Abstract
Purpose: :
Potential signaling pathways involved in the development of myopia are largely unknown even though many candidate molecules have been proposed to be involved in this process. The purpose of this study was to determine the possible role of vasoactive intestinal peptide (VIP) in experimentally induced myopia in chicks.
Methods: :
Three groups of 6-day-old white Leghorn chicks wore a unilateral translucent hemispherical plastic diffuser that is known to induce myopia in their right eyes. The first group was the control group that received nothing. The intravitreal injections were applied into the occluded eyes in groups 2 and 3. The intravitreal injections of 10 μl of saline and 10 μl of VIP (0.5 ng/μl) were applied in group 2 and 3 respectively every 24 hours for 7 days. On the first and eight days of the experiment the refraction was assessed with retinoscopy and the axial length (AL) by A-scan ultrasonography. After the final measurements, the weight and volume of the enucleated right and left eyes were noted. Statistical analysis was performed using nonparametric tests (p<0.05=significant).
Results: :
At final examinations, form deprivation myopia (FDM) of high degrees was obtained in groups 1 and 2, whereas the mean final refraction documented in left eyes was 0.6±2.0 0.3±1.8 and 1.3±0.5 in group 1, 2 and 3 respectively. The mean final refraction (D) detected in the right eyes was -13.5±2.7, -9.9±3.6 and -1.8±2.8 in group 1, 2 and 3 respectively. The final myopia obtained was significantly lower in VIP injected eyes (p<0.05). The mean final AL in mm was 10.6±0.6, 9.9±0.2 and 9.2±0.3 in group 1, 2 and 3 respectively. The final AL was significantly shorter in VIP group compared to the other two groups (p<0.05). The volume of the right eyes in VIP group was significantly lower than the volumes in other groups (p<0.05). The right eyes of group 1 weighed more than the right eyes in VIP group (p<0.05), whereas the difference in weights between group 2 and 3 didn’t reach a statistical significance.
Conclusions: :
Eyes injected with VIP were significantly less myopic than the other occluded eyes. VIP seems to have potentially inhibitory effects in the development of FDM.
Keywords: myopia • drug toxicity/drug effects