## 2 Brachytherapy  
The standard treatment of primary conjunctival melanoma (CM) is local excision followed by adjuvant local therapy or only brachytherapy. This treatment modality is increasingly safe, effective and ever-expanding, although most of the experiences reported in the literature refer to its use for uveal melanoma in which it is considered a standard treatment for small or medium-sized tumors, \(\leq\)10 mm in apical height and \(\leq\)16 mm in diameter [13; 14]. In CM, adjuvant treatment is important to improve tumor control and patient survival, especially when surgical margins are positive. Adjuvant therapy includes brachytherapy, cryotherapy, topical mitomycin C, proton beam radiotherapy, or alpha 2b interferon. Size and localization are important parameters of choice of these treatments to use [15]. Eye brachytherapy can use radionuclides emitting low-energy photons (125I, 103 Pd, or 13 ICs) or beta rays (106 Ru/106 Rh or 90 Sr) [15; 16]. Radionuclides emit several low-energy, in the X-ray range (20-35 keV), photons with different intensities. In this case, the photoelectric effect, in which photons transfer energy to electrons, is the predominant effect. The choice of devices depends on the operator's experience, properties of the specific radio-isotope, size and the method of use [16; 17]. Custom plaque design can reduce unnecessary radiation to nearby healthy structures, reduce treatment time and increase its effectiveness. The 13 ICs source provides a slightly more uniform dose distribution than the other sources, but the DVHs of these plaques (I, Pd) show a similar trend. Palladium-103 has a biologically effective dose better than I-125. Due to the rarity of the disease, there is not numerous data on the various ways of delivering brachytherapy [17]. Currently, there is no standardized dose protocol for the irradiation of intraocular tumors with 106 Ru eye plaques; in fact, there are two different methods of delivery (high dose: 290-320 Gy or low dose: 100 Gy), while, for I125 eye plaques, the minimum dose required for tumor control should be at least 85 Gy [15; 16; 17; 18; 19]. Iodine plaques are usually used to treatarsal conjunctival melanoma after primary excision. Even for Sr-90 there is not a standardized regime, but, on average, the total dose is 36-60 Gy and fraction size is typically 10 Gy, and it is preferable for lesions of the bulbar conjunctiva for the shape and the size of the applicator. The technical characteristics of the applicators may constitute a limitation for their use in cases where the ocular anatomy does not allow it. Strontium treatment using a hand-held applicator, and treatment is used in the Academic Medical Center (Amsterdam, the Netherlands) or Catharina Hospital (Eindhoven, the Netherlands) as in those centers a Sr-90 applicator was available. In these centers is dispensed a dose of 60 Gy in 6 fractions, 10 Gy at a time, at the conjunctival surface. The application lasts 60-90 s. While Ru-106 brachytherapy is used in Leiden University Medical Center (LUMC, Leiden, the Netherlands): 100 Gy in a single dose are dispensed in this center, 2 mm deep because all the lesions had been removed. Treatment time was variable and there were different types of plaques of different shapes and sizes. From 2012 onwards, in patients with primary acquired melanosis (PAM) in addition to CM, the topical use of mitomycin and brachy therapeutic treatment with Ru-106 [10; 18]. There are no statistically significant differences in the development of relapses, metastases or deaths between the two treatments; according to [PERSON], even the treatment with I-125 plaque does not differ much from the results with Ru-106 and Sr-90, but Ru-106 reduces local toxicity compared to Sr-90 [15; 16; 17; 18]. Moreover, the adjuvant treatment with Ru106 had the same total recurrence rate as the treatment performed by [PERSON], who applied the same dose at a depth of 1 mm [10].