Open Access
Cornea & External Disease  |   June 2023
Diagnosis of Photokeratitis by Tear Ferning Using a Novel Set of SK Grading Criteria in a UVB-Induced Mouse Model
Author Affiliations & Notes
  • Kevin Kai-Wen Chen
    Department of Medical Laboratory and Biotechnology, Chung Shan Medical University, Taichung, Taiwan
  • Sophie Meng-Tien Hsieh
    Department of Medical Laboratory and Biotechnology, Chung Shan Medical University, Taichung, Taiwan
  • Han-Hsin Chang
    Department of Nutrition, Chung Shan Medical University, Taichung, Taiwan
  • David Pei-Cheng Lin
    Department of Medical Laboratory and Biotechnology, Chung Shan Medical University, Taichung, Taiwan
    Department of Ophthalmology, Chung Shan Medical University Hospital, Taichung, Taiwan
  • Correspondence: David Pei-Cheng Lin, Department of Medical Laboratory and Biotechnology, Chung Shan Medical University, No. 110, Chien-Kuo North Road, Taichung City 40201, Taiwan. e-mail: pcl@csmu.edu.tw 
  • Han-Hsin Chang, Department of Nutrition, Chung Shan Medical University, No. 110, Chien-Kuo North Road, Taichung City 40201, Taiwan. e-mail: jhhc@csmu.edu.tw 
Translational Vision Science & Technology June 2023, Vol.12, 25. doi:https://doi.org/10.1167/tvst.12.6.25
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      Kevin Kai-Wen Chen, Sophie Meng-Tien Hsieh, Han-Hsin Chang, David Pei-Cheng Lin; Diagnosis of Photokeratitis by Tear Ferning Using a Novel Set of SK Grading Criteria in a UVB-Induced Mouse Model. Trans. Vis. Sci. Tech. 2023;12(6):25. https://doi.org/10.1167/tvst.12.6.25.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Current ocular surface diagnostic methods may not totally meet and implement the clinical demands for early and precise treatments. The tear ferning (TF) test has been known as a quick, simple, and inexpensive procedure. This study aimed to validate the TF test as an alternative method for early determination of photokeratitis status.

Methods: The tear sample was collected from the UVB-induced photokeratitis eyes and processed for TF formation. The TF patterns were graded by both the Masmali and a Sophie-Kevin (SK) grading criteria, a new set of criteria modified from the Masmali grading, for differential diagnoses. In addition, the TF test results were correlated with three clinical ocular surface indicators, including tear volume (TV), tear film break-up time (TBUT), and cornea staining, to evaluate the diagnostic capacity.

Results: Differential diagnosis between the normal and the photokeratitis status was achieved by the TF test. The SK grading reflected earlier photokeratitis status than the Masmali grading criteria. The TF results were strongly correlated with the three clinical ocular surface indicators, particularly for the TBUT and cornea staining.

Conclusions: The TF test was proven to have a capacity to distinguish photokeratitis from the normal status at an early stage by using the SK grading criteria. It is therefore potentially useful for photokeratitis diagnosis in the clinical settings.

Translational Relevance: The TF test may fulfill the demands of precise and early diagnosis to facilitate in time the intervention for photokeratitis.

