Progressive Lens Design Quiz

Clinical Skills and Refractive Management: Progressive Lenses

• OPT505 Clinical Skills and Refractive Management course covers progressive lenses.
• Core competencies include advising on, ordering, and dispensing suitable optical correction, considering durability, comfort, appearance, age, and lifestyle (including multifocal lenses).
• Adjusting spectacle frames to optimize physical and optical performance is also a crucial competency.

Learning Outcomes

• Defining progressive lenses (the progressive lens surface).
• Listing the advantages and disadvantages of progressive lenses.
• Understanding differing design criteria (hard and soft).
• Understanding prism thinning.
• Defining free-form surfacing and its impact on lens design.
• Discussing aspects of fitting.
• Considering reasons for non-tolerance to progressive lenses (PPLs).
• Following a plan for verification and duplication.

Progressive Power Lenses

• Progressive power lenses offer continuous vision at all distances.
• They function like trifocal lenses, with 3 areas of vision.
• Lens power increases progressively across the lens.
• Distance vision is typically at the top, and near vision is at the bottom of the lens.

PPL Advantages

• No visible jump between different focal zones.
• Wide range of lens designs.
• Good cosmetic appearance.

PPL Disadvantages

• Altered relationship between eye and head movement.
• Areas of indistinct vision.
• Areas of astigmatism.
• Greater fitting accuracy is needed.
• Frame size/shape may limit lens availability.
• Choice of lens designs may be restricted.

Anatomy of a Progressive Lens

•  Progressive lenses feature a distance, intermediate, and near zone.
•  A blending region connects these areas.
•  A progressive corridor guides the progression of power across the lens.

Power Profile of a Plano Lens with +2.00 Add

• A diagram illustrating lens power change across zones.
• Shows the gradient change from distance to near.

Power Profile of a Progressive Power Lens

• Progressive lenses are characterized by a continuously shortening surface radii.
• This continuous change in curvature causes unwanted astigmatism.
• Various examples showcase different levels of astigmatism as the distance from the edge of the lens increases.

Lens Performance

• Iso-cylinder lines join points with identical surface astigmatism (0.25D or 0.50D difference).
• Vector plots illustrate astigmatism direction and amount.
• Mean power plots show how mean power changes across the progressive surface.
• Power profile diagrams demonstrate the beginning of power progression.

Lens Markings

• Illustrative diagrams, including the prism reference point, add, logo, and material markings on the lenses.

Free-form Technology

• Free-form surfaces deviate from simple mathematical models.
• They are defined by the sag at many data points.

Free-form Surfacing

• Allows for incorporating cylindrical correction.
• Facilitates improved off-axis performance.
• Enables manufacturers to better account for frame fit and RX.

Front Surface vs Back Surface

• Most progressive lenses have their progressive zones on the front, and distance correction on the back.
• On the back, you get wider zones for near and intermediate vision.

HoyaluxID

• Designed to reduce wavy and skewed distortions between front and back lens surfaces.
• Offers wider fields of clear view in shorter corridors (14mm or 11mm).
• Needs more measurements, including the working distance.

Individualised PPLs

• BBGR Anateo, Essilor, Hoya, Nikon, Norville, Rodenstock, and Zeiss individual series are mentioned.

Dispensing PPLs

• Important to consider lens and frame choices when dispensing progressive lenses.

PPL Terminology

• Explains terms like fitting cross, progression, corridor length, short and long corridors, and the prism reference point.

Fitting PPLs

•  Methods for proper centration point determination.
• Methods for verifying the vertical fitting cross position from the center of the patient's pupil.
• Determining minimum vertex distance.
• Measuring the pantoscopic angle (approximately 10 degrees).
• Checking the depth and fit of the frame.

Fitting Cross

• The progression usually starts 2 to 3 mm below the fitting cross, about 0.12D greater than the distance prescription.

Failure to Adapt

• Causes, such as incorrect Rx, incorrect measurements, poor frame fit, poor lens design, and glazing issues.

Frame Selection

• Visualizing how the full addition points fit within the frame for usable or unusable fit.

Pantascopic Tilt

• Visual axis (line of sight) should ideally be at right angles to the optical axis for optimal progressive lens performance.
• Patients may report issues like oval plates or sloping floors.

Incorrect Fitting Heights

• Common issues for progressive lens wearers are improper fitting heights.
• An excessively high fitting height creates blurring issues at distance.
• A shallow frame may present a similar effect.

Adaptational Difficulties

• Dealing with uncorrected vertical phoria.
• Dealing with astigmatism having oblique axes.
• Managing vertical differential prismatic effect.
• Dealing with anisometropia.
• Recommending short corridor designs for hyperopes.

Fitting Tips

• Following guidelines for minimum fitting height (at least 10 mm above the fitting cross).
• Employing the shortest possible vertex distance.
• Placing the fitting cross at the pupil center, not the corneal reflex.
• Fitting the frame before taking measurements for precise fit validation.
• Implementing guidelines for managing patient expectations.

Recommended Reading

• Listing different articles on fitting progressive lenses.

Test your knowledge on progressive lens designs including hard and soft designs, user benefits, and the effects of various lens characteristics. This quiz covers key concepts like surface astigmatism, progression lengths, and fitting for optimal patient tolerance. Understand the significance of 'free-form' surfacing and iso-cylinder lines in lens performance.