EFFECTS OF REFRACTIVE SURGERY ON BINOCULAR VISION : PRE- AND POST- LASIKBINOCULAR VISION : PRE- AND POST- LASIK

VALUES

JOSÉ DE JESÚS ESPINOSA GALAVIZ, OD, MSc, FCOVDELIZABETH CASILLAS CASILLAS, OD, MSc

JAIME BERNAL ESCALANTE OD MScJAIME BERNAL ESCALANTE, OD, MScSERGIO RAMÍREZ GONZALEZ, OD MSc

VI INTERNATIONAL CONGRESS OF BEHAVIORAL OPTOMETRYAPRIL 2010

Introduction More than a million of refractive surgery procedureswere done in USA in 2002

Some reports about complications after surgery onbinocular vision as a result of the procedure haveappeared

R dl f th t i b t ith th Regardless of the controversy is about with theprocedure with the refractive amblyopia patient,thousands could have the procedure without acomprehensive binocular vision evaluation

Binocular Vision Values

GENERAL OBJECTIVE

Determine the effects of refractive surgery (LASIK procedure) on binocular vision by comparing binocular  vision pre surgery values against postbinocular  vision pre‐surgery values against post‐surgery values.

SPECIFIC OBJECTIVES Determine binocular vision values in patients whodecided to have a refractive surgery, specifically aLASIK procedure before surgeryLASIK procedure before surgery

Determine binocular vision values in the same patients Determine binocular vision values in the same patientsafter surgical procedure

Compare both results and analyze the changes inbinocular vision values

Methods The research was done in “Visual Láser Ocular” inCiudad Victoria, México from May 30th 2007 until July31th of 2008.31th of 2008.

The study was done in patients who decided to haveLASIK for either myopia, hyperopia, with or without

i i All l dastigmatism. All were selected. Sample: 15 patients; 10 women and 5 men. Age rangefrom 24 to 39.from 24 to 39.

All were selected by the ophthalmologist who had onlydone: refractive studies, corneal topography, ultrasonic

h t f d l ti d l t tipachymetry, fundus evaluation, and corneal testing.

Hypothesis HYPOTHESIS

Refractive surgery  DOES change the binocular vision values

ALTERNATE HYPOTHESIS:

Refractive surgery DOES NOT change binocular vision valuesvalues

Statistical AnalysisStatistical Analysis Statistical analysis was done using a “T” paired test using SPSS 

Version   Soft are  ith the data grouped using the OEP modelVersion 17 Software with the data grouped using the OEP model:a) Habitual phoria for far (#3)b) Habitual phoria for near (#13A)) I d d  h i  (#8)c) Induced phoria (#8)d) True adduction (first blur) (#9)e) Convergence (break and recovery) (#10 break and #10 rec)f) Abd i  (b k  d   (  b k  d    )f) Abduction (break and recovery (#11 break and #11 rec )g) Base out to blur‐out (#16A) h) Base out break (#16B/B)

( )i) Base out to recovery (#16B/R)j) Base in to blur‐out (#17A)k) Base in break (#17B/B)l) Base in to recovery (#17B/R)

ExpectativeExpectativePrueba Morgan

(1944ª, Saladin y Sheedy

Jackson y Goss (1991)

Expectativas OEP(1944 ,

1944b)Sheedy (1978)

Goss (1991) OEP

#3 Habitual phoria far .5 exo#13A Habitual phoria near 6 exo

#8 Induced phoria far 1 exo 1 exo 1 exo .5 exo#9 BO blur far 9 15 14 7 a 9#9 BO, blur far 9 15 14 7 a 9

#10 BO break/recovery 19/10 28/20 23/6 19/10

#11 BI break/recovery 7/4 8/5 12/4 9/5#12 Vertical phoria far Orto

#13 3 0 3 6#13B Induced phoria near 3 exo 0.5 exo 3 exo 6 exo#16ª BO blur near 17 22 21 15#16B BO break/recovery 21/11 30/23 27/10 21/15#17ª BI blur near 14 14 15 14#17B BI break/recovery 21/13 19/13 21/9 22/18#17B BI break/recovery 21/13 19/13 21/9 22/18#18 Vertical phoria near Orto#19 Amplitud lente

negativo5.00 D

#20 (PRA) -2.37 -2.14 -2.25 a -2.50#21 (NRA) +2 00 +1 91 +1 75 a#21 (NRA) +2.00 +1.91 +1.75 a

