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| FACIALAESTHETICS | ARTICLE


Figure 6 Skin resurfacing to the lower eyelids in a male patient


scanned CO2 lasers that limit skin heating revolutionised


the resurfacing industry. These new lasers are capable of removing layers of


photodamaged skin in a precise fashion, leaving only a narrow zone of thermal necrosis. The first laser pass significantly ablates more tissue than the second or subsequent passes, and an ablation plateau is reached at three to four passes, limiting depth to approximately 250 µm. The ability to control the epidermal vaporisation depth with minimal damage to the papillary dermis is a pre-requisite for successful, scorch-free skin resurfacing. The CO2


laser achieves the desired results by removing


the outermost layer of the epidermis and some portion of the superficial dermis, and then re-establishing this layer through normal wound healing. Healthy epidermis migrates from adjacent tissue and adnexal structures, and new collagen and elastic tissue are deposited by activated fibroblasts9


. To respond to these requirements


and achieve well-controlled tissue ablation without the risk of scarring or dyspigmentation, it is important to confine ablation to a thin layer (20–50 µm) and deliver enough energy to vaporise the tissue (5 J/cm2


) in a time The levator palpebra superioris is innervated by


the superior branch of the oculomotor nerve, entering the muscle from its inferior surface in its posterior third. Müller’s muscle requires sympathetic innervation. Postganglionic fibres arise from the superior cervical ganglion and travel superiorly in the neck as a plexus with the internal carotid artery. The fibres take an intracranial course to the cavernous sinus, where they travel through the superior orbital fissure into the orbit via CN branches. The internal and external carotid arteries


contribute to lid arterial supply. The internal carotid arterial supply is from the terminal branches of the ophthalmic artery medially, and the lacrimal artery laterally.


Carbon dioxide lasers The mainstay for skin resurfacing for the past few decades has been the CO2


and implemented in the 1980s, the CO2


replaced deep phenol peels and mechanical abrasion7 CO2


lasers emit light at a wavelength of 10600 nm that is


strongly absorbed by water (the primary chromophore for CO2


light abundant in the skin). Conversion of radiant


energy to heat at the point of absorption instantly raises the temperature of tissue water to more than 100°C, so that the tissue water evaporates7, 8


. The CO2 laser


accurately evaporates the epidermis and dermis, resulting in the reorganisation and strengthening of collagen bundles in addition to epidermal regeneration to rejuvenate the skin. The first CO2


lasers developed used a continuous


wave; however, this technique was not adopted widely owing to significant thermal damage and the high risk of scarring. The advent of short-pulsed high-energy and


shorter than the thermal relaxation time of the skin (1 ms). Two different types of CO2


purpose of skin resurfacing. The first is a high-power, pulsed CO2


5–7 J/cm2 The mainstay for skin


resurfacing for the past few decades has been the CO2


deep phenol peels and mechanical abrasion.


laser.


implemented in the 1980s, the CO2


Developed in the 1960s and laser has largely replaced


lasers are promoted for the


laser that can deliver a treatment fluency of with each sub-millisecond pulse. The


second uses an opto-mechanical flash scanner connected to a conventional continuous-wave CO2


laser. Later, CO2 resurfacing lasers with short


pulse durations (60 microseconds) emerged, which ablate less tissue per pass and leave a narrower zone of thermal necrosis than the original CO2


resurfacing lasers. These newer


systems allow epidermal vaporisation with minimal thermal damage to the papillary dermis. The newer super-pulsed lasers have pulse energies 5–7-times higher than conventional


super-pulsed lasers to maximise tissue vaporisation. This results in pure steam vaporisation with minimal


laser. Developed in the 1960s laser has largely .


Figure 7 Periorbital


rejuvenation in a female patient


prime-journal.com | November/December 2012 ❚


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