Tutorial

New 3C Calculator!
The home page provides the calculation for the right eye, for the left eye and the possibility of quickly inserting the date of the calculation, the name of the surgeon and the patient.

There is the possibility to select the type of biometrics performed: interferometry, ecobiometry or SOS biometry. Consequently, correction factors of the axial length will be activated.

There is the possibility to select the keratometric index used by the instrument. It was set at 1.3375, according to European standards.

The calculator provides the possibility of performing three types of calculation: calculation for virgin eyes, calculation for eyes after refractive surgery, calculation for secondary piggyback implant for pseudophakic eyes.
All calculations provide for the possibility of carrying out the calculation for both spherical and toric lenses.

The feature of this computing platform; compared to the previous versions, it is the presence of a new formula, which provides a better accuracy of the prediction of the postoperative error, in particular in the long eyes. In fact, a polynomial optimization of the length has been developed which also provides for an improvement of the ELP estimate and therefore of the calculated lens power. Another feature is that, in the absence of measurement of the lens, the calculator can estimate it, obviating this unknown and the formula can be used.
However, we recommend entering the LT value if measured.

The calculator also provides the possibility of carrying out the calculation with several lenses at the same time. If the surgeon also needs to make the calculation for sulcus implantation.

Regarding the calculation for toric lenses, the calculator requires keratometry. Optional data are: the SIA and posterior (negative) astigmatism measured by a tomograph. Thus, any slots that are grayed out are optional.

In this case, the calculation can be performed in two different ways: either by entering the posterior corneal astigmatism, or by not entering the posterior astigmatism. In the second case, the calculator will carry out the calculation based on keratometric astigmatism only, with the relative consequences.
The rest of the compilation is the same as the calculation for virgin eyes.
The calculator provides a graphical representation of the IOL implant axis, keratometry axis, and main incision axis.

The calculation after refractive surgery provides for the possibility of selecting the type of previous refractive surgery: post Laser (PRK, LASEK, LASIK, SMILE) and post radial keratotomies.
In particular, the formula after radial keratotomies for estimating corneal power is completely new.
The big news is that the calculation in this case can be done in any situation. Both knowing the patient's medical history and not knowing the patient's medical history.
Information buttons are provided to help the less expert operator guide the calculation and explain the logic of the calculator.
The calculation can be performed even without knowing the patient's pre-operative data. Furthermore, there are various options that allow the calculation after refractive surgery, knowing the pre-operative data according to an order of priority. For example, after laser it is possible to enter or the SIRC value directly (which the operator thinks he knows), or the curvature before refractive surgery, or the curvature of the posterior surface measured with a tomograph. It is therefore possible to calculate the anterior preoperative curvature with a good approximation and therefore to estimate the SIRC automatically.

If the operator does not fill in the optional gray fields dedicated to the calculation after refractive surgery, the SIRC calculation will still be performed, using polynomial regression formulas, which take into consideration the inserted biometric parameters.
Therefore, the calculation is possible without knowing the patient's clinical history, both as regards the eyes after laser refractive surgery and as regards the eyes after radial keratotomies.

If the surgeon enters all the optional data for the calculation of the SIRC, the calculator will automatically process the data entered according to an order of priority.
In this case all data has been entered, but the SIRC has been obtained based on the back surface only.
All these decision algorithms within the computer are explained via information windows.

The calculation of toric lenses after refractive surgery is very similar to that for virgin eyes. In these eyes, the relationship between anterior and posterior surface astigmatism is impaired. Consequently, it is mandatory to calculate the total corneal astigmatism by directly entering the posterior corneal astigmatism measured with a tomograph.

The calculator provides for the calculation for secondary piggyback implants in eyes that have already undergone phacoemulsification surgery, both for spherical and toric lenses.
The formula is in principle a vergence formula using the fictitious refractive index according to the Camellin-Calossi formula.
In this case, accurate measurement with a tomograph of the distance between the corneal apex and the anterior plane of the previously implanted lens is required. It is possible to carry out this calculation in all situations: in virgin eyes, after laser refractive surgery and after radial keratotomies.
You can select the distance between the eyeglass lens plane and the corneal plane. This distance is the one that was used to measure the refraction after cataract surgery. Hence, the actual refraction. Generally, the average distance is 12 mm.

Finally, the operator inserts the patient's sphere and refractive cylinder.

The calculation for piggyback toric lenses for secondary implants is based on the same principle. Added to this is the need to know the axis of the patient's refractive astigmatism.