DALK SURGERY

New indications for deep anterior lamellar keratoplasty (DALK) are enlarging the scope of surgeons’ ability to perform corneal transplantations without the risk of rejection, Donald Tan MD told delegates attending the 2nd EuCornea Congress. “DALK surgery can be used to treat a wide variety of corneal, refractive, ocular surface and anterior segment conditions and corneal surgeons today should avail themselves of this option where appropriate,†said Dr Tan, director of the Singapore National Eye Centre and professor of ophthalmology at the National University of Singapore.

He stressed that advances in surgical tools and techniques are fostering an increase in lamellar surgery and a marked reduction in penetrating keratoplasty (PKP) procedures in some institutions who perform high-volume lamellar surgery.

“The trend is towards increased anterior lamellar keratoplasty and endothelial keratoplasty in Singapore. Of all grafts performed at our centre in 2010, 61 per cent were lamellar keratoplasties, with anterior lamellar grafts accounting for 24 per cent and endothelial keratoplasty 36 per cent.†The principal reason for the shift lies in the data for graft rejection, said Dr Tan. In the Singapore corneal transplant study, which looked at 901 PKPs performed from 1991 to 2003, 60 per cent of the graft failures were due to either endothelial rejection or late endothelial decompensation.

By contrast, a significant improvement in graft survival was found for DALK and Descemet’s stripping automated endothelial keratoplasty (DSAEK) outcomes, he said.

Current indications for DSAEK include conditions such as bullous keratopathy, re-grafts and Fuch’s dystrophy, while the main indications for DALK are keratoconus, post-infectious or traumatic stromal scars, post-refractive surgery ectasia or scarring, active infectious keratitis unresponsive to medical treatment, and as an adjunct to ocular surface transplantation.

Looking at some of these indications in more detail, Dr Tan said that a recent study comparing visual outcomes in DALK and PKP for keratoconus showed better outcomes and less complications for DALK procedures. “Endothelial cell loss was reduced in the DALK group and there were no rejections compared to a 35 per cent incidence of rejection episodes in the PKP. DALK patients also experienced less raised IOP, and reduced rates of glaucoma and cataract as well because we are using far less topical steroids for these patients,†he said.

In terms of new and emerging indications for DALK, Dr Tan highlighted scenarios such as therapeutic DALK for infectious keratitis, refractive surgery stromal disasters, DALK combined with ocular surface transplantation, keratoconus with previous hydrops, and anterior lamellar keratoplasty over failed PKPs due to stromal disease.

In a recent case series, eight eyes of eight patients successfully underwent DALK over a previous PKP for a variety of optical, therapeutic, and tectonic indications, where endothelial function from the PKP remained healthy, said Dr Tan.

He added that while DALK is usually contraindicated in cases of previous hydrops because of the risk of Descemet’s membrane rupture at the hydrops scar, improved manual lamellar dissection techniques means that manual DALK is possible for such cases with the possibility of obtaining good vision as an alternative to PKP.

Dr Tan also noted that refractive surgery disasters such as complete flap necrosis, ectasia or infections are also possible indications for treatment using automated lamellar therapeutic keratoplasty (ALTK).

For medically unresponsive infectious keratitis, therapeutic DALK may be considered instead of therapeutic PKP, said Dr Tan, as the procedure yields better overall graft survival.

Dr Tan reiterated that DALK is now rightly seen as a viable alternative to PKP with equivalent or better visual results.