BACKGROUND Children with perinatal brain damage have a high prevalence of visual impairment. Stimulation of vision at a critical period can encourage brain plasticity and the recovery of impaired function. OBJECTIVE The aim of our study was to investigate when is the critical period for visual stimulation in children with perinatal brain damage. METHODS We compared 35 children within the first eight months of life (median age = 4 months) to 35 children aged between eight and thirty months (median age = 15 months), all with perinatal brain damage. All the children were attending an early intervention program at Mali dom, Zagreb, a rehabilitation centre for children with visual impairment. We compared the results from baseline and follow-up assessments of visual functions (grating acuity and contrast sensitivity). We also compared differences in change scores between the two groups. RESULTS Our results have shown that children who commence a visual stimulation program within the first eight months of life had more improvement in both visual functions. This improvement is statistically significant in visual acuity (p = 0.048). CONCLUSIONS These results indicate the importance of starting a visual stimulation program within the first eight months after birth.