Presbyopia - A Simultaneous Solution
Michael Baertschi, MSc Mmed Education FAAO
Michael Wyss, MSc FAAO
Simon Bolli, Eidg dipl Augenoptiker
Marc Fankhauser, Eidg dipl Augenoptiker
Correcting presbyopia with a simultaneous system can provide some benefits for your patient compared to translating (R)GP designs, including meeting reading demands in more positions of gaze, better comfort and improved intermediate vision for computer work. However, simultaneous vision can be difficult for your patient to adapt to and can be difficult for you during the fitting process. In the next few contributions to I-Site newsletter, we will highlight fitting pearls for simultaneous systems to make presbyopia lens fitting with these systems more successful.
Multifocal designs generally provide distance and near vision optics with an additional transition zone between those corrections for intermediate vision (see Figure 1).
Figure 1: Multifocal Design with Distance Center
Because several corrections are presented to the brain, contrast vision will be decreased. To improve contrast vision, first reduce the near addition on the dominant eye - sometimes to the point of providing only distance correction for that eye. Second, change the zone diameter of the lens depending on the vision demand preferred. Finally, change the design from a distance center (DC) to a near center (NC). Due to the manufacturing process used, changing an NC lens to a DC lens with an identical zone diameter results in different amounts of distance vision provided through the optical portions of the lens.
The following case report will further explain this modality.
Our patient was a 52-year-old Caucasian male who had been a successful (R)GP lens wearer since the age of 16. After he developed presbyopia, he was successfully fitted with a perilimbal (diameter 11.20mm) simultaneous (R)GP NC (diameter 2.7mm) lens design. As the reading addition increased with age, distance vision began to cause eye strain for the patient, especially at night. Lowering the near addition to overcome this led to unacceptable near vision. The next step was to change the NC 2.7mm design to a DC 3.3mm diameter ring. The reason for the bigger DC zone diameter was to gain more of the pupil area, as further explained in Figure 2.
Figure 2: Comparing NC and DC lens designs regarding the remaining percentage of distance optics
NC designs are manufactured by having a near correction over a certain area in the center of the lens, after which the distance area is created by gradually lowering the addition to zero. The same procedure is used to manufacture DC designs, which will lead to a somewhat smaller distance area than that in the NC design. In the example used in Figure 2, the DC variant would provide only about one half the distance area compared to that of the NC design, despite the identical zone diameter. This is an important feature for ECPs to know, as otherwise the goal (better distance visual acuity) will not achieved. And more importantly, the patient could lose confidence in the system and/or the skills of the ECP if such variables are not taken into account.
In our example, the patient had much better distance visual acuity with the new lens, while maintaining good reading performance. This will also allow us to increase the near addition slowly in the future if needed.
It is essential to know the contact lens design used in detail so you can be creative and find the best solution for any specific presbyopic patient. This is the only way to accurately and precisely fit simultaneous multifocal designs. Otherwise it is more of a ‘trial-and-error’ process, which could result in additional chair time and costs as well as extra appointments for your patient and potential loss of faith in the system or practice.
Michael Baertschi was the senior optometrist at the University Eyehospital Basel from 2000 to 2007. He is the owner of Kontaktlinsenstudio Baertschi in Bern, Switzerland and the CEO of Eyeness AG in Bern. Michael graduated from Pennsylvania College of Optometry as M.Sc. Optom. and from the University of Bern as M.med. Educ. Michael Baertschi is a fellow of the American Academy of Optometry and president of the Swiss Interlens group.
Michael graduated from Olten SHFA in Switzerland and did his MSc at the Hochschule Aalen Germany (in cooperation with New England College of Optometry and Pacific University, USA). Since 1999 he has worked in a private practice (kontaktlinsenstudio Baertschi in Bern, Switzerland) as Optometrist for specialty contact lens fitting. Additionally, he is an adjunct Faculty Member at the New England College of Optometry USA, Hochschule Aalen Germany, TVCI in Prague (Czech Republic) and FHNW Optometry in Olten Switzerland. Michael is a clinical investigator for several Industry Partners and has published or lectured on several topics in the contact lens field throughout the world. Michael is a Fellow of the American Academy of Optometry and serves as a the vice chairman of the Admittance Committee for new Fellows outside the USA.