Use of Bowman layer implantation promising for advanced keratoconus

Take-home message: Results were encouraging from patients in a small study group receiving Bowman layer implantations to treat advanced keratoconus.

By Vanessa Caceres; Reviewed by Jack Parker, MD

Birmingham, AL-The use of Bowman layer implantation may be a way to halt progressive advanced keratoconus, according to Jack Parker, MD.

This alternative treatment for advanced keratoconus could help avoid complications associated with the current treatment options of penetrating keratoplasty (PK) or deep anterior lamellar keratoplasty (DALK), said Dr. Parker, UAB Callahan Eye Hospital, Birmingham, AL.

“Traditionally, the management of keratoconus has consisted of a contact lens fitting as long as possible and then a PK or DALK reluctantly,” he said. “I say reluctantly not because these surgeries don’t work, but because of their frequent complications-such as wound healing difficulties, suture-related problems, progression of disease in the recipient rim, and persistent irregular astigmatism in the graft.”

There is a strong desire by surgeons to treat keratoconus early on to avoid PK or DALK and their related complications, he said, noting that this has spurred the popularity of corneal crosslinking (CXL) and intracorneal ring segments to stabilize the eyes.

“The problem is that eyes with advanced keratoconus-steeper than 60 D or thinner than 350 µm-aren’t candidates for corneal crosslinking or intracorneal ring segments,” Dr. Parker said. Keratoconus often progresses in these eyes with steep or thin corneas, and then patients must undergo PK or DALK.

Testing a theory

To help avoid this, Dr. Parker and a team of Dutch researchers, including Gerrit Melles, MD, PhD, Amsterdam, theorized the idea of implanting an isolated Bowman layer in these patients.

“Bowman layer fragmentation is one of the earliest and most significant changes in keratoconus,” he said. “Perhaps by replacing the Bowman layer, we can mechanically bolster and shore up the cornea, protecting it from further ectactic progression.”

Dr. Parker presented the results from the first 22 eyes of 19 patients with advanced progressive keratoconus. All patients received a Bowman implant delivered into the midstroma, and were followed for an average of 2 years, but some for up to 3 years.

“The goals were to halt ectasia progression, improve vision by flattening the cornea into a more normal anatomy, and avoid the complications associated with PK and DALK,” Dr. Parker said.

Dr. Parker explained what an isolated Bowman layer graft looks like and said that the fellow researchers have previously described stripping it from the anterior stroma.¹

In 90% of patients, the corneas flattened, indicating that ectasia progression had stopped.

“That is the same success rate as corneal crosslinking or intracorneal segments,” he said.

He also described Scheimpflug imaging of a cornea that had flattened by about 8 D.

The average best spectacle-corrected visual acuity improved from 20/400 preoperatively to 20/25 postoperatively and contact lens vision remained unchanged.

“That was a fairly significant advancement for many patients,” he said.

There were two complications in the study group. In two cases, intraocular Descemet membrane perforations inadvertently occurred during the manual dissection of the midstromal pocket. Surgery was aborted in both cases, perforations were allowed to heal, and-in both-Bowman layer implantation was successfully re-attempted at a later date.

“The operation looks to be promising, safe, improves people’s vision, and avoids many of the common complications that are the worst bane of people with DALK and PK,” Dr. Parker concluded.

Reference

1. Lie J, Droutsas K, Ham L, et al. Isolated Bowman layer transplantation to manage persistent subepithelial haze after excimer laser surface ablation. J Cataract Refract Surg. 2010;36:1036-1041.

Jack Parker, MD

E: jack.parker@gmail.com

This article was adapted from Dr. Parker’s presentation at the 2014 meeting of the American Academy of Ophthalmology. Dr. Parker did not indicate any proprietary interest in the subject matter.