Skin Research and Technology 2015; 21: 41–46 Printed in Singapore All rights reserved doi: 10.1111/srt.12154
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Skin Research and Technology
Dermal matrix affects translucency of incident light on the skin H. J. Kim1,*, J. H. Baek1,*, J. E. Eo1, K. M. Choi1, M. K. Shin2 and J. S. Koh1 1
Skin Research Center, DERMAPRO LTD., Seoul, Korea and 2Department of Dermatology, School of medicine, Kyung Hee University, Seoul, Korea
Background/aims: The age-dependent changes in the optical reflection characteristics have been studied about skin hydration, melanin index, or skin color. However, the age-dependent changes in the optical reflection have little attention on inner skin structures. To control the factors affecting the optical reflection except for dermal matrix, subjects were selected as our guideline and we evaluated the optical reflection of subsurface on skin layers of two age groups. Method: Young and old healthy volunteers were recruited after signing a written informed consent form. Facial skin was measured by means of noninvasive measurements: skin hydration, color, epidermis and dermis thickness, dermal density, subsurface reflectance, and transmittance.
Result: Compared to young group, old group showed that dermal density and thickness was decreased significantly although epidermis thickness was not changed. Conclusion: In conclusion, dermal density is one of the major factors which affects the subsurface reflectance in skin.
of the skin such as gloss, shine, radiance, and translucency is the result of complicated light-skin interactions involving surface and subsurface reflections. Among them, skin radiance is a psychophysical parameter that involves quite complicated surface and internal qualities of the skin (1). In comparison with skin features, optical attributes of the skin such as radiance and translucency have not been well defined. The optical attributes of the skin are affected by skin hydration, skin color (melanin and hemoglobin distribution), and inner skin structures. When the skin is hydrated, surface scattering decreases, there is less back scattering and more transmission. Therefore, the decrease in skin surface scattering increases light penetration into the deeper skin layers, resulting in an increase in skin transparency (2). Other factors affecting optical attributes of the skin are skin color and inner skin structures. It is well known that melanin and hemoglobin absorb the light and affect subsurface reflection as absorbing the light.
Moreover, inner skin structures such as collagen and elastin fiber increase the light scattering. Various studies have been performed on these parameters in the fields of cosmetics. However, the relationship between the dermal matrix and subsurface reflection has not been established. The aim of this study was to evaluate the correlation only between the subsurface reflection and inner skin structures using contact and contactless translucency devices.
T
HE APPEARANCE
*H. J. Kim and J. H. Baek contributed equally to this work.
Key words: dermal matrix – translucency – radiance – subsurface reflection
Ó 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Accepted for publication 8 March 2014
Materials and Methods Human subjects The study included clinically healthy female subjects aged between 20 and 58 years. Several inclusion and exclusion criteria were used for the selection of the subjects. Each subject provided written informed consent to participate to the study. The subjects were divided two groups: group A (20 subjects, 20–28 years), group B (22 subjects, 50–58 years). We had enrolled the volunteers as to our guideline which is composed of skin hydration, skin color (L* value) limitation to evaluate the radiance only by inner skin structures. The L* value was
41
Kim et al.
around 62–65 and skin hydration was around 51–67.
Measurement of skin hydration The skin hydration level was measured using the Corneometerâ CM 825 (Courage & Khazaka Electronic GmbH, Cologne, Germany). The measurements were performed in the same controlled room.
Skin color evaluation The skin color was determined using the Minolta Spectrophotometer CM-2600d (Minolta Co. Ltd., Osaka, Japan). Color was expressed using the CIE 1976 (L*a*b*) system, where L = luminance, a = red/green reflectance, and b = yellow/blue reflectance. To evaluate melanin, the melanin index was measured by a Mexameter (Mexameter, MX 18, Courage-Khazaka, Cologne, Germany), where 16 light-emitting diodes were arranged in a circular manner.
