2. Biometry is the process of measuring the
power of the cornea ( keratometry) and the
axial length of the eye, by using the data to
determine the ideal intraocular lens (IOL)
power.
3. Biometry essentially includes:
Measurement of axial length (AL)
Keratometry (K- reading), i.e. measurement
of corneal power and
Effective IOL position
9. Used to measure the corneal curvature
1D error results 1D error in IOL power
calculation
Types of keratometer
1. Mannual
2. Auto keratometer, keratometer
incorporated with IOL Master and Lenster
3.Topography- Placido disc based or
elevation based topography
11. Depending upon the basis of their derivation
1. THEORETICAL : these are derived
from geometrical optics
2. REGRESSION FORMULAE : Actual
postoperative refractive results of many lens
implantations are used to predict IOL power
Grouped into various GENERATIONS
12. 1st Generation
SRK I, Hoffer
2nd Generation
Binkhorst, SRK II
3rd Generation
Holladay-1, Hoffer-Q, SRK/T
4th Generation
Holladay-2, Haigis