- Email: [email protected]
Optical profilometry: An objective method for quantification of facial wrinkles
Volume 21 Number 3, Part 2 September 1989
16. 17.
18. 19. 20.
Mouse model for photoaging
morphologic evaluation of chronic actinic dermal damage with emphasis on the role of mast cells. J Invest Dermatol 1988;90:325-30. Kaidbey KH, Kligman AM. The acute effects oflongwave ultraviolet radiation on human skin. J Invest Dermatol 1979;75:253-6. Gilchrest BA, Soter NA, Hawk JLM, et al. Histologic changes associated with ultraviolet A induced erythema in normal human skin. J AM ACAD DERMATOL 1983;9: 213-9. Kligman LH. UVA enhances low dose UVB tumorigenesis. Photochem Photobiol 1988;47:8S. Kligman LH, Kligrnan AM. Photoaging. In: Fitzpatrick TB, Eisen AZ, WolffK, et al., eds. Dermatology in general medicine. 3rd ed. New York: McGraw Hill, 1987:1470-5. Lee K_H, Tong TG. Mechanism of action of retinyl
I III
IIIII
I
21.
22. 23. 24.
compounds on wound healing. II. Effect of active retinyl derivatives on granuloma formation. J Pharm Sci 1970;59:1195-7. Hunt TK, Ehrlich HP, Garcia JA, et al. Effect of vitamin A on reversing the inhibitory effect of cortisone on healing of open wounds in animals and man. Ann Surg 1969;170:633-41. Kligman LH. Effects of all-trans-retinoieacid on the derrods of hairless mice. J AM ACADDERMATOL1986;15:77985,884-5. Kligman AM, Grove GG, Hirose R, et al. Topical tretinoin for photoaged skin. J AM ACAD DERMATOL 1986; 15(suppl):836-59. Weiss JS, Ellis CN, Headington JT, et al. Topical tretinoin improves photoaged skin: a double-blind vehicle-controlled study. JAMA 1988;259:527-32.
I
Optical profilometry: An objective method for quantification of facial wrinkles Gary L. Grove, PhD, a Mary J. Grove, MEd, a and James J. Leyden, MD b Broomall and
Philadelphia, Pennsylvania Facial fine lines and wrinkles can be faithfully captured by silicone rubber impression materials. Computerized digital image processing of such specimens provides objective measurement of the skin's topography, which has a significant degree of correlation with clinical grading. Optical profilometry provides a dimension of objectivitythat can complement clinical assessment in the study of agents that may be useful in the therapy ofphotodamaged skin. (J AM ACADDERMATOL1989;21:631-7.) The skin, especially of the face, undergoes characteristic changes with advancing age. Indeed, these facial features are usually the major clues to appraise a person's age. Although there are other overt morphologic changes that can be used as markers of cutaneous aging, the degree of wrinkling in the "crow's-feet" area seems to have the greatest impact. Thus it is not surprising that considerable effort has been expended to develop skin care products that can effectively deal with aging. Recent reports have indicated that treatment with topical aU-trans-retinoicacid can be helpful to modify many of the changes associated with photoaging, including a decrease in the appearance of wrinkles and fine lines.l, 2 Although clinical assessment and From the Skin Study Center,a and the Department of Dermatology,b University of PennsylvaniaSchoolof Medicine. Reprint requests: Gary L. Grove,PhD, Skin Study Center, 571 Abbott Dr., Broomail, PA 19008.
photography are useful methods for assessing such changes, they have drawbacks. This is especially true for photography, in which minor changes in lighting or facial expression can greatly influence the appearance of lines and wrinkles. We are also concerned that concurrent improvements in other facial features that can result from effective retinoid therapy, such as a decrease in intensity of solar lentigines and an increase in dermal blood flow, might partially unblind or unduly influence the investigator in judging the drug's impact on wrinkles. Thus there clearly is a need for a more objective method to evaluate the effect of topical agents on facial lines and wrinkles. Silicone rubber impression materials can be used to make a mold of the skin that faithfully captures the surface topography. 3 In this article we will describe how digital image processing can be used as a quantitative method for assessment of microtopographic features, Our approach is a variant of the 631
632
Journal of the American Academy of Dermatology
Grove et aL
On admission to the study, the periorbital region of each subject was examined by one of us (J.J.L), and the degree of photoaging as reflected by the crow's-feet pattern was scored by a visual analog scale. The 6-grade scoring system of Daniell8 for visual grading of facial skin wrinkling in the paraocular region was also used. A skin surface impression was then taken as will be described.
Skin surface impressions
Fig. I. Subject with crow's-feet site delineated with adhesive paper rings with tab oriented to face outward. Fig. 2. Optical profilometry profile of skin surface topography. Analysis of samples involved 10 parallel scans. procedure originally described by Corcuff and colleagues46 and allows serial monitoring of changes in facial wrinkles with extended periods between observation points.
