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ORIGINAL ARTICLE
Year : 2021  |  Volume : 28  |  Issue : 3  |  Page : 169-173  

Prevalence of color vision anomalies among dental professionals


1 Consultant Oral and Maxillofacial Surgeon, Trinity Hospital, Silaimual, Melthum, Aizawl, Mizoram, India
2 Department of Orthodontics and Dentofacial Orthopaedics, Meghna Institute of Dental Sciences, Nizamabad, Telangana, India
3 Consultant Orthodontist, Madurai, Tamil Nadu, India
4 Department of Prosthodontics and Crown and Bridge, The KLE Academy of Higher Education and Research, KLE V.K. Institute of Dental Sciences and Hospital, Belgaum, Karnataka, India
5 Department of Prosthodontics and Crown and Bridge, RVS Dental College and Hospital, Coimbatore, Tamil Nadu, India
6 Department of Conservative Dentistry and Endodontics, RVS Dental College and Hospital, Coimbatore, Tamil Nadu, India
7 Department of Preventive Dental Sciences, Division of Periodontology, College of Dentistry, University of Ha'il, Ha'il, Kingdom of Saudi Arabia
8 Department of Oral Medicine and Radiology, Saraswati Dhanwantari Dental College and Hospital and Post-graduate Research Institute, Parbhani, Maharashtra, India

Date of Submission10-Dec-2020
Date of Acceptance15-Nov-2021
Date of Web Publication31-Dec-2021

Correspondence Address:
Dr. Abhishek Singh Nayyar
Department of Oral Medicine and Radiology, Saraswati Dhanwantari Dental College and Hospital and Post-graduate Research Institute, Parbhani, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/meajo.meajo_529_20

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   Abstract 


PURPOSE: Color blindness is one of the potential disabilities affecting the ability of color perception by the eye. The aim of the present study was to evaluate the prevalence of color blindness among dental professionals.
METHODS: For the present study, a total of 198 dental professionals were randomly selected as subjects who were asked to fill the required questionnaire followed by which their color vision status was evaluated using the Ishihara test. The results obtained were subjected to statistical analysis. Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) version 17.0 (SPSS Inc., Chicago, IL, USA). The prevalence of color blindness, age specificity, and the ratio of the occurrence of color blindness in relation to gender were assessed using Chi-square test for independence and Chi-square test with Yates's correction for independence when the expected frequency was <5. P < 0.05 was considered statistically significant.
RESULTS: The present study reported 3.54% prevalence of color blindness among the study population. A higher number of cases were reported from males (9.26%) than females (1.39%). (P < 0.05) Furthermore, the prevalence of color blindness was found to be more in faculty members (5.88%) than in students with a reported prevalence of 3.31%.
CONCLUSION: The present study reported high prevalence of color blindness in dental professionals while they were totally unaware of it.

Keywords: Color vision anomalies, dental professionals, Ishihara test


How to cite this article:
Ngente Z, Jadav B, Aafaque S, Patil A, Govindarajulu R, Muthusamy P, Babu J S, Swarnalatha C, Nayyar AS. Prevalence of color vision anomalies among dental professionals. Middle East Afr J Ophthalmol 2021;28:169-73

How to cite this URL:
Ngente Z, Jadav B, Aafaque S, Patil A, Govindarajulu R, Muthusamy P, Babu J S, Swarnalatha C, Nayyar AS. Prevalence of color vision anomalies among dental professionals. Middle East Afr J Ophthalmol [serial online] 2021 [cited 2022 Jul 4];28:169-73. Available from: http://www.meajo.org/text.asp?2021/28/3/169/334631




