Micropulsed Laser in Patients With Macular Oedema in Retinal Dystrophies

BACKGROUND:

Degenerative diseases of the visual system classified as rare and, in particular, those affecting the retina (known as Inherited retinal dystrophies, IRDs) cause very severe functional deficits. Their onset is in many cases particularly early with a consequent visual impact of extreme severity. They constitute a heterogeneous group from a clinical point of view, but in all of them the loss of photoreceptors causes progressive vision loss that can result in complete blindness.

These pathologies can be complicated by the presence of cataracts, epiretinal membrane and macular oedema (10-50%), resulting in a worsening of visual acuity. While surgical treatment is applicable for the first two complications, the treatment of macular oedema can make use of several options. Oral or topical diuretics (Acetazolamide) are still the first therapeutic approach and, if oedema persists despite treatment, intravitreal corticosteroid injection has been used in various reports. The injection of anti-Vascular Endothelial Growth Factor (VEGF) drugs and vitrectomy have also been proposed but with conflicting results. The use of topical non-steroidal drugs has been studied and proven to be valuable, although inferior to diuretic treatment in terms of visual recovery. The use of intravitreal corticosteroids is also not without possible further complications such as ocular hypertension and early onset of cataracts.

Despite some improvement in retinal oedema by taking the above-mentioned diuretics, relapses can be observed at the end of therapy, reason for taking longer periods (\>12 weeks) of therapy. However, the same chronic continuation of diuretic therapy is not always desirable considering its possible adverse events such as tingling sensation, malaise, altered taste sensation and gastrointestinal disorders.

RATIONALE:

The application of the micropulsed subthreshold retinal laser to reduce retinal oedema in various diseases (diabetic oedema, central serous chorioretinopathy, age-related macular degeneration and retinal vein occlusion) has recently gained wide acceptance.

Retinal threshold refers to the tendency of the laser to cause tissue bleaching resulting in retinal cell death, the term sub-threshold implies that the laser uses such a small amount of energy that it does not cause irreversible damage to retinal structures. The term 'micropulsed' derives from the fact that the laser does not use a continuous wave but has a sub-100% duty cycle and the use of 'off' times is what distinguishes this type of laser from conventional lasers and allows the tissue to cool down, preventing laser-induced retinal damage.

The main characteristics of this type of laser are therefore that it does not cause visible retinal damage and that it has therapeutic effects.

One theory of how this type of laser works is through the action of the molecular protective mechanisms of the Heat Shock Protein (Hsp) family in the retina, including protein chaperone activity, stabilisation of the cytoskeleton and prevention of apoptosis mainly through inhibition of cytochrome C release through the phenomenon of 'resetting'. Another theory hypothesized the activation of leucocyte recruitment or remodeling of the extracellular matrix in the choroid and retina. Possible mechanisms of increased trophic factors (CNTF and FGF-2)14 and up-regulation of other factors (MMP-2, MMP-3, TNFα and Nos2) are covered.

TRIAL DESIGN:

Prospective, interventional, single-centre, open-label study involving consecutive enrolment (see sample size in section "Statistics") of patients with macular oedema in retinal dystrophies.

Each patient referred to the Outpatient Clinical and Research Center of Neuro-ophthalmology and Genetic and Rare Diseases with IRD and macular oedema treated for 3 months with diuretics and draining food supplements and without improvement of macular oedema or increase of the same (reduction of post-therapy CRT ≤20% compared to pre-therapy CRT) will be duly informed about the therapeutic option of this study protocol. After verification of the criteria for inclusion in the study and after signing of the informed consent, the patient will be considered eligible for treatment with micropulsed laser by the physicians of the Clinical and Research Center of Neuro-ophthalmology and Genetic and Rare Diseases and Medical Retina. The patient enrolled in the study will be clinically analysed with the instrumentation indicated below at regular intervals (screening/baseline, follow-up 1 \[FU1\] (1 month), FU2 (3 months), FU3 (6 months), FU4 (9 months), FU5 (12 months), FU6 (18 months) and FU7 (24 months).

• To study changes in visual acuity between before and after treatment [Срок оценки: up to 24 months]
• To study the retinal function in the macular area before and after treatment. [Срок оценки: up to 24 months]
• To study the retinal perfusion of the macular area by OCT-angiography before and after treatment. [Срок оценки: up to 24 months]