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MINWOOK CHANG, Jae Rock Do, Youngseok Lee, Sehyun Baek; The Functional and Histopathological Change in the Levator Palpebrae Superioris and Müller's Muscle after Subconjunctival Injection of Triamcinolone Acetonide in Rabbits. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4455.
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The aim of this study was to evaluate the functional and histopathological changes in the levator palpebrae superioris and Müller's muscles after subconjunctival injection of triamcinolone acetonide (TA) in rabbits.
Twenty-four white New Zealand rabbits were divided into two groups. In group A, a subconjunctival injection of 0.5 cc TA (40 mg/cc) was administered to the right eye, while a normal saline injection of the same volume was administered to the left eye. In group B, the same procedures were done with a 1.0 cc injection of TA or normal saline into each eyelid. Follow-up was done to evaluate the histopathological changes in the levator and Müller's muscles, changes in the mean transectional area of Müller's muscle, and changes in upper lid height (MRD1) at one, two, four and six weeks after injection. Western blot analyses were used to determine the levels of myosin light chain phosphorylation (MLC-p) and alpha smooth muscle actin (a-SMA), which are related to the contractility of Müller's muscle.
No specific changes in MRD1 were noted in either group A or B. No significant histopathological changes were found in the levator muscles. However, significant atrophy and thinning of Müller's muscle were found, and MLC-p and a-SMA levels were decreased. This was consistent with the histological changes of Müller's muscle observed in rabbits that received a TA injection. These changes were reversible and influenced by the volume of the injection.
Subconjunctival injection of TA into the upper eyelids appears to be temporally influential on both the functional and histopathological changes of Müller's muscle. This may be explained by the effect of improvement in lid retraction regardless of the minimal specific change observed in the levator muscle.
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