   Introduction Top


Esthetics plays a vital role in achieving patient satisfaction in restorative and prosthetic dental procedures.[1],[2],[3],[4] The demand of high esthetic outcomes is achieved through the production of an acceptable morphology and shade reproduction in a restoration.[5],[6],[7],[8] The success of the currently available esthetic restorative dental materials depends on correct shade matching while the perception of color is a complex process which depends on various factors. The ability to match the shade of a required prosthesis to that of the adjacent natural teeth is an important goal of restorative dental procedures.[9],[10],[11],[12],[13] Color vision defect affects the ability of shade matching as a defect in color vision may lead to difficulty in the perception of color.[14],[15] Color blindness, in its congenital form, is the product of genetic mutations that affects the expression of the three types of cone cells present in the eye that respond differently to light of different wavelengths. In its genetic form, color blindness is seen as a common vision disorder, especially, seen in males (gene defect arises on the X chromosome within the Xq28 band).[16],[17] Cone cells present in the eye are actually photoreceptor cells present in the retina of vertebrate eyes including the human eye. These cone cells respond differently to light of different wavelengths and are, thus, responsible for color vision. Cone cells are densely packed in the fovea centralis of the eye which is a 0.3 mm diameter area with very thin, densely packed cells which quickly reduce in number toward the periphery of the retina. Conversely, cone cells are considered to be absent from the optic disc contributing to the so-recognized, blind spot.[16],[18] There is evidence to suggest that color vision is integral to a number of dental specialties, particularly, restorative and prosthetic dentistry.[19],[20],[21],[22],[23],[24] Identifying and informing dental professionals with color blindness should, thus, allow the personnel to receive the necessary support and training to pursue a successful career. The present study was conducted to evaluate the prevalence of color blindness in dental professionals to make them aware about their anomaly, if, it existed and to create awareness about this type of professional limitation which can put a serious hurdle in a successful career in restorative and prosthetic dentistry.


   Methods Top


The present observational study was conducted in a cross-sectional study design to evaluate the prevalence of color blindness in dental professionals. The sampling frame in the present study included a total of 198 dental professionals including 181 dental students and 17 faculty members who were randomly selected as study subjects for the present study. The sampling technique used in the present study was simple random sampling with random number method used for carrying-out randomization. Ethical clearance for the conduct of the study was duly obtained from the Institutional Ethics Committee before the start of the study. The subjects included were informed about the need for the study and written, informed consent was obtained from each subject to participate in the study. The present study was designed as a questionnaire-based survey wherein each subject was asked to fill a questionnaire containing information about age, gender, and designation followed by which color vision status of each subject was evaluated using the Ishihara test [Figure 1]. Six color plates were shown to each subject in-person while the subjects were asked to detect the numbers in the color plates and write them in the questionnaire provided. The questionnaires were, then, evaluated and the data obtained was subjected to statistical analysis. All standard instructions for the test were followed in the present study while those who were detected color blind in the test were re-assessed by advanced examination using 17 color plates to confirm the results.
Figure 1: Ishihara chart for color blindness test

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Statistical analysis

Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) version 17.0 (SPSS Inc., Chicago, IL, USA). The prevalence of color blindness, age specificity, and the ratio of the occurrence of color blindness in relation to gender were assessed using the Chi-square test for independence and Chi-square test with Yates's correction for independence when the expected frequency was <5. P < 0.05 was considered statistically significant.


   Results Top


The prevalence of color blindness in the total sample studied was found to be around 3.54%. Among these, maximum numbers of color-blind cases were reported in the 17–21 years age group, though, a general trend for increase in the probability of color blindness could be seen with increasing age with 2 out of merely 16 cases in the 27–31 years age group found to be color blind than as compared to 17–21 years and 22–26 years age groups wherein 3 and 2 cases, respectively, were found to be color blind in a total of 104 and 73 cases. The overall prevalence of color blindness, thus, was reported at 12.50% in the 27–31 years age group as against 17–21 years and 22–26 years age groups, wherein the recorded prevalence was calculated at 2.88% and 2.74%, respectively [Table 1]. Furthermore, the prevalence of color blindness was found to be more in males with 5 out of 54 (9.26%) cases being affected with the anomaly as against females wherein only 2 out of 144 (1.39%) cases were found to be color blind with the results being statistically significant (P < 0.05) [Table 2]. Again, 1 out of the 17 faculty members was found to be color blind as against the students, wherein 6 out of 181 subjects were found to be color blind with a reported prevalence of 5.88% and 3.31%, respectively [Table 3].
Table 1: Color vision status according to age group distribution of entire sample

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Table 2: Color vision status according to gender distribution

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Table 3: Color vision status according to the designation

