Prevalence of Refractive Errors and its Associated Risk Factors among Medical Students of Jazan University, Saudi Arabia: A Cross-sectional Study.

PURPOSE: Refractive errors (REs) are common and continue to increase globally, particularly myopia. Uncorrected REs are the second leading cause of preventable blindness and the most common cause of visual impairment. The main objective of this study is to assess the prevalence of REs and to investigate its associated risk factors among medical students of the Jazan region, Saudi Arabia.
METHODS: An observational analytical cross-sectional study was conducted among a random sample of 447 medical students at Jazan University. Eye examination was conducted using an autorefractor test (Huvitz HRK-8000A Autorefractor Keratometer) to measure spherical refraction (emmetropia, myopia, and hyperopia) and cylindrical refraction (astigmatism). Factors associated with myopia and hyperopia were evaluated using logistic regression models.
RESULTS: The overall prevalence of REs was 48.8% (95% confidence interval [CI] [44.2, 53.4]). The prevalence of REs among female medical students was 55.1% (95% CI [48.6, 61.5]), which was significantly higher than that among males (42.3%, 95% CI [36.0, 48.9]), with a P = 0.007. Of the 447 medical students examined, approximately one-third (33.8%) had myopia, 10.5% had astigmatism, and only 10.5% had hyperopia. The results of logistic regression indicated that females were 52% more myopic than males (odds ratios [OR] = 1.52, 95% CI [1.04, 2.22]), while participants with both parents having a history of REs were twofold more myopic than students with no family history of REs (OR = 2.01, 95% CI [1.2, 3.4]). A history of blurred vision also increases the risk of myopia by seven times (OR = 7.2, 95% CI [6.4, 11.3]).
CONCLUSION: RE among medical students is a problem. Thus, it needs to be assessed carefully before students choose a specialty that may need very good near and far vision for postgraduate study. Copyright:

Introduction

Refractive errors (REs) are defined as a condition, in which the optics of the nonaccommodating eye are unable to take parallel light rays to concentrate on the retina. REs can present singularly such as myopia (nearsightedness), hyperopia (farsightedness), and astigmatism, or combined, such as myopic astigmatism and hyperopic astigmatism.[1] A recent meta-analysis study involved data from 98 countries revealed that uncorrected RE was among the leading causes for moderate or severe vision impairment.[2] The WHO estimated that severe REs accounted for 5 million blind persons globally.

For prevention of the blindness, the WHO and the International Agency for the Prevention of Blindness identified uncorrected REs as one of the priorities program, through Vision 2020 initiative to eliminate avoidable blindness.[3] Uncorrected REs burden individuals and society with increased morbidity, economic hardship, and decreased opportunities for education and productivity.[4]

REs are now prevalent and continue to increase globally, particularly myopia.[5] The risk of myopic complications, such as cataracts, glaucoma, retinal detachment, and blindness, is increasing as well.[6] Several studies have shown that the major factors associated with myopia were genetic and environmental factors, as they contribute to raising myopia around the world.[7] The literature suggested that watching TV, especially from a short distance, using electronic devices for a long time, using dim light while reading, family history, gender (female), and near work activity are major risk factors for REs.[8910]

Worldwide, numerous studies were conducted on RE and provided highly variable results. In Norway, 47% of students were myopic.[11] In Malaysia, it is stated that 7% of medical students were hyperopic,[12] while the prevalence of myopia was 89.8% in Singapore.[13]

In KSA, relatively few studies have been conducted among medical students. Studies that had been conducted in Qassim, Aljouf, and Riyadh showed relatively high myopic prevalence among the students.[589] Among Qassim and Riyadh students, studies showed that approximately 50% of them were myopic.[59] Aljouf University study showed the highest rates of REs at 83.1% prevalence of myopia.[8] In contrast, hyperopia and astigmatisms had a lower rate than myopia, with a prevalence between 3% and 32% in Qassim and Aljouf studies, respectively.[58] In Jazan region, several studies on REs were conducted, but no research has been conducted among medical students. This study aims to assess the prevalence of REs and its associated risk factors among medical students of Jazan University.

Methods

Study design, setting, and population

An analytical, cross-sectional study was conducted among medical students of Jazan University. Jazan University is a leading higher educational institution in the region, with 26 faculties enrolling more than 50,000 students. The estimated number of medical students was 475 in the male section and 509 in the female section. Inclusion criteria were being a medical student (males and females) who registered for the academic year 2019/2020 and having signed the consent form to participate in the study. The exclusion criteria involved any prior history of ocular diseases or procedures.

