Q: Who is a good candidate for HD lenses?
A: HD lenses are fantastic for a wide variety of patients. From young adults looking for true High Definition to mature adults needing a significant add requirement. These lenses are perfect for many. The difference is all in the fitting!
Q: What is spherical aberration?
A: Spherical aberration describes what happens when light rays entering a refracting (focusing) surface such as the cornea are less strongly focused at the center of the refracting surface and are progressively more focused off center. Images are focused on a series of points, resulting in “blur circles.” Fortunately, the human crystalline lens has optical properties that cancel out and neutralize most of the corneal-surface-induced spherical aberration.
Q: How do soft contact lenses affect spherical aberration?
A: The curvature of the front surface of any soft contact lens, when placed on the eye, will vary with its power, thickness and lens flexure. A minus lens used to correct myopia will reduce the dioptric curvature of the combined soft lens/corneal surface, and as a result, will reduce the spherical aberration at the eye’s front surface. However, this soft lens/corneal spherical aberration is often over-reduced. So much so that minus lens powers cause the compensating power of the crystalline lens to be unopposed. This can cause an overall increase in spherical aberration for these eyes. In the case of a plus lens used to correct hyperopia, the increased dioptric curvature of the soft contact lens/corneal surface will also increase spherical aberration. The resulting vision is less than ideal, including reduced visual acuity, contrast sensitivity and low depth of field.
Q: How do HD High Definition Aspheric lenses minimize spherical aberration?
A: In order for a soft contact lens to be effective in reducing spherical aberration, the amount of spherical-aberration-reducing curvature must vary with the power and thickness of the lens, and be compensating for the lens flexure on the eye. HD has incorporated aberration reduction geometry into all of its High Definition Aspheric lenses by using computerized ray-tracing programs and sophisticated ophthalmic instruments to determine these ideal aspheric curvatures for each lens power and thickness in their “unflexed” state. This unique design results in improved visual acuity at all distances, as well as increased depth of field, reduced refractive astigmatism and improved contrast sensitivity. Overall, patients enjoy crisper, sharper, clearer vision than possible with conventional soft contact lenses. Clinical studies have also found the standard High Definition Aspheric lenses effective for early presbyopes.
Q: What is Hypathin™ mold core technology?
A: A proprietary manufacturing process that produces the world’s thinnest contact lenses (0.06 mm @ -3.00). This ultra-thin design makes High Definition lenses extremely comfortable yet easy to handle, and promotes higher oxygen transmission.
Q: Why do you recommend using the High Definition Aspheric (and not the HDX Progressive Multifocal lens) when the patient’s add power is less than +1.00?
A: The High Definition Aspheric lens is an excellent choice of lens for emerging presbyopes, because you can add the plus power and still provide an excellent distance vision. The fitting is very simple: Add +0.50 diopter to the spherical equivalent of your patient. For example, if the patient’s Rx is +2.00 with +1.00 add power, add +0.50 to the spherical equivalent which equals to a +2.50 lens power.
Q: We have a lot of monovision patients in our practice. Is there any benefit in using the High Definition Aspheric lenses for this purpose?
A: Yes, definitely. Thanks to the High Definition Aspheric optics that provides extra sharp overall vision all you need to do is bump the plus to the dominant eye by 0.50 diopter and the non dominant eye by half of the add power. The result is improved binocularly “balanced” monovision, unlike with the standard spherical lenses.