Transcript Pre-anesthesia

Torsional Changes During
Routine Ophthalmic
Anesthesia
Eunice Yook, BS, MS, John P. Hatch, PhD, Kent L. Anderson, MD, PhD
Department of Ophthalmology
The University of Texas Health Science Center at San Antonio,
The authors have no financial interest in the subject matter of this e-poster.
ABSTRACT
Purpose: The purpose of this study is to investigate the torsional changes of the
eye after anesthesia during cataract extraction. With this information, we hope to
augment current practices by determining whether pre-anesthesia markings are
indicated before cataract surgery, especially when using toric lenses.
Methods: This study recruited 30 patients from a clinic affiliated with a medical
university in San Antonio, Texas. Before anesthesia was administered, the medial
and lateral canthus was marked with a sterile marking pen in the upright position.
Next, using a Bubble Level Toric Marking System, marks were made at the medial
and lateral limbus. A photo was obtained at a fixed distance. After anesthesia was
administered, a second photo was taken. Differences were measured using a
screen protractor, and results were analyzed in IBM SPSS for Windows.
Results: Pre-anesthesia and post-anesthesia photos were taken and compared in
30 eyes. Mean cyclotorsion was 4.20° with a standard deviation of 3.05°. Values
ranged from 0.18° to 10.02°. The 95% confidence interval was 3.06-5.33°.
Conclusion: Previous studies have found clinically significant alterations of
postoperative refractions at 15°. Our study showed all subjects had less than a
15° change, suggesting that pre-anesthesia markings may not be required. Instead,
the surgeon can mark the eye intraoperatively after anesthesia has been
administered to guide placement of toric lenses.
INTRODUCTION
•

Several factors may affect ocular torsion:
 Changes in position (supine vs. upright)
 Extra-ocular muscle paralysis
 Rotation of the intraocular lens (IOL) in the bag
In regards to positional influences, the current agreement is
that regardless of correcting for position, postoperative
results are the same1.
INTRODUCTION
•

Since extra-ocular muscles contribute to the tone, curve and
position of the eyeball when contracted1 (Figure 1),
anesthesia induced muscle paralysis may affect eye position
during ocular surgery2.
Torsional effects during anesthesia are currently unknown.
INTRODUCTION
Astigmatism
• Torsional changes will affect those with astigmatism.
• New toric IOLS can correct for astigmatism, but require
precise positioning, and are not covered by insurance.
• Previous studies have shown that a change more than 15°
in the axis during refractive surgery reduces the amount of
astigmatism corrected by 50%4,5.
• If anesthesia causes a significant cyclotorsion, surgeons may
find it beneficial to mark the eye before anesthesia.
• Therefore, by investigating torsional changes under
anesthesia, one can determine whether preoperative
markings are indicated for cataract surgery.
STUDY DESIGN




Prospective
Noncomparative
Enrollment of 30 patients
Subjects recruited from a clinic affiliated with a large
medical university in San Antonio, Texas.
Inclusion criteria
 Patients who were cleared exclusively for routine cataract
extraction with IOL placement.
METHODS
Pre-anesthesia:
1. Eyelid marked in the upright position.
1.
Temporal and nasal limbus marked with Mastel Bubble
Level Toric Marking System. (Figure 2)
2.
Sony Cybershot Camera in Easy Mode camera was used to
obtain a photo of the eye at a fixed distance. (Figure 3a, 4a)
Figure 2: Mastel Bubble Level Toric Marking System
METHODS
Post-anesthesia:
1. Second photo was taken after the presence of extra-ocular
muscle paralysis (Figure 3b, 4b).
1.
Effect of anesthesia was confirmed by presence of
chemosis, a reaction to the anesthesia. (Figure 3b).
1.
Differences measured using the Iconico Screen Protractor.
1.
Results were analyzed in Excel.
METHODS
Area of
conjunctival
chemosis
Figures 4a and 4b:
Position of eye pre- and
post local anesthesia,
respectively.
b. Post-anesthesia: a. Pre-anesthesia:
b. Post-anesthesia: a. Pre-anesthesia:
Figures 3a and 3b:
Position of eye pre- and
post retrobulbar
anesthesia, respectively.
RESULTS
•
•
•
•
•
Mean change
Standard deviation
4.20°
3.05°
Range
95% Confidence interval
0.18-10.02°
3.06-5.33°
Pre-anesthesia and post-anesthesia photos were taken
and compared in 30 eyes.
After statistical analysis, mean cyclotorsion was 4.20°
with a standard deviation of 3.05°.
The change in torsion varied from 0.18° to 10.02°.
The 95% confidence interval was 3.06-5.33°.
Data was tested with a one-sided single sample t-test at a 0.05 level
of significance, using IBM SPSS for Windows (IBM SPSS, Chicago, Ill.),
CONCLUSIONS
• After studying 30 subjects, we found that the anesthesia
effects did not move the eye greater than 15°.
Clinical significance
• Previous studies found clinically significant effects on
postoperative refraction at 15°4,5.
• Our study showed subjects had less than a 15° change,
therefore pre-anesthesia markings may not be necessary.
• Instead, the surgeon can mark the eye after anesthesia
has been administered to guide IOL placement.
• When combined with other factors that affect
torsion, the additive effects may exceed 15° leading to
poor refraction outcomes.
REFERENCES
1. Dooley I, Charalampidou S, Malik A, Ormonde G, Loughman J, Molloy
L,Beatty S. Surgically induced astigmatism after phacoemulsification with
and without correction for posture-related ocular cyclotorsion. J Cataract
Refract Surg. 2010; 36: 413-7.
2. Kraft SP, O'Reilly C, Quigley PL, Allan K, Eustis HS. Cyclotorsion in unilateral
and bilateral superior oblique paresis.J Pediatr Ophthalmol Strabismus.
1993 Nov-Dec;30(6):361-7.
3. Lynch PJ, illustrator; Jaffe CC. Yale University Center for Advanced
Instructional Media Center for Advanced Instructional Media, 1987-2000.
Accessed on September 8, 2010 at http://commons.
wikimedia.org/wiki/File:Eye_movements_abductors.jpg.
4. Novis C, Astigmatism and Toric Lenses. Current Opinion in Ophthalmology.
2000, 11:47–50.
5. Tjon-Fo-Sang, MJ, de Faber JH, Kingma C, Beekhuis WH. Cyclotorsion: A
possible cause of residual astigmatism in refractive surgery. J Cataract
Refract Surg. 28; 4:599 – 602.