Apparatus, systems and methods for use in analyzing discrete reactions at ultra high multiplex with reduced optical noise, and increased system flexibility. Apparatus include substrates having integrated optical components that increase multiplex capability by one or more of increasing density of reaction regions, improving transmission of light to or collection of light from discrete reactions regions. Integrated optical components include reflective optical elements which re-direct illumination light and light emitted from the discrete regions to more efficiently collect emitted light. Particularly preferred applications include single molecule reaction analysis, such as polymerase mediated template dependent nucleic acid synthesis and sequence determination.