MATERIAL AND METHODS Human subjects The experimental design and all associated procedures were approved by an Institutional Review Board for the protection of human research subjects before the start of this study. Twenty-five healthy women ranging in age from 24 to 64 years participated. All were of skin type II or III with respect to sun sensitivity7 and without a recent history of burning. None were taking any prescription medications, except oral contraceptives, and all were further restricted in their use of various over-thecounter products, cosmetics, soaps, and skin care products for the duration of this l-month study and at least 1 week before onset.
Subjects were placed in a recumbent position so that they could remain comfortable while remaining still for at least 5 minutes. Subjects were instructed to keep their eyes closed while relaxing their face as much as possible. The sampled site was in the periorbital region just lateral to the commissure of the eyes and 5 mm from the external raphe. This site was delineated by affixing 15 mm diameter adhesive paper rings (Novamatrix), and extreme care was taken to orientate the tab to face outward, toward the ear (Fig. 1). To facilitate relocating this site for subsequent serial samples, close-up 35 mm color photographs were taken of the region, with the adhesive ring properly placed for each subject. Negative skin surface replicas were obtained with Silfo silicone dental impression material (FlexicoDevelopments Ltd., Potters Bar, England). A thin layer of freshly prepared Silflo was gently spread over the bounded area of the ring with a spatula and allowed to polymerize. This occurred within 3 to 4 minutes, after which time the ring was lifted from the skin together with the replica. Each specimen was coded and stored in individual glassine envelopes until measured. To determine the reproducibility of the method, 10 persons were repetitively sampled on five different occasions during a 4-week period. At least 5 days elapsed between each successive sample, and no guides other than the reference photos were used to relocate the test site. In addition, 10 repetitive measures were taken of the same sample without any changes in the instrumental setup, and 10 repetitive measures in which the rotating sample holder and the lighting angle were altered and then restored to the original point were also taken.
Optical profilometry The Magiscan digital image processing system used in this study has been previously described. 9 Briefly, this instrument consists of a high-resolution, black-and-white video camera, which is interfaced
Volume 21 Number 3, Part 2 September 1989
Optical profilometry of facial wrinkles 633
fq
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Visual Analog Scores Fig. 3. Correlation of clinical grading according to Daniell classification and visual analog scale. Table I. Representative data from image analysis of skin surface impressions Direction
N E S W N-S E-W
7.80 3.20 7.96 3.26 7.88 3.23
0.42 0.31 0.74 0.51 0.58 0.41
into a computer that contains specially designed image-processing hardware and software. In this application, we use a program entitled "Optical Profilornetry" that is based on the National Aeronautics and Space Administration's remote sensing approach to lunar landscape mapping that was used during the Ranger missions. 1° Instead of using the sun to sidelight the moon craters and crevices, we used a fiberoptic illuminator set at a fixed angle to bring out skin surface details. The resulting image was then digitized into a 256 by 512 pixel matrix with 64 gray levels for brightness. If the gray level values across a horizontal segment of this digitized image are plotted, a profile that reflects the surface features at that specific location is created (Fig. 2). This graphic display is similar to those achieved through mechanical profilometry with mechanical stylus devices; we extract numeric information that describes the microtopographic attributes in much the same way. 3 Of the many
31.82 15.82 32.54 16.36 32.18 16.09
1.34 1.72 2.84 2.11 2.09 1.92
18.1 3.0 17.4 2.1 17.8 2.5
parameters available for assessing skin surface topography, both Rz and Ra, have proved to be especially useful. T o compute Rz, the profile is first divided into five equal segments along the x axis. The minimum-maximum differences within each segment are then determined, and R z is calculated as the average of these five local values. To compute Ra, an average line is generated to run through the center of the profile, and the area that the profile deviates above and below this line is determined. In analyzing a sample, 10 parallel scans are run, and the average Ra and R z are computed. If any of the values from any individual scan are more than 2 standard deviations away from the group average, this outlying value is eliminated, and the group average is recomputed. We have also created another parameter caUed "Shadows" that has no real counterpart in mechanical profilometry. This value refers to the total area within a standard area of the specimen that is coy-
Journal of the American Academy of Dermatology
634 Grove et aI.
15
E]FI Fi
o
lO
to
Z
5 R = 0.85
3
I
I
I
I
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43
63
83
Clinical G r a d e - Visual A n a l o g Scale
Fig. 4. Correlation of degree of facial wrinkling in crow's-feet area with optical profilometry parameter Ra.
