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Bowman’s layer transplantation may be safer surgery for patients with advanced keratoconus
The surgery helps avoid many of the complications associated with PK and DALK.
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For most eyes with advanced keratoconus, penetrating keratoplasty is a bad option. It permanently weakens the cornea, precipitates cataracts, promotes glaucoma, provides an often uneven and unstable refractive surface, presents the constant risk of allograft reaction and graft rejection, and — perhaps worst of all — produces many unhappy patients, particularly if the surgery was elective and not emergently required.
Nevertheless, PK so far remains the most common surgical treatment worldwide for patients with advanced keratoconus. And while alternatives to conventional PK have emerged, including deep anterior lamellar keratoplasty and new femtosecond technology for creating and shaping the donor and recipient surfaces, for the most part, these innovations have merely mitigated the impact of some of the above problems without actually solving any of them. Meanwhile, ultraviolet corneal cross-linking and intracorneal ring segments have arrived but, presently, are still limited in their application exclusively to patients with mild to moderate stage disease. What has been sorely lacking is a new treatment option for patients with advanced keratoconus that is effective and, at the same time, free from the considerable difficulties that both PK and DALK frequently entail.
Recently, however, Bowman’s layer transplantation has been described for exactly this cohort of patients. The operation consists of implanting an isolated donor Bowman’s layer within the mid-stroma of a recipient keratoconic cornea. The healing response around the graft serves to both flatten the cornea into a more normal anatomic configuration and also to stabilize it against further ectasia. So far for our patients who received this operation, many of them now 4 to 6 years after surgery, the average amount of corneal flattening has been 8 D to 9 D, and 90% have seen their previously progressive disease arrested. Practically all have had comfortable contact lens wear preserved or restored. Moreover, the litany of potential complications has been abolished. This is because Bowman’s layer transplantation involves no surface incisions; no sutures; no cellular/metabolically active tissue so potentially no allograft reaction/graft rejection; no intraocular manipulations because the entire surgery takes place within the recipient cornea; no cataract formation or glaucoma development; and, most of all, vanishingly few unhappy patients.
And while the idea of Bowman’s layer transplantation may be relatively new, the surgery itself employs only old techniques; the manual mid-stromal dissection of a recipient cornea was actually first described as part of a DALK procedure in 1998. In addition, the operation may be considered low risk because either PK or DALK can always be tried later if Bowman’s layer transplantation fails.
Just as endothelial keratoplasty displaced PK as the treatment of choice for endothelial disorders worldwide, increasingly it seems that selective anterior lamellar surgery will do the same for disorders of the anterior cornea, including keratoconus. Smaller, more specific and more peculiar grafts may be the future of corneal transplantation. And if it were your eye, which kind would you choose?
- References:
- Melles GRJ, et al. Br J Ophthalmol. 1999;doi:10.1136/bjo.83.3.327.
- Melles GRJ, et al. Cornea. 1999;18(1):80-86.
- Parker JS, et al. Surv Ophthalmol. 2015;doi:10.1016/j.survophthal.2015.02.004.
- Parker JS, et al. US Ophthalmic Review. 2015;doi:10.17925/usor.2015.8.1.33.
- van Dijk K, et al. JAMA Ophthalmol. 2014;doi:10.1001/jamaophthalmol.2013.5841.
- van Dijk K, et al. Ophthalmology. 2015;doi:10.1016/j.ophtha.2014.12.005.
- For more information:
- Jack S. Parker, MD, a YO member of the OSN Europe Edition Board, can be reached at Parker Cornea, 700 18th St. S #503, Birmingham, AL 35233, USA; email: jack.parker@gmail.com.
Disclosures: The authors report no relevant financial disclosures.