Usefulness of handheld electroretinogram system for diagnosing blue-cone monochromatism in children.

Purpose: To report the diagnosis of three childhood patients with blue-cone monochromatism (BCM) using S-cone electroretinograms (ERG) recorded with RETeval Complete.

Study Design: Prospective clinical study.

Methods: We examined three boys initially suspected of having rod monochromatism. S-cone ERG was performed with red background and blue flashed light stimulation using two different intensities: 0.25 cd × s/m and 1 cd × s/m.

Results: Case 1 was a 12-year-old boy with a visual acuity of 0.1 OU. Case 2 was an 8-year-old boy with a visual acuity of 0.3 OD and 0.2 OS. Both cases showed a myopic fundus and nystagmus without any other ocular abnormalities. Case 3 was a 6-year-old boy with a visual acuity of 0.3 OD and 0.4 OS. He also showed myopic fundus changes, but nystagmus was not observed. Rod and maximal responses recorded with RETeval were likely to be within normal range; however, cone responses were absent in all cases. S-cone ERGs showed positive responses at 40 ms with 0.25 cd × s/m intensity in Case 2, and at approximately 30-40 ms with 1.0 cd × s/m intensity in all three cases. These ERG findings led to a diagnosis of BCM.

Conclusions: S-cone ERG of RETeval was helpful in diagnosing with minimal invasion BCM in childhood patients.