OUTLIERS

Outliers and 9 groups of eyes with typical biometry

All current formulas give good results in eyes with usual biometry. The problem is about 20 percent of eyes that are outliers. 


Outliers are eyes:

  • extra short or long eyes
  • extra steep or flat eyes
  • with extra large or small lens
  • with vitreous volume enlargement
  • after LASIK or other refractive surgery
  • after vitrectomy
  • after glaucoma surgery
  • after scleral buckle surgery


Biometric outliers are eyes, where any of the biometric parameters is approximatelly outside +/- 2 SD (standard deviations) of the average values


Outliers are eyes: 

Extra long (XL with AL>26mm)   

Extra short (XS with AL<21mm)   

Extra Steep (XE with K>46mm)   

Extra flat (XF with K<41mm)

(The letter X stands for extra-) 


“Normal” AL and K eyes categories are approximately within +/- 1 SD (standard deviation), typical eyes are approximately within +/- 2 SD and eyes outside 2 SD are “outliers”.  


Within Outliers many other unusual combinations can theoretically exist 

as for example:   

XL-F: Very long flat eye   

XS-F: Short very flat eye


Combinations increase further as more than one parameter is outside 2 SD .


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