Sampling procedures

The sample size for this study is calculated to be 460 students. The estimation was based on the sample size formula for cross-sectional study designs, using the following parameters: prevalence of RE = 50% (as no previous study on RE was conducted at Jazan University), a 95% confidence interval (CI), and an error of not more than 5%. Furthermore, the study assumed a nonresponse rate of 15%. The final sample size was equally divided into males and females as there is equal proportion of males and females. The sample size was then stratified according to the different classes within the Faculty of Medicine at Jazan University.

Data collection techniques and study instrument

A self-administered questionnaire and a clinical checklist involving the results of the eye test were used for data collection. The checklist involved the collection of clinical data using an ophthalmology mobile clinic. The self-administered questionnaire involves four sets of data. The first part includes demographic information (age, gender, place of residence, etc.). The second part includes data regarding knowledge about having a RE and family history, whereas the third part includes data regarding lifestyle (suffering from blurred vision, feeling a headache, a previous eye operation, and usage of contact lenses). The fourth part includes risk factors involving the average number of hours/days spent on near work (reading, usage of a mobile, usage of an iPad or computer, playing a video game, and watching TV).

Eye examinations

After completing the questionnaire, all participants went to the examination. The examination was conducted by an optometrist and involved one step, which was the measurement of objective refraction. This was done by an autorefractor test (Huvitz HRK-8000A Autorefractor Keratometer) to measure spherical refraction (emmetropia, myopia, and hyperopia) and cylindrical refraction (astigmatism). The autorefractor examination was done by placing each student's chin on the chin holder and asking him/her to view the image with both eyes. The same examiner used the same device for all the participants.

Operational definitions

The definitions of RE were based on the following. Myopia was considered if spherical equivalent refraction (SER) ≤0.75 D, emmetropia if SER is between −0.75 D and 1 D, and hyperopia if SER ≥1 D. Myopia was further classified as low, moderate, and severe. Low myopia was defined as SER of −0.75 to −2.99 D, moderate as SER from −3.00 to −5.99 D, and severe as SER ≥−6.00 D. Astigmatism ≥1.00 was defined as diopter of cylinder.[5]

Ethics

This study was conducted in accordance with the bioethics standards of the Kingdom of Saudi Arabia. Ethical approval was obtained from the Institutional Review Board of Jazan University. The study participants were told that they had the right not to participate in the study. Moreover, the participants' privacy was respected, and the data were kept confidential and were utilized for study purposes only.

Data analysis

The data were entered and analyzed using SPSS version 20 (SPSS Inc., Chicago, IL, USA). Data analysis involved descriptive statistics analysis and some techniques of inferential statistics. The descriptive statistics included simple tabulation, frequencies, and cross-tabulations. The Chi-squared test was used to test differences in proportion. Univariate logistic regression models were used to assess factors associated with myopia/hyperopia. The models' results are reported as odds ratios (OR) with 95% CI. A P < 0.05 was used as the cutoff level to indicate statistical significance.

Results

A total of 447 medical students signed the study consent and participated in the eye examinations (222 males and 225 females), with a nonresponse rate of 2.8% (447 out of 460). The sociodemographic characteristics of the students are described in Table 1. Of the sample, 56.4% were in the age group of 21–23 years. The mean age was 21.7 years for both males and females. Almost 49.0% of the students in the sample had a Cumulative Grade Points Average equivalent of very good. Students with no family history of RE formed 31.8% of the sample. The same table presents the mean values of spherical equivalent RE for both eyes by different characteristics. The overall mean refraction was −0.91 ± 1.83 (95% CI [−1.08, −74]) in the right eye compared to −0.78 ± 1.67 (95% CI [−0.93, −62]) in the left eye.

Table 1

Background characteristics and mean values spherical equivalent refraction

Characteristic	n (%)	Mean±SD
		Right eye SER	Left eye SER
Gender
Male	222 (49.7)	-0.88±1.80	-0.73±1.55
Female	225 (50.3)	-0.94±1.87	-0.83±1.78
Age groups (years)
18-21	120 (26.8)	-0.79±1.58	-0.72±1.67
21-23	252 (56.4)	-0.99±2.00	-0.84±1.77
24-27	71 (15.9)	-0.8±1.56	-0.70±1.29
Study level (years)
2nd	94 (21.0)	-0.97±1.69	-0.82±1.88
3rd	118 (26.4)	-0.88±1.80	-0.93±1.65
4th	108 (24.2)	-0.66±1.54	-0.47±1.72
5th	106 (23.7)	-1.21±2.29	-0.90±1.52
6th	21 (4.7)	-0.51±1.14	-0.70±1.05
Mode of living
Urban	187 (41.8)	-0.89±1.90	-0.79±1.84
Rural	251 (56.2)	-0.93±1.79	-0.76±1.54
CGPA
Pass	28 (6.3)	-0.82±1.79	-0.86±1.74
Good	52 (11.6)	-1.39±2.63	-0.94±1.73
Very good	219 (49.0)	-0.85±1.73	-0.84±1.63
Excellent	121 (27.1)	-0.86±1.64	-0.65±1.70
Parental history of refractive error
None	142 (31.8)	-0.82±1.69	-0.64±1.45
One	109 (24.4)	-0.87±1.63	-0.82±1.87
Both of them	107 (23.9)	-1.23±1.87	-1.02±1.70
Mobile use per day (h)
<4	103 (23.0)	-1.05±2.21	-0.90±1.78
4-7	178 (39.8)	-0.82±1.50	-0.66±1.70
8+	158 (35.3)	-0.96±1.93	-0.87±1.58
Video game (h)
<1	317 (70.9)	-1.01±1.82	-0.91±1.77
1+	123 (27.5)	-0.66±1.85	-0.45±1.29
Total 95% CI	447 (100)	-0.91±1.83 (-1.08, -74)	-0.78±1.67 (-0.93, -62)

