Purpose: It is known that the fibrous strands of the Zonule of Zinn can be severely affected in people with Marfan Syndrome (MS), which may lead to subluxation of the crystalline lens. We have developed a set of optical techniques to objectively assess the biomechanics of the anterior eye (pupil, crystalline lens or artificial intraocular lens, IOL), and to evaluate their impact on reading performance.
Methods: A dynamic Purkinje-meter based on the high-speed recording of Purkinje images was used to measure the oscillations of lens (or the IOL as appropriate). The oscillations of the iris (iridodonesis) were also quantified. A pupillometer, based on a Raspberry Pi computer was built, using 2 blue LEDs (wavelength 480 nm) to assess the dynamics of the pupillary reflex to a 1-second flash of light. Reading and eye movement performances were assessed using custom developed software integrated with an eye tracker (Eyelink 1000, SR Research Ltd., Canada) in order to obtain the number of saccades performed. Ten sentences extracted from the Minnesota Low-Vision Reading test were read at a font size three times larger than the reading threshold. Three subjects (66, 69 and 75 years old) with MS who had undergone surgery for lens dislocation were examined. Subject 1 had an anterior chamber IOL implant, subject 2 had a posterior chamber IOL implant, and subject 3 was aphakic.
Results: IOL wobbling was very large in subject 2 (posterior chamber IOL) with oscillations lasting for up to 1.5 seconds and amplitudes of 1.7 mm. Subject 1 with the anterior chamber IOL had no noticeable IOL wobbling. Pupil and iris wobbling were clearly observed in subject 3 (aphakia) with the pupil edges displaced up to 0.28 mm after each saccade. Pupillary reflex was faster and stronger in subject 1 (anterior chamber IOL) with a maximum pupillary constriction of 48% compared to subjects 2 and 3 for whom pupillary constriction was 24% and 22%, respectively. Stability of the eye with reading was worse in subject 2 (posterior chamber IOL), showing more saccades (N = 203) compared to subject 1 (N = 144) and subject 3 (N= 122).
Conclusions: A set of methods designed to objectively evaluate the ocular biomechanics of MS patients was successfully tested. This methodology shows promising potential to explore differences in various surgical solutions to treat lens dislocation in people with Marfan syndrome.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 – May 2, 2019.