Cooke-modified axial length (CMAL)

Before you use the Cooke modified axial length, here are a quick review of facts :

  • You may have bought that expensive optical biometry machine, but that does not guarantee you accurate results. Why ?

  • Most optical biometry machines utilize composite or group refractive indices, that is they apply one R.I for the whole eye. This may be good for normal axial lenght eyes, but may create hyperopic outcome for longer axial lengths and myopic outcome for short axial lengths.

  • Some studies indicate segmented R.I consideration, that is, consideration of each eye anatomical feature refractive index as more beneficial.

  • However, not many optical biometry machines use the segmented approach while converting signals to axial length.

  • The CMAL approach is a nomogram developed by David Cooke which closely approximates sum of segment AL and can be applied to all types of axial length.

  • Addtionally the Wang & Koch nomogram has been also provided for high axial length patients. Input high axial length data of patients from optical biometry only.


  • Here is the calculator :






Sources :1. Approximating sum of segments axial length from a traditional optical low coherencereflectometry measurement; David L Cooke, Timothy L Cooke; JCRS 2019; 45; 351-3542. 2. Modified axial length adjustment formulas in long eyes - correspondence Li Wang, DouglasKoch; JCRS Nov, 2018. 3.Effects on IOL Power Calculation and Expected Clinical Outcomes of Axial Length Measurements Based on Multiple vs Single Refractive Indices; Shammas et al; Clinical Ophthalmology 2020:14 1511–1519.





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