6. Progressive power lenses (PPL)

what are PPL’s used for

to correct presbyopia (age related far sightedness)

PPL lenses are designed to

Lenses designed to provide continuous vision at all distances, and due to the lens power changing over the lens surface,

what are the zones of a ppl

1. distance

2. intermediate

3. near

what are test methods for PPLs

1. vector plots

2. Astigmatic contour plots

3. power profile

what are some brands that produce ppls

1. hoya

2. essilor

3. zeiss

PPL lenses are generally

thinned

what are the markings on PPLs

• Distance reference point: Optimal location for verifying the Distance prescription.

• ◦ Fitting point: The alignment point of the lens design, which is placed directly in front of the visual axis of the eye during primary gaze. ◦

• Prism reference point: Optimal location on the surface for verifying prescribed prism or prism thinning. It is located at the prism reference point ink marking, centred exactly between the permanent alignment reference markings. Conventional PPL lenses are prism thinned by 2/3rd of the Addition. ◦

• Near reference point: The optimal location for verifying the Add power of the prescription.

• ◦ Alignment reference point: Laser etching will be engraved on the lens surface. Nasal point will have manufactures logo and temporal side will have the Add. These etchings are used for the specific manufacturer lens template to mark the lens up with the above markings to view the fitting of the lens on a patient in a spectacle frame.

what are properties of hard design PPLs

• Aberrational astigmatism is confined to limited nasal and temporal areas.

• ◦ Distance vision is almost aberration free.

• ◦ Large distance area. ◦ Narrow intermediate.

• ◦ Wide reading area.

• ◦ Front surface design

what are properties of soft design PPLs

• Some aberrational astigmatism extends into the distance area affecting the peripheral vision.

• ◦ Large intermediate zone.

• ◦ Narrow reading area.

• ◦ Front surface design

what are properties of freeform PPLs

• Most advanced version of PPL lenses.

• Freeform is a manufacturing technology that can design customised lenses

• Created by computer controlled surfacing equipment.

• ◦ Can create lens of any prescription combination and any measurement.

• ◦ Wider field of view due to back surface design.

• ◦ Maximised VA at all distances.

• ◦ Reduced levels of aberrational astigmatism.

• ◦ Reduced level of ‘swim and sway’ effect.

PPL lenses can be

aspheric