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


Years

TOTAL

ACCOM AMP


Years

TOTAL

MANIFEST

ABSOLUTE


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


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

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

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




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


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


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

WEARING PRISM

? INTENTIONAL ? MAINSTREAM ? QUIRKY

? INADVERTENT

NEUTRALISE & THEN MEASURE FUSIONAL

RESERVES

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


THANK YOU

refractive surgery & strabismus:

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