Abstract
PurposeTo determine the characteristics of the photoreceptor abnormalities in retinitis pigmentosa (RP) and cone–rod dystrophy (CRD).MethodsWe evaluated the photoreceptor abnormalities using spectral-domain optical coherence tomography (SD-OCT) in 28 patients with RP and 17 patients with CRD. The OCT images and full-field electroretinograms were obtained from 21 eyes in normal subjects who were age-matched to patients with RP and CRD and served as controls.ResultsEyes with RP and CRD had markedly decreased rod responses (6.5 and 57.5 % of normal value), maximal responses (9.6 and 51.6 %), cone (16.5 and 25.8 %), and 30-Hz flicker responses (17.8 and 30.1 % of normal value), and their P values were smaller than 0.0003. On comparison of ERG data between RP and CRD, they had statistically significant differences in rod responses (P < 0.0003) and maximal responses (P < 0.0003). However, there were no statistical differences in cone response and a weak difference in 30-Hz flicker responses (P < 0.017). The best-corrected visual acuity was −0.03 ± 0.09 (logMAR, mean ± standard deviation [SD]) in eyes with RP, but 0.57 ± 0.54 in eyes with CRD. SD-OCT showed that eyes with RP had an intact reflective line at the junction between the photoreceptor inner and outer segment (IS/OS) at the fovea, while eyes with CRD had no IS/OS. The extent of the central visual field was correlated with the IS/OS length at the macula in eyes with RP.ConclusionThe distribution patterns of the IS/OS line help to differentiate between RP and CRD.
Highlights
Retinitis pigmentosa (RP) is an inherited rod–cone dystrophy characterized by night blindness, photophobia, and loss of the peripheral visual field
We evaluated the photoreceptor abnormalities using spectral-domain optical coherence tomography (SD-Optical coherence tomography (OCT)) in 28 patients with retinitis pigmentosa (RP) and 17 patients with cone–rod dystrophy (CRD)
The OCT images and full-field electroretinograms were obtained from 21 eyes in normal subjects who were age-matched to patients with RP and CRD and served as controls
Summary
Retinitis pigmentosa (RP) is an inherited rod–cone dystrophy characterized by night blindness, photophobia, and loss of the peripheral visual field. Differentiating between pure cone dystrophy and CRD is difficult, because some degree of rod dysfunction develops as the cone dystrophy progresses. The definitions that have been used conventionally are ‘‘cone dystrophy for retinal diseases with predominant cone dysfunction with later onset and mild rod involvement,’’ and ‘‘CRD for retinal dystrophies with early onset cone dysfunction followed shortly thereafter by significant rod disease’’ [1]. In both rod–cone (RP) and CRDs, the symptoms occasionally overlap, making the differential diagnosis difficult
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