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

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

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

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)

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

„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, 2002Parthasarathy A et al., Br J Ophthalmol, 2008

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, 2002Parthasarathy 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

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)

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

Endothelial cell counts revealed a value of 2237 (SD 243/mm2 ) before surgery, compared to 2068 (SD 302/mm2) 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

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