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1、编号： 时间：2021年x月x日 书山有路勤为径，学海无涯苦作舟 页码：第9页 共9页 Comparison between graticule and image capture assessment of lower tear film meniscus height J. Santodomingo-Rubido, a, , J.S. Wolffsohna and B. Gilmartina aOphthalmic Research Group, School of Life and Health Sciences, Aston University, Birming

2、ham, UK Available online 14 July 2006. Abstract Purpose To compare graticule and image capture assessment of the lower tear film meniscus height (TMH). Methods Lower tear film meniscus height measures were taken in the right eyes of 55 healthy subjects at two study visits separated by 6 m

3、onths. Two images of the TMH were captured in each subject with a digital camera attached to a slit-lamp biomicroscope and stored in a computer for future analysis. Using the best of two images, the TMH was quantified by manually drawing a line across the tear meniscus profile, following which the T

4、MH was measured in pixels and converted into millimetres, where one pixel corresponded to 0.0018 mm. Additionally, graticule measures were carried out by direct observation using a calibrated graticule inserted into the same slit-lamp eyepiece. The graticule was calibrated so that actual readings, i

5、n 0.03 mm increments, could be made with a 40× ocular. Results Smaller values of TMH were found in this study compared to previous studies. TMH, as measured with the image capture technique (0.13 ± 0.04 mm), was significantly greater (by approximately 0.01 ± 0.05 mm, p = 0.03) than that measured w

6、ith the graticule technique (0.12 ± 0.05 mm). No bias was found across the range sampled. Repeatability of the TMH measurements taken at two study visits showed that graticule measures were significantly different (0.02 ± 0.05 mm, p = 0.01) and highly correlated (r = 0.52, p < 0.0001), whereas image

7、 capture measures were similar (0.01 ± 0.03 mm, p = 0.16), and also highly correlated (r = 0.56, p < 0.0001). Conclusions Although graticule and image analysis techniques showed similar mean values for TMH, the image capture technique was more repeatable than the graticule technique and this can b

8、e attributed to the higher measurement resolution of the image capture (i.e. 0.0018 mm) compared to the graticule technique (i.e. 0.03 mm). Keywords: Tear meniscus height; Tear prism; Tear film; Repeatability Article Outline 1. Introduction 2. Methods 2.1. Statistical analysis 3. Results 4

9、. Discussion Acknowledgements References 1. Introduction The tear meniscus, which is formed between the lid surface and the bulbar conjunctiva, is present along the superior and inferior lid margins. It has been estimated that the tear meniscus holds 75–90% of the total volume of the tear film

10、 [1]. Therefore, careful examination of the lower lid tear meniscus height (TMH) is likely to provide a simple but clinically useful indication of tear volume. Assessment of the TMH is commonly used by eye care practitioners universally as part of routine ocular assessments [2] and [3]. However, mea

11、n absolute values of TMH in normal eyes have been reported to vary between 0.14 and 0.46 mm depending on the technique employed [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19] and [20]. Studies using calibrated graticules inserted into the slit-lamp eyepiece

12、have reported mean values which vary between 0.15 and 0.35 mm in normal healthy eyes (Table 1) [4], [5], [6], [7], [8] and [9]. Another study has used the calibrated variable slit beam height of a slit-lamp to measure the TMH and reported a mean value of 0.32 mm [10]. Video capture techniques measur

13、e the TMH by taking an image of the meniscus in which the upper and lower extent of the tear meniscus is located subjectively (often by drawing a line) and then, using computer software, convert the number of pixels between these points to a physical distance using a calibration factor. Mean values

14、of the TMH between 0.17 and 0.43 in normal healthy eyes have been reported using image capture techniques (Table 1) [11], [12], [13], [14], [15], [16] and [17]. Measures of the TMH can also be obtained by means of an optical pachymeter attached to a slit-lamp and mean values of the TMH in normal sub

15、jects have, in this case, been found to vary between 0.16 and 0.38 mm [17], [18] and [19]. Finally, optical coherence tomography, which uses low-coherence interferometry to produce two-dimensional images of optical scattering from tissues, can allow cross-sectional imaging of the TMH, giving mean re

16、ported values of 0.14 [20] and 0.27 mm [17] in normal healthy eyes. Larger values of TMH have been reported in studies in which fluorescein was instilled into the eye to enhance visualization of the tear meniscus [14] and [21]. Fluorescein is known to disrupt the tear film by reducing stability [22]

17、, [23] and [24] and this might initiate reflex lacrimation leading to higher TMH values. It is also possible that increased tear meniscus height with the use of fluorescein occurs as a result of ocular irritation and/or adding fluorescein containing-dye solution to the tear meniscus [25]. Although d

18、ifferences in the mean value of the TMH have been reported in the literature, the measurement of TMH has been found to be useful in differentiating between normal, dry eye, and nasolacrimal duct obstruction subjects [26] and [27]. Furthermore, TMH measurements have shown promising results in evaluat

