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Transplantation of Bowman’s layer a promising option for persistent subepithelial haze
Advantages of the procedure include decreased surgical time and rapid visual recovery.
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Bowman’s layer transplantation may become a realistic treatment option in eyes with recurrent or persistent subepithelial haze, according to a group of surgeons who are currently using this technique at the Netherlands Institute for Innovative Ocular Surgery in Rotterdam.
Although its function is not entirely clear, Bowman’s layer is a visible indicator of ongoing stromal-epithelial interactions and plays a crucial role in preserving corneal transparency, Gerrit Melles, MD, said in an interview with Ocular Surgery News.
Bowman’s-related disorders, abnormal epithelial-stromal interactions, are relatively frequent in hereditary corneal dystrophies, in persistent epithelial defects and after laser photoablation. The damage, disruption or destruction of Bowman’s layer may lead to various degrees of corneal opacity and vision loss.
On the other hand, Dr. Melles pointed out, traumatic or iatrogenic corneal abrasions are rarely, if ever, associated with haze formation, because Bowman’s layer is not affected.
“In the presence of the anatomical Bowman’s layer, subepithelial scars induced by epithelial-stromal wound healing response do not occur,” he said.
Getting to the root of the problem
Conventional treatment options for subepithelial haze are not always effective, Dr. Melles said. They are palliative treatments, but they do not get to the root of the problem, which is the lack of a healthy Bowman’s layer.
“For example, when we use mitomycin C to treat anterior stromal haze following excimer surface ablation, we don’t eliminate the most probable cause of haze development, which is the lack of an anatomical Bowman’s layer. In some cases, haze may become so persistent, difficult to manage and nonresponsive to re-epithelialization that eventually a deep anterior lamellar keratoplasty has to be performed to avoid keratectasia and/or to restore an optically clear cornea,” he said.
Dr. Melles worked with Jessica Lie, PhD, a specialist in surgically preparing lamellar transplants, and fellows at the Rotterdam clinic’s eye bank to develop a procedure to separate Bowman’s layer from the underlying stroma, enabling isolated Bowman’s layer transplantation.
Surgical procedure
In a fairly simple surgical procedure, the anterior corneal scar is excised manually or with femtosecond laser, and then the donor Bowman’s layer is placed on the stromal bed without suture fixation. A sclera-supported hard contact lens is then positioned in the eye to prevent graft dislocation by eyelid movements. After the epithelium has closed, the lens is removed or adjusted to improve visual acuity.
Advantages
The procedure is easier to perform and requires less surgical time than PK or deep anterior lamellar keratoplasty. It is also less invasive, and because only a superficial scar is removed, ocular integrity is largely preserved.
Because isolated Bowman’s layer transplantation is a completely extraocular procedure, the risk of intraoperative complications is low. Iatrogenic complications are reduced by the absence of sutures, preventing erosion and wound dehiscence.
Compared with PK and deep anterior lamellar keratoplasty, Bowman’s layer transplantation enables faster visual recovery. Interface scarring is unlikely to occur, and the cornea rapidly regains clarity. Less postoperative care is needed without sutures, and all medications can be quickly tapered.
In addition, because Bowman’s layer does not contain cellular components, there is no immune response, and the risk of rejection is minimized, Dr. Melles said. – by Michela Cimberle
- Gerrit Melles, MD, can be reached at the Netherlands Institute for Innovative Ocular Surgery, Laan Op Zuid 88, 3071 AA Rotterdam, Netherlands; +31-10-297-4444; fax: +31-10-297-4440; e-mail: melles@niios.nl.