A-Constant Optimization
Description
Returns an optimized a-constant (SRK/T) for a particular lens model from a series of treatment data (limited to 400 cases).
The resource uses 2 different mathematical models to determine the optimized a-constant.
- Model 1: The optimized a-constant is calculated for every single case. The average of all optimized a-constants is returned.
- Model 2: The optimized a-constant calculation is iterativ. The lowest refractive error (RE bottom point) for a series of cases by changing a-constants is determined. The a-constant that is leading to the bottom point is returned.
Background
The selection of the most appropriate IOL power formula including the use of an accurate lens constant are recognized being critical for delivering optimized refractive outcomes and best possible postoperative uncorrected visual acuity.
Lens constants are specific adjustment factors that improve the precision of the IOL power calculation by including the effective lens position (ELP) prediction.
The IOL material and design, the used diagnostic instrument and surgical factors may lead to variation of the lens constant.
The manufacturer recommended lens constants and constants provided by independent groups, e.g. ULIB, are the starting point for a surgeon-specific lens constant.
Surgeons are encouraged to develop their own lens constant for a given IOL to account for practice-specific variables.
Multiple studies have shown a significant improvement of the refractive accuracy due to lens constant optimization (general and personal).
The a-constant remains one of the most important lens constant for IOLs. Simple conversion equations are available to calculate one lens constant to another for a particular IOL model and biometry formula.
URL
POST https://www.zubisoft.com/api/aconstant_opti
Permission
Standard authentication with public key, hashed private key and user key is required.
Parameters
Requests must contain an array with objects with the following parameters:
| Name | Format | Example | Comment |
|---|---|---|---|
| axial_length | Float | 23.82 | The optical axial length in mm |
| k_flat_pre | Float | 42.08 | The flatter meridian (lower K-value) in D |
| k_steep_pre | Float | 45.25 | The steeper meridian (higher K-value) in D |
| iol_power_sphere | Float | 20.5 | The SE power of the IOL in D |
| manifest_sphere_post | Float | 0.75 | The postoperative manifest sphere in D |
| manifest_cylinder_post | Float | -1 | The postoperative manifest cylinder in D. Can be in plus or minus format (diopters) |
"data": [
{
"axial_length": 23.13,
"k_flat_pre": 44.7,
"k_steep_pre": 45.98,
"iol_power_sphere": 20.5,
"manifest_sphere_post": 0.75,
"manifest_cylinder_post": -1
},
{
"axial_length": 23.41,
"k_flat_pre": 43.16,
"k_steep_pre": 44.47,
"iol_power_sphere": 21.5,
"manifest_sphere_post": -1.5,
"manifest_cylinder_post": 1
}]
curl --location --request POST 'https://www.zubisoft.com/api/aconstant_opti' \
--header 'Content-Type: application/json' \
--header 'X-Public-Key: yourPublicKey' \
--header 'X-User-Key: yourUserKey' \
--header 'X-Private-Key: hashOfYourPrivateKey' \
--data-raw '{
"data": [
{
"axial_length": 23.64,
"k_flat_pre": 40.91,
"k_steep_pre": 44.82,
"iol_se_power": 22,
"manifest_sphere_post": 1,
