Hoffer Q

IOL Intraocular Lens Power Calculations Hoffer Q Formula Myopic Hyperopic Keratorefractive Eye Surgery Eye Cataract Surgery Eyes 2008-09-13 IOL Intraocular Lens Power Calculations Hoffer Q Formula Myopic Hyperopic Keratorefractive Eye Surgery Eye Cataract Surgery Eyes 2008-09-13 IOL calculation using the HOFFER Q formula The HOFFER Q formula was published in 1993 [HOFFER, 1993], based on the earlier work of Kenneth J. Hoffer, M.D. The HOFFER Q IOL Dr. Hoffer is Clinical Professor of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, California, USA. The author wrote and published the Hoffer Q formula. Although it is copyrighted, it may be freely used by anyone without penalty of royalties or fees of any kind. The author does not charge ultrasound manufacturers for providing the Hoffer Q formulas in their instruments. The author also provides a system of IOL power calculation using the Hoffer Q, Holladay, and SRK/T formulas with personalization which can be purchased on Casio fx-8500G calculators and on diskette for IBM in either DOS or Windows. IOL calculation using the HOFFER Q formula The HOFFER Q formula was published in 1993 [HOFFER, 1993], based on the earlier work of Kenneth J. Hoffer, M.D. (cf. references). The HOFFER Q IOL power P P = f (A, K, Rx, pACD) is a function of A : axial length K : average corneal refractive power (K-reading) Rx : refraction pACD : personalized ACD (ACD-constant) Likewise, the HOFFER Q refractive error Rx Rx = f (A, K, P, pACD) depends on A, K, P and pACD. For the calculations, the corneal radii R1C and R2C in [mm] are converted into K in [D] according to: K = 0.5 (K1 +K2) with K1 = 337.5/R1C and K2 = 337.5/R2C . The personalized ACD (pACD) is set equal to the manufacturer's ACD-constant, if the calculation was selected to be based on the ACD-constant. In case the A-constant was choosen, pACD is derived from the A-constant [HOFFER, 1998] according to [HOLLADAY et al, 1988] pACD = ACD-const = 0.58357 * A-const - 63.896 . References HOFFER KJ: Mathematics and computers in intraocular lens calculation. Am Intra-Ocular Implant Soc J, 1(1):4-5, 1975 HOFFER KJ: Intraocular lens calculation: The problem of the short eye. Ophthalmic Surg, 12:269-272, 1981 HOFFER KJ: The effect of axial length on posterior chamber lens and posterior capsule position. Current Concepts Ophthalmic Surg, 1:20-22, 1984 HOFFER KJ: The Hoffer Q formula: A comparison of theoretic and regression formulas. J Cataract Refract Surg, 19:700-712, 1993; ERRATA 20:677, 1994 HOFFER KJ: Personal communication, 1998

IOL Intraocular Lens Calculations
Prior Keratorefractive Surgery

Hoffer Q Formula.


Hoffer Q formula MYOPIC keratorefractive surgery IOL power adjustment table based on the Aramberri "double K method." The numbers in each row of refractive correction represent the amount in diopters that must be ADDED TO the calculated IOL power when using the Hoffer Q formula.

Each of the two tables listed below assume an average pre-refractive surgery corneal power of 43 D and implantation of an Alcon SA60AT intraocular lens.


MYOPIC Axial Length (mm)  
Refractive
Correction
(D)		 20 22 24 26 28 30
2 0.4 0.3 0.2 0.2 0.1 0.0  
3 0.6 0.5 0.3 0.3 0.2 0.0  
4 0.8 0.6 0.5 0.3 0.2 0.0  
5 1.0 0.8 0.6 0.4 0.3 0.0  
6 1.2 0.9 0.7 0.5 0.4 0.1  
7 1.4 1.1 0.8 0.6 0.5 0.1  
8 1.6 1.2 1.0 0.7 0.6 0.2  
9 1.7 1.3 1.1 0.8 0.7 0.2  
10 1.9 1.5 1.2 1.0 0.7 0.3  


Hoffer Q formula HYPEROPIC keratorefractive surgery IOL power adjustment table based on the Aramberri "double K method." The numbers in each row of refractive correction represent the amount in diopters that must be SUBTRACTED FROM the calculated IOL power when using the Hoffer Q formula. If no number appears, it means that the formula is not applicable for that combination of axial length and refractive correction.


HYPEROPIC Axial Length (mm)  
Refractive
Correction
(D)		 20 22 24 26 28 30  
2 0.4 0.3 0.2 0.1 0.1 0.0  
3 0.7 0.5 0.3 0.2 0.0 0.0  
4 0.9 0.6 0.4 0.2 0.0 0.0  
5 1.1 0.7 0.4 0.2 0.0 0.0  
6 1.3 0.9 0.5 0.2 0.0 0.0  


These two tables were adopted from the following:

Aramberri J. Intraocular lens power calculation after corneal refractive surgery: Double K method. J Cataract Refract Surg 2003; 29(11): 2063-2068.

Koch, D., Wang I. Calculating IOL power in eyes that have had refractive surgery. J Cataract Refract Surg 2003 29(11) 2039-2042.

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