This document summarizes light therapy and its use in wound healing. It discusses the four phases of normal wound healing and how diabetes can slow the process. The history of using light, including lasers and LEDs, to aid healing is presented. Studies show red light at 633nm and 10J/cm2 promoted healing in diabetic rats most effectively. Light stimulates angiogenesis through endothelial cell proliferation. Multiwavelength light therapy did not influence pressure ulcer healing. Low-level light therapy's mechanisms of action include stimulating mitochondria and having a biphasic dose response. While its effectiveness remains controversial, light therapy is a popular treatment with few risks.

1. LIGHT AND WOUND
HEALING
By:Amin Talebi (MSc)
Shiraz University of Medical Science; Medical
Physics Department

2. Outline
Why wound healing is important ?
Normal wound healing
History of the use of light in the wound healing
The optimum wavelength and incident dose
Mechanisms of action
Conclusion
References

3. Why wound healing is important ?
• Wound causes can be internal or external in origin
• Wounds of internal origin are mainly due to impaired circulation,
neuropathy or medical illness
• Wounds of external origin are due to an outside force or trauma that
causes open or closed wounds.

4. Why wound healing is important ?
• 382 million people have diabetes in 2013; by 2035 this will rise to 592
million
• Approximately 15 percent of diabetics will develop a foot ulcer at
some point. Foot ulcers are the most common wounds for this patient
population.
• According to statistics, diabetes is the number one reason for limb
amputation in the U.S.

5. Wound healing can be slowed when the patient
is diabetic
• Blood Glucose Levels
• Poor Circulation
• Diabetic Neuropathy
• Immune System Deficiency
• Infection

6. Normal wound healing
There are four phases of normal wound healing
I. Vascular Response (Hemostasis)
II. Inflammatory Response (Inflammation)
III. The Proliferative Phase (Granulation, Epithelialization)
IV.Maturation Phase (Reconstruction phase)

7. Vascular Response (Hemostasis)
• Vasoconstriction – within seconds, regardless of the source of injury,
blood vessels constrict to stop bleeding and reduce exposure to
bacteria
• Platelets cluster together at the site of injury to form a ‘clot’
• Wound healing begins within minutes after tissue damage

8. Inflammatory Response (Inflammation)
• This is the body’s early defense system against microbial invasion
• Neutrophils and Macrophages ingest injurious agents, thereby
protecting against bacterial invasion.
• Disorders that lead to reduced numbers of phagocytic cells slow the
inflammatory process and make the person more prone to infection

9. The Proliferative Phase (Granulation,
Epithelialization)
• Granulation occurs. Collagen, capillaries and cells begin to fill the
wound space with new connective tissue.
• Epithelialization occurs as epithelial cells migrate from surrounding
skin. This tissue is very fragile

10. Maturation Phase (Reconstruction phase)
• Remodeling of the scar continues for approximately 1 year
• Scar tissue regains about two thirds of its original strength
• Scar tissue is never as strong as the original tissue it replaces

11. Normal wound healing

12. History of the use of light in the wound healing
• light therapy is one of the oldest therapeutic methods used by humans
• historically as solar therapy by Egyptians, later as UV therapy for
which Nils Finsen won the Nobel prize in 1904
• The use of lasers and LEDs as light sources was the next step in the
technological development of light therapy, which is now applied to
many thousands of people worldwide each day

13. History of the use of light in the wound healing
• LASER is an acronym for Light Amplification by the Stimulated
Emission of Radiation.
• During the 1960s and 1970s, lasers were regarded as destructive .
• those lasers using photothermal and ablative properties are used
routinely to cut and destroy tissue. This is known as laser surgery.
• The therapeutic properties of relatively low intensity, athermic laser
irradiation were then recognised. This is referred to as laser therapy.