Table II. Repetitive measures with change in setup between each run Ra average 5.59 5.57 3.84 3.79 SD 0.16 0.21 0.09 0.14 CV % 2.93 3.69 2.40 3.59 Rz average 27.61 27.58 19.64 19.59 SD 0.77 0.87 0.54 0.65 CV % 2.79 3.15 2.77 3.30 Shadow average 16.59 21.34 23.67 22.21 SD 1.50 2.71 2.53 2.01 CV % 9.06 12.72 10.70 9.05 CV, Coefficient of variatton.
ered by dark shadows and is measured by setting an arbitrary gray level threshold to segment out these regions. Obviously, if the surface is rather smooth and fiat, there will be few shadows and this value will be small, but if the surface is wrinkled and rough, the shadowed areas will correspondingly increase. Because of the skin's artisotropy, the Ra, Rz, and Shadows determinations were made with the specimens iUuminated from different orientations. To accomplish this, the fiberoptic illuminator remained at a fixed angle and distance while the specimen was axially moved in 90-degree steps on a turntable that served as the specimen holder. Measurements referred to as "North-South" were obtained with the illumination perpendicular across the major line axis, whereas measurements called "East-West" were obtained with parallel lighting.
Statistical methods Statistical analysis was performed with the STATA 2.0 Professional Version with optional Statklt (Computing Resource Center, Los Angeles, Calif.). A probability value of <0.05 was used as the level for determining significance in all evaluations. RESULTS Clinical evaluations The distribution of our subject population, as classified according to the scoring scheme of Daniell,8 is highly skewed toward the slight-to-moderate levels, with no representation in the most severe categories. As expected, there was a high degree of correlation between the visual analog scale values of wrinkling and the DanieU classes (Fig. 3).
Skin surface impressions Although 25 women participated in this study, we were able to obtain good quality skin surface impressions from only 23. The primary problem with the remaining two was that their impressions lacked a crispness of details. Because both subjects had excessively oily skin, we suspect that some component of the skin surface lipids interfered with the polymerization of the silicone rubber film. Indeed, precleaning the surface with methanol seemed to improve the quality of the replica; nevertheless, we felt it best to exclude these two subjects from further consideration because this pretreatment alters the skin surface. Representative data from a single
Volume 21 Number 3, Part 2 September 1989
Optical profilometry of facial wrinkles 635
Table HI. Coefficient of variation for serial samples on same persons Ra Subject No.
N-S
1 2 3 4 5 6 7 8 9 10 Average
9.89 10.84 6.59 10.07 10.05 5.77 9.11 9.38 8.52 7.34 8.76
1
Rz
Shadows
E-W
N-S
E-W
N-S
[
E-W
11.04 9.95 4.83 8.24 4.88 4.12 5.99 12.10 6.98 8.11 7.62
6.40 9.43 8.02 9.44 7.98 3.84 6.63 3.96 9.20 7.23 7.21
11.25 12.16 8.73 7.81 5.66 4.33 7.83 9.93 8.70 6.90 8.33
22.93 20.76 11.18 13.50 5.47 8.50 15.46 3.22 15.81 12.37 12.92
30.82 27.11 38.64 21.00 16.24 9.16 9.82 8.18 12.60 18.13 19.17
1.0000 0.5550
1.0000
Table IV. Coefficient of variance matrix Visual Ra N-S Ra E-W Rz N-S Rz E-W Shadow N-S Shadow E-W
1.0000 0.8520 0.1424 0.7913 -0.2380 0.5837 -0.0243
1.0000 0.1076 0.8689 -0.3113 0.7694 0.1110
1.0000 0.0189 0.8267 0.0723 0.5886
specimen are shown in Table I. In general, the values are higher when taken in either the North or South orientation because the major lines are best highlighted with cross-illumination. Because only small differences are to be expected from measurements taken at 180 degrees from one another, North and South, as well as the East and West, values have been pooled to derive six measurements (Ra, Rz, and Shadows in both axes) from each specimen, respectively.
Reproducibility of the method Repetitive measures taken of the same sample with no intervening changes in instrumental setup showed a coefficient of variation for Ra and Rz that was less than 1%. Table II shows that if placement on the rotating sample holder and lighting angle are altered and then restored between each measurement, the coefficient of variation increases to approximately 3%. These values represent instrumental variations that are encountered when dealing with an individual specimen. We must also be concerned with other variations that arise from relocating the sample site or batches of silicone rubber, which would further decrease the reproducibility of
1.0000 -0.3189 0.6190 -0.0539
1.0000 -0.2959 0.4177
this method. The data from serial assessments of the same 10 women shown in Table III indicate that with repeat sampling, the coefficient of variation for the overall method, as far as Ra and Rz are concerned, is approximately 8%. Some of this may be the result of biologic variations in skin surface topography that arise from changes in ambient conditions, menstrual cycle, etc. Under all conditions, the reproducibility of the measurements based on Shadows is only half that of those based on Ra and Rz. Most likely this is because of the need to create an arbitrary gray level threshold to segment the scene into a binary image of shadowed and nonshadowed regions. Such procedures are extremely sensitive to smaU changes in brightness that would have little or no impact on the profile parameters.