Introduction
Ultraviolet radiation (UVR) has been known to cause photothermal and photomechanical damages,1 including cellular apoptosis,2 DNA damage,3,4 and detrimental accumulation of reactive free radicals.35 The scenario may be referred as photokeratitis to describe the acute reactions to UVR-induced “burns.” The most reported cases of photokeratitis are “snow blindness” and “welder's flash.”6 The snow blindness occurs from excessive UVB irradiation under naturally high-reflective environments. On the other hand, the welder's flash results from exposure to artificial UVB (and sometimes UVC), such as those from a welder's arc.6 
The earliest symptoms of photokeratitis emerge as a gritty ocular sensation, followed by photophobia and tearing. These initial symptoms are caused by the loss and damage of cornea epithelial cells on the superficial ocular surface. This leads to corneal edema, resulting in haze and vision impairment. Further exposure to UVR would cause epithelial exfoliation and severe pain.7,8 Furthermore, UVB irradiation can induce inflammatory responses,912 which is regarded as the key mechanisms in photokeratitis.1 
The tear film, a thin moist layer covering the cornea, plays an important role on the ocular surface. It not only has an immune protective effect, but also provides nutrients to the cornea.13,14 Therefore, a close relationship exists between the status of the tear film and the health of the cornea. Given that the quality and quantity of tear film are crucial for ocular health, the ways to examine these tear characteristics are pivotal for ophthalmic diagnosis. Current ocular surface diagnostic methods include tear volume (TV), tear film break-up time (TBUT), and cornea staining.15 However, the use of current protocols may not totally meet the demand for early and precise diagnosis, due to the weak correlation among different indicators.16,17 For diagnosis of photokeratitis, the major methods include slit-lamp examination, corneal fluorescein staining, ocular ultrasound, and visual acuity testing.6,18 For these major methods to be helpful, the photokeratitis status is already at certain stages later than the initiation period. Thus, cultivation of a novel, easy to perform, and capable early diagnostic method is advantageous. 
The tear ferning (TF) test is known as a quick, simple, and inexpensive test for tear sample assessment. It is performed by putting a drop of tear sample on a glass slide, and allowed to air dry in order to form the TF patterns.19 The previous studies have shown good sensitivity, specificity, and repeatability20,21 using the TF test. In our previous study, the mouse TF test protocol has been established by using a wash solution for collection of a small amount of tear sample,22 which potentially may be applicable to assess clinical photokeratitis at the early stage. 
To develop TF as a novel diagnostic test, we investigated whether the TF patterns can be distinguished between normal and photokeratitis status in a mouse UVB-induced model, by using both the Masmali and the Sophie-Kevin (SK) grading criteria established in the present study. To further validate the TF test, other indicators commonly used for ocular surface diagnosis were correlated with the TF grades. 
Materials and Methods
Animals
Twelve 8-week-old female Institute of Cancer Research (ICR) mice were purchased from BioLASCO Taiwan Co., Ltd, Taipei, Taiwan. The mice were fed ad libitum and kept at 20°C to 24°C with 50% to 55% humidity under a 12 hour:12 hour light-dark cycle. Only mice without anomalies of the anterior eye (cornea, anterior chamber, iris, or lens) were included in the experiments. All procedures involving mice were reviewed and approved by the Institutional Animal Care and Use Committee of Chung Shan Medical University and were performed in accordance with the Association for Research in Vision and Ophthalmology (ARVO) Resolution on the Use of Animals in Ophthalmic and Vision Research. 
Photokeratitis Model
The mice were randomly divided into two groups: blank control (blank) and UVB-damaged (damage). Each group contained six mice. After the mice were anesthetized with 2.5% Avertin (Sigma-Aldrich, St. Louis, MO) at 400 mg/kg by intraperitoneal injection,22 the eyes of the damage group were directly exposed to UVB light (LF-206LS; UVItec Limited, England) in a darkroom once daily.12 The UVB source was set at 8 mW/cm2 with exposure time for 90 seconds to reach a total amount of 0.72 J/cm2 /day, during a 10-day (days 1 to 10) experiment period. The UVB light wavelength ranged between 280 nm and 320 nm with a peak at 312 nm, which was confirmed with a UV detector (VLX-3W; Vilber Lourmat). After the UVB irradiation, the mice were transferred to their original cages and set under normal room light. The mice of the blank group were treated in a similar manner except they were exposured to UVB light. 
