Lamellar keratoplasty (LK) is a surgical procedure where healthy corneal tissue from a deceased individual is grafted into the eye of a patient with diseased corneal tissue. Keratoplasty involves partial or full-thickness corneal transplantation. Two procedures are used in keratoplasty; penetrating keratoplasty (PK) and LK. PK consists of replacing the full thickness of the recipient's cornea while LK replaces the partial thickness or parts of the cornea.
LK is divided into anterior lamellar keratoplasty (ALK) and posterior lamellar keratoplasty (PLK). ALK includes superficial anterior lamellar keratoplasty (SALK) and deep anterior lamellar keratoplasty (DALK).
ALK replaces the epithelium, Bowman’s layer, and stroma while sparing the endothelium and Descemet’s membrane. It is an option in patients who have a healthy endothelium. ALK is a useful procedure for patients who have undergone trauma or keratitis, leading to an anterior stromal scar. Patients with epithelial and stromal dystrophies, spheroidal degeneration, Salzman nodular degeneration, keratoconus, complications following refractive surgery, etc., can benefit from ALK.
PLK, also known as endothelial keratoplasty (EK), replaces the Descemet’s membrane and includes Descemet’s stripping endothelial keratoplasty (DSEK), deep lamellar endothelial keratoplasty (DLEK), Descemet’s stripping automated endothelial keratoplasty (DSAEK), and Descemet’s membrane endothelial keratoplasty (DMEK).
In PLK, the diseased endothelium is removed and replaced with the donor endothelium. Patients with endothelial diseases, Fuchs' endothelial dystrophy, pseudophakic bullous keratopathy, aphakic bullous keratopathy, and iridocorneal endothelial syndrome, can undergo PLK. Other conditions necessitating PLK include glaucoma filtration surgeries, post-PK endothelial graft rejection, etc.
Before the Procedure
The cornea is harvested as early as possible, at least six to 12 hours after the donor's death. The harvested tissue is stored under sterile conditions. Corneas from children two years and under are not considered because of high rejection chances as well as surgical and refractive issues. The medical history and blood screening of the donor is done. A microscopic examination of the donated cornea, which includes an endothelial cell count, is also undertaken.
The ophthalmologist takes the patient through what to expect, which includes the benefits and risks of the procedure. The patient’s medical history is taken, as well as a clinical and ophthalmic evaluation.
LK is performed depending on the part to be replaced.
- SALK is only used when 30-50% of the cornea is affected and replaced with a similar amount of tissue.
The surgeon uses a direct dissection of 60-80% of partial-thickness trephination. Next is corneal dissection with crescent, placement of donor tissue, and suturing.
- Generally, ALK makes use of various techniques.
The Melles technique uses closed dissection which has recorded better visual outcomes.
The Anwar significant bubble technique creates a big bubble to detach the deep stromal layers from the Descemet's membrane.
The viscoelastic dissection technique uses a bubble to separate the deeper stromal layer from the Descemet’s membrane.
Hydro Delamination technique combines a partial trephination and a lamellar keratectomy.
Microkeratome technique makes surgery easier and results in less interface scarring and irregular astigmatism
- In PLK, DLEK uses small incisions of 5 mm.
DSAEK involves stripping off the Descemet’s membrane to prepare the bed, and 4-5 mm limbal or corneoscleral incisions are made to insert the donor tissue with forceps.
DMEK involves the transplantation of isolated donor endothelium and Descemet's membrane.
Risks & Complications
Intraoperatively, ALK may result in micro-perforation where the eye suddenly becomes soft, and fluid or air goes into the interface. It may also lead to pupillary block glaucoma due to the air bubbles left in the anterior chamber. Bleeding and other interface debris like fibers may result.
After surgery, the following complications may arise:
- Graft dislocation
- Primary graft failure
- Graft vascularization
- Graft melting or failure
- Higher endothelial cell loss rates
- Fixed dilated pupil (severe but rare)
- Interface haze limiting 20/20 vision
- Early postoperative intraocular pressure
- Epithelial, subepithelial, or stromal rejection
- Endophthalmitis (inflammation due to infection)
- Persistent epithelial defects due to persistence of tight or loose sutures
- Double anterior chamber caused by entrapped visco or micro-perforation
- Interface abnormalities such as thickness irregularities, folds and wrinkles, incomplete removal of viscoelastic
Aftercare & Recovery
The bandage is opened after 24 hours. The patient receives steroid eye drops every two hours in the first week following surgery. The dose changes to every four hours in the next two weeks, then four times daily from week three to 12, and eventually twice a day up to six months. The medication helps to relieve symptoms such as swelling, redness, and itching. An antibiotic is prescribed, which is instilled in the eye four times daily for two weeks. Topical lubricants are also used monthly for three months and every three months after that. Follow up takes up to 12 months.
With ALK, there is no risk of endothelial graft rejection and there is a rapid functional recovery of vision. It also registers low astigmatism with excellent best-corrected visual acuity. There is also a chance for penetrating keratoplasty to be performed in case of a recurrence or a perforated Descemet’s membrane postoperatively. ALK is primarily an extraocular technique where the host endothelium is preserved; therefore, it has very low rejection risks, wound leaks, or a flat anterior chamber.
PLK has registered a tectonically stable globe, fewer immunological rejections, and no suture-related complications. It preserves the typical corneal topography, thus allowing for faster visual recovery. Procedures like DMEK have a shorter recovery period and less incidence of graft dislocation.