Post on 18-Aug-2015
transcript
Hyperopia & Congenital esotropia
Frequency Degree Management
Habitual Mild Earlier surgery
Occasional Significant(>3.5D) Early surgery contraindicated
Postoperative Eventual increase Secondary Et that improves with
optical Rx
High hyperopia with Accomodative Esotropia with Consecutive Exotropia
Reduce hyperopic power by half
If exotropia still manifest or there is a drop in visual acuity then operate on the consecutive Exotropia after measuring over maximum cyclopegic refraction.
Do you measure with prism over glasses and operate on the measured angle?
A hyperopic patient of +10.00 ref error measured to have 50 pd of esotropia over glasses.
He was operated for 50 pd to achieve ortho
but was undercorrected
with residual eso of 15-20pd
ARTIFACTS INTRODUCED BY SPECTACLE LENSES IN THE MEASUREMENT OF STRABISMIC DEVIATIONS
KIRK D. SCATTERGOOD , M H BROWN,D L GUYTON
AJO 96:439-448,1983
The peripheral prismatic effect of corrective spectacles introduce an
artifact when measuring strabismus
The peripheral prismatic effect of corrective spectacles introduce an artifact when measuring strabismus
cθt∆t
h
11.5 13.5
25
D
∆m
[ ∆t ][ ∆t ] x 100 = x 100 = 100 100 %%[ ∆m ] 1- 0.025 D[ ∆m ] 1- 0.025 D Simplified model
In clinical practice it is the measured deviation that is found first and true deviation must then be calculated
In clinical practice it is the measured deviation that is found first and true deviation must then be calculated
Calculating the true deviation
If glasses are plus Measured deviation = True deviation – 2.5 D% [D-lens power]
If glasses are minus Measured deviation = True deviation + 2.5 D%
In clinical practice it is the measured deviation that is found first and true deviation must then be calculated .
Using the simplified model the authors obtain an expression for true deviation [∆t]
as a percentage of measured deviation [∆m]
[ ∆t ] x 100 = 100 % [ ∆m ] 1- 0.025 D
Plus lenses decrease and minus lenes increase the measured deviation.
Spectacle lens power
True deviation as %of measured deviation
To find true deviationChange measured deviation by Example
-20 67 Decrease by 33%
4/6
-10 80 Decrease by 20%
4/5
PLANO 100 No change 4/4
+10 133 Increase by 33%
4/3
+20 200 Increase by100%
4/2
High Plus lenses in both exo & eso – M D <T D [undercor]
High Minus lenses in both exo & eso – M D >T D [overcor]
This becomes Sx significant with refractive errors of + 5 d
This formula deals with strabismus measurements with distance fixation
If you have built castles in the air, your work need not be lost, that is where they should be, now put the foundations under them.
If you have not measured with C L, with this formula you can still achieve orthophoria
Myope of 10D with measured deviation-exo of 40 pd was operated for the true deviation 32pd (20% less) which gave good alignment
-10D MYOPE WITH EXOTROPIA
POSTOPERATIVE
MEASURED DEVIATION 40PD PREOP