Effects of direct intravitreal dopamine injections on the development of lid-suture induced myopia in rabbits
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- Gao, Q., Liu, Q., Ma, P. et al. Graefe's Arch Clin Exp Ophthalmo (2006) 244: 1329. doi:10.1007/s00417-006-0254-1
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Dopamine (DA) storage and release are reduced in form deprivation myopia (FDM) in a wide range of species, from chicks to primates. FDM can be prevented by treatment with DA agonists such as apomorphine, and paradoxically by the dopamine neurotoxin 6-hydroxydopamine. In this study, we increased the DA levels by direct intravitreal DA injections to learn if FDM can be suppressed in a rabbit model.
Seven-day-old rabbits were deprived of pattern vision by the suturing the right eyelids after natural eye opening. In the first group (FD, n=20), the right eye received form deprivation (FD) alone. In the second group (DA-FD, n=16), the deprived eye of 7-day-old rabbits received four intravitreal injections of 20 μg dopamine every 5 days. In the third group (saline-FD, n=16), the deprived eye received saline injections with the same schedule. The contralateral eye remained untreated as a control. At the end of the 8-week deprivation period, the effects of DA on refractive error, corneal curvature and ocular dimensions were assessed by streak retinoscopy, keratometry and A-scan ultrasonography, respectively.
Eight weeks of FDM induced a myopic shift of −2.70±0.87 D (n=20) in treated eyes compared with contralateral eyes. The major structural correlate of the myopia appeared to be elongation of the vitreous chamber (0.7±0.3 mm, n=20) and axial elongation (0.9±0.3 mm, n=20), respectively. Repeated intravitreal injections of DA fully prevented the myopic shift (−0.06±0.37 D), elongation of the vitreous chamber (0.1±0.3 mm, n=16) and axial elongation (0.3±0.2 mm, n=16) due to lid suture, whereas saline injections had slight effect.
FD by suturing eyelids is an effective technique to induce a significant myopic shift, vitreous chamber and axial elongation in rabbits as a model of myopia development. These changes associated with FD were retarded by intravitreal injections of DA.