Correlation of image analysis results with clinical gradings Table IV shows a matrix of correlation coefficients between the various parameters measured in this study. Note that the greatest degree of agreement with the expert grader's ratings obtained from the visual analog scales with either Ra, Rz, or Shad-
Journal of the
636
American Academy of Dermatology
Grove et aL
50-
0 o
0 0
40-
..e O
0
Z
N
30-
0 0
2O 3
R =
0.79
I
I
I
I
23
43
63
83
Clinical G r a d e - Visual A n a l o g Scale
Fig. 5. Correlation of degree of facial wrinkling in crow's-feet area with optical profilometry parameter Rz.
40
0
O0 0
0 0 0
30
0
0
0 0
20 cOD
0o 0 IO R = 0.58
o 3
I
I
I
I
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43
63
83
Clinical G r a d e - Visual A n a l o g Scale
Fig. 6. Correlation of degree of facial wrinkling in crow's-feet area with optical profilometry parameter Shadows.
ows is that obtained in the North-South orientation. This is to be expected, since the major lines and features are best highlighted under these conditions of illumination. Graphic displays of the correlographs on the basis of North-South measures of Ra, Rz, and Shadows are presented in Figs. 4 to 6, respectively. Close inspection of both the Ra and Rz plots indicates that neither value shows any clearcut changes over the
lower ranges of the expert grading's rating scale. This suggests that optical pmftlometry is less sensitive than the well-trained eye in evaluating very fine lines. Shadows values are also more spread out and do not correlate as well as the other two measures. CONCLUSIONS
Previous studies 5,6,8,11 have estab/ished that a strong association exists between the evolution of
Volume 21 Number 3, Part 2 September 1989 wrinkles in the crow's-feet region and the degree of past sun exposure. Indeed, on the basis of a survey of 900 persons, DanieU 8 calculated that after controlling for age and smoking history, subjects who averaged more than 4 hours of current daily outdoor exposure were 2.5 times more likely to have prominent crow's-feet than persons who spent less than 2 hours a day outdoors. In a collaborative study with Corcuff's group, 6 we found that crow's-feet patterns in American women were formed by 35 years of age and continuously deepened with advancing age. Although the present study has not addressed the underlying mechanisms that account for the observed changes, we agree with Kligman 1: that surface topography most probably reflects alterations in the elastic network of the upper dermis instead of morphologic organization of the collagen bundles. Clinical studies of cosmetics or drugs for their effects on facial wrinkling have relied on clinical judgment and photography for assessing changes caused by therapy. In this study we have demonstrated that digital image processing of skin surface replicas provides a suitable methodology for quantification of facial lines and wrinkles. Optical profilometry of skin surface replicas is an objective method that adds a dimension of quantification that can complement the clinical evaluation of treatment of photoaged skin. REFERENCES
1. Weiss JS, Ellis CN, Headington JT, et al. Topical tretinoin improves photoaged skin: a double-blind vehicle-controlled study. JAMA 1988;259:527-32.
Optical profilometry of facial wrinkles 637 2. Kligman AM, Grove GL, Hirose R, Leyden JJ. Topical tretinoin for photoaged skin. J AM ACAD DERivlATOL 1986;15:836-59. 3. GroveGL, GroveMJ. Objectivemethods for assessingskin surface topographynoninvasively.In: LevequeJL, ed. Cutaneous investigation in health an disease. New York: Marcel Dekker, 1989:1-32. 4. Corcuff P, Chatenay F, Leveque JL. A fully automated system to study skin surface patterns. Int J Cosmet Sci 1984;6:167-76. 5. CorcuffP,deRigalJ, LevequeJL, Maldd S,Agache P. Skin relief and aging. J Soc Cosmet Chem 1983;34:177-90. 6. CorcaffP, LevequeJL, Grove GL, Kligman AM. The impact of agingon the microreliefofperio-orbital and leg skin. J Soc Cosmet Chem 1987;82:145-52. 7. Pathak MJ. Sunscreens and their use in the preventive treatment of sunlight-induced skin damage. J Dermatol Surg Oncol 1987;13:739-50. 8. Daniell HW. Smoker's wrinkles: a study in the epidemiology of "crow's feet." Ann Intern Med 1971;75:873-80. 9. Grove GL. Dermatological applications of the Magiscan image analyzing computer. In: Marks R, Payne PA, eds. Bioengineering and the skin. New York: MTP Press, 1981:173-80. 10. Schurmeier HM, Heacock RL, Wolfe AE. The ranger mission to the moon. Sci Am 1966;214:52-67. 11. Holman CDJ, Armstrong BK, Evans PR, et al. Relationship of solar keratosis and history of skin cancer to objective measures of actinic skin damage. Br J Dermatol 1984;110:129-38. 12. KligmanAM. The classificationand treatmenf of wrinkles. In: Kligman AM, Takase Y, eds. Cutaneous aging. Tokyo: University of Tokyo Press, 1989:547-56.