cheek using TLS850 (Diastron Ltd, Andover, Hampshire, UK) and Radioscan (Trusystem, Seongnam, Korea). Radioscan is a contactless translucency device of which light source is not direct contact with the skin. So it can measure both surface and subsurface reflections. However, TLS 850 is a contact translucency device of which light source is direct contract with the skin. So it can measure only subsurface reflections. Contactless measurement mechanism of translucency is described in Fig. 2. Contact measurement mechanism of translucency is described in Eq. (1) and Fig. 1. The method to calculate amount of surface/ subsurface scattering reflective light (3) is given in Eq. (1): Surface reflection ¼ light intensity of parallel polarized light intensity of cross polarized Subsurface reflection ¼ light intensity of cross polarized 2
Measurement of epidermis thickness The epidermal thickness was measured by the mean thickness of two part of epidermis, the one is dermal papillary tip, and the other is dermal papillary bottom (Fig 2). And 4-mm area of the left cheek in dermis layer was imaged by means of RCM (Reflectance Confocal Microscopy, Lucid, Rochester, NY, USA). The field of view measured 500 9 500 lm2 with a resolution of 1000 9 1000 pixels and corresponded to a horizontal section at a selected tissue depth.
The translucency value is composed of three parameters as follows:
• The K value represents the amount of light detected by the probe as close to the light source as possible. • The ALPHA value represents the rate of attenuation of the light level moving away from the source. A high ALPHA represents a rapid attenuation of light intensity.
Light source
Signal profile
Ultrasonographic evaluation for dermal thickness and density The ultrasonographic assessment of the integument was performed with a 20 MHz high-frequency Dermascan C device (Cortex Technology, Hadsund, Denmark), that allows the ‘in vivo’ acquirement of cross-sectional images of the skin (B mode) up to 2.5 cm in depth.
Translucent material
Optical measurement of subsurface reflection For the study of the optical properties of the skin, subsurface reflection was acquired at
Fig. 1. The diagram of translucency value on the skin. The translucent materials scatter the light within the material, a proportion of this scattered light being returned to the probe. Using a fiber optic faceplate (FOP), the probe collects the backscattered light.
42
Photodiode array
Fibre optic faceplate
Dermal matrix affects translucency (a) 70
Skin hydration (A.U)
60 50 40 30 20 10 0 Young
Old
(b) 160 140 120 Melanin index
Fig. 2. Orientation of polarization of surface and subsurface reflection from the skin. Subsurface reflections contain polarized light of random orientation that can be decomposed into vectors parallel and perpendicular to that of the incident light. The device (Radioscan) collects the amount of back scattering light from sub-surface skin layer (5).
100 80 60 40
• The AREA value represents the total amount
20 0
of light scattered into the material.
Young
Old
(c) 70 60 50 L* value
Statistics Statistical evaluation was carried out employing the SPSS statistical package (release 21, SPSS Inc., Chicago, IL, USA). We employed the student ttest when testing for significant differences between the two groups.
40 30 20 10
Results
0 Young
Skin hydration, L value, and the melanin indices The homogeneity of three parameters was described at Table 1. They were not significantly different between two groups (Fig. 3). Skin hydration, melanin, and skin color affect the subsurface reflections. Especially, skin hydration decreases the surface scattering, resulting in the increase in light into dermis layer. Skin color (L* value, melanin index) also affects the incident light in the skin by absorbing it. TABLE 1. Volunteer selection (n = 42) Item
Young group Mean SD
Old group Mean SD
t
P-value*
Skin hydration L* value Melanin index
61.1 6.01 63.81 1.06 134.60 27.31
61.09 5.92 63.08 1.56 127.41 17.81
0.005 1.773 1.020
0.996 0.084 0.314
*
Comparison between groups.
Old
Fig. 3. Changes of skin hydration (a), L* value (b) and melanin index (c) by age group.
Epidermis thickness In young group, the mean epidermal thickness was 46.63 7.53 lm, old one was 45.68 7.16 lm. There were no significant differences between two groups (Table 2, Fig. 6). We evaluated the epidermis thickness as the middle thickness of dermal papillary tip and dermal papillary bottom.
Dermal thickness and density In young group, the dermal thickness was 1.82 0.14 mm, the old one was 1.75 0.19 mm. Dermal density of young group was higher than the old one. Dermal density decreased significantly and dermal thickness tends to decrease in old group (Table 2; Fig. 4).
