Retinoic Acid Reduces Ocular Elongation in Chicks with Form‐Deprivation Myopia

Purpose. Retinoic acid (RA) has been proposed to be of value in treating myopia, as it affects scleral growth in chicks with form‐deprivation myopia. The present study aimed to test the effects of RA injection on a form‐deprivation myopia (FDM) model in chicks. Methods. The chicks were form‐deprived by having a black goggle sutured over one eye with the contralateral eye as the control. Daily intraperitoneal injection of all‐trans RA was performed for 12 days. The eye weight (EW), ocular length (OL), equatorial diameter (ED), and the thickness of retina and sclera were measured to reflect the effects of RA on ocular development under form‐deprivation myopia. Results. The effect of RA was biphasic with alleviating effect on FDM limited to a daily dose of up to 10 µg/day with relatively less myopic development than the controls. Significant differences of EW and OL, but not ED, at 10 µg/day RA (P < 0.05) were observed. The thinning of retina and the thickening of sclera as a result of FDM were reversed, albeit not significantly, in the presence of RA up to a daily dose of 10 µg/day. Conclusions. The results show that exogenously applied RA has the potential to inhibit scleral growth in form‐deprived chicks. Such findings are in line with the understanding that regulation of scleral growth is one of the key factors in myopia, and RA may be of value in its treatment.