Immediate comfort
Free single-use trial lenses (Red tint)
Guarantee of fit (3 months)
Available in various materials
Delivery in 72 hours
All stages of keratoconus
Type of cone: Centered pointed, oval or extended
Cone position: centered or slightly off center
Not recommended for keratoconus with an off-center cone and pellucid marginal degeneration: opt for BioK D
2 years
Daily wear



Biok, Special Keratoconus rigid gas permeable contact lenses, having multi-curve geometry with soft junctions and a bevel zone, designed using digital technology with nanometer precision allowing the creation of very complex designs. BioK is a lens that perfectly meets the expectations of users in terms of stability, ease of fit and comfort for the wearer.


Start with :

Biomicroscopic examination
Keratometry and/or corneal topography

Choice of lens diameter (ØT)

The diameter of the first trial lens is limited to that offered in the trial box (8 to 9.60), unless you order a custom-made trial lens, in which case the choice of diameter will depend on:

Stages of keratoconus
Type of cone: :

  • Pointed center ⇒ Small ØT
  • Oval: standard ØT
  • Extended: large ØT

Location of the cone: centered or off-center: the more the cone is off-center, the greater the ØT will be.
Palpebral opening; allows us to choose the type of adaptation: Inter-palpebral or grabbed

Choice of radius of curvature (r0) 

The choice of r0 for the first trial lens depends on the corneal keratometry : r0 = K + 0.1:

K-K’< 0.3 mm to r0 = K-0.1
K-K’> 0.3 mm to r0 = K-0.2

Evaluation of fit

After fitting the trial lens, wait 30 minutes before proceeding to the fit assessment

Ideal fit
Centered lens
Apical touch
Alignment ring
Peripheral clearance band from 0.5 to 0.8 mm
Movement of 0.5 to 1 mm after blinking

A fit assessment always begins with an observation of the central zone

1 – Central zone (Static observation, lens centered)

Tight Fit

Biok légèrement (0.05) serrée au centre avec dégagements périphérique
Excessive central fluorescence
Air bubbles
Lens off-center and low
Reduced mobility

Possible solutions  : Try a flatter radius

Poor Fit

BioK plate de 0.15 à 0.2 mm
Large central contact area
Lens off-center and high
Excessive mobility

Possible solutions  : Try a tighter radius

2 – Centering and mobility

The evaluation of centering, mobility and periphery should only be done after finding the r0 which gives the best alignment in the center.

Centering (static observation)
BioK centrée

The lens must be centered, a shift lower is tolerable as long as the lens does not cross the limbus.

Lens off-center and low: choose a larger diameter of 0.3 to 0.5 mm
Lens off-center and high: choose a smaller diameter of 0.3 to 0.5 mmmm
Mobility (dynamic observation)

The lens should exhibit slight movement after blinking, with the lens moving up, then slowly refocusing.

3 – Periphery

BioK trial lenses have a standard peripheral clearance (d). Depending on observations it can be adjusted by ordering a tighter or flatter clearance.

AEL SERRE - Choisir d+
AEL TROP OUVERT - Choisir d2-
Wide clearance: (>1mm) will cause excessive lens mobility and formation of air bubbles in the periphery. Choose a tighter Edge-Lift (d-, d2-, or d3-)
Fine Clearance: (<0.5mm) will result in reduced lens mobility. Choose a flatter Edge-Lift (d+, d2+, d3+ or d4+)


Perform an over-refraction to determine the power of the final lens
Start by looking for the best visual acuity with only spherical power, then compensate in the cylinder.
If the refractive astigmatism is less than 0.75 D, it is better to disregard it, and order a spherical BioK
If the astigmatism is greater than 0.75 and the gain in acuity is significant, order an external toric lens: BioK TE.

Internal toroidal fit: BioK TI

When the corneal astigmatism exceeds 2.50 diopters, the lens is unstable and the fluorescent image is not satisfactory, in this case the best solution is to change to internal toric lens: BioK TI. 
For fit, send the Keratometry (or the topography) and the glasses correction to the lab. We will send you a definitive lens with an exchange option.


Radius of curvature  6.00 to 9.00 mm by 0.05
Diameter 9.40 to 12.00 mm by 0.1
Peripheral clearance per 0.03 mm Standard : d
Slow (tight): d-, d2-, d3-
Quick (flat: d+, d2+, d3+, d4+
Sphere +30.00 to -30.00 D by 0.25
Cyl Up to 6.00 D by 0.25
Axis 0° to 180° by 1°
Addition Up to 4.00 D by 0.25


Classification Focon III 4 Focon III 4 Focon III 5 Focon III 5
Name Roflufoco C Roflufocon D Roflufocon E Tisifilcon A
DK 65 100 125 180
Hardness 79 75 77 81
Light transmissibility 96% 97% 94% 96%
UV Filter Yes Yes Yes Yes
Tint Blue/Red Blue Blue/Gray Blue


We recommend using a care solution for rigid contact lenses without preservatives Regard K®

See Product


The adaptation guarantee is 1 month (according to the guarantee offer)