Diagnosing eye conditions using medical photography has, for many years, been reliant upon fundus fluorescein angiography. This technique combines injected sodium fluorescein dye, filter combinations, flash photography and, until recently, ‘pushed’ (extended) development. The images produced are of diagnostic value for the clinicians to study the circulation in the retina to reveal conditions such micro-aneurysms and arterial stenosis, haemorrhages and other ophthalmic conditions. And the procedure is an excellent diagnostic tool for patients with diabetic retinopathy.
The origins of the diagnostic technique started in 1959 when two medical students, Harold Novotny and David Alvis, studying at Indiana University, were researching a photographic technique to estimate the oxygen concentrations in retinal vessels. The application of dyes, retinal photography and the use of filters was not new at the time, but bringing these known techniques together to form a new procedure would result in a universally accepted diagnostic technique.
The students' previous research led them to place a filter with a peak excitation of 450nm (Wratten filter 47 in the blue range) in the pathway of the illuminating source (flash and observation lamp) of a Zeiss fundus camera. A filter of peak emission of 520nm (Wratten filter 58 in the green range), combined with a 3mm layer of copper sulphate, was placed over the camera’s light pathway.
The technique required a patient - in this case Alvis, who was the first to undergo the investigation having lost the toss of a coin. 5ml of *fluorescite was injected into Alvis’s cubital vein (arm) followed by a saline flush. As the dye circulated, photographs were taken of the retina. The technology at the time allowed the flash to recycle every 12 seconds and so limited the number of images that could be taken during circulation. The results, because of the low light levels and slow speed of the photographic emulsion, were very faint, so in subsequent tests pushed processed film with an extended development time was used. This revealed a series of denser images of the circulation of the dye around the fundal vessels.
Normal fluorescein angiogram
of the right eye
Angiogram of the retina showing
the circulating sodium fluorescein
dye (white) at mid phase
Reproduced by kind permission
of the University of Iowa Carver
College of Medicine
Abnormal fluorescein angiogram
of the right eye
Dysfunction of retinal circulation on
the top half of the photograph with
associated vessel blockage (black)
Reproduced by kind permission of
Barts Health NHS Trust, London
Although funding for more research was refused by the students’ university, subsequent development was carried out by several different investigators. Today, Novotny and Alvis have been recognised as the founders of this invaluable technique which has found worldwide acceptance as the main diagnostic imaging procedure in medical retinal clinics.
*Fluorescite” is a trade name but comprised of 5% fluorescein in sodium carbonate.
A copy of Novotny and Alvis’s original article can be found at:-
**http://circ.ahajournals.org/content/24/1/82.full.pdf
Copyright: Bob Tapper (2015)