Anteriorly located zonular fibres as a tool for fine regulation in accommodation.

PubMed ID: 26490669

Author(s): Flügel-Koch CM, Croft MA, Kaufman PL, Lütjen-Drecoll E. Anteriorly located zonular fibres as a tool for fine regulation in accommodation. Ophthalmic Physiol Opt. 2016 Jan;36(1):13-20. doi: 10.1111/opo.12257. Epub 2015 Oct 21. PMID 26490669

Journal: Ophthalmic & Physiological Optics : The Journal Of The British College Of Ophthalmic Opticians (Optometrists), Volume 36, Issue 1, Jan 2016

PURPOSE To describe an anteriorly located system of zonular fibres that could be involved in fine-tuning of accommodation.

METHODS Forty-six human and 28 rhesus monkey eyes were dissected and special preparations were processed for scanning electron microscopy and reflected-light microscopy. Additional series of frontal and sagittal histological and ultrathin sections were analysed in respect to the origin and insertion of anteriorly located zonules. The presence of sensory terminals at the site of the originating zonules within the connective tissue of the ciliary body was studied by immunohistochemistry. For in-vivo visualization ultrasound biomicroscopy (UBM) was performed on 12 human subjects.

RESULTS Fine zonular fibres originated from the valleys and lateral walls of the most anterior pars plicata that covers the anterior and inner circular ciliary muscle portion. These most anterior zonules (MAZ) showed attachments either to the anterior or posterior tines or they inserted directly onto the surface of the lens. At the site of origin, the course of the MAZ merged into the connective tissue fibres connecting the adjacent pigmented epithelium to the ciliary muscle. Numerous afferent terminals directly at the site of this MAZ-origin were connected to the intrinsic nervous network of the ciliary muscle.

CONCLUSIONS A newly described set of zonular fibres features the capabilities to register the tensions of the zonular fork and lens capsule. The close location and neural connection towards the circular ciliary muscle portion could provide the basis for stabilization and readjustment of focusing that serves fast and fine-tuned accommodation and disaccommodation.