The document explains progressive addition lenses (PALs), which have increasing power for vision as one looks downward through the lens. It traces the history of PALs from their introduction in 1907 to the first commercial product by Essilor in 1959, and outlines the basic design components, including distance, near, and intermediate zones. Additionally, it discusses various designs of PALs such as mono and multi designs, symmetric and asymmetric layouts, and hard and soft designs, along with specific PAL markings for lens identification.

1. Progressive Addition Lens
Ayan Das, 4th Sem,
George College of Management and Science

2. Definition
The power of addition gradually increases as the line of the vision sweeps downward
through the lens.

3. History
• First patient on progressive power lenses was published in 1907 by Owen Ave
• Essilor company introduced first commercially available PAL,Varilux in 1959

4. Basic design of PAL

5. • Distance
A designated zone located in the upper portion of the lens, which provides the necessary
distance correction.
• Near
A designated zone in the lower portion of the lens, which provides the necessary near
addition or near power.

6. Intermediate
• A corridor in the central portion of the lens connects these two zones, which increases
progressively in plus power from the distance to near.This zone is also known as
“Progressive zone”

7. PAL designs
• Mono design and Multi design
• Asymmetry and Symmetry design
• Hard and Soft design

8. Mono and Multi design
• In case of Mono design progressive addition lens, a single design is used
for all addition powers.
• In Multi design the position for near vision changes with the addition
power changes with the addition power change, i.e. the near area goes up
with the increase in the addition.

9. Asymmetry and Symmetry design
• In case of Symmetrical PAL design, the right and left lenses are identical.
• Asymmetric PAL design incorporates a nasal offset of the near zone and
has separate design for right and left lens.

10. Hard and Soft design
• A Harder PAL design concentrates the astigmatic error into smaller areas
of the lens surface, thereby expanding the areas of perfectly clear vision at
the expense of higher levels of blur and distortion.
• A Softer PAL design spreads the astigmatic error across larger areas of
the surface, thereby reducing the overall magnitude of blur at the expense
of narrowing zones of perfectly clear vision.

12. PAL markings

13. PAL markings
• A and A1:They are two hidden circles, which are permanently etched on
the lens at 34 mm apart.
• B:This point is the distance optical center (DOC) of the lens, also known
as Prism Reference Point.
• C: Hidden addition power situated at the temporal side and is visible by
fogging.
• D: 0 to 180 degree axis line passing through the DOC.

14. PAL markings
• E: Fitting cross lies above the DOC.
• F: Distance power(DP) circle to check the exact distance power with the
help of Lensometer.
• G: Hidden logo situated nasally and get visible when ink marking is
removed.
• H: 7mm to 9mm circle is the center of the near vision area and is inset by
2.5mm.

15. PAL images