43
Kim et al. TABLE 2. Results of skin characteristics on young and old groups (n = 42) Translucency value Group Young Old P-value*
Skin hydration 61.10 6.01 61.09 5.93 0.996
L* value
Melanin index
Epidermal Thickness (um)
Dermal density
Dermal thickness (mm)
Alpha
K
Area
Subsurface reflection
63.81 1.06 63.08 1.57 0.084
134.60 27.31 127.41 17.81 0.314
46.63 7.53 45.68 7.16 0.680
15.44 2.29 13.06 2.31 0.002*
1.82 0.14 1.75 0.19 0.236
0.0232 0.0012 0.0217 0.0010 0.000*
1313.75 155.72 1235.89 117.89 0.088
57309.55 6529.63 57725.95 6680.78 0.845
25.15 2.75 23.36 2.62 0.037*
*Comparison between groups.
(a)
(b)
Fig. 4. Dermal matrix of young group (a) and old group (b) by ultrasonography.
Therefore, the incident light is affected less by inner skin structures such as collagen and elastin fiber.
Dermal matrix architecture As shown in Fig. 5, the presence of thin fibers arranged in a reticular pattern characterized younger subjects and progressively increased the coarse and huddled collagen in older subjects.
Translucency value The subsurface reflection intensity decreased significantly in old group. The mean value in young group was 25.15 2.75 and the old one was 23.36 2.62. The translucency value in younger group was 0.0232 0.0012 and the old one was 0.0217 0.0012 (Table 2; Fig. 6). The alpha and K value were lower for older group. If dermis layer is compact and well-organized, the K value is high. The ALPHA value represents the rate of attenuation of the light level moving away from the source. If skin is more transparent, the light travels deeper and longer in the skin structure.
44
Discussion Skin radiance has been used as general cosmetic term for skin brightness, purity, and emission of light from the skin. Among these, skin brightness can be usually expressed by L value of L* a* b* (CIELAB color space system). Zhi-xing Jiang et al. defined skin translucency as the light scattering beneath skin surface (4). Incident light is divided into two parts, surface and subsurface reflection. The melanin and hemoglobin absorb the incident light affecting the surface and subsurface reflection. Skin hydration is related to the hydration of the stratum corneum, and is also known to be an important attribute of healthy skin. Moisturized skin is more transparent as light passes into the skin. The decrease in skin surface scattering increases light penetration into the deeper skin layers, resulting in an increase in skin translucency. The purpose of this study was to measure the relationship between translucency and the dermal matrix, other factors that affect skin translucency are excluded. Skin hydration, L value, and melanin index were controlled both groups. There were not significant differences in skin
Dermal matrix affects translucency (a)
(b)
Fig. 5. Dermal matrix of young group (a) and old group (b) by reflectance confocal microscopy.
*
(a)
(b)
(c) 49
1.9
18
14 12 10 8 6 4
Epidermis thickness (µm)
Dermis thickness (mm)
Dermal density (A.U)
48
1.85
16
1.8 1.75 1.7 1.65 1.6
Young
(d)
45 44 43
41
Old
*
0.0240
46
42
2 0
47
Young
Old
Young
Old
*
(e) 26 25.5 Subsurface reflection value
0.0235 Translucency value
0.0230 0.0225 0.0220 0.0215 0.0210 0.0205
25 24.5 24 23.5 23 22.5 22 21.5
0.0200
21 Young
Old
Young
Old
Fig. 6. Changes of dermal density (a), dermis thickness (b), epidermis thickness(c), translucency value (d) and subsurface reflection value (e) by age group (Mean SE, *P < 0.05).
hydration, L value, or melanin index between the two groups. Furthermore, the epidermal thickness exhibited no significant differences. However, dermal density, thickness, translucency value, and subsurface reflection value did show significant differences between two groups. K and Alpha parameter of translucency
value are lower in the old group due to dermal matrix being more loose resulting the light travel deeper into the skin structure. This means that dermal matrix is not compact and less organized. In old group, the dermal matrix affects less light sub-surface reflection or scattering. Therefore, the incident light passes
45
Kim et al.
through the dermis easily, giving the skin a more transparent aspect. Also, the dermis thickness in the younger group was thicker than that in the old group. However, there was no difference in terms of epidermis thickness. The epidermis also contains densely packed keratin fibers which could act as strong scatterers. And the epidermal layer acts as a strong absorber due to the high density of melanin pigment and therefore the incident light energy will be reduced through absorption (3). However, their contribution can be considered as negligible since the epidermis is very thin. In this study, the melanin index and L* value of each subject were controlled in both groups.