Data Collection and Assessment Schedule
Before every measurement, the mice were anesthetized with intraperitoneal 2.5% Avertin injection (Sigma-Aldrich, St. Louis, MO) at 400 mg/kg. The TF tests were conducted on days 0, 3, 4, 5, 7, 9, and 10. To avoid potential interference with the TF tests, assessments of TV and TBUT were performed on day 11. The cornea stain photography was conducted on day 12. Measurements were performed and the data were obtained from both the right and the left eyes. 
Measurement of TV
The TV was measured under anesthetized condition with a tear test strip (Advantech test paper; Tokyo Roshi Kaisha, Japan) of 1-mm width.23 The lower eyelid was pulled down slightly and a strip was placed on the palpebral conjunctiva for 20 seconds. The moistened length of the strip was measured in millimeters. The TV test was repeated three times for each eye with the average taken as the results. 
Measurement of TBUT
The TBUT assessments were performed with instilling 5 µL of 1% fluorescein on the center cornea using a micropipette.24 The eyelid closures were manually aided for three times, and the ocular surface was examined under a dissection stereoscope (Stemi SV 11; Carl Zeiss, Germany) with an illuminating system (HBO 100; Carl Zeiss, Germany). The appearance of fluorescein in the tear film was observed under cobalt blue light. The time when the first dark spot emerged on the cornea surface was recorded. The experiment was repeated three times for each eye to obtain an average value. 
Grading of Cornea Staining
The damages of the cornea surface were examined based on the extent of lissamine green stain, according to previous publications.12,25 Each cornea was stained with 3 µL of 1% lissamine green (Sigma-Aldrich, St. Louis, MO). Images of cornea staining were taken under a dissecting microscope (SMZ 645; Nikon, Tokyo, Japan) and graded according to the following criteria. The cornea is divided into four quadrants. In each quadrant, the staining was differentiated into four levels: absent (grade 0), light (grade 1), moderate (grade 2), and severe (grade 3). The total grades of the four quadrants were summed for each eye.23 
TF Procedures
Tear samples were collected with wash solution containing 0.4% NaCl and maintained pH value at 7.5 ± 0.2. After anesthesia, a drop of 2 µL wash solution was added onto the ocular surface with a micropipette set perpendicular to the cornea. The drop was pipetted 30 to 40 times to thoroughly wash the ocular surface, avoiding loss of the solution and damage to the ocular surface. All TF tests were performed immediately after sample collection. For each test, a 1.5 µL sample was placed onto a glass slide and air-dried in an oven (LE-509RH; Yih Der, Taiwan) for 10 minutes at 24 ± 2°C and relative humidity (rH) 46 ± 3%. Each TF formation was photographed under a light microscope (DM500; Leica, Wetzlar, Germany) by 40× and 100× magnification. 
TF Grading
The patterns of TF images were graded in accordance with the Masmali21 and the SK gradings. The SK grading is a new set of criteria modified from the Masmali method to describe TF ranging from 0 to 4 by 0.5 incremental scales. 
The SK gradings were based on TF crystal patterns and non-crystal spaces as demonstrated by the area of orange color on the lower left box in each magnified photograph in Figure 1. Generally, more and wider spaces were observed as the grades were getting higher. Grade 0 was designated with the presence of dense radiating snowflake patterns (as indicated by the red arrow in Fig. 1) whereas their surrounding details were too subtle to be discerned. Grade 0.5 exhibited complex patterns and had more evident non-crystal spaces than grade 0. In addition, grade 0.5 had fine trunk crystals (indicated by red triangles). Grade 1 mainly formed fine branching patterns with even more non-crystal spaces. Compared with grade 0.5, the trunk crystals were coarser (indicated by blue triangles). Grade 1.5 had even coarser trunk crystals compared with grade 1 (indicated by yellow triangles). The fine branches appeared more irregular than those of grade 1. For grade 2, most of the TF crystals were intersected at right angles (indicated by right angle marks in red) and the gaps between neighboring branches became wider. For grade 2.5, the intersected TF crystals became broken and more non-crystal spaces were identified. Grade 3 exhibited large unbranched crystals in a cross shape (indicated by the red arrow in Fig. 1) and much more non-crystal spaces were observed. Grade 3.5 contained crystals with shorter arms and were even square-like in shape (indicated by the red arrow in Fig. 1). Grade 4 showed much less presentation of crystals, almost close to none, and the largest non-crystal area. More examples of TF grading are shown in Supplementary Figure S1
Figure 1.
 
