Trypan blue (trade name MembraneBlue, VisionBlue) is a vital stain used to selectively color dead tissues or cells blue. Live cells or tissues with intact cell membranes are not colored. Since cells are very selective in the compounds that pass through the membrane, in a viable cell trypan blue is not absorbed; however, it traverses the membrane in a dead cell. Hence, dead cells are shown as a distinctive blue color under a microscope. Since live cells are excluded from staining, this staining method is also described as a dye exclusion method. This dye may be a cause of certain birth defects such as encephalocele. Trypan blue is commonly used in microscopy (for cell counting) and in laboratory mice for assessment of tissue viability. The method cannot distinguish between necrotic and apoptotic cells. Trypan blue is also used in ophthalmic cataract surgery to stain the anterior capsule in the presence of a mature cataract, to aid in visualization, before creating the continuous curvilinear capsulorhexis.

Fluorescein is a synthetic organic compound available as a dark orange/red powder slightly soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications. Fluorescein was first synthesized by Adolf von Baeyer in 1871. It can be prepared from phthalic anhydride and resorcinol in the presence of zinc chloride via the Friedel-Crafts reaction. Fuorescein sodium is used intravenously in diagnostic fluorescein angiography or angioscopy of the retina and iris vasculature. Fluorescein sodium responds to electromagnetic radiation and light between the wavelengths of 465-490 nm and fluoresces, i.e., emits light at wavelengths of 520-530 nm. Thus, the hydrocarbon is excited by blue light and emits light that appears yellowish-green. Following intravenous injection of fluorescein sodium in an aqueous solution, the unbound fraction of the fluorescein can be excited with a blue light flash from a fundus camera as it circulates through the ocular vasculature, and the yellowish green fluorescence of the dye is captured by the camera. In the fundus, the fluorescence of the dye demarcates the retinal and/or choroidal vasculature under observation, distinguishing it from adjacent areas/structures. Topical, oral, and intravenous use of fluorescein can cause adverse reactions, including nausea, vomiting, hives, acute hypotension, anaphylaxis and related anaphylactoid reaction, causing cardiac arrest and sudden death due to anaphylactic shock. The most common adverse reaction is nausea, due to a difference in the pH from the body and the pH of the sodium fluorescein dye; a number of other factors however, are considered contributors as well. The nausea usually is transient and subsides quickly. Intravenous use has the most reported adverse reactions, including sudden death, but this may reflect greater use rather than greater risk. Both oral and topical uses have been reported to cause anaphylaxis, including one case of anaphylaxis with cardiac arrest (resuscitated) following topical use in an eye drop. Reported rates of adverse reactions vary from 1% to 6%. The higher rates may reflect study populations that include a higher percentage of persons with prior adverse reactions. The risk of an adverse reaction is 25 times higher if the person has had a prior adverse reaction. The risk can be reduced with prior (prophylactic) use of antihistamines and prompt emergency management of any ensuing anaphylaxis. A simple prick test may help to identify persons at greatest risk of adverse reaction

Trypan blue (trade name MembraneBlue, VisionBlue) is a vital stain used to selectively color dead tissues or cells blue. Live cells or tissues with intact cell membranes are not colored. Since cells are very selective in the compounds that pass through the membrane, in a viable cell trypan blue is not absorbed; however, it traverses the membrane in a dead cell. Hence, dead cells are shown as a distinctive blue color under a microscope. Since live cells are excluded from staining, this staining method is also described as a dye exclusion method. This dye may be a cause of certain birth defects such as encephalocele. Trypan blue is commonly used in microscopy (for cell counting) and in laboratory mice for assessment of tissue viability. The method cannot distinguish between necrotic and apoptotic cells. Trypan blue is also used in ophthalmic cataract surgery to stain the anterior capsule in the presence of a mature cataract, to aid in visualization, before creating the continuous curvilinear capsulorhexis.

ICG is a cyanine fluorescent dye which is used in medicine as an indicator substance (for photometric hepatic function diagnostics and fluorescence angiography) in cardiac, circulatory, hepatic and ophthalmic conditions. It is administered intravenously and, depending on liver performance, is eliminated from the body with a half life of approx. 3-4 minutes.