‘Investigations and their interpretation’ introduces the reader to both standard and emerging technologies that enable assessment of the structure or function of the eye and visual system. Starting with visual field testing, the chapter covers automated and Goldmann perimetry, novel protocols and progression analysis. Anterior segment imaging covers keratometry, topography and OCT. Posterior segment imaging includes angiographic techniques, novel blood flow quantification methods, OCT, and adaptive optics. Electrodiagnostic tests are introduced including multifocal techniques. Finally ophthalmic ultrasonography and radiology are supported by clinical strategies and examples to support the practice and interpretation of these techniques.