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   Discussion Top


Vision is a psycho-physical phenomenon based on the sensitivity of cone cells in the retina to wavelengths between 400 and 700 nm of the electromagnetic spectrum. There are about 6–7 million cone cells in a human eye which are mostly concentrated toward the macula. These cells are less sensitive to light than the rod cells in the retina which support vision at low light levels, though, allow the perception of color. They are, also, able to perceive finer details and more rapid changes in images because their response times to stimuli are faster than the rod cells.[16],[17],[18] Cone cells are normally of three types with each type of cell sensitive to wavelengths of light that correspond to short-, medium- and longer-wavelength light.[17] Since the human eye usually has three kinds of cone cells with different light receptive pigments or, proteins which are called photopsins with different response curves and thus, response to variation in color, the human eye is said to have trichromatic vision. These three pigments, responsible for detecting light, have been shown to vary in their exact chemical composition due to genetic influences, and thus, different individuals have cone cells which have different color sensitivity.[25] Furthermore, since there are three types of cone cells in the eye responsible for spectral sensitivity for color perception when a single type of color receptive cone cells are missing from the eye, the person is unable to distinguish between colors and is said to have color blindness. A person with a loss of red cones is called a protanope and in such a case, the overall visual spectrum is noticeably shortened near the longer wavelength end because of a lack of red cones. Similarly, a person who lacks green cones is called a deuteranope while this person has an almost normal visual spectral width because red cones are available to detect the longer wavelength end. In similar lines, it has been observed that red-green color blindness is a genetic disorder that occurs almost exclusively in males and is rare in occurrence, though, blue-yellow type of color blindness, another related variant, also, called tritanopia, is an extremely rare condition.[18],[25],[26] The most commonly used tests for color vision deficiencies are the Ishihara plates used for detecting red-green deficits and the Richmond Hardy, Rand, and Rittler plates used for detecting blue-yellow (tritan) deficiencies while, also, being suitable for acquired color vision defects.[27],[28],[29],[30] As blue-yellow deficiencies are extremely rare, the Ishihara test was employed in the present study. The series of Ishihara color plates are designed to give a quick and accurate assessment of color vision deficiencies of congenital origin in the red-green region. The full Ishihara test consists of 38 plates. Only 6 plates were used in the present study since it is not necessary in all cases to use the whole series of plates. For screening purposes or, in a large scale examination, the test may be simplified to an examination of 6 plates only including No. 1, one of No.s 2, 3, one of No.s 4-7, one of No.s 8, 9, one of No.s 10-13, and one of No.s 14, 15. Furthermore, it may be necessary to vary the order of the plates as per the need if it is suspected that there is a deliberate deception on part of the subject.[31],[32] Furthermore, deuteranopia is a relative color blindness for specific types of cone cells that is detected or, rather, suggested by the test. In the assessment of color vision status using the 6 plates short test, a normal reading for all the plates is required to suggest normal color vision status. In case of a discrepancy, an extended series of tests including more number of test plates like 17 plates or, the full series of plates is used before diagnosing a color vision defect.[33],[34],[35] Furthermore, a significant point to be noted in this regard is that the ability to grade the severity of color vision defects is limited and results from such tests cannot yet be used as a basis for deciding on the severity of color vision defect.[36] Numerous studies have shown that color vision defects are common among dental professionals and do affect their abilities.[37],[38],[39] The results of the present study were found to be in close accordance with the findings of the study conducted by Moser et al.[37] who conducted a similar study on 670 professionals and found 66 (9.95%) professionals to be color blind. Similarly, Bamise et al.[14] recorded a 6.3% prevalence of color blindness amongst Nigerian dental practitioners with the prevalence being higher in males (8.4%) than in females (3.9%). Barghi et al.,[19] also, found 7 out of 50 individuals to be color blind in their study while Wasson and Schuman[20] found 9.3% of the population presenting with color blindness in their study with the males being affected more than females signifying the sex-linked nature of this condition analogous with the findings of the present study. A recent study by Alqahtani et al.,[40] also, observed a total of 20.19% of male dental students to be affected with red-green color vision deficiency as compared to 1.4% of female students with 44 male and 3 female students identified with red-green color deficiency out of a total sample size of 203 students included in the study. The frequency of total color vision deficiency observed in the study was found to be 3.9%. A meta-analysis published by Birch[41] including large random population surveys revealed the prevalence of color vision deficiency in European Caucasians to be about 8% in men and 0.4% in women while between 4% and 6.5% in men of Chinese and Japanese ethnicity. Furthermore, another notable finding of the meta-analysis published was that the male: female prevalence ratio was markedly different in Europeans and Asians, thus, suggesting founder events and genetic drift, rather than natural selection, to be the major factors behind these differences. To note, the present study had reported a 3.54% prevalence of color blindness with record higher number of cases reported from males (9.26%) than females (1.39%) (P < 0.05). Deuteranopia is a type of red-green color blindness characterized by the inability to distinguish red and green pigments. Deuteranopia is inherited as an X-linked recessive trait, affecting predominantly males. The genes responsible for leading to red-green color blindness are passed down on the X chromosome, thus, manifesting the color vision defect more commonly in males than females.[31],[32],[42],[43],[44],[45],[46],[47] Color perception plays an important role in the dental profession, though, unfortunately, not many of the professionals are aware of this limitation. The purpose of the present study was to create awareness about this type of compromise among dental professionals. There is no known cure for color blindness. Contact lenses and glasses with filters may be advisable to help color deficiencies or, improve color perception. Fortunately, the vision of most color blind people is normal in all other respects and certain adaptation methods are all that is required.[48],[49]


