Intraocular therapy has revolutionised the ophthalmology field, specifically the treatment of diseases originating in the retina, the most serious of those affecting the eye. Among the latter, the diseases that have the greatest impact are degenerative diseases, in particular age-related macular degeneration (AMD); those that are associated with high myopia; those that are vascular in origin, mainly diabetic retinopathy; and those that are associated with biomechanical problems, such as vitro-macular traction syndromes.
Treatments replacing or complementing surgery
To treat these diseases, in recent years there have been significant advances in retina surgery, with the perfecting of techniques and instruments that facilitate minimally-invasive surgery, and which, as a result, improve visual results and enable patients to recover in a shorter space of time. However, new steps are being taken for drug treatments to replace or complement surgery. These alternatives are drug therapies that, through intraocular injections, act locally on the inside of the eye, particularly on the retina and, more specifically, on the macula (central zone of the retina responsible for detailed vision). The Barcelona Ocular Microsurgery Institute (IMO) has spent more than a decade taking part in various international studies to assess the efficiency of these new treatments for diabetic macular oedema, retinal thrombosis and AMD, among others.
Improved visual results
According to Dr. Rafael Navarro, a retina specialist at IMO, “despite the fact that, in many cases, adequate treatment with these new drugs requires multiple injections, since their effects last for several weeks or, in the best cases, several months, generally speaking intraocular treatment improves the visual result of patients compared to previous treatments and, in many cases, avoids having to resort to surgery with the risks this involves”. The most obvious case is the treatment of age-related macular degeneration (AMD) in which the injection of antiangiogenic drugs, which slow down the growth of abnormal blood vessels growing in the retina, has become the reference treatment for wet forms of the disease. The treatment is based on an important discovery: so-called endothelial growth factors, which are the cause of various forms of cancer, diabetes and retinopathy in premature babies, among other pathologies, which cause the growth of new blood vessels in these tissues and which current treatment manages to combat by injecting antibodies into the eye. “This new option has revolutionised the visual prognosis of patients, since 70% maintain or recover vision with this intraocular treatment compared with 20% with other treatments such as laser, surgery and photodynamic therapy" explains Dr Rafael Navarro.
Despite the positive results, the treatment currently requires a monthly injection while signs of the disease exist, something that the ophthalmologist determines by monitoring the same using OCT (Optical Coherence Tomography), a scan used to capture high-definition tomographical images of the eye. With a view to improving treatment and the patient's quality of life, tests are already being carried out on drugs with an action that lasts twice as long as the current drugs, and we hope that from the beginning of next year in some cases treatment will only be required every two months.
Application in vascular retina diseases
Intraocular injections are also used with positive results in cases of vascular retina diseases such as macular oedema, which causes a build-up of liquid in the macula and up until now has only been treated with laser, with very limited results. Intraocular drugs that reduce this inflammation (anti-angiogenics and steroids) are used in patients who cannot be treated with laser or in whom this treatment achieves poor results. A little over a year ago the use of one of these drugs was approved, based on a long-acting injectable and biodegradable corticosteroid implant (dexamethasone) for the treatment of macular oedema in patients with retinal vein occlusion (RVO), the second most common cause of vascular retina disease after diabetic retinopathy, and a common cause of significant vision loss. The new implant acts locally to control the oedema, reduce inflammation around the occlusion and thus improve the patient's visual acuity. Its effect lasts for approximately four months. Dr Rafael Navarro is currently coordinating an international and multicentre clinical trial in Spain for the treatment of another type of macular oedema, diabetic macular oedema, the diabetic retinopathy complication that is most harmful to vision. The trial is expected to last for one year and "seeks to compare two treatments based on intravitreal injections to determine which of the two achieves better recovery of the patient's visual acuity with fewer injections", explains IMO specialist.
Positive results in high myopia and macular hole
Another group of people benefitting from new intraocular injections are those suffering from high myopia (over 6-8 diopters) in which the risk of retinal complications is increased. Intraocular treatment has revolutionised the visual prognosis in cases of myopic vascular membranes in the macular area and, also, the results in such cases are better than for other retinal diseases, since 90% of these patients require only one or two injections to recover vision. Intraocular microplasmin injections, a drug used to separate abnormal adhesion of the retina and vitreous gel without the need for surgery, is one of the latest advances in intraocular therapy and is used in vitro-retinal traction syndromes of the macula and in some cases of macular hole.
Hopes for hereditary retina pathologies and dry AMD, for which there is still no effective treatment
"At present, the intraocular therapy field is developing at a dizzying speed, which leads us to hope that we will soon have new intraocular therapies, such as the injection of slow release neurotrophic factors for example for the treatment of hereditary retina diseases or dry AMD, diseases that currently have no effective treatment method”, announces Dr Navarro. New delayed release systems are also being studied for any drug injected into the eye to remain active for a longer period of time, even years, which will greatly improve the quality of life of patients so they can control the disease with fewer injections.