Before pulling a single lens from your diagnostic set, pick up your PD ruler.
This humble, low-tech tool does more than measure pupillary distance. When used thoughtfully, it can give you valuable clues about lid position, visible iris diameter, pupil size, and even blink dynamics—all of which influence lens selection and success.
Take a moment to assess horizontal visible iris diameter and lid-to-limbus positioning. Are the lids riding low? That could spell trouble for multifocal centration. Is the iris size larger than average? You may need a larger diameter GP or consider how edge lift will interact with the scleral landing zone. Even pupil size under room lighting can help you anticipate whether that center-near multifocal will deliver clear vision at both distances.
It’s also a great educational tool. Patients respond well when you demonstrate that you’re customizing the fit to their anatomy and not just grabbing a box off the shelf.
Try using the PD ruler as your first diagnostic tool in the contact lens exam. It adds less than a minute to your workflow but can save you multiple remakes or frustrated follow-ups. Keep it in your pocket. It deserves a spot in your fitting process, right next to your topographer.
I hope you’ve found inspiration from this series to find other simple, low-cost tools in addition to your PD ruler, Lissamine green strips, the fenestrated DMV plunger, and the white tissue test to elevate your contact lens practice.