References 1. Petitjean A, Sainthillier JM, Mac-Mary S, Muret P, Closs B, Gharbi T, Humbert P. Skin radiance: how to quantify? Validation of an optical method. Skin Res Technol 2007; 13: 2–8. 2. Jiang Z-X, De La Cruz J. Appearance benefits of skin moisturization. Skin Res Technol 2008; 14: 293–297. 3. Matsubara A. Differences in the surface and subsurface reflection characteristics of facial skin by age
46
And no significant differences were observed in these factors. Thus, the epidermis was not taken into consideration as factors affecting the incident light sub-surface reflection or scattering. Figure 4 depicts the dermal matrix of the young and old group. Concerning the dermis, a thin reticulated structure, and well-organized filaments of collagen fibers were observed in young subjects. Thus, subsurface reflection value is high in younger subjects. The dermal matrix in young subjects comprises many scattering factors such as collagen and elastin fiber. In conclusion, dermal density is a major factor that affects the subsurface reflectance in skin.
group. Skin Res Technol 2012; 18: 29–35. 4. Matsubara A, Liang Z, Sato Y, Uchikawa K. Analysis of human perception of facial skin radiance by means of image histogram parameters of surface and subsurface reflections from the skin. Skin Res Technol 2012; 18: 265–271. 5. Jiang ZX, Kaplan PD. Point-spread imaging for measurement of skin translucency and scattering. Skin Res Technol 2008; 14: 293–297.
Address: J. S. Koh DERMAPRO LTD Skin Research Center 4F Jiho B/D Bangbaejoongang-Ro 30 Seocho-Gu Seoul 137-843 Korea Tel: +82 2 597 5434 Fax: +82 2 597 5430 e-mail: [email protected]
Copyright of Skin Research & Technology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Skin Research and Technology
Dermal matrix affects translucency of incident light on the skin H. J. Kim1,*, J. H. Baek1,*, J. E. Eo1, K. M. Choi1, M. K. Shin2 and J. S. Koh1 1
Skin Research Center, DERMAPRO LTD., Seoul, Korea and 2Department of Dermatology, School of medicine, Kyung Hee University, Seoul, Korea
Background/aims: The age-dependent changes in the optical reflection characteristics have been studied about skin hydration, melanin index, or skin color. However, the age-dependent changes in the optical reflection have little attention on inner skin structures. To control the factors affecting the optical reflection except for dermal matrix, subjects were selected as our guideline and we evaluated the optical reflection of subsurface on skin layers of two age groups. Method: Young and old healthy volunteers were recruited after signing a written informed consent form. Facial skin was measured by means of noninvasive measurements: skin hydration, color, epidermis and dermis thickness, dermal density, subsurface reflectance, and transmittance.
Result: Compared to young group, old group showed that dermal density and thickness was decreased significantly although epidermis thickness was not changed. Conclusion: In conclusion, dermal density is one of the major factors which affects the subsurface reflectance in skin.
of the skin such as gloss, shine, radiance, and translucency is the result of complicated light-skin interactions involving surface and subsurface reflections. Among them, skin radiance is a psychophysical parameter that involves quite complicated surface and internal qualities of the skin (1). In comparison with skin features, optical attributes of the skin such as radiance and translucency have not been well defined. The optical attributes of the skin are affected by skin hydration, skin color (melanin and hemoglobin distribution), and inner skin structures. When the skin is hydrated, surface scattering decreases, there is less back scattering and more transmission. Therefore, the decrease in skin surface scattering increases light penetration into the deeper skin layers, resulting in an increase in skin transparency (2). Other factors affecting optical attributes of the skin are skin color and inner skin structures. It is well known that melanin and hemoglobin absorb the light and affect subsurface reflection as absorbing the light.