CI: Confidence interval, SD: Standard deviation, CGPA: Cumulative grade points average, SER: Spherical equivalent refraction

The prevalence of having any type of RE is presented in Table 2. The overall prevalence of REs was 48.8% (95% CI [44.2, −53.4]). The prevalence of REs among female medical students was 55.1% (95% CI [48.6, 61.5]), which was significantly higher than that among males (42.3%, 95% CI [36.0, 48.9]), with a P < 0.05. The prevalence of RE among students who play video games for <1 h was 53.9% (95% CI [48.4, 59.3]), compared with 36.6% (95% CI [28.6, 45.4]) among participants who play video games more than 1 h/day. REs did not differ significantly according to the rest of the factors presented in the table.

Table 2

Prevalence of refractive errors regarding some selected characteristics

Characteristic	RE+/total	Prevalence	95% CI	P
Gender
Male	94/222	42.3	36.0-48.9	0.007
Female	124/225	55.1	48.6-61.5
Age groups (years)
18-21	51/102	42.5	34.0-51.5	0.054
21-23	136/252	54.0	47.8-60.0
24-27	30/71	42.3	31.4-53.9
Study level (years)
2nd	47/94	50.0	40.0-60.0	0.942
3rd	55/118	46.6	37.8-55.6
4th	53/108	49.1	39.8-58.4
5th	54/106	50.9	41.5-60.3
6th	9/21	42.9	24.4-63.6
Mode of living
Urban	97/187	51.9	44.7-58.9	0.241
Rural	116/251	46.2	40.1-52.4
CGPA
Pass	16/28	57.1	38.9-73.6	0.169
Good	30/52	57.7	44.1-70.2
Very good	104/219	47.5	41.0-54.1
Excellent	55/121	45.5	36.8-54.3
Parental history of refractive error
None	60/142	42.3	43.4-50.0	0.050
One	58/109	53.2	43.9-62.3
Both of them	61/107	57.0	47.5-66.0
Mobile use per day (h)
<4	54/103	52.4	42.8-61.8	0.175
4-7	78/178	43.8	36.7-51.2
8+	84/158	53.2	45.4-60.8
Video game (h)
<1	171/317	53.9	48.4-59.3	0.001
1+	45/123	36.6	28.6-45.4
Overall prevalence	218/447	48.8	44.2-53.4

CI: Confidence interval, CGPA: Cumulative grade points average, RE: Refractive errors

The prevalence of students with myopia, hyperopia, and astigmatism was calculated and is shown in Table 3 broken down by some selected characteristics. Of the 447 medical students examined, approximately one-third (33.8%) had myopia, 10.5% had astigmatism, and only 10.5% had hyperopia. The table further showed that myopia is the most common RE among the medical students, and it differs significantly according to gender, parental history of RE, and duration of playing video games (P < 0.05 for all).

