Penetrating Keratoplasty, often called PK, is the traditional corneal transplant method in which the entire thickness of the cornea is removed and replaced with a donor graft. This procedure is typically indicated for conditions that affect all corneal layers, such as:

• Advanced keratoconus with significant thinning and distortion
• Extensive scarring from infections, injury, or chemical burns
• Corneal dystrophies that affect multiple layers

PK is generally performed under either local or general anesthesia and can take several hours depending on the complexity of the case. Although this method is highly successful—with thousands of procedures performed each year in the United States—it has some drawbacks. Patients will typically have a longer recovery period, often experiencing blurred vision and light sensitivity for several months until the sutures are removed. There is also a higher risk of transplant rejection, where the immune system may attempt to attack the donor tissue.

Over the years, advances in surgical techniques have allowed our cornea specialists to selectively replace only the diseased portions of the cornea. These selective or partial-thickness transplants offer several benefits compared to traditional full-thickness PK, such as faster healing times and lower risks of rejection. The key types of partial transplants include:

DALK involves replacing the majority of the stroma—the thick middle layer of the cornea—while preserving the patient’s own healthy Descemet’s membrane and endothelial cells. This technique is particularly effective for conditions that exclusively affect the stromal layers, such as:

• Keratoconus, where the cornea becomes cone-shaped due to thinning
• Selective corneal dystrophies affecting the stromal tissue
• Superficial scarring that does not impact the innermost layers

Because the patient’s own endothelium remains intact, DALK carries a lower risk of rejection. In addition, the overall healing process is quicker and the need for long-term use of steroid eye drops is often reduced. However, DALK is a delicate procedure, and in about 10 to 20% of cases, the separation of the stroma from the Descemet’s membrane can be challenging, potentially necessitating conversion to a full-thickness PK.

DSAEK is similar in purpose to DMEK, but the donor tissue includes a thin layer of stroma along with the Descemet’s membrane and endothelial cells. This added tissue makes the graft slightly thicker and, in some ways, easier to manipulate during surgery. However, the extra stromal layer may result in a slightly longer recovery period and a higher risk of postoperative astigmatism. In summary:

• Surgical Ease: The extra tissue can simplify graft handling, especially for surgeons early in their experience.
• Visual Outcomes: Results are generally very good, though on average, vision may not be as sharp as after DMEK.
• Rejection Risk: The risk is marginally higher compared to DMEK because of the additional donor stroma.

While DSAEK is more forgiving during surgery, the added stromal layer can sometimes lead to mild astigmatism and slightly longer visual recovery compared to DMEK.