Hyperopic Photorefractive Keratectomy With Adjunctive Topical Mitomycin C for Refractive Error After Penetrating Keratoplasty for Keratoconus

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.

Femto-LASIK after Deep Anterior Lamellar Keratoplasty to Correct Residual Astigmatism: A Long-Term Case Series Study

Purpose: To evaluate the long-term outcomes of femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) to correct residual astigmatism after deep anterior lamellar keratoplasty (DALK). Methods: This retrospective case series study included 10 eyes that underwent Femto-LASIK after a DALK. The refractive error, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, thinnest corneal thickness (TCT), and central corneal thickness (CCT) were registered. The postoperative follow-up ranged between 36 and 60 months. Results: All surgeries were uneventful, with no intra- or postoperative complications. The mean UDVA (Snellen scale) rose from 0.13 ± 0.05 to 0.47 ± 0.15 six months after Femto-LASIK (p < 0.001). All cases experienced a significant improvement in UDVA. None of the eyes lost lines of CDVA, and seven eyes (70%) improved the CDVA compared to preoperative values. The refractive cylinder changed from a preoperative value of −3.88 ± 1.00 D to −0.93 ± 0.39 six months after Femto-LASIK (p < 0.0001). In eight eyes (80%), the UDVA and refractive outcomes remained stable at postoperative follow-up visits. In contrast, one eye experienced a refractive regression over the follow-up. TCT and CCT were stable at the different postoperative follow-up visits. Conclusions: Our findings suggest that Femto-LASIK might safely and effectively corrects residual astigmatism after DALK. Despite these encouraging results, further long-term studies, including a larger number of cases, are required to confirm the safety of the procedure. The refractive stability in eyes with prior RK might be lower than for other DALK indications.

Mitomycin-C in corneal surface excimer laser ablation techniques: a report by the American Academy of Ophthalmology

OBJECTIVE

To review the published literature assessing the efficacy and safety of mitomycin-C (MMC) as an adjunctive treatment in corneal surface excimer laser ablation procedures.

METHODS

Literature searches of the PubMed and Cochrane Library databases were last conducted on August 19, 2014, without language or date limitations. The searches retrieved a total of 239 references. Of these, members of the Ophthalmic Technology Assessment Committee Refractive Management/Intervention Panel selected 26 articles that were considered to be of high or medium clinical relevance, and the panel methodologist rated each article according to the strength of evidence. Ten studies were rated as level I evidence, 5 studies were rated as level II evidence, and the remaining 11 studies were rated as level III evidence.

RESULTS

The majority of the articles surveyed in this report support the role of MMC as an adjunctive treatment in surface ablation procedures. When MMC is applied in the appropriate concentration and confined to the central cornea, the incidence of post-surface ablation haze is decreased. Although a minority of studies that evaluated endothelial cell density (ECD) reported an MMC-related decrease in ECD, no clinical adverse outcomes were reported.

CONCLUSIONS

Over the past 15 years, the use of MMC during surgery in surface ablation has become widespread. There is good evidence of the effectiveness of MMC when used intraoperatively as prophylaxis against haze in higher myopic ablations. Although there are reports of decreased endothelial counts after the administration of MMC during surgery, the clinical significance of this finding remains uncertain, because no adverse outcomes were reported with as much as 5 years of follow-up. Optimal dosage, effectiveness as prophylaxis in lower myopic and hyperopic ablations, and long-term safety, particularly in eyes with reduced corneal endothelial cell counts from prior intraocular surgery, have yet to be established.

Mitomycin C: biological effects and use in refractive surgery

PURPOSE

To provide an overview of the safety and efficacy of mitomycin C (MMC) as adjuvant therapy after refractive surgery procedures.

METHODS

Literature review.

RESULTS

Over the past 10 years, MMC has been used by refractive surgeons to prophylactically decrease haze after surface ablation procedures and therapeutically in the treatment of preexisting haze. Development of MMC treatments has had a significant role in the revival of surface ablation techniques. We reviewed the literature regarding mechanism of action of MMC, its role in modulating wound healing after refractive surgery, and its safety and efficacy as adjuvant therapy applied after primary photorefractive keratectomy surgery or after photorefractive keratectomy re-treatment after laser in situ keratomileusis and other corneal surgeries and disorders. The drug is a potent mitotic inhibitor that effectively blocks keratocyte activation, proliferation, and myofibroblast differentiation. Many studies have suggested that MMC is safe and effective in doses used by anterior surface surgeons, although there continue to be concerns regarding long-term safety. After initial depletion of anterior keratocytes, keratocyte density seems to return to normal 6 to 12 months after the use of MMC when corneas are examined with the confocal microscope. Most clinical studies found no difference between preoperative and postoperative corneal endothelial cell densities when MMC 0.02% was applied during refractive surgery, with exposure time of 2 minutes or less.

