Change in the Phoria state of Change in the Phoria state of the eye after refractive surgery the eye after refractive surgery

for myopiafor myopia

Dr Umang Mathur, Dr Archana Gupta, Dr Suma GaneshDr Umang Mathur, Dr Archana Gupta, Dr Suma GaneshDr Shroff’s Charity Eye Hospital, Daryaganj, New Dr Shroff’s Charity Eye Hospital, Daryaganj, New

Delhi 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

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

Methods

Inclusion 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

Methods

Pre operative work upRoutine 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

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

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 - 4.76 D (SD: 2.93)

Mean Anisometropia 0.71 D (SD: 0.76)

All the deviations were exodeviations

Change in the deviation post operatively

0

5

10

15

20

25

30

distance deviation pre op 0 30 4 0 0 2 0 18 0 3 2

distance deviation post op 0 25 2 0 0 10 0 10 0 0 2

1 2 3 4 5 6 7 8 9 10 11

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

0

5

10

15

20

25

near deviation pre op 3 25 5 3 3 4 3 10 6 8 12

near deviation post op 3 8 2 3 0 5 4 10 5 4 10

1 2 3 4 5 6 7 8 9 10 11

P = 0.261

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

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; 12:315-321.Schuler E, Silverberg M, Beade P, Moadal K. Decompensated strabismus after laser in situ keratomilleusis. J Cataract Refract Surg 2000; 26: 1552-4.

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; 12:315-321.

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

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