   Conclusion Top


Since esthetics plays a significant role in the successful practice of restorative and prosthetic dentistry, dental professionals should always be concerned regarding esthetics along with the treatment of disease. The present study reported a high prevalence of color blindness in dental professionals included in the study while they were totally unaware of it which is not unusual due to a general lack of awareness about this type of anomaly. Most of the times, dental professionals remain unaware of this type of compromise and it becomes tricky to identify such a compromise existing. At the time of selection in course, a full body check-up is mandatory, but this excludes color vision test. The governing body should pay more attention and must take proper measures in improvising the benchmark criteria during counseling/selection procedures to courses where esthetics are a cause of concern. The present study, thus, concluded that prevalence of color blindness/color vision defect/deficiency among dental professionals was high enough with males having a higher frequency as compared to females, thus, mandating further studies and research in this regard on larger population sizes including subjects from different race, regions, and ethnicity in determining the actual data of its prevalence and its impact on the professional abilities.

Acknowledgments

To all the patients who contributed to the study without whom this study would not have been feasible.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Fondriest J. Shade matching in restorative dentistry: The science and strategies. Int J Periodontics Restorative Dent 2003;23:467-79.  Back to cited text no. 1
    
2.
Qualtrough AJ, Burke FJ. A look at dental esthetics. Quintessence Int 1994;25:7-14.  Back to cited text no. 2
    
3.
Miller L. Organizing color in dentistry. J Am Dent Assoc 1987;Spec No: E26-40.  Back to cited text no. 3
    
4.
Samorodnitzky-Naveh GR, Geiger SB, Levin L. Patients' satisfaction with dental esthetics. J Am Dent Assoc 2007;138:805-8.  Back to cited text no. 4
    
5.
Akarslan ZZ, Sadik B, Erten H, Karabulut E. Dental esthetic satisfaction, received and desired dental treatments for improvement of esthetics. Indian J Dent Res 2009;20:195-200.  Back to cited text no. 5
[PUBMED]  [Full text]  
6.
Tin-Oo MM, Saddki N, Hassan N. Factors influencing patient satisfaction with dental appearance and treatments they desire to improve aesthetics. BMC Oral Health 2011;11:6.  Back to cited text no. 6
    
7.
Maghaireh GA, Alzraikat H, Taha NA. Satisfaction with dental appearance and attitude toward improving dental esthetics among patients attending a dental teaching center. J Contemp Dent Pract 2016;17:16-21.  Back to cited text no. 7
    
8.
Grzić R, Spalj S, Lajnert V, Glavicić S, Uhac I, Pavicić DK. Factors influencing a patient's decision to choose the type of treatment to improve dental esthetics. Vojnosanit Pregl 2012;69:978-85.  Back to cited text no. 8
    