CONCLUSIONS

After more than 10 years of use, MMC has been found to be effective when used for prevention and treatment of corneal haze. Questions remain regarding optimal treatment parameters and long-term safety.

Photorefractive keratectomy with mitomycin C after penetrating and lamellar keratoplasty

PURPOSE

To assess the safety and efficacy of photorefractive keratectomy with mitomycin C (PRK-MMC) to correct refractive errors after corneal transplantation.

METHODS

This was a prospective and noncomparative study of 36 eyes that underwent PRK-MMC after penetrating (n = 34) or lamellar (n = 2) keratoplasty. After mechanical epithelial removal and photoablation, a sponge with mitomycin C 0.02% was applied to the stromal bed for 1 minute. The uncorrected and best-corrected visual acuities, refraction, and complications were assessed.

RESULTS

The average follow-up was 16.27 ± 8.38 months (range, 6-30.5 months). The spherical equivalent decreased from -3.95 ± 4.11 to -1.07 ± 1.45 diopters (D) postoperatively (P < 0.001). The mean preoperative astigmatism was 4.42 ± 1.69 D (range, 1.00-7.25 D); however, surgical correction was limited to 6.00 D. Vector analysis of astigmatic correction showed an index of success of 55%. At the last follow-up, 41.7% (n = 15) and 61.1% (n = 22) of the eyes were within ±0.50 and ±1.00 D of emmetropia, respectively. Nineteen eyes (52.8%) achieved an uncorrected visual acuity of 20/40 or better. The best-corrected visual acuity remained within 1 line of the preoperative values in 26 cases (72.2%), improved in 8 (22.2%), and decreased in 2 (5.6%). Endothelial cell decompensation was observed in 1 eye (2.8%) 11 months postoperatively, and haze developed in 3 cases (8.3%).

CONCLUSIONS

PRK-MMC may be an option to correct refractive errors after keratoplasty. A low preoperative endothelial cell count and haze may affect the safety outcomes.

Refractive surgery after corneal transplant

PURPOSE OF REVIEW

Ametropia and astigmatism following successful penetrating keratoplasty can seriously impact a patient's quality of vision. Similar limitations can result following anterior lamellar keratoplasty (ALK) and Descemet's stripping endothelial keratoplasty (DSEK). These patients often suffer from aniseikonia and can be intolerant of spectacles and contact lenses. Refractive surgery can correct both ametropia and astigmatism following corneal transplantation and improve a patient's final visual outcome. The same methods used to correct naturally occurring refractive errors are being used with increasing success in patients who have undergone corneal transplants.

RECENT FINDINGS

Many refractive options are available to treat ametropia following penetrating keratoplasty. Incisional keratotomies have been employed to treat high amounts of astigmatism. Photorefractive keratectomy (PRK) and laser in-situ keratomileusis (LASIK) are also used to treat myopia, hyperopia and astigmatism. LASIK has been shown to have an overall better outcome compared to PRK; however, the use of mitomycin-C with PRK has improved results. Phakic and pseudophakic piggyback intraocular lenses are also being used to treat high degrees of ametropia and astigmatism; however, the long-term results are somewhat limited.

SUMMARY

Refractive surgery can improve the final visual outcome of patients who have undergone successful corneal transplantation. Currently available modalities provide many options for patients who are intolerant of spectacles and contact lenses. Continued advances and research will enable surgeons to optimize visual quality in postkeratoplasty patients.

Mitomycin C in corneal refractive surgery

Mitomycin C has played a deciding role in the current revival of excimer laser surface ablation techniques. We review the literature regarding mechanism of action of mitomycin C, histological effects on the cornea, and indications, dose, exposure time, and toxicity of mitomycin C in corneal refractive surgery. Mitomycin C is an alkylating agent with cytotoxic and antiproliferative effects that reduces the myofibroblast repopulation after laser surface ablation and, therefore, reduces the risk of postoperative corneal haze. It is used prophylactically to avoid haze after primary surface ablation and therapeutically to treat pre-existing haze. There is no definite evidence that establishes an exact diopter limit or ablation depth at which to apply prophylactic mitomycin C. It is usually applied at a concentration of 0.2mg/ml (0.02%) for 12 to 120 seconds over the ablated stroma, although some studies suggest that lower concentrations (0.01%, 0.002%) could also be effective in preventing haze when treating low to moderate myopia. This dose of mitomycin C has not been associated with any clinically relevant epithelial corneal toxicity. Its effect on the endothelium is more controversial: two studies report a decrease in endothelial cell density, but the majority of reports suggest that the endothelium is not altered. Regarding mitomycin C's effect on keratocyte population, although animal studies report keratocyte depletion after its use, longer follow-up suggested that the initial keratocyte depletion does not persist over time.

