Immobility of a lens on the eye – often observed immediately on eye opening after sleep with silicone hydrogel lenses. Normal movement patterns are gradually established after eye opening so that binding is usually not observed at an aftercare visit. … Continue reading
Evaporation of the pre-lens tear film, consequently causing the lens to lose moisture to the environment. More common with higher water content and ionic lenses. May be related to dryness/discomfort symptoms reported by the patient. Pervaporation of the post-lens tear … Continue reading
Optimal lens fit includes 0.2-0.5mm primary gaze movement with good corneal coverage in all directions of gaze. Slightly loose fit (45-50%) on push-up test and no edge lift. Lens settling is uncommon and therefore initial impression is important. Also see … Continue reading
see Edge lift.
Due to the higher rigidity of the new silicone-based materials, most lenses exhibit approximately up to 0.5mm of movement in primary gaze compared with approximately 0.2mm for DSCL.
Lens tightness can be examined with the push-up test. Using a continuous scale from 0 to 100 per cent, lens tightness of 50% indicates optimal lens behavior at push-up, 100% would indicate the lens is too tight (almost impossible to … Continue reading
see Lens wear schedule.
The lens wear schedule determines how many days and nights in a row the silicone hydrogel lenses should be worn without removal. This has to be carefully developed, for each patient individually, usually during the initial aftercare visits. The range … Continue reading
Subjective assessment made after observations with the slit lamp biomicroscope. Takes into consideration the pattern in which the tears break over the contact lens, the speed of break up, the stability of the tear film, the lipid layer appearance and … Continue reading
see Lid eversion.
To assess redness and roughness of the upper palpebral conjunctiva. At every aftercare visit lids need to be everted. Instillation of fluorescein can be helpful in the assessment of palpebral roughness. With lens wear, levels of both redness and roughness … Continue reading
see Corneal neovascularization.
The limbus is the junction between the cornea and the sclera of the eye. This is a vital area because it contains stem cells that constantly differentiate to replace the surface epithelium of the cornea. Damage to the limbus will … Continue reading
A vital stain that has a similar action to rose bengal but does not sting on instillation.
Term for contact lenses or contact lens materials with Dk/t between 18 and 25 x 10-9 (cm x ml O2)/(s x ml x mmHg). Also see Dk, Dk/t, Oxygen demand and Oxygen supply.
Unit dose or multi-dose comfort drops formulated for use with contact lenses. Patients should be advised to use lubricating drops often and liberally, especially before bedtime and upon awaking.
