overnight orthokeratology
DESCRIPTION
refraksiTRANSCRIPT
04/20/23 1
overnight orthokeratology
Dr Widjayanti Utoyo, SpM
04/20/23 2
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