Formulae for biometry
Axial length (mm) Formula 
<22mm  Hoffer Q
22-24.5mm Average of Hoffer Q, Holladay and SRK/T
24.6-26mm Holladay
>26mm  SRK/T
1. Fledelius HC. Refraction and eye size in the elderly. Acta Ophthalmol 1966;6: 241-248. 

2. Hoffer K J. Biometry of 7500 cataractous eyes. Am J Ophthalmol 1980; 90: 360 - 368. 

3. Sanders DR, Retzlaff JA, Kraff MC et al. Comparison of the SRK/T formula and other theoretical and regression formulae. J Cat Refract Surg 1990;16:341-346. 

4. Hoffer K J. The Hoffer Q Formula: A comparison of theoretic and regression formulas. J Cataract Refract Surg 1993; 19: 700-712. 

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