Basic Lens Dispensing Part 6

Successful fitting of progressive lenses does not just mean being proficient with a ruler. Discussion, demonstration, educating the customer, prescription, the correct frame choice as well as correct measurements are all vital steps in a good progressive dispense. Learning the needs of the person you are dispensing to is essential.

Discussion Example:

• Discuss in detail the customer's lifestyle, their occupational requirements, hobbies, sports, leisure activities.
• Do they drive?
• How satisfied are they with the performance of the lenses they are currently wearing?
• Time taken here means you will have very few comebacks.

Demonstration and Education

Where possible, giving the customer a demonstration often alleviates concerns about wearing progressive lenses. Whilst the main information allows you to recommend the lenses most suitable, it also allows customers to make an educated choice in their lens design.

Remember, Free Form lenses will always provide better visual acuity.

Prescription and Frame Choice

Prescription and frame should always be considered simultaneously as with the dispensing of other lens forms.

The lens and frame material, frame type and shape should be considered not only for cosmetic but also for optical reasons. For example an aviator frame may not be suitable due to the shorter depth nasally, where the reading area would be on a progressive lens.

It is more suited to have the lens consultation prior to frame selection, this way the patients' optical needs are considered whilst choosing a frame, rather than selecting the lens that best fits the frame but not necessarily the patients' requirements.

Measurements

It is best to fit the frame prior to taking any measurements. This prevents any error due to the frame slipping whilst the measurements are taken. Pupillary distances must always be taken monocularly. The exact horizontal centration of the lens ensures that the customer uses the clear channel of vision rather than looking partially (or wholly) through the peripheral distorted area.

Studies have proven that using a pupilometer is generally more accurate than using a ruler. Mark the horizontal centration onto the dummy lenses to ensure that no mistakes have been made when recording the measurements. This also allows the vertical measurements to be recorded at the correct horizontal position.

When taking the vertical centration (heights), the customer must be sitting in a ‘normal' relaxed position looking straight ahead (primary gaze). Place yourself at the same eye level and mark at the pupil centre.

Once the heights have been marked on the lens, it is advisable to ask the customer to walk around the practice, or to stand and check the markings are still correct. Of course, large differences in height between the dispenser and customer will need to be overcome.

When satisfied the measurements are accurate, record them carefully, ensuring that the heights are enough to allow for the minimum depth of the chosen lens.

Tips For Successful Progressive Lens Dispensing:

1. Ensure that you choose a frame that has adequate depth and that the temples can be adjusted for pantoscopic angle.
2. Ask lifestyle questions and choose the correct progressive lens type and fitting height.
3. When dispensing Free Form progressives there is no need to be concerned with the previous "non-freeform" progressive being worn -the vision with Free Form will always be superior to standard manufactured progressive lenses.
4. Check adjustment of old spectacles.
5. Upon delivery ask your client to read the reading chart in a low or raised position. Then, ask your client to view a distance point in a low position. This will educate them on how to adjust their direction of view using progressive lenses.
6. Recommend Free Form progressive lenses for improved vision and comfort.

How does Your PAL Measure Up?

Progressive lenses will not work well if the correct measurements are not taken accurately or if the measurements are not in-sync with the method that your laboratory is using. Follow these five steps for successful lens dispensing:

Step 1: Frame Selection & Adjustment

• Select a frame which is suitable for progressive lenses and offers adequate height from the PD to the lower rim of the frame - refer to Step 3.
• Adjust the frame to fit your client comfortably and ensure that the pantoscopic angle of the temples is adjusted in the region of 10 to 15 degrees.

Step 2: Measuring the PDs

• The easiest method to ensure accurate individual PD measurements is by using a Pupillometer.
• Utilising the Pupillometer; measure each eye individually with both eyes open. Dot the pupil positions.
• The Pupillometer is extremely accurate as it measures the distance between the visual axes rather than just the distance between the pupil centres (Ref: David Wilson).

Step 3A: Correct Reference Points for Heights

The internationally accepted reference points for measuring progressive lens heights are:

• Deepest point of lens shape at peak of bevel -preferred (box measurement) - Refer Step 4
• Horizontal centerline (datum) - also accepted internationally.
• Ensure at pupil point that there is adequate depth for the progressive corridor length centres (Ref: David Wilson)

Step 3B: Correct Reference Points when ordering Progressive Lens Heights

• To avoid problems you should recognise and utilise the box measurement as described in Step 3A and detailed in Step 4.
• Heights at PD can cause problems when frame shapes have nasal cutaways e.g. teardrop or when PD's are different! (Ref: A J Hanks)

Step 4: Example of Box Measurement of Spectacle Frames

(Ref: A J Hanks)

Step 5: Centration Chart

• Lay the frame face down on the Centration Chart and position the ink marks (PD dots) on the "0" line.
• The horizontal position of the frame is not important for heights.
• Read the heights at the bevel on the deepest point in the box measurement. - Ref: A J Hanks

Part 6 of the Basic Lens Dispensing series has been reproduced with kind permission from the ODMA. This article appeared in the ODMA Optical Retailers Guide, in the Education and Training section, under the heading of ‘Basic Lens Dispensing Part 6'.

Independent practitioners, who would like to receive a copy of the ODMA Optical Retail Guide, should contact ODMA on E: marketing@odma.com.au

Paul Stacey is the General Manager of Smyth & Perkins. He has extensive experience in the optical industry, which has included retail, manufacturing and wholesale environments. He was appointed to the ODMA executive in 2000. He heads up the ODMA Education Committee and is the State ODMA representative for Queensland.