14. History of the use of light in the wound healing
• In 1967 Endre Mester in Semmelweis University, Budapest, Hungary
wanted to test if laser radiation might cause cancer in mice.
• He shaved the dorsal hair, divided them into two groups and gave a
laser treatment with a low powered ruby laser (694-nm) to one group.
• They did not get cancer
• The hair on the treated group grew back more quickly than the
untreated group

15. • The use of low levels of visible or near infrared light for reducing pain,
inflammation and edema, promoting healing of wounds, deeper
tissues and nerves has been known for almost forty years since the
invention of lasers.

16. LASER vs LED
• LASER light is:
coherent (all wavelengths are produced in phase)
monochromatic (of single colour or wavelength)
Collimated (produces a close parallel beam)

17. LASER vs LED
• LED light is:
• Noncoherent
• Polychromatic
• with broader line width

18. Schematic representation of the main areas of
application of LLLT

19. • Differences exist in the delivery of LLLT.
• Variables include laser type and wavelength, the use of a single
wavelength or a combination of wavelengths, irradiance or dosage,
beam divergence, spot size and duration of treatment

21. • The He-Ne laser was the first laser available and is reported to have
beneficial effects in both wound healing and dentistry.
• The He-Ne laser has the advantage that it emits red light, which is
visible and therefore the blink reflex protects the eye from it.

22. • The GaAs and GaAlAs laser have been most commonly used for the
treatment of pain and inflammation.
• These lasers have the disadvantage that their light is invisible and
therefore eye protection is required.

23. The optimum wavelength and incident dose

24. • The study was performed using 532,633,810, and 980 nm diode
lasers
• Incident doses of 5, 10, 20, and 30 J/cm2 .
• The wound healing on control rats with diabetes was slower than on
control rats without diabetes.
• LLLT at appropriate treatment parameters can enhance the wound
healing on diabetic rats

26. • Result showed that the optimum wavelength and incident dose was
633 nm and l0 J/cm .
• irradiation of visible laser light was better than invisible laser light in
the treatment of wound healing on diabetic rats.

27. • The reason for the effective acceleration of wound healing on diabetic
rats using low-power lasers was that perhaps the absorption of laser
light with specific wavelength by target tissue resulted in the
enhancement of fibroblast proliferation and the promotion of collagen
metabolism and granulation tissue formation in the diabetic wound

29. Laser and LED phototherapies on angiogenesis
• One very important phenomena involved on the formation of the
granulation tissue is angiogenesis.
• It is essential for the supply of oxygen and nutrients for the healing
wound allowing both cell proliferation and deposition of the collagen
matrix

30. • There are many studies on the use of laser light aiming to positively
stimulating the healing process, being the stimuli to angiogenesis one
of the most frequently reported.
• Previous studies have shown that, similar to laser light, the use of
LEDs presents an important effect on both angiogenesis and
vascularity.

32. Laser and LED phototherapies on angiogenesis
• There is an increase on angiogenesis on green LED (p<0.001), red
LED (p00.001), IR laser (p00.012) and red laser (p00.034) groups.
• No difference between the blue LED group and the control.
• The comparison among all illuminated groups showed a significant
increase on angiogenesis on green LED and red LED in relation to the
red laser group

33. Laser and LED phototherapies on angiogenesis
• the most evident effect on endothelial cells seen when doses of 1.05
or 2.1 J/cm2 were used.
• the effects of both light sources are dependent on both wavelength
and energy density rather than on the coherence.

34. Laser and LED phototherapies on angiogenesis
• in this study λ530+20 nm LED light group showed the most increased
angiogenesis.
• Result showed that not only red LEDs but also green LEDs can be a
new powerful therapeutic strategy for wound healing

35. Multiwavelength Light Therapy

36. • To study the efficacy of multiwavelength light therapy in the treatment
of pressure ulcers in subjects with spinal cord disorders.
• Thirty-five subjects with spinal cord injury, with 64 pressure ulcers
(stage 2, n=55; stage 3, n=8; stage 4, n=1), were randomized into
treatment and control groups.

37. • Treatment group received 14 sessions of multiwavelength light
therapy, with 46 probes of different wavelengths from a gallium-
aluminum-arsenide laser source, 3 times a week.
• Energy used was 4.5J/cm2.
• Ulcers in the control group received sham treatment.

