Soft Lenses: Soft or hydrogel lenses are soft lenses that are made of water containing plastics. Hydrogel lens materials have varying degrees of oxygen permeability. Newer silicone hydrogel materials allow even more oxygen to pass through these lenses, reducing the risk for chronic oxygen deprivation of the cornea.
Soft contact lenses are larger than the diameter of the cornea, draping over the entire cornea that make these lenses more comfortable. They can be used to correct for nearsightedness, farsightedness or presbyopia (loss of ability to focus at near over 40 years of age). But, because these lenses conform to the surface of the cornea, they do not correct for corneal optical considerations such as astigmatism. In such cases, special soft lenses called toric lenses are used. The comfort and versatility of soft lenses enables us to fit them not only for conventional daily wear but also for extended wear, multifocal use, cosmetic color, and special purposes post-surgical, and more.
Silicon Hydrogel Soft Lenses: Silicon hydrogel soft lenses are arguably one of the best developments ever in the history of contact lenses. Silicon is a material that has been used in RPG contact lenses for over the past 50 years to increase oxygen permeability. Since Silicon has great oxygen permeable properties, it has been incorporated into soft hydrogel contact lenses and now increase oxygen permeability to an over four fold increase over the standard hydrogel lenses.
Rigid Gas Permeable (RGP) Lenses: Rigid gas permeable lenses are made of plastics without the water content that is present in soft contact lenses. These lenses are often used to correct irregularities in the corneal surface such as high astigmatism. They can also be used to mask the effects of corneal scarring, corneal distortion such as keratoconus or following surgery of the cornea such as corneal transplants. RGP lenses can also be used for multifocal corrections. They provide excellent optical correction and are do not dry out in the same way that soft contact lenses do.
Wearing Schedules and Disposal Intervals: Contact lenses are most commonly worn for day time use or daily wear. Some people wear their lenses overnight or extended wear. The Food and Drug Administration (FDA) has approved certain lenses for this type of wearing schedule. Not every eye is suited for extended wear and the risks for extended wear should be discussed with your practitioner.
Daily lenses are typically replaced on a regular interval for best eye health. The replacement schedule can vary from daily (single use lenses, good for patients with allergies and solution sensitivities) to the more common intervals: semimonthly (every 2 weeks) and monthly. Certain lenses are replaced quarterly to annually—although this replacement schedule is more typical for semi-custom or custom specialty lenses. Disposable lenses replaced on a regular basis do not develop the same types of contact lens deposits that could cause discomfort or irritation to the eye.