Prevalence and Factors Associated with Refractive Errors among University Students at Mbarara University of Science and Technology, Uganda ()
1. Introduction
Refractive errors (RE) arise when parallel rays of light do not focus on the retina [1]. Common types of refractive errors include myopia (nearsightedness), hyperopia (long-sightedness), and astigmatism [2]. People with refractive errors complain of blurry vision, difficulty reading, headache, eyestrain. Genetic and environmental factors play a major role in the development of refractive errors [3].
Refractive errors are the leading cause of visual impairment (101.2 million people worldwide) [4] [5]. Uncorrected refractive errors are the second leading cause of blindness (6.8 million people blind) globally) [4] [5]. Uncorrected refractive errors are recognized as a public health burden as it leads to loss in productivity affecting people’s lifestyle, limiting education, employment opportunities of active and healthy individuals [6]. Factors that lead to uncorrected refractive errors include lack of awareness among affected individuals, lack of readily available screening and testing services, insufficient corrections, and cultural disincentives for the use of optical correction in some countries [7].
Refractive error prevalence, more so myopia, is increasing dramatically in the group of people who are getting a higher education level like a university [8]. Students with uncorrected refractive errors strain to read standard-sized print, overhead projection, computer, color discrimination thus impacting their learning, academic achievement, and employability [2]. A study conducted at the University of Trondheim, Norway and another study conducted by different Universities in Kazerun, Iran [9] found that the risk for developing refractive errors was higher in university students than in the general population.
In Uganda, studies done on the prevalence of refractive errors were based on the community and primary schoolchildren with a prevalence of 4.6% [10] and 11.6% respectively. Little is known about refractive errors among university students in Uganda and or East Africa [11].
Refractive errors are a priority for eye disease by the World Health Organization stated in the global initiative Vision 2020’ for reducing preventable blindness. Information about refractive errors in university students helps in planning effective programs to deal with the problem. This study sought to bridge the existing knowledge gap about refractive errors among university students in Uganda by not only assessing the common refractive errors but also focusing on the likely contributory factors among students in the Faculty of Medicine at Mbarara University of Science and Technology (MUST). It added knowledge by providing information on this subject, emphasizing the need for more screening strategies, correction and further planning.
2. Methods
2.1. Ethical Statement
This study adhered to the tenets of the Helsinki declaration. Approval of the study was obtained from the faculty of Medicine research committee (Ref: DMS 6) and the research ethics committee (Ref: MUREC 1/7) at Mbarara University of Science and Technology. Informed consent was sought from all the enrolled participants (See Appendix A).
This was a cross-sectional descriptive and analytical study conducted among undergraduate students in the Faculty of MUST, Southwestern Uganda from April 2021 to July 2021.
The sample size was calculated using the formula for estimation of a single proportion by Kelsey (Kelsey et al., 1996)
.
where: Z value = 1.96.
P = the prevalence of refractive errors among university students was assumed to be 54% based on a study conducted at Era’s Lucknow Medical College and Hospital [12], this study was used because its sample size suits our study as their population size was similar to our study population size and the margin error of estimation that was assumed to be 5% (0.05). This provided 382 students and to account for the predicted 20% non-response rate, the final sample was 458 students.
2.2. Case Definition
A student was diagnosed to have g refractive error if found with spherical equivalent (SE) calculated as sphere plus half-cylinder of ±0.50. Myopia was defined as a spherical error (SE) of at least −0.50 diopters (D), hyperopia was defined as SE of at least +0.50D and astigmatism was defined as a cylinder of at least 0.50D [13].
2.3. Inclusion Criteria
We enrolled students in the Faculty of Medicine willing to participate by signing the informed consent and with clear visual axes that could not affect the refraction procedure plus those using corrective eyeglasses.
2.4. Exclusion Criteria
We excluded students with ocular comorbidities affecting vision for example cornea, lens and vitreous opacities, retinal and macular abnormalities and those with previous ocular surgery affecting vision.
