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Evaluation of the Patient and Decision Making in Anterior Lamellar Keratoplasty
Ashiyana Nariani, MD, MPH; Terry Kim, MD; Melissa B. Daluvoy, MD; and Alan N. Carlson, MD
Since the work done by Eduard Zirm in 1905 with the first successful human full-thickness penetrating keratoplasty (PK),1 there have been several surgeons, including von Hippel,2 Paufique and Charles,3 McGhee, Kim, and Wilson,4 and Anwar,5 who have innovated lamellar corneal transplant surgery as a potential alternative to PK for a variety of indications (Table 3-1).5–10
ADVANTAGES
Deep anterior lamellar keratoplasty (DALK) has emerged in recent years as a preferred approach to conserve the host endothelium and to avoid rejection.4 A report by the American Academy of Ophthalmology, in which 11 published studies comparing DALK with PK were analyzed, substantiated that DALK is superior to PK for preservation of endothelial cell density (ECD), avoiding risk of endothelial cell immune graft rejection and has additional theoretic safety advantages. There was no significant difference in best spectacle-corrected visual acuity, spherocylindrical refraction, nor postoperative astigmatism.5–14
Additional advantages of DALK over PK include enhanced structural integrity with less risk of rupture post-trauma,15–20 faster recovery time with earlier visual improvement,21 absence of endothelial graft rejection, increased intraocular stability during surgery,22 reduced risk of choroidal hemorrhage and endophthalmitis, absence of need of donor graft with good endothelial count, better long-term graft survival,23 no late failures, minimal steroid-related complications and easier follow-up.5,24
TABLE 3-1
INDICATIONS FOR AND CONTRAINDICATIONS TO DEEP ANTERIOR LAMELLAR KERATOPLASTY
| INDICATIONS | CONTRAINDICATIONS |
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DISADVANTAGES
Despite the advantages of the DALK procedure, the technical challenges of and additional time required for the procedure prevent some surgeons from attempting it. Some argue that higher-order aberrations and light scatter caused by the surgical interface may be factors limiting post-DALK visual outcomes.26
In order to optimize resource expenditure, it is critical to understand the indications for and contraindications to performing DALK. For those patients where both DALK and PK are viable surgical options, DALK should be attempted as the benefits of attempting the DALK procedure outweigh the risks and is in the best interest of the patient.
INDICATIONS
DALK is the preferred corneal transplant procedure of choice, over PK, for the optical correction of axial corneal diseases with intact DM and healthy corneal endothelium (see Table 3-1).5–10 Indications can be classified into the following categories: ectasia (Figure 3-1), superficial corneal dystrophies (Figure 3-2), corneal degenerations (Figure 3-3) and deposits (Figure 3-4), and superficial corneal scars.11
Figure 3-1. Keratoglobus. (Reprinted with permission from Melissa B. Daluvoy, MD, Duke University Eye Center, Durham, NC.)
Figure 3-2. Lattice corneal dystrophy. (Reprinted with permission from Melissa B. Daluvoy, MD, Duke University Eye Center, Durham, NC.)
Figure 3-3. (A) Salzmann’s nodular degeneration with corresponding (B) slit lamp examination. Reprinted with permission from Melissa B. Daluvoy, MD, Duke University Eye Center, Durham, NC.)
Figure 3.4. Cloudy cornea due to Hurler’s syndrome (Mucopolysaccharidosis Type 1). (A) Preoperative and (B) postoperative after DALK procedure. (Reprinted with permission from Melissa B. Daluvoy, MD, Duke University Eye Center, Durham, NC.)
Special Considerations
Beyond the previously mentioned indications, there are special cases in patients with healthy endothelium where DALK is the definitive treatment of choice. Surgeons not performing DALK should refer to seasoned DALK surgeons the following case scenarios:
- Given the additional benefit of not having to use long-term steroids with the DALK procedure, it should be the procedure of choice particularly for patients who have normal endothelium but have any of the following factors at play:
- Patients who are steroid responders and/or are phakic
- Patients with poor compliance to therapy and follow-ups6
- Patients at a higher risk of complications, such as positive pressure, iris prolapse, choroidal effusion/hemorrhage
- Patients who are steroid responders and/or are phakic
- DALK has the theoretical advantage of less severity in dehisced suture wounds as compared to PK wounds; therefore, it may be preferred over PK in patients who are predisposed to ocular trauma (eg, personnel in the armed forces, those participating in contact sports).
- DALK has advantages of avoiding the intraocular, open-sky segment of the PK procedure, thereby avoiding complications. Patients residing in an area with harsh and severe climate, making them more prone to ocular surface disease due to environmental factors, would also benefit from undergoing a DALK when indicated as the risk of rejection in consequent vascularized corneas with pan-nus would be higher with a PK in place.
- Sutures may be removed earlier following DALK, allowing for potentially quicker refractive stability. This is important for younger patients at risk for amblyopia, as well as patients who are non-verbal or those with intellectual disabilities, such as patients with Down syndrome.
- Additional clinical scenarios where a DALK would be safer than a PK include keratoconus associated with inflammation (ie, vernal keratoconjunctivitis, monocular status, history of repeated graft rejections in the other eye).6,7
Figure 3-5. (A) Corneal cystinosis deposits, extending through all corneal layers on (B) slit lamp examination and (C) anterior segment optical coherence tomography (ASOCT). (Reprinted with permission from Melissa B. Daluvoy, MD, Duke University Eye Center, Durham, NC.)
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