As expected, visual field testing in cone dystrophy usually reveals a central scotoma. In cases with the typical bulls-eye appearance, there is often relative central sparing.Because of the wide spectrum of fundus changes and the difficulty in making the diagnosis in the early stages, electroretinography (ERG) remains the best test for making the diagnosis. Abnormal cone function on the ERG is indicated by a reduced single-flash and flicker response when the test is carried out in a well-lit room (photopic ERG). The relative sparing of rod function in cone dystrophy is evidenced by a normal scotopic ERG, i.e. when the test is carried out in the dark. In more severe or longer standing cases, the dystrophy involves a greater proportion of rods with resultant subnormal scotopic records. Since cone dystrophy is hereditary and can be asymptomatic early on in the disease process, ERG is an invaluable tool in the early diagnosis of patients with positive family histories. Cone dystrophy in general usually occurs sporadically. Hereditary forms are usually autosomal dominant, and instances of autosomal recessive and X-linked inheritance also occur. In the differential diagnosis, other macular dystrophies as well as the hereditary optic atrophies must be considered. Fluorescent angiography, ERG, and color vision tests are important tools to help facilitate diagnosis in early stages. Treatment
Though there is no treatment for cone dystrophy, certain supplements may help in delaying the progression of the disease.
Ametropic amblyopia is a medical condition in which the retina cannot focus on the image of a distant object, a condition often described as reduced visual acuity. This is due to large uncorrected refractive errors in the patients optic system of the eyes. Astigmatism is one of the most frequent causes of ametropic amblyopia. References
Further reading
Moseley, Merrick J., et al. "Effectiveness of occlusion therapy in ametropic amblyopia: a pilot study." British Journal of Ophthalmology 81.11 (1997): 956–961. Cavazos, H.;  et al. (1993). "Ametropic Amblyopia". Strabismus. Informa Plc. 1 (2): 63–67. doi:10.3109/09273979309087719. PMID 21314500. Abraham, S. V. "Bilateral ametropic amblyopia." J Pediatr Ophthalmol Strabismus 1 (1964): 57–61. Werner, D. B., and W. E. Scott. "Amblyopia case reports--bilateral hypermetropic ametropic amblyopia." Journal of pediatric ophthalmology and strabismus 22.5 (1984): 203–205. Moseley, Merrick J;  et al. (1997). "Effectiveness of occlusion therapy in ametropic amblyopia: a pilot study". British Journal of Ophthalmology. BMJ Publishing Group Ltd. 81 (11): 956–961. doi:10.1136/bjo.81.11.956. PMC 1722055. PMID 9505818.