ACH is a severe complication caused by disruption and local detachment of the DM, secondary to increasing corneal ectasia in conditions such as keratoconus.13,14 Due to its elasticity, DM retracts or coils when it breaks under tension. The aqueous humor flows into the corneal stroma, causing severe corneal edema and opacity.14,15 The conventional therapies for ACH consist of non-surgical treatments, such as wearing rigid gas-permeable contact lenses (RGPCL), compressive bandaging,16,17 and surgical treatments such as injection of inert gas (C3F8 or SF6) into the anterior chamber, corneal cross-linking, epikeratophakia or lamellar keratoplasty.1,18,19 However, continued RGPCL wear will damage the corneal epithelium, not well tolerated, and is usually associated with poor long-term efficacy and high recurrence rates in patients with advanced keratoconus.20 The severe corneal edema caused by large breaks in DM also limits the likelihood of a complete and successful DALK, which is now the preferred treatment for keratoconus.21
We recognized that repairing the break in DM would allow the corneal edema to subside and the corneal stroma to heal, and could create conditions supportive of subsequent lamellar keratoplasty and even DALK. We therefore proposed this novel and effective procedure which combined epikeratophakia with intracameral air injection and DALK using the same corneal graft. Intracameral air injection is an effective therapy that can shorten the period of corneal edema.22 In the first-stage surgery, the pathological cornea was covered with an allogenic donor graft and an air bubble was inserted into the anterior chamber to push the detached DM back and adjacent to the stroma. This contributed to rapid closure of the DM wound, after which the severe edema of the recipient graft bed subsided within 1–2 days, as confirmed by the AS-OCT examination. Six months later, the DM repair was strengthened by new collagen deposits secreted by the surrounding healthy corneal endothelial cells,23 providing a solid structural foundation for the second-stage DALK surgery in the present study, including manual stromal dissection. In the 6 months of follow-up after DALK, AS-OCT examinations showed corneal (stroma plus DM) thickness and BCVA values comparable to those following DALK in keratoconus patients without ACH.24
To our knowledge, this two-step procedure of epikeratophakia with intracameral air injection and DALK has not been reported previously in the medical literature. Currently, sustainable eye banks remain rare in developing countries, and a shortage of donor corneas is the most common problem faced by the corneal surgeon.25 The novel procedure we have proposed consists of two keratoplasties, but the same donor graft is used for both procedures, which therefore imposes no additional donor burden and technically avoids the need for a fresh donor cornea for penetrating keratoplasty with associated complications such as endothelial rejection and chronic endothelial dysfunction.26,27 In addition, about 2 months after epikeratophakia, the donor graft epithelium had also reepithelized from the limbus of the recipient cornea. Consequently, transplanting the same donor graft in the-second stage DALK surgery also avoided the challenge of regenerating a new corneal epithelial layer, promoting rapid graft healing.28
At 2 months after epikeratophakia, 1 eye of 1 patient in this case series showed a complication in the form of a branch-shaped neovascularization in the superficial recipient corneal stroma bed. In that patient, all corneal neovascularization was removed after thoroughly dissection during the DALK procedure, and the recipient corneal stroma bed remained transparent during subsequent follow-up.
In conclusion, we propose a novel two-stage procedure for treating ACH, which shows rapid absorption of corneal edema and DM healing and minimizes the risk of postoperative endothelial immune rejection.