Abstract
Purpose: :
To study macular structure of male patients and female carriers of choroideremia.
Methods: :
Individuals affected with or carriers for choroideremia and normal-sighted controls were imaged at several retinal locations within 1.5mm of fixation using an adaptive optics scanning laser ophthalmoscope (AOSLO) developed by Canon Inc. (Tokyo, Japan). Infrared (IR) fundus photography, spectral domain optical coherence tomography (OCT), and autofluorescence (AF) images were also obtained. Patients underwent ophthalmic examination and were molecularly diagnosed.
Results: :
Many choroideremia patients show a central region of relatively intact retinal structure. Dark islands observed in IR photographs correspond to regions where the retinal pigment epithelium (RPE) remains intact. OCT confirms these islands have RPE and photoreceptor layers. In addition, these dark islands exhibit AF. AO imaging reveals residual cone photoreceptors throughout these central regions in patients affected with choroideremia, however cone density in these areas is reduced compared to normal. Areas devoid of cone photoreceptors allow for the visualization of deep choroidal vasculature. IR imaging in carriers generally shows intact central retina with hypopigmented spots and scattered peripheral regions of atrophy. AF is absent in the hypopigmented peripheral regions consistent with retinal and RPE atrophy at those locations. Carriers of choroideremia show an intact cone photoreceptor mosaic with AO imaging and OCT.
Conclusions: :
AOSLO imaging allows visualization of the cone photoreceptor mosaic within the remaining islands of intact retinal structure in patients with choroideremia. Choroideremia patients can maintain relatively high visual acuity late in life despite reduced cone density at locations retaining retinal structure. Future applications of high-resolution AO imaging in combination with other imaging modalities will include longitudinal studies of the progression of diseases such as choroideremia. In addition, AO imaging may also be an effective endpoint for determining the efficacy of experimental treatments, such as gene or cell-based therapies.
Keywords: imaging/image analysis: clinical • photoreceptors • retina