Moreover, inner skin structures such as collagen and elastin fiber increase the light scattering. Various studies have been performed on these parameters in the fields of cosmetics. However, the relationship between the dermal matrix and subsurface reflection has not been established. The aim of this study was to evaluate the correlation only between the subsurface reflection and inner skin structures using contact and contactless translucency devices.
T
HE APPEARANCE
*H. J. Kim and J. H. Baek contributed equally to this work.
Key words: dermal matrix – translucency – radiance – subsurface reflection
Ó 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd Accepted for publication 8 March 2014
Materials and Methods Human subjects The study included clinically healthy female subjects aged between 20 and 58 years. Several inclusion and exclusion criteria were used for the selection of the subjects. Each subject provided written informed consent to participate to the study. The subjects were divided two groups: group A (20 subjects, 20–28 years), group B (22 subjects, 50–58 years). We had enrolled the volunteers as to our guideline which is composed of skin hydration, skin color (L* value) limitation to evaluate the radiance only by inner skin structures. The L* value was
41
Kim et al.
around 62–65 and skin hydration was around 51–67.
Measurement of skin hydration The skin hydration level was measured using the Corneometerâ CM 825 (Courage & Khazaka Electronic GmbH, Cologne, Germany). The measurements were performed in the same controlled room.
Skin color evaluation The skin color was determined using the Minolta Spectrophotometer CM-2600d (Minolta Co. Ltd., Osaka, Japan). Color was expressed using the CIE 1976 (L*a*b*) system, where L = luminance, a = red/green reflectance, and b = yellow/blue reflectance. To evaluate melanin, the melanin index was measured by a Mexameter (Mexameter, MX 18, Courage-Khazaka, Cologne, Germany), where 16 light-emitting diodes were arranged in a circular manner.
cheek using TLS850 (Diastron Ltd, Andover, Hampshire, UK) and Radioscan (Trusystem, Seongnam, Korea). Radioscan is a contactless translucency device of which light source is not direct contact with the skin. So it can measure both surface and subsurface reflections. However, TLS 850 is a contact translucency device of which light source is direct contract with the skin. So it can measure only subsurface reflections. Contactless measurement mechanism of translucency is described in Fig. 2. Contact measurement mechanism of translucency is described in Eq. (1) and Fig. 1. The method to calculate amount of surface/ subsurface scattering reflective light (3) is given in Eq. (1): Surface reflection ¼ light intensity of parallel polarized light intensity of cross polarized Subsurface reflection ¼ light intensity of cross polarized 2
Measurement of epidermis thickness The epidermal thickness was measured by the mean thickness of two part of epidermis, the one is dermal papillary tip, and the other is dermal papillary bottom (Fig 2). And 4-mm area of the left cheek in dermis layer was imaged by means of RCM (Reflectance Confocal Microscopy, Lucid, Rochester, NY, USA). The field of view measured 500 9 500 lm2 with a resolution of 1000 9 1000 pixels and corresponded to a horizontal section at a selected tissue depth.
The translucency value is composed of three parameters as follows:
• The K value represents the amount of light detected by the probe as close to the light source as possible. • The ALPHA value represents the rate of attenuation of the light level moving away from the source. A high ALPHA represents a rapid attenuation of light intensity.
Light source
Signal profile
Ultrasonographic evaluation for dermal thickness and density The ultrasonographic assessment of the integument was performed with a 20 MHz high-frequency Dermascan C device (Cortex Technology, Hadsund, Denmark), that allows the ‘in vivo’ acquirement of cross-sectional images of the skin (B mode) up to 2.5 cm in depth.
Translucent material
Optical measurement of subsurface reflection For the study of the optical properties of the skin, subsurface reflection was acquired at
Fig. 1. The diagram of translucency value on the skin. The translucent materials scatter the light within the material, a proportion of this scattered light being returned to the probe. Using a fiber optic faceplate (FOP), the probe collects the backscattered light.
42
Photodiode array
Fibre optic faceplate
Dermal matrix affects translucency (a) 70
Skin hydration (A.U)
60 50 40 30 20 10 0 Young
Old
(b) 160 140 120 Melanin index
Fig. 2. Orientation of polarization of surface and subsurface reflection from the skin. Subsurface reflections contain polarized light of random orientation that can be decomposed into vectors parallel and perpendicular to that of the incident light. The device (Radioscan) collects the amount of back scattering light from sub-surface skin layer (5).