"manifest_cylinder_post": -2
},
{
"axial_length": 27.13,
"k_flat_pre": 43.38,
"k_steep_pre": 44.58,
"iol_se_power": 10,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": -1.25
},
{
"axial_length": 24.26,
"k_flat_pre": 41.31,
"k_steep_pre": 42.72,
"iol_se_power": 21,
"manifest_sphere_post": -0.27,
"manifest_cylinder_post": -1.75
},
{
"axial_length": 23.19,
"k_flat_pre": 42.99,
"k_steep_pre": 43.95,
"iol_se_power": 22.5,
"manifest_sphere_post": 1.75,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 21.69,
"k_flat_pre": 41.12,
"k_steep_pre": 41.88,
"iol_se_power": 29,
"manifest_sphere_post": -1.5,
"manifest_cylinder_post": 0.75
},
{
"axial_length": 24.38,
"k_flat_pre": 42.72,
"k_steep_pre": 43.38,
"iol_se_power": 19.5,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 27.26,
"k_flat_pre": 43.05,
"k_steep_pre": 43.55,
"iol_se_power": 10.5,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -0.25
},
{
"axial_length": 24,
"k_flat_pre": 40.71,
"k_steep_pre": 41.82,
"iol_se_power": 23,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 1
},
{
"axial_length": 24.33,
"k_flat_pre": 44.06,
"k_steep_pre": 44.23,
"iol_se_power": 20,
"manifest_sphere_post": -1.75,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 23.87,
"k_flat_pre": 41.77,
"k_steep_pre": 43.16,
"iol_se_power": 22,
"manifest_sphere_post": -1,
"manifest_cylinder_post": 0.75
},
{
"axial_length": 26.03,
"k_flat_pre": 44.82,
"k_steep_pre": 46.11,
"iol_se_power": 11,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 1.25
},
{
"axial_length": 22.4,
"k_flat_pre": 45.61,
"k_steep_pre": 47.27,
"iol_se_power": 21.5,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 24.94,
"k_flat_pre": 41.46,
"k_steep_pre": 41.93,
"iol_se_power": 19.5,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": 0.25
},
{
"axial_length": 22.84,
"k_flat_pre": 46.3,
"k_steep_pre": 46.55,
"iol_se_power": 20,
"manifest_sphere_post": 0.5,
"manifest_cylinder_post": -1
},
{
"axial_length": 24.12,
"k_flat_pre": 41.26,
"k_steep_pre": 42.67,
"iol_se_power": 21.5,
"manifest_sphere_post": 1,
"manifest_cylinder_post": -1.25
},
{
"axial_length": 24.36,
"k_flat_pre": 44.64,
"k_steep_pre": 45.06,
"iol_se_power": 17,
"manifest_sphere_post": 0,
"manifest_cylinder_post": 0.25
},
{
"axial_length": 24.38,
"k_flat_pre": 42.61,
"k_steep_pre": 43.72,
"iol_se_power": 20.5,
"manifest_sphere_post": -1.75,
"manifest_cylinder_post": 1
},
{
"axial_length": 23.49,
"k_flat_pre": 43.79,
"k_steep_pre": 44.54,
"iol_se_power": 21,
"manifest_sphere_post": 0.5,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 23.72,
"k_flat_pre": 41.98,
"k_steep_pre": 42.83,
"iol_se_power": 24.5,
"manifest_sphere_post": -2,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 22.08,
"k_flat_pre": 44.94,
"k_steep_pre": 46.11,
"iol_se_power": 24,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 1.75
},
{
"axial_length": 23.94,
"k_flat_pre": 45.3,
"k_steep_pre": 46.11,
"iol_se_power": 18,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": 1
},
{
"axial_length": 23.37,
"k_flat_pre": 42.03,
"k_steep_pre": 42.29,
"iol_se_power": 24,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 24.07,
"k_flat_pre": 42.56,
"k_steep_pre": 43.1,
"iol_se_power": 20.5,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 1.25
},
{
