Eagleview Eye Clinic

Tag bifocal

SEGMENT HEIGHT

Segment height refers to the vertical measurement of a bifocal or progressive lens segment.

What it’s for:

Segment height is used to:

  1. Position the lens segment correctly
  2. Ensure optimal vision through the segment

Measurement:

Segment height is typically measured from the lower eyelid margin to the top of the segment.

LENS TYPES ACCORDING TO FUNCTION

These includes:

a. SINGLE VISION LENSES: These are lenses with just one power from top to botton.

b. BIFOCAL LENSES: These are lenses with two different, at the top for distance view and one below for objects close to the individual.

c. TRIFOCAL LENSES
Trifocal lenses are lenses with three powers the one at the top for distance vision, the middle one for intermediate distance and the last one below for near vision. Although it’s not really in vogue any more.

d. PROGRESSIVE ADDITION LENSES
PALs contains a myriad of optical powers from the top to the bottom. Another distinct feature of this lens is that it doesn’t posses the unsightly and visible demarcation in bifocal and trifocal. A very popular PAL brand is the varilux or varifocal lenses.