Transcript Change in the Phoria state of the eye after refractive

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
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 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
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–
–
–
–
–
–
–
–
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
Pre op
Post op
30
Distance
Near
5.36 pd
4.45 pd
(SD: 9.69) (SD: 7.84)
25
20
15
7.45 pd
4.90 pd
(SD: 6.59) (SD: 3.2)
10
5
0
P= 0.464
1
2
3
4
5
6
7
8
9
10
11
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
25
20
15
P = 0.261
10
5
0
1
2
3
4
5
6
7
8
9
10
11
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
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