Glossary of Terms

Aphakia
Absence of the crystalline lens following cataract surgery. A specialty GP contact lens is normally indicated.


Aspheric Contact Lens
Posterior aspheric contact lenses progressively flatten from center to edge. The rate of flattening (eccentricity) can be varied to enhance lens to cornea alignment or to produce a progressive multifocal effect for presbyopic patients.


Aspheric Peripheral Curve
A progressive flattening curve applied to both aspheric and spherical lenses providing an improved lens to cornea fitting relationship. HPC and CAS are examples of aspheric peripheral curves.


Astigmatism
Unequal curvatures of the eye resulting in an unequal focus of light rays on the retina. Toric or Ellip-See-Con lenses are normally indicated.


Bifocal Contact Lens
Contact lens with two focal lengths, (distance and near corrections). See VFL 3


Bridge II or RK Bridge
A custom reverse geometry contact lens design developed to better accommodate atypical corneal shapes. A complex aspheric posterior surface that actually steepens in the para-central area, relative to the flatter central base curve area. Peripherally, the Bridge II design flattens to accommodate the flatter peripheral corneal topography.


Conform-A-Spheric (CAS)
The CAS peripheral curve was one of Conforma's earliest endeavors into aspheric lens manufacturing. While not a definable conic section, the CAS peripheral curve continually flattens as it progresses outward toward the lens edge. The CAS curves are available in three asphericities: CAS 141 for average edge lift, CAS 121 for less edge lift and CAS 161 for more edge lift. The CAS curves are still used routinely on Conforma specialty lenses such as VFL II and Ellip-See-Con. CAS curves were designed for the smaller diameter hard lens designs available many years ago. The optimum edge lift is achieved at a curve width of approximately .5mm. When attempting to utilize a CAS periphery on a lens design outside of the normal intended parameter range, consider contacting Conforma consultation to avoid an unacceptable lens to corneal fitting relationship.


Conform-A-Thin
A rigid thin lens design offered as a suitable alternative to Polycon II. Lens parameters are standardized with three diameter options, 8.5, 9.0 and 9.5.


Eccentricity (E-Value)
is a numerical expression which describes the rate or degree of flattening of an aspheric (conic section) lens surface.


E-Lens
The Conforma E-Lens is a rigid corneal lens with a posterior surface contoured to match the corneal surface. The central optical section is spherical and the periphery is aspheric. E-Lens is manufactured from several moderately oxygen permeable GP materials.


Elite
Conforma Elite is a rigid corneal lens with a posterior surface contoured to match the corneal surface. The central optic section is spherical and the periphery is aspheric. Elite is manufactured from several highly oxygen permeable GP materials.


Ellip-See-Con
Posterior aspheric contact lens that progressively flattens from center to edge to better align with the corneal surface. The Ellip-See-Con design is frequently prescribed for astigmatism and irregular corneal surfaces. Efficiently masking significant corneal as well as neutralizing some residual astigmatism, Ellip-See-Con is frequently used as a problem solver design.


Hyperbolic Peripheral Curve (HPC)
HPC is an aspheric peripheral curve system developed by and only available from Conforma Contact Lenses. Hyperbolic is a mathematical term used to define the shape of a conical or aspheric surface. The HPC curve is an aspheric surface that progressively flattens from a smooth transition at the optical zone to the lens edge and approximates the contour of the cornea. This improved center to edge alignment provides enhanced comfort, a more uniform distribution of bearing pressure and improved tear exchange. These combined fitting characteristics add up to quicker adaptation and healthier corneas. The HPC curve is Conforma's "standard" or the default peripheral curve system routinely applied to most Conforma designs, including E-Lens, Elite and VFL 3. The HPC periphery, when applied to a spherical lens, was designed to match the sagittal depth and edge lift of a standard tri-curve design. Fitting a single vision spherical lens with a HPC periphery requires no alteration to your fitting philosophy. A central fitting alignment or upper lid attachment approach will prove successful for most patients. Fitting a VFL 3 lens, or other aspheric design, requires compensation for the flattening effect of the entire posterior surface (base curve + peripheral curve). The HPC peripheral curve system was designed for overall lens diameters of 9.0mm to 10.0mm. If you are attempting to fit lenses out side of this diameter range, contact Conforma consultation to discuss the appropriate optic zone and curve width options.


Hyperopia
Farsighted, refractive error in which light rays focus behind the retina. Single vision GP lenses such as E-Lens, Elite or Conform-A-Thin are normally indicated.


Keratoconus
A noninflammatory protrusion of the cornea resulting in reduced vision. Custom aspheric or other speicalty RGP contact lenses normally provide better visual acuity than spectacles. See Conforma-K&tm;


Multifocal Contact Lens
Contact lens with multiple (2 or more) focal lengths. Correcting distance, near and usually intermediate vision for presbyopic patients. See VFL® 3


Myopia
Nearsighted, refractive error in which light rays focus in front of the retina. Single vision GP lenses such as E-Lens, Elite or Conform-A-Thin are normally indicated.


Presbyopia
Impairment of near and intermediate vision due to the natural aging of the eye. Normally occurs at about age 40. Monovision, VFL 3 or other multifocal contact lenses are normally indicated.


Refractive Surgery
The surgical alteration of the cornea to reduce or correct the refractive error. Any post-operative refractive error can be addressed with a custom specialty or reverse geometry GP contact lens.


Refractive Therapy
Ortho-K, myopia control, all terms used to describe contact lens induced corneal change resulting in reduced or corrected refractive error. See Paragon CRT®


RK Bridge or Bridge II
A reverse geometry contact lens design developed to better accommodate atypical corneal shapes. A complex aspheric posterior surface that actually steepens in the para-central area, relative to the flatter central base curve area. Peripherally, the Bridge II design flattens to accommodate the flatter peripheral corneal topography.


SuperAdd
Supplemental add power applied to the front surface of a VFL 3 lens to extend or increase the total add affect. See VFL® 3 SuperAdd


Toric
A specialty GP contact lens design for astigmatism. Bi-Toric, Back Toric or Front Toric designs may be selected based on the amount and type of astigmatism involved.


Transplant
A corneal transplant or grafting of corneal tissue due to advanced Keratoconus, injury or other degradation of normally transparent corneal tissue. Following transplant surgery custom aspheric, reverse geometry or other specialty GP contact lenses may be indicated.


VFL 3
Aspheric multifocal contact lens for presbyopic patients. The aspheric base curve flattens from the center to the periphery, producing a progressive increase in plus power. This progressive power change creates the multifocal affect correcting vision at distance, intermediate and near.