The Extreme H2O 54% (hioxifilcon D) spherical soft contact lens for daily wear is indicated for the correction of visual acuity in aphakic or Therefore, the continuing ocular health of the patient and lens performance on the eye should be carefully monitored by the prescribing eye care practitioner. The potential impact of these factors on the patient’s ocular health must be carefully weighed against the patient’s need for refractive correction. Consequently, when selecting an appropriate lens design and parameters, the eye care practitioner should consider all characteristics of the lens that can affect lens performance and ocular health, including oxygen permeability, wettability, central and peripheral thickness, and optic zone diameter. The toric lens provides a more even surface over the highly uneven astigmatic cornea and thus helps to focus light rays on the retina.ĭue to the small number of patients enrolled in clinical investigation of lenses, all refractive powers, design configurations, or lens parameters available in the lens material were not evaluated in significant numbers. Because an oxygen atom has a greater electronegativity than a hydrogen atom, the O―H bonds in the water molecule are polar, with the oxygen bearing a partial negative charge (δ−) and the hydrogens having a partial positive charge (δ+).In its hydrated state, the EXTREME H2O 54% (hioxifilcon D) soft contact lens, when placed on the cornea, acts as a refracting medium to focus light rays on the retina. The O―H distance ( bond length) is 95.7 picometres (9.57 × 10 −11 metres, or 3.77 × 10 −9 inches). The two hydrogen atoms are bound to the oxygen atom at an angle of 104.5°. The water molecule is not linear but bent in a special way. The root of these anomalies lies in the electronic structure of the water molecule. In its solid form, ice, water is less dense than when it is liquid, another unusual property. For example, its melting point, 0 ☌ (32 ☏), and boiling point, 100 ☌ (212 ☏), are much higher than would be expected by comparison with analogous compounds, such as hydrogen sulfide and ammonia. Witness an experiment explaining why fresh water and seawater have different freezing points See all videos for this articleĪlthough its formula (H 2O) seems simple, water exhibits very complex chemical and physical properties.
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