Demonstration of the SK grading criteria for mouse TF. The details of grading criteria are described in the main text. The red boxed areas are magnified and put beneath each grade photograph. The inter-crystal spaces of each magnified photograph were painted in orange and represented by the black boxed areas on the lower left corner. The red arrows in grades 0, 3 and 3.5 are indicated by the snowflake, the cross shape, and the square-like patterns, respectively. The red triangles in grade 0.5, the blue triangles in grade 1, and the yellow triangles in grade 1.5 indicated the trunk crystals from finer to coarser, as the grade scales were increased. The red right angle marks in grade 2 indicated the intersection of TF crystals at the right angle. All the original photographs were magnified at 100×.
Figure 1.
 
Demonstration of the SK grading criteria for mouse TF. The details of grading criteria are described in the main text. The red boxed areas are magnified and put beneath each grade photograph. The inter-crystal spaces of each magnified photograph were painted in orange and represented by the black boxed areas on the lower left corner. The red arrows in grades 0, 3 and 3.5 are indicated by the snowflake, the cross shape, and the square-like patterns, respectively. The red triangles in grade 0.5, the blue triangles in grade 1, and the yellow triangles in grade 1.5 indicated the trunk crystals from finer to coarser, as the grade scales were increased. The red right angle marks in grade 2 indicated the intersection of TF crystals at the right angle. All the original photographs were magnified at 100×.
Statistical Analysis
The data are presented as the means ± standard error of the mean (SEM) and compared with the Mann-Whitney U test. The Pearson correlation was used to depict the relationship among the obtained data. Correlation coefficients was considered very weak (0.00–0.19), weak (0.20–0.39), moderate (0.40–0.59), strong (0.60–0.79), and very strong (0.80–1.00). All statistical analyses were performed by using GraphPad Prism 9 software (GraphPad Software, San Diego, CA). 
Results
Effects of UVB on TV and TBUT
To investigate TV and TBUT after UVB exposure for 10 days, the tear strip test and fluorescein instillation were performed. The results showed that the TV was significantly reduced in the damage group, and there was no significant difference in the blank group after 10 days (Fig. 2A). Similarly, the TBUT in the damage group decreased significantly, in contrast to the no difference in the blank group after 10 days (Fig. 2B). 
Figure 2.
 
The tear volume (TV) and tear film break-up time (TBUT) on days 0 and 11 with or without UVB damage. mm, millimeter; sec, second; ns, nonsignificant. **** P < 0.0001, by the Mann-Whitney U test; n = 12 for both the blank and the damage groups.
Figure 2.
 
The tear volume (TV) and tear film break-up time (TBUT) on days 0 and 11 with or without UVB damage. mm, millimeter; sec, second; ns, nonsignificant. **** P < 0.0001, by the Mann-Whitney U test; n = 12 for both the blank and the damage groups.
Effects of UVB on Corneal Staining
The damage to the ocular surface was assessed by cornea staining using lissamine green. Severe opacity was found in the UVB-damaged cornea on day 11, after 10 days of UVB exposure (compare Figs. 3B and Fig. 3D). The grade of cornea staining was significantly higher in the damage group compared with that of the blank group (Table 1). 
Figure 3.
 
Representative photographs of cornea lissamine green stain on days 0 and 12. (A, B) Without UVB damage; (C, D) with UVB damage.
Figure 3.
 
Representative photographs of cornea lissamine green stain on days 0 and 12. (A, B) Without UVB damage; (C, D) with UVB damage.
Table 1.
 
The Average of Cornea Stain Grades on Days 0 and 12, With (Damage) and Without (Blank) UVB Exposure
Table 1.
 
The Average of Cornea Stain Grades on Days 0 and 12, With (Damage) and Without (Blank) UVB Exposure
Effect of UVB on TF Patterns
The TF results of the damage and the blank groups on days 0, 5, and 10 were compared (Fig. 4). On day 5 after UVB exposure, the TF pattern showed more coarse trunks and non-crystal spaces in the damage group (Fig. 4E) compared to that of the blank group (Figs. 4A, 4B, 4C) and that before UVB damage on day 0 (Fig. 4D). On day 10 after UVB exposure, the TF pattern was significantly scattered and with short crystal formation that was square-like in shape (Fig. 3F). Moreover, even more non-crystal spaces could be observed in the TF pattern after 10 days of UVB exposure. However, the TF test results from the blank group on days 0, 5, and 10 showed dense snowflake patterns without non-crystal spaces (see Figs. 4A, 4B, 4C). No difference was observed in the blank group on different days. A trend of less TF formation was observed after UVB exposure (compare Figs. 4D with Fig. 4E and Fig. 4F). 
Figure 4.
 
TF patterns on days 0 (A, D), 5 (B, E), and 10 (C, F), respectively. A, B, and C, without UVB damage; D, E, and F, with UVB damage. The red boxed areas are magnified and presented on the lower right corner of each photograph to show the specific characteristics of TF patterns. All original photographs were taken at 100× magnification.
Figure 4.
 
TF patterns on days 0 (A, D), 5 (B, E), and 10 (C, F), respectively. A, B, and C, without UVB damage; D, E, and F, with UVB damage. The red boxed areas are magnified and presented on the lower right corner of each photograph to show the specific characteristics of TF patterns. All original photographs were taken at 100× magnification.
Relatively Early TF Detection of UVB-Induced Photokeratitis by SK Grading
The TF grades using both grading criteria were increased along with the days of experiment except for the blank group (Fig. 5). To determine which set of TF grading criteria is more suitable for early photokeratitis diagnosis in the mouse model, the SK and the Masmali grading criteria were compared. Using the SK grading criteria, the TF results increased from an average grade of 1.42 (SEM ± 0.18) before UVB exposure to 2.13 (SEM ± 0.18) after 3 days of UVB exposure. After 10 days, the average TF grade increased to 2.83 (SEM ± 0.11). A significant difference in TF grades was found between the blank and the damage groups as early as on day 3 (P < 0.01; Table 2). In contrast, by using the Masmali grading criteria, the average of TF grades was only slightly increased from 1.25 (SEM ± 0.13) to 1.67 (SEM ± 0.14) after 3 days of UVB exposure. The TF tests revealed no significant differences between the blank and the damage groups on day 3 by using the Masmali criteria. 
Figure 5.
 
