One of the most rewarding aspects for me as a healthcare provider for more than four decades has been to experience tremendous advances in eye care, especially in the diagnosis and management of ocular surface diseases. I recently learned about technologies that use various forms and wavelengths of light to treat anterior segment ocular conditions including dry eye disease (DED).
For example, photobiomodulation, also known as low-level laser therapy, has been in existence since 1967 (Hamblin, 2016), but it has been utilized for treating ocular conditions only within the last decade. Like so many therapies in health care, it was discovered serendipitously.
Origins of Photobiomodulation In a search for a non-surgical therapy for cancer, Hungarian researcher Endre Mester treated surgically implanted tumors in rats with low-power laser energy (Hamblin, 2016). Although this therapy failed to eliminate the tumors, Mester noted that rats treated with low-power laser showed an enhanced rate of hair growth and improved wound healing (Gáspár, 2009).
Over time, light-emitting diodes (LEDs) have largely replaced lasers as the source of energy for this technology. Early on, it was referred to as low-level light therapy (LLLT); however, photobiomodulation has become the preferred terminology (Anders et al, 2015).
The mechanism of action by which photobiomodulation exerts its beneficial effects remained a mystery until Russian researcher Tiina Karu identified cytochrome c oxidase in the mitochondrial respiratory chain and introduced the hypothesis of “retrograde mitochondrial signaling.” This explains how a single, relatively brief exposure to specific forms of light exerts a positive effect on tissue (Hamblin, 2016; Karu, 2008).
Treatment for Xerostomia Dry eye and xerostomia (dry mouth) are two well-established features of Sjögren’s and often present concomitantly. Simões et al (2009) reported the case of a 60-year-old woman diagnosed with Sjögren’s who was referred for laser phototherapy of severe xerostomia.
She underwent diode laser radiation therapy of the parotid, sub-mandibular, and sublingual glands three times per week, for a period of eight months. The salivary flow rate and xerostomia symptoms were measured before, during, and after treatment. Her xerostomia improved, and after completion of the treatment, the parotid and salivary gland pain and swelling resolved.
Intense Pulsed Light for Meibomian Gland Dysfunction
Meibomian gland dysfunction (MGD) is the most prevalent single underlying cause of dry eye (Lemp et al, 2012). Vigo et al (2019) evaluated the efficacy of intense pulsed light (IPL) for treating dry eye-associated MGD. They examined 19 subjects before and after they underwent three sessions of IPL treatment consisting of high-intensity pulses of polychromatic lights with a broad range of wavelengths (515-to-1200nm). Anticipated outcomes included selective photocoagulation and ablation of superficial eyelid blood vessels and telangiectasias, reduced levels of inflammatory mediators, and improved meibomian gland secretion.
The majority of the treated patients (17 of 19; 89.5%) perceived an improvement of their ocular discomfort symptoms after IPL treatment. The authors concluded that IPL was beneficial in managing MGD-associated dry eye, but they anticipated that repeated treatments would be necessary to retain its beneficial effects (Vigo et al, 2019).
Adding to the Armamentarium
At a time when dry eye is becoming increasingly more common in individuals of all ages, with MGD widely regarded as a significant contributor, the advent of additional non-invasive, efficacious treatments is encouraging news for eyecare providers and their patients. CLS
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