38. Characteristics of Multiwavelength Light
Source
The central 820nm laser source was surrounded by 45 supraluminous
diodes of different wavelengths.

39. Results
• No significant difference in healing between the treatment and control
groups.
• Multiwavelength light therapy from a gallium- aluminum-arsenide laser
source did not influence overall healing pressure ulcers.

40. DNA damage after phototherapy

41. • This study aimed to determine the effects of phototherapy induced
DNA damage.
• human skin fibroblast cells.
• Irradiated twice once at 30 min and again at 72 h with 5 or 16 J/cm2.
• using a diode laser at 636 nm.

42. Results
• At both 1 and 24 h, wounded cells irradiated with 5 J/cm2 showed
insignificant DNA damage compared to control cells.
• irradiation with 16 J/cm2 showed significant damage.
• 24 h post-irradiation these cells showed a significant decrease in
damage compared to cells left to incubate for 1 h.

43. Mechanism of action of LLLT
• One theory regarding that the laser is capable of influencing
photoreceptors in the cells.
• This mechanism is referred to as photobiology or biostimulation.
• It has been reported that photobiostimulation occurs via the electron
transport chain enzymes in mitochondria,

44. Mechanism of action of LLLT
• The biostimulating effect of LLLT results in an increase in
microcirculation, higher production rates for ATP, RNA, and DNA
synthesis, thus improving cellular oxygenation, nutrition, and
regeneration and an enhanced mitochondrial electron transport
system.

49. Mechanism of action of LLLT
• The magnitude of the laser biostimulation effect depends on
the wavelength used
the physiological state of the cell at the moment of irradiation

50. Biphasic dose response of LLLT
• LLLT delivered at low doses may produce a better result when
compared to the same wavelength delivered at high doses.
• Weak stimuli slightly accelerate vital activity and stronger stimuli raise
it further
• but when a peak is reached, then stronger stimuli suppress it, until a
negative response is finally achieved.

51. Idealized biphasic dose response curve

52. Biphasic dose response
• The biphasic curve will be helpful to identify the sufficient energy level
that will be applied to get maximum biostimulation.
• If insufficient energy is applied then there will be no response
(because the minimum threshold has not been met).
• If more energy is applied, then a threshold is crossed and
biostimulation disappears and is replaced by bioinhibition instead

53. Conclusion
• Although the usefulness of phototherapy in wound healing is still
controversial, it has become a popular treatment modality in many
clinics.
• As this therapy has few contraindications and no reported side effects,
it could be considered as a potentially useful treatment option if shown
to be effective

54. Conclusion
• There appear to be many anecdotal claims that phototherapy
stimulates wound healing but the question arises as to whether
sufficient scientific evidence exists to justify its routine use in wound
care.

55. References
• MARIUSZ CHYCZEWSKI, PIOTR HOLAK , MAREK JAŁYŃSKI , ALEKSANDER
KASPROWICZ , TADEUSZ ROTKIEWICZ1, AND ANNA MIKOŁAJCZYK1. EFFECT OF LASER
BIOSTIMULATION ON THE HEALING OF CUTANEOUS SURGICAL WOUNDS IN PIGS.
FAROUKA.H. AL-WAIBAN, M.Sc., Ph.D, XING YANG ZHANG, M.D., and
BERNARD L. ANDRES. MT(AMT). Low-Level LaserT herapyE nhancesW oundH ealingi n
DiabeticR ats:A Comparisono f Different Lasers. Photomedicine and Laser Surgery
Volume 25, Number 2,2007
Michael R Hamblin a,b,c,* and Tatiana N Demidova. Mechanisms of Low Level Light Therapy.
Adel J. Hussein1, Abdalbari A. Alfars2, Mohsin A. J. Falih2, Al-Nawar A. Hassan2. Effects of a low level laser
on the acceleration of wound healing in rabbits. North American Journal of Medical Sciences 2011 April,
Volume 3. No. 4.

56. Thanks for your attention