REFRACTIVE SURGERY & STRABISMUS:
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Transcript of REFRACTIVE SURGERY & STRABISMUS:
REFRACTIVE SURGERY & STRABISMUS: PREDICTING &
AVOIDING COMPLICATIONS
Lionel Kowal, Ravindra Battu, Burton Kushner
Lionel Kowal
‘Straight [ening] guy for the queer eye’
Ocular motility clinic RVEEHSenior Clinical Fellow, U of Melbourne
1st Vice President ISAPrivate Eye Clinic
Lionel Kowal
$ interest
MODERN REFRACTIVE SURGERY
> 12 yrs old n = millionsHuge refereed literature
• Patient satisfaction & visual symptoms after LASIK Ophthalmology (2003) 110: 1371-1378
• 97% would recommend LASIK • Halos 30% Glare 27% Starbursts 25% !!
GUIDELINES FOR REF SURGEON /
STRABISMOLOGIST
• PROTECT PTS & REF SURGEONS FROM COMPLICATIONS THAT CAN BE ANTICIPATED
• NOT DENY PTS Q-O-L ENHANCING PROCEDURE
GUIDELINES FOR REF SURGEON /
STRABISMOLOGIST
1. SCREENING TECHNIQUES – FOR ALL PTS
See Kowal [2000] and Kowal & Kushner [2003]
2. THIS TALK: MODERATE / HIGH RISK GROUPS ONLY
REFRACTIVE SURGERY & STRABISMUS
AT RISK GROUPS1.HYPEROPIA
2.MONOVISION 3. ANISOMETROPIA
4. KNOWN / PAST STRAB.
IMPORTANT MESSAGE
HYPEROPIA IS NOT THE MIRROR IMAGE
OF MYOPIA
Population of hyperopes ≠ Population of myopes mild amblyopia
• Predisposed to esodeviation• Mild hyperopes: good UCV
most of their lives
CONSIDER IN EVERY HYPEROPE
Habitual hyperopic spectacle correction is being worn for
good vision and
possibly for control of esodeviation
PREDSIPOSITION TO STRAB IN HYPEROPES
If recognised before RS: patient’s problem
Not recognised before RS: your problem
Success of RS in myopia
Primary factor : change in corneal curvature
2° factors : 2° aberrations, pupil, late ectasia
Factors for Success in hyperopiaALL OF :
Change in corneal curvature &Amount & symmetry of residual hyperopia &Pre-existing predisposition to esodeviation &
Effect of RS on fusional reserve &Decay of accom amp in future &
Amount of latent hyperopia2° factors: Acquired astigmatism, ↑ flap problems, 2° aberrations, loss of
prismatic effects of spectacles, …
Treatment target in Myopia
= Cyclo refraction
Cyclo Ref should = Manifest Ref [within 0.5 DS]
MR > CR : rule out underlying eXodeviation
Treatment target in hyperopia? No easy answer
VISUAL PHYSIOLOGY LESSON #1
TYPES OF HYPEROPIA
Treatment target in hyperopia? Need to know ALL the H subtypes
Absolute: min + for D T-holdWill allow good UCV
Manifest: max + for D T-holdMax effect of H on D & N vision and on alignment
Total H = Cyclo RefLatent [TOTAL – MANIFEST] : will become manifest
TYPES OF HYPEROPIADS
Years
TOTAL = Cyclo Ref
PROBABLY STAYS STABLE FOREVER
TYPES OF HYPEROPIADS
Years
TOTAL
ACCOM AMP
TYPES OF HYPEROPIADS
Years
TOTAL
MANIFEST
ABSOLUTE
TYPES OF HYPEROPIADS
Years
TOTAL
MANIFEST
LATENT: ONLY REVEALED BY CYCLO
TYPES OF HYPEROPIADS TOTAL
M
A
FACULTATIVE
Latent
FACULTATIVE HYPEROPIA
Easily handled by patient’s normal accommodation
ANY result in this range → good UCV
If symmetric, good & comfortable UCV
HYPEROPIA
DSTOTAL
Manifest
Absolute
Facultative
Latent Z
Y
X
X : D age 20 : N 40 : N Y : D 20 : N 40 : N
HYPEROPIA
DSTOTAL
Manifest
Absolute
Facultative
Latent Z
Y
X
Z : RISK OF VISUAL DISCOMFORT, I/MITT BLUR
RE ≠ LE : RISK OF ABNORMAL BINOCULAR VISION. ACCOM SPASM INCREASING ESODEVIATION.
