A free app offering a number of features: a digital version of the Efron Grading Scales, easy-to-use multifocal and toric calculators and oxygen profiles displaying the
oxygen transmissibility relevant to a selected contact lens design and prescription:
DAILIES TOTAL1 contact lenses are specifically designed to address contact lens discomfort - they have the highest surface lubricity (or smoothness) and the highest breathability (or
oxygen transmissibility) of any leading daily disposable contact lens,3 delivering exceptional comfort that lasts all day.
The family of contact lenses features polyvinylpyrrolidone (PVP) for enhanced wettability, a high
oxygen transmissibility level (Dk/t) and a low modulus.
In conventional hydrogel lenses, oxygen is dissolved in water and transported through the materials to the cornea; therefore, the water content of lens materials is a key factor in
oxygen transmissibility [31].
The high
oxygen transmissibility allows up to five times more oxygen through the lens than traditional soft contact lenses, for white healthy looking eyes," Dr Mahmoud highlighted.
With an
oxygen transmissibility level of 175, Focus NIGHT&DAY extended wear lenses transmit the industry's highest amount of oxygen to the eye's cornea.
Current scleral lenses are twice as thick as conventional GP lenses with a subsequent impact upon
oxygen transmissibility; these lenses facilitate a deeper liquid lens with entire corneal coverage, added to which there is virtually no tear pump mechanism to replenish the tear layer.
For lathe manufactured soft and rigid lenses, practitioners need to decide on which contact lens material is most suitable for any given patient with regard to
oxygen transmissibility and water content.
The contact lens
oxygen transmissibility (Dk/t) required for no contact lens induced corneal oedema in open-eye and closed-eye conditions is estimated at 35 x [10.sup.-9] and 125 x [10.sup.-9] respectively.
Contact lenses made up of materials with a known Dk, may then have their
oxygen transmissibility calculated, by dividing the oxygen permeability by the thickness of each lens, providing us with Dk/t (units of x [10.sup.-9] (cm mL [O.sub.2])/(mL sec mmHg)).
The combination produces a lens with reasonably high
oxygen transmissibility (Dk/t approximately 100), good wettability and resistant to proteins, but very flexible.
DAVID THOMAS Contact Lenses/Menicon will be launching the Miru 1 month Menicon silicone hydrogel lens on stand 13, which is named after the Japanese verb miru, "to see." Menicon has developed two proprietary technologies (MeniSilk and Nanogloss) which combine to create 'exceptional wettability and comfort and deliver outstanding
oxygen transmissibility.'