2.5. Variables
We enrolled a total of 368 students. The data collected include: socio-demo- graphics, ophthalmic history including lifestyle factors, visual acuities, and results of refraction examination. The WHO Examination form [14] was modified and used to collect data as a questionnaire containing (socio-demographics, ophthalmic history including lifestyle factors, results of refractive examination) that was pretested and found valid for the study.
2.6. Data Collection
Instruments used included Retinoscope, pen torch, lensometer, pinhole, direct ophthalmoscope, trial frame and lenses. A questionnaire (Appendix B) was used to capture socio demographic data and ocular history. The WHO Examination form was modified and used to collect data [14]. The questionnaire had sections (socio-demographics, ophthalmic history including lifestyle factors, results of refractive examination). A Research Assistant (RA) with qualifications of being a nurse off duty during the time of data collection helped in registration and administering questionnaires to the participants.
Screening of participants for eligibility was done by the PI using a torch and a direct ophthalmoscope. Those who met the inclusion criteria consented, registered, and information about socio-demographics, ophthalmic history, and lifestyle were collected in the same sitting by the RA. Visual acuity was assessed using a Snellen’s chart at 6 meters in a well-lit room or open space. Students wearing glasses were assessed with and without them, the refractive power of the glasses was measured using a lensometer. Pinhole acuity was measured in students whose visual acuities were worse than 6/6. And when these student’s visual acuity improved with pinhole, the cause of the reduction in vision was considered to be mainly refractive. Therefore, objective refraction was carried out in all those with visual acuity (VA) less than 6/6 that improved with the pinhole by principal investigator and optometrists at Mbarara University Referral & Eye Center, and subjective refraction was performed by achieving best-corrected visual acuity using Snellen’s chart. Refractive error was defined as spherical equivalent (SE) calculated as sphere plus half-cylinder. Myopia was defined as a spherical error (SE) of at least −0.50 diopters (D), hyperopia was defined as SE of at least +0.50D and astigmatism was defined as a cylinder of at least 0.50D [13]. Examination of the anterior segment and posterior segment was done using a pen torch or ophthalmoscope light and the direct ophthalmoscope.
2.7. Data Analysis
Data recorded on the pretested questionnaire was entered into EPI INFO version 3.5 and exported from EPI INFO to STATA software version 14.0.
Tables and figures were used to display results of descriptive analysis. The prevalence of refractive errors was got and a p-value of 0.05 was used to determine a significant association between refractive errors and independent factors.
3. Results
3.1. Socio-Demographic Characteristics of the Study Participants
368 students participated in the study to give a response rate of 80.3%. The mean age of the study population was 22.7 ± 3.7 years (range, 18 - 45 years) Table 1.
Most of the student participants 94% (n = 368) were between 18 - 29 years. Male students were the majority 240 (65%) and 128 (35%) were females. Year 1 students were 29% (105) of the total participants, Year 2 were 30% (n = 368) and Year 3 - 4 students were the majority at 41% (n = 368).
Table 1. Social demographics.
Demographics |
Social Demographics |
Category |
Frequency (368) |
Percentage% |
Age |
|
|
18 - 29 |
335 |
94 |
30 - 45 |
21 |
6 |
Sex |
|
|
Male |
240 |
65 |
Female |
128 |
35 |
Program |
|
|
Medicine |
127 |
34 |
Nursing |
64 |
17 |
Physiotherapy |
39 |
11 |
Pharmacy |
138 |
38 |
Year of study |
|
|
1 |
105 |
29 |
2 |
112 |
30 |
3 - 4 |
151 |
41 |
Family history of using prescribed glasses among parents and siblings was reported by 44% (163) and 21% (n = 368) reported a history of using corrective glasses. About 85% (308) of the students’ participants reported a history of reading for less than 9 hours daily Table 2. Photophobia and headache while reading were the major reported complaints among all the students at 32% followed by eye pain at 30% with the least complaint of blurry vision reported at 22% among the students (n = 368) as shown in Figure 1.
Figure 1. Eye complaints among students.
Table 2. Students’ lifestyle.
