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

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

• Dr Umang Mathur, Dr Archana Gupta, Dr Suma Ganesh
• Dr Shroffs 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

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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

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Methods

• Inclusion criteria
• Bilateral myopia
• Agegt18 yrs
• Willingness for refractive surgery
• Eligibility for refractive surgery
• Anisometropia lt 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

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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
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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
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Results

• Of the 87 screened subjects, only 70 were found
  eligible these were screened and 11(15) were
  enrolled

Parameters Results
Female Male 101
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
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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
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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

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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 12315-321. Schuler E,
Silverberg M, Beade P, Moadal K. Decompensated
strabismus after laser in situ keratomilleusis.
J Cataract Refract Surg 2000 26 1552-4.
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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 12315-321.
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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

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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