Retinoblastomas appear in children under two years of age, hence the importance of ophthalmologic examinations at an early age. In these cases the initial sign may be leukocoria (white reflex in the pupil).
In adults it depends on the location of the tumor. If it affects the macula (center of the retina), it may be accompanied by loss of vision. If the location is peripheral, it may go unnoticed, so it is important to follow routine controls by an ophthalmologist.