What is DALK?
Deep Anterior Lamellar Keratoplasty. As the name suggests it is a type of keratoplasty or corneal transplantation. There have been traditionally two types of replacement of cornea with a cadaver cornea. Full thickness graft referred to as Penetrating Keratoplasty or PK. The other type less commonly used was Lamellar keratoplasty or LK, This is a partial thickness cornea graft. Learn about the Structure of Cornea.
DALK is hybrid between LK and PK. It goes deep where no LK has ever been before (language sounds like Star Trek, huh). It just stops short of the Descemets’ and endothelial layer.
Indications for the DALK procedure
DALK is indicated when the inner layers of the cornea is healthy but the superior layers have a pathology.
In Keratoconus eye disorder the endothelium works but the collagen layer is weak. Keratoconus eye disease is present in younger people. DALK is a good choice in them. If the cornea has ruptured like in Hydrops than DALK may not be possible.
Corneal Dystrophies and superficial scars not treatable with PTK are good candidates for DALK. Scars may varied etiology like post PRK scars, post traumatic or post infective. In cases of herpetic scars it is recommended to wait six months after the active infection has subsided.
Steps in DALK Surgery
- Preparation of patients Cornea: The thickness of the host cornea is measured. Three fourths of this value is calculated. A cornea trephine is set to this thickness.
- A needle is introduced through the trephined edge till it reaches the descemets membrane. An air bubble is introduced till it spreads uniformly across the cornea.
- Lamellar dissection is done with a crescent knife to remove the trephine superficial cornea.
- An air bubble is introduced into the anterior chamber. The constant presence indicates the endothelium has not been perforated.
- The needle is reintroduced into the remaining cornea over the descemets membrane. A knife slits the remaining stroma of the cornea. This is than excised with corneal scissors.
- The donor cornea graft devoid of the inner layer is placed on the bare descemets membrane and sutured with interrupted and/or continuous stitches.
Advantage of DALK Transplant
- Safer during surgical procedure as the eye is closed system. Therefore iris and other content of the eye cannot come out.
- The endothelium of the patient is preserved. The chances of endothelium rejection are avoided.
- Even after DALK procedure eye is more resistant to trauma.
- Induced astigmatism is less.
Disadvantage of DALK
- It is technically more difficult to perform
- It may be necessary to convert it to PK on the operating table.
- The host donor junction can become hazy affecting the best corrected vision.
DALK is a great procedure if you qualify for it. There is one way to find out. Schedule a consult with Cornea specialist Rajesh Khanna, MD by calling (310) 482 1240.