ERG variability in X-linked congenital retinoschisis patients with mutations in the RS1 gene and the diagnostic importance of fundus autofluorescence and OCT.
OBJECTIVE
X-linked congenital retinoschisis (RS) is a relatively frequent retinal dystrophy associated with RS1 gene mutations. A negative electroretinogram (ERG), i.e., a b/a wave ratio <1.0 in the standard combined response, is considered a key diagnostic feature of RS. Only a few cases without a negative ERG have been reported.


METHODS
This study includes 24 RS patients with RS1 mutations. ERGs (according to ISCEV standards, n = 23), ON-OFF-responses (n = 9), fundus autofluorescence (FAF, n = 8), and optical coherence tomography (OCT, n = 6) were performed.


RESULTS
The mean age at examination was 22.6 years (0.5-53.2 years), and median visual acuity was 0.3 (no light perception to 0.6). A negative ERG was found in 13 of 23 patients (56.5%), of whom one patient presented a negative ERG at the 2-year follow-up, with an initial b/a wave ratio >1.0. Another patient had a b/a wave ratio of 0.96 in one eye and 1.02 in the fellow eye. In 10 of 23 patients, the b/a wave ratio ranged from 1.03 to 1.34. Single-flash cone and 30 Hz flicker responses were always reduced. FAF and OCT were pathologic in all patients tested. FAF was increased in the fovea. OCT revealed foveal schisis to various degrees and thinning of the retina in an older patient.


CONCLUSIONS
Although ERG abnormalities were detected in all patients tested, more than 40% of patients with RS1 mutations did not have a negative ERG. In clinically suspected RS a combination of ERG, FAF, OCT, and molecular-genetic testing is advised to verify the diagnosis.
Renner
Agnes B
AB
Augenklinik, Charité Campus Benjamin Franklin, Universitätsmedizin Berlin, Hindenburgdamm 30, 12200 Berlin, Germany. a.renner@berlin.de
Kellner
Ulrich
U
Fiebig
Britta
B
Cropp
Elke
E
Foerster
Michael H
MH
Weber
Bernhard H F
BH
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004596:Electroretinography; D005136:Eye Proteins / Q000235:genetics*; D005453:Fluorescence; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009154:Mutation; D012160:Retina / Q000503:physiopathology; D041441:Retinoschisis / Q000175:diagnosis* / Q000235:genetics* / Q000503:physiopathology; D041623:Tomography, Optical Coherence; D014792:Visual Acuity
D005136:Eye Proteins; C108726:RS1 protein, human