Tear ferning (TF) gradings by (A) the Sophie-Kevin (SK) and (B) the Masmali grading criteria. The SK grading displayed significant difference between the blank and the damage groups on day 3, one day earlier than the Masmali grading. **P < 0.01; ***P < 0.001; ****P < 0.0001; n = 12 for both the blank and the damage groups; all statistics were performed by the Mann-Whitney U test.
Figure 5.
 
Tear ferning (TF) gradings by (A) the Sophie-Kevin (SK) and (B) the Masmali grading criteria. The SK grading displayed significant difference between the blank and the damage groups on day 3, one day earlier than the Masmali grading. **P < 0.01; ***P < 0.001; ****P < 0.0001; n = 12 for both the blank and the damage groups; all statistics were performed by the Mann-Whitney U test.
Table 2.
 
The Average Tear Ferning (TF) Grades by the Sophie-Kevin (SK) and the Masmali Grading Criteria on Days 0, 3, 4, 5, 7, 9, and 10, With (Damage) or Without (Blank) UVB Exposure
Table 2.
 
The Average Tear Ferning (TF) Grades by the Sophie-Kevin (SK) and the Masmali Grading Criteria on Days 0, 3, 4, 5, 7, 9, and 10, With (Damage) or Without (Blank) UVB Exposure
Correlation Between TF Test and Other Ocular Surface Indicators
Because the SK grading was found to be more sensitive for early diagnosis, the test results were further correlated with other ocular surface indicators, including TV, TBUT, and cornea staining (Fig. 6). In all the study groups, the negative correlation between the TF test and the TV test was strong (r = −0.702, P = 0.0001; see Fig. 6A). A very strong negative correlation (r = −0.878, P < 0.0001) between the TF test and the TBUT was also observed (see Fig. 6B). Furthermore, a very strong positive correlation (r = 0.887, P < 0.0001) between the TF test and the cornea stain was also found (see Fig. 6C). 
Figure 6.
 
The correlation of tear ferning (TF) results by the Sophie-Kevin (SK) grading criteria with tear volume (TV), tear film break-up time (TBUT), and cornea stain. mm, millimeter. sec, second; (A) r = −0.702, P = 0.0001; (B) r = −0.878, P < 0.0001; (C) r = 0.887, P < 0.0001; n = 12 for both the blank and the damage groups; all the statistics were performed by Pearson r test.
Figure 6.
 
