2.  Gradually increase in power ◦ Upper portion = distance power ◦ Downward & inward = near power ◦ Inbetween is a progressive corridor where the lens power is gradually changing

3.  Must make sure there’s enough room for the progressive zone and near portion  Can be unintentionally cut off if frame too small ◦ Must have enough vertical depth ◦ There’s a minimum fitting height from the manufacturer – usually around 18mm ◦ There are smaller “short corridor” PAL’s for smaller frames

4. ◦ Must have enough frame in lower nasal portion  Watch out with aviator shapes ◦ Short vertex distance  When frame is closer, there’s a wider depth of field ◦ Must be able to add pantoscopic tilt of 10-12 degrees

5.  What type of PAL is appropriate?  Does the patient have a lot of astigmatism?  Do you need a short corridor PAL?  Does the patient use the computer a lot?  In general, what are their work needs (and distances used?)

6.  Corridor is narrow ◦ Use monocular PD  Fitting cross ◦ Usually 4 mm above corridor

7.  Hidden markings ◦ Add power is engraved 4mm below a temporal symbol, sometimes above  Manufacturer usually 4mm below nasal hidden circle ◦ Use a black background ◦ Used fluorescent bulbs ◦ Use instrument designed to make markings show up

8.  Monocular distance PD  Fit & fully adjust the exact frame that will be used  If no lenses in frame, put clear tape across eyewire  Be at eye level with patient ◦ Patient looks at dispenser’s nose ◦ Draw line through center of pupil for both eyes ◦ Put frame on manufacturer’s centration chart

9.  Horizontal pupil lines should be on chart’s horizontal axis  Mark PD as vertical line