Lamellar keratoplasty is a type of corneal transplant procedure that involves selectively replacing only the diseased layers of the cornea. This approach differs from a full-thickness corneal transplant, known as penetrating keratoplasty (PK), where the entire cornea is replaced with donor tissue. This technique aims to preserve the healthy layers of the recipient’s cornea, which can offer specific advantages.
Understanding Lamellar Keratoplasty and Its Purpose
Lamellar keratoplasty is a surgical method that involves removing only the damaged portion of the corneal tissue and replacing it with a corresponding healthy section from a donor. The cornea is a transparent, dome-shaped structure at the front of the eye, composed of multiple layers, each with a distinct function.
This procedure addresses conditions affecting specific corneal layers, such as scarring from infections or trauma, and certain corneal dystrophies. Examples include Fuchs’ dystrophy, which impacts the innermost layer, and keratoconus, a progressive thinning that causes the cornea to bulge. Preserving healthy corneal layers helps maintain the eye’s structural integrity and can reduce complications associated with full-thickness transplants.
Types of Lamellar Keratoplasty
Lamellar keratoplasty encompasses several techniques, broadly categorized by which corneal layers are treated. Deep Anterior Lamellar Keratoplasty (DALK) is a common type used for diseases affecting the front layers of the cornea, such as the epithelium, Bowman’s layer, and stroma, while preserving the healthy innermost layer called Descemet’s membrane and the endothelium. This technique is particularly useful for conditions like advanced keratoconus or corneal scarring where the endothelium is still functioning well. DALK aims to remove nearly 95% of the corneal thickness, leaving only the thin posterior membrane.
For conditions affecting the posterior layers, specifically the endothelium, endothelial keratoplasty procedures are performed. Descemet’s Stripping Endothelial Keratoplasty (DSEK) or Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) involves replacing the patient’s diseased endothelium and Descemet’s membrane with a thin layer of donor tissue that includes posterior stroma, Descemet’s membrane, and endothelium. This procedure is frequently used for conditions like Fuchs’ dystrophy, which cause endothelial cell loss.
Descemet’s Membrane Endothelial Keratoplasty (DMEK) is a more refined endothelial keratoplasty technique. In DMEK, only the Descemet’s membrane and the endothelium from the donor are transplanted, without additional stromal tissue. This provides a “like for like” replacement, making it the thinnest type of transplant. This procedure results in faster visual recovery and a lower rejection rate compared to other corneal transplantation methods.
The Surgical Process and Recovery
The surgical process for lamellar keratoplasty begins with a detailed pre-surgical assessment, including comprehensive eye examinations and corneal imaging. The procedure is performed under local or general anesthesia. During surgery, precision instruments carefully remove the diseased portion of the recipient’s cornea.
A healthy donor corneal tissue, obtained from a recently deceased individual, is then prepared to match the removed section. The donor tissue is precisely positioned and secured in place, sometimes using fine stitches, or in some advanced techniques, a laser-based attachment. The eye may be patched after surgery, and a protective shield is often recommended for use at night for about a week.
Recovery varies depending on the specific type of lamellar keratoplasty performed. Blurred vision is common for several weeks as the eye adjusts. Patients are prescribed steroid eye drops and other medications to prevent infection and rejection, which must be used as directed.
Strenuous activities, heavy lifting, and rubbing the eye should be avoided during the initial healing period. Regular follow-up visits with the ophthalmologist are scheduled to monitor healing, manage complications, and ensure the transplant’s success. Full visual stabilization can take several months to a year.
Potential Outcomes and Considerations
The long-term outcomes of lamellar keratoplasty procedures include significant visual improvement. For instance, DMEK has shown visual rehabilitation to 20/40 or better in approximately 90% of cases within the first three months. Graft survival rates are favorable, particularly due to the preservation of healthy recipient tissue layers.
While the risk of rejection is lower compared to full-thickness transplants, it remains a consideration, although endothelial rejection is significantly reduced or eliminated in DALK procedures. Other considerations include infection, glaucoma, and the possibility of residual astigmatism or interface haze, which can affect visual quality. Adherence to post-operative instructions, including consistent use of prescribed eye drops and attending follow-up appointments, significantly influences the procedure’s success. The underlying corneal condition also plays a role in the overall prognosis and visual outcome.