The correlation of tear ferning (TF) results by the Sophie-Kevin (SK) grading criteria with tear volume (TV), tear film break-up time (TBUT), and cornea stain. mm, millimeter. sec, second; (A) r = −0.702, P = 0.0001; (B) r = −0.878, P < 0.0001; (C) r = 0.887, P < 0.0001; n = 12 for both the blank and the damage groups; all the statistics were performed by Pearson r test.
Discussion
In this study, the TF test was investigated for its capacity to distinguish between normal and early photokeratitis status in a mouse UVB-induced model. With photokeratitis, although both the Masmali and the SK criteria could distinguish the damage from the blank groups after 4 days, the SK criteria could decern the damage group on day 3. This capacity of earlier detection would render the SK criteria more helpful than the Masmali grading if the TF test is used in the clinical settings. This advantage of the SK criteria is likely due to that the subtler changes can be reflected. However, this advantage cannot be generalized that TF can show early changes than those reflected by TBUT and TV, simply because the latter two measurements were conducted at a later time in our experimental design. 
To further verify the TF test as a reliable method for early photokeratitis diagnosis, we correlated the TF results with other commonly used clinical ocular surface parameters. The TF test showed strong correlations with TV, TBUT, and cornea staining, indicating that the TF test may provide a general view of all the three indicators under the photokeratitis status. Besides, the TF test correlation with TBUT was stronger than with TV, suggesting that the TF test can reflect more about tear quality than quantity. The insight of this finding would be a potential use of TF to reflect the important component within the tear. For example, cornea damage may be due to loss of lactoferrin, which is a significant component of the tear film and plays an important role in maintaining ocular surface health.26 Reduced lactoferrin levels in the tears may contribute to tear film instability and may alter the TF formation. Another potential use of TF may be to correlate with cornea staining for confirmation of ocular surface status, particularly at early stages when the staining remains not evident. In the present study, our data showed a very strong positive correlation between lissamine green staining and TF grading, supporting the use of TF for the evaluation of corneal epithelial injuries. However, to bring the TF test into clinical settings, human clinical trials are mandatory to confirm its applicability as an earlier indicator for photokeratitis. 
Differential diagnosis among ocular surface diseases is critical for clinical management. For example, early photokeratitis and dry eye share some common symptoms such as tearing, itchy sensation, and ocular surface redness and swelling. In addition, allergic conjunctivitis shares similar symptoms at the early stage,27 which is a challenge for differential diagnosis. Incorrect management for these diseases, for example, between dry eye and allergic conjunctivitis at early stages, may lead to worsen the pathogenetic aftermath.28 Nevertheless, the commonly used assessments, such as TBUT and Schirmer's test, have been shown only weakly correlated with signs and symptoms.16,17 Other assessments, such as in vivo confocal microscopy (IVCM) and osmolarity test,29 demand substantial time, expensive instruments, or personnel skills for completion. Therefore, a quick, easy to perform, reproducible, and cost-effective measurement for early and preferentially differential diagnosis would be more acceptable in clinical settings. We hypothesize that different ocular surface disorders may have their characteristic tear composition, and therefore may display differential TF results. In this regard, the TF test may offer another option for ocular surface diagnosis. 
In conclusion, the present study has demonstrated the use of the TF test for early diagnosis of photokeratitis, particularly by using the SK grading criteria. Furthermore, because the TF test can generally reflect the results of TV, TBUT, and cornea staining, and can be easily performed, it may be used as a primary test for mass screening of ocular surface diseases. 
Acknowledgments
Supported by a research grant MOST 110-2320-B-040-022 from the Ministry of Science and Technology, Taiwan to David P.-C. Lin. 
Disclosure K.K.-W. Chen, None; S.M.-T. Hsieh, None; H.-H. Chang, None; D.P.-C. Lin, None 
References
Ivanov IV, Mappes T, Schaupp P, Lappe C, Wahl S. Ultraviolet radiation oxidative stress affects eye health. J Biophotonics. 2018; 11(7): e201700377. [CrossRef]
