Description
BioSafty, mini-scleral lens with an innovative and totally customizable design. Specially designed to meet the expectations of professionals and give them control to achieve the ideal fit, it is the best choice for irregular corneas, or simple ametropia. The lens passes over the cornea and the limbus to rest on the sclera, offering the wearer great comfort. The BioSafty is available in latest generation materials with the highest DK in the world offering great stability.
Adaptation
BioSafty Design
Geometry of the BioSafty is multi-aspherical, with a design that adapts to all sagittal heights and different corneal diameters, created with 4 adjustable zones:
Each of these zones can be adjusted in steps of 50 µm, making it possible to best optimize the fit.
Choice of the first trial lens
The diameter
Three parameters are involved in the choice of the diameter of the first trial lens: scleral toricity, palpebral opening and corneal diameter ØC
- For ØC < 11.8 choose the 15.10
- For 11.8> ØC choose the 16.30
For a small inter-palpebral opening opt for the small diameter (15.10) to facilitate handling.
For better stability and better centering, opt for the small diameter (15.10), this avoids the interaction of the periphery of the lens with the sclera
Deflection
Three options for choosing the trial lens deflection
Evaluation of fit
Criteria for a good fit :
After inserting the lens, the evaluation goes through:
1 – Observation of fluorescence
Immediately after fitting the trial lens, proceed with observation using a slit lamp. In blue light it must be uniform with absence of air bubbles. In the event of the presence of these, immediately remove the lens and put it back after filling it with saline solution.
The lens must pass over the cornea and the limbus; the lens must not be in contact with the cornea. In case of contact remove the lens and replace with another with a larger deflection.
2 – Diameter of the lens / corneal diameter
The edge of the lens must be at least 1.5 mm from the limbus.
If a pinguecula is present, check its location relative to the edge of the lens. A change in diameter can avoid contact between the pinguecula and the lens.
3 – Evaluate the thickness of the clearance in the center (C)
With LAF in white light and narrow slit between 45° and 60°, evaluate the clearance in the center or the clearance by comparing it with the thickness of the lens or that of the cornea (clearance = lens thickness or 2/3 of the thickness cornea).
The objective is to have a clearance in the center between 250 and 350 µm.
4 – Assess the paracentral (P) and limbic (L) clearances
Zone Paracentrale (P)
Paracentral Zone (P): In the event of DMP, trauma or post-graft, insufficient or excessive clearance may be observed at the peripheral cornea, which requires an adjustment of the sagittal height in this zone. Order a lens with P+1, P+2, P+3, P-1 or P-2 (each step corresponds to 50 µm). This is only a change of deflection at the level of this zone without inducing a change in the sagittal height of the lens.
Zone limbique (L)
Limbic zone (L): The support must be only on the sclera, avoiding any contact with the limbus, and fluorescence must be present over 360°. If the limbal clearance is insufficient order a lens with L+1, L+2, L+3 where each step corresponds to a change in limbal deflection of 50 µm.
A large limbal clearance is undesirable; it can be reduced by ordering a lens with L -1, L -2 by 50 µm.
5 – Check scleral support in all positions (after wearing for at least 1 hour)
The scleral zone (S) must be aligned over 360° with the sclera. This observation should be done after a minimum of 1 hour of wear.
If the lens is too tight it will cause compression of the vessels and/or wrinkling of the conjunctiva. Order a lens with a more open clearance from S+1 to S+12 in steps of 25µm.
If too flat, the SZ will cause discomfort, hyperemia, edema and formation of air bubbles. Order the final lens with a more closed edge-lift from SZ-1 to S -12, in 25 µm steps.
Peripheral toric scleral lens
The greater the DT, the greater the interaction with scleral asymmetry.
Consider reducing the diameter of the lens first.
Opt for a peripheral toric lens (BioSafty TP) if:
Advantage of a TP
Order a BioSafty TP (peripheral toric) or a BioSafty TPO (Adjusted by quadrant)
Over-refraction
After a complete and satisfactory fit evaluation, over-refraction is performed to determine the power of the final lens. If the deflection of the final lens is different from the trial lens, recalculate the power of the final lens taking into account the change in the base radius and applying the rule 0.1 mm →0.50 D
The Biolens laboratory can do these calculations for you if you send the reference of the trial lens, the adjustments and the over-refraction..
Look for the best visual acuity in spherical only. If the VA is unsatisfactory, correct the astigmatism:
External Toric
Toric scleral lenses have engravings on their surface, to allow for checking the rotation of the axis of astigmatism. Two lines at 3:00 a.m. and 9:00 a.m.
In case of rotation a recalculation of the axis of astigmatism will be necessary.
