Purpose To study the clinical features and to identify the genetic defects in seven Chinese families with achromatopsia.

METHODS Detailed ocular examinations including best corrected visual acuity (BCVA), color vision, slit lamp, fundus, electroretinography (ERG) and optical coherent topography (OCT) were performed for affected subjects. Peripheral blood was obtained from all patients and their family members for genomic DNA extraction. All exons of CNGA3 (cyclic nucleotide-gated channel alpha-3) were ampli?ed by polymerase chain reaction (PCR) and screened for mutation by direct DNA sequencing. A hundred normal controls were screened to verify suspected diseased related mutations.

RESULTS Nystagmus, photophobia and impaired color discrimination were occurred in all patients. The best corrected visual acuity of the affected subjects ranged from 0.05 to 0.3. Severely depressed and non-recordable cone ERG was observed.  Noticeable structural changes were observed in the central retina of patients with achromatopsia under OCT examination. CNGA3 mutations were identified in four out of seven families. Novel compound heterozygous mutations I353T (c.1058T>C) and E377del  (c.1129-1131delGAG) were identified in family ZF01; a novel frame shift mutation T14PfsX4 (c.40delA) and hotspot missense mutation R283W (c.847C>T) were identified in family LP06; novel homozygous missense mutation D211E (c.633A>T) were detected in family ZR01 and a novel nonsense mutation S31X (c.62C>G) and a hotspot mutation R410W (c.1228C>T) were identified in family WS05. Mutations were segregated within the families. These mutations were not detected among 100 controls.

CONCLUSIONS. CNGA3 related achromatopsia is more common than CNGB3 related achromatopsia in Chinese population. Five novel mutations were identified in CNGA3. Genetic characterization of patients with achromatopsia is important for genetic counseling and future gene therapies. To the best of our knowledge this is the first report of genetic study related to Chinese achromatopsia patients.