Toric Multifocal Contact Lens Design: Case Study

Pupil Size Matters

With more patients inquiring about toric multifocal contact lenses, more practitioners are interested in how to achieve stress-free, successful toric multifocal contact lens fittings. We at SpecialEyes know one of the critical factors that contributes to successful multifocal contact lens fittings is pupil size and the manner in which multifocal optics are distributed over a patient’s pupil diameter. The case study below, demonstrates how our pupil size fitting methodology, via the Multifocal Simulator, can give practitioners prescribing the SpecialEyes 54 Multifocal a unique advantage.

Case Study

An eye-care practitioner contacted SpecialEyes and requested we design custom toric multifocal contact lenses for one of his astigmatic presbyopic patients. The SpecialEyes consultant designed the base curve, diameter, and power of the toric multifocal contact lenses via the Arc Length Contact Lens Calculator. The practitioner provided an approximate pupil size measurement of 4mm which was used to design the multifocal optic zone sizes utilizing the SpecialEyes Multifocal Simulator. The trial contact lens parameters were as follows:

SpecialEyes 54 Multifocal Trial Contact Lenses:

OD: 8.3 base curve | 14.8 diameter +0.75 -1.00 x176 +2.25 add
2.0mm near center zone and 3.5mm peripheral zone

OS: 8.6 base curve | 14.9 diameter +0.50 -1.00 x173 +2.25 add
2.0mm near center zone and 3.5mm peripheral zone

Once the fit of the trial contact lenses was honed in, it was then time to evaluate vision. After an adaptation period, the patient was happy with his near vision but distance visual acuity was 20/30 and needed improvement. The consultant asked about the approximate pupil size measurement and asked if a more precise measurement could be taken in regular room illumination. The practice reported back that the pupil size was actually 3.5mm in regular room illumination.

The SpecialEyes Multifocal Simulation in Image A represents the trial toric multifocal contact lenses (2.0mm near center zone and a 3.5mm peripheral zone) based on the patient’s accurate pupil measurement of 3.5mm. The image to the far left represents distance vision and you can see that the image is somewhat degraded and blurred.

Action:

To resolve the distance visual acuity complaint, the peripheral zone was decreased from 3.5mm to 3.0mm. This places more distance optics over the pupil diameter area and thus improves distance visual acuity. The SpecialEyes Multifocal Simulation in Image B represents the second set of trial multifocal contact lenses with the reduced peripheral zone. As you can see, the far left image representing distance vision is much clearer and exhibits less blur compared to image A.

Image A

Image B

Results:

The simulated images provide us guidance when fitting the custom SpecialEyes 54 Toric Multifocal contact lenses, but the truth lies in the patient response. The patient returned to the practice to try the redesigned toric multifocal contact lenses based on an accurate pupil size measurement of 3.5mm. Although final visual acuity results were not reported to us, we can tell you that 3 weeks later the practice called to order the remaining lenses for his year supply.

So, if you decide to fit SpecialEyes’ custom toric multifocal, make sure to measure pupil size as accurately as possible and communicate that information to SpecialEyes upon initial lens design.

Want more information on the SpecialEyes 54 Multifocal Toric? Click the Learn More button below.

Happy Fitting!