Laser treatment of the Retina : a brief history!

" When, according to Greek mythology, Prometheus gave man the gift of fire (an act for which he was severery punished by the gods) it was one of the most important steps in the history of mankind." 

 The use of HEAT in the history of medicine goes back to antiquity. Heat and fire were used to sterilise wounds and stop bleeding since ancient times. 

The use of heat in ophthalmology also has quite an interesting history.

 

Jules Gonin

Jules Gonin, a French ophthalmologist was the first to use a heat cautery to treat retinal detachment for the first time. A metal filament was heated on a flame and inserted into the eye to cauterise the retinal break. (For a non medico : Consider this procedure similar to a soldering iron. When you solder a metal, it melts and gets attached to another metal with which you intend to attach it. A heat cautery would do a somewhat similar thing! It would attach the detached retina back to its original position.) In those days this was quite a revolutionary procedure! Earlier, retinal detachment practically meant that a person went blind. Gonin's procedure  ("Ignipuncture") meant that patients with retinal detachment could hope to retain useful vision. 

 

Gerhard Meyer Schwickerath

Cut to post world war Germany where a young 25 year old doctor called Gerhard Rudolph Meyer - Schwickerath seemed quite interested with Gonin's experiments. He wanted to construct a diathermy machine ( One which uses electrical current to coagulate tissues) for the treatment of retinal detachment in a principle similar to Gonins'.

 

At that time Gerhard was also supervising a medical students' thesis - In which the student described his own retinal burn which was acquired while looking at the sun during the solar eclipse of 11th July 1945. 

This was infact quite a remarkable observation for young Gerhard. Gonin had created a retinal burn using heat. Gerhard himself planned to improvise it by producing a retinal burn using electricity. Now here was a case where a similar retinal burn was produced using, well, sunlight!

 

Ignipuncture and retinal cautery were invasive procedures and so carried certain procedural risks. Light coagulation was non invasive and hence carried lesser risks. In young Gerhards' mind such an innovation would have tremendous benefit in treatment of retinal detachment and also small eye cancers. He could very well limit the spread of retinal detachment of he applied sunlight burns around retinal breaks. Similarly he could easily burn off small retinal tumors before they became life or sight threatening. The question now was how do you create retinal burns using light and more so how do you do it predictably. 

Dr Gerhard used a machine utilising carbon arc ( similar to the one used for welding) to create retinal burns in rabbit retinas. He tried doing the same in human eyes having ocular tumors ( melanomas) but the results were quite disappointing. 

He then decided to harness the power of the Sun to produce retinal burns!

 

He constructed this new equipment, using a set of lens, mirrors and diaphragms and placed it on the roof of the eye hospital. A heliostat was used to compensate for the movement of the earth so that the procedure could be performed. Typically, a fully dilated patient wearing sunglasses was asked to sit with the machine on the roof. When the weather was clear and a prolonged period of sunlight was expected, the patient was supposed to call the doctor by phone. But unfortunately most times, by the time everyone was ready to perform the photocoagulation, the sun would disappear! The session would then have to be postponed for another sunny day! Clearly this dependence on the sun and seasons to perform therapeutic procedures wasn't a great idea!

 

In 1956, Zeiss first introduced the Xenon Arc photocoagulator in association with Dr Gerhard. This machine used xenon, an inert gas to produce a strong beam of light which could be then focussed on the eye tissues to produce coagulation. This was the first ever retinal laser machine to be available commercially. The Xenon photocgulator was a huge machine, in terms of the real estate it ocupied. Morever the burns it produced in the eye were quite large and painful. Around 2-3 % patients who underwent Xenon Arc photocagulation developed retinal membranes and distortion of the central retina and hence central vision. Most patients undergoing laser needed to be injected with an anaesthetic solution around the eye to reduce the pain and ensure patient cooperation. 

Subsequent iterations of retinal laser machines were more refined and easier to use. Krypton and Argon laser photocagulators were developed which had significantly lesser collateral damage. The were easier to use, caused minimal patient discomfort and did not require injectable anaesthesia for the procedures.

The development of laser photocoagulation was a watershed moment in the non surgical treatment of retinal conditions. It was initially used by Meyer Schwickerath in the treatments of retinal detachments and to destroy retinal tumors. It was subsequently noticed that the same technology could be used to destroy certain abnormal blood vessels inside the eye ( hemangiomas, Von- Hippel tumors, Sickle cell disease.) 

In the 1980s the role of retinal lasers in the treatment of diabetic retinopathy was well established. Cases of severe Proliferative Diabetic retinopathy who were administered retinal laser did far better than those who were'nt. As the technology for diagnosis and imaging of the retina increases, the spectrum of conditions for which laser could be used also increased.  Doctors could now, very accurately pinpoint the leaking vessels inside the retina using angiography. Laser beam could then be used to "coagulate" the leaking vessel and thus reduce the swelling inside the retina. 

Currently the most commonly used laser in retina is the frequency doubled Nd Yag laser. As compared to the first prototype, the current laser console is probably smaller than a small briefcase. It is easily portable and can be used in the outpatient department as well as inside the operating room. Retinal lasers are typically day-care procedures and do not need any specific preparations to be performed. With sub-threshold and multi-spot options, patient compliance is also quite good.

          Looking back at the history of the development of this useful treatment , it is indeed                interesting to see where we stand today and what the future might hold.

            References : 

Meyer-Schwickerath GR. The history of photocoagulation. Aust N Z J Ophthalmol. 1989 Nov;17(4):427-34. doi: 10.1111/j.1442-9071.1989.tb00566.x. PMID: 2696498.