The results of PTK using Fourier-Domain Optical Coherence Tomography for Granular Corneal Dystrophy Type 2 Eung Kweon Kim, MD, Ph.D 1 ; Tae-im Kim, MD, Ph.D 1 ; Jung Won Park, MD 2 ; Woosuk Chung, MD 3 1 Corneal Dystrophy Research Institute, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea 2 Daegu Yonsei Eye Clinic, Daegu, Korea 3 Siloam Eye Hospital, Seoul, Korea The authors have no financial interest

Page  2 Introduction  Measuring the exact depth of deposits in granular corneal dystrophy type 2 (GCD2) may allow us not only improve vision by removing most vision threatening deposits, but also save corneal tissue as much as possible during the procedure.

Page  3 The depth of corneal deposit determines treatment strategy and depth of ablation Endothelium ~ lower margin of deposits : 269µm  DLKP Long lattice deposits reaches almost to D’s membrane and pushed the endothelium back  PKP 28 y-o female 8 years after LASIK Upper margin of deposit ~ Bowman’s layer: 31µm Endothelium ~ lower margin of deposits: 363µm  amputating the LASIK flap

Page  4 Purpose  We compared the depths of corneal deposits in GCD2 patient using a RTVue-100 FD-OCT and the actually ablated depths of deposits.  From October 2008 to October 2009  21 eyes of GCD2 patients who undertaken phototherapeutic keratectomy (PTK ) RTVue (Optovue Inc, Fremont, CA) Fourier domain OCT High speed and high resolution OCT Layer by layer assessment 3-D scanning

Page  5 Methods  Pre-operative measurements of deposits by FD-OCT Bowman’s layer ~ granular deposits or diffuse haze (without lattice deposits)  Step ladder ablation assisted by intra-operative slit lamp examination Intra-operative slit lamp examination was undertaken every 10 ㎛ of ablation. PTK was stopped when the diffuse haze and granular deposits removed.

Page  6 Intra-operative step ladder ablation assisted by slit-lamp examination Before ablation After 21 microns ablation After 31 microns ablation After 41 microns ablation

Page  7 (㎛)(㎛) (Patient) The minimal thickness of deposits, estimated depths of deposits by FD-OCT and the actually ablated thickness Results

Page  8 PatientFollow upBaselinePostoperative Deposit thickness by FD-OCT( ㎛ ) Actually ablated thickness( ㎛ ) No. MonthsBCVAUCVABCVAUCVA Min Max Follow up period, visual acuity, deposit thickness by FD-OCT and actually ablated thickness of all included patients. BCVA; best-corrected visual acuity, UCVA; uncorrected visual acuity,

Page  9 (㎛)(㎛) (Patient) Patient 1 Even deposits : 53 ~ 55 ㎛ by FD-OCT → Ablated thickness: 55 ㎛

Page  10 (㎛)(㎛) (Patient) Patient 9 Uneven deposits : 31 ~ 78 ㎛ by FD-OCT → Ablated thickness: 43 ㎛

Page  11  Deposit thickness by FD-OCT ≥ actually ablated depth It may be due to -Superficial part of opacity and corneal stroma was excised together when the epithelium removed. -We measured the maximal depth of corneal deposits when measuring FD-OCT  The depth of corneal deposits measured with FD-OCT before PTK corresponded well to the actually ablated depth with intra-operative slit lamp assisted method. Conclusion