Demographics |
Students’ lifestyle |
Category |
Frequency (368) |
Percentage % |
History of using glasses by Students |
|
|
Yes |
77 |
21 |
No |
291 |
79 |
Family history |
|
|
Yes |
163 |
44 |
No |
205 |
56 |
Daily reading time |
|
|
8 hours |
308 |
84.9 |
More than 8 hours |
55 |
15.2 |
Reading time |
|
|
Day |
138 |
37.60 |
Night |
229 |
62.40 |
Sleep time |
|
|
Before midnight |
165 |
44.9 |
After midnight |
202 |
55.0 |
Preferred leisure activity |
|
|
Indoor |
195 |
53.3 |
Outdoor |
171 |
46.7 |
Time spent watching television |
|
|
≤3 hours |
333 |
90 |
>3 |
35 |
10 |
Time spent on phone |
|
|
≤3 hours |
43 |
12 |
>3 |
325 |
88 |
Time spent using computer |
|
|
≤3 hours |
193 |
52 |
>3 |
175 |
48 |
Sleep duration |
|
|
≤6 hours |
268 |
73 |
>6 |
100 |
27 |
3.2. Prevalence of Refractive Errors
Among the 368 students enrolled during our study period, refractive errors were present in 97 of them giving an overall prevalence of 26.36% (See Table 2).
Table 3 shows the prevalence of different types of refractive errors among our students. Most of the students had Myopia (58/97) 60%, followed by Astigmatism (36/97) 37% and Hypermetropia 3%. Astigmatism consisted of largely myopic astigmatism 72% (26) and 28% (10) compound/mixed astigmatism only.
Table 3. Types of refractive errors.
Types of refractive errors |
Types of refractive errors |
Frequency |
Percentage |
Astigmatism |
36 |
37 |
Myopia |
58 |
60 |
Hyperopia |
3 |
3 |
Total |
97 |
100 |
Among the students found with refractive errors (27/97) 28% were using corrective glasses and of those 30% (8/27) were using glasses that were not correct for their current refractive errors as shown in Table 4.
Table 4. Glass use among students with refractive errors.
Glass use |
Glass use among students with refractive errors. |
Frequency (%) |
Percentage |
NO |
70 |
72 |
YES |
19 |
28 |
Correct power |
8 |
|
Not Correct power |
|
|
Total |
97 |
100 |
3.3. Factors Associated with Refractive Errors
In bivariate analysis (Table 5), positive family history of parents and siblings using glasses was found to be associated with having refractive errors. In multivariate analysis (Table 5), the only factor associated with students having refractive errors was positive family history of parents and siblings using glasses and this was statistically significant p value of 0.05%.
Table 5. Bivariate and multivariate analysis results of factors associated with refractive errors.
Factor |
Bivariate analysis |
Multivariate analysis |
UOR (95% CI) |
P Value |
AOR (95% CI) |
P (0.0498) |
Sex |
|
|
|
|
Male |
1.0 |
0.072 |
Female |
1.5 (0.96 - 2.49) |
Age (years) |
|
|
|
|
18 - 29 |
1.0 |
0.228 |
1.0 |
0.145 |
30 - 45 |
1.75 (0.70 - 4.37) |
1.99 (0.78 - 5.04) |
Study Year |
|
|
|
|
1 |
1.0 |
|
High p value
(not included) |
2 |
0.79 (0.42 - 1.46) |
0.456 |
3 - 4 |
1.00 (0.57 - 1.76) |
0.973 |
Program |
|
|
|
|
Medicine |
1.0 |
|
High p value
(not included) |
Nursing |
1.16 (0.58 - 2.33) |
0.656 |
Physiotherapy |
1.27 (0.56 - 2.85) |
0.562 |
Pharmacy |
1.27 (0.73 - 2.21) |
0.390 |
Preferred Leisure activity |
|
|
|
|
Indoor |
1.0 |
0.546 |
High p value
(not included) |
Outdoor |
0.86 (0.54 - 1.38) |
Reading time |
|
|
|
|
≤8 hours |
1.0 |
0.84 |
High p value
(not included) |
>8 hours |
1.06 (0.56 - 2.03) |
Preferred Reading time |
|
|
|
|
Day |
1.0 |
0.981 |
High p value
(not included) |
Night |
1.0 (0.62 - 1.62) |
Family history of refractive errors |
|
|
|
No |
1.0 |
0.056 |
1.0 |
0.032 |
Yes |
1.57 (0.98 - 2.50) |
1.68 (1.04 - 2.72) |
Time spent using computer |
|
|
|
≤3 hours |
1.0 |
0.165 |
|
|
>3 |
1.3 (0.87 - 2.21) |
|
|
4. Discussion
This study found a high prevalence of refractive errors among medical undergraduate students in the Faculty of Medicine at Mbarara University of Science and Technology. This result is in accordance with a study at Kolkata Teaching Hospital although they had a smaller study [1]. Medical students could have been involved in intensive near work habits right from their early school days, even before joining medical college and in addition an underlying genetic predisposition and ethnicity may alter eye growth leading to the development of refractive errors [15]. Other studies conducted among medical students with a similar prevalence of refractive errors were in Malaysia, Mymensingh Medical College (MMC) with a prevalence of 32.24% [16] and in Al-Mustansiriya Medical College with a reported prevalence of about 33% [2]. The prevalence of refractive errors among medical students has been found higher compared to non-medical students in the general population [9].