"axial_length": 23.52,
"k_flat_pre": 42.03,
"k_steep_pre": 43.27,
"iol_se_power": 22.5,
"manifest_sphere_post": -1.25,
"manifest_cylinder_post": 1
},
{
"axial_length": 22.46,
"k_flat_pre": 46.49,
"k_steep_pre": 46.94,
"iol_se_power": 21,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -0.25
},
{
"axial_length": 25.1,
"k_flat_pre": 41.62,
"k_steep_pre": 42.72,
"iol_se_power": 18.5,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 23.79,
"k_flat_pre": 43.77,
"k_steep_pre": 44.18,
"iol_se_power": 20,
"manifest_sphere_post": -0.25,
"manifest_cylinder_post": -0.25
},
{
"axial_length": 20.3,
"k_flat_pre": 45.24,
"k_steep_pre": 47.54,
"iol_se_power": 30,
"manifest_sphere_post": 1.25,
"manifest_cylinder_post": 3.5
},
{
"axial_length": 23.92,
"k_flat_pre": 43.05,
"k_steep_pre": 44.18,
"iol_se_power": 20,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -1
},
{
"axial_length": 23.48,
"k_flat_pre": 42.72,
"k_steep_pre": 43.21,
"iol_se_power": 22.5,
"manifest_sphere_post": -1.5,
"manifest_cylinder_post": 1.5
},
{
"axial_length": 23.21,
"k_flat_pre": 42.99,
"k_steep_pre": 44.18,
"iol_se_power": 22.5,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 24.09,
"k_flat_pre": 40.52,
"k_steep_pre": 40.76,
"iol_se_power": 22,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 0.25
},
{
"axial_length": 25.5,
"k_flat_pre": 40.47,
"k_steep_pre": 42.24,
"iol_se_power": 18.5,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": -2
},
{
"axial_length": 23.15,
"k_flat_pre": 44.76,
"k_steep_pre": 45.92,
"iol_se_power": 20,
"manifest_sphere_post": 1,
"manifest_cylinder_post": -1.25
},
{
"axial_length": 23.53,
"k_flat_pre": 43.16,
"k_steep_pre": 43.55,
"iol_se_power": 22,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 23.77,
"k_flat_pre": 40.86,
"k_steep_pre": 41.62,
"iol_se_power": 24,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 23.84,
"k_flat_pre": 42.29,
"k_steep_pre": 43.16,
"iol_se_power": 21.5,
"manifest_sphere_post": -0.25,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 21.94,
"k_flat_pre": 43.83,
"k_steep_pre": 44.64,
"iol_se_power": 26.5,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -0.25
},
{
"axial_length": 26.09,
"k_flat_pre": 44.58,
"k_steep_pre": 45,
"iol_se_power": 11.5,
"manifest_sphere_post": 0,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 25.46,
"k_flat_pre": 42.19,
"k_steep_pre": 42.35,
"iol_se_power": 19,
"manifest_sphere_post": -1.25,
"manifest_cylinder_post": 0
},
{
"axial_length": 23.53,
"k_flat_pre": 44.12,
"k_steep_pre": 47.01,
"iol_se_power": 18.5,
"manifest_sphere_post": 1,
"manifest_cylinder_post": 1
},
{
"axial_length": 25.32,
"k_flat_pre": 43.72,
"k_steep_pre": 44.64,
"iol_se_power": 15,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 23.31,
"k_flat_pre": 45.24,
"k_steep_pre": 47.94,
"iol_se_power": 18,
"manifest_sphere_post": 0.75,
"manifest_cylinder_post": -3.25
},
{
"axial_length": 25.76,
"k_flat_pre": 45.42,
"k_steep_pre": 45.92,
"iol_se_power": 11.5,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 0.25
},
{
"axial_length": 22.95,
"k_flat_pre": 43.95,
"k_steep_pre": 45.06,
"iol_se_power": 22,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": -1.25
},
{
"axial_length": 21.8,
"k_flat_pre": 42.78,
"k_steep_pre": 44.58,
