Tomey OA-2000 - SRK SHOWA Formula

4-7 ■
β : P [na・r + L1 (nc – 1)
+ 0.001AREF {L1・r + V・L1 (1 – nc) - na・V・r }]
r : na [1000X – P・L1・r + AREF
{0.001P・V・L1・r – (V・X + L1・r)}]
AREF : Refractive power of eye after surgery (D)
4.1.5 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)