Every practitioner who has fit soft toric multifocal contact lenses has experienced some degree of frustration in reaching the ultimate goal of 20/happy. During fitting, you may find that the toric multifocal contact lenses have optimal fit and alignment, refraction is accurate, the patient takes no over refraction, yet the patient still desires better vision. What could be causing this roadblock? SpecialEyes has found that the performance of multifocal contact lenses can be attributed to the manner in which the multifocal optics are distributed over the area of the patient’s pupillary diameter.
Fortunately, as mentioned previously, with SpecialEyes 54 Toric Multifocal contact lenses practitioners have the ability to customize and control the multifocal optic zones. By altering the multifocal zones, you will simultaneously change the area of near, intermediate, and distance optics placed over the pupil, as well as, the rate at which the power progresses from one power in the center of the lens to the opposite power in the periphery of the lens.
When addressing a multifocal contact lens patient’s chief visual complaint via a multifocal zone change, the patient’s pupil size is an important factor. Please feel free to reach out to the SpecialEyes consultation team for troubleshooting assistance or any questions you may have in regard to multifocal zone changes as it relates to pupil size.
The following scenarios demonstrate appropriate multifocal zone changes in relation to the patient’s pupil size and chief visual complaint. For simplicity’s sake, let’s assume that both of the following patients have identical refractive errors, pupil sizes, and lens designs. The only difference is their chief visual complaint.
Trial SpecialEyes 54 Toric Multifocal Contact Lenses
(aspheric design – near center lenses OU)
OD: 8.2 Base Curve 14.6 Diameter -3.00 -1.00 x180 +1.50 Add Power
2.0 Near Center Zone, 4.0mm Peripheral Zone
OS: 8.2 Base Curve 14.6 Diameter -3.50 -1.50 x180 +1.50 Add Power
2.0 Near Center Zone, 4.0mm Peripheral Zone
Pupil Size: 4.0mm in regular room illumination
Distance Visual Acuity: 20/30
Near Visual Acuity: J1+
Case Scenario #1: Pupil Size of 4.0mm in Regular Room Light
A myopic astigmatic presbyopic patient desires contact lens vision correction and is fit in a trial SpecialEyes 54 Multifocal – aspheric design. The patient’s pupils measure 4.0mm in regular room light. The patient’s chief complaint is that his distance vision could be sharper.
Resolution: In this scenario, to improve the patient’s distance vision we must dedicate a larger area to distance optics over the pupil diameter area. Taking into consideration the patient’s pupil size of 4.0mm this would be accomplished by decreasing the peripheral zone diameter value to 3.5mm from 4.0mm. Making the peripheral zone smaller will place more distance optics over the patient's pupil area and improve the patient’s distance vision. It’s worth noting that when making changes to the peripheral zone, the minimum amount of recommended change is 0.50 mm.
Case Scenario #2: Pupil Size of 4.0mm in Regular Room Light
A myopic astigmatic presbyopic patient desires contact lens vision correction and is fit in a trial of the SpecialEyes 54 Multifocal – aspheric design. The patient’s pupils measure 4.0mm in regular room light. The patient’s chief complaint is that her intermediate vision could be sharper.
Resolution: In this scenario, to improve intermediate vision we need to decrease the rate at which the power progresses within the progressive zonal area. We can accomplish this by either decreasing the near center zone diameter value or increasing the peripheral zone diameter value. Deciding which zone to change has to be done in conjunction with pupil size assessment, current zone sizes, and visual acuity. The patient's visual acuity was 20/30 at distance and J1+ at near and the near center zone size in the original lens was 2.0mm and the peripheral zone size was 4.0mm. In this situation, I would decrease the near center zone diameter value to 1.8mm to improve the patient's intermediate vision. This will decrease the area of near optics, potentially taking away from near slightly, but will decrease the rate at which the power progresses, thus improving intermediate vision, which was the patient's main complaint. Since the patient's visual acuity at near was J1+ we had leeway to take away a bit from near to correct the patient's main complaint of desiring better intermediate vision. If we had tried to improve intermediate vision by increasing the peripheral zone we most likely would have improved intermediate vision but at a cost of decreasing distance visual acuity beyond the 20/30. This decrease in distance visual acuity would have happened because we would've placed the distance optics outside the pupil diameter area. Increasing the peripheral zone in this scenario would have been a detriment to the fitting and the patient wouldn't have been functional at distance.
Conclusion: Any change made to a multifocal optic zone should be made in relation to the patient’s pupil size. The next time you are ordering a SpecialEyes 54 Toric Multifocal, take a moment to measure the patient’s pupil size and be sure to share that information with the fitting consultant and they can help guide you to the perfect multifocal contact lenses.
Korinne Andrew is a Customer Service Representative at SpecialEyes. She has been with the company since 2012 and has developed a keen knowledge of the company’s products as well as expertise in fitting custom toric, sphere, and multifocal contact lenses.