"iol_se_power": 27.5,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 25.79,
"k_flat_pre": 43.1,
"k_steep_pre": 43.6,
"iol_se_power": 14.5,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 22.39,
"k_flat_pre": 44.35,
"k_steep_pre": 44.76,
"iol_se_power": 24,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 1
},
{
"axial_length": 24.39,
"k_flat_pre": 40.81,
"k_steep_pre": 42.13,
"iol_se_power": 21.5,
"manifest_sphere_post": -2,
"manifest_cylinder_post": 2.25
},
{
"axial_length": 24.24,
"k_flat_pre": 43.72,
"k_steep_pre": 45.12,
"iol_se_power": 18,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 1
},
{
"axial_length": 23.96,
"k_flat_pre": 42.99,
"k_steep_pre": 43.21,
"iol_se_power": 20.5,
"manifest_sphere_post": 0.5,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 23.46,
"k_flat_pre": 43.05,
"k_steep_pre": 44.64,
"iol_se_power": 21.5,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 0.75
},
{
"axial_length": 24.41,
"k_flat_pre": 39.75,
"k_steep_pre": 40.61,
"iol_se_power": 19.5,
"manifest_sphere_post": 1,
"manifest_cylinder_post": 1.75
},
{
"axial_length": 24.89,
"k_flat_pre": 42.78,
"k_steep_pre": 43.05,
"iol_se_power": 18,
"manifest_sphere_post": -1,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 23.66,
"k_flat_pre": 42.35,
"k_steep_pre": 42.99,
"iol_se_power": 22,
"manifest_sphere_post": -0.25,
"manifest_cylinder_post": 0.25
},
{
"axial_length": 25.23,
"k_flat_pre": 41.41,
"k_steep_pre": 42.88,
"iol_se_power": 18,
"manifest_sphere_post": 0.75,
"manifest_cylinder_post": -1.75
},
{
"axial_length": 25.76,
"k_flat_pre": 42.4,
"k_steep_pre": 43.21,
"iol_se_power": 15.5,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": -1
},
{
"axial_length": 23.48,
"k_flat_pre": 43.27,
"k_steep_pre": 44.88,
"iol_se_power": 21,
"manifest_sphere_post": 2.25,
"manifest_cylinder_post": 1.5
},
{
"axial_length": 23.26,
"k_flat_pre": 44.82,
"k_steep_pre": 45.06,
"iol_se_power": 20.5,
"manifest_sphere_post": 0.5,
"manifest_cylinder_post": -0.25
},
{
"axial_length": 23.57,
"k_flat_pre": 42.78,
"k_steep_pre": 43.83,
"iol_se_power": 21.5,
"manifest_sphere_post": 0.5,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 23.23,
"k_flat_pre": 41.26,
"k_steep_pre": 45.42,
"iol_se_power": 23,
"manifest_sphere_post": 1.75,
"manifest_cylinder_post": -3
},
{
"axial_length": 24.79,
"k_flat_pre": 41.21,
"k_steep_pre": 42.88,
"iol_se_power": 16.5,
"manifest_sphere_post": 1,
"manifest_cylinder_post": -1.75
},
{
"axial_length": 23.43,
"k_flat_pre": 42.35,
"k_steep_pre": 43.16,
"iol_se_power": 23,
"manifest_sphere_post": -2,
"manifest_cylinder_post": 0.501
},
{
"axial_length": 23.34,
"k_flat_pre": 42.24,
"k_steep_pre": 42.56,
"iol_se_power": 23.5,
"manifest_sphere_post": 0,
"manifest_cylinder_post": 0
},
{
"axial_length": 25,
"k_flat_pre": 41.41,
"k_steep_pre": 41.67,
"iol_se_power": 19.5,
"manifest_sphere_post": -0.25,
"manifest_cylinder_post": 0.75
},
{
"axial_length": 23.92,
"k_flat_pre": 40.37,
"k_steep_pre": 41.56,
"iol_se_power": 23.5,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 25.57,
"k_flat_pre": 44.64,
"k_steep_pre": 46.11,
"iol_se_power": 12.5,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 1.5
},
{
"axial_length": 23.69,
"k_flat_pre": 42.83,
"k_steep_pre": 44.06,
"iol_se_power": 21,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 0.75