16. 17.
18. 19. 20.
Mouse model for photoaging
morphologic evaluation of chronic actinic dermal damage with emphasis on the role of mast cells. J Invest Dermatol 1988;90:325-30. Kaidbey KH, Kligman AM. The acute effects oflongwave ultraviolet radiation on human skin. J Invest Dermatol 1979;75:253-6. Gilchrest BA, Soter NA, Hawk JLM, et al. Histologic changes associated with ultraviolet A induced erythema in normal human skin. J AM ACAD DERMATOL 1983;9: 213-9. Kligman LH. UVA enhances low dose UVB tumorigenesis. Photochem Photobiol 1988;47:8S. Kligman LH, Kligrnan AM. Photoaging. In: Fitzpatrick TB, Eisen AZ, WolffK, et al., eds. Dermatology in general medicine. 3rd ed. New York: McGraw Hill, 1987:1470-5. Lee K_H, Tong TG. Mechanism of action of retinyl
I III
IIIII
I
21.
22. 23. 24.
compounds on wound healing. II. Effect of active retinyl derivatives on granuloma formation. J Pharm Sci 1970;59:1195-7. Hunt TK, Ehrlich HP, Garcia JA, et al. Effect of vitamin A on reversing the inhibitory effect of cortisone on healing of open wounds in animals and man. Ann Surg 1969;170:633-41. Kligman LH. Effects of all-trans-retinoieacid on the derrods of hairless mice. J AM ACADDERMATOL1986;15:77985,884-5. Kligman AM, Grove GG, Hirose R, et al. Topical tretinoin for photoaged skin. J AM ACAD DERMATOL 1986; 15(suppl):836-59. Weiss JS, Ellis CN, Headington JT, et al. Topical tretinoin improves photoaged skin: a double-blind vehicle-controlled study. JAMA 1988;259:527-32.
I
Optical profilometry: An objective method for quantification of facial wrinkles Gary L. Grove, PhD, a Mary J. Grove, MEd, a and James J. Leyden, MD b Broomall and
Philadelphia, Pennsylvania Facial fine lines and wrinkles can be faithfully captured by silicone rubber impression materials. Computerized digital image processing of such specimens provides objective measurement of the skin's topography, which has a significant degree of correlation with clinical grading. Optical profilometry provides a dimension of objectivitythat can complement clinical assessment in the study of agents that may be useful in the therapy ofphotodamaged skin. (J AM ACADDERMATOL1989;21:631-7.) The skin, especially of the face, undergoes characteristic changes with advancing age. Indeed, these facial features are usually the major clues to appraise a person's age. Although there are other overt morphologic changes that can be used as markers of cutaneous aging, the degree of wrinkling in the "crow's-feet" area seems to have the greatest impact. Thus it is not surprising that considerable effort has been expended to develop skin care products that can effectively deal with aging. Recent reports have indicated that treatment with topical aU-trans-retinoicacid can be helpful to modify many of the changes associated with photoaging, including a decrease in the appearance of wrinkles and fine lines.l, 2 Although clinical assessment and From the Skin Study Center,a and the Department of Dermatology,b University of PennsylvaniaSchoolof Medicine. Reprint requests: Gary L. Grove,PhD, Skin Study Center, 571 Abbott Dr., Broomail, PA 19008.
photography are useful methods for assessing such changes, they have drawbacks. This is especially true for photography, in which minor changes in lighting or facial expression can greatly influence the appearance of lines and wrinkles. We are also concerned that concurrent improvements in other facial features that can result from effective retinoid therapy, such as a decrease in intensity of solar lentigines and an increase in dermal blood flow, might partially unblind or unduly influence the investigator in judging the drug's impact on wrinkles. Thus there clearly is a need for a more objective method to evaluate the effect of topical agents on facial lines and wrinkles. Silicone rubber impression materials can be used to make a mold of the skin that faithfully captures the surface topography. 3 In this article we will describe how digital image processing can be used as a quantitative method for assessment of microtopographic features, Our approach is a variant of the 631
632
Journal of the American Academy of Dermatology
Grove et aL
On admission to the study, the periorbital region of each subject was examined by one of us (J.J.L), and the degree of photoaging as reflected by the crow's-feet pattern was scored by a visual analog scale. The 6-grade scoring system of Daniell8 for visual grading of facial skin wrinkling in the paraocular region was also used. A skin surface impression was then taken as will be described.
Skin surface impressions
Fig. I. Subject with crow's-feet site delineated with adhesive paper rings with tab oriented to face outward. Fig. 2. Optical profilometry profile of skin surface topography. Analysis of samples involved 10 parallel scans. procedure originally described by Corcuff and colleagues46 and allows serial monitoring of changes in facial wrinkles with extended periods between observation points.
