## 4 Discussion  
Several studies have investigated different low-level laser and light sources with related treatment parameters for the management of alopecia, like LLLT [19, 20, 21, 22, 23, 24], various wavelengths of LED light [25, 26], and several other techniques that are combined, such as LED-LLLT [27]. Although the available literature regarding phototherapy-based devices to treat AGA is restricted, the study results regarding the outcomes showed a more robust performance than those reported in previous studies. [PERSON] et al. (2009) [27] conducted a 26-week, randomized, double-blind, device-controlled, multicenter trial during which 110 male patients with AGA Ila-V were randomized for treatment with the HairMax LaserComb(r) [27]. The primary efficacy endpoint was the mean terminal HD. At 26 weeks, HD had an average increase of 19.8% in the patients of the study group. [PERSON] et al. (2013) [20] performed a randomized, double-blind, sham device-controlled trial at two research centers that included 40 male and female subjects with AGA treated with a helmet-type 3R LLLT device, with a lightweight source consisting of LEDs emitting wavelengths of 630 nm (3.5 mW, 24 units, L-513 ECA) and 660 nm (2.5 mW, 18 units, L-513 LRC) and an LD with wavelengths of 650 nm (4 mW, 27 units, DL3147-060) [20]. The primary efficacy endpoint was HD after 24 weeks of treatment estimated with trichograms. Six months after the last procedure, the mean percentage of the increase in HD was 14.7%. Finally, [PERSON] et al. (2018) [28] conducted a 24-week, prospective, randomized, double-blind, device-controlled run that included male subjects aged over 18 years with AGA that were treated with RAMACAP, a combat helmet-shaped device containing single-mode LDs which emitted a wavelength of 660 \(\pm\) 10 nm [28]. The first efficacy endpoint was HD and the hair diameter in the TA at weeks 8, 16, and 24, by photographing the TA with a Folliscope(r) and measuring it with Folliscope 2.8 software (LeadM Corporation, Seoul, Korea). Six months after treatment, the mean percentage of an increase in HD was 9.1%. However, there was a significant difference between light and laser sources. Thirty-two home-use LLLT devices cleared by the US-FDA were found and analyzed in the literature through several studies, including seven randomized clinical trials (RCTs) (such as 1 Capillus(r) [29], 2 HairMax(r) [27], 2 iGrow(r) [30, 31, 32], and 2 iRestore(r) [33, 34]), and two cohort studies (one perspective [35] and one retrospective [36]) to support the efficacies of home-use LLLT devices. The subjects in most of the RCTs had mild to moderate patterned hair loss, MPHL (NW grade IIa-V) and/or FPHL (LW-Savin Baldness Scale I-2, I-3, I-4, II-1, and II-2). The duration of studies ranged from 16 to 26 weeks, with a mean duration of 21.3 weeks. For the assessment, most RCTs showed positive results of an increase in microscopic hair counts. The majority of the LLLT treatment groups yielded a statistically significant improvement in hair counts compared to the control group. In two non-controlled trials [35, 36], LLLT also demonstrated an improvement when compared to baseline, with no provided \(p\)-value. Meanwhile, there was one RCT that also studied the effectiveness of a helmet LLLT device in combination with topical minoxidil in FPHL [37]. The application protocol differences of LLLT devices included the shape, light source, number of LEDs and LDs, the wavelength, and the total power output. Due to no head-to-head study to evaluate the devices, the clinical benefits of one over the other cannot be determined. When considering the number of diodes, the comb-type LLLT devices used the least number of diodes, ranging from 7 to 12 diodes. Besides, the prices of the comb-type LLLT devices were cheaper than other shapes and proved clinical effectiveness [31]. Therefore, they could be good options for patients with financial limitations.