The Eye- External
Protect the eye from debris and distribute tears across the cornea with each blink.
Eyelids (Palpebrae)
Horizontal width of the lens opening.
A (Eye Size)
deviates light 1 cm at 1 meter.
1 Prism Diopter (Δ)
It measures and verifies the prescription of finished lenses.
lensometer
Frame completely surrounds the lens. Most durable.
Full-Rim
moves eye inward (adduction)
Medial Rectus
Length of the temple piece from hinge to tip.
Temple Length
Corrects exo deviations (eye turns outward)
BI (Base In)
Rotates to bring target lines into focus. Reads sphere and cylinder power.
Power Drum/Wheel
No frame around lenses. Requires polycarbonate or Trivex.
Rimless (Drill-Mount)
It produces mucus to help lubricate the eye.
Conjunctiva
(also called Geometric Center Distance)
Frame PD
Thin press-on prism for temporary/diagnostic use.
Fresnel Prism
Rotates the target to align with the cylinder axis of the lens.
Axis Wheel
Lightweight, hypoallergenic, corrosion-resistant
Titanium
Produces, distributes, and drains tears.
Lacrimal System
Distance between the two lenses at the narrowest point.
DBL (Bridge Size)
Corrects eso deviations (eye turns inward)
BO (Base Out)
Adjustable ocular for focusing the reticle to the examiner's eye. Always adjust FIRST.
Eyepiece
Rim on top, nylon cord on bottom. Lightweight.
Semi-Rimless
The bony socket that houses the eye, made up of seven bones.
Orbit
Longest diagonal measurement of the lens opening.
ED (Effective Diameter)
Corrects vertical deviations
BU (Base Up) / BD (Base Down)
Three dots that mark the optical center and axis on the lens.
Marking Device
Returns to original shape
Memory Metal (Flexon)