1. Dept. of Ophthalmology, Friedrich-Alexander University Erlangen-Nuremberg, Erlangen, Germany. Outcome after big-bubble deep anterior lamellar keratoplasty (DALK) for corneal stromal diseases with and without the use of a femtosecond laser S. Riss, B. Bachmann, C. Cursiefen, F.E. Kruse The authors have no financial interest in the subject of this poster

2.  Deep anterior lamellar keratoplasty (DALK) is an alternative to penetrating keratoplasty (PK) in patients with corneal stromal diseases.  The technique involves the replacement of the diseased stroma of the cornea while preserving the recipients Descemet`s membrane and endothelial layer.  Separation of Descemet’s membrane from the posterior stroma can be achieved either by manual preparation or by placing an air bubble between these two layers (big bubble technique).  We want to present the clinical outcome after DALK surgery using the big-bubble-procedure with a modified small-bubble technique.  We want to investigate the use of a femtosecond laser to increase the safety of the procedure. Purpose

3.  54 eyes of 54 patients treated with DALK using the big-bubble technique with successful bubble formation were evaluated.  10 eyes of 10 patients were treated with femtosecond laser-assisted DALK.  Preoperative diagnostics included ultrasound pachymetry, Pentacam, Orbscan, slit-lamp OCT, endothelial cell count and sufficient slit-lamp biomicroscopy.  Indications were keratokonus (n = 49), keratoglobus (n = 1), pellucidal marginal degeneration (n=1) and corneal scars (n = 3).  The main outcome measures of the study included best-corrected visual acuity, astigmatism, endothelial cell count and pachymetry.  Intraoperative and postoperative complications and conversion rate are described in relation to the use of a femtosecond laser (Femtec, 20/10 perfect vision, Heidelberg, Germany). Methods

4. Correct Pachymetry Mapping for Accurate Placement of the Big Bubble  Ultrasound pachymetry is currently viewed as the gold standard in measuring corneal thickness as it has a high degree of reproducibility.  Oculus Pentacam ® is a fast, non-contact method of measuring corneal thickness using a rotating scheimpflug camera, which allows a pachymtery mapping of central and peripherial corneal thickness.  We examined 30 patients and used different pachymetry devices to measure corneal thickness and analyzed the comparibilty to ultrasound pachymetry. Pentacam ® Scheimpflug imaging, (Oculus, Wetzlar, Germany)

5. Rössler C et al., 2010, submitted  Correlation between the ultrasound pachymetry and the Pentacam ® revealed a high significant correlation coefficient of 0.838 (Figure A).  Central corneal thickness measured by Pentacam ® showed the highest comparability to the ultrasonic pachymetry (Figure B). Figure A) Figure B) Correct Pachymetry Mapping for Accurate Placement of the Big Bubble

6. „ Big Bubble“-DALK with modified „Small Bubble“ Technique Air injection into the corneal stromal tissue forming a large air bubble between Descemet`s membrane and the host`s corneal stroma. Exact predescemetal positioning of the needle. Peripherial Trephination at determined depth according to Pentacam pachymetry. modified from Anwar M et al., J Cataract Refract Surg, 2002 Parthasarathy A et al., Br J Ophthalmol, 2008

7. Injecting a small air bubble into the anterior chamber to delineate separation of stroma and Descemet`s membrane. modified from Anwar M et al., J Cataract Refract Surg, 2002 Parthasarathy A et al., Br J Ophthalmol, 2008 After removing of the host`s anterior stroma, the donor graft is sutured into host`s corneal bed. Slit-lamp OCT of a patient on the first day after DALK „ Big Bubble“-DALK with modified „Small Bubble“ Technique

8. Femtosecond Laser-assisted DALK  10 eyes of 10 patients were treated with femtosecond laser-assisted DALK using Femtec (20/10 perfect vision, Heidelberg, Germany).  Indication was keratokonus (n=10) in all cases.  Preoperative pachymtery mapping was performed by ultrasound pachymetry and Pentacam ® for measuring central and peripheriial corneal thickness (Figure A).  Accordintg to Pentacam ® results cut depth was determined at 90% of the thinnest pachymetry value on the trephination circle in all cases (Figure B). Figure A) Figure B)

9.  Best-corrected visual acuity (BCVA) preoperatively was 0.17 (SD 0.14) and 6 months postoperatively 0.45 (0.15) (p=0.001)  Astigmatism could be reduced from 6.13 (SD 3.76) preoperatively to 3.79 (SD 2.48) at 6 months follow-up (p=0.02). Results

10.  Endothelial cell counts revealed a value of 2237 (SD 243/mm 2 ) before surgery, compared to 2068 (SD 302/mm 2 ) 6 months after the procedure (p>0.05). A significant loss of endothelial cells could not be detected.  Complications included delayed wound healing (6/54), early suture loosening (3/54) and delayed descemet re-attachment (5/54), which could be handled using air injection.  Conversion rate to perforating keratoplasty was 30% in eyes with manual dissection and 0% with the use of a femtosecond laser. Results

11.  DALK using the big-bubble-technique is an effective and safe treatment option for corneal stromal diseases.  No perforation of Descemet‘s membrane in our first 10 consecutive femtosecond laser assisted-DALK patients occured.  The safety of the procedure can be improved and the conversion rate can be reduced by using femtosecond laser in connection with advanced pachymetry. Conclusions