When brown spots appear on the face, many patients may feel that they are all similar to melasma.

 

However, in actual clinical practice, melasma and solar lentigines are often different types of lesions.

 

Melasma usually appears as broad, hazy pigmentation, while solar lentigines often appear as relatively well-defined brown spots.

That is why the treatment approach also needs to be different.

 

Melasma often reacts sensitively, so aggressively burning the area is not always the right approach.

 

On the other hand, solar lentigines are often pigment lesions located more superficially in the epidermis. When the lesion is clearly identified, spot treatment may be a more suitable approach.

 

Simply put, melasma treatment is closer to controlling a “broad background color,” while solar lentigo treatment is closer to selectively reducing “distinct spot-like pigmentation.”

 

Today, I would like to explain what solar lentigines are, why toning alone may sometimes be insufficient, and what actual research has shown when comparing picosecond and nanosecond lasers :)

 

If you look at the photo above, solar lentigines usually appear as small brown spots.

 

Unlike melasma, which tends to spread broadly and hazily, solar lentigines often show relatively visible borders.

 

They commonly appear on areas with frequent sun exposure, such as the cheekbones, cheeks, forehead, and backs of the hands.

 

That is why they are called solar lentigines.

 

In simple terms, they are pigment lesions strongly related to sun exposure.

 

However, not every brown spot on the surface is a solar lentigo.

 

It could be freckles, melasma may be mixed in, or acquired bilateral nevus of Ota-like macules, also known as ABNOM, may be present together.

 

In some cases, a lesion that first looks like pigmentation may actually be a slightly thickened surface lesion, such as seborrheic keratosis.

 

So the first step in solar lentigo removal is not choosing a laser.

 

It is separating and identifying the lesion.

 

We need to distinguish whether it is melasma, a solar lentigo, freckles, ABNOM, or seborrheic keratosis before deciding the treatment direction.

If you look at the image above, the treatment approach can differ depending on how deep the pigment is located in the skin.

 

Solar lentigines are often mainly epidermal pigment lesions.

 

In other words, the pigment is commonly concentrated in a relatively shallow layer rather than deep within the skin.

So if the lesion is clearly defined, selectively targeting the lesion with spot treatment may be more appropriate than repeating broad, low-energy toning.

 

Melasma is different.

 

Melasma is not simply an epidermal pigment problem. It is often connected with the skin barrier, vascular response, inflammation, hormones, and UV exposure.

 

So if melasma is treated aggressively like a solar lentigo, it may become more sensitive or even darker.

 

If this difference is not understood, patients may end up asking, “Why is my pigmentation not disappearing even though I keep receiving laser treatments?”

 

These two treatments have different goals.

One commonly used laser for solar lentigo removal is a 532 nm pigment laser.

 

This is where picosecond lasers and nanosecond Q-switched lasers are often compared.

 

A nanosecond laser breaks pigment using short pulses measured in nanoseconds.

 

A picosecond laser uses even shorter pulses measured in picoseconds, aiming to fragment pigment into smaller particles.

 

Picosecond lasers are often explained with an emphasis on the photomechanical effect, meaning mechanical shock.

 

Theoretically, this may help selectively break pigment particles into smaller fragments while reducing thermal damage to surrounding tissue.

 

However, the important point here is not that “pico is always better.”

 

Even with the same picosecond laser, the result can vary depending on wavelength, energy level, spot size,

irradiation method, skin type, and lesion thickness.

 

Ultimately, what matters more than the device name is how accurately the lesion is assessed, what energy setting is used, and what depth is targeted.

 

So what did the actual study show?

 

In a study by Kim et al., 20 patients with solar lentigines were treated with both a 532 nm picosecond Nd:YAG laser and a 532 nm Q-switched Nd:YAG laser.

This study was conducted using a split-face design.

 

Simply put, each patient’s face was divided into two sides. One side was treated with a 532 nm picosecond laser, while the other side was treated with a 532 nm Q-switched laser.

 

The study followed the patients after one treatment at 2, 4, 8, and 12 weeks.

 

Three dermatologists evaluated improvement using photographs and the QIS, or quartile improvement scale.

 

If you look at the before-and-after photos above, brown lentigines are visible on the cheekbone area before treatment, and the pigmentation appears lighter after treatment.