Hunter JJ, Morgan JI, Merigan WH, et al. The susceptibility of the retina to photochemical damage from visible light. Prog Retin Eye Res. 2012; 31(1): 28–42. [CrossRef]
Wakamatsu TH, Dogru M, Tsubota K. Tearful relations: oxidative stress, inflammation and eye diseases. Arquivos brasileiros de oftalmologia. 2008; 71: 72–79. [CrossRef]
Choy CKM, Cho P, Benzie IF. Antioxidant content and ultraviolet absorption characteristics of human tears. Optom Vis Sci. 2011; 88(4): 507–511. [CrossRef]
Cadet J, Douki T, Ravanat JL. Oxidatively generated damage to cellular DNA by UVB and UVA radiation. Photochem Photobiol. 2015; 91(1): 140–155. [CrossRef]
Delic NC, Lyons JG, Di Girolamo N, Halliday GM. Damaging effects of ultraviolet radiation on the cornea. Photochem Photobiol. 2017; 93(4): 920–929. [CrossRef]
Izadi M, Jonaidi-Jafari N, Pourazizi M, Alemzadeh-Ansari MH, Hoseinpourfard MJ. Photokeratitis induced by ultraviolet radiation in travelers: a major health problem. J Postgrad Med. 2018; 64(1): 40–46.
Cullen AP. Ozone depletion and solar ultraviolet radiation: ocular effects, a United Nations environment programme perspective. Eye Contact Lens. 2011; 37(4): 185–190. [CrossRef]
Kolozsvári L, Nógrádi A, Hopp B, Bor Z. UV absorbance of the human cornea in the 240-to 400-nm range. Invest Ophthalmol Vis Sci. 2002; 43(7): 2165–2168.
Lan W, Petznick A, Heryati S, Rifada M, Tong L. Nuclear Factor-κB: central regulator in ocular surface inflammation and diseases. Ocul Surf. 2012; 10(3): 137–148. [CrossRef]
Jamerson EC, Elhusseiny AM, ElSheikh RH, Eleiwa TK, El Sayed YM. Role of matrix metalloproteinase 9 in ocular surface disorders. Eye Contact Lens. 2020; 46(Suppl 2): S57–S63.
Lin DP, Chang HH, Yang LC, et al. Assessment of ultraviolet B-blocking effects of weekly disposable contact lenses on corneal surface in a mouse model. Mol Vis. 2013; 19: 1158–1168.
Bron A, Tiffany J, Gouveia S, Yokoi N, Voon L. Functional aspects of the tear film lipid layer. Exp Eye Res. 2004; 78(3): 347–360. [CrossRef]
Pescosolido N, Imperatrice B, Koverech A, Messano M. L-carnitine and short chain ester in tears from patients with dry eye. Optom Vis Sci. 2009; 86(2): E132–E138. [CrossRef]
Messmer EM. The pathophysiology, diagnosis, and treatment of dry eye disease. Dtsch Arztebl Int. 2015; 112(5): 71–81; quiz 82.
Nichols KK, Nichols JJ, Mitchell GL. The lack of association between signs and symptoms in patients with dry eye disease. Cornea. 2004; 23(8): 762–770. [CrossRef]
Hay EM, Thomas E, Pal B, et al. Weak association between subjective symptoms of and objective testing for dry eyes and dry mouth: results from a population based study. Ann Rheum Dis. 1998; 57(1): 20–24. [CrossRef]
Nagy ZZ, Hiscott P, Seitz B, et al. Clinical and morphological response to UV-B irradiation after excimer laser photorefractive keratectomy. Surv Ophthalmol. 1997; 42: S64–S76. [CrossRef]
Masmali AM, Purslow C, Murphy PJ. The tear ferning test: a simple clinical technique to evaluate the ocular tear film. Clin Exp Optom. 2014; 97(5): 399–406. [CrossRef]
Masmali AM, Sultan A-Q, Al-Gasham TM, et al. Application of a new grading scale for tear ferning in non-dry eye and dry eye subjects. Cont Lens Anterior Eye. 2015; 38(1): 39–43. [CrossRef]
Masmali AM, Murphy PJ, Purslow C. Development of a new grading scale for tear ferning. Cont Lens Anterior Eye. 2014; 37(3): 178–184. [CrossRef]
Tang YJ, Chang HH, Tsai CY, Chen LY, Lin DP. Establishment of a tear ferning test protocol in the mouse model. Transl Vis Sci Technol. 2020; 9(13): 1. [CrossRef]
Song X, Zhao P, Wang G, Zhao X. The effects of estrogen and androgen on tear secretion and matrix metalloproteinase-2 expression in lacrimal glands of ovariectomized rats. Invest Ophthalmol Vis Sci. 2014; 55(2): 745–751. [CrossRef]
Tang Y-J, Chang H-H, Chiang C-Y, et al. A murine model of acute allergic conjunctivitis induced by continuous exposure to particulate matter 2.5. Invest Ophthalmol Vis Sci. 2019; 60(6): 2118–2126. [CrossRef]
Wolffsohn JS, Arita R, Chalmers R, et al. TFOS DEWS II Diagnostic Methodology report. Ocul Surf. 2017; 15(3): 539–574. [CrossRef]
Flanagan JL, Willcox MDP. Role of lactoferrin in the tear film. Biochimie. 2009; 91(1): 35–43. [CrossRef]
Leonardi A, Modugno RL, Salami E. Allergy and dry eye disease. Ocul Immunol Inflamm. 2021; 29(6): 1168–1176. [CrossRef]
Messmer EM. The pathophysiology, diagnosis, and treatment of dry eye disease. Deutsches Ärzteblatt International. 2015; 112(5): 71.
Tashbayev B, Utheim TP, Utheim ØA, et al. Utility of tear osmolarity measurement in diagnosis of dry eye disease. Sci Rep. 2020; 10(1): 5542. [CrossRef]
Figure 1.
 