MATERIAL AND METHODS Human subjects The experimental design and all associated procedures were approved by an Institutional Review Board for the protection of human research subjects before the start of this study. Twenty-five healthy women ranging in age from 24 to 64 years participated. All were of skin type II or III with respect to sun sensitivity7 and without a recent history of burning. None were taking any prescription medications, except oral contraceptives, and all were further restricted in their use of various over-thecounter products, cosmetics, soaps, and skin care products for the duration of this l-month study and at least 1 week before onset.
Subjects were placed in a recumbent position so that they could remain comfortable while remaining still for at least 5 minutes. Subjects were instructed to keep their eyes closed while relaxing their face as much as possible. The sampled site was in the periorbital region just lateral to the commissure of the eyes and 5 mm from the external raphe. This site was delineated by affixing 15 mm diameter adhesive paper rings (Novamatrix), and extreme care was taken to orientate the tab to face outward, toward the ear (Fig. 1). To facilitate relocating this site for subsequent serial samples, close-up 35 mm color photographs were taken of the region, with the adhesive ring properly placed for each subject. Negative skin surface replicas were obtained with Silfo silicone dental impression material (FlexicoDevelopments Ltd., Potters Bar, England). A thin layer of freshly prepared Silflo was gently spread over the bounded area of the ring with a spatula and allowed to polymerize. This occurred within 3 to 4 minutes, after which time the ring was lifted from the skin together with the replica. Each specimen was coded and stored in individual glassine envelopes until measured. To determine the reproducibility of the method, 10 persons were repetitively sampled on five different occasions during a 4-week period. At least 5 days elapsed between each successive sample, and no guides other than the reference photos were used to relocate the test site. In addition, 10 repetitive measures were taken of the same sample without any changes in the instrumental setup, and 10 repetitive measures in which the rotating sample holder and the lighting angle were altered and then restored to the original point were also taken.
Optical profilometry The Magiscan digital image processing system used in this study has been previously described. 9 Briefly, this instrument consists of a high-resolution, black-and-white video camera, which is interfaced
Volume 21 Number 3, Part 2 September 1989
Optical profilometry of facial wrinkles 633
fq
5
4
[3
rq [3
[q
3
[] []
e-
121
2
[]
[]
r]
][]
1
0 3
FI
n =
I
I
I
23
43
63
0.94
"
I
83
Visual Analog Scores Fig. 3. Correlation of clinical grading according to Daniell classification and visual analog scale. Table I. Representative data from image analysis of skin surface impressions Direction
N E S W N-S E-W
7.80 3.20 7.96 3.26 7.88 3.23
0.42 0.31 0.74 0.51 0.58 0.41
into a computer that contains specially designed image-processing hardware and software. In this application, we use a program entitled "Optical Profilornetry" that is based on the National Aeronautics and Space Administration's remote sensing approach to lunar landscape mapping that was used during the Ranger missions. 1° Instead of using the sun to sidelight the moon craters and crevices, we used a fiberoptic illuminator set at a fixed angle to bring out skin surface details. The resulting image was then digitized into a 256 by 512 pixel matrix with 64 gray levels for brightness. If the gray level values across a horizontal segment of this digitized image are plotted, a profile that reflects the surface features at that specific location is created (Fig. 2). This graphic display is similar to those achieved through mechanical profilometry with mechanical stylus devices; we extract numeric information that describes the microtopographic attributes in much the same way. 3 Of the many
31.82 15.82 32.54 16.36 32.18 16.09
1.34 1.72 2.84 2.11 2.09 1.92
18.1 3.0 17.4 2.1 17.8 2.5
parameters available for assessing skin surface topography, both Rz and Ra, have proved to be especially useful. T o compute Rz, the profile is first divided into five equal segments along the x axis. The minimum-maximum differences within each segment are then determined, and R z is calculated as the average of these five local values. To compute Ra, an average line is generated to run through the center of the profile, and the area that the profile deviates above and below this line is determined. In analyzing a sample, 10 parallel scans are run, and the average Ra and R z are computed. If any of the values from any individual scan are more than 2 standard deviations away from the group average, this outlying value is eliminated, and the group average is recomputed. We have also created another parameter caUed "Shadows" that has no real counterpart in mechanical profilometry. This value refers to the total area within a standard area of the specimen that is coy-
Journal of the American Academy of Dermatology
634 Grove et aI.
15
E]FI Fi
o
lO
to
Z
5 R = 0.85
3
I
I
I
I
23
43
63
83
Clinical G r a d e - Visual A n a l o g Scale
Fig. 4. Correlation of degree of facial wrinkling in crow's-feet area with optical profilometry parameter Ra.
