The pictures show blocked and leaking retinal blood vessels. This study is fundus angiography. A dye is injected into an arm vein, and the bloodstream carries it to the vessels of the eye within seconds. The fundus camera carries special filters that make the dye stand out as it flows. The three common findings are vascular obstructions, leakage, and neovascularization, which means the abnormal growth of new blood vessels. All three matter a great deal in diabetes.
Timing is the point of the test. The camera fires in a rapid sequence. The images record the vessels at set time intervals as the dye fills the whole vascular tree. A vessel that is blocked stays dark. A vessel that leaks lets dye spread into the tissue around it. Two dyes are used. Fluorescein is the dye for most routine angiograms. Indocyanine green is more specialized and is chosen to study the choroidal circulation, the vessel layer under the retina. It is also chosen when blood or fluid deposits on top of the choroid hide those vessels from fluorescein. Angiography sometimes images the iris as well. The angiogram pictures come out black and white.
Remember what the dye can and cannot tell you. It maps blood flow, so it answers questions about blockage, leakage, and new vessels. It is not a test of lens clarity, corneal shape, or eye pressure. A diabetic patient is sent for this study to find leaking vessels and new vessels early, while treatment still helps. Explaining what an angiogram looks for sits in the COA ophthalmic imaging content area.
Incorrect Answers
- A. Lens cloudiness is judged at the slit lamp, not by a dye in a vein. The dye travels in blood vessels, and the natural lens has no blood vessels.
- B. Corneal thickness comes from a separate measuring instrument and has nothing to do with dye in the bloodstream or with pictures of the retina.
- D. The width of the drainage angle is studied at the front of the eye. Angiography is aimed at the fundus, which is the back of the eye.
Testing Pearls
- Angiography detects obstructions, leakage, and neovascularization.
- It is done with the fundus camera plus special filters.
- Images are taken in rapid sequence to show timed filling of the vessels.
- Fluorescein is used for most routine angiograms.
- Indocyanine green is picked for the choroid and when a hemorrhage hides it.
References
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 10, Adjunctive Tests and Procedures.
