High Myopia Induced by Bilateral Form Deprivation Is Highly Synchronized in Both Eyes of Chickens: a pilot study

Purpose : Form-deprivation and lens-induced myopia are two well-established models for experimental myopia research. Although both paradigms induce axial myopia, form-deprivation myopia is induced by the absence of clear vision and the axial elongation can progress continuously with large inter-subject variability (open-loop); whereas lens-induced myopia by imposing hyperopic defocus stops when eyes receive a clear focal image (closed-loop). This pilot study investigated whether the refractive development in both eyes was independent of each other under the bilateral form-deprivation condition.

Methods : At day 5 post-hatching (P5), White Leghorn chicks were randomly assigned to receive either unilateral (UFD, n=5) or bilateral form deprivation (BFD, n=5) by covering one (right eye) or both eyes with translucent diffusers. At the onset and over the 9-day treatment period, refractive state and ocular axial dimensions were measured longitudinally (P5, P7, P10, P12, and P14) using a modified Hartinger refractometer and a high-resolution A-scan ultrasonographer, respectively. Two-way repeated measures ANOVA was used for statistical analysis. All parameters were expressed as mean±SD.

Results : Both treatment and duration showed significant main effects on spherical-equivalent refractive error (SE) development (Treatment effect: F(3,16)= 4.19, p
Conclusions : Refractive development in both eyes was synchronized under bilateral form deprivation in chickens. Further studies are warranted to understand the mechanism of inter-ocular synchronization and its potential role in form deprivation myopia.