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Chapter-09 Biometry

BOOK TITLE: Small Incision Cataract Surgery (Manual Phaco)

Author
1. Swarup D
2. Suman Santosh
ISBN
9788184489804
DOI
10.5005/jp/books/11358_9
Edition
2/e
Publishing Year
2010
Pages
7
Author Affiliations
1. State Institute of Ophthalmology, Allahabad, India
2. Regional Institute of Ophthalmology, MLN Medical College, Allahabad, India
Chapter keywords

Abstract

Estimation of power of IOL implant is known as Biometry. It is done individually in every patient to get best visual outcome after surgery. IOL power calculation is done by 2 methods. First is based upon primary refraction, second based upon accurate measurement of different parameters such as axial length and corneal curvature. SRK formulae has wide acceptance. It shows that variation of axial length of 1mm results in 2.5 D change in IOL power. SRK formula needs adjustment to SRK-II for very long (> 24.5 mm) and very short (< 22 mm) eye ball. Orientation of optics of implant and surgeon\'s personal a constant is also important for correct IOL power estimation. A round and centered capsulorhexis maximizes the accuracy of refractive out come after cataract surgery, in the cases of in the bag IOL placement. For patients who have had refractive surgeries, clinical history method or hard contact lens method or an average of the two is most common.

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