Optical Characteristics of Lenses (2.2)

What is the optic axis?

line connecting the centers of curvature of two lens surfaces

What are lens poles?

points on the front and back surfaces of lens which intersect the optic axis

What does the SE give us?

circle of least confusion

What does giving a patient their SE do?

places circle of least confusion on their retina

When do we give patients their SE?

If we do not want to give patients their full amount of cyl

When would you not want to give a patient their full amount of cyl?

oblique astigmatism

first time spec wearer

How does an image form for a sphere lens?

parallel rays of light are incident onto convex lens and form a point image at secondary focal plane

What is the size of a blur circle dependent on?

distance from secondary focal plane and size of lens aperture

If you want to determine edge thickness in the meridian with the longest distance from optical center to edge, what power do you need to use?

Power in the oblique meridian

How to find power in the oblique meridian for a sphero-cyl lens?

Pø=Psph + (Pcyl x sin^2 (a))

When do you need to find the combination of two cyl lenses to put into a single sphero-cyl lens?

fitting toric CL using SCOR (sphereo-cyl over refraction)

What power is induced by lens tilt?

Sph power (minimal)

Oblique cylinder power (significant)

The cyl power change as a result of lens tilt results in what?

oblique astigmatism aberration

If you give a pair of specs pantoscopic tilt, what meridian will your added cyl power be?

parallel to axis of rotation of lens, therefore 180º

IF you give a pair of specs faceform/wrap, what meridian will your added cyl power be in?

parallel to axis of rotation of lens, therefore 90º

If you tilt a plus lens, what kind of cyl do you add?

plus cyl

If you tilt a minus lens, what kind of cyl do you add?

minus cyl

For a sphere lens, where forms a blur circle?

Anywhere not at secondary focal point

For a sph/cyl lens, the are between the two line images is called?

interval of sturn