Aconstant conversion from Optical Biometry to immersion or contact based biometry

Aconstant dilemna when you have the optical Aconstant of lens only and you have to do a US for this patient

1. What would be the aconstant for contact or immersion based biometry

2. What would be the aconstant for manual or auto based keratometry

Aconstant conversion from optical to contact or immersion based ultrasound biometry taking into consideration keratometry device
Aconstant conversion from optical biometry constant to contact or immersion