However, higher prevalence of refractive errors was found among medical students of Baroda Medical College at 54% [8] and at Era’s Lucknow Medical College and Hospital at 54% [12]. Similar studies were conducted in Odisha, India with the prevalence of refractive errors of 56% [17] in Saudi Arabia, also reported a similar prevalence of refractive error of 58.6% [18]. The prevalence of refractive errors was found among medical students, a prevalence of 79.5% was reported among medical students in Nigeria [11], a prevalence of 83.1% was found among Aljouf University Medical Students [19]. Refractive errors vary in different nations and regions among medical students probably due to variation in genetic predispositions, environment factors, ethnicity, methodology, non- participation rates, and refraction techniques [1] [20].
Myopia was the commonest type of refractive error followed by astigmatism and lastly, hyperopia similar to most studies. Studies that found high prevalence of myopia among medical students included (81.70%) in Bangladesh [21], and in India 77.7% [12], and 54.5% [17], and also in Malaysia, the myopia of 87.6% (Gopalakrishnan et al., 2011). Medical students have intense studying and exposure to performing near work that could explain the high prevalence of myopia [11]. Medical students have intense studying and exposure to performing near work that could explain the high prevalence of myopia [11]. In addition to the intensive near work associated with the professional courses, genetic and racial traits could play a role in the development of myopia.
Astigmatism in this study was also reported similarly by a study conducted in Saudi Arabia that found medical students with 53.7% astigmatism [22] another study among medical students that reported astigmatism of 33.5% [23]. The reason for similarity could be due to the same screening methods, classification and retinoscopy [1].
Low prevalence of hypermetropia was also reported in studies conducted among Aljouf University medical students with reported hypermetropia prevalence of 3.483% [19], a study conducted among medical students at Era’s Lucknow Medical College and Hospital reported (4.5%) hypermetropia [12], (7.3%) hypermetropia were reported among medical students of AIMST University, Malaysia [16] and hypermetropia of (2.73%) was found in students of Al-Mus- tansiriya Medical College [2]. The low prevalence of hypermetropia may be due to the fact that it is often present from birth owing to low the power of eye lens and abnormal shape of the cornea, small eye size. However, children and young adults compensate for the problem with a very flexible eye lens and therefore hypermetropia usually appears when the eye lens is not flexible at a more advanced age [2].
4.1. Factors Associated with Refractive Errors
Student positive family history of refractive error was found to have a statistically significant relationship with refractive errors among the students. Similar results were reported by studies conducted among students in Dow Medical College, Pakistan [24], among medical students of Qassim University, Saudi Arabia [25], among university students of a tertiary care teaching hospital of Kolkata [1], and among students of Nepal Medical College [18]. This association could be due to genetic predisposition from the parents who have refractive errors [20].
4.2. Limitations, Conclusion, and Recommendations
Limitations
Owing to the large student numbers who would come in at any one time and needed to be worked upon quickly, refraction wasn’t done by one optometrist.
