1. Change in the Phoria state of the eye after refractive surgery for myopia
Dr Umang Mathur, Dr Archana Gupta, Dr Suma Ganesh
Dr Shroff’s Charity Eye Hospital, Daryaganj, New Delhi
The authors do not have any proprietary or financial interest in a product, method or material used in this study. There are no competing interests in this study

2. Aim
To study the change in the phoria state of the eye after refractive surgery for myopia
Design: Prospective non comparative study
All patients interested in refractive surgery were screened

3. Methods Inclusion criteria Exclusion criteria Bilateral myopia
Age>18 yrs
Willingness for refractive surgery
Eligibility for refractive surgery
Anisometropia < 1D
Exclusion criteria
Unilateral
Amblyopia
Presence of any other ocular disease
Any previous intraocular surgery
Patient not willing for refractive surgery
Patients unsuitable for refractive surgery
Planned monovision

4. Methods Pre operative work up Routine LASIK work up including
The spectacles worn were evaluated for the power, presence of a bifocal segment and any prism if incorporated
For correction, the manifest refraction was aimed for in all cases - no deliberate over or under-corrections attempted.
Orthoptic evaluation
Head posture evaluation
Hirschberg test
Cover test
Prism bar cover test for distance and near (and in all positions of gaze) both with and without glasses wherever possible
Extra ocular movements
Near point of convergence, near point of accommodation
Fusional amplitudes
Worth 4 dot test for fusion/suppression
Ran dot E for stereopsis.
Patients with a deviation of greater than or equal to three prism diopters* were
included in the study

5. Methods Standard LASIK technique
LASIK flap created with a Hansatome at 160 or 180 microns depth and the stromal bed was ablated using a Visx star S4 excimer laser
Postoperative evaluations
one week
six weeks
three months
six months post
Orthoptic evaluation at each visit
Any symptoms/ complaints in near work activities
Statistical Analysis: The paired t test was used in analyzing the results

6. Results
Of the 87 screened subjects, only 70 were found eligible; these were screened and 11(15%) were enrolled
Parameters
Results
Female: Male
10:1
Average age
26.46 yrs (SD: 7.29; range: 19 to 45 yrs
Average MRSE RE
-4.81 D (SD: 3.22)
Average MRSE LE
D (SD: 2.93)
Mean Anisometropia
0.71 D (SD: 0.76)
All the deviations were exodeviations

7. Change in the deviation post operatively
Pre op
Post op
Distance
5.36 pd (SD: 9.69)
4.45 pd (SD: 7.84)
Near
7.45 pd (SD: 6.59)
4.90 pd (SD: 3.2)
P= 0.464
P = 0.261

8. Discussion
Approximately 1.5 million LASIK being done every year - myopia - most common diagnosis… it is important to anticipate and predict postoperative complications
In our study… phorias present in 15% of the patients who underwent refractive surgery
Although not statistically significant, there was a general trend towards an overall improvement in the degree of deviation post operatively

9. Review of Literature
But, there are multiple case reports of diplopia/decompensation post refractive surgery !!!
On detailed review, all had risk factors:
Targeted monovision
Unilateral refractive surgery
Anisometropia
Amblyopia
Kushner B J, Lionel Kowal. Diplopia after Refractive Surgery: Occurrence and Prevention.
Arch Ophthalmol 2003; 12:
Schuler E, Silverberg M, Beade P, Moadal K. Decompensated strabismus after laser in situ
keratomilleusis. J Cataract Refract Surg 2000; 26:

10. Discussion
Deviations preoperatively controlled with deliberate myopic overcorrection or prisms in glasses - missed in the pre operative evaluation* There was no such case in our series … ours was a controlled study with strict inclusion and exclusion criteria
*Kushner B J, Lionel K. Diplopia after Refractive Surgery: Occurrence and Prevention.
Arch Ophthalmol 2003; 12:

11. Discussion
Strengths
Among the first prospective, controlled studies for myopes in the general population presenting for refractive surgery
Most reports to date have been isolated case reports that have been retrospectively reviewed once the decompensation settled in
Drawbacks
Cases with risk factors excluded
Larger prospective study needs to be planned

12. Conclusion
Refractive surgery for myopia does not significantly alter the phoria state of the eye Considering the increasing number of refractive surgeries being done, and the implications of missing a well controlled deviation pre operatively, orthoptics should be a part of pre operative work ups