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A. Ho, L. Donovan, V. Fernandez, T. Hughes, X.–W. Zhong, E. Smith, J. Ge, J.–M. Parel, B. Holden, The Vision CRC Dynamic Vision Team; Accommodation in a Live Primate Model Following Phaco–Ersatz . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5891.
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Phaco–ersatz (lens capsule refilling) has been proposed as a surgical technique for restoring accommodation in presbyopes. Early experiments with commercially available silicone oils have demonstrated feasibility. However, those materials have inherent disadvantages (e.g. leakage into the anterior chamber). We tested the short–term accommodative response following refilling of the lens with a custom–developed polymer gel in an on–going study using a live primate model.
Bilateral total iridectomy was performed on six rhesus monkeys (5–6 years of age) at the ZhongShan Ophthalmic Center primate facility. Pre–op accommodative amplitude (AA) was evaluated in both eyes using a Nikon Retinomax auto–refractor, as the difference in refraction between the unaccommodated and accommodated states. Accommodation was induced by subconjunctival injection of pilocarpine HCl (0.5% or 1%). Phaco–ersatz was performed on the right eye following the technique described by Tahi & Parel (JCRS, 1999). Following hydrodissection and aspiration of the lens material via a small capsulorhexis (0.8–1.2 mm diameter), a mini–valve was inserted through the capsulorhexis to prevent polymer leakage. The evacuated capsule was then refilled with a custom–developed siloxane–based polymer, which was crosslinked in situ using blue light (400–500 nm, for 30 or 60 seconds irradiation at 153 mW.cm–2). The AA for both eyes was evaluated at post–op days (POD) 1, 3 and 5 or 7.
Median pre–op AA were 11.0D (range 7.5D to 14.2D) and 11.7D (range 7.6D to 13.0D) for the right and left eyes respectively. The median AA over all POD were 12.8D (range 7.6 to 16.0D) and 7.6D (range 5.0 to 12.8D) for the control and experimental eyes respectively. Since the level of accommodation induced may vary between occasions and animals, a Relative Amplitude of Accommodation (RAA) expressed in percentages was calculated as the ratio of accommodative amplitude in the refilled eye to that of the control eye. The median RAA was 60% (range 43% to 82%).
The efficacy of a custom–developed gel for restoring accommodation following phaco–ersatz has been demonstrated in a live primate model.
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