9.
Hall NR. Tooth colour selection: The application of colour science to dental colour matching. Aust Prosthodont J 1991;5:41-6.  Back to cited text no. 9
    
10.
Miller LL. Shade matching. J Esthet Dent 1993;5:143-53.  Back to cited text no. 10
    
11.
Sproull RC. Color matching in dentistry. I. The three-dimensional nature of color. J Prosthet Dent 1973;29:416-24.  Back to cited text no. 11
    
12.
Small BW. Shade selection for restorative dentistry. Gen Dent 2006;54:166-7.  Back to cited text no. 12
    
13.
Heymann HO. The artistry of conservative esthetic dentistry. J Am Dent Assoc 1987;Spec No.:E14-23.  Back to cited text no. 13
    
14.
Bamise CT, Esan TA, Akeredolu PA, Oluwatoyin O, Oziegbe EO. Color vision defect and tooth shade selection amongst Nigerian dental practitioners. Rev Clín Pesq Odontol 2007;3:175-82.  Back to cited text no. 14
    
15.
Poljak-Guberina R, Celebic A, Powers JM, Paravina RD. Colour discrimination of dental professionals and colour deficient laypersons. J Dent 2011;39:e17-22.  Back to cited text no. 15
    
16.
Kandel ER, Schwartz JH, Jessell TM. Principles of Neural Science. 4th ed. New York: McGraw-Hill; 2000.  Back to cited text no. 16
    
17.
Schacter DL, Gilbert DT, Wegner DM. Psychology. 2nd ed. New York: Worth; 2011.  Back to cited text no. 17
    
18.
Wyszecki G, Stiles WS. Color science: Concepts and methods, quantitative data and formulae. In: Wiley Series in Pure and Applied Optics. 2nd ed. New York: Wiley-Interscience; 2000.  Back to cited text no. 18
    
19.
Barghi N, Pedrero JA, Bosch RR. Effects of batch variation on shade of dental porcelain. J Prosthet Dent 1985;54:625-7.  Back to cited text no. 19
    
20.
Wasson W, Schuman N. Color vision and dentistry. Quintessence Int 1992;23:349-53.  Back to cited text no. 20
    
21.
Davison SP, Myslinski NR. Shade selection by color vision-defective dental personnel. J Prosthet Dent 1990;63:97-101.  Back to cited text no. 21
    
22.
Barbur JL, Rodriguez-Carmona M. Variability in normal and defective colour vision: Consequences for occupational environments. In: Best J, editor. Colour Design. Cambridge: Woodhead Publishing Limited; 2012.  Back to cited text no. 22
    
23.
Ethell J, Jarad FD, Youngson CC. The effect of colour defective vision on shade matching accuracy. Eur J Prosthodont Restor Dent 2006;14:131-6.  Back to cited text no. 23
    
24.
Khosla A, Maini AP, Wangoo A, Singh S, Mehar DK. Prevalence of colour vision anomalies amongst dental professionals and its effect on shade matching of teeth. J Clin Diagn Res 2017;11:ZC33-6.  Back to cited text no. 24
    
25.
Jameson KA, Highnote SM, Wasserman LM. Richer color experience in observers with multiple photopigment opsin genes. Psychon Bull Rev 2001;8:244-61.  Back to cited text no. 25
    
26.
Swanson WH, Cohen JM. Color vision. Ophthalmol Clin North Am 2003;16:179-203.  Back to cited text no. 26
    
27.
Birch J. Efficiency of the Ishihara test for identifying red-green colour deficiency. Ophthalmic Physiol Opt 1997;17:403-8.  Back to cited text no. 27
    
28.
Birch J. Clinical use of the American optical company (Hardy, Rand and Rittler) pseudo-iso-chromatic plates for red-green colour deficiency. Ophthalmic Physiol Opt 1997;17:248-54.  Back to cited text no. 28
    
29.
Cole BL, Lian KY, Lakkis C. The new Richmond HRR pseudo-iso-chromatic test for colour vision is better than the Ishihara test. Clin Exp Optom 2006;89:73-80.  Back to cited text no. 29
    