HYPEROPIAAny uncorrected H [short of full manifest H] →
accommodation → accom conv → eso tendency if motor fusion is inadequate
With time, any Latent H → Manifest [=‘Recurrent H’] → accommodation → accom conv → eso tendency ..
Asymmetric accommodation→ accom spasm / [varying] accom convergence → eso tendency ..
Short term patient satisfaction after RS:
Abs H → good UCV.Show that with this minimum vision - improving correction in place there is still adequate
control of any latent E
MEASURING FUSIONAL RESERVES
Medium term patient satisfaction
Correction > Abs H is required : Manifest Hyperopia
Max effect on D & N vision and E
REFRACTIVE SURGERY & STRABISMUS
Assessing results :
VISUAL PHYSIOLOGY LESSON #2
Assessing resultsUse GOOD vision charts
Test monocularly for D to T-hold : ETDRS / NVRI / Bailey Lovie
Snellen: not enough crowding 6/6 – 6/12
Test monocularly for N to T-hold : Rosenbaum J cards / usual cards → N5
OK to assess strength of near addNOT OK to test to T-hold
Psychophysically valid near tests
* NVRI near [ETDRS]: 25cm : N 2.5Can be used @ 40 cm
* Lea : 40 cm : 20/20Can be used @ 25 cm
* M cards : American MA Evaluation of Impairment 5th Edn
T-hold : 0.3
NVRI NEAR TEST BAILEY LOVIE / ETDRS
LEA NEAR TEST
Case 1 : 32 yo WCF
Wearing +4.75, + 5 DS OU no h/o strab
Lasik → residual +2.25, +2 DS < AH
UCV 6/7.5 very happy BUT …… develops ET!
No gls worn : accom amp fine for +2 DS BUT accomm conv ET : not happy
Case 2 : 24 yo WCF
Wearing PALs to control near ETPALs NOT RECOGNISED‘Successful’ RS: ET’ returns
LESSON: look @ the glasses!
Mark Optical Centers Use automated vertometer that will automatically
detect PALs and Δs
REFRACTIVE SURGERY AND STRABISMUS
Case : 50 yo WCF
Wearing +5 DS OU CR +7 DS OUUncorrected H : + 2DS
Ref lensectomy / Array → plano UCV 6/6 OU very happy
2 DS accomm → accomm conv to control XT
20∆ XT very unhappy
The safe hyperope for RS
With AH correction in place: phoria ≤ 5 ∆BIFR > 5 ∆LH ≤ 1 DS
MANY [?most] low hyperopes
REFRACTIVE SURGERY & STRABISMUS
AT RISK GROUPS1.HYPEROPIA
2.MONOVISION 3. ANISOMETROPIA
4. KNOWN / PAST STRAB.
MONOVISIONFawcett n = 118 48 : PLANNED MV
11/48 : ABNORMAL BINOCULAR VISION [ABV] ∑ 23%
* intermittent or persistent diplopia * visual confusion * “binocular blur requiring occlusion to focus comfortably”
NON - MV PTS : 2/70 [3%] HAD ABV
p significant ∑13 pts with ABV
HOW MUCH ANISOMETROPIA TO
PRODUCE ABV ?13 pts with ABV : 1.8 DS
105 pts with no ABV : 0.5 DS
P < 0.001
MONOVISIONFawcett JAAPOS 2001:
SURGICAL MV UNCORRECTABLE DEFICIENCY OF HIGH QUALITY STEREO
Also seen in k/conus
MONOVISION #1
55 yo PRE - REF SX R -2.75/-1x85 6/9 L -2.25/-0.25x180 6/9D: Ortho. N : 8 Δ Esophoria. 60” stereoPOST LASIK : diplopia / visual confusionR: P 6/6 L sc 6/15 Rx -1.75 DSintermittent near ET 6 ΔMV: ↓ motor fusion phoria → tropiaGlasses to correct MV: symptoms fixed
MONOVISION #2
52 yo PRE-REF SXR -4.00/-0.75x180 L-3.00/-1.5x1606 Δ exophoria 60” stereoPOST LASIK : blur, i/mitt diplopiaR +0.25/-0.75x50; L -0.75/-0.25x130[XT] D: 2 Δ, N: 10 ΔMV reduces motor fusion; phoria → tropia Lasik reversal of MV : now asymptomatic
MONOVISION→ FIXATION SWITCH
DIPLOPIA
Amblyopic eye [with scotoma] becomes fixing eye in some situations.