 

The study found that both lasers were effective for treating solar lentigines, but the 532 nm picosecond laser showed better results than the Q-switched Nd:YAG laser in terms of QIS, which evaluated the degree of clinical clearance.

 

There is another important point.

 

That is PIH.

 

PIH means post-inflammatory hyperpigmentation.

 

After solar lentigo removal, the original lentigo may become lighter, but a brown mark may remain or the area may look darker.

 

This kind of change may be related to PIH.

 

In this study, PIH occurred in 5% of areas treated with the 532 nm picosecond laser and in 30% of areas treated with the 532 nm Q-switched Nd:YAG laser.

 

This is very important in solar lentigo removal.

 

Reducing the lentigo itself is important, but reducing post-treatment pigmentation is just as important.

 

Especially in Asian skin, brown marks may remain for a long time if inflammation occurs after laser treatment.

 

That is why the key in solar lentigo treatment is not “burning strongly in one session,” but “accurately reducing the pigment while minimizing damage to the surrounding skin.”

After spot treatment for solar lentigines, the treated area may temporarily look darker or form a thin crust.

 

This can happen as the pigment lesion reacts to the laser and moves toward the surface.

 

Usually, the crust gradually falls off or the color becomes lighter over several days to one or two weeks.

 

However, the crust should not be picked off during this period.

 

If it is removed too early, skin that has not fully healed may be exposed, which can prolong redness or increase the risk of pigmentation.

 

UV protection after treatment is also important.

 

Solar lentigines are closely related to UV exposure from the beginning.

 

If the skin receives a lot of sunlight while it is still sensitive after treatment, the area may appear to recur or pigmentation may remain.

 

This is where treatment sequence becomes important.

 

For example, if a face has broad melasma and only the solar lentigines are treated aggressively with spots, the lentigines may become lighter, but the melasma may appear more noticeable.

 

On the other hand, if someone has many solar lentigines and receives only toning for a long time, the overall tone may become slightly more even, but the distinct brown spots may remain visible.

 

That is why, when I explain pigmentation treatment, I separate “toning” and “spot treatment.”

 

Broad pigmentation should be managed with toning to control the background tone.

 

Distinct solar lentigines should be reduced separately with spot treatment.

 

If redness or vascular reaction is present, vascular treatment may also need to be considered.

 

Pigmentation treatment is often not completed with just one laser. More often, we need to separate the lesions on the face and design the treatment sequence accordingly.

Before removing solar lentigines, visual diagnosis is important. When needed, imaging devices can also help evaluate pigment distribution.

 

Even if brown spots look similar on the surface, the treatment direction can change depending on whether the pigment is epidermal, whether melasma is mixed in, whether deeper pigment is present, or whether redness is also involved.

 

If you look at the photo above, the depth and shape of pigmentation can appear different even within the same face.

 

We need to identify these differences first to decide whether pico spot treatment is appropriate, whether toning should come first, or whether vascular treatment or barrier recovery should be considered together.

 

Solar lentigo removal is not a treatment that simply removes pigment aggressively.

 

It is a treatment that selects the right lesions accurately and reduces them carefully.

 

Reducing the pigment while minimizing surrounding skin damage and the risk of pigmentation afterward.

 

Finding that balance is one of the most important parts of pigmentation treatment in dermatology :)

 

This was Director Won Dae-han.

 

Thank you for reading.

 

Source:
Kim JY, Yang JH, Hur K, Choi YJ, Kim WS. A Split-Face, Single-Blinded, Randomized Controlled Comparison of 532 nm Picosecond Neodymium-Doped Yttrium Aluminum Garnet Laser versus 532 nm Q-Switched Neodymium-Doped Yttrium Aluminum Garnet Laser in the Treatment of Solar Lentigines. Annals of Dermatology. 2020;32(1):8-13. DOI: 10.5021/ad.2020.32.1.8.

 

※ This article is intended to provide general medical information. Actual suitability for solar lentigo removal, laser type, number of treatments, and treatment intervals may vary depending on pigment depth, lesion type, skin type, and whether melasma or redness is present. An accurate diagnosis and treatment plan should be determined through consultation.