Against the Rule Astigmatism

• Touch along the vertical meridian.
  • Flattest Curve in the 90 Meridian
• Pooling (clearance) along the horizontal meridian
  • Steepest Curve in the 180 meridian

Flat Fit

• Apical touch
• Peripheral pooling (clearance)
• Indicates edge lift

Ideal Fit

• Also known as Alignment Fit

• Even distribution of teas/fluorescein
• represents uniform fluorescein pattern, not an on-K fit.
• Bright ring of fluorescein around perimeter due to flatter peripheral curve.

Steep Fit

• Apical pooling (clearance)
• Central vaulting
• Peripheral touch
• Steep fit is sometimes called Apical Clearance Fit
• Indicates a tight lens fit

With The Rule Astigmatism

• Pooling (clearance) along the vertical meridian.
  • Steepest Curve in the 90 Meridian
• Touch along the horizontal meridian
  • Flattest Curve in the 180 meridian

Against the Rule Astigmatism

• Touch along the vertical meridian.
  • Flattest Curve in the 90 Meridian
• Pooling (clearance) along the horizontal meridian
  • Steepest Curve in the 180 meridian

Flat Fit

• Apical touch
• Peripheral pooling (clearance)
• Indicates edge lift

Ideal Fit

• Also known as Alignment Fit
• Even distribution of teas/fluorescein
• represents uniform fluorescein pattern, not an on-K fit.
• Bright ring of fluorescein around perimeter due to flatter peripheral curve.

Steep Fit

• Apical pooling (clearance)
• Central vaulting
• Peripheral touch
• Steep fit is sometimes called Apical Clearance Fit
• Indicates a tight lens fit

With The Rule Astigmatism

• Pooling (clearance) along the vertical meridian.
  • Steepest Curve in the 90 Meridian
• Touch along the horizontal meridian
  • Flattest Curve in the 180 meridian

Lens fitting philosophies

interpalpebral fit → lens sits between the lids and is well-centered

lid attached → lens is attached to lids and controlled by lids, sits more superiorly

Interpalpebral Fitting

An interpalpebral lens-to-cornea fitting relationship often refers to a lens that centers well and is positioned between the lids. It is often achieved with a slightly smaller overall diameter and steeper base curve radius than a lid attachment design.

- work best with wider apertures

Lid Attachment Fitting

The lens design includes an edge contour that sloped toward the lid to enhance lid-lens contact, often resulting in a slightly superiorly decentered fitting relationship.

- lid doesn't feel the lens with each blink because it slightly overlaps the lens

-Lid attachment RGP fits should show a thin, even edge-to-edge layer of fluorescein stained tear film that
exhibit alignment or slight apical feathering as well as less than 180 degrees of bearing in the
mid-periphery to allow for a good tear exchange with each blink.