Amblyopia is a developmental disorder of vision. Recent evidence has suggested that refractive correction alone treats the condition successfully in a third of cases, with further occlusion therapy required in the remainder. Anisometropia is a contributing factor in many amblyopia cases, and is a condition which is defined as a significant difference in refractive error between the eyes. Theoretically, anisometropia leads to both defocus in one eye as well as unequal image size (aniseikonia). Current spectacle prescribing corrects for the first but not for the second of these deficits. Aniseikonia may be acting as a barrier to neural plasticity, restricting visual recovery. This project aims to accurately measure the extent of aniseikonia in anisometropic amblyopes using subjective and objective measurements. Following on from this, a clinical pilot study will be completed to assess if correcting for aniseikonia results in better treatment outcomes in children.