100 80 60 40
• The AREA value represents the total amount
20 0
of light scattered into the material.
Young
Old
(c) 70 60 50 L* value
Statistics Statistical evaluation was carried out employing the SPSS statistical package (release 21, SPSS Inc., Chicago, IL, USA). We employed the student ttest when testing for significant differences between the two groups.
40 30 20 10
Results
0 Young
Skin hydration, L value, and the melanin indices The homogeneity of three parameters was described at Table 1. They were not significantly different between two groups (Fig. 3). Skin hydration, melanin, and skin color affect the subsurface reflections. Especially, skin hydration decreases the surface scattering, resulting in the increase in light into dermis layer. Skin color (L* value, melanin index) also affects the incident light in the skin by absorbing it. TABLE 1. Volunteer selection (n = 42) Item
Young group Mean SD
Old group Mean SD
t
P-value*
Skin hydration L* value Melanin index
61.1 6.01 63.81 1.06 134.60 27.31
61.09 5.92 63.08 1.56 127.41 17.81
0.005 1.773 1.020
0.996 0.084 0.314
*
Comparison between groups.
Old
Fig. 3. Changes of skin hydration (a), L* value (b) and melanin index (c) by age group.
Epidermis thickness In young group, the mean epidermal thickness was 46.63 7.53 lm, old one was 45.68 7.16 lm. There were no significant differences between two groups (Table 2, Fig. 6). We evaluated the epidermis thickness as the middle thickness of dermal papillary tip and dermal papillary bottom.
Dermal thickness and density In young group, the dermal thickness was 1.82 0.14 mm, the old one was 1.75 0.19 mm. Dermal density of young group was higher than the old one. Dermal density decreased significantly and dermal thickness tends to decrease in old group (Table 2; Fig. 4).
43
Kim et al. TABLE 2. Results of skin characteristics on young and old groups (n = 42) Translucency value Group Young Old P-value*
Skin hydration 61.10 6.01 61.09 5.93 0.996
L* value
Melanin index
Epidermal Thickness (um)
Dermal density
Dermal thickness (mm)
Alpha
K
Area
Subsurface reflection
63.81 1.06 63.08 1.57 0.084
134.60 27.31 127.41 17.81 0.314
46.63 7.53 45.68 7.16 0.680
15.44 2.29 13.06 2.31 0.002*
1.82 0.14 1.75 0.19 0.236
0.0232 0.0012 0.0217 0.0010 0.000*
1313.75 155.72 1235.89 117.89 0.088
57309.55 6529.63 57725.95 6680.78 0.845
25.15 2.75 23.36 2.62 0.037*
*Comparison between groups.
(a)
(b)
Fig. 4. Dermal matrix of young group (a) and old group (b) by ultrasonography.
Therefore, the incident light is affected less by inner skin structures such as collagen and elastin fiber.
Dermal matrix architecture As shown in Fig. 5, the presence of thin fibers arranged in a reticular pattern characterized younger subjects and progressively increased the coarse and huddled collagen in older subjects.
Translucency value The subsurface reflection intensity decreased significantly in old group. The mean value in young group was 25.15 2.75 and the old one was 23.36 2.62. The translucency value in younger group was 0.0232 0.0012 and the old one was 0.0217 0.0012 (Table 2; Fig. 6). The alpha and K value were lower for older group. If dermis layer is compact and well-organized, the K value is high. The ALPHA value represents the rate of attenuation of the light level moving away from the source. If skin is more transparent, the light travels deeper and longer in the skin structure.
