The results of PTK using Fourier-Domain Optical Coherence Tomography for Granular Corneal Dystrophy Type 2

Eung Kweon Kim, MD, Ph.D1; Tae-im Kim, MD, Ph.D1; Jung Won Park, MD2; Woosuk Chung, MD3

1Corneal Dystrophy Research Institute, Department of Ophthalmology,

Yonsei University College of Medicine, Seoul, Korea 2Daegu Yonsei Eye Clinic, Daegu, Korea 3Siloam Eye Hospital, Seoul, Korea

The authors have no financial interest

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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.

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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

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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

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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.

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Intra-operative step ladder ablation assisted by slit-lamp examination

Before ablation After 21 microns ablation

After 31 microns ablation After 41 microns ablation

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( ㎛ )

(Patient)

The minimal thickness of deposits, estimated depths of deposits by FD-OCTand the actually ablated thickness

Results

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Patient Follow up Baseline PostoperativeDeposit thickness by

FD-OCT( ㎛ ) Actually ablated

thickness( ㎛ ) No. Months BCVA UCVA BCVA UCVA Min Max

1 9 0.4 0.4 0.8 0.5 53 552 8 0.4 1 0.6 53 56 453 3 0.6 0.2 41 404 6 0.2 0.3 106 122 1055 8 0.4 0.9 103 109 726 8 0.8 0.6 1 47 447 6 0.5 0.6 0.5 42 398 7 0.3 0.9 44 47 529 3 0.3 0.2 0.4 31 78 43

10 3 0.1 0.9 97 8811 3 0.5 0.9 75 100 10012 3 0.05 0.1 0.6 31 63 5813 3 0.2 0.7 59 5714 3 0.3 1 56 72 5915 3 0.5 0.8 53 5116 1 0.8 0.3 28 88 5017 1 0.3 0.7 34 72 5018 1 0.2 0.05 0.1 72 7119 1 0.4 0.3 0.9 28 47 3020 0 0.4 0.5 78 5121 0 0.3 0.2 31 44 60

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,

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( ㎛)

(Patient)

Patient 1 Even deposits : 53 ~ 55 ㎛ by FD-OCT → Ablated thickness: 55 ㎛

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( ㎛)

(Patient)

Patient 9 Uneven deposits : 31 ~ 78 ㎛ by FD-OCT → Ablated thickness: 43 ㎛

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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