NOTE: The SRK II formula (see below) is trademarked by the authors.
Parameters:
(1) type of intraocular lens
(2) axial length of the eye in mm
(3) average keratometry reading in diopters
required power for intraocular lens in diopters =
= (constant for the IOL model) – ((constant for axial length in mm) * (axial length in mm)) – ((constant for average keratometry reading) * (average keratometry reading in diopters))
where:
• The constant for the IOL model reflects its position within the eye.
• The constant for axial length is 2.5.
• The constant for average keratometry reading is 0.9.
required power for intraocular lens in diopters =
= (constant for the IOL model) – (2.5 * (axial length in mm)) – (0.9 * (average keratometry reading in diopters))
The original SRK formula was modified (SRK II) to correct a problem arising in eyes with short (< 22 mm) or long (>= 24.5 mm) axial lengths.
|
Axial Length
|
Value for A
|
|
< 20 mm
|
(value A for IOL) + 3
|
|
20 to 20.99 mm
|
(value A for IOL) + 2
|
|
21 to 21.99 mm
|
(value A for IOL) + 1
|
|
22 to 24.49 mm
|
(value A for IOL)
|
|
>= 25.00 mm
|
(value A for IOL) – 0.5
|
