KERATOPLASTY

Corneal transplantation worldwide is shifting from conventional penetrating keratoplasty (PK) to emerging selective lamellar procedures including anterior lamellar keratoplasty (ALK) and endothelial keratoplasty (EK). However, PK will continue to play a major role, especially in developing countries, Donald Tan MBBS, FRCSE, FRCSG, FRCOphth, FAMS told a Cornea Day session at the 2013 American Society of Cataract and Refractive Surgery (ASCRS) annual symposium.

“Major centres around the world are embracing EK and ALK surgery, and lead the way to the future of corneal transplantation. The lamellar revolution holds great promise,” said Dr Tan, medical director of the Singapore National Eye Centre, chairman of the Singapore Eye Research Institute and president of the Asia Cornea Society.

He noted, though, that adoption rates vary significantly by region and country. Differing clinical indications, procedure difficulty, outcomes questions, cost, reimbursement policies and availability of suitable donor tissue all appear to influence selective lamellar keratoplasty adoption.

Dr Tan based his assessment on a comprehensive review of peer-reviewed literature as well as data from national registries, eye banks and major corneal transplant centres around the world. While the data are spotty due to inconsistent reporting, and in some cases ambiguous due to lack of uniform diagnosis definitions, they show a clear trend towards greater reliance on both EK and ALK.

Some of the more complete data come from developed countries, Dr Tan said. “What is really taking the US and other developed countries by storm is endothelial keratoplasty.” In 2011, EK, including Descemet’s stripping automated endothelial keratoplasty (DSAEK), and Descemet’s membrane endothelial keratoplasty (DMEK), already accounted for 40 to 50 per cent of corneal transplants in Europe, the US and Singapore. Data from larger centres in Japan, Russia Saudi Arabia and elsewhere reflected similar adoption trends.

Advantages of EK include better vision with less astigmatism, shorter recovery time, less rejection, potentially longer graft survival and potentially less endothelial cell loss. However, significant challenges exist to global adoption of EK, particularly in developing countries, Dr Tan said. It is still a new procedure, requiring training and simply overcoming inertia. Cost is an issue.

As a result, PK remains the predominant transplant procedure in developing Asian countries, ranging from 96 per cent in the Philippines to 89 per cent in India and 68 per cent in China’s Tongren Prefecture, though procedure volume is growing, Dr Tan noted. “In the industrialised countries we are at about 50 per cent adoption and the developing countries are at a slightly lower aspect of the [adoption] curve.”

Also, developing countries see more endstage severe disease unsuitable for DSAEK, meaning PK is likely to continue playing a larger role, he added.

Overall, ALK adoption lags that of EK, in part because indications for ALK are less common, Dr Tan noted. But while developed countries clearly lead the way in EK adoption, ALK is gaining ground quicker in some developing countries. Nationally, Singapore, Brazil and Italy stand out as mature adopters, with ALK at about 25 per cent of all corneal transplants. Major centres in China and Saudi report similar rates, Dr Tan said. UK, Australia, Hong Kong and India are in the seven per cent to 12 per cent range, while most other countries, including the US, Italy and Germany, are further behind at two per cent to five per cent.

ALK benefits include lower graft rejection rates, a stronger eye after surgery, donor advantage in that high density endothelium is not needed, better graft survival, and good visual results with big-bubble and other procedures that leave minimal stoma behind. Challenges to ALK adoption include difficulty of the procedure, Dr Tan said. The procedure takes longer and there are reimbursement issues that may be limiting uptake in the US.

Dr Tan noted that in Singapore, PK dropped from about 87 per cent of corneal transplants in 2003 to just 27 per cent in 2012, with DSAEK/DMEK growing to 44 per cent and ALK/DALK to 28 per cent. Similar progressions can be observed globally in eye bank data, and he expects the trend towards selective lamellar keratoplasty will continue as procedures mature and practice catches up with the evidence.