Department of Ophthalmology, University Hospital Ayr, Scotland Microkeratome Assisted Superficial Anterior Lamellar Keratoplasty: A Prospective Interventional Case Series Michelle Attzs Sathish Srinivasan Department of Ophthalmology, University Hospital Ayr, Scotland The authors have no financial interests to declare

PURPOSE To report indications, visual and refractive outcomes of patients following microkeratome assisted superficial anterior lamellar keratoplasty (SALK)

METHODS Interventional case series of nine eyes of nine patients, with anterior corneal pathology, who underwent pre operative anterior segment optical coherence tomography (AS-OCT) with either Visante (Carl Zeiss Meditec, Inc, USA) or Cirrus (Carl Zeiss Meditec, Inc, USA) All surgeries were performed by a corneal surgeon (SS) Depth of pathology, thickness of donor lamellar disc used, pre and postoperative uncorrected (UDVA) and corrected distance (CDVA) visual acuities; and complications were evaluated

SURGICAL TECHNIQUE Depending on the depth of pathology, as assessed by AS-OCT, a 200, 250 or 300 micron head microkeratome (Moria, France) was used to remove the pathological anterior lamellar from the recipient cornea The donor cornea was mounted on an artificial anterior chamber (Moria, France) A same sized microkeratome (with freshly disposable blade) was used to prepare the donor anterior lamellar button A donor anterior lamellar button of the desired thickness, with an overall diameter of 9.25mm, was provided The donor anterior lamellar lenticule was secured to the host stromal bed with a combination of eight 10-0 nylon interrupted sutures and fibrin glue A bandage contact lens was positioned on the eye at the end of the procedure

Anterior stromal scar- HSV keratitis 150 0.78 0.48 2 Patient Age Sex Indication for surgery Depth of pathology (microns) Pre op UDVA CDVA Post op Further surgery 1 70 M Anterior stromal scar- HSV keratitis 150 0.78 0.48 2 DALK due to underestimation of depth of pathology by AS OCT 29 160 0.18 - 3 48 Ant/Mid stromal scar- CL related infectious keratitis 144 0.3 0.6 4 46 Lattice dystrophy Interface infectious keratitis and subsequent DALK 5 53 F Anterior stromal scar - CL related infectious keratitis 120 6 40 Meesmann corneal dystrophy U/A 7 80 240 8 44 190 PK due to underestimation of depth of pathology by AS OCT. Subsequent early rejection 9 30 Granular dystrophy

RESULTS Mean age of cohort 49 ± 17 years (range 29 – 80) Average depth of pathology on AS-OCT was 165 ± 39 microns (range 144 – 240 microns) (including patients where AS-OCT could assess depth of pathology) Inaccurate estimation of depth of pathology by AS- OCT with two cases resulted in a further deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) (Patient 1 and 8, respectively) One case developed interface infectious keratitis, and required a subsequent DALK, after removal of the SALK and treatment with high dose antimicrobial treatment (Patient 4) AS-OCT was unable to estimate the depth of pathology in cases of corneal dystrophy

RESULTS Pre operative mean UDVA and CDVA, of all patients who underwent surgery, was 1.16 logMAR and 0.76 logMAR, respectively At 6 months, post operative mean UDVA and CDVA was 1.06 logMAR and 0.68 logMAR, respectively (excluding patients who required further surgery , n=3)

CASE 1 48 year old male with central corneal scar of OD due to contact lens related infectious keratitis. AS-OCT shows a pathology depth of 144 microns. Pre op UDVA was 0.78 logMAR and CDVA was 0.3 logMAR. A 200 micron microkeratome was used for donor and host cornea.

CASE 1 There were no intra or post operative complications. Post operative slit lamp examination demonstrates no residual pathology on the stromal bed, and this is confirmed by AS-OCT. Post op UDVA was 2 logMAR and CDVA was 0.6 logMAR. This patient went on to have cataract surgery 2 years later, which resulted in a UDVA and CDVA of 0.18 logMAR.

CASE 2 29 year old male with central corneal scar of OD secondary to herpes simplex virus keratitis. AS-OCT shows a pathology depth of 160 microns. Pre op UDVA was 0.78 logMAR and CDVA 0.18 logMAR. A 300 micron microkeratome was used for donor and host cornea.

CASE 2 There were no intra or post operative complications. Post operative slit lamp examination demonstrates no residual pathology on the stromal bed, and this is confirmed by AS-OCT. Post operative UDVA was 0.48 logMAR and CDVA was 0.0 logMAR.

CONCLUSIONS AS – OCT is a useful tool for assessing the depth of anterior corneal pathology in the majority of cases Microkeratome assisted superficial anterior lamellar keratoplasty (SALK) is safe and effective for the surgical management of anterior corneal pathologies