DALK

Indications for DALK

DALK is typically performed in patients with corneal diseases that affect the front layers of the cornea (epithelium and stroma) but have a healthy endothelium. The most common indications for DALK include:

1. Keratoconus:

1. A progressive, non-inflammatory condition where the cornea thins and bulges outward, leading to irregular astigmatism and distorted vision.

2. Corneal Scarring:

2. Scars caused by infections (such as herpes simplex virus or bacterial keratitis), trauma, or previous surgeries that affect vision.

3. Corneal Dystrophies:

3. Hereditary diseases like granular dystrophy or lattice dystrophy, which cause deposits to form in the corneal stroma, affecting transparency.

4. Chemical Injuries:

4. In cases where the outer layers of the cornea are damaged by chemical burns, but the endothelium remains healthy.

5. Post-Infectious Keratitis:

5. After an infection has been treated, if the resulting corneal opacity is limited to the stroma, DALK can be used to restore clarity.

Advantages of DALK

1. Lower Risk of Rejection:

1. Since DALK preserves the patient’s endothelium (the layer most likely to cause immune rejection), the risk of graft rejection is much lower compared to penetrating keratoplasty (PK), which replaces the entire cornea.

2. No Risk of Endothelial Cell Loss:

2. DALK avoids damage to the patient’s own endothelial cells, which are essential for keeping the cornea clear and free of swelling. Preserving the endothelium means that patients are less likely to develop conditions like corneal edema or graft failure over time.

3. Faster Recovery and Fewer Long-Term Complications:

3. DALK patients typically experience fewer long-term complications because their own endothelium continues to function properly. Additionally, visual recovery can be faster and more stable in some cases.

4. Reduced Need for Immunosuppression:

4. Since the endothelium is not replaced, the body is less likely to recognize the graft as foreign, reducing the need for long-term use of steroid eye drops or other immunosuppressive medications.

5. Long-Term Graft Survival:

5. Because the patient’s own endothelium remains in place, the graft can last longer, particularly in younger patients who may need a corneal transplant early in life.

The DALK Procedure

DALK is a technically challenging surgery and involves several key steps:

1. Creating the Corneal Incision:

1. The surgeon begins by making a small incision on the surface of the cornea.

2. Removing the Damaged Stroma:

2. Using specialized tools, the surgeon carefully removes the epithelium and stroma (the outer layers of the cornea) while leaving the patient’s own Descemet’s membrane and endothelium intact.

3. This can be done either by manual dissection or using an air bubble technique (also known as the "Big Bubble" technique), where an air bubble is injected to separate the stroma from the underlying healthy layers.

3. Graft Placement:

3. Once the patient’s damaged corneal layers are removed, a donor graft (which includes the stroma and epithelium) is prepared and placed onto the patient’s cornea. The graft is then secured with fine sutures.

4. Post-Surgery:

4. After the surgery, the patient’s eye is bandaged, and prescription eye drops (antibiotics and steroids) are provided to prevent infection and control inflammation.

Recovery After DALK

1. Visual Recovery:

1. Vision improves gradually after DALK, though it may take several months for the vision to stabilize fully, especially if sutures remain in place for an extended period.

2. Like with penetrating keratoplasty, some patients may experience post-operative astigmatism, which can be managed with glasses, contact lenses, or additional procedures.

2. Sutures:

2. Sutures are usually left in place for 6 to 12 months, depending on how well the eye heals. Removing the sutures at the right time is critical for achieving the best possible vision.

3. Activity Restrictions:

3. Patients are advised to avoid activities that could cause trauma to the eye or increase eye pressure, such as heavy lifting, strenuous exercise, or rubbing the eye.

4. Follow-Up:

4. Regular follow-up appointments are necessary to monitor healing, control inflammation, and ensure the graft remains clear.

Risks and Complications

While DALK is generally safer than penetrating keratoplasty, some risks and potential complications still exist:

1. Incomplete Dissection:

1. One of the most challenging aspects of DALK is preserving the Descemet's membrane and the endothelium. In some cases, the membrane may be accidentally perforated during the surgery, requiring conversion to a full penetrating keratoplasty (PK).

2. Astigmatism:

2. Irregular corneal healing can lead to astigmatism, a common complication after corneal transplantation. It can be corrected with glasses, contact lenses, or additional surgical techniques like suture adjustment or refractive surgery.

3. Graft Failure:

3. Although the risk of rejection is lower with DALK, there is still a small chance of graft failure due to improper healing, infection, or other factors.

4. Infection:

4. Post-operative infections are rare but can occur. This risk is mitigated by using antibiotic eye drops and proper post-operative care.

5. Scarring:

5. In rare cases, scarring can occur at the graft-host junction, affecting the clarity of vision. Scarring may require further surgical intervention.

6. Longer Surgical Time:

6. DALK surgery is typically longer and more technically challenging than penetrating keratoplasty because of the need to precisely dissect the corneal layers.

Success Rates of DALK

DALK has a high success rate in patients with healthy endothelium. Studies have shown that 90-95% of patients achieve significant improvements in vision following the procedure, with fewer long-term complications compared to penetrating keratoplasty. In conditions like keratoconus, the outcomes are particularly favorable, with most patients achieving clear vision without the risk of endothelial rejection.

Comparison with Penetrating Keratoplasty (PK)

• Risk of Rejection: DALK has a lower risk of rejection compared to PK because the patient’s own endothelium is preserved.

• Complications: DALK has fewer long-term complications, such as endothelial cell loss or chronic corneal edema, which can occur after PK.

• Vision: Both surgeries can restore clear vision, though DALK patients may experience fewer complications and more stable vision in the long term.

• Recovery: Recovery from DALK may be somewhat faster, though both procedures require months for full healing.

Conclusion

Deep Anterior Lamellar Keratoplasty (DALK) is an excellent option for patients with corneal diseases like keratoconus or corneal scarring that affect the outer layers of the cornea while sparing the endothelium. The procedure offers a safer alternative to full-thickness corneal transplants (penetrating keratoplasty) by reducing the risk of rejection, preserving the patient's healthy endothelial cells, and providing long-term stability. Although technically challenging, DALK can achieve excellent visual outcomes and significantly improve patients' quality of life with fewer long-term risks.