Aim: A clinically useful treatment laser must generate stable and precise energy of low diffusivity. This study assessed the photothermal response of a Q-switched ruby laser (QSRL) in the treatment of oculodermal melanosis (Nevus of Ota).Methods: A two-year retrospective review of 40 patients with oculodermal melanosis treated with a QSRL (λ = 694 nm, pulse duration = 25 ns, 3 mm spot size, energy density 6-10 J/cm2) was performed. Demographics included an age range of 18-54 years (mean 28) and a gender distribution of 25 females and 15 males. The values recorded from real-time infrared thermal imaging of the lasered skin were inserted into standard thermal wave equations. This permitted analysis of the resultant temperature distributions related to the energy change.Results: Skin temperature was unchanged during the initial heating stage. This was followed by a very rapid temperature rise. A thermal b injury manifested by dermal-epidermal disruption, resulted when the energy density of the QSRL exceeded 8 J/cm2 (> 44℃).Conclusion: The use of infrared thermal imaging with a standard thermal wave equation allows prediction of skin temperature distribution when QSRL is used for the treatment of oculodermal melanosis. With the use of appropriate settings, complications may be minimized.