation of ICRS. Intrastromal circular tunnel is formed in the central zone of donor cornea using femtosecond laser. Then penetrating trepanation 8.1 mm in diameter is performed symmetrically to the formed tunnel. After preparing penetrating or lamellar recipient bed, suture fixation is placed in the corneal transplant, then the ICRS is implanted into the graft. Surgical technique no. 2 - keratoplasty with simultaneous implantation of ICCR. The donor cornea is dissected from periphery to center using femtosecond laser. Central zone remains untouched. A large diameter full-thickness trepanation is performed and the donor cornea is divided into the anterior and posterior layers. The ICCR is put on the donor cornea while holding the posterior layer with forceps. Penetrating or lamellar recipient bed is prepared, then the corneal graft is fixed with sutures. Transparent corneal graft acceptance does not guarantee high visual acuity due to post-keratoplasty astigmatism. Surgical correction of astigmatism is performed in the long term post-operatively and isn't effective enough. We proposed this new surgical technique of keratoplasty with simultaneous implantation of ICCR and ICRS into the graft as close as possible to the visual axis of the eye, which can help make the postoperative astigmatism minimal both immediately after surgery and in the long term. The study proposes a new approach to intraoperative prevention of post-keratoplasty astigmatism. The technique is simple, safe and effective. Analysis of long-term outcomes is required before recommending this method for widespread use in clinical practice.

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.

Combined photorefractive keratectomy and corneal collagen cross-linking for treatment of keratoconus: a 2-year follow-up study

Background:

Corneal collagen cross-linking (CXL) is considered an effective procedure for slowing down or eliminating the progression of keratoconus. New techniques, in combination with CXL, have been proposed to stop the evolution of keratoconus and improve the visual function.

Objective:

To evaluate the effectiveness of combined photorefractive keratectomy (PRK) with mitomycin-C (MMC) application and CXL in the management of grade 1–2 keratoconus over a 2-year follow-up.

Methods:

Fifteen eyes underwent topography-guided PRK with 0.02% MMC application immediately followed by standard CXL.

Results:

Best corrected visual acuity improved from 0.15 ± 0.11 logMAR to 0.08 ± 0.09 logMAR at 24 months (p < 0.0001) in treated eyes. Mean steepest meridian keratometry reduced from 48.79 ± 3.22 D at baseline to 46.16 ± 3.11 D at 24 months (p < 0.0001). Mean flattest meridian keratometry reduced from 45.18 ± 2.17 D preoperatively to 44.35 ± 2.19 D at 24 months (p < 0.0001).

Conclusion:

Simultaneous topography-guided PRK with MMC 0.02% application and standard CXL is a safe, promising and effective procedure in the treatment of mild and moderate keratoconus.

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.

Topography-Guided Trans-Epithelial No-Touch Photorefractive Keratectomy for High Irregular Astigmatism After Penetrating Keratoplasty: A Prospective 12-Months Follow-Up

Purpose

To describe the efficacy and safety of topography-guided trans-epithelial no-touch photorefractive keratectomy (PRK) for the correction of highly irregular astigmatism after penetrating keratoplasty (PK).

Patients and Methods

A prospective study was conducted on 12 eyes of 12 patients affected by highly irregular astigmatism after PK for keratoconus. Each patient underwent a single-step topography-guided trans-epithelial ablation (CIPTA^®2 software, iVis Technologies). Corneal topography data as well as uncorrected (UDVA) and corrected distance visual acuity (CDVA) and spherical equivalent (SEQ) were collected preoperatively (T0) and at 1 (T1), 3 (T2) and 12 (T3) months after surgery.

Results

Mean UDVA and CDVA significantly improved, respectively, from 1.22±0.17 and 0.18±0.03LogMAR at T0 to 0.63±0.17 (CI 95%, P<0.001) and 0.04±0.03LogMAR at T3 (CI 95%, P<0.001). Mean SEQ significantly decreased from −3.75±1.32 to –1.60±1.32D (CI 95%, P<0.02). Mean subjective refractive astigmatism (SRAST) and mean keratometry astigmatism (SimK) significantly decreased, respectively, from 7.83±0.98 and 8.10±1.48D to 2.83±0.98 and 5.29±1.48D (CI 95%, P<0.001). Corneal Morphological Irregularity index (CMI) significantly decreased from 62.76±7.26 µm to 23.24±7.26 µm (CI 95%, P<0.001). Apart from a single episode of graft rejection 5 days after ablation, successfully reverted with topical steroids, no other complications were noted. A mild corneal haze was observed in two eyes (16.7%) at 3 months post-PRK, and no regression was observed at 12 months.

Conclusion

Our study demonstrates the safety and long-term effectiveness of a trans-epithelial topography-guided ablation in the treatment of post-PK highly irregular astigmatism.

