The Role of Optical Coherence Tomography in the Evaluation of Ocular Photodynamic Therapy

Clinical studies in vitreoretinal disorders utilize a variety of modalities in order to assess the retina’s response to different therapies. The standard methods include visual acuity assessment, clinical examination, angiography, and electrophysiologic testing. Visual acuity is a primary outcome in most ophthalmology studies. It is measured by standardized techniques such as the Early Treatment for Diabetic Retinopathy Study (ETDRS) chart or the modified Bailey-Lovie chart. Clinical examination may involve a certified study examiner or multiple examiners and it may be performed in a masked fashion. Angiography with fluorescein dye is used to assess the posterior segment circulation. It has traditionally been the gold standard test to diagnose and classify choroidal neovascularization (CNV), as well as to evaluate the response of CNV to therapy. Indocyanine green (ICG) dye, which was originally used in cardiovascular imaging, has recently found applications in ophthalmology. The molecular and fluorescent properties of ICG permit improved imaging of the choroidal circulation. In some cases, ICG may permit evaluation of pathology, which is not visualized with fluorescein angiography due to blockage by hemorrhage. Electrophysiologic tests such as the electroretinogram (ERG) and electro-oculogram (EOG) are useful to localize pathology to a specific level or location in the retina and to monitor the effect of therapy.