MYTH #8: Patients with ADD at +2.00 and +2.50 do not get adequate near vision with multifocal contact lenses.
FACT: The quality of vision is largely a product of optical design. It isn’t the power of the ADD but the type of optics used to produce the power.
There are a finite number of ways to produce ADD power in a progressive design contact lens multifocal. Because soft lenses are centered on the eye, it is nearly impossible to produce functioning alternating vision. That precludes the use of traditional segmented designs like flat tops or executive straight tops which require lens translation in order to work. This forces designers to look at other traditional simultaneous performance designs.
We have seen several simultaneous designs evolve. I believe aspherics are the oldest or are perhaps tied with the conventional center-ADD or reverse center-ADD designs used in conventional PMMA and more recently in GP lenses. In addition, there are multiple alternating zone designs which to date have not achieved much popularity.
In soft lenses we have taken the aspherics, the center-ADD and reverse center-ADD lenses and evolved and adapted them to achieve effective simultaneous vision. Unfortunately, there are some optical realities that must be considered - first, dominance and non dominance. We must satisfy “Mother Nature’s” requirement for best distance vision in the dominant eye. It continues to be true that this can best be done with spherical optics. Also, the patient will require the same sharp vision at near which also requires spherical optics in the ADD power. Full aspheric optical zones are challenged when the ADD powers go above +1.50. The results manifest themselves in less than sharp image quality. With ADDs at +2.00 and +2.50, the near image reduction is significant and for many patients, unacceptable.
In order to better service both the distance and near image quality, ProClear Multifocal merges the optical technology. That puts spherical optics in the dominant eye for distance and spherical optics for near on the non dominant eye. A concentric aspheric zone in both the (D) and (N) lenses provides the progressive optics for all other ranges. The ProClear Multifocal provides excellent dominant distance, excellent non dominant near and a balance at intermediate.
Many believe the balance of optics minimizes the image quality disparity and optimizes patient satisfaction – I believe it because I hear it from practitioners every day. Near vision is no problem with the ProClear design whether it is a +1.00 or a +4.00.