Conclusion
The prevalence of refractive errors among medical undergraduate students in the Faculty of Medicine at Mbarara University of Science and Technology was found to be high at 26.36% with Myopia as the commonest refractive error. Student positive family history of refractive error was found to have a statistically significant relationship with refractive errors among the students.
Recommendations
1) Screening of university students upon entry and regular checkup during their study helps detect and differentiate those who already have refractive errors before joining university from those who develop them during the University study.
2) Further studies should be carried out on students to determine the genetic predisposition to having refractive errors since family history was associated with having refractive errors.
Acknowledgements
The authors remain grateful to the Almighty Lord for Your Grace, Mercy and Salvation daily.
Funding
The principal investigator was sponsored by Christian Blind Mission (CBM).
Appendices
A: Research and Ethics Committee Approval Letter
B: Questionnaire
Serial No. Date of Interview: DD|___|___|/MM|___|___|/YY|___|___|___|___| Interviewer initials ☐☐
SECTION A: SOCIODEMOGRAPHICS
Student ID: |___|___|___|___| Age (years) ☐ Sex (1: Male; 2: Female) ☐
Program Name: ________________________Year of study ☐
Region of Origin: (1: Central; 2 Eastern; 3: Northern; 4 Western; 5: Others) ☐
SECTION B: HISTORY AND EYE SYMPTOMS
Circle where appropriate:
B1. Do you use or have you ever used prescribed eyeglasses/contact lenses?
1 = Yes 2 = No
If No go to B3
B2. At what age did you start using them? Years ☐
B3. Are there family members using prescribed eyeglasses/contact lenses?
(1 = Mother or Father 2 = Both 3 = Siblings 4 = None)
If None go to B5
B4. How do they use eyeglasses? (1 = All the time 2 = Reading only)?
B5. How much time in a day do you normally take while reading? Hours ☐
B6. What time do you prefer to read (1 = Day 2 = Night)?
B7. What time do you normally sleep?
(1 = Before 12:00 am 2 = After 12:00 am)
B8. Duration of sleep in a day on average (hours ☐
B9.a. What is your preferred leisure activity (1 = Indoor 2 = Outdoor)?
B9.b. What is the average time spent on these activities in a day?
(1 = Indoor Hours ☐ 2 = Outdoor Hours ☐
B10. How much time in a day do you normally spend viewing/using the following?
a. Phone hours ☐
b. TV hours ☐
c. Computer hours ☐
B11. Tick Yes/No. Do you, have it?
|
1 = Yes |
2 = No |
|
1 = Yes |
2 = No |
1) Eye Pain |
☐ |
☐ |
4) Blurred vision |
☐ |
☐ |
2) Tearing |
☐ |
☐ |
5) Headache |
☐ |
☐ |
3) Photophobia |
☐ |
☐ |
|
☐ |
☐ |
Serial No. Date of Interview: DD|___|___|/MM|___|___|/YY|___|___|___|___| Interviewer initials ☐☐
SECTION C: VISION ASSESSMENT
VA Examiner ID ☐
C1. A student is wearing corrective lenses? 0: NO; 1: YES ☐
If No Go to C3
C2. Visual Acuity with corrective lenses:
Visual Acuity cannot be determined (reason)_________________
C3. A Uncorrected Visual Acuity (UCVA) C3.B Pin hole if UCVA worse than 6/6
|
UCVA |
OD |
/ |
OS |
/ |
|
PH, VA |
OD |
/ |
OS |
/ |
Visual Acuity cannot be determined (reason)_________________
Serial No. Date of Interview: DD|___|___|/MM|___|___|/YY|___|___|___|___| Interviewer initials ☐☐
SECTION D: REFRACTION
D1. Retinoscopy
Cannot be examined (reason)_________________
D2. Subjective refraction (with BCVA)
|
Sphere |
Cyl. |
Axis |
BCVA |
OD |
|
|
|
/ |
OS |
|
|
|
/ |
Cannot be examined (reason)_________________
D3. Lensometry
Cannot be examined (reason)_________________
Comment