Purevision Multifocal lenses manufactured by Bausch and Lomb use an innovative silicone hydrogel design to provide crisp, clear vision for presbyopic patients as well as maintaining good ocular health. Prebyopia is a condition affecting patients as they age, resulting in a need for additional power to see objects at near. Purevision Multifocals are aspherically designed meaning they have a flatter radius of curvature allowing for a flatter lens and less spherical aberration. This results in better vision as well as comfort. Additionally, Purevision Multifocals are designed using concentric zones for reading distances allowing patients to see objects as easily at the near point as well as they are able to at infinity. The combination of optics and biocompatibility make Purevision Multifocals an exceptional lens choice for mature patients.
Purevison Mulitifocals are designed to correct for a condition known as presbyopia. Presbyopia is a common refractive error generally occurring at around age 40. One third of the ability of the eye to focus resides in the refractive transparent medium of the cornea. The remaining two-thirds may be found with the crystalline lens. This lens bows and flexes as we view objects at different focal lengths. It is held in place by suspensory ligaments known as the zonules of Zinn. The ability of the crystalline lens to flex is known as accommodation or the accommodative reflex. As a natural part of the aging process, these ligaments begin to stiffen making the process of accommodation more difficult until finally our ability to view objects closely and clearly become extremely difficult. To combat this refractive error, a bifocal is prescribed. Basically, additional power is added to the distance correction to allow for the lack of accommodation of the crystalline lens. This is achieved in Purevision Multifocals using concentric zones for different focal lengths from near to intermediate to distance vision.
One of the problems that a patient may encounter with either ophthalmic lenses or contacts is a higher order aberration known as spherical aberration. The higher the degree of the radius of curvature of the lens the higher the degree of refraction of light rays being bent back toward the optical center of the ophthalmic device. This creates an area of distortion along the periphery causing a perceptual problem for the observer. Aspherical lenses are designed to combat this problem by maintaining a flatter curvature along every meridian of the lens. This provides a wider field of view resulting in clearer vision as well as less irritation for the contact lens wearer along the peripheral edge of the contact. Purevision Multifocals are designed using this process allowing the patient better vision in every instance including low light situations. Mature patients have to rely on less and less visible light reaching the retina as they age. The more light allowed reaching the retina the better the patient will be able to see. These lenses accomplish that goal.
Additionally, Purevision Multifocals also assist the patient in maintaining good ocular health through preventing complications associated with deprivation of oxygen, protein buildup, bacterial infections, and allergies. Purevision Multifocals are manufactured using a silicone hydrogel material, balafilcon A, resulting in a high water content of 36% as well as a very high level of oxygen with a Dk/t of 112. This parameters give both the patient and eyecare practitioner peace of mind when assessing ocular health benefits as well as provide great vision to the patient.