Deep Anterior Lamellar Keratoplasty for Post-LASIK Ectasia

PURPOSE

To describe 2 cases of post-laser in situ keratomileusis (LASIK) ectasia managed with deep anterior lamellar keratoplasty (DALK).

METHODS

Clinical findings, surgical interventions, and outcomes are reported. The surgical technique of DALK is described.

RESULTS

Two patients developed progressive loss of vision after LASIK surgery with enhancement procedure(s). Corneal ectasia was diagnosed on the basis of clinical findings, progressive central corneal thinning on pachymetry, and topographical changes with irregular astigmatism and inferior corneal steepening. Both patients underwent uneventful DALK surgery, in which the anterior 80% of the central corneal stroma was replaced by a donor button and sutured in place. The postoperative recovery was uneventful, except for mild interface haze in 1 case, which resolved within 2 weeks of surgery. However, 1 patient underwent additional surgery, including clear lens extraction with intraocular lens placement, astigmatic keratotomies, and photorefractive keratectomy (PRK) to achieve good unaided visual acuity. At last follow-up, at least 2 years after DALK, both patients were satisfied with their vision. Their uncorrected visual acuity (UCVA) was 20/60+ and 20/40- in their operated eyes, improving to 20/40+ and 20/30- with minimal refractive corrections. The grafts and lamellar interfaces were clear.

CONCLUSIONS

We believe that DALK should be considered as an alternative to penetrating keratoplasty for the surgical management of post-LASIK ectasia.

Surgical Correction of Hyperopia

Surgical attempts to correct hyperopia have yielded varying results over the last 130 years. These techniques include the reshaping of the cornea through incisions, burns, or lamellar cuts with removal of peripheral tissue; the addition of central inlays; laser ablations; and the replacement of the crystalline lens. By examining the success of each surgical technique, the refractive surgeon may be able to make an informed decision on its indications and limitations, based on the specific patient's characteristics. Reporting the outcomes and complications of hyperopic surgery will help refine our approach to the management of an increasingly hyperopic and presbyopic population.

How and when to use mitomycin-C in refractive surgery

PURPOSE OF REVIEW

Mitomycin-C is an antimetabolite that has seen increased use in ophthalmology over the past several decades. From glaucoma surgery to the management of various corneal disorders, mitomycin-C seems to be a viable tool in the management of scar and haze formation.

RECENT FINDINGS

With the constant evolution of refractive surgery, mitomycin-C has come to the forefront as a modulator of corneal wound healing after excimer laser surface ablation.

SUMMARY

This article will describe the various indications, techniques, and current trends of mitomycin-C application in corneal refractive surgery.

Refractive surgery after corneal transplantation

PURPOSE OF REVIEW

Many patients who have undergone corneal transplantation are unable to achieve satisfactory visual acuity with spectacle and contact lens correction alone. For these patients, refractive surgery becomes a viable option to reduce the post-keratoplasty ametropia. With the many recent advances in refractive surgery for naturally occurring refractive error, new possibilities arise for application to this complicated set of patients. This review discusses key recent developments in refractive surgery after corneal transplantation.

RECENT FINDINGS

The biomechanical effects of incisional keratotomy on post-keratoplasty corneas continue to be studied, and these techniques remain a common and simple method of reducing astigmatism. Photorefractive keratectomy, previously problematic for regression and haze formation, is gaining new prominence as early experience with the adjunctive use of mitomycin C has demonstrated good results. Long-term studies with laser in-situ keratomileusis (LASIK) have continued to show good safety and efficacy. Modern developments in cataract surgery appear to have lower incidences of graft rejection and failure. Developments in lens implantation technology continue to offer expanding options for intraocular refractive surgery.

SUMMARY

Although visual rehabilitation after corneal transplantation remains a formidable challenge, developments in refractive surgery for naturally occurring ametropias directly translate into an improved ability to help these most challenging refractive cases. Continued research will bring about improved efficacy while maintaining a high level of safety.