In the central ectasias and in the most evident forms, the effectiveness of the compensation is determined by the formation of the lacrimal meniscus between the cornea and the lens. In the soft, this element is obtained through a weighted increase of the central thickness (CT), which increases the resistance to the bending of the hydrophilic polymer. The fitting protocol of SP-K is suitable in the most evolved cases of Keratoconus (KC), when the visual recovery is most affected by higher order aberrations (vertical coma).
production characteristics
Recommended polymers: to ensure minimum hypoxic stress, SP-K are produced in Si-Hydrogel (hydrogel materials 54,59,68% H2O upon request).
patient selection
Ectasie of intermediate grade, in the cases of corneal (R)GP discomfort, difficult scleral management and morphology not suitable for hybrids.
refractive selection criteria
- BCVA < 20/40 (visual recovery obtained with the best spherical-cylindrical ophthalmic correction).
- Poor visual quality, conditioned by aberration residues (HOA) and the perception of ghost images, halos and splits.
- Corneal topography: ectasias with central apex and evolution of medium-evolved grade.
fitting procedures
- Select the SP-K model (1,2,3) according to the stage of KC in topography; take the closest BC to the Flat K value in the SIM-K.
- After 30′ from the insertion, evaluate the movement and the ratio of coverage (TD vs HVID); if the fit is flat modify the sagittal by intervening on the peripheral Skirt of alignment (step ±1).
- Check the rotation of marks and perform subjective over-refraction (sphere-cylinder-axis).
- At the removal, verify the effects of mechanical interaction (topography) and physiological response in slit lamp (biomicroscopy).
final lens order
Indicate any changes in parameters (BC, TD) and polymer (%H2O). Consider the over-refraction and ask, in case of residual astigmatism, the new lens with module Front Toric (FT).
Due to the high water content of the material, frequent replacement is suggested.
