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  IOL Power Calculations
How to Achieve Accurate Results
IOL Power Calculations
 
IOL Power Calculations Cataract Surgery Arizona
Alcon AcrySof Toric IOL Cataract Surgery Arizona
A-scan Biometry Cataract Surgery Arizona
Bag vs. Sulcus
Corneal Transplantation
Effective Lens Position Cataract Surgery Arizona
Haigis Formula
High-Extreme Axial Myopia
IOL Calculation Formulas
Limbal Relaxing Incisions
Outcomes Database
Polypseudophakia
Polypseudophakia Calculations
Post Keratorefractive Surgery Cataract Surgery Arizona
Pseudophakia
Pseudophakic CFs
Refractive Vergence Formula
Silicone Oil
Staphyloma
Validation Guidelines
Optical Biometry Optical Biometry
SIA Calculator
Disclaimer
Physician Downloads SIA Calculator
Links
References
Special Thanks

Intraocular Lens Power Calculations.

Over the last decade, IOL power calculations have become a focal point of cataract surgery. In 1977, the state-of-the-art for estimating IOL power for emmetropia was to simply add +19.0 D to the pre-cataractous refraction. A decade later, being within ±1.00 D of the target refraction was still considered a reasonable standard. The standard for accuracy for normal eyes was more recently addressed in the United Kingdom in the 2006 study: "Benchmark standards for refractive outcomes after NHS cataract surgery." The authors concluded that the "benchmark" standard for refractive outcomes for normal eyes after cataract surgery should be within ±0.50 D for 55% of cases and within ±1.00 D for 85% of cases.1

Today, by carefully optimizing the individual component parts of IOL power calculations, combined with advanced surgical techniques, it is possible to be within ±0.50 D for better than 70 percent of surgeries and ±1.00 D for better than 90% of surgeries.2 By tracking your outcomes, you can see where you are in relation to this published "benchmark" standard.

Cataract Surgery Arizona
Surgically-induced Astigmatism Calculator

Surgically-induced Astigmatism Calculator

Now there is no need to delve into mathematics. The SIA Calculator removes the task of drawing vectors or looking up sines, cosines and their relatives. Just push a few keystrokes and the job is accurately and speedily done. Read more...
Surgically-induced Astigmatism Calculator (SIA Calculator)

Surgically-induced Astigmatism Calculator
Haigis Formula Optimization

Haigis Formula Optimization

Rather than simply move a fixed formula-specific IOL power prediction curve up (more IOL power recommended) or down (less IOL power recommended), the Haigis formula instead uses three constants. Read more...
Haigis Formula Optimization Spreadsheet

Haigis Formula Optimization Spreadsheet
4-IOL Constants

Optical Biometry Lens Constants

Because there is no corneal contact, optical biometry lens constants will always be higher than those optimized for applanation A-scans in which there is a variable amount of corneal compression. Read more...
Optical Biometry Lens Constants

Optical Biometry

Precise biometry is essential for accurate outcomes in cataract and refractive surgeries. The measurement of axial length by ultrasound was the gold standard for many years.


LenStar Tutorials


IOLMaster Tutorials


Precise biometry is essential for accurate outcomes in cataract and refractive surgeries. The measurement of axial length by ultrasound was the gold standard for many years. Read more...

IOLMaster
Keratometer Measurement
IOL Power Formulas

IOL Power Formulas

If you have not done so already, now is the time to incorporate one of the newer theoretic IOL formulas. Follow this link for comparisons of the various IOL power formulas in current use: IOL Power Formulas

IOL Power Formulas
A-scan Biometry

A-scan Biometry

A-Scan Biometry using ultrasound, an important and sometimes challenging preoperative measurement, can be carried out in several ways. In this section, we will compare the advantages of the immersion technique over applanation, and how to improve accuracy.
A-Scan Biometry Using Ultrasound

A-scan Biometry
IOL Power after LASIK, PRK, RK

IOL Power after LASIK, PRK, RK

Prior keratorefractive surgery will make direct measurements for corneal power problematic. Learn how to to estimate the true corneal power following RK, PRK, and LASIK. IOL Power after LASIK, PRK, RK

IOL Power after LASIK, PRK, RK
Cataract Surgery Arizona

  Dr. Hill volunteers his time and resources to make the information on this website available to you. If you would care to donate towards the operating expenses, or just to say thank you, we welcome your contribution.

Cataract Surgery Arizona
 

A-Scan Ultrasound Biometry

A-scan biometry by immersion has better reproducibility, which leads to an overall increase in accuracy. However, all forms of ultrasound based biometry have limitations. Follow the links below for advanced A-Scan biometry techniques to improve your axial length measurements.

A-scan Biometry
Biometry Explained
A-scan Setting
Applanation A-scan
Immersion A-scan
Immersion Vector A/B-scan

Prior Keratorefractive Surgery

Prior keratorefractive surgery will make direct measurements for corneal power problematic. Follow these links to learn how to to estimate the true corneal power following RK, PRK, and LASIK.

Myopic LASIK
Hyperopic LASIK
Radial Keratotomy
Double K Formula Corrections
Hoffer Q Formula
Holladay 1 Formula
SRK/T Formula

ASCRS Post Keratorefractive Calculator

Effective Lens Position (ELPo)
(Anterior Chamber Depth)

Determining the Effective Lens Position (ELPo) for each IOL and each surgeon is an effective way to reduce the prediction error to a minimum. The ELPo allows you to calculate the optimal or "personalized" lens position based on your individual experience with any style lens averaged ideally from at least 20 to 30 cases.

Effective Lens Position (ELPo)
ELP Spreadsheet

Post Myopic LASIK

The following links contain descriptions of several popular IOL power calculation methods as they relate to the various ablative forms of keratorefractive surgery for myopia, such as LASIK and PRK.

Clinical History Method
Contact Lens Method
Corneal Bypass Method
Feiz-Mannis Method
Haigis-L Formula
Latkany Method
Masket Method
Wang Koch Maloney Method
Modified Masket Method
Topographic Central Power
 

Special Thanks
Many deserve our special thanks for graciously offering their guidance and suggestions.

 

To know more about these topics, see: References for some references of the material presented above.

1. Gale RP, Saldana M, Johnston RL, Zuberbuhler B, McKibbin M. Benchmark standards for refractive outcomes after NHS cataract surgery. Published on-line in Eye, 24 August 2007.

2. Brändle J in Haigis W: IOL calculation in long and short eyes. In Mastering the Techniques of IOL Power Calculations. Hoyos GA, Dementiev JE (eds), Jaypee Brothers Medical Publishers (P) Ltd., New Delhi, 2005


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Intraocular Lens Power Calculations


East Valley Ophthalmology, Arizona's premier eye specialists, provides this on-line information for educational and communication purposes only and it should not be construed as personal medical advice. Information published on this website is not intended to replace, supplant, or augment a consultation with an eye care professional regarding the viewer/user's own medical care. East Valley Ophthalmology's disclaims any and all liability for injury or other damages that could result from use of the information obtained from this site. Please read our full Disclaimer