Fluorescein angiography is a common procedure used in ophthalmology to diagnose and monitor diseases of the retinal and choroidal blood vessels. The most commonly seen adverse reactions to fluorescein angiography include nausea, vomiting, and urticaria. More severe reactions such as anaphylaxis are rare, occurring in only 1 of 2247 patients (0.4%) in a recent retrospective study. The standard dose of intravenous fluorescein used for fluorescein angiography is 500mg given intravenously in a 10% or 25% solution. One study from 2008 attempted to compare a 200mg dose versus a 500mg dose of intravenous fluorescein, and found that 200mg produced inferior image quality. However, the quality of the cameras used for fluorescein angiography has improved significantly in the last 10 years, and the scanning laser ophthalmoscope currently used for fluorescein angiography in our clinic (Optos) is significantly more effective than the fundus camera used in the 2008 study (Topcon). The scanning laser ophthalmoscope uses a fundamentally different imaging technique than the traditional fundus camera, with a much narrower illumination source, and has been shown to be significantly more sensitive in the detection of retinal vascular leakage.
A commonly used method for preventing adverse reactions in patients who have previously had an adverse reaction to intravenous fluorescein is to use a 250mg dose instead of the standard 500mg dose, despite the lack of evidence to this effect. In our anecdotal experience, a 250mg dose of intravenous fluorescein, used in patients whom have previously experienced an adverse reaction, has produced images of equivalent quality to the images produced using a full 500mg dose. To our knowledge, no study has compared a 500mg dose of intravenous fluorescein with a lower dose since the 2008 study previously mentioned, despite the advances in camera quality.
The study will aim to recruit a sample size of approximately 100 patients. Adult patients scheduled for fluorescein angiography at the Kresge Eye Institute will be recruited into the study by one of the study members if they meet inclusion and exclusion criteria. Once a patient has consented to participate in the study, they will be randomized to receive either a 250mg or 500mg dose of intravenous fluorescein with their fluorescein angiography procedure. All fluorescein angiograms will be done only if clinically indicated, and therefore the patient will not be placed at any increased risk by participating in this study. If a participant returns for a repeat fluorescein angiogram within the next four months, they will receive the dose (250mg or 500mg) which they did not receive with their previous angiogram. Patients who experience an adverse reaction during their first angiogram will be removed from the study in order to prevent a patient who had an adverse reaction with a half-dose from receiving a full-dose with a subsequent procedure. The photographer will adjust the image brightness settings in order to create the "best possible" image for each patient, and there will be no change between procedures with the 250mg and 500mg doses. A single camera (Optos) will be used for each patient in the study.
Data collection will be obtained from the patient, the imaging procedure, and the patient's electronic medical records at the Kresge Eye Institute. Information to be collected includes age, gender, race, visual acuity, and ophthalmologic medical history. The timing and quality of images at different phases of fluorescein angiography will be compared between 500mg and 250mg doses in each eye using objective and subjective measures. Subjective criteria will include grading of the images by a panel of masked retinal surgeons and residents. Grading will look at specific factors of a fluorescein angiography such as macula detail, macrovasculature, and microvasculature. These subjective criteria will then be used to determine whether any appreciable difference exists in the image quality between 250mg and 500mg doses of intravenous fluorescein given prior to Optos fluorescein angiography.
