The effect of curcumin on ocular growth and refractive development in guinea pigs

Objective To determined if curcumin affects refractive development and provides guidance for clinical application. Methods In this experimental study, 3-week-old pigmented guinea pigs were divided into two groups: normal control (N) and form deprivation myopia (FDM). In each group, the animals were sub-divided into control (N: n=13, FDM: n=12), vehicle-injected (10% DMSO, N: n=13, FDM: n=13), 15 μg/100 μl curcumin-injected [in 10% DMSO, (N: n=17, FDM: n=17)], or 150 μg/100 μl curcumin-injected [in 10%DMSO, (N: n=15, FDM: n=15)] subgroups. Curcumin dissolved in 100 μl vehicle (or vehicle alone) was administered monocularly by periocular injection into eyes of the designated groups daily. Refraction and axial parameters were measured before treatment and at 2 and 4 weeks after treatment. Scleral collagen Ⅰ was quantified by Western blots 2 weeks after treatment. Data between right and left eyes were analyzed using paired t-tests, and among different groups using one-way ANOVA. Results There was a dose-dependent myopic shift in refraction following daily periocular injection of curcumin. After 4 weeks, the refraction values for each group were as follows: N+ DMSO [-0.37±0.38 diopter (D)] vs. N+15 μg curcumin (-1.62±1.63 D) vs. N+150 μg curcumin (-3.90±1.79 D) (F=21.510, P<0.001). The axial length (AL) were similarly elongated in a dose-dependent manner: 0.01±0.03 mm vs. 0.04±0.05 mm vs. 0.07±0.06 mm respectively (F=4.992, P=0.011). In addition, after 4 weeks of curcumin treatment, there was a dose-dependent enhancement of FDM (FDM+DMSO vs. FDM+15 μg curcumin vs. FDM+150 μg curcumin: -7.81±3.24 D vs. -8.99±3.12 D vs. -10.93±1.96 D respectively, F=4.425, P=0.018). AL was similarly elongated in FDM eyes, but without significant differences. Furthermore, injection of 150 μg curcumin reduced scleral collagen Ⅰ expression (fellow eyes vs. treated eyes: 0.33±0.08 vs. 0.18±0.03, t=-2.305, P=0.043). Conclusion Periocular injection of curcumin induces myopia and enhances FDM in pigmented guinea pigs, probably by reducing expression of scleral collagen Ⅰ. Key words: Curcumin; Myopia; Form deprivation myopia; Collagen