Transcript Placement of Toric Intraocular Lens and the Long

Placement of Toric Intraocular Lens and
the Long-term Change in the Axis of
Corneal Astigmatism after Sutureless
Cataract Extraction by
Phacoemulsification
Maggie Hymowitz MD, Maayan Keshet MD,
Inna Ozerov MD, Marilyn Ilan ASOT,
Leslie
Shapiro MD
The authors have no financial interest to disclose
Purpose
Astigmatism is common in patients undergoing cataract
surgery. Between 15% and 29% of cataract surgery
patients have more than 1.50 diopters (D) of
preexisting astigmatism.1
Correction of corneal astigmatism is important for
improving visual outcomes following cataract surgery.
The FDA-approved, one-piece hydrophobic acrylic
toric intraocular lens (IOL), offers this option.
Accurate toric alignment is crucial for effective
refractive correction with toric IOLs.
Purpose
Recent studies have shown that the acrylic IOL is very
stable, with a mean IOL rotation of 3.35° in one study
and 3.63° in another study.2,3 Given such excellent
rotational stability in patients with pre-existing corneal
astigmatism, this lens has recently gained popularity.
In our retrospective chart review, we examined the
degree to which the axis of corneal astigmatism
changes after cataract surgery. Post-operative rotation
could have a bearing on axis calculations for the toric
IOL.
Methods
Fifty patients who underwent cataract surgery by a
single surgeon between 1998 and 2004 were identified
thorough a computer-based patient registry. The
surgeon used a 2.6 mm temporal clear corneal incision
and a two-handed phaco-emulsification technique.
The registry included the patients’ ages, surgical
techniques, and pre- and post-operative keratometry
measurements at regular time intervals from 1 day to
approximately 6 years post-operatively.
Patients with previous corneal surgery, corneal
astigmatism less than 0.75 D, complex cataract surgery,
or operative complications were excluded from the
study.
Methods
Patients with pre-operative corneal astigmatism
≥ 0.75 D and no intraoperative complications
were identified.
Corneal astigmatism was assessed using an
automated keratometer. The keratometric
cylinder values were calculated from the
measured radius of curvature.
Results
Thirty eyes were included in the study. The average
age was 75.6.
The average change in axis pre and post-operatively
(3-6 years) was 13.27°. (p=0.194)
In 13 patients (43%) the axis rotated toward the 90
degree axis. In the remaining 17 patients (57%) the
axis rotated toward the 180°.
Results
The association of axis-change with pre-operative
age was not statistically significant (r=0.14).
The association of axis-change with average
preoperative K-readings was not statistically
significant (r=0.04).
The average change in cylinder value before
cataract extraction and 3-6 years after surgery was
-0.25 D, also not significant (p=0.41).
Conclusions
Although the statistical analysis indicates that
pre- to post-operative axis change was not
significant, clinically, 13.27° of toric IOL
rotation would mean an almost 40% loss in the
astigmatic correction.4
However, the direction of axis change was
unpredictable and therefore unhelpful in preoperative planning of toric IOL placement.
References
1. Hoffer KJ. Biometry of 7,500 cataractous eyes. Am J
Ophthalmol. 1980;90:360–368.
2. Chang DF. Comparative rotational stability of single-piece
open-loop acrylic and plate-haptic silicone toric intraocular
lenses. J Cataract Refract Surg. 2008;34:1842–1847.
3. Mendicute J, Irigoyen C, Aramberri J, Ondarra A, MontésMicó R. Foldable toric intraocular lens for astigmatism
correction in cataract patients. J Cataract Refract Surg.
2008;34:601–607.
4. Viestenz A, Seitz B, Langenbucher A. Evaluating the eye's
rotational stability during standard photography: Effect on
determining the axial orientation of toric intraocular lenses. J
Cataract Refract Surg. 2005;31:557-561.