19、ing the efficacy of punctual occlusion in subjects with different forms of dry eye [28]. Significant differences in TMH values have also been found between tolerant and intolerant contact lens wearers [16]. Whereas calibrated graticules inserted into the slit-lamp eyepiece might be more commonly use

20、d in clinical settings, the use of image capture techniques are predominantly used in research settings. Since the relationship between these two methods of TMH assessment has not been compared in the same subjects, the purpose of this study is to compare a graticule versus an image capture techniqu

21、e in the measurement of the TMH. Table 1. Mean ± standard deviation (S.D.) lower tear menicus height (TMH) values reported in the literature using graticule and image capture techniques Graticule Image capture Author Mean ± S.D. TMH Author Mean ± S.D. TMH Lamberts et al.

22、[4] 0.23 ± 0.09 Zaman et al. [11] 0.18 ± 0.11 Tomlinson et al. [5] 0.35 ± 0.11 Doughty et al. [12] 0.17 ± 0.05 Miller et al. [6] 0.22 ± 0.08 Doughty et al. [13] 0.19 ± 0.09 Jordan and Baum [7] 0.30 ± 0.06 Kwong and Cho [15] 0.24 ± 0.07 Papas and Vajdic [8] 0.15 ± 0.04 Glasson et al

23、. [16] 0.43 ± 0.11 Lim and Lee [9] 0.19 ± 0.05 Johnson and Murphy [17] 0.34 ± 0.05 Mean ± S.D. TMH 0.24 ± 0.07 Mean ± S.D. TMH 0.26 ± 0.10 Full-size table Results for normal subjects without instillation of fluorescein are shown. View Within Article 2. Methods Fifty-five heal

24、thy subjects (24 males and 31 females), with a mean age of 20.4 (standard deviation [S.D.] 1.6) years (range 18.4–24.7 years, median 20.1 years), with a mean ± S.D. spherical equivalent of −2.46 ± 2.34 D, and astigmatism <1.00 D, had measurements of TMH performed by one of the authors (J.S.-R.) at t

25、wo scheduled visits separated by 6 months. Ethical approval for this study was obtained from the Aston University Ethical Committee. All subjects were given written information about the study before they signed a written statement of consent to participate. The study complied with the Declaration o

26、f Helsinki. TMH was measured as the distance between the darker edge of the lower eyelid and the tear strip. Subjects were positioned on the slit-lamp chin rest and instructed to look at a target located to maintain primary eye gaze. In order to avoid reflex tearing, a relatively short light beam of

27、 low intensity was used to prevent direct shinning of the light into the pupil during TMH measurement. Two images (800 × 600 pixels) of the lower fornix and a portion of the inferior sclera and lower eyelid were brought into focus, captured using a digital camera (CKY-F58 3-CCD, JVC Americas Corp.,

28、Wayne, USA) attached to a slit-lamp (Topcon SL-7F, Tokyo, Japan) by WinTV software (v4.6, Hauppauge!, NY, USA) and stored in a computer for future analysis (Fig. 1). Using the best of two images, the TMH was quantified by manually drawing a line across the tear meniscus profile, following which the

29、TMH was measured in pixels and converted into millimetres, where one pixel corresponded to 0.0018 mm. Following image capture, the TMH was subsequently measured subjectively with a graticule (WF10Xmicro, Olympus, Tokyo) inserted into the eyepiece of the slit-lamp. The graticule was calibrated so tha

30、t actual readings, in 0.03 mm increments, could be made with a 40× ocular. With both techniques, three readings were recorded and a mean obtained. Fig. 1. Image of the tear meniscus height captured by a camera attached to the slit-lamp. Fig. 1. Image of the tear meniscus height captured by

31、a camera attached to the slit-lamp. View Within Article 2.1. Statistical analysis The distribution of values and repeatability of three consecutive measures of the TMH at the first study visit were assessed with the coefficient of skewness and the mean standard deviation (S.D.) of repeate

32、d measures, respectively. The bias between the two measuring techniques and repeatability between study visits for each technique (i.e. mean difference, S.D., and 95% confidence limits) were calculated and presented graphically [29]. Comparisons and correlations between measures were performed using

33、 paired two-tailed t-tests and the Pearson's product moment correlation coefficient, respectively. Data for the right eye only were used to avoid the confounding effect of using non-independent data from both eyes [30]. The level of statistical significance was taken as 5%. 3. Results A mean ± S.D

34、. value of TMH of 0.13 ± 0.04 (range 0.04–0.23 mm, median 0.13 mm) and 0.12 ± 0.05 mm (range 0.04–0.30 mm, median 0.11 mm) was found with the image capture and graticule techniques, respectively, at the first study visit (Fig. 2). A lower coefficient of skewness was found with the image capture meas

