EXPORT CITATION

Chapter-10.3 Intraocular Lens Power Calculation

BOOK TITLE: Postgraduate Ophthalmology (2 Volumes)

Author
1. Bhartiya Shibal
2. Vanathi M
3. Gupta Manoj
4. Vasavada Abhay R
5. Vasavada Viraj A
6. Vasavada Vaishali A
7. Aggarwal Aashima
8. Sawhney Saurabh
ISBN
9789350252703
DOI
10.5005/jp/books/11051_39
Edition
1/e
Publishing Year
2012
Pages
16
Author Affiliations
1. Dr RP Centre for Ophthalmic Sciences, AIIMS, Ansari Nagar, New Delhi, India, Clinical Ophthalmology, Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India, Dr RP Center for Ophthalmic Sciences, AIIMS, New Delhi, India, Fortis Memorial Research Institute, Gurgaon, Haryana, India, Dr RP Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, Fortis Memorial Research Institute, Gurgaon, Haryana, India, Fortis Flt Lt Rajan Hospital, New Delhi, India, Fortis Memorial Research Institute, Gurugram, Haryana, India, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, Dr RP Centre for Ophthalmic Sciences, AIIMS, Ansari Nagar, New Delhi-110029, India, Dr RP Centre for Ophthalmic Sciences, AIIMS, Ansari Nagar New Delhi, India
2. Clinical Ophthalmology, Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, Ansari Nagar New Delhi, India, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, AIIMS, New Delhi, India, Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
3. Dr RP Centre for Ophthalmic, Science (AIIMS), Ansari Nagar, New Delhi, India, Dr RP Centre for Ophthalmic, Sciences, AIIMS, Ansari Nagar, New Delhi, India, Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India, Jaypee Hospital, Noida, Uttar Pradesh, India, Dr Rajendra Prasad Center for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India
4. Ila Devi Cataract and IOL Research Center, Raghudeep Eye Clinic, Ahmedabad, Iladevi Cataract and IOL Research Centre, Raghudeep Eye Clinic, Gurukul Road, Memnagar, Ahmedabad, India, Raghudeep Eye Hospital, Iladevi Cataract and IOL Research Center, Ahmedabad, Gujarat, India, Iladevi Cataract and IOL Research Center, Ahmedabad, Gujarat, India, Iladevi Cataract and IOL Research Centre, Raghudeep Eye Hospital, Ahmedabad, India, Iladevi Cataract and IOL Research Center, Raghudeep Eye Hospital, Ahmedabad, Gujarat, India, Raghudeep Eye Clinic and Iladevi Cataract and IOL Research Center, Ahmedabad, Gujarat, India
5. Iladevi Cataract and IOL Research Centre, Raghudeep Eye Clinic, Memnagar, Ahmedabad, India, Iladevi Cataract and IOL Research Center, Raghudeep Eye Clinic, Ahmedabad, Gujarat, India, Raghudeep Eye Clinic and Iladevi Cataract and IOL Research Center, Ahmedabad, Gujarat, India
6. Iladevi Cataract and IOL Research Center, Raghudeep Eye Clinic, Ahmedabad, Gujarat, India, Raghudeep Eye Clinic and Iladevi Cataract and IOL Research Center, Ahmedabad, Gujarat, India
7. Primus Superspeciality Hospital, New Delhi, India; Brahm Shakti Hospital and Research Centre, Budh Vihar, Delhi, India, and Insight Eye Clinic, Rajouri Garden, New Delhi, India
8. Brahm Shakti Hospital and Research Center, Budh Vihar, New Delhi, India; Insight Eye Clinic, Rajouri Garden, New Delhi, India
Chapter keywords
components of IOL power calculation, biometry, formulae, clinical variables, ultrasound velocities, different parts of the eye, silicone oil, corneal power measurement, manual keratometer, autokeratometer, corneal topography, theoretical formulae, regression formulae, postoperative refraction, patient, ocular status, keratometry, topography, posterior corneal curvatures, anterior corneal radius, toric IOLs, corneal astigmatism, surgically induced astigmatism, mathematical vector analysis, keratorefractive surgery, corneal asphericity, pre-lasik data, history derived method, refraction derived corrected keratometric value method, Aramberri double-K method, adjusted effective refractive power, R factor method, effective lens position, masket regression formula, corneal bypass method, immersion ultrasonography, laser interferometry, axial length, analysis of surgically induced astigmatism, astigmatic analysis, vector transformation, modern methodology for evaluating SIA

Abstract

The three major components of IOL power calculation are biometry, formulae, and clinical variables. The ultrasound velocities for different parts of the eye, silicone oil, as well as different IOLs are presented. Several instruments are available for corneal power measurement, such as manual keratometer, autokeratometer, corneal topography, and so on. Theoretical formulae and regression formulae are explained. The targeted postoperative refraction should be based on patient needs and ocular status. Keratometry and topography assume a normal relationship between the anterior and posterior corneal curvatures, and measure the anterior corneal radius. Toric IOLs are beneficial in the correction of regular corneal astigmatism. Surgically induced astigmatism is calculated using mathematical vector analysis. Keratorefractive surgery alters corneal asphericity and the relationship between anterior and posterior corneal curvatures. Formulas incorporating pre-lasik data are history derived method, refraction derived corrected keratometric value method, Feiz-Mannis method, Aramberri double-K method, adjusted effective refractive power, and R factor method. Corneal topography and effective lens position are discussed. Newer formulas include masket regression formula and corneal bypass method. The use of immersion ultrasonography and laser interferometry is recommended to measure axial length. Analysis of surgically induced astigmatism is described. Accurate analysis of astigmatic changes requires that the rules of vector transformation be followed. Modern methodology for evaluating SIA and calculating SIA using trigonometric functions are discussed. Aggregate data analysis, interpretation of data, and clinical applications are discussed.

© 2019 Jaypee Brothers Medical Publishers (P) LTD.   |   All Rights Reserved

Powered by MPS ScholarStor