This document discusses progressive lenses, including their history, types, features, markings, fitting process, advantages, and disadvantages. It provides details on: - The four main types of lenses - single vision, bifocals, trifocals, and progressive addition lenses. - Key features of progressive lenses, including having multiple focal points that change continuously across the lens rather than distinct segments. - Important temporary and permanent markings on progressive lenses used in fitting, including the fitting cross, distance reference circle, and lateral locator lines. - The process of accurately relocating the fitting cross from temporary to permanent markings to ensure proper positioning over the pupil.

1. BY,
SANJANA CHOUHAN.S

2. OBJECTIVES
• Details of progressive lenses.
• Types of progressive lenses.
• Progressive markings.
• Fitting error and alignment and also the
types of bi-focals

3. INTRODUCTION
• The very first Progressive lens was invented
by Bernard Maitenaz, from the French
company Essel, in the year 1959 –known as
Varilux lens .
• A progressive addition lens has more than one
focal point or dioptric powers, without the
need to switch lenses.
• Progressive lenses can be called progressive
addition lenses (PAL), progressive power
lenses (PPL).

4. • Based on the number of focal points,
ophthalmic lenses are divided into four types
 Single vision lenses
 Bifocals
 Trifocals
 Progressive addition lens

5. • SINGLE VISION LENSES - Corrects only
one vision at a time . (Single focal point)
• BIFOCALS – Corrects two vision, Distance
and near.(Two focal points)
• TRIFOCALS – Corrects three vision,
distance, near and intermediate.(Three focal
points)
• PROGESSIVE – Corrects different
distances.(Many focal points)

7. FEATURE OF A PROGRESSIVE LENS
• A progressive lens provides visual
compensation at all distances namely Far,
Distances and Near.
• It has a lens that changes its dioptric power
continuously, starting at its geometric centre
and gradually progressing its dioptre value.
• The progression of power occurs in an
optically pure progression corridor.

8. • By “Pure” it is meant that there are no
astigmatic aberrations in the peripheral zones
of the lens .
• The progression corridor starts few
millimetre (mm) below the fitting cross and
keeps progressing until it reaches the near
visual field .

9. • At the lateral zones the astigmatic
aberration zones are present, where vision is
not totally clear .
• The aspheric lens design is responsible for
the power progression of PALS and has
different radii of curvature.
• It is made up of multiple focal points due to
change in its radius of curvature.

11. PROGRESSIVE LENS DESIGNS
• Hard design
• Soft design

12. TEMPORARY MARKINGS
 Distance reference circle:
• This is the identification circle used to check
the distance lens power.
• It should be crossed checked with the
lensometer or focimetry.
 Fitting cross:
• It should be located exactly at the center of
the patients pupil.
• It is used to measure the MPD(monocular
pupillary distance) and fitting height.

13.  Prism reference circle:
• This is the point which is used to check the
amount of prism in the lens.
 Near reference circle:
• This marking is used to check the near vision
power.
• It should be verified with the lensometer.

14.  Small horizontal locater:
• This indicator should be level with the prism
reference point.
• This mainly helps the surfacing lab markers to
mount the lenses and check the position of
horizontality.
• The horizontality precision can even be
spotted easily with the naked eye.

15. TEMPORARY MARKINGS

16. PERMANENT MARKINGS

17. PERMANENT MARKING
 Lateral circles:
• There are two small lateral circles that are used to
relocate the temporary markings and they are
positioned exactly 34 mm apart one each on the nasal
and temporal sides.
• Lens logo and material code:
• The lens type is identified with the help of lens logo.
• The material coat helps us to identify the type of
lens material.

18. • E.g: In case of 1.5 index the lens logo is
followed by no.6 and in case of polycarbonate
lens, a letter P is seen.
• This logo is nasally located.
 Addition power:
• This is located below the temporal locator
• We can read the addition power directly from
the lens by using the lensometer.

19. DETAILS OF LENS MARKING
 Central fitting cross:
• The central fitting cross is marked with the
ink
• Mounted in the frame as per the center of
the customers pupil.
• It is a temporary marking.
• The marking can be wiped off with isopropyl
alcohol.

20. RELOCATING THE FITTING CROSS
• A template is provided by the manufacturer
for the progressive lenses.
• By placing the lens on the template marking
sure to align the 2 lateral traces in the
horizontal direction and mark the fitting
cross.

22. • The wearer should be looking straight ahead
with the head in the straight up while the
measurements are being taken.
• The fitting cross is placed exactly at the
pupillary center.
• If these precautions are not taken it will lead
to inaccurate measurements.

23. ADVANTAGES
• Improved appearance
• Complete range of working distance
• NO JUMP effect
• Thinner and lighter
• No need to switch lenses
• No dividing line

24. DISADVANTAGES
• Peripheral aberrations
• Adaptation problems
• More critical fitting required
• More expensive

25. Guess the markings ???

26. THANK YOU