Michael Baertschi, MSc Mmed Education FAAO
Michael Wyss, MSc FAAO
Simon Bolli, Eidg dipl Augenoptiker
Marc Fankhauser, Eidg dipl Augenoptiker
Presbyopia combined with a high amount of astigmatism is often recognized as a challenge in contact lens practice. This is especially true if the astigmatism is oblique. Translating (R)GP designs generally provide fantastically clear images for distance and reading purposes. However, if the reading portion rotates temporally while the patient is reading, visual acuity will be reduced and patients often complain about seeing shadows while reading. This case report will concentrate on a translating (R)GP lens design and will provide an important fitting pearl for oblique astigmatic cases.
Our patient was a 48-year-old Caucasian female with a high amount of oblique astigmatism. She had been wearing (R)GP lenses for 22 years. During the last few years she had suffered from increased presbyopia and, therefore, complained about difficulty with reading. We will concentrate on her left eye for this case report to keep it simple. Topography OS showed astigmatism of 3.6D at a 30° axis (Figure 1).
Figure 1: Topography OS showed 3.6D of astigmatism at a 30° axis.
Figure 2: Translating back toric (R)GP OS, perfectly locked into the corneal astigmatism at 30°.
A standard translating (R)GP lens with a back-toric design locked in perfectly along the corneal astigmatism at 30° (Figure 2). But this resulted in a temporally rotated near segment, which clearly made it difficult for the patient to “access” the reading portion, especially when the eyes were converging. Additionally, due to the prism ballast used at 270° for the translating effect of the (R)GP design, the lens would rotate from 30° after blinking toward 180°, which would lead to spectacle blur and unstable visual results and also would make the lens uncomfortable to wear.
To overcome this rotation problem, the final (R)GP lens was made with an optimized back-toric design and, more importantly, a shifted prism ballast toward 300°. Prism ballast is marked on the lens with an additional engraving. Consequently, the reading portion was accordingly shifted 30° as well. (Figure 3)
Figure 3: Translating back-toric (R)GP with rotated near segment.
Now the (R)GP lens still perfectly locks in at the same astigmatism axis of 30°, while the reading portion perfectly positions at 270°. Additionally, the (R)GP now only moved vertically without any rotation, which led to a comfortable wearing time with stable and precise visual performance.
Summary & Discussion
Creativity is the keyword here, especially when dealing with special corneal conditions. Astigmatic correction with (R)GP designs provides fantastic image quality. This is especially important in presbyopia. All of the other contact lens options on the market have their compromises when our astigmatic patients develop presbyopia. Good observation of the fitting and consequent lens modifications made together with your lab can sometimes really open a new world for your (presbyopia) patients.
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 Member of the Admittance Committee for new Fellows outside the USA.