35、ures (0.44) compared to the graticule measures (1.04) at the first visit. The repeatability of three consecutive measures at the first visit was 0.01 and 0.004 mm for the graticule and image capture measures, respectively. TMH, as measured with the image capture technique, was significantly longer (

36、by approximately 0.01 ± 0.05 mm, p = 0.03) than that measured with the graticule technique (Fig. 3). The image capture technique could be expected to read approximately as much as 0.09 above or 0.07 below the subjective technique. There was no significant bias between the two methods of measurement

37、for the whole range of TMH values evident in this study. Both measuring techniques were highly correlated (r = 0.61, p < 0.0001). Repeatability of the TMH measurements taken at the two study visits showed that graticule measures were significantly different (0.02 ± 0.05 mm, p = 0.01) and highly corr

38、elated (r = 0.52, p < 0.0001), whereas image capture measures were similar (0.01 ± 0.03 mm, p = 0.16), but also highly correlated (r = 0.56, p < 0.0001) (Fig. 4). Fig. 2. Histogram to show the distribution of the graticule and image capture measures of the lower tear meniscus height from th

39、e 59 right eyes evaluated. Fig. 2. Histogram to show the distribution of the graticule and image capture measures of the lower tear meniscus height from the 59 right eyes evaluated. View Within Article Fig. 3. Differences between image capture and graticule measures of the lower tear m

40、eniscus height (TMH). Fig. 3. Differences between image capture and graticule measures of the lower tear meniscus height (TMH). Fig. 4. Repeatability of the graticule and image capture measures of the lower tear meniscus height (TMH) between the two study visits. Fig. 4. Repeatability of the

41、graticule and image capture measures of the lower tear meniscus height (TMH) between the two study visits. View Within Article 4. Discussion Consistent with previous studies, the values of TMH found in this study were positively skewed for both the graticule and image capture techniques [

42、4] and [12]. In addition, lower mean values of the TMH were found compared to previous studies (Table 1). However, there are a number of reports which, although slightly higher on average, have shown similar values to the TMH values reported here [8], [11], [12], [18] and [19]. Most subjects employe

43、d in this study were normal silicone hydrogel contact lens wearers (76%) and a previous study has shown lower values of TMH in silicone hydrogel lens wearers compared to normal non-contact lens wearers [6]. Special care was taken to ensure that subjects maintained primary eye gaze during the measure

44、ment of the TMH as it was noted prior to the study that when subjects were asked to look upwards the height of the tear meniscus approximately doubled, and when subjects were looking nasally, about two-thirds of the subjects showed higher values of the TMH than when they were maintaining primary eye

45、 gaze. Although some studies have measured TMH while subjects were maintaining primary eye gaze [12], [13], [15] and [17], the extent to which others studies have controlled eye gaze is unclear [4], [5], [6], [7], [8], [9], [10], [11], [14], [16], [18], [19] and [20]. In taking TMH measurements, spe

46、cial care was taken in the present study to avoid reflex tearing by direct shinning of the slit-lamp beam light into the pupil. Whereas some studies have taken steps to avoid this as a source of error [12], [13], [15] and [17], this may not have been the case in others [4], [5], [6], [7], [8], [9],

47、[10], [11], [14], [16], [18], [19] and [20]. A statistically significant difference between the two techniques of TMH measurement was found. Nevertheless, the relatively close match in the mean TMH values between the two techniques is in agreement with previous studies (Table 1). A better repeatabil

48、ity for three consecutive readings and over time was found with the image capture compared to the graticule technique, a finding likely to be attributable to the higher measurement resolution of the former (i.e. 0.0018 mm) compared to the latter (i.e. 0.03 mm). Two earlier studies using a similar im

49、age capture technique have reported comparable levels of repeatability to those found in this study [15] and [16]. In addition to the assessment of the lower TMH, a study of both the upper and lower tear meniscus height, radius of curvatures, width and cross-sectional areas is likely to provide valu

50、able information for the diagnosis and treatment of subjects with dry eyes, nasolacrimal duct obstruction and contact lens complications [14], [16], [26], [28], [31] and [32]. Clearly, the validity and repeatability of these tear meniscus parameters need to be assessed. In summary, although graticul

51、e and image analysis techniques showed similar mean values for TMH, the image capture technique was more repeatable than the graticule technique owing to its higher measurement resolution. Acknowledgement Aston University Studentship to J.S.-R. References [1] F.J. Holly, Physical chemistry of th

52、e normal and disordered tear film, Trans Ophthalmol Soc UK 104 (1985), pp. 374–380. View Record in Scopus | Cited By in Scopus (39) [2] D.R. Korb, Survey of preferred tests for diagnosis of the tear film and dry eye, Cornea 19 (2000), pp. 483–486. Full Text via CrossRef | View Record in Scopus | Ci

