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asers have been used in medical practice
since the early 1960s when pioneers of
the technology, notably Dr Leon
Goldman, investigated the interaction of laser
light on biological tissues and carried out early
clinical studies on humans. A great proponent
of ‘bloodless surgery’, so-called as the laser
cauterises blood vessels while the incision is
made, Goldman supervised the first removal of
a tumour using a laser in 1966.
In the mid 1960s, ruby lasers and argon ion
lasers were developed. Emitting a wavelength
in the blue-green area of the visible spectrum,
which is absorbed well by haemoglobin, was
suited to retinal surgery. Laser technology has
now progressed considerably and various
accepted medical practices in ophthalmology
use laser systems to treat diseases of the eye.
Age-related macular degeneration (AMD) is
one such disease and one of the commonest
causes of blindness in the western world. The
disease affects the macula, a part of the eye
located in the centre of the retina that allows the
eye to resolve fine detail. The causes of AMD
are unclear, but onset becomes increasingly
likely over time as the macula is damaged and
worn out, and patients older than 60 are
particularly susceptible. It is estimated that, in
the western world, one in 50 people aged 50
years and above, and up to one in five people
aged 85 and above, have AMD, and with an
aging population the number of people
diagnosed with the disease is growing.
There are two forms of AMD: wet and dry.
Wet AMD occurs when abnormally growing
blood vessels, which are often fragile, in the
retina leak fluid – raising the macula from its
position at the back of the eye and causing rapid
damage. Dry AMD, which is the much
commoner form, is the slower degeneration of
Sight for
light-sensitive cells in the macula leading to a
gradual blurring of the central vision.
The treatment for wet AMD is decided on a
case-by-case basis, but where the damaged
blood vessels are located outside the fovea,
photocoagulation is generally the recommended
sore eyes
treatment method. Photocoagulation involves
using a laser to produce local cauterisation of
the damaged blood vessels, thereby preventing
further bleeding.
The target for the photons of light is
oxygenated haemoglobin, which has an
absorption peak of 577nm. ‘Twenty to thirty
years ago, ion-pumped dye lasers were used,
Greg Blackman investigates how laser systems are but in the late ‘80s the more reliable, heat
used in medical practices, from eye surgery to
efficient solid-state technology came into effect,’
explains Matthias Schulze, director of marketing
removing varicose veins at Coherent, a supplier of photonics-based
LSEspr09 pp14-15 Medical.indd 14 3/3/09 10:43:32
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