Corneal haze after photorefractive keratectomy (PRK) can be a challenging complication for ophthalmologists to manage. Mild haze is quite common; in 95% of cases, the cornea clears or is left with trace haze. In some patients, however, haze can persist and cause clinically significant visual disturbances.1 Keratocyte overactivation and fibroblast proliferation have been implicated in haze formation and result in reduced corneal transparency and refractive treatment regression.1,2
Conventional treatments for corneal haze include phototherapeutic keratectomy (PTK), application of mitomycin-C (MMC), and use of topical steroids. These modalities are not always effective, however, and although the haze may initially regress, there are patients whose haze continues to recur aggressively despite multiple treatments. Repeat PTK, superficial keratectomy, amniotic membrane, and the use of thiotepa drops have been used, although not always with effect.3 In extreme cases, penetrating keratoplasty (PKP) has been reported.
Superficial anterior lamellar keratoplasty (ALK) has previously been reported as a technique for treating anterior corneal pathology. We present here a case that demonstrates a similar application of superficial ALK in the treatment of recalcitrant post-PRK haze resistant to a breadth of other treatments.
A 36-year-old man presented to our clinic in 2007 with a history of corneal ectasia secondary to hyperopic laser in situ keratomileusis. He had corneal crosslinking and intrastromal corneal ring segment (Intacs, Addition Technology, Inc.) insertion but continued to have significant aberrations. Penetrating keratoplasty assisted by the use of a femtosecond laser (IntraLase, Johnson & Johnson Vision) was performed. Two-and-a-half years postoperatively, the patient had wavefront PRK with MMC treatment for a refraction of −3.50 +1.25 × 68. Postoperatively, he had a persistent epithelial defect for several months; when the defect resolved, an area of subepithelial haze was revealed.
The patient was treated with PTK and MMC 3 times between 2011 and 2012 in addition to postoperative steroids and thiotepa drops. The haze lessened but never fully resolved after any of the PTK sessions and always worsened in severity within several months of surgery. Even when visual acuity was good, the patient reported that his vision was hazy. A superficial keratectomy was performed in late 2013; however, significant haze recurred and the postoperative corrected distance visual acuity was limited to 20/80 at 8 months. Two more rounds of PTK with MMC were performed during the subsequent 2 years. The haze recurred, and in 2016 PTK and MMC were used in conjunction with topography-guided ablation treatment. The haze recurred once more, and in 2017 PTK and MMC were combined with a superficial keratectomy and amniotic membrane placement. Five months postoperatively, there was dense haze and surface irregularity of the cornea and the uncorrected distance visual acuity was 20/80.
In March 2018, femtosecond laser–assisted superficial ALK was performed. The donor cornea was trephinated with the femtosecond laser; the parameters were a 7.5 mm radius, 130 μm thickness, and 45-degree flap hinge. The patient's native cornea was trephinated with the femtosecond laser; the parameters were 7.5 mm, 150 μm depth, and 45-degree hinge. The flap mode was used in both procedures; thus, a hinge remained because the therapeutic mode did not allow a total lamellar cut. The hinges of the donor cornea and recipient cornea were then amputated manually with scissors. The superficial anterior lamellar donor was placed on the recipient bed and flattened. Eight sutures were placed.
Six months postoperatively, there were no signs of significant haze in the cornea and the patient's corrected distance visual acuity was 20/30.
Superficial ALK is a new strategy for treating anterior corneal opacities. Case series4,5 have reported the effective use of femtosecond laser–assisted sutureless ALK for treatment of anterior corneal scarring secondary to infectious keratitis. Case reports describe the use of microkeratome-assisted superficial ALK to manage an opacity related to laser in situ keratomileusis flap dehiscence and to treat Reis-Bücklers corneal dystrophy.6,7
To our knowledge, this is the first reported case of femtosecond laser–assisted superficial ALK for the treatment of PRK-related haze. Our patient's haze was likely related to multiple factors, notably a nonhealing epithelial defect and history of ocular surgeries.8 Although the haze receded sporadically over several months, it was largely resistant to and recurred after 8 PTK treatments with MMC in addition to adjunctive use of superficial keratectomies and amniotic membrane placement.
Superficial ALK is an optimal treatment in cases in which the pathology is not amenable to superficial treatments such as PTK or superficial keratectomy but is not deep enough to necessitate deep ALK or PKP. Superficial ALK is much less invasive than deep ALK or PKP. In addition, the healing time is shorter and there is less induced astigmatism and fewer potential complications.
Our technique is one of several described in the literature. Use of the microkeratome and the femtosecond laser has been reported. Before the femtosecond laser–assisted superficial lamellar keratectomy, Rasheed and Rabinowitz9 described using a microkeratome to create a free cap; the cornea was allowed to heal without transplantation of tissue. Yoo et al.4 were the first to document use of the femtosecond laser for superficial ALK and touted the benefits of greater depth customizability and a more precise graft–host junction fit compared with the microkeratome. We opted to use sutures in this case; however, the technique has been performed without sutures because of the precision of the laser technology.
In summary, femtosecond laser–assisted superficial ALK might hold promise for managing difficult-to-treat post-PRK corneal haze. In cases recalcitrant to conventional treatments, this technique should be explored as an option.
None of the authors has a financial or proprietary interest in any material or method mentioned.
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