Aesthetic nurse prescriber Mary White takes an in-depth look at how lasers function and explains how to use them to effectively treat thread veins
The last decade has brought about big advances in medical laser technology, which have assisted aesthetic practitioners in providing a more effective treatment of thread veins. Broken veins, telangiectasia or thread veins are the small red or blue veins that can appear anywhere on the body and are very common on the face. Thread veins can appear as single veins, widely dispersed, or as a collection of broken veins close together. They can also appear as a collection of vessels arising from a single point, known as spider naevi. Thread veins are caused by a variety of factors including exposure to ultraviolet light, wind and extreme temperatures. Steroid creams and the hormonal changes that occur during pregnancy can also cause thread veins.8 In addition, there is a belief generally amongst practitioners that some individuals are genetically more prone to develop thread veins than others, and some people are more at risk because of old injuries. To understand how to safely and effectively treat facial thread veins using lasers, it is necessary to go back to some basic physics in order to appreciate the principles of how laser light interacts with tissue to achieve the desired result. All lasers have unique characteristics, which determine the outcome of treatment, and what condition a specific laser can effectively treat.
Lasers have certain characteristics that make them unique. Laser light is monochromatic (one colour, or one wavelength), coherent (all the photons are in phase) and collimated (it can be precisely directed). For example, ordinary light from a light bulb or a torch is polychromatic (has several colours) with all wavelengths of visible light present (remember splitting sunlight using prisms in science lessons to show the colours of the rainbow?) and is not coherent or collimated, which means it is scattered in many directions.1 When standing in front of a wall with a torch, the circular light from the torch would be small whilst close to the wall and would get dimmer and more scattered as it retreats from the wall. Compare that with a laser pointer being used at a conference in a large auditorium; the laser spot does not change size or get bigger as the speaker moves around and it can travel a long way around a room. Laser light interacts with targets in many ways, such as reflection, scattering and transmission. However, from my experience when using lasers in dermatology applications, the tissue interaction that is most utilised is absorption. Lasers have a variety of indications, such as cutting, vaporising and coagulation, and they can do this because the target tissue absorbs the laser light. The theory of selective photothermolysis2 states that in order to destroy a selected target, while sparing the surrounding tissue, three basic parameters are necessary. First of all, the colour of the chosen laser light (wavelength) must be one that is absorbed by the target and poorly absorbed by the surrounding tissue. This spares the surrounding tissue from being damaged at the same time by the laser. Secondly, the length of time that the laser beam interacts with the target, that is the pulse duration, must be long enough to destroy the target and is determined by the size of the target. The pulse duration will vary depending on the application you are using the laser for. Finally, in order to destroy or alter the target, it must be heated to a high enough temperature to cause permanent damage to that target.2 Therefore, enough energy must be applied and absorbed for an effective temperature rise.
Another influencing factor when choosing a laser to treat facial thread veins is the depth of penetration of the laser into tissue
Another influencing factor when choosing a laser to treat facial thread veins is the depth of penetration of the laser into tissue. This is dependent upon the wavelength of the laser and also the spot size, with larger spot sizes penetrating deeper than smaller ones. Facial thread veins are fairly superficial and will require smaller spot sizes than, for example, a hair follicle for laser hair removal, which will be more deeply rooted.
Another important parameter to consider when carrying out laser treatment is pulse duration. Pulse duration is the amount of time over which the laser pulse is delivered into the target, in this case the haemoglobin in the blood cells. In order for laser treatment to be effective, the pulse duration must be selected in consideration with the thermal relaxation time (TRT) of the target. The pulse duration must be shorter than the TRT of haemoglobin, but not too short that it causes unwanted side effects, such as hyper/hypo pigmentation or scarring.2
TRT is defined as the time required for the targeted chromophore/structure to cool to half its peak temperature immediately after the laser exposure. Simply put, smaller objects cool faster than larger objects of the same material and it is important to consider how long the haemoglobin will take to cool down, and then choose an appropriate pulse duration.
Finally the energy density that is delivered during laser treatment must be considered, which would vary depending on a number of factors including spot size, wave length and laser manufacturer, and is referred to as fluence and measured in joules/cm2. Fluence takes into account the energy used as well as the area being treated or spot size.
Once the physics is understood, it is easier to see the fundamental difference between lasers and IPL sources. Both technologies can reduce thread veins, but that’s where the similarity ends.
In either case, the damaged veins are gradually dissolved and removed by the body’s immune system over several weeks after treatment, during a process called phagocytosis.6 The Nd:YAG laser in my clinic effectively treats facial thread veins in one to three treatments sessions, lasting approximately five to 15 minutes, with treatments spaced at six to eight week intervals. The treatment sensation is hot, however this is reduced by epidermal cooling, delivered with a cryogen device built into the laser I use. Freezing cryogen gas is delivered onto the treatment area and can be controlled by three parameters: how long to freeze for (in milliseconds), the delay between the cryogen delivery and the laser beam delivery (again milliseconds) and how long to freeze after the laser beam delivery (also in milliseconds). This effectively cools and protects the epidermis and reduces the risk of thermal damage and scarring. With Nd:YAG laser therapy, the thread veins are immediately less visible than before treatment. There may be some skin reaction in the form of intravascular coagulation, which appears as a grey-hued tiny bruise on some larger vessels, particularly around the nose. Other acceptable clinical end points include vasospasm, vessel swelling and ‘sticky’ vessels, which are caused by the microscopic damage to the endothelial cells of the vessel walls, causing them to collapse and then ‘stick’ together, preventing further blood flow through the vessels.7 The latter is probably the best clinical endpoint in my opinion, and when tested with a blanche test, these vessels will not refill and an excellent outcome can usually be predicted. From my extensive experience in treating thread veins, normal sequelae of treatment include erythema, oedema and occasional micro-crusting. These side effects usually disappear after 24-48 hours, but can occasionally last up to seven days.
A common error when administering laser treatment for facial thread veins is the incorrect selection of which laser parameter to alter first. It is often believed that increasing the fluence is the best approach when a clinical endpoint is not achieved. Unfortunately, this usually leads to thermal damage of the treated area and non-selective damage to tissues and, thus, increases the risk of scarring.2
When treating facial thread veins with Nd:YAG laser, the first parameter to alter when clinical endpoints are not achieved is the pulse duration. Larger blood vessels will require heating for longer than smaller ones and when the correct pulse duration is used, selective damage will occur. Because larger objects and structures take longer to cool down than smaller ones with a smaller surface area, larger blood vessels take longer to cool down than smaller ones. Therefore, a longer pulse duration would be selected for wider vessels and a shorter pulse duration for narrower ones.
Using pulse durations that are too short can cause unwanted side effects and carry more risk. A fixed fluence of energy is being delivered over a fixed period of time. If this energy is delivered over a short period of time, e.g. pulse duration 3ms, it comes as a short, strong pulse. However, if this energy is delivered over a longer period such as 30-60ms, it is more gently delivered. It can be confusing to think of pulse duration as being ‘stronger’ when the number is higher but, in fact, it should be considered as gently ‘simmering’ the target with the same energy, just over a longer period of time, rather than delivering a short burst of energy in a short time. The safest way to treat is to adjust the pulse duration first, until a desired endpoint is seen. Only then should the fluence be increased in stages until either intravascular coagulation, or ‘sticky’ vessels are seen.
Facial thread veins can be safely and effectively treated using Nd:YAG laser therapy. The treatment is cost effective as, in my experience, it usually takes under three sessions to clear most unwanted veins. The incidence of recurrence is low with this treatment and side effects are minimal.