In a series focusing on medical specialties, the BBC News website meets medical photographer Karl Southerton.
Medical photographers provide a wide range of photographic services to staff working in the medical field.
Their work can play a key role in helping to diagnose disease, and track and record treatments.
WHAT IS YOUR JOB?
I am a head of department in medical photography at the Western Eye Hospital, London.
Now I only take photographs of the eye, but when I was a general medical photographer I might take pictures of any condition the doctors needed records of, such as a skin problem or a mastectomy.
We document things in situ. You can photograph again and again in the same position and have a photographic record of what the patient looks like before, during and after treatment.
WHAT IS THE MOST COMMON CONDITION?
At the moment age-related macular degeneration (AMD) is the big thing as there are now treatments which can help patients while 10 years ago when doctors would say there was not a lot they could do.
Often they would have to say 'We will probably monitor you, but you will probably go blind'.
Now we can actually treat the patient so they can get their sight back.
WHAT IS THE MOST COMMON PROCEDURE?
Taking photographs of AMD patients.
The macular is the key part of the retina at the back of the eye where the rod and cone cells that react to light are concentrated.
If it is damaged then it can have a huge impact on the quality of your vision - particularly your central vision.
AMD is a degeneration of this area, which can be caused by leakage from the tiny blood vessels nearby.
Doctors treat the area with drugs, and then we use photography both to see if it has stopped leakage from the blood vessels, and to measure the extent of the scarring that has taken place.
We put fluorescent dye into the patient to fill the retinal vessels to show if there is any sort of leakage or block and where they are.
We also look at the vessels underneath the retina.
We dilate the pupils of a patient - this is essential as it's very difficult to image a patient without dilation drops as the pupil's natural reaction to light is to close.
Dilating drops work on one of two principles: they either stimulate the iris muscle that opens the pupil (the dilator), or prevent action of the iris muscle that closes the pupil (the sphincter).
When a person is dilated the pupils remain large even if light is shone in them. This then allows a clear view of the retina.
We then use a camera, called a fundus camera, with inbuilt mirrors to take pictures of the eye.
There is a filament light within it that bounces off the back of the retina and takes a reversed image. The image is then bounced back through a series of mirrors which then turn the image the right way round so we can record it.
WHAT IS THE HARDEST THING ABOUT YOUR JOB?
The hardest thing about my job is the number of patients I see - about 200 plus a month with a variety of different ophthalmic conditions. AMD probably accounts for about 50-60% of these.
Then there is also separate database, with about 7,000 patients, for diabetic patients as these are seen regularly for an eye test.
Retinal images are taken of the eyes of the diabetic patients using a 'non-mydriatic fundus' camera, which instead of emitting light to view the retina, instead is viewed through an infa red viewer which is better for the patient as there's no bright light (other that when the image is taken). As diabetic patients are quite often photophobic and also don't dilate very well, this camera is specifically used for their needs.
Most diabetic patients have a yearly screening appointment.
WHAT IS YOUR MOST SATISFYING CASE?
It is very satisfying when you have someone who is expecting to lose their sight, but they come back a couple of weeks later and you can see it is getting better and better.
The eye of a person with Age Related Macular Degeneration
It is also great to have the photographic proof to be able to show treatment is working.
Photographs can really help a patient, because they can show them how they were before and after an operation.
It can really bring home to them the difference treatment has made - for instance, a patient who undergoes surgery for a drooping eyelid.
WHY DID YOU CHOOSE THIS SPECIALITY?
I went to college and did an HND in commercial photography, fashion and advertising and then went to do a course in art and design, with more emphasis on audio/visual.
I did a few jobs including work with the local newspaper and a few photographers.
But there were no jobs out there because of the recession, so I looked to see what jobs were available and kept seeing medical photography and wondered what it was all about.
I made several shortlists for jobs but didn't get them because I didn't have the experience.
But then I offered to do two weeks work experience at Moorfields Eye Hospital, someone was leaving and I got the job.
IF YOU HAD YOUR TIME AGAIN WOULD YOU CHANGE YOUR SPECIALTY?
I probably would not. I like ophthalmic work. It is very specialised and when you focus on the back of the eye it is very critical work and I like that.
WHICH SPECIALTY WOULD YOU HAVE GONE INTO IF NOT YOUR OWN?
I had an idea that I wanted to do sports photography because I liked following Newcastle United.
Sports photography is quite similar to our work because you are looking at something quite close up on the pitch and you have obviously got to take the photograph as quickly as possible.
It is very difficult to get an action shot, which is similar to getting a retinal shot because you have a patient at whom you are shining a bright light and they don't want to keep their eyes open for too long.
HOW DO YOU SEE THE ROLE DEVELOPING IN THE FUTURE?
Now there is foundation degree course to take medical photographs which gives students a background in what they are actually taking photos of.
This is important, because there is no use saying 'take a picture of the optic disc,' if you don't know what the optic disc is.
The imagery is also becoming far more detailed, and is playing an ever more key role in helping medical staff make a diagnosis, or assess how a treatment is progressing.
CV - Karl Southerton
Working with various commercial photographers
Moorfields Eye Hospital
City Hospital (Birmingham)
Western Eye Hospital, London