Custom Multifocal Optics for Toric Multifocal Contact Lens Patient
SpecialEyes advises eye-care practitioners to always take pupil size into account when designing and prescribing a custom multifocal contact lens. In the case below, SpecialEyes helped a practitioner design custom toric multifocal contact lenses for an astigmatic presbyopic patient. The patient was a more advanced presbyope with a refractive add power of +2.25.
OD: +4.25 -1.50 x109
OS: +4.50 -1.75 x080
Add: +2.25 OU
During the initial lens design, our consultant requested the patient’s pupil-size measurements to ensure optimal design of the multifocal optics. Unfortunately, that information was not available at the time of the consultation.
Given the absence of pupil-size measurements, the SpecialEyes consultant used a standard approach to the multifocal optics and designed the custom multifocal toric contact lens with a 2.0mm near-center zone and a 4.0mm peripheral zone.
Explanation of Multifocal Zone Sizes: The 2.0mm near-center zone is the diameter value across the center of the lens where the full near optics are located. At the edge of this near-center zone, the lens starts to transition (or progress) in power. This transitional area is where the intermediate optics are located. The 4.0mm peripheral zone is the diameter value that represents the point in the lens at which full distance power is reached. From the 4.0mm peripheral zone diameter value, the lens remains at full distance power throughout the remainder of the optic zone.
SpecialEyes 54 Toric Multifocal Contact Lens Trial #1:
OD: 8.0 Base Curve/14.6 Diameter +4.50 -1.75 x109 +2.25 add
OS: 8.1 Base Curve/14.6 Diameter +4.75 -2.00 x080 +2.25 add
Multifocal Optics: 2.0mm near-center zone/4.0mm peripheral zone
Chief Complaint: Poor distance vision: 20/50 OU. When the patient returned to the office for the trial lens fitting, the practitioner was able to obtain a pupil-size measurement of 4.0mm in regular room illumination.
Action: Redesign the multifocal optics based on the patient’s pupil size. The peripheral zone was decreased from 4.0mm to 3.5mm OU to improve distance vision. No other contact lens parameters were altered. The simulated images below provide a visual representation of the potential performance of both lens designs based on a 4.0mm pupil measurement in regular room illumination.
Simulated Images Representing Contact Lens Trial #1:
Interpretation: The far-left image represents distance vision, the far-right image represents near vision, and the images in between represent intermediate vision. As you can see in the far-left image of Simulation #1, distance vision is blurred and degraded. The patient’s distance visual acuity (DVA) with this toric multifocal contact lens design was 20/50 OU.
Simulated Images Representing Contact Lens Trial #2 With Peripheral Zone Change:
Interpretation: As the far-left image of Simulation #2 demonstrates, decreasing the peripheral zone to 3.5mm enhanced distance vision significantly. The patient’s distance vision improved from 20/50 OU with the trial lenses to 20/25 OU with the second set of toric multifocal contact lenses.
Outcome: Decreasing the peripheral zone OU improved the patient’s DVA from 20/50 to 20/25, while NVA remained at 20/25. The patient was happy with the new toric multifocal contact lens design and the practitioner ordered an annual supply of lenses.
Conclusion: Pupil size really does matter when designing and prescribing a custom multifocal and toric multifocal contact lens. As shown in the simulation examples above, accurate pupil size measurements are critical to the initial design of the 54 Multifocal and when altering zone sizes to improve visual acuity. Click here to request a SpecialEyes Ruler.