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4.1.6 SRK SHOWA formula
1. Implanted IOL power (D)
L < 22.0 :P = A – 2.5L – 0.9K + 1.4 – 1.45REF
22.0≦L < 24.5 : P = A – 2.5L – 0.9K – 1.67REF
24.5≦L < 27.0 : P = A – 2.5L – 0.9K + 0.71 – 1.25REF
27.0≦L : P = A – 2.5L – 0.9K – 1.69REF – 1.69
2. Predicted refractive power after surgery (D)
L < 22.0 : R = (A - 2.5L – 0.9K + 1.4 – P)/1.45
22.0≦L < 24.5 : R = (A – 2.5L – 0.9K – P)/1.67
24.5≦L < 27.0 : R = (A – 2.5L – 0.9K + 0.71 – P)/1.25
27.0≦L : R = (A – 2.5L – 0.9K – 1.69 – P)/1.69
L : Axial length
K : Average corneal refractive power (D)
= (K1 + K2)/2
r : Radius of corneal curvature (mm)
= {(KI – 1) × 1000}/K
KI : Cornea equivalent refractive index
REF : Target Ref. after surgery (D)
A : A-Constant
P : Implanted IOL power (D)
3. Personal A-Constant
L < 22.0 : A = P + 2.5L + 0.9K - 1.4 + 1.45AREF
22.0≦L < 24.5 : A = P + 2.5L + 0.9K + 1.67AREF
24.5≦L < 27.0 : A = P + 2.5L + 0.9K - 0.71 + 1.25AREF
27.0≦L : A = P + 2.5L + 0.9K + 1.69AREF + 1.69
AREF : Eye refractive power after surgery (D)
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