30.
Birch J. Identification of red-green colour deficiency: Sensitivity of the Ishihara and American Optical Company (Hard, Rand and Rittler) pseudo-iso-chromatic plates to identify slight anomalous trichromatism. Ophthalmic Physiol Opt 2010;30:667-71.  Back to cited text no. 30
    
31.
Ishihara S. Tests for Colour Blindness. Toyko, Japan: Kanehara Shupper Co. Ltd.; 1972.  Back to cited text no. 31
    
32.
Ishihara S. Tests for Colour Blindness. London: Hodder Arnold; 1998.  Back to cited text no. 32
    
33.
Chorley AC. A modified protocol for color vision screening using Ishihara. Aerosp Med Hum Perform 2015;86:747-51.  Back to cited text no. 33
    
34.
Gündogan NU, Durmazlar N, Gümüş K, Ozdemir PG, Altintaş AG, Durur I, et al. Projected color slides as a method for mass screening test for color vision deficiency (a preliminary study). Int J Neurosci 2005;115:1105-17.  Back to cited text no. 34
    
35.
Ganley JP, Lian MC. Projected color slides as a method for mass screening of red-green color deficient individuals. Ophthalmic Epidemiol 1997;4:213-21.  Back to cited text no. 35
    
36.
Cole BL. Assessment of inherited colour vision defects in clinical practice. Clin Exp Optom 2007;90:157-75.  Back to cited text no. 36
    
37.
Moser JB, Wozniak WT, Naleway CA, Ayer WA. Color vision in dentistry: A survey. J Am Dent Assoc 1985;110:509-10.  Back to cited text no. 37
    
38.
Ramachandran N, Wilson GA, Wilson N. Is screening for congenital colour vision deficiency in school students worthwhile? A review. Clin Exp Optom 2014;97:499-506.  Back to cited text no. 38
    
39.
Naik A, Pai R. Color Blindness in dental students and staff and obstacle in shade selection for restorations. Ann Essences Dent 2010;11:25-8.  Back to cited text no. 39
    
40.
Alqahtani NA, Togoo RA, Alqahtani MM, Suliman NS, Alasmari FA, Alqahtani FM, et al. Frequency of color vision deficiency among Saudi dental students: A cross-sectional study. Eur J Dent 2021;15:27-32.  Back to cited text no. 40
    
41.
Birch J. Worldwide prevalence of red-green color deficiency. J Opt Soc Am A Opt Image Sci Vis 2012;29:313-20.  Back to cited text no. 41
    
42.
Deeb SS, Kohl S. Genetics of color vision deficiencies. Dev Ophthalmol 2003;37:170-87.  Back to cited text no. 42
    
43.
Ladekjaer-Mikkelsen AS, Jensen H, Rosenberg T, Jørgensen AL. Molecular genetics of red-green color blindness. Ugeskr Laeger 1995;157:4808-12.  Back to cited text no. 43
    
44.
Deeb SS. Molecular genetics of colour vision deficiencies. Clin Exp Optom 2004;87:224-9.  Back to cited text no. 44
    
45.
Deeb SS. Molecular genetics of color-vision deficiencies. Vis Neurosci 2004;21:191-6.  Back to cited text no. 45
    
46.
Deeb SS. The molecular basis of variation in human color vision. Clin Genet 2005;67:369-77.  Back to cited text no. 46
    
47.
Rigaudière F, Leid J, Viénot F, Le Gargasson JF. Neurophysiological basis and clinical tests for assessment of X-linked color vision deficiencies in school children. J Fr Ophtalmol 2006;29:87-102.  Back to cited text no. 47
    
48.
Dargahi H, Einollahi N, Dashti N. Color blindness defect and medical laboratory technologists: Unnoticed problems and the care for screening. Acta Med Iran 2010;48:172-7.  Back to cited text no. 48
    
49.
Dohvoma VA, Mvogo SR, Kagmeni G, Emini NR, Epee E, Mvogo CE. Color vision deficiency among biomedical students: A cross-sectional study. Clin Ophthalmol 2018;12:1121-4.  Back to cited text no. 49
    


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