How Does The Pass Technique Impact Pain And Lesion Reduction In 1450 Nm Diode Laser Acne Treatment?

The double-pass, lower-fluence technique substantially improves comfort. In the cited comparison, a high-energy single pass at 12–14 J/cm² produced about a 78% reduction in acne lesions, but average pain was 5.6/10. A lower-energy double pass at approximately 8 J/cm² per pass reduced pain to 1.3/10 while still achieving about a 67% lesion reduction.

The trade-off is clear: double-pass delivery sacrifices roughly 11 percentage points of lesion reduction in exchange for a major reduction in patient discomfort. For many patients, this comfort advantage may improve treatment acceptance and completion without eliminating meaningful clinical benefit.

What the Pass Technique Changes

High-energy single pass maximizes lesion reduction

A single pass using 12–14 J/cm² concentrates substantial thermal energy into one delivery. In the referenced results, this approach achieved approximately 78% lesion reduction, making it the stronger option for maximizing numerical clearance.

The disadvantage is a relatively high average pain rating of 5.6 on a 10-point scale. The intense thermal sensation can limit tolerance, particularly when treating widespread or deeply inflamed acne.

Lower-energy double pass prioritizes comfort

The double-pass approach uses a lower fluence—approximately 8 J/cm² per pass—rather than delivering the treatment in one high-energy exposure. The reported average pain rating fell to 1.3/10, representing a substantial improvement in comfort.

Clinical efficacy remained meaningful, with approximately 67% lesion reduction. This is lower than the 78% reported with high-energy single pass, but it still represents a robust response for inflammatory acne.

Why the 1450 nm Laser Can Affect Acne

Thermal targeting of sebaceous glands

The 1450 nm wavelength penetrates into the dermis and is absorbed by water-containing tissue. This allows controlled heating near the sebaceous glands, where thermal injury can reduce gland activity and sebum production.

Because excess sebum supports inflammatory acne biology, reducing sebaceous activity can decrease active lesion formation over a course of treatment.

Cooling protects the epidermis

Dynamic epidermal cooling helps limit heat accumulation at the skin surface while allowing therapeutic energy to reach deeper tissue. This is particularly important because the treatment’s clinical effect depends on creating sufficient dermal thermal injury without causing unnecessary epidermal damage.

Cooling can improve tolerance, but it does not eliminate the need for appropriate fluence selection, skin assessment, and monitoring.

Comparing the Clinical Outcomes

Pain difference

Protocol	Approximate pain rating	Interpretation
Single pass, 12–14 J/cm²	5.6/10	Moderate-to-high discomfort
Double pass, approximately 8 J/cm² per pass	1.3/10	Low discomfort

The difference is approximately 4.3 points on a 10-point scale, which is clinically meaningful for patient experience and willingness to undergo repeated sessions.

Lesion-reduction difference

Protocol	Approximate lesion reduction	Interpretation
Single pass, 12–14 J/cm²	78%	Greater reported clearance
Double pass, approximately 8 J/cm² per pass	67%	Slightly lower, but still substantial

The double-pass protocol produced about 11 percentage points less lesion reduction in the cited comparison. These figures should not be treated as universal outcomes because results depend on patient selection, treatment schedule, cooling, acne severity, and assessment timing.

Understanding the Trade-offs

Comfort versus maximum clearance

The high-energy single pass is appropriate when the primary objective is the greatest possible lesion reduction and the patient can tolerate the thermal sensation. However, greater efficacy per treatment is less useful if discomfort causes missed appointments or refusal of future sessions.

The lower-energy double pass offers a more tolerable treatment experience. Its approximately 67% lesion reduction suggests that practitioners can improve comfort without abandoning meaningful clinical efficacy.

Fluence cannot be evaluated in isolation

An 8 J/cm² double pass should not automatically be considered equivalent to a single 16 J/cm² exposure. Tissue response depends on pulse structure, interval between passes, spot size, cooling, repetition rate, treatment technique, and the characteristics of the specific laser platform.

Therefore, the reported comparison supports a clinical strategy, not a universal conversion formula.

Patient variability matters

Pain ratings are averages, not guarantees. Patients with darker skin phototypes, highly inflamed lesions, sensitive skin, or prior treatment-related anxiety may experience different levels of discomfort and may require individualized parameter selection.

Transient erythema, edema, itching, and occasional post-inflammatory hyperpigmentation remain possible, even when a lower-energy protocol is used.

How to Apply This to Clinical Planning

Use patient tolerance as a treatment variable

The best protocol is not necessarily the one with the highest lesion-reduction percentage. It is the one that delivers adequate clinical improvement while allowing the patient to complete the planned treatment course.

Dynamic cooling, appropriate counseling, and—when clinically suitable—topical anesthesia can further support tolerability, particularly with higher-fluence treatment.

Interpret outcomes over the full treatment course

The cited figures compare approximate lesion reduction, but acne treatment commonly involves multiple sessions spaced weeks apart. A lower-energy protocol may be especially practical when repeated treatments are anticipated and comfort is important for adherence.

Outcome assessment should use consistent lesion-count methods and comparable follow-up intervals.

Choosing the Right Protocol for the Goal

If your primary focus is maximum lesion reduction per treatment: A high-energy single pass at approximately 12–14 J/cm² produced the greater reported reduction—about 78%—but requires careful pain management and monitoring.
If your primary focus is patient comfort and treatment compliance: A lower-energy double pass at approximately 8 J/cm² per pass reduced average pain to 1.3/10 while maintaining about 67% lesion reduction.
If your primary focus is treating patients who are unlikely to tolerate high heat: Consider a lower-energy, multi-pass strategy with appropriate epidermal cooling and individualized parameter adjustment.
If your primary focus is protocol consistency: Use validated settings for the specific 1450 nm platform rather than assuming that fluence values or pass techniques are interchangeable across devices.

The lower-energy double-pass approach is a practical comfort-first strategy that preserves substantial acne improvement while accepting a modest reduction in reported lesion clearance.

Summary Table:

Protocol	Pain Rating (avg)	Lesion Reduction
Single pass, 12–14 J/cm²	5.6/10	78%
Double pass, ~8 J/cm² per pass	1.3/10	67%

As a leading supplier of professional-grade aesthetic lasers, BELIS can help you choose the optimal 1450 nm diode laser system for your clinic or salon. Our advanced devices feature dynamic cooling and customizable pass parameters to balance efficacy and comfort, ensuring high patient satisfaction. Contact us today to learn more about our dermatological laser solutions and how they can enhance your acne treatment outcomes. Get in touch with BELIS.