AIMS: To evaluate the evolution of ocular and electroretinographic findings in identical twin sisters with the carbohydrate deficient glycoprotein (CDG) syndrome over a period of 14 years. METHODS: Both girls underwent a clinical ophthalmic examination with funduscopy and an electrophysiological assessment with recording of flash electroretinogram (FERG) at the age of 4 years and 18 years RESULTS: On ophthalmic examination at the age of 4 years an alternating convergent squint and a saccadic pursuit was diagnosed. In both, vision was 6/9 bilaterally. Fundus examination showed normal optic discs, narrow blood vessels, and a mild irregular pigmentation in the periphery. In one girl the FERG showed a recognisable a, b1, and b2-wave with reduced amplitude to less than 40% of the normal. In the other girl the reduction in amplitude was still more obvious, but for the white flash a small b1-wave was still present. At the age of 18 vision had remained 6/9 in both eyes. Funduscopy showed pink optic discs, moderately narrowed blood vessels, and bony spicule pigmentary deposits in the mid periphery. The adapto ERG, performed in identical conditions at 18 years of age, showed a completely extinguished trace for both eyes. CONCLUSIONS: Despite progressive deterioration of ERG findings good central vision was preserved over 14 years.