In his seminal book on modern education, Closing of the American Mind, Allan Bloom observed that oftentimes the things that disturb us most about prior civilizations are the very things that
they took most for granted: Child sacrifice. Gladiatorial games. Bell-bottom pants. Modified ETDRS macular photocoagulation
for diabetic macular oedema (DME)? Any retinal-destructive laser procedure for retinal vascular disease?1
It is clear that for progress to take place in medicine, or virtually anywhere else, what we 'know' at any moment will eventually
be shown to be inadequate, misguided, or simply wrong. A glance back in time gives a sobering preview to how the future will
view our present. Monty Python perfectly captured the spirit of this dilemma in their 1970's sketch called 'Everything You
Know is Wrong'. I like to think that Python was deeply influenced by Aristotle, who, without benefit of reading the more highly
evolved thinkers of our own time, noted that while evidence for the advance of human technology was clear, evidence for change
in human nature was absent.2,3
What does this have to do with laser treatment for DME? Nothing. But it has much to do with the humans who think about it
and do it. Information theory states that the amount of new information we can learn from a given event is directly proportional
to the improbability of that event occurring.4 How much do we learn from yet another study confirming that ranibizumab is effective against choroidal neovascularization
from yet another cause? So when something really new and unexpected comes along offering a wealth of new insights and the
prospect of significant advancement, it must, by definition, strike us as very unlikely — if not impossible, and even absurd.
Realization that the ridiculous and impossible may also be the truth makes us, at best, uncomfortable. And if there is one
thing that humans value and defend, it is their comfort. Wars are fought over less.
Effective treatment for retinal disease
The discovery that laserinduced thermal retinal burns could effectively treat retinal disease represents one of the great
advances in the history of ophthalmology. The necessity of laser-induced retinal damage in the treatment of DME has been universally
accepted for almost 50 years, and remains the prevailing notion today.5 So what are we to make of the idea that those very same retinal burns — or any laser-induced retinal damage, for that matter
— are actually unnecessary and simply represent an adverse side-effect of treatment? See 'uncomfortable' above.
In April 2000 a pilot study was started involving laser treatment for DME with, for the first time, the explicit intent of
avoiding laser-induced retinal damage of any kind by use of a low-duty cycled micropulsed 810 nm diode laser (IRIDEX Corp.,
Mountain View, California, USA). At same time, the modest clinical effects anticipated from this invisible ('low-intensity')
laser treatment were sought to be magnified by a fundamental change in treatment technique, permitted by the unique safety
of the micropulsed laser: that of confluent ('high-density') treatment of the target tissue (DME) with contiguous small laser
The pilot study was born of the base desire to avoid replacing a spent argon laser. It succeeded through a little bit of good
intuition and masses of good luck, not to mention sufficient ignorance as to the impossibility of the proposition to give
it a try.6 Reported in 2005, this study stated that 'low-intensity/high-density' subthreshold diode micropulse photocoagulation (SDM)
appeared to be as effective as conventional suprathreshold photocoagulation for DME but without any clinical or angiographic
evidence of laser-induced retinal damage at any point during or after treatment. Without laserinduced retinal damage there
were no complications or adverse treatment effects. SDM appeared to be, in fact, absolutely harmless.7,8 These findings have been corroborated by subsequent studies including randomized clinical trials.10–14 Other reports suggest SDM may also be effective for the treatment of macular oedema due to branch retinal vein occlusion,
central serous chorioretinopathy and proliferative diabetic retinopathy.