Transcript Refractive Surgery and Diplopia

REFRACTIVE SURGERY
& STRABISMUS:
PREDICTING &
AVOIDING
COMPLICATIONS
Lionel Kowal, Ravindra Battu, Burton Kushner
Lionel Kowal
‘Straight [ening] guy for the queer eye’
Ocular motility clinic RVEEH
Senior Clinical Fellow, U of Melbourne
1st Vice President ISA
Private Eye Clinic
Lionel Kowal
$ interest
MODERN REFRACTIVE
SURGERY
> 12 yrs old
n = millions
Huge 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 GROUPS
1.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 hyperopia
ALL 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 hyperopia
2° 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-hold
Will allow good UCV
Manifest: max + for D T-hold
Max effect of H on D & N vision and on alignment
Total H = Cyclo Ref
Latent [TOTAL – MANIFEST] : will become manifest
TYPES OF HYPEROPIA
DS
TOTAL = Cyclo Ref
PROBABLY STAYS STABLE FOREVER
Years
TYPES OF HYPEROPIA
DS
TOTAL
ACCOM AMP
Years
TYPES OF HYPEROPIA
DS
TOTAL
MANIFEST
ABSOLUTE
Years
TYPES OF HYPEROPIA
DS
TOTAL
MANIFEST
LATENT: ONLY
REVEALED BY CYCLO
Years
TYPES OF HYPEROPIA
DS
TOTAL
Latent
M
FACULTATIVE
A
FACULTATIVE HYPEROPIA
Easily handled by patient’s normal
accommodation
ANY result in this range → good
UCV
If symmetric, good & comfortable
UCV
HYPEROPIA
TOTAL
DS
Latent
Z
Y
Manifest
Facultative
X
X : D
age 20 : N
40 : N
Y : D
20 : N
40 : N
Absolute
HYPEROPIA
TOTAL
DS
Latent
Z
Y
Manifest
Facultative
X
Absolute
Z : RISK OF VISUAL DISCOMFORT, I/MITT BLUR
RE ≠ LE : RISK OF ABNORMAL BINOCULAR VISION.
ACCOM SPASM  INCREASING ESODEVIATION.
HYPEROPIA
Any 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 results
Use 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 add
NOT OK to test to T-hold
Psychophysically valid near tests
* NVRI near [ETDRS]: 25cm : N 2.5
Can be used @ 40 cm
* Lea : 40 cm : 20/20
Can 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
Lasik → residual +2.25, +2 DS
no h/o strab
< AH
very happy
BUT …… develops ET!
No gls worn : accom amp fine for +2 DS
BUT accomm conv  ET : not happy
UCV 6/7.5
Case 2 : 24 yo WCF
Wearing PALs to control near ET
PALs 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 OU
Uncorrected 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 GROUPS
1.HYPEROPIA
2.MONOVISION
3. ANISOMETROPIA
4. KNOWN / PAST STRAB.
MONOVISION
Fawcett
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
MONOVISION
Fawcett
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 6/9
D: Ortho.
N : 8 Δ Esophoria. 60” stereo
POST LASIK : diplopia / visual confusion
R: P 6/6
L sc 6/15 Rx -1.75 DS
intermittent near ET 6 Δ
MV: ↓ motor fusion
phoria → tropia
Glasses to correct MV: symptoms fixed
MONOVISION #2
52 yo PRE-REF SX
R -4.00/-0.75x180
L-3.00/-1.5x160
6 Δ exophoria 60” stereo
POST LASIK :
blur, i/mitt diplopia
R +0.25/-0.75x50; L -0.75/-0.25x130
[XT] D: 2 Δ, N: 10 Δ
MV 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 EYES
1/50: FUSIONAL CONV ↓ FROM 35 TO 5Δ
0/50 HAD SYMPTOMS
TEMPORARY 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 GROUPS
1.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 STRETCHING
SENSORY ADAPTATIONS
CORNEAL REFRACTIVE
SURGERY
CONVERTS AXIAL A’METROPIA
SAFE ACCORDING TO KNAPP
→
CORNEAL A’METROPIA
AT RISK ACCORDING TO KNAPP
EXAMPLE
RE -2 Kav 44
LE -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 test
A’metropia @ nodal point ≠ cornea
REFRACTIVE SURGERY &
STRABISMUS
AT RISK GROUPS
1.HYPEROPIA
2.MONOVISION
3. ANISOMETROPIA
4. CURRENT / PAST STRAB.
4. KNOWN / PAST
STRABISMUS
1. STRAIGHTENED STRAB
2. CURRENT STRAB
3. WEARING ∆
4. ASTIGMATISM + STRAB
RS IN STRABISMIC
MISALIGNED 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
DISTANCE (feet)
1
2
3
4
5
6
~
~
10
15
20
SCOTOMA SIZE
(degrees)
5.25
2.63
1.75
1.32
1.05
0.88
~
~
0.53
0.35
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
P4D : ?5 SAFE
1-2 ? UNSAFE
0.5 ? UNSAFE
SUPPRESSION EG #1
I/MITT 15+Δ VERTICAL PHORIA
NEVER HAD DIPLOPIA
BFB #2
P4D SCOTOMA 1 DEG
W4D: DIPLOPIA
RR OVERCOMES SS → RISK OF SPONT DIPLOPIA
4. KNOWN / PAST
STRABISMUS
1. STRAIGHTENED STRAB
2. CURRENT STRAB
3. WEARING ∆
4. ASTIGMATISM + STRAB
WEARING PRISM
? INTENTIONAL
? MAINSTREAM ? QUIRKY
? INADVERTENT
NEUTRALISE & THEN
MEASURE FUSIONAL
RESERVES
4. KNOWN / PAST
STRABISMUS
1. STRAIGHTENED STRAB
2. 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 TREATMENTS
HORIZONTAL KAPPA : COMMON
VERTICAL 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 KAPPA
14Δ 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 …
REFERENCES
KOWAL L
Clin Exp Ophthal 2000: 28, 344-346
New 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