biometry immersion optical helpful tips & key points
TRANSCRIPT
9.30 am to 9.45 am Biometry Immersion/Optical
-Helpful tips & key points BOS 7-6-2015
Dr.Anand SudhalkarDr. Shubhangi Puntambekar
Mrs. Angela Macwan
Why Biometry?
Achieve “Desired “ refractive status post operatively.
“Better than before”
Common Procedures done1984…….
Keratometry
Ultrasonography
Keratometry3.2mm
Steep and Flat meridian
Axial LengthCornea to ILM
Contact and Immersion
Simple formula
SRK I: P = A - 0.9 K - 2.5 L(1) P: IOL power for emmetropia
K: corneal refractive power (K-reading)
L: axial length
A: A-constant of IOL
Areas of Refractive Surprises
Effective Lens Position
Effective Lens Position
IOL A-constant
Optimised for Biometry
Personalised by surgeon
Optical Coherence Biometry
Ultrasound v/s Optical A-Scan
Ultrasound Sound Wave 10MHz Topical Anesth,
contact probe Corneal compression Anatomical axis length
Keratometry, CCT separate
Modern formulas absent
Optical 780um light (9X
faster) Non Contact
No compression Visual – Refractive
Axial length All measurements (9)
in one go, along same axis
More measurements for 4th Generation formulas
KeratometryThe Lenstar,, measures at two zones (2.3 mm and 1.65 mm). In addition to its 32 points of measurements, each scan captures 128 points of measurements, such that five sets of readings captures 640 points of measurementsIn clinical studies this has been proven that the keratometry on the Lenstar is equivalent to the gold standard manual keratometry.
CCTRange 300 to 800u
ACDRange 1.5 to 5.5mm
Lens ThicknessRange: 0.5 to 6.5mm
Axial Length14 to 32mm,
Repeatability +- 0.035mm
