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overnight orthokeratology

Dr Widjayanti Utoyo, SpM

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Introduction

To achieve optimal fit with reverse geometry Contex OK lenses

To determine a time course and the stability of visual & corneal changes in achieving maximal refractive, corneal curvatures, & thickness changes after overnight wear of OK (B &D)

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methods

Both eyes (10 subj) fitted Measure 1day, 1 week, 1&3

month:1. UCVA

2. Refractive correction

3. Contrast sensitivity

4. Corneal curvature

5. Corneal thickness

Lens removal, 4,8, &12 hours after l.r.

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results

UCVA, refract correct, contrast s, c curvature: change significantly

Max level : end of 1 week After 3 month : c epith thick

reduced 19 um

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conclusion

Succesful fitting: understanding lens-cornea relationship

Full effect : 1 week Visual & corneal changes stable

for all waking hours

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History

Introduce 1960 Save but limited efectiveness Central BC flatter than center c curvature 2nd curve: 3-17 D steeper than central

BC 3rd curve: close match mid peripheral

cornea 4th curve: flatter than all other curve

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Function Central BC: central curv flattening 2nd curve : stability, enhance central c

flattening Accelerated reduced myopia Wear lens only 8 hours overnight Need to study recovery data to 12 hours

after removal Swarbick: thinning c epit 28 day, 6 hrs

lenses Nicholas : thinning -> redistribution of

corneal tissue

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Subjects

10 subject, 21-43 yrs, myop< 3 D, ast < 1 D

No ocular& sist disease Not worn c. l. 1 week before 2 excluded

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Lenses Fluorosilicone acrilate polymer + D&C green no

6 as color O2 permeabil: 8x 10 -5 at 35 ‘ C Contex OK B&C 4 zones :1. 1st 6.00 mm2. 2nd 3-17 D steeper3. 3rd 0-5 D steeper than BC but flatter than 2nd

curve4. Alignment zone B: 0.9, D: 1.0 & fits tighter5. 4th : edge lift to enhance tear flow

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Procedure

Compr examine UCVA : Bailey-Lovie chart Binocular small letter c.s. (Pelli-

Robson) Cent c curve : keratometer

topografi& thickness : Orbscan topographer (B& L)

Total thickness : Tandem ConfocalScanning Microscope

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Procedure

Profession Fitting & inform Guide: BC = flat kerato reading - Spherical eq - -.75 D

BC (D)= 42.5 – 3.00 – 0.75 BC (D) = 38.75 D atau 8.71 mm 2nd curve : BC 8.5 Use 10.6 mm diameter Use c.l. 1 hr before sleep

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Procedure

Analysis : Excel, versi 2000 (Microsoft)

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Average baseline data

data average Std dev

Ref err(sph eq) -1.76 0.70

UCVA 0.49 0.22

U contr sens(log) 0.75 0.40

Horiz keratometr 43.55 1.45

Vertical kerato 44.24 1.52

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Spherical equivalent

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Mean contrast sens

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Change in Rx/

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Mean central horizontal kerato

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Discussion

OK procedure different (’70& 80): reverse geometry & High O2 transmissib overnight

Well centered & OZ diameter increase : peripheral distortion

Predicted c BC radius : close 2nd curve radius least predict Cornea remodelled : 8 hrs

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Discussion

The change at 1 week, 1& 3 month similar for all parameters

All except Contrast sens recover, but less than day 1

Contrast sens, not depend on c curvature but on c clarity

Extremely strong relationship : changes in flat corneal curv. & refract err

Average c. r.e: 2.12 D, f.c.c : 1.95 D

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Discussion

R. change : curve, optical path length, aberations

Spherical central b.c. radii flatten both principal meridians equally

C. toricity 0.75; 3 mth 0.80D C. thick : swelling after use Swarbick : thinning Confocal : both swelling & thinning