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Congenital hypertrophy of the retinal pigment epithelium (CHRPE) on ocular coherence tomography (OCT) has the characteristic sign of RPE thickening and hyper reflectivity. However, the underlying choroid characteristics remain under researched. This retrospective study utilised data from an ophthalmic oncology clinic in New York to analyse 46 patients and 46 eyes for retinal and choroidal thickness by obtaining enhanced depth imaging OCT (EDI-OCT) images. After excluding two patients with a lesion <2mm, 44 patients with a mean age of 54 years were included. Furthermore, only 32 patients had EDI-OCT imaging adequate for analysis. Thickness measurements were analysed by two independent observers from the centre of the CHRPE and 500um outside the lesion on EDI-OCT imaging and a mean of the two measurements were calculated. Sattler’s layer and the choriocapillaris (outermost choroid layers) were atrophic in 31 patients. Haller’s layer (innermost choroid layer) was healthy in 14, thin in 17, and absent in one. There was no statistical difference in choroidal thickness for Haller’s layer in CHRPE. However, CHRPE with a thinned or absent Haller’s layer displayed a significantly (p<0.05) greater diameter compared to the healthy eye (8.78 vs. 6.53mm). The authors’ results for choroidal and retinal thickness in CHRPE eyes in relation to the healthy eye were found to be approximately half. Lesion location was found to play no role with choroidal thickness upon statistical analysis. The authors state the majority (97%) of the cohort demonstrated an attenuated or unidentifiable inner choroid. In comparison a healthy outer choroid layer was identified in 44%. These findings suggest preference for inner choroid impact in CHRPE. With increasing technological advances, OCT descriptions of the choroid have improved. However, an important limitation of OCT analysis is the disturbance of optical transmission to the choroid as a result of the heavy pigment present within the CHRPE. The authors conclude with the speculation as to whether CHRPE pathology is derived from the choroid, retina, or the RPE and believe confirmation is warranted by other cohorts.

Optic coherence tomography characteristics of the choroid underlying congenital hypertrophy of the retinal pigment epithelium.
Francis JH, Sobol EK, Greenberg M, et al.
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Annes Ahmeidat

MBChB, BSc, Ninewells Hospital and Medical School, Dundee, UK.

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