44
Discussion Skin radiance has been used as general cosmetic term for skin brightness, purity, and emission of light from the skin. Among these, skin brightness can be usually expressed by L value of L* a* b* (CIELAB color space system). Zhi-xing Jiang et al. defined skin translucency as the light scattering beneath skin surface (4). Incident light is divided into two parts, surface and subsurface reflection. The melanin and hemoglobin absorb the incident light affecting the surface and subsurface reflection. Skin hydration is related to the hydration of the stratum corneum, and is also known to be an important attribute of healthy skin. Moisturized skin is more transparent as light passes into the skin. The decrease in skin surface scattering increases light penetration into the deeper skin layers, resulting in an increase in skin translucency. The purpose of this study was to measure the relationship between translucency and the dermal matrix, other factors that affect skin translucency are excluded. Skin hydration, L value, and melanin index were controlled both groups. There were not significant differences in skin
Dermal matrix affects translucency (a)
(b)
Fig. 5. Dermal matrix of young group (a) and old group (b) by reflectance confocal microscopy.
*
(a)
(b)
(c) 49
1.9
18
14 12 10 8 6 4
Epidermis thickness (µm)
Dermis thickness (mm)
Dermal density (A.U)
48
1.85
16
1.8 1.75 1.7 1.65 1.6
Young
(d)
45 44 43
41
Old
*
0.0240
46
42
2 0
47
Young
Old
Young
Old
*
(e) 26 25.5 Subsurface reflection value
0.0235 Translucency value
0.0230 0.0225 0.0220 0.0215 0.0210 0.0205
25 24.5 24 23.5 23 22.5 22 21.5
0.0200
21 Young
Old
Young
Old
Fig. 6. Changes of dermal density (a), dermis thickness (b), epidermis thickness(c), translucency value (d) and subsurface reflection value (e) by age group (Mean SE, *P < 0.05).
hydration, L value, or melanin index between the two groups. Furthermore, the epidermal thickness exhibited no significant differences. However, dermal density, thickness, translucency value, and subsurface reflection value did show significant differences between two groups. K and Alpha parameter of translucency
value are lower in the old group due to dermal matrix being more loose resulting the light travel deeper into the skin structure. This means that dermal matrix is not compact and less organized. In old group, the dermal matrix affects less light sub-surface reflection or scattering. Therefore, the incident light passes
45
Kim et al.
through the dermis easily, giving the skin a more transparent aspect. Also, the dermis thickness in the younger group was thicker than that in the old group. However, there was no difference in terms of epidermis thickness. The epidermis also contains densely packed keratin fibers which could act as strong scatterers. And the epidermal layer acts as a strong absorber due to the high density of melanin pigment and therefore the incident light energy will be reduced through absorption (3). However, their contribution can be considered as negligible since the epidermis is very thin. In this study, the melanin index and L* value of each subject were controlled in both groups.
References 1. Petitjean A, Sainthillier JM, Mac-Mary S, Muret P, Closs B, Gharbi T, Humbert P. Skin radiance: how to quantify? Validation of an optical method. Skin Res Technol 2007; 13: 2–8. 2. Jiang Z-X, De La Cruz J. Appearance benefits of skin moisturization. Skin Res Technol 2008; 14: 293–297. 3. Matsubara A. Differences in the surface and subsurface reflection characteristics of facial skin by age
46
And no significant differences were observed in these factors. Thus, the epidermis was not taken into consideration as factors affecting the incident light sub-surface reflection or scattering. Figure 4 depicts the dermal matrix of the young and old group. Concerning the dermis, a thin reticulated structure, and well-organized filaments of collagen fibers were observed in young subjects. Thus, subsurface reflection value is high in younger subjects. The dermal matrix in young subjects comprises many scattering factors such as collagen and elastin fiber. In conclusion, dermal density is a major factor that affects the subsurface reflectance in skin.
group. Skin Res Technol 2012; 18: 29–35. 4. Matsubara A, Liang Z, Sato Y, Uchikawa K. Analysis of human perception of facial skin radiance by means of image histogram parameters of surface and subsurface reflections from the skin. Skin Res Technol 2012; 18: 265–271. 5. Jiang ZX, Kaplan PD. Point-spread imaging for measurement of skin translucency and scattering. Skin Res Technol 2008; 14: 293–297.
Address: J. S. Koh DERMAPRO LTD Skin Research Center 4F Jiho B/D Bangbaejoongang-Ro 30 Seocho-Gu Seoul 137-843 Korea Tel: +82 2 597 5434 Fax: +82 2 597 5430 e-mail: [email protected]
Copyright of Skin Research & Technology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
