Phenotypic characterisation of enhanced S Cone syndrome-a multicenter case series analysis

To characterise in detail the clinical features of enhanced S-cone syndrome (ESCS).

A retrospective study of retinal phenotype in 34 subjects with ESCS recruited from four centres in India. All subjects had a pathognomonic electroretinogram (ERG) features diagnostic of ESCS and had colour fundus imaging. Fundus photographs, fundus autofluorescence (11 subjects) and optical coherence tomography (OCT, 22 subjects) images were graded, and correlation between their gradings were ascertained. Effect of age on visual acuity was analysed.

Twenty-one males (62%) and 13 females were included. The median age at presentation was 17.5 years [Interquartile range:10, 25]. Nyctalopia was the most common presenting symptom seen in 76% (26/34) of subjects. The median best corrected visual acuity at presentation was 0.35 logMAR [0.17, 0.62]. The most common retinal phenotype was a ring of non-specific pigmentary changes along the arcades with or without atrophy (41%, 28/68 eyes) followed by yellow to white dot like changes along the vascular arcades/mid-periphery (38%, 26/68). Hypo-autofluorescence with moderate diffuse or patchy changes along the major vascular arcades was seen in 37% (8/22) of eyes. OCT showed foveomacular schisis in 79% (35/44), of which 8 eyes (18%) had giant schisis(>1000 um). No correlation was observed between any of the retinal features and fundus autofluorescence sub-types, but lower visual acuity with increasing age was noted (R²;0.122, p < 0.05).

This study establishes the range of retinal features associated with ESCS. Pigmentary changes with or without atrophy along the arcades was predominantly seen in our cohort unlike nummular changes described in previous studies of ESCS.