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Mary Ann Croft, T M. Nork, Jared P. McDonald, Alexander Katz, Paul L. Kaufman; The Vitreous Membrane Relaxes During Accommodation: Lens And Extralenticular Accommodative Factors. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6677.
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To elucidate the accommodative function of the vitreous membrane (anterior hyaloid) with respect to the ciliary body, lens, and zonular attachments at rest and during accommodation in rhesus monkeys.
The eyes of 4 rhesus monkeys (aged 4-12 yrs) were studied. Central Electrical stimulation of the Edinger-Westphal (E-W) nucleus was used to induce maximum accommodative responses. Ultrasound biomicroscopy (UBM; 50 MHz, 35 MHz) images were collected in the region of the vitreous membrane, ciliary body, lens, and zonular attachments. Fluorescein dye (50 µl of 0.02%) or Triesence (50 µl, triamcinolone acetonide), both of which bind or cling to collagen in the vitreous membrane, was inserted into the monkey vitreous to facilitate visualization of the vitreous membrane by endoscopy (Endo Optiks) or UBM, respectively. The anterior vitreous membrane and the entire extent of the ciliary body, zonula, and the anterior and posterior surfaces of the lens were imaged before and during accommodation.
The Triesence and fluorescein adhered to the vitreous membrane and allowed visualization of the vitreous membrane function by UBM and endoscopy during accommodation. The vitreous membrane relaxed during accommodation in the region between Weiger’s ligament and the point where the membrane splits from the vitreous zonule. The membrane began to relax beginning 0.3 sec following stimulus onset at a time when ~0.1 mm of both accommodative centripetal lens equator and muscle movement has occurred, and ~0.1 mm of both forward vitreous zonule and muscle movement has occurred. Based on the above observations and the qualitative assessment of the dynamic accommodative movements imaged by UBM, the relaxation of the vitreousmembrane appeared to be dependent upon centripetal and forward movement of the muscle and vitreous zonule. When the stimulus was discontinued, the vitreous membrane was pulled back into a straight course [by the vitreous zonule and muscle relaxation] and became taut, restoring tension to Weiger’s ligament and the posterior lens surface. This phenomenon was observed in both the nasal and temporal quadrant.
The vitreous membrane plays a role in the flattening of the posterior lens surface during disaccommodation. During accommodation, the vitreous membrane relaxes, which allows the posterior lens surface to increase in curvature.
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