What does the treatment involve?
Photodynamic therapy is a treatment involving the endovenous injection of an active principle called verteporfin which is subsequently activated for 83 seconds with a non-thermal laser.
During the session, a contact lens is put in place to locate the spot in the area we wish to treat just like we do with conventional laser treatment. Anaesthetic drops are put in the eyes so that the patient does not experience any cornea irritation.
The duration of exposure to the laser can be reduced in half if required in certain cases. It is an outpatients treatment and the patient is recommended not to expose themselves to direct light for two days given that, being a photosensitive substance, it can cause wounds to the skin.
The objective of photodynamic therapy is to stimulate platelet aggregation and cause an obliteration of the vascular structure we wish to treat
When is the treatment indicated?
At the start of the 2000s, photodynamic therapy was the treatment of choice for age-associated macular degeneration, the main cause of blindness in the Western world.
It was the first treatment to change the natural history of this disease and was a real revolution in the world of ophthalmology. In spite of the treatment, the patient continued to lose visual acuity quite quickly.
This treatment is currently relegated to second place as a treatment, replaced by anti-VEGF intravitreal injections that give anatomical results and in terms of visual acuity are clearly superior to those acheived by photodynamic therapy.
In any case, sub-types of age-associated macular degeneration, such as polypoidal choroidal vasculopathy still have a clear indication, almost always associated with intravitreal injections.
Another pathology with a clear treatment indication is chronic central serous chorioretinopathy. These are cases where the symptoms do not go away themselves (which happens with the majority of patients) and we want to accelerate the reabsorption of liquid stored under the macula
Another current indication of photodynamic therapy with verteporfin is symptomatic circumscribed choroidal hemangioma. It is a benign tumour of the vascular tissue located in the choroid. The desired result is the reduction or elimination of the liquid stored under the macula, as it is responsible for the reduction in visual acuity.
Possible risks
Although not thermal but still a type of laser, a corneal contact lens must be used. In very few cases, cornea alterations may be experienced, such as mild erosions or keratitis.
Once the treatment has been provided, it is normal that the patient has blurred vision for a few days given that temporary inflammation occurs in the retina without leaving any side effects.
As mentioned before, the patient must stay away from direct light for 48 hours as it can cause redenned skin and wounds, in more severe cases.
It is recommended that the patient leaves the treatment room wearing long sleeves and trousers to reduce the body's exposure to the sunlight. High intensity hallogen lighting must be avoided at all costs, such as that found in surgical theatres, the dentist's room and tanning salons.
Haematomas that are reabsorbed after a few days derived from the endovenous injection may also form.
In some patients, backache may also occur at the time of the infusion of the drug. It is usually temporary and does not require treatment.
The only absolute contraindication is in patients who are allergic to porphyrin.