Partial coherence interferometry: a novel approach to biometry in cataract surgery.
OBJECTIVE
To compare biometry performed by an enhanced version of dual beam partial coherence interferometry and applanation ultrasound in a prospective study of 85 cataract eyes to improve refractive outcome of cataract surgery due to a more accurate calculation of intraocular lens power.


METHODS
The SRK II formula using ultrasound biometry data was employed. Three months after surgery, partial coherence interferometry biometry was repeated and refractive outcome was determined. Preoperative partial coherence interferometry biometry data were used to determine the refractive power of the intraocular lenses retrospectively and to calculate the possible refractive outcome.


RESULTS
Precision of partial coherence interferometry biometry was more than 10 times better than that of ultrasound. Therefore, the possible mean absolute error for postoperative refraction achieved with partial coherence interferometry biometry was 0.49 diopters (compared with 0.67 diopters with ultrasound biometry), resulting in an improvement of 27%. Axial eye length measured with the two techniques differed by a mean of 460 microm. The difference in lens thickness measured with partial coherence interferometry and ultrasound significantly correlated with cataract grade. A mean shortening of 120 microm of axial eye length following cataract surgery was also detected by partial coherence interferometry.


CONCLUSIONS
The enhanced version of partial coherence interferometry offers biometry with unprecedented precision (<10 microm) and resolution (approximately 12 microm), therefore improving the refractive outcome in cataract surgery. This noninvasive technique provides a high degree of comfort for the patient, with no need for local anesthesia or pupil dilation and minimized risk of corneal infection.
Institut für Medizinische Physik, Universität Wien, Vienna, Austria. Wolfgang.Drexler@univie.ac.at
W
W
Drexler
O
O
Findl
R
R
Menapace
G
G
Rainer
C
C
Vass
C K
CK
Hitzenberger
A F
AF
Fercher
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000869:Anterior Eye Segment / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D001699:Biometry / Q000379:methods*; D002387:Cataract Extraction; D005123:Eye / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D006801:Humans; D007368:Interferometry / Q000295:instrumentation / Q000379:methods*; D007910:Lenses, Intraocular; D008027:Light; D008875:Middle Aged; D055095:Optics and Photonics; D012029:Refraction, Ocular / Q000502:physiology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014463:Ultrasonography