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

HOLLADAY JT, PRAGER TC, CHANDLER TY, MUSGROVE KH, LEWIS JW, RUIZ RS: A three-part system for refining intraocular lens power calculations. J Cataract Refract Surg, 14:17-24, 1988

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