Table II. Repetitive measures with change in setup between each run Ra average 5.59 5.57 3.84 3.79 SD 0.16 0.21 0.09 0.14 CV % 2.93 3.69 2.40 3.59 Rz average 27.61 27.58 19.64 19.59 SD 0.77 0.87 0.54 0.65 CV % 2.79 3.15 2.77 3.30 Shadow average 16.59 21.34 23.67 22.21 SD 1.50 2.71 2.53 2.01 CV % 9.06 12.72 10.70 9.05 CV, Coefficient of variatton.
ered by dark shadows and is measured by setting an arbitrary gray level threshold to segment out these regions. Obviously, if the surface is rather smooth and fiat, there will be few shadows and this value will be small, but if the surface is wrinkled and rough, the shadowed areas will correspondingly increase. Because of the skin's artisotropy, the Ra, Rz, and Shadows determinations were made with the specimens iUuminated from different orientations. To accomplish this, the fiberoptic illuminator remained at a fixed angle and distance while the specimen was axially moved in 90-degree steps on a turntable that served as the specimen holder. Measurements referred to as "North-South" were obtained with the illumination perpendicular across the major line axis, whereas measurements called "East-West" were obtained with parallel lighting.
Statistical methods Statistical analysis was performed with the STATA 2.0 Professional Version with optional Statklt (Computing Resource Center, Los Angeles, Calif.). A probability value of <0.05 was used as the level for determining significance in all evaluations. RESULTS Clinical evaluations The distribution of our subject population, as classified according to the scoring scheme of Daniell,8 is highly skewed toward the slight-to-moderate levels, with no representation in the most severe categories. As expected, there was a high degree of correlation between the visual analog scale values of wrinkling and the DanieU classes (Fig. 3).
Skin surface impressions Although 25 women participated in this study, we were able to obtain good quality skin surface impressions from only 23. The primary problem with the remaining two was that their impressions lacked a crispness of details. Because both subjects had excessively oily skin, we suspect that some component of the skin surface lipids interfered with the polymerization of the silicone rubber film. Indeed, precleaning the surface with methanol seemed to improve the quality of the replica; nevertheless, we felt it best to exclude these two subjects from further consideration because this pretreatment alters the skin surface. Representative data from a single
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Optical profilometry of facial wrinkles 635
Table HI. Coefficient of variation for serial samples on same persons Ra Subject No.
N-S
1 2 3 4 5 6 7 8 9 10 Average
9.89 10.84 6.59 10.07 10.05 5.77 9.11 9.38 8.52 7.34 8.76
1
Rz
Shadows
E-W
N-S
E-W
N-S
[
E-W
11.04 9.95 4.83 8.24 4.88 4.12 5.99 12.10 6.98 8.11 7.62
6.40 9.43 8.02 9.44 7.98 3.84 6.63 3.96 9.20 7.23 7.21
11.25 12.16 8.73 7.81 5.66 4.33 7.83 9.93 8.70 6.90 8.33
22.93 20.76 11.18 13.50 5.47 8.50 15.46 3.22 15.81 12.37 12.92
30.82 27.11 38.64 21.00 16.24 9.16 9.82 8.18 12.60 18.13 19.17
1.0000 0.5550
1.0000
Table IV. Coefficient of variance matrix Visual Ra N-S Ra E-W Rz N-S Rz E-W Shadow N-S Shadow E-W
1.0000 0.8520 0.1424 0.7913 -0.2380 0.5837 -0.0243
1.0000 0.1076 0.8689 -0.3113 0.7694 0.1110
1.0000 0.0189 0.8267 0.0723 0.5886
specimen are shown in Table I. In general, the values are higher when taken in either the North or South orientation because the major lines are best highlighted with cross-illumination. Because only small differences are to be expected from measurements taken at 180 degrees from one another, North and South, as well as the East and West, values have been pooled to derive six measurements (Ra, Rz, and Shadows in both axes) from each specimen, respectively.
Reproducibility of the method Repetitive measures taken of the same sample with no intervening changes in instrumental setup showed a coefficient of variation for Ra and Rz that was less than 1%. Table II shows that if placement on the rotating sample holder and lighting angle are altered and then restored between each measurement, the coefficient of variation increases to approximately 3%. These values represent instrumental variations that are encountered when dealing with an individual specimen. We must also be concerned with other variations that arise from relocating the sample site or batches of silicone rubber, which would further decrease the reproducibility of
1.0000 -0.3189 0.6190 -0.0539
1.0000 -0.2959 0.4177
this method. The data from serial assessments of the same 10 women shown in Table III indicate that with repeat sampling, the coefficient of variation for the overall method, as far as Ra and Rz are concerned, is approximately 8%. Some of this may be the result of biologic variations in skin surface topography that arise from changes in ambient conditions, menstrual cycle, etc. Under all conditions, the reproducibility of the measurements based on Shadows is only half that of those based on Ra and Rz. Most likely this is because of the need to create an arbitrary gray level threshold to segment the scene into a binary image of shadowed and nonshadowed regions. Such procedures are extremely sensitive to smaU changes in brightness that would have little or no impact on the profile parameters.