Habitually fixing eye is now the deviating eye in those situations : no scotoma diplopia
no definite cases in this series
UNPLANNED MONOVISION
50 PRK PTS [White; ESA,1997]
3 MO. DELAY B/W EYES1/50: FUSIONAL CONV ↓ FROM 35 TO 5Δ0/50 HAD SYMPTOMSTEMPORARY MV ≠ PERMANENT MV
MONOVISION:PROBLEMS
? 20+%
LONG STANDING SURGICAL MV DEGRADES SENSORY / MOTOR FUSION
MORE THAN CL MV AND TEMPORARY SURGICAL MV
REFRACTIVE SURGERY & STRABISMUS
AT RISK GROUPS1.HYPEROPIA
2.MONOVISION 3. ANISOMETROPIA
4. KNOWN / PAST STRAB.
Knapp’s Law
Axial a’metropia not / less aniseikonogenic
c.f. corneal a’metropia
OTHER FACTORS: RETINAL STRETCHINGSENSORY ADAPTATIONS
CORNEAL REFRACTIVE SURGERY
CONVERTS AXIAL A’METROPIA SAFE ACCORDING TO KNAPP
→
CORNEAL A’METROPIA AT RISK ACCORDING TO KNAPP
EXAMPLE
RE -2 Kav 44LE -4.5 Kav 44.5
To end up with Plano OU, must produce corneal
a’metropia
LENSECTOMY & ANISEIKONIA
REFRACTIVE LENSECTOMY IN HIGH + MAY NOT BE ANISEIKONOGENIC
EG: R +7 L + 0.25 DS/ -1.5 DC AFTER L LENSECTOMY Dissociated with 10 ∆ vertical ZERO subjective aniseikonia with gls!1% with Awaya testA’metropia @ nodal point ≠ cornea
REFRACTIVE SURGERY & STRABISMUS
AT RISK GROUPS1.HYPEROPIA
2.MONOVISION 3. ANISOMETROPIA
4. CURRENT / PAST STRAB.
4. KNOWN / PAST STRABISMUS
1. STRAIGHTENED STRAB2. CURRENT STRAB
3. WEARING ∆4. ASTIGMATISM + STRAB
RS IN STRABISMICMISALIGNED OR STRAIGHTENED
NEED TO ANSWER:Q1. RISK OF DETERIORATION OF
ALIGNMENT Q2. RISK OF DIPLOPIA
- SPONTANEOUSLY [NO REF SX] - SUCCESSFUL REF SX- IMPERFECT REF SX
RISK OF SPONTANEOUS DETERIORATION
‘SPONTANEOUS DETERIORATION’ WILL BE ATTRIBUTED BY PT TO RS
RISK IF:• VERSION / DUCTION DEFICIT
ALREADY PRESENT• CVD / ALPHABET PATTERN
RISK OF SPONTANEOUS DIPLOPIA
2 SITUATIONS:
STRAB ANGLE STAYS SAME :DEPTH OF SCOTOMA IMPORTANT
STRAB ANGLE INCREASES / CHANGES:SIZE OF SCOTOMA IMPORTANT
RISK OF SPONTANEOUS DIPLOPIA
DEPTH: BAGOLINI FILTER BAR - RETINAL
RIVALRY [RR]HOW MUCH RR TO OVERCOME A SUPP
SCOTOMA?
