Title : (Un)avoidable errors in biometry and some ideas how to overcome them
Abstract:
Purpose:
Murphy´s Law, postulated in 1949, stated “If anything can go wrong, it will”. This also holds true when calculating intraocular lenses (IOL) – and also here, were the options are manifold, partly systemic and pre-programmed.
Methods:
Close cooperation with the Institute of Experimental Ophthalmology, University Homburg/Saar (Germany).
Results:
Any incorrect measurement of biometry data inevitably will lead to incorrect calculations of the respective IOL, such as measurements of the axial length, anterior chamber depth and corneal curvature due to inappropriate instrument settings or outdated instrument calibrations.
Ideally, to calculate an IOL, the radii of the anterior and posterior corneal surfaces, central thickness and refractive index of the cornea, as well as the respective data from the IOL. Together with the values of the pseudophakic anterior chamber depth, the refractive index of the aqueous humor, the pseudophakic vitreous length and its refractive index, all information would be available to calculate the respective IOL individually. Since the values of the pseudophakic eye are not yet available at the time of the IOL calculation, various simplifications and model assumptions of the phakic eye are still used today.
Conclusions:
Today, optical biometry is regarded as a standard diagnostic tool in cataract surgery and represents the basis for reliable IOL calculation before cataract surgery. It has become an indispensable part of ophthalmology and has revolutionized cataract surgery.
Note: Making the best calculation and using optimized constants cannot compensate for errors in biometry. Take time to check all measurements for consistency or contradictions.
Audience Take Away:
- The audience will made aware of the major errors which might occur in biometry before cataract surgery.
- They will understand which of them they can influence and which not.
- They will understand how important personal IOL constants are and where to find them.
- Improved understand of biometry of the eye will lead to better IOL power calculation
- More exact IOL power calculation will lead to better post-OP refractive results and by this to more happy patients.
