Desìo coloured toric lenses: clinical guide and fitting protocol
Prescribing a coloured contact lens to an astigmatic patient means reconciling visual correction and aesthetic result. This guide brings together the clinical characteristics of Desìo toric lenses and the recommended fitting protocol.
What the specialist requires from a coloured toric lens
To be clinically reliable, a coloured toric contact lens must meet four requirements:
- Predictable fitting, successful at the first application
- Stability throughout the day and for the whole useful life of the lens
- Consistent comfort, from application through to replacement
- Breadth of spherical and cylindrical ranges, to cover the majority of astigmatic ametropes
Why internal toricity
Desìo toric lenses use a toric back surface (internal toricity). Compared with external toricity, this design solution offers concrete clinical advantages:
- A wide range of correctable astigmatic power, up to −3.00 D, against the maximum of around −2.00 D typical of externally toric constructions
- No axis limitations: full coverage from 10° to 180° in 10° steps
- Optimal visual acuity, thanks to the optically clean spherical front surface
- Excellent stability even with medium-to-high astigmatism
- Full respect for corneal metabolism
Fitting advantages
In practical terms, the geometry of Desìo toric lenses translates into:
- Respect for corneal metabolism, for physiological wear
- High axis stability, guaranteed by the Prism Ballast
- Excellent batch-to-batch reproducibility, both geometric and chromatic
In terms of geometric characteristics, Desìo toric lenses are comparable to traditional annual toric lenses produced by lathe cutting, with the added colour quality inherent to Cast Molding.
Pre-fitting assessment: checklist
- Keratometric or topographic measurement: the flattest corneal radius must be between 7.60 mm and 8.10 mm, compatible with the lens Base Curve of 8.70 mm
- Assessment of eyelid morphology: excessive lid tension can destabilise the prism
- Blinking characteristics: complete or partial, and the force applied
- Absence of contraindications to contact lens wear
Outside the 7.60–8.10 mm range, the lens Base Curve of 8.70 mm is not correctly matched to the cornea. This compromises both the positioning of the Prism Ballast and the aesthetic rendering of the iris colouring.
Biomicroscopic check after fitting
- 1Visual acuity with the lens fitted, monocular and binocular, compared with the refraction
- 2Centring of the lens on the corneo-scleral surface, in primary and secondary gaze positions
- 3Stability of the Prism Ballast at 6 o'clock, with rotation of less than 10° after blinking
- 4Lens dynamics: smooth movement on the corneal surface, with no adhesion
- 5Subjective comfort: absence of foreign-body sensation
Clinical notes
- Abnormal positioning of the prism compromises both visual acuity and the aesthetic effect, through decentring of the iris design.
- Pairing a spherical lens with a toric one in the same shade is possible, provided the two lenses belong to the same production batch.