Demonstration of the SK grading criteria for mouse TF. The details of grading criteria are described in the main text. The red boxed areas are magnified and put beneath each grade photograph. The inter-crystal spaces of each magnified photograph were painted in orange and represented by the black boxed areas on the lower left corner. The red arrows in grades 0, 3 and 3.5 are indicated by the snowflake, the cross shape, and the square-like patterns, respectively. The red triangles in grade 0.5, the blue triangles in grade 1, and the yellow triangles in grade 1.5 indicated the trunk crystals from finer to coarser, as the grade scales were increased. The red right angle marks in grade 2 indicated the intersection of TF crystals at the right angle. All the original photographs were magnified at 100×.
Figure 1.
 
Demonstration of the SK grading criteria for mouse TF. The details of grading criteria are described in the main text. The red boxed areas are magnified and put beneath each grade photograph. The inter-crystal spaces of each magnified photograph were painted in orange and represented by the black boxed areas on the lower left corner. The red arrows in grades 0, 3 and 3.5 are indicated by the snowflake, the cross shape, and the square-like patterns, respectively. The red triangles in grade 0.5, the blue triangles in grade 1, and the yellow triangles in grade 1.5 indicated the trunk crystals from finer to coarser, as the grade scales were increased. The red right angle marks in grade 2 indicated the intersection of TF crystals at the right angle. All the original photographs were magnified at 100×.
Figure 2.
 
The tear volume (TV) and tear film break-up time (TBUT) on days 0 and 11 with or without UVB damage. mm, millimeter; sec, second; ns, nonsignificant. **** P < 0.0001, by the Mann-Whitney U test; n = 12 for both the blank and the damage groups.
Figure 2.
 
The tear volume (TV) and tear film break-up time (TBUT) on days 0 and 11 with or without UVB damage. mm, millimeter; sec, second; ns, nonsignificant. **** P < 0.0001, by the Mann-Whitney U test; n = 12 for both the blank and the damage groups.
Figure 3.
 
Representative photographs of cornea lissamine green stain on days 0 and 12. (A, B) Without UVB damage; (C, D) with UVB damage.
Figure 3.
 
Representative photographs of cornea lissamine green stain on days 0 and 12. (A, B) Without UVB damage; (C, D) with UVB damage.
Figure 4.
 
TF patterns on days 0 (A, D), 5 (B, E), and 10 (C, F), respectively. A, B, and C, without UVB damage; D, E, and F, with UVB damage. The red boxed areas are magnified and presented on the lower right corner of each photograph to show the specific characteristics of TF patterns. All original photographs were taken at 100× magnification.
Figure 4.
 
TF patterns on days 0 (A, D), 5 (B, E), and 10 (C, F), respectively. A, B, and C, without UVB damage; D, E, and F, with UVB damage. The red boxed areas are magnified and presented on the lower right corner of each photograph to show the specific characteristics of TF patterns. All original photographs were taken at 100× magnification.
Figure 5.
 
Tear ferning (TF) gradings by (A) the Sophie-Kevin (SK) and (B) the Masmali grading criteria. The SK grading displayed significant difference between the blank and the damage groups on day 3, one day earlier than the Masmali grading. **P < 0.01; ***P < 0.001; ****P < 0.0001; n = 12 for both the blank and the damage groups; all statistics were performed by the Mann-Whitney U test.
Figure 5.
 
Tear ferning (TF) gradings by (A) the Sophie-Kevin (SK) and (B) the Masmali grading criteria. The SK grading displayed significant difference between the blank and the damage groups on day 3, one day earlier than the Masmali grading. **P < 0.01; ***P < 0.001; ****P < 0.0001; n = 12 for both the blank and the damage groups; all statistics were performed by the Mann-Whitney U test.
Figure 6.
 
The correlation of tear ferning (TF) results by the Sophie-Kevin (SK) grading criteria with tear volume (TV), tear film break-up time (TBUT), and cornea stain. mm, millimeter. sec, second; (A) r = −0.702, P = 0.0001; (B) r = −0.878, P < 0.0001; (C) r = 0.887, P < 0.0001; n = 12 for both the blank and the damage groups; all the statistics were performed by Pearson r test.
Figure 6.
 
The correlation of tear ferning (TF) results by the Sophie-Kevin (SK) grading criteria with tear volume (TV), tear film break-up time (TBUT), and cornea stain. mm, millimeter. sec, second; (A) r = −0.702, P = 0.0001; (B) r = −0.878, P < 0.0001; (C) r = 0.887, P < 0.0001; n = 12 for both the blank and the damage groups; all the statistics were performed by Pearson r test.
Table 1.
 
The Average of Cornea Stain Grades on Days 0 and 12, With (Damage) and Without (Blank) UVB Exposure
Table 1.
 
The Average of Cornea Stain Grades on Days 0 and 12, With (Damage) and Without (Blank) UVB Exposure
Table 2.
 
The Average Tear Ferning (TF) Grades by the Sophie-Kevin (SK) and the Masmali Grading Criteria on Days 0, 3, 4, 5, 7, 9, and 10, With (Damage) or Without (Blank) UVB Exposure
Table 2.
 
The Average Tear Ferning (TF) Grades by the Sophie-Kevin (SK) and the Masmali Grading Criteria on Days 0, 3, 4, 5, 7, 9, and 10, With (Damage) or Without (Blank) UVB Exposure
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