ESP RELEVANT TO ACQ SUPPRESSION
BAGOLINI FILTER BAR aka SBISA BAR
RISK OF SPONTANEOUS DIPLOPIA
SIZE :
POLARIZED 4 DOT TEST [ARTHUR]
POLARISED 4 DOT TEST BRIAN ARTHUR
APPROXIMATE SCOTOMA SIZE
TEST TO PATIENT SCOTOMA SIZE DISTANCE (feet) (degrees)
1 5.25 2 2.63 3 1.75
4 1.32 5 1.05 6 0.88 ~ ~
~ ~10 0.5315 0.3520 0.26
SUPPRESSION SCOTOMA [SS]
SS NOT ALWAYS ‘SAFE’SMALL SHALLOW SS MORE AT RISK FOR
DIPLOPIA THAN LARGE DEEP ONE
BFB : > 5-6 SAFE 1-2 ? UNSAFE
P4D : ?5 SAFE 0.5 ? UNSAFE
SUPPRESSION EG #1
I/MITT 15+Δ VERTICAL PHORIANEVER HAD DIPLOPIA
BFB #2P4D SCOTOMA 1 DEG W4D: DIPLOPIA
RR OVERCOMES SS → RISK OF SPONT DIPLOPIA
4. KNOWN / PAST STRABISMUS
1. STRAIGHTENED STRAB2. CURRENT STRAB
3. WEARING ∆4. ASTIGMATISM + STRAB
WEARING PRISM
? INTENTIONAL ? MAINSTREAM ? QUIRKY
? INADVERTENT
NEUTRALISE & THEN MEASURE FUSIONAL
RESERVES
4. KNOWN / PAST STRABISMUS
1. STRAIGHTENED STRAB2. CURRENT STRAB
3. WEARING ∆4. ASTIGMATISM + STRAB
ASTIGMATISM WITH STRAB
BEWARE OF CHANGE IN CYL AXIS
WHEN PT CHANGES :
FROM BINOCULAR TO MONOCULAR FIXATION
1/6 CHANGES BY ≥ 18 DEG
SITTING TO SUPINE
De Faber : 1/4 CHANGES BY ≥ 13 DEG
Becker : No change
EXPECT GREATER CHANGES IN AXIS IF ANY CYCLOVERTICAL STRAB
OTHERS 1.
GLASSES HAVE SUCCESSFULLY CAMOUFLAGED POS / NEG KAPPA
NOW : PSEUDO STRAB WITHOUT GLS
OTHERS 2.
VERTICALLY DECENTERED TREATMENTSHORIZONTAL KAPPA : COMMONVERTICAL KAPPA : 1/5000 IN A STRAB PRACTICE
HORIZONTAL DECENTRATION: → INDUCED H ∆ ‘ABSORBED’ BY MOTOR FUSION →
LITTLE / NO RISK OF DIPLOPIA
VERTICAL DECENTRATION: DIPLOPIA MORE LIKELY
OTHERS 2.
VERTICALLY DECENTERED TREATMENT
-23 DS LASIK !?POOR FIXATION? VERTICAL KAPPA14Δ VERTICAL DIPLOPIA
IMAGES SUPERIMPOSED BY Δ OR BY HCL
OTHERS 2.
OTHERS 3.CEREBRAL DIPLOPIA
BILATERAL MONOCULAR DIPLOPIA
NOT REFRACTIVE NOT FIXED / EXPLAINED BY HCL /
TOPOGRAPHY / ABERROMETRY
WELL … MAYBE …
REFERENCESKOWAL L
Clin Exp Ophthal 2000: 28, 344-346New review submitted ? 2004/ 5
……………………………………………KUSHNER B & KOWAL L
Archives Ophthal March 2003 28 Patients……………………………………………
KOWAL L & BATTU R‘Refractive Surgery and Diplopia’ in
‘STEP BY STEP LASIK SURGERY’ VAJPAYEE et al 2003. Chapter 13
REFRACTIVE SURGERY & STRABISMUS
THANK YOU