Radio waves are found at the long range of the electromagnetic spectrum, with wavelengths extending well beyond 30cm, which is longer than infrared. Radiofrequency (RF) energy is used in our daily lives for telecommunications and broadcast services (radio and television), navigation systems, satellite communications, computer and mobile networks, remote controls, etc. (Lucas, 2015). RF is also used in other fields such construction for industrial heating and sealing processes (CPWR, 2020).
Radiofrequency in Medicine
Radiofrequencies are used extensively in the medical field, with primarily a thermal effect on living tissue whereby the controlled heating can be used to cut, coagulate, or induce metabolic processes in the target tissue (Elsaie, 2009; Ihnát et al, 2014).
RF is most often used in cosmetic dermatology for skin rejuvenation including treatments such as skin tightening, face contouring, atrophic scar revision, treatment of inflammatory acne, reduction of adipose tissue, etc. (Gentile et al, 2018; Vale et al, 2018). The RF devices heat specific layers of the skin, and the healing process promotes the remodeling of collagen, which clinically enhances the appearance of mild-to-moderate skin laxity (Elsaie, 2009).
RF has also been used in the treatment of chronic pain conditions to create an irreversible thermal lesion on nerve fibers by increasing the temperature sufficiently, which permanently interrupts pain signals (Ojango, 2018). An example is RF thermocoagulation to treat trigeminal neuralgia (Zakrzewska and McMillan, 2011), which is an ablative surgery in which the semilunar ganglion or trigeminal nerve branch is punctured by a RF needle with the guidance of computerized tomography or X-ray imaging (Li et al, 2019).
RF ablation has been shown to induce antigen-presenting cell infiltration and to enhance systemic antitumor T-cell immune response and tumor regression in pancreatic, liver, and breast cancers (Reccia et al, 2018; Ito et al, 2018). RF ablation has also been used in the treatment of reflux of the great saphenous vein (the longest vein in the leg), which is the most common cause of chronic venous insufficiency. With RF, the energy induces a thermal injury and seals off the great and small saphenous vein. In comparison with traditional surgery, this technique offers comparable efficacy with lower morbidity and faster recovery (Ihnát et al, 2014). RF technology can also be used diagnostically to image vascular changes, such as the evaluation of subclinical atherosclerotic changes (Ozisler and Kaplanoglu, 2019).
Radiofrequency in the Eye
RF can be used in the treatment of eye conditions such as conjunctivochalasis (CCh), a condition characterized by redundant, loose, and non-edematous bulbar conjunctiva. CCh can cause symptoms of ocular surface irritation similar to dry eye and can lead to decreased tear film stability and delayed tear clearance, which can increase ocular surface inflammation (Trivli et al, 2018). RF has been used successfully to ablate the redundant conjunctiva, offering a shorter procedure and recovery time over surgical excision techniques.
RF has also been used in conductive keratoplasty (CK) for the correction of hyperopia by deepening the central cornea. A fine tip is inserted into the peripheral corneal stroma at eight-to-32 points, and a precise amount of RF energy is delivered. The surrounding area heats up, and the collagen shrinks in a controlled fashion, constricting the cornea and increasing its curvature. This technique has shown promise, as it spares the visual axis, does not require a creation of a large flap, and is not associated with postoperative dry eye (McDonald, 2005).
RF technology has been advantageous in the treatment of congenital fibrovascular pupillary membrane, with reduced risk of iatrogenic cataract, less bleeding, and with minimal disturbance of the iris (Wang et al, 2019).
Some ocular side effects, such as cataracts, have been reported in animals with the use of RF energy (Elder, 2003). Side effects after long periods of exposure to low-level RF energy have not been confirmed in human populations (Elder, 2003).
The most common problems reported during RF cosmetic procedures are ocular pain, photophobia, and conjunctival hyperemia (Ricci et al, 2015).
More recently, RF technology has been explored for the management of dry eye disease. RF needles have been used for punctal occlusion for patients who have aqueous tear deficiency (Bhavsar et al, 2011). Additionally, there has also been a growing interest in the use of RF in the management of meibomian gland dysfunction (MGD). Following RF for skin rejuvenation, patients reported an improvement of their dry eye symptoms and required less artificial tears (Johnson, 2019). It is hypothesized that the heat produced by the RF energy may have a positive effect on MGD through the localized heating and stimulation of the nerves supporting the meibomian glands.
A pilot study using RF technology for dry eye reported improvements in symptoms using the Ocular Surface Disease Index (OSDI) and Standardized Patient Evaluation of Eye Dryness (SPEED) questionnaires (Christensen and Hauser, 2017). RF treatments were performed at Day 1, 15, and 30; 72% of participants noted an improvement of their dry eye as early as the second treatment, with some reporting a prolonged effect weeks post-treatment.
A comparative study between a RF device and thermal pulsation revealed an improvement with RF in the symptom scores, meibomian gland expression, and conjunctival staining (Jaccoma et al, 2018). Although these preliminary results are promising, the sample size of the study was limited (n = 10), so further studies are needed.
Much still needs to be uncovered concerning the role of RF technology and its potential for the management of dry eye disease. Interest in the technology has prompted studies to determine its efficacy with regard to MGD (NCT04120584); however, more studies are needed to gain a better understanding of the underlying mechanisms of RF technology in the management of dry eye disease including its overall safety and effectiveness. CLS
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