Abstract
Purpose :
To further elucidate the structures involved with the accommodative mechanism and presbyopia.
Methods :
In 14 rhesus monkeys (ages 6-23 yrs), maximum accommodative responses were induced by electrical stimulation of the E-W nucleus. Ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz) and endoscopy images were collected in the region of lens, ciliary muscle, zonular attachments and vitreous during the accommodative response. Images were collected before & after intra- or extracapsular lens extraction (ICLE, ECLE). Various contrast agents (i.e., triamcinolone) were used to enhance visualization of the intraocular structures and fluid movements during accommodation.
Results :
Following ICLE, with no capsule or anterior zonular attachments to the ciliary processes (CP), CP movement velocity (0.28±0.13mm/sec; mean±sem) is reduced compared to the normal phakic eye (0.92±0.13mm/sec). Following ECLE with zonular attachments to the capsule and Wieger’s ligament remaining, CP movement velocity is increased slightly compared to the normal phakic eye. Following ICLE, with no zonular attachments to the capsule and only zonular attachments between the CP and Wieger’s ligament remaining, CP movement velocity is still robust (0.97±0.13 mm/sec).
In the normal phakic eye, continuous vitreous strands that extend from the posterior retina and attach to the pars plicata and to the pars plana were newly visualized (UBM and endoscopy) and these strands move centripetally in concordance with the accommodative response. The anterior aspect of the vitreous lacunae, which extend from the central vitreous and attach peripherally to the vitreous zonule, contributes to the anterior hyaloid. The anterior hyaloid bows backward during accommodation and the compartment inside the lacunae narrows by 0.27±0.03mm. The lacunae could be part of the cistern structure reported by Jongbloed WL Doc Ophthalmol 1987.
Conclusions :
The CP velocity data suggest that centripetal muscle movement can be robust in the absence of the lens/capsule so long as the zonular attachments between the CP and Wieger’s ligament are intact. The vitreous and the accommodative apparatus exhibit numerous interconnections throughout the eye – front to back (i.e., pars plicata, pars plana, retina) and may have implications for accommodation, fluid dynamics, presbyopia and glaucoma.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.