For Designing Custom Sphere, Toric, Multifocal, and Toric Multifocal Contact Lenses
The SpecialEyes Prescribing Nomogram is a convenient resource that enables eye-care practitioners to quickly design SpecialEyes custom soft contact lenses for patients with an average corneal diameter or horizontal visible iris diameter (HVID) of 11.6 to 12.0mm. If your patient has an HVID that is larger or smaller than average, we advise using the SpecialEyes Arc Length Calculator to design the lenses, as this will increase the probability that your first lens fitting will be successful.
How to Use the SpecialEyes Prescribing Nomogram:
Using your flattest keratometry (K) reading, locate your starting position on the horizontal axis.
From your starting position, move vertically, passing through your diameter value until you intersect the colored diagonal line representing your chosen lens material: blue for 59% hioxifilcon A material, green for 54% hioxifilcon D material, or gold for 49% hioxifilcon B material.
From the intersection with the material line, move left to the vertical axis to determine your base curve value.
Use spectacle refraction (SRx) or manifest refraction (MRx) and compensate for vertex distance.
Example: 59% hioxifilcon material and a flat K of 43.5 results in a 14.6 diameter and 8.0 base curve.