Development of Selective Lamellar Keratoplasty within an Asian Corneal Transplant Program: The Singapore Corneal Transplant Study (An American Ophthalmological Society Thesis)

Abstract

Purpose: To evaluate outcomes of anterior lamellar keratoplasty (ALK) and endothelial keratoplasty (EK) within the Singapore Corneal Transplant Study (SCTS), with the hypothesis that both ALK and EK are able to provide equivalent or improved clinical outcomes, compared to penetrating keratoplasty (PK), and to determine changing trends globally with other international databases.

Methods: Clinical data on all transplants performed was derived from our SCTS database, a prospective national keratoplasty registry, and clinical outcomes (graft survival, endothelial cell loss, complications, visual acuity) were compared between PK, ALK, and EK. Global trends on indications and forms of keratoplasty performed in 2011/2012 were obtained from national keratoplasty or eye banking registries, corneal/ophthalmological societies, national eye banks, and national ophthalmic institutions.

Results: Global rates of EK surgery vary widely, from 52% (Sweden) to 0% (South Africa), with higher adoption by industrialized countries. ALK adoption rates similarly vary from 28.7% (China) to 1.0% (Philippines). SCTS data show high adoption rates in Singapore: EK 44% and ALK 28%. Our surgical modifications to big-bubble deep anterior lamellar keratoplasty (DALK) surgery resulted in visual outcomes matching PK, and a low conversion to PK of 2.1%, whereas our evolving approaches to donor insertion in Descemet's stripping automated endothelial keratoplasty (DSAEK) show significant reduction in 1-year postoperative endothelial cell loss rates from 60% (folding), to 22% to 30% (Sheets Glide), to 15% (EndoGlide inserter).

Conclusion: Improvements in various forms of ALK and EK surgery can lead to better visual outcomes, longer graft survival, and reduced complications, as compared to PK. Global trends suggest adoption of these procedures at different rates.

FIGURE 1

Evolution of the type of keratoplasty performed at the Singapore National Eye Centre from 1991 to 2012. DALK, deep anterior lamellar keratoplasty; DMEK, Descemet’s membrane endothelial keratoplasty; DSAEK, Descemet’s stripping automated endothelial keratoplasty; PK, penetrating keratoplasty.

FIGURE 2

Therapeutic deep anterior lamellar keratoplasty for active, unresponsive infectious keratitis. Left, Severe contact lens–related Pseudomonas aeruginosa keratitis presenting as a corneal abscess with hypopyon not responding to conservative management. Right, Postoperative appearance after therapeutic big-bubble deep anterior lamellar keratoplasty. After 8 years, graft was clear and there was no disease recurrence.

FIGURE 3

Tectonic peripheral crescenteric anterior lamellar keratoplasty: Mooren’s ulcer with repeated peripheral corneal melting despite long-term systemic immunosuppression, multiple peripheral crescenteric tectonic anterior lamellar patch grafts.

FIGURE 4

Tectonic deep anterior lamellar keratoplasty for small corneal perforations. Left, Leaking descemetocele following repeated corneal melting related to severe blepharokeratitis. Right, Postoperative appearance after tectonic manual, layer-by-layer deep anterior lamellar keratoplasty; visual acuity was 20/30.

FIGURE 5

Combined ocular surface transplantation with deep anterior lamellar keratoplasty for Stevens-Johnson syndrome. Left, Preoperative appearance. Right, Postoperative appearance after cultured oral mucosal epithelial transplantation combined with deep anterior lamellar keratoplasty.

FIGURE 6

Global trends on indications for corneal transplantation in 2011/2012.

FIGURE 7

Global trends on types of keratoplasty performed in 2011/2012. EK, endothelial keratoplasty; LK, anterior lamellar keratoplasty; PK, penetrating keratoplasty.

FIGURE 8

Indications for keratoplasty performed in the Singapore Corneal Transplant Study. ALK, anterior lamellar keratoplasty; DSAEK, Descemet’s stripping automated endothelial keratoplasty; PK, penetrating keratoplasty.

FIGURE 9

Singapore Corneal Transplant Study. Overall graft survival rates for all diagnoses from 2000 to 2011. Survival rates for penetrating keratoplasty (PK), deep anterior lamellar keratoplasty (dALK), and endothelial keratoplasty (EK) are compared.

FIGURE 10

Singapore Corneal Transplant Study. Kaplan-Meier survival curve comparing penetrating keratoplasty (PK) and Descemet’s stripping automated endothelial keratoplasty (EK) performed for pseudophakic bullous keratoplasty (PBK).

FIGURE 11

Singapore Corneal Transplant Study. Kaplan-Meier survival curve comparing penetrating keratoplasty (PK) and Descemet’s stripping automated endothelial keratoplasty (EK) performed for Fuchs’ endothelial dystrophy (FED).

FIGURE 12

Singapore Corneal Transplant Study. Kaplan-Meier survival curve comparing penetrating keratoplasty (PK) and Descemet’s stripping automated endothelial keratoplasty (EK) performed for pseudophakic bullous keratoplasty (PBK) after exclusion of grafts with high risk factors.

FIGURE 13

Singapore Corneal Transplant Study. Kaplan-Meier survival curve comparing penetrating keratoplasty (PK) and Descemet’s stripping automated endothelial keratoplasty (EK) performed for Fuchs’ endothelial dystrophy (FED) after exclusion of grafts with high risk factors.

FIGURE 14

Major complications reported in the Singapore Corneal Transplant Study. ALK, anterior lamellar keratoplasty; DSAEK, Descemet’s stripping automated endothelial keratoplasty; HSV, herpes simplex virus; IOP, intraocular pressure; PK, penetrating keratoplasty.

FIGURE 15

Review of published endothelial cell loss rates following Descemet’s stripping automated endothelial keratoplasty using various donor insertion devices. NCI, Neusidl corneal inserter.

FIGURE 16

Comparison of 3-year Kaplan-Meier survival curve following Sheets Glide Descemet’s stripping automated endothelial keratoplasty (DSAEK) vs penetrating keratoplasty (PK) reported in the Singapore Corneal Transplant Study.