Complete Guide to Endothelial Keratoplasty: Techniques, Outcomes, and Advances

Endothelial keratoplasty (EK) has emerged as the preferred surgical treatment for patients with endothelial dysfunction, revolutionizing the field of corneal transplantation. Unlike traditional penetrating keratoplasty (PK), EK specifically targets the diseased endothelium while preserving the majority of the patient's cornea. This procedure, characterized by its minimally invasive approach, has gained popularity due to improved visual outcomes, faster recovery times, and reduced complications. In this comprehensive guide, we will delve into the intricacies of endothelial keratoplasty, covering indications, preoperative evaluation, contraindications, surgical techniques, postoperative care, potential complications, various EK techniques, prognosis, alternative options, costs, and recent advances.

Indications for Endothelial Keratoplasty

Endothelial keratoplasty is indicated in patients with corneal endothelial dysfunction that leads to corneal edema, compromised vision, or bullous keratopathy. The most common conditions necessitating EK include:

• Fuchs' Endothelial Dystrophy: A genetic disorder characterized by progressive endothelial cell loss, leading to corneal edema and vision impairment.
• Pseudophakic Bullous Keratopathy (PBK): Corneal edema resulting from endothelial damage, typically following cataract surgery.
• Iridocorneal Endothelial Syndrome (ICE): A group of disorders where abnormal endothelial cells spread across the cornea, leading to corneal edema and glaucoma.
• Failed Penetrating Keratoplasty: Patients with failed PK may undergo EK to restore corneal clarity.
• Congenital Hereditary Endothelial Dystrophy (CHED): A rare condition in which the corneal endothelium fails to function correctly, leading to early-onset corneal edema.

Preoperative Evaluation

A thorough preoperative evaluation is essential for the success of endothelial keratoplasty. The evaluation should include:

• Comprehensive Ophthalmic Examination: This includes visual acuity testing, slit-lamp examination, corneal topography, and pachymetry to assess corneal thickness and detect other ocular conditions.
• Endothelial Cell Count: Specular microscopy is used to measure the density of endothelial cells and assess the health of the remaining endothelium.
• Optical Coherence Tomography (OCT): Anterior segment OCT provides detailed imaging of the cornea, helping to assess the corneal thickness, Descemet’s membrane, and anterior chamber depth.
• Assessment of Ocular Surface: The ocular surface should be examined for any signs of dry eye, blepharitis, or other conditions that could affect the surgical outcome.
• Medical History: A review of the patient’s medical history is crucial, particularly in identifying systemic conditions like diabetes, which may impact healing.
• Patient Counseling: Patients should be educated about the procedure, expected outcomes, potential risks, and the importance of postoperative care and follow-up.

Contraindications

While endothelial keratoplasty is highly effective, certain conditions may contraindicate the procedure:

• Significant Corneal Scarring: Patients with extensive anterior stromal scarring or opacification may not benefit from EK, as the visual axis remains compromised.
• Active Ocular Infection: Any active infection, including keratitis or uveitis, must be treated and resolved before considering EK.
• Uncontrolled Glaucoma: Severe glaucoma with optic nerve damage may preclude EK, as elevated intraocular pressure can compromise graft survival.
• Extensive Peripheral Anterior Synechiae (PAS): In cases where PAS involves significant portions of the cornea, the procedure may be technically challenging and less effective.
• Poor General Health: Patients with systemic conditions that impair healing or increase surgical risks should be carefully evaluated before proceeding with EK.

Surgical Techniques and Steps

Endothelial keratoplasty encompasses several techniques, each with its unique approach and indications. The most commonly performed EK procedures include Descemet's Stripping Endothelial Keratoplasty (DSEK), Descemet's Membrane Endothelial Keratoplasty (DMEK), and Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK). Below, we outline the general steps for these procedures.

Descemet's Stripping Endothelial Keratoplasty (DSEK)

1. Preparation of the Donor Tissue: The donor cornea is prepared by manually or mechanically stripping the Descemet's membrane and a thin layer of posterior stroma.
2. Stripping the Host Descemet's Membrane: Through a small incision, the surgeon removes the patient's diseased Descemet's membrane and endothelium using specialized instruments.
3. Insertion of the Donor Graft: The prepared donor tissue is folded and inserted into the anterior chamber through the incision.
4. Unfolding and Positioning the Graft: The graft is unfolded within the anterior chamber using air or balanced salt solution. Once positioned correctly, it is centered over the posterior cornea.
5. Air Bubble Injection: An air bubble is injected into the anterior chamber to press the graft against the recipient's cornea, ensuring proper adhesion.
6. Postoperative Care: The patient is instructed to maintain a supine position to facilitate graft adherence.

Descemet's Membrane Endothelial Keratoplasty (DMEK)

DMEK is a more refined and challenging technique that involves transplanting only the Descemet's membrane and endothelium.

1. Preparation of the Donor Tissue: The donor Descemet's membrane and endothelium are carefully stripped from the stroma.
2. Stripping the Host Descemet's Membrane: Similar to DSEK, the patient's Descemet's membrane is removed.
3. Insertion of the Donor Graft: The ultra-thin donor tissue is rolled into a scroll and inserted into the anterior chamber.
4. Unfolding and Positioning the Graft: The surgeon carefully unfolds the scroll and centers it over the host cornea using gentle manipulation.
5. Air Bubble Injection: An air bubble is injected to adhere the graft to the host cornea.
6. Postoperative Care: As with DSEK, the patient must remain supine to ensure graft adherence.

Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK)

DSAEK is a variant of DSEK that uses an automated microkeratome to prepare the donor graft.

1. Donor Tissue Preparation: An automated microkeratome is used to create a uniform, thin graft.
2. Stripping the Host Descemet's Membrane: The diseased Descemet's membrane is removed using the same technique as in DSEK.
3. Graft Insertion and Positioning: The donor tissue is folded and inserted into the anterior chamber, then unfolded and centered.
4. Air Bubble Injection: An air bubble is injected to secure the graft in place.
5. Postoperative Care: Supine positioning is required to maintain graft adherence.

Postoperative Care

Proper postoperative care is critical for the success of endothelial keratoplasty. Patients should be closely monitored for graft adherence, intraocular pressure, and signs of rejection.

• Medications: Postoperative medications typically include corticosteroid eye drops to reduce inflammation and prevent rejection, as well as antibiotics to prevent infection.
• Positioning: Patients are advised to remain in a supine position for the first 24-48 hours to ensure the graft remains in place.
• Follow-Up Visits: Regular follow-up visits are essential to monitor graft adherence, endothelial cell density, and overall corneal clarity.
• Management of Complications: Early detection and management of complications such as graft detachment or rejection are crucial to preserving graft function.

Potential Complications

While endothelial keratoplasty is generally safe, complications can occur. These may include:

• Graft Detachment: The most common complication, where the donor tissue fails to adhere to the host cornea. This may require re-bubbling or repeat surgery.
• Primary Graft Failure: Occurs when the graft fails to function correctly from the outset, often requiring repeat keratoplasty.
• Graft Rejection: Characterized by endothelial cell loss, corneal edema, and immune response. Early intervention with topical steroids can often reverse rejection.
• Increased Intraocular Pressure: Steroid-induced glaucoma or graft-related angle closure may lead to elevated intraocular pressure, requiring medical or surgical intervention.
• Infectious Keratitis: Though rare, postoperative infections can compromise graft survival and require prompt treatment.

Different Techniques in Endothelial Keratoplasty

Several variations of endothelial keratoplasty have been developed, each with distinct advantages and challenges:

• DSEK/DSAEK: These techniques involve transplanting both Descemet's membrane and a thin layer of posterior stroma, offering greater ease of handling but slightly thicker grafts compared to DMEK.
• DMEK: Considered the gold standard for endothelial keratoplasty, DMEK offers superior visual outcomes due to the transplantation of only Descemet's membrane and endothelium. However, the procedure is technically demanding.
• Pre-Descemet's Endothelial Keratoplasty (PDEK): A newer technique that involves transplanting Descemet's membrane, endothelium, and a thin layer of pre-Descemet's tissue. PDEK may offer advantages in graft stability and handling.

Prognosis and Outcome

The prognosis for patients undergoing endothelial keratoplasty is generally excellent, with most patients achieving significant improvement in vision. The visual outcomes are influenced by factors such as preoperative corneal clarity, graft thickness, and the presence of other ocular conditions.

• Visual Recovery: Patients typically experience rapid visual recovery, often within weeks to a few months postoperatively, compared to the longer recovery times associated with PK.
• Graft Survival: Long-term graft survival rates for EK are favorable, with many grafts remaining clear and functional for over a decade.
• Rejection Rates: The rejection rates for EK are lower than for PK, particularly in DMEK, where the transplanted tissue is minimal, reducing the antigenic load.

Alternative Options

For patients who may not be ideal candidates for endothelial keratoplasty, alternative treatments include:

• Penetrating Keratoplasty (PK): The traditional full-thickness corneal transplant may be considered in cases of severe corneal scarring or when EK is not feasible.
• Keratoprosthesis: For patients with multiple graft failures or severe ocular surface disease, an artificial cornea (keratoprosthesis) may be an option.
• Descemetorhexis Without Endothelial Keratoplasty (DWEK): A newer approach for treating Fuchs' dystrophy, where the Descemet's membrane is removed without grafting, allowing the patient’s peripheral endothelial cells to repopulate the central cornea.

Average Cost

The cost of endothelial keratoplasty varies widely depending on geographical location, the surgeon's expertise, and the specific technique used. On average, the cost may range from $5,000 to $15,000, including the surgical fee, donor tissue, anesthesia, and postoperative care. In some countries, costs may be higher due to the availability of advanced technologies and the need for specialized training.

Recent Advances in Endothelial Keratoplasty

Recent advances in endothelial keratoplasty have focused on improving surgical techniques, graft preparation, and patient outcomes:

• Preloaded Grafts: Preloading of donor tissue by eye banks allows for better standardization of grafts, reduces tissue handling, and shortens surgical time.
• Tissue Engineering: Research into tissue-engineered endothelial cells and Descemet's membranes may pave the way for synthetic or lab-grown grafts, potentially reducing dependence on donor tissue.
• Minimally Invasive Techniques: Advances in micro-incision surgery and the use of femtosecond lasers have improved the precision of graft preparation and insertion.
• Enhanced Imaging: Innovations in imaging technologies such as intraoperative OCT have provided surgeons with real-time visualization, enhancing surgical accuracy and outcomes.

Conclusion

Endothelial keratoplasty represents a significant advancement in corneal transplantation, offering numerous benefits over traditional methods. With its targeted approach, minimally invasive techniques, and excellent visual outcomes, EK has become the procedure of choice for treating endothelial dysfunction. As technology and surgical techniques continue to evolve, the future of endothelial keratoplasty looks promising, with ongoing research focused on improving patient outcomes, reducing complications, and expanding the indications for this remarkable procedure.