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Deep Anterior Lamellar Keratoplasty (DALK)

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Title: Deep anterior lamellar keratoplasty (DALK)

Author (s): Rhett Thomson, MS4, and Mark Mifflin, MD

Photographer: Mark Mifflin, MD, and Ethan Peterson

Date: 8/29/20

Video:

Keywords/Main Subjects: Deep anterior lamellar keratoplasty; DALK; Corneal Transplantation

Overview:

• Utilized for anterior corneal pathology (eg, keratoconus)^1,2
• Procedure involves replacing anterior lamellae while keeping Descemets membrane (DM) and endothelium
• Outcomes are often compared to those of penetrating keratoplasty (PK)^3-5
• Advantages of DALK:
  • Endothelial rejection risk avoided⁶
  • Ideal in young, healthy patients with active immune systems
  • High quality donor tissue not required (helpful in resource poor areas)
• Disadvantages of DALK:
  • Historically, non-smooth contour from residual lamellar dissection resulted in poorer visual outcomes
  • Rupturing DM is a common complication⁷
  • Complications often necessitate conversion to a full PK⁸
• Recent improvements:
  • “Big bubble” technique increases smooth contour leading to better visual outcomes^9,10
  • “Big bubble” technique involves separating anterior lamella from Descemets using air, decreasing the chance of rupturing Descemets
  • Manual intrastromal dissection can be performed as an alternative to “big bubble” technique

 Description of video: Steps of DALK explained¹¹

1. The geographic center of the cornea is marked
2. An appropriately sized vacuum trephine is selected and set to about ⅔ corneal thickness
   1. Cautery of the anterior surface is generally avoided in DALK
      
3. A stainless-steel crescent blade is used to remove about half of the anterior stroma, making later removal of more posterior tissue easier
   
4. The anterior chamber is decompressed slightly
5. Small indicator air bubbles are injected into the anterior chamber
   
6. Create a “big bubble” to separate Descemets membrane and endothelium from the anterior stroma
   
7. As Descemets is pushed deeper, the air bubbles in the anterior chamber are often seen getting moved to the periphery
   
8. Apply dispersive viscoelastic in advance of puncturing the lamella covering the “big bubble”
   
9. Puncture the remaining stroma while avoiding perforation of Descemets
   
10. Following the puncture of the “big bubble”, Descemets will once again move to its more natural anterior position
    1. This allows the air bubbles in the anterior chamber to return from the periphery to the center
       
11. Between Descemets and remaining anterior lamella, apply dispersive OVD (ophthalmic viscosurgical device)
    
12. Cut remaining stroma into four quadrants and manually cut away, often using curved cornea scissors
    
13. Calipers are used to verify bed diameter prior to preparing and punching donor tissue
    
14. Trypan blue is use to stain donor Descemets which is then removed
    
15. Remove Descemets and endothelium from donor tissue
    
16. Trephination of donor cornea
    
17. Place donor graft on host
    1. Donor tissue is typically cut to the same diameter, or smaller if needed to decrease myopia in a keratoconus patient
       
18. Suture graft using standard techniques
    

References:

1. Al-Torbak AA, Al-Motowa S, Al-Assiri Aet al. Deep anterior lamellar keratoplasty for keratoconus. Cornea 2006; 25:408-412.
2. Mohammadpour M, Heidari Z, Hashemi H. Updates on Managements for Keratoconus. Journal of current ophthalmology 2018; 30:110-124.
3. Song Y, Zhang J, Pan Z. Systematic Review and Meta-Analysis of Clinical Outcomes of Penetrating Keratoplasty Versus Deep Anterior Lamellar Keratoplasty for Keratoconus. Experimental and clinical transplantation : official journal of the Middle East Society for Organ Transplantation 2020; 18:417-428.
4. Keane M, Coster D, Ziaei M, Williams K. Deep anterior lamellar keratoplasty versus penetrating keratoplasty for treating keratoconus. The Cochrane database of systematic reviews 2014:Cd009700.
5. Pedrotti E, Passilongo M, Fasolo A, Ficial S, Ferrari S, Marchini G. Refractive outcomes of penetrating keratoplasty and deep anterior lamellar keratoplasty in fellow eyes for keratoconus. International ophthalmology 2017; 37:911-919.
6. Hos D, Matthaei M, Bock Fet al. Immune reactions after modern lamellar (DALK, DSAEK, DMEK) versus conventional penetrating corneal transplantation. Progress in retinal and eye research 2019; 73:100768.
7. Huang OS, Htoon HM, Chan AM, Tan D, Mehta JS. Incidence and Outcomes of Intraoperative Descemet Membrane Perforations During Deep Anterior Lamellar Keratoplasty. American journal of ophthalmology 2019; 199:9-18.
8. Donoso R, Díaz C, Villavicencio P. Comparative study of keratoconus between Anwar’s deep anterior lamellar keratoplasty versus converted penetrating keratoplasty. Archivos de la Sociedad Espanola de Oftalmologia 2015; 90:257-263.
9. DUA HS. Know your Bubbles. Acta ophthalmologica 2016; 94.
10. Dua HS, Faraj LA, Kenawy MBet al. Dynamics of big bubble formation in deep anterior lamellar keratoplasty by the big bubble technique: in vitro studies. Acta ophthalmologica 2018; 96:69-76.
11. Nanavaty MA, Vijjan KS, Yvon C. Deep anterior lamellar keratoplasty: A surgeon’s guide. Journal of current ophthalmology 2018; 30:297-310.

Faculty Approval by: Mark Mifflin, M.D.

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