+2.00

Final ResultsFinal ResultsTest Media Pre Media Post Difference

Habitual phoria far -0 73 -0 10 +0 63Habitual phoria far 0.73 0.10 +0.63

Dist BO Blur (first blur) 17.00 13.00 -4.00

Dist BO Break 23.87 19.40 -4.47

Dist BO Recovery 9.0 7.13 -1.87

Dist BI Break 9.53 8.13 -1.4

Dist BI Recovery 2.83 2.60 -0.23

Habitual phoria Near -1.33 1.03 +2.36

Near BO Blur 22.80 17.60 -5.20

Near BO Beak 28.66 22.53 -6.13

Near BO Recovery 11.80 10.20 -1.6

Near BI Blur 15.25 12.50 -2.75

N BI B k 23 46 20 00 3 46Near BI Break 23.46 20.00 -3.46

Near BI Recovery 9.26 8.73 -0.53

GraphG ap

StatysticalStatyst caTest Media Significance level (p)

Habitual phoria far .633 .482

Habitual phoria near 2.3667 .160

BO blur far 4.57143 .176

BO break far 4.667 .147

BO recovery far 1.8667 .244

BI break far 1.4000 .280

BI f 2337 811BI recovery far .2337 .811

BO blur-out near 5.200 .395

BO break near 6.1333 .059

BO recovery near 1.600 .552

BI blur-out near 2.7500 .378

BI break near 3.4667 .319b ea ea 3 66 3 9

BI recovery near .5333 .751

RESULTS On the basis of the above results, the hypothesis

is rejected.f f This means, from an statistic point of view

refractive surgery DOES NOT change binocular vision valuesvision values

However…

Discussion It is well known that the prescription given to a patient can alter phoria values.  Example: an overcorrection in myopia with exophoria tends to decrease phoria value  myopia with exophoria tends to decrease phoria value, or even in some cases, change it into esophoria.

It is also known  the most of refractive surgeons tend It is also known, the most of refractive surgeons tend to overcorrect in myopia cases in order to anticipate future changes increasing  in myopia values.

Discussion Nevertheless the results shown binocular vision was 

i f   h     h  i   h i   d 

Discussion

satisfactory, there were changes in phoria and binocular vision values 

An exophoric myopic patient has never face symptoms  An exophoric myopic patient has never face symptoms of esophoria

Although  this is still in analysis , 85% of patients in Although  this is still in analysis , 85% of patients in this study, complained about near vision problems as accommodative asthenopia, fatigue, headache, etc.

Discusion We believe all of this is due to the overcorrection of myopia.U f l     f  h   f i    h     Unfortunately, most of the refractive surgeons have no knowledge about binocular vision evaluation and treatment procedurestreatment procedures.

Discussion In regard to convergence and divergence resultant values, the was a good degree of variability. There were patients who showed minimal modifications against patients who showed minimal modifications against previous values. Some others had better values and others had worse values.

For us, this results mean the re‐organization that current in an organism as result of a LASIK procedure

It is result of the stress imposed on the visual system Thus, a full binocular evaluation should be done b f   f i  before refraction surgery.

Discussion There are reports about unstable AC/A ratios after refractive surgery that get stabilization around 6 to 9 months after (Prakash et al; 2007)months after (Prakash et al; 2007)

Likewise, visual therapy for patients having symptomatic BV disorders after Lasik procedure symptomatic BV disorders after Lasik procedure (Faktorovich; 2008)

Question is: Is the patient prepared to a new p p penvironment for near vision? 

ConclusionConclusion Although  only one out of 15 patients shown diplopia  Although, only one out of 15 patients shown diplopia for one day (day after surgery), we believe it is important to test binocular vision status before the 

i l d i i  i   d   O l   ith thi  d t    th  surgical decision is made.  Only with this data can the OMD evaluate risks about diplopia after the procedure.

85% of patients in this study complained about  near vision problems after their surgery.

It would be desirable for refractive surgeons to lean on  It would be desirable for refractive surgeons to lean on functional optometry in order to evaluate binocular vision.

C l iConclusionE l t   l  th   tt   b t  ti   Evaluate properly the matter about overcorrection; there are some studies proving that myopia increases slightly or not at all after LASIK treatment.s g t y o ot at a a te S t eat e t.

It is necessary to have more similar research in order to state a predictable model of binocular vision results after surgery. 

Gracias Special Thanks to: Dr. Paul Harris for his i l bl  h l  i  invaluable help in preparing the document

Robert Williams and  Robert Williams and OEP for all the support

Dr. Berenice Velazquez qfor her help in lecture preparation