53、ted By in Scopus (55) [3] K.K. Nichols, J.J. Nichols and K. Zadnik, Frequency of dry eye diagnostic test procedures used in various modes of ophthalmic practice, Cornea 19 (2000), pp. 477–482. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (39) [4] D.W. Lamberts, C.S. Foster a

54、nd H.D. Perry, Schirmer test after topical anaesthesia and the tear meniscus height in normal eyes, Arch Ophthalmol 97 (1979), pp. 1082–1085. View Record in Scopus | Cited By in Scopus (68) [5] A. Tomlinson, K.J. Blades and E.I. Pearce, What does the phenol red thread test actually measure?, Optom

55、Vis Sci 78 (2001), pp. 142–146. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (32) [6] W.L. Miller, M.J. Doughty, S. Narayanan, N.E. Leach, A. Tran and A.L. Gaume et al., A comparison of tear volume (by tear meniscus height and phenol red thread test) and tear fluid osmolarity

56、 measures in non-lens wearers and contact lens wearers, Eye Contact Lens 30 (2004), pp. 132–137. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (23) [7] A. Jordan and J. Baum, Basic tear flow. Does it exist?, Ophthalmology 87 (1980), pp. 920–930. View Record in Scopus | Cited B

57、y in Scopus (127) [8] E.B. Papas and C.M. Vajdic, Inter-ocular characteristics of the pre-contact lens tear film, Curr Eye Res 20 (2000), pp. 248–250. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (11) [9] K.J. Lim and J.H. Lee, Measurement of the tear meniscus height using 0

58、.25% fluorescein sodium, Korean J Ophthalmol 5 (1991), pp. 34–36. View Record in Scopus | Cited By in Scopus (0) [10] M. Guillon, E. Styles, J.-P. Guillon and C. Maïssa, Preocular tear film characteristics of nonwearers and soft contact lens wearers, Optom Vis Sci 74 (1997), pp. 273–279. Full Text

59、via CrossRef | View Record in Scopus | Cited By in Scopus (47) [11] M.L. Zaman, M.J. Doughty and N.F. Button, The exposed ocular surface and its relationship to spontaneous eyeblink rate in elderly Caucasians, Exp Eye Res 67 (1998), pp. 681–686. Abstract | PDF (233 K) | View Record in Scopus | Cite

60、d By in Scopus (28) [12] M.J. Doughty, M. Laiquzzaman and N.F. Button, Video-assessement of tear meniscus height in elderly Caucasians and its relationship to the exposed ocular surface, Curr Eye Res 22 (2001), pp. 420–426. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (20) [

61、13] M.J. Doughty, M. Laiquzzaman, E. Oblak and N. Button, The tear (lacrimal) meniscus height in human eyes: a useful clinical measure or an unusable variable sign?, Contact Lens Ant Eye 25 (2002), pp. 57–65. Article | PDF (264 K) | Full Text via CrossRef | View Record in Scopus | Cited By in Scopus

62、 (21) [14] J.C. Mainstone, A.S. Bruce and T.R. Golding, Tear meniscus measurement in the diagnosis of dry eye, Curr Eye Res 15 (1996), pp. 653–661. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (75) [15] Y.M. Kwong and P. Cho, Tear meniscus height in normal and dry eyes, Opto

63、m Today 4124 (2001), pp. 28–32. [16] M.J. Glasson, F. Stapleton, L. Keay, D. Sweeney and M.D.P. Willcox, Differences in clinical parameters and tear film of tolerant and intolerant contact lens wearers, Invest Ophthalmol Vis Sci 44 (2003), pp. 5116–5124. Full Text via CrossRef | View Record in Scop

64、us | Cited By in Scopus (35) [17] M.E. Johnson and P.J. Murphy, The agreement and repeatability of tear meniscus height measurement methods, Optom Vis Sci 82 (2005), pp. 1030–1037. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (27) [18] M. Port and T. Asaria, The assessment o

65、f human tear flow, J BCLA 13 (1990), pp. 76–82. Abstract | View Record in Scopus | Cited By in Scopus (27) [19] S. Patel and M.J. Port, Tear characteristics of the visual display unit operator, Optom Vis Sci 68 (1991), pp. 798–800. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus

66、 (9) [20] L. Jones, R. Leech, S. Rahman, T. Simpson and D. Fonn, A novel method to determine tear prism height, Optom Vis Sci 79 (2002) (suppl), p. 252. [21] T.R. Golding, A.S. Bruce and J.C. Mainstone, Relationship between tear meniscus parameters and tear-film breakup, Cornea 16 (1997), pp. 649–661. View Record in Scopus | Cited By in Scopus (43) [22] L.S. Mengher, A.J. Bron, S.R. Tonge and D.J. Gilbert, A non-invasive instrument for clinical assessment of the pre-corneal tear film stabilit