Personalized A-Constant

Description

Returns a patient-individual a-constant (SRK/T) for a particular IOL model (ID), axial length and age, using the IBRA P1 biometry formula.

Available IOLs as of 25.06.21:
ID=32 (Alcon AcrySof SN60WF)
ID=156 (Johnson&Johnson Tecnis ZCB00)
ID=214 (ZEISS AT LISA tri 839MP)

Background
Studies have shown a significant improvement of the refractive accuracy due to lens constant optimization (general and surgeon-specific). Newer biometry formulas, e.g. Barrett Universal II, offer an additional correction to account for individual patient characteristics, mainly very short or very long eyes (AL>26mm). As part of Zubisoft's own research a correlation between age and the a-constant, and the axial length and the a-constant was found for many IOLs. The findings were integrated into a new algorithm and combined with existing a-constant optimization technologies to provide a patient-individual approach to a-constant calculation. The new biometry formula was called 'IBRA P1'. The formula is still under investigation.

URL

POST https://www.zubisoft.com/api/aconstant_pers

Permission

Standard authentication with public key, hashed private key and user key is required.

Parameters

Requests must contain an array containing the following parameters:

Name Format Example Comment
axial_length Float 26.55 The optical axial length in mm
age Integer 72 Age of the patient in years (optional, no age adjustment applied if not provided)
iol Integer 32 ID of the IOL model used (as per IBRA's devices list) 

{
    "axial_length": 26.55,
    "age": 72,
    "iol": 32
}




curl --location --request POST 'https://www.zubisoft.com/api/aconstant_pers' \
--header 'Content-Type: application/json' \
--header 'X-Public-Key: yourPublicKey' \
--header 'X-User-Key: yourUserKey' \
--header 'X-Private-Key: hashOfYourPrivateKey' \
--data-raw '{
    "axial_length": 26.55,
    "iol": 32
}'

Response

The response includes the following values:

Name Format Example Comment
personal_aconst Float 119.25 Personalized a-constants used for SRK/T
ibra_optimised_aconst Float 119.03 A-constant from IBRA reference database for given IOL model
al_adjustment Float 0.19 Adjustment provided based on axial length algorithm
age_adjustment Float 0.03 Adjustment provided based on age algorithm 

{
    "personal_aconst": 119.25
    "ibra_optimised_aconst": 119.03
    "al_adjustment": 0.19
    "age_adjustment": 0.03
}