Aberrometric, Keratometric, and Visual Outcomes After Trans-Epithelial Topography-Guided Phototherapeutic Keratectomy for the Treatment of Irregular Corneas

Purpose

To assess the safety, aberrometric and keratometric changes, and stability of trans-epithelial topography-guided phototherapeutic keratectomy (TE-TG-PTK) with mitomycin C (MMC) using the ALLEGRO Topolyzer platform for the treatment of irregular astigmatism.

Methods

This is a retrospective case series including 57 eyes that underwent TE-TG-PTK + MMC using the ALLEGRO Topolyzer platform for the treatment of irregular astigmatism. CDVA, manifest refraction (MR), keratometry readings, and aberrometry readings were analyzed at 1, 3, 6, and 12 months.

Results

Causes of corneal irregularity included non-infectious leucoma (n=23), infectious leucoma (n=7), adenoviral keratitis (n=20), corneal haze (n=2), post-penetrant keratoplasty (PKP) (n=1), and others (n=4). Overall, 76% of the eyes (n=40) gained lines of vision; patients gained 1, and 2 or more lines of vision in 76%, and 38% of cases, respectively. Only 1 patient (2%) lost 5 lines of vision. Mean preoperative CDVA (LogMAR) was 0.37 ±0.31 and improved to 0.14 ±0.18 (p<0.001) at final follow-up (12 months). CDVA remained unchanged in 10 eyes (21%). No significant changes were observed in mean keratometry (Kmean) and keratometric astigmatism readings. Regarding aberrometry, only changes in coma proved to be significant 6 months after surgery (P<0.01). No intraoperative/postoperative complications were reported.

Conclusion

At final follow-up, significant improvements were observed in CDVA and coma. TE-TG-PTK + MMC proved to be an effective and safe procedure for the treatment of corneal irregular astigmatism due to several causes.

Small Incision Lenticule Extraction for Postkeratoplasty Myopia and Astigmatism

Purpose. To evaluate the visual and refractive outcomes after small incision lenticule extraction (SMILE) for treating myopia and myopic astigmatism after penetrating keratoplasty (PKP). Design. Case-series. Methods. Ten eyes of 10 patients with previous PKP and residual myopic astigmatism for whom pentacam imaging and thickness measurements were acceptable for laser vision correction. Manifest refraction (MR), uncorrected distance visual acuity (UDVA), and corrected distance visual acuity (CDVA) were obtained preoperatively and one day, one week, and one, 3, and 6 months postoperatively. Cases were operated on the VisuMax® femtosecond laser platform with 500 kHz repetition rate. Results. The mean correction ratio for spherical errors was 0.84 ± 0.19 D and for the mean refractive spherical equivalent (MRSE) was 0.79 ± 0.13 D. Vector analysis showed a mean astigmatism reduction at the intended axis of 67 ± 25.25%, a correction index of 0.81 ± 0.21, and an overall mean percentage of success of astigmatism surgery of 53 ± 37.9%. The postoperative MRSE was stable throughout the 6-month follow-up period. The efficacy index was 0.93 and the safety index was 1.12. Conclusion. SMILE for correction of post-PKP myopia and astigmatism is effective, safe, and stable with moderate accuracy and predictability. Centration of the treatment within the grafts was easily performed.

Efficacy of Wavefront-guided Photorefractive Keratectomy with Iris Registration for Management of Moderate to High Astigmatism by Advanced Personalized Treatment Nomogram

Purpose:

To evaluate the efficacy of photorefractive keratectomy (PRK) using the advanced personalized treatment (APT) nomogram for correction of moderate to high astigmatism.

Methods:

This prospective interventional case series included 60 consecutive eyes of 30 patients undergoing wavefront-guided PRK (Zyoptix 217 Z100 excimer laser, Bausch & Lomb, Munich, Germany) using the APT nomogram and iris registration for myopic astigmatism. Mitomycin-C was applied intraoperatively in all eyes. Ophthalmic examination was performed preoperatively and 1, 3 and 6 months postoperatively.

Results:

Preoperatively, mean sphere was -1.68 ± 2.08 diopters (D), mean refractive astigmatism was -3.04 ± 1.05 D and mean spherical equivalent (SE) was -3.12 ± 1.77 D. Six months postoperatively, mean sphere was + 0.60 ± 0.64 D (P < 0.005), mean cylinder was -0.43 ± 0.46 D (P < 0.005) and mean SE was + 0.28 ± 0.48 D (P < 0.005). Hyperopic overcorrection (≥ +1.0 D) occurred in 3 (5%) eyes. Postoperatively, root mean square (RMS) of higher order aberrations (HOAs) was significantly increased (P = 0.041). RMS of spherical aberration (Z [4, 0]) showed no significant change after surgery (P = 0.972).

Conclusion:

Considering the acceptable residual refractive error, low rate of hyperopic overcorrection, acceptable uncorrected visual acuity, and low risk of postoperative corneal haze, PRK using the APT nomogram with iris registration and mitomycin-C use is a safe and effective modality for treatment of moderate to high astigmatism.