Transcript Document

INTRAOCULAR LENS POWER
CALCULATION BY IMMERSION A-SCAN
BIOMETRY VERSUS CONTACT A-SCAN
BIOMETRY MEASUREMENTS BEFORE
CATARACT SURGERY
Burak Bilgin**, M.D., Kadir Eltutar*, M.D., N. Demet
Ozcelik*, M.D.
*: Istanbul Education and Research Hospital
Opthalmology Department, Turkiye.
**: Almangoz Eye Center, Nisantasi, Istanbul,
Turkiye.
The authors state that they have no proprietary interest and they have not
received any grants or funds in support of the study.
PURPOSE :

The study was designed to evaluate the
difference in contact A - scan biometry
versus immersion A - scan biometry
measurements for intraocular lens (IOL)
power calculations before cataract surgery.
.
METHODS :
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Foldable acrylic hydrophobic IOLs ( AcrySof SA60AT,
SN60WF, SA30AT, SN60AT ) were implanted.
Axial length (AxL) measured by contact A - scan and
immersion biometry were compared.
The estimated refraction ( -0,50 Diopters ) was
compared with postoperative refraction achieved on the
days 1, 7,15 and 30.
Highly myopic eyes with posterior staphyloma were
excluded from the study to avoid the miscalculation of
IOL power.
RESULTS :

Immersion A-scan measured longer axial
length than contact A-scan biometry
( p < 0,05 ).
RESULTS:

Compared to contact A-Scan biometry,
estimated refraction measurements with
immersion A-Scan biometry were closer to
refraction achieved postoperatively.
SE: Spherical Equivalent
RESULTS:

Lens power prediction error for the contact A-scan group
was 0,93 ± 0,67 D at the visit on day 30, and 0,47 ±
0,46 for the immersion A-scan group respectively. The
difference was statistically significant (p<0,05 ).
SE: Spherical Equivalent
CONCLUSIONS:
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IOL power calculation to achieve postoperative
emmetropia, is an important factor in
phacoemulsification surgery.
Our results show that; lens power prediction error with
immersion A-Scan biometry is lower compared to contact
A-Scan biometry ( p < 0,05 ).
Immersion biometry gives longer axial length
measurements compared to contact A-Scan biometry
( p < 0,05 ).
Choosing the appropriate formula for IOL power
calculation according to axial length measured by
ultrasound biometry plays a major role for achieving
emmetropia after uncomplicated phacoemulsification
surgery.