1. Big-Bubble Deep Anterior Lamellar Keratoplasty Dissection Plane Hamish D. McKee, MB ChB Luciane C. D. Irion, PhD, FRCPath Fiona M. Carley, FRCOphth Arun K. Brahma, MD, FRCOphth Manchester Royal Eye Hospital, United Kingdom

2. Corneal Transplantation Penetrating Keratoplasty – Femtosecond-assisted Anterior Lamellar Keratoplasty – Deep Anterior Lamellar Keratoplasty (DALK) – Anterior Lamellar Keratoplasty (ALK) – Femtosecond-assisted Endothelial Keratoplasty – Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) – Descemet’s Membrane Endothelial Keratoplasty (DMEK) Keratoprosthesis

3. Descemet’s Membrane 8 week stage in utero endothelial cells secrete DM continuously A = banded DM prior to birth 3 micrometre B = unbanded DM post-birth up to 7 micrometre

4. Stroma 80-85% of structure of cornea Deeper layers more strictly organised than superficial layers Anterior cornea is more rigid Posterior cornea has poor rigidity – During stromal swelling pressure directs against DM – Results in Descemet’s Folds

5. DALK Video Several techniques for anterior lamellar removal big bubble technique (Anwar) – Surgically technically challenging – Best method of ‘baring’ Descemet’s membrane Sugito and Kondo hydrodelamination technique Melles technique of manual dissection Rostron’s direct dissection method

6. Why not do PK for everyone? Less invasive the procedure, the better Avoid removing non-diseased, healthy tissue Remove only the part of the cornea that is dysfunctional Avoid open-sky situations

7. Background Assumed that big-bubble DALK dissection plane is between stroma and Descemet membrane (DM) Anwar M, Teichmann KD. Big-bubble technique to bare Descemet's membrane in anterior lamellar keratoplasty. J Cataract Refract Surg 2002;28:398-403. Study of 3 big-bubble posterior lamellae obtained during conversion to PK showed residual stroma on all 3 Jafarinasab MR, Rahmati-Kamel M, Kanavi MR, et al. Dissection Plane in Deep Anterior Lamellar Keratoplasty Using the Big-Bubble Technique. Cornea 2010 Feb 15.

8. Background 2 types of big bubble seen clinically White-margin big-bubble – As described in original paper Anwar M, Teichmann KD. Big-bubble technique to bare Descemet's membrane in anterior lamellar keratoplasty. J Cataract Refract Surg 2002;28:398-403. Clear-margin big-bubble – Appears like air-bubble in AC but not mobile – Anwar suggested may represent intra-DM cleavage plane (AAO Subspeciality Day November 10, 2007) Edge of mobile air bubble in AC

9. Aims and methods Donor corneas mounted on artificial anterior chamber Big-bubble dissection carried out Type of bubble noted – White-margin – Clear-margin Samples, formalin-fixed paraffin-embedded, evaluated with light microscopy using H&E and PAS stain

10. Results 30 white-margin big-bubbles – All showed residual stroma Mean 7.0 μm (range 2.6 – 17.4) 2 clear-margin big-bubbles – No residual stroma seen on Descemet membrane Unable to determine on light microscopy if plane between DM and stroma or intra-DM Stroma (S), Descemet membrane (D), endothelium (E)

13. Conclusion The big bubble technique does NOT routinely bare DM The white margin seen during big-bubble DALK may indicate an intrastromal cleavage plane True baring of DM may only occur in the less commonly seen clear-margin big-bubble The disregulation of lamellar fibres within the stroma of keratoconus may explain why the big bubble is a surgically difficult procedure with relatively low success It is important to note the type of big-bubble obtained clinically for histological or clinical research on big- bubble DALK