Correlation of image analysis results with clinical gradings Table IV shows a matrix of correlation coefficients between the various parameters measured in this study. Note that the greatest degree of agreement with the expert grader's ratings obtained from the visual analog scales with either Ra, Rz, or Shad-
Journal of the
636
American Academy of Dermatology
Grove et aL
50-
0 o
0 0
40-
..e O
0
Z
N
30-
0 0
2O 3
R =
0.79
I
I
I
I
23
43
63
83
Clinical G r a d e - Visual A n a l o g Scale
Fig. 5. Correlation of degree of facial wrinkling in crow's-feet area with optical profilometry parameter Rz.
40
0
O0 0
0 0 0
30
0
0
0 0
20 cOD
0o 0 IO R = 0.58
o 3
I
I
I
I
23
43
63
83
Clinical G r a d e - Visual A n a l o g Scale
Fig. 6. Correlation of degree of facial wrinkling in crow's-feet area with optical profilometry parameter Shadows.
ows is that obtained in the North-South orientation. This is to be expected, since the major lines and features are best highlighted under these conditions of illumination. Graphic displays of the correlographs on the basis of North-South measures of Ra, Rz, and Shadows are presented in Figs. 4 to 6, respectively. Close inspection of both the Ra and Rz plots indicates that neither value shows any clearcut changes over the
lower ranges of the expert grading's rating scale. This suggests that optical pmftlometry is less sensitive than the well-trained eye in evaluating very fine lines. Shadows values are also more spread out and do not correlate as well as the other two measures. CONCLUSIONS
Previous studies 5,6,8,11 have estab/ished that a strong association exists between the evolution of
Volume 21 Number 3, Part 2 September 1989 wrinkles in the crow's-feet region and the degree of past sun exposure. Indeed, on the basis of a survey of 900 persons, DanieU 8 calculated that after controlling for age and smoking history, subjects who averaged more than 4 hours of current daily outdoor exposure were 2.5 times more likely to have prominent crow's-feet than persons who spent less than 2 hours a day outdoors. In a collaborative study with Corcuff's group, 6 we found that crow's-feet patterns in American women were formed by 35 years of age and continuously deepened with advancing age. Although the present study has not addressed the underlying mechanisms that account for the observed changes, we agree with Kligman 1: that surface topography most probably reflects alterations in the elastic network of the upper dermis instead of morphologic organization of the collagen bundles. Clinical studies of cosmetics or drugs for their effects on facial wrinkling have relied on clinical judgment and photography for assessing changes caused by therapy. In this study we have demonstrated that digital image processing of skin surface replicas provides a suitable methodology for quantification of facial lines and wrinkles. Optical profilometry of skin surface replicas is an objective method that adds a dimension of quantification that can complement the clinical evaluation of treatment of photoaged skin. REFERENCES
1. Weiss JS, Ellis CN, Headington JT, et al. Topical tretinoin improves photoaged skin: a double-blind vehicle-controlled study. JAMA 1988;259:527-32.
Optical profilometry of facial wrinkles 637 2. Kligman AM, Grove GL, Hirose R, Leyden JJ. Topical tretinoin for photoaged skin. J AM ACAD DERivlATOL 1986;15:836-59. 3. GroveGL, GroveMJ. Objectivemethods for assessingskin surface topographynoninvasively.In: LevequeJL, ed. Cutaneous investigation in health an disease. New York: Marcel Dekker, 1989:1-32. 4. Corcuff P, Chatenay F, Leveque JL. A fully automated system to study skin surface patterns. Int J Cosmet Sci 1984;6:167-76. 5. CorcuffP,deRigalJ, LevequeJL, Maldd S,Agache P. Skin relief and aging. J Soc Cosmet Chem 1983;34:177-90. 6. CorcaffP, LevequeJL, Grove GL, Kligman AM. The impact of agingon the microreliefofperio-orbital and leg skin. J Soc Cosmet Chem 1987;82:145-52. 7. Pathak MJ. Sunscreens and their use in the preventive treatment of sunlight-induced skin damage. J Dermatol Surg Oncol 1987;13:739-50. 8. Daniell HW. Smoker's wrinkles: a study in the epidemiology of "crow's feet." Ann Intern Med 1971;75:873-80. 9. Grove GL. Dermatological applications of the Magiscan image analyzing computer. In: Marks R, Payne PA, eds. Bioengineering and the skin. New York: MTP Press, 1981:173-80. 10. Schurmeier HM, Heacock RL, Wolfe AE. The ranger mission to the moon. Sci Am 1966;214:52-67. 11. Holman CDJ, Armstrong BK, Evans PR, et al. Relationship of solar keratosis and history of skin cancer to objective measures of actinic skin damage. Br J Dermatol 1984;110:129-38. 12. KligmanAM. The classificationand treatmenf of wrinkles. In: Kligman AM, Takase Y, eds. Cutaneous aging. Tokyo: University of Tokyo Press, 1989:547-56.