},
{
"axial_length": 22.57,
"k_flat_pre": 44.94,
"k_steep_pre": 45.49,
"iol_se_power": 22.5,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 24.76,
"k_flat_pre": 44.35,
"k_steep_pre": 45.67,
"iol_se_power": 15.5,
"manifest_sphere_post": 0.75,
"manifest_cylinder_post": -1.25
},
{
"axial_length": 21.81,
"k_flat_pre": 45.49,
"k_steep_pre": 46.3,
"iol_se_power": 24.5,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 1
},
{
"axial_length": 24.24,
"k_flat_pre": 42.83,
"k_steep_pre": 44.64,
"iol_se_power": 19,
"manifest_sphere_post": -1,
"manifest_cylinder_post": 1
},
{
"axial_length": 23.16,
"k_flat_pre": 43.32,
"k_steep_pre": 44.12,
"iol_se_power": 22.5,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 22.45,
"k_flat_pre": 43.21,
"k_steep_pre": 44.18,
"iol_se_power": 25,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 22.9,
"k_flat_pre": 45.67,
"k_steep_pre": 46.49,
"iol_se_power": 20,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": 1.25
},
{
"axial_length": 23.92,
"k_flat_pre": 40.37,
"k_steep_pre": 41.56,
"iol_se_power": 23.5,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 24.67,
"k_flat_pre": 44.41,
"k_steep_pre": 45.67,
"iol_se_power": 15.5,
"manifest_sphere_post": -0.75,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 23.86,
"k_flat_pre": 45.06,
"k_steep_pre": 46.17,
"iol_se_power": 17.5,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 0.75
},
{
"axial_length": 23.54,
"k_flat_pre": 43.72,
"k_steep_pre": 43.95,
"iol_se_power": 21,
"manifest_sphere_post": 0.5,
"manifest_cylinder_post": -1
},
{
"axial_length": 23.61,
"k_flat_pre": 40.81,
"k_steep_pre": 42.24,
"iol_se_power": 24,
"manifest_sphere_post": -1.25,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 26.75,
"k_flat_pre": 39.11,
"k_steep_pre": 39.89,
"iol_se_power": 17,
"manifest_sphere_post": -0.25,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 22.82,
"k_flat_pre": 43.95,
"k_steep_pre": 45.67,
"iol_se_power": 22.5,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 22.64,
"k_flat_pre": 43.72,
"k_steep_pre": 47.01,
"iol_se_power": 22.5,
"manifest_sphere_post": -1.25,
"manifest_cylinder_post": 1.25
},
{
"axial_length": 24.26,
"k_flat_pre": 42.67,
"k_steep_pre": 42.67,
"iol_se_power": 20.5,
"manifest_sphere_post": 0,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 24.28,
"k_flat_pre": 44.29,
"k_steep_pre": 44.76,
"iol_se_power": 17.5,
"manifest_sphere_post": -0.5,
"manifest_cylinder_post": 0.5
},
{
"axial_length": 23.32,
"k_flat_pre": 44.76,
"k_steep_pre": 45.92,
"iol_se_power": 20,
"manifest_sphere_post": -0.25,
"manifest_cylinder_post": -0.75
},
{
"axial_length": 23.96,
"k_flat_pre": 43.06,
"k_steep_pre": 44.23,
"iol_se_power": 20,
"manifest_sphere_post": 0.75,
"manifest_cylinder_post": -0.5
},
{
"axial_length": 23.71,
"k_flat_pre": 43.6,
"k_steep_pre": 44.12,
"iol_se_power": 20.5,
"manifest_sphere_post": 0.25,
"manifest_cylinder_post": -0.5
}
]
}'
Response
The response includes the following values
| Name | Format | Example | Comment |
|---|---|---|---|
| aconstant_model1 | Float | 118.98 | A-constant calculated with Model 1 (case-by-case) |
| aconstant_model2 | Float | 118.96 | A-constant calculated with Model 2 (iterativ) |
{
"aconstant_model1": 118.98,
"aconstant_model2": 118.96
}