Proclear Toric XR contacts by Coopervision are designed to address the problem of fitting patients with extremely high astigmatism with a toric soft lens design. Astigmatism is the most common refractive error found among patients resulting from an irregular shape of the cornea. In cases of astigmatism, the cornea is shaped more like a football than a sphere. As light passes through this refractive medium it comes to focus at two different focal points on the retina. In order to correct his problem, a prescription must address each focal point independently and often to varying degrees. This is accomplished through addressing the near-sightedness or far-sightedness of a patient through the spherical correction, or sagittal plane. The astigmatism is corrected through cylinder power, or the tangential plane. The point at which each power is at 100% of its correction resides at an angle of 90⁰ from each other. This can become problematic when attempting to fit a contact, especially when the patient has a large amount of astigmatism, or cylinder correction. The higher the amount of cylinder, the more precisely the lens must fit. If a high cylinder contact lens shifts even slightly, it will reduce the patient’s visual acuities by several lines on the Snellen chart.
Patients who simply have correction for farsightedness or nearsightedness with no astigmatism correction wear spherical lenses, meaning any meridian of the lens has the same power or prescription. During the course of wear, a spherical lens will rotate constantly as the patient blinks or rubs their eyes. A toric lens cannot do this since the correction for astigmatism must reside in a tangential plane 90⁰ from the spherical plane. Proclear Toric XR lenses are designed to provide ultimate stabilization during wear to prevent this problem. This lessens what is known as the rotational recovery time — the time it takes for a lens to be moved from its primary position of precise visual acuity and return to that position. This rotational return can be lessened when the eyecare practitioner takes into account the radius, base curve and centering of the contact lens. The Proclear Toric XR lens has more than 45,000 different parameter combinations to choose from making them ideal for fitting hard to fit toric contact lens patients.
In addition to providing an excellent toric design, the Proclear Toric XR also provides the patient with better wearability due to a combination of phosphorylcholine and omafilcon A hydrogel technology. Phosphorylcholine attracts water molecules in addition to being extremely biocompatible. The biocompatibility of this substance is widely used in cardiac surgeries where stents are implanted as well as other procedures of a vascular nature. The rejection rate is extremely low for this material which also works well for contacts. The absorption and attraction of water, of which omafilcon A is comprised of 41%, maintains the fluid environment necessary for a healthy cornea. This prevents the buildup of proteins, the colonization of bacteria responsible for infections and irritation associated with allergens. Hydrogel lenses also provide a level of oxygen transmission to the cornea preventing a condition known as corneal neovascularization. Corneal neovascularization occurs when the cornea is deprived of oxygen. The body will initiate an autoimmune response through a new ingrowth of blood vessels in an effort to bring need oxygen and nutrients. If this ingrowth encroaches on the visual axis, vision becomes compromised.