Table 3

Pattern of refractive errors according to some selected characteristics

Characteristic	Pattern of refractive errors			Emmetropia	P
	Myopia	Hyperopia	Astigmatism
Gender
Male	59 (26.6)	10 (4.5)	25 (11.3)	128 (57.7)	0.015
Female	92 (40.9)	10 (4.4)	22 (9.8)	101 (44.9)
Age groups (years)
18-21	38 (31.7)	2 (1.7)	11 (9.2)	69 (57.5)	0.184
21-23	95 (37.7)	14 (5.6)	27 (10.7)	116 (46.0)
24-27	18 (25.4)	4 (5.6)	8 (11.3)	41 (57.7)
Study level (years)
2nd	35 (37.2)	3 (3.2)	9 (9.6)	47 (50.0)	0.106
3rd	35 (29.7)	3 (2.5)	17 (14.4)	63 (53.4)
4th	37 (34.3)	11 (10.2)	5 (4.6)	55 (50.9)
5th	38 (35.8)	3 (2.8)	13 (12.3)	52 (49.1)
6th	6 (28.6)	0 (0.0)	3 (14.3)	12 (57.1)
Mode of living
Urban	63 (33.7)	10 (5.3)	24 (12.8)	90 (48.1)	0.373
Rural	85 (33.9)	9 (3.6)	22 (8.8)	135 (53.8)
CGPA
Pass	12 (42.9)	2 (7.1)	2 (7.1)	12 (42.9)	0.239
Good	19 (36.5)	4 (7.7)	7 (13.5)	22 (42.3)
Very good	68 (31.1)	7 (3.2)	29 (13.2)	115 (52.5)
Excellent	45 (37.2)	3 (2.5)	7 (5.8)	66 (54.5)
Parental history of refractive error
None	43 (30.3)	7 (4.9)	10 (7.0)	82 (57.7)	0.027
One	34 (31.2)	7 (6.4)	17 (15.6)	51 (46.8)
Both of them	48 (44.9)	2 (1.9)	11 (10.3)	46 (43.0)
Mobile use per day (h)
<4	36 (35.0)	5 (4.9)	13 (12.6)	49 (47.6)	0.622
4-7	53 (29.8)	8 (4.5)	17 (9.6)	100 (56.2)
8+	61 (38.6)	6 (3.8)	17 (10.8)	74 (46.8)
Video game (h)
<1	124 (39.1)	15 (4.7)	32 (10.1)	146 (46.1)	0.002
1+	26 (21.1)	4 (3.3)	15 (12.2)	78 (63.4)
Overall prevalence	151 (33.8)	20 (4.5)	47 (10.5)	229 (51.2)

CGPA: Cumulative grade points average

Table 4 presents the associations between myopia, hyperopia, and certain risk factors based on logistic regression models. The table showed that females were 52% more myopic than males (OR = 1.52, 95% CI [1.04, 2.22]) and that students with both parents having a history of RE were twofold more myopic than students with no family history of REs (OR = 2.01, 95% CI [1.2, 3.4]). A history of blurred vision also increases the risk of myopia by seven times (OR = 7.2, 95% CI [6.4, 11.3]). Increasing the distance from the TV is associated with a higher prevalence of myopia, as shown by the OR over unity (OR = 1.14, 95% CI [1.04, 1.3]). Using contact lenses was positively associated with hyperopia (OR = 2.1, 95% CI [1.02, 4.0]).

Table 4

Associations of myopia/hyperopia in the medical students based on logistic regression models

Factors	Myopia		Hyperopia
	OR	95% CI	OR	95% CI
Gender
Male	1		1
Female	1.52*	1.04-2.22	1.5	0.71-3.1
Family history
None	1
One	1.60	0.91-2.7	1.74	0.52-5.8
Both of them	2.01*	1.2-3.4	0.56	0.22-1.35
History of headache
No	1		1
Yes	1.27	0.87-1.8	1.18	0.57-2.44
History of blurred vision
No	1		1
Yes	7.2	6.4-11.3	1.73	0.84-3.5
Using contact lenses
No	1		1
Yes	1.30	0.85-1.1	2.1*	1.02-4.0
Mobile use per day	0.96	0.92-1.0	1.06	0.96-1.16
TV distance (m)	1.14*	1.04-1.3	0.93	0.82-1.04
Average time video	1.11	0.95-1.27	1.15	0.81-1.64

CI: Confidence interval, OR: Odds ratio

Of the 151 medical students who are classified as myopic, 76.3% had low myopia, 19.9% had moderate myopia, and only 3.9% had high myopia. According to gender, 79.0% of females and 72.8% of males had low myopia [Figure 1].

Figure 1

Different levels of myopia according to gender

Discussion

REs are among the leading causes of vision loss worldwide.[2] Therefore, it has been the concern of numerous researches worldwide to determine the patterns of its prevalence among different populations and to determine the risk factors impacting its prevalence. The present study was conducted among medical students who are frequently more exposed to risk factors affecting their vision such as near work.

Our study revealed that about half of the students (48.8%) who participated in the study had a form of REs. Compared to the prevalence reported by previous studies, there was a great variation between different countries. Furthermore, the prevalence of RE varied between different groups within the same country [Table 5].

Table 5

Prevalence of refractive errors among medical students in different countries

Study	Sample size	Population-country	Prevalence (%)
Alsaif et al. 2019[14]	338	Imam Abdulrahman bin Faisal University-Saudi Arabia	47.9*
Patel et al. 2019[10]	248	GMERS Medical College-India	48.3
Rizyal et al. 2019[15]	210	Nepal Medical College-Kathmandu Nepal	51.4
Shi et al. 2018[16]	3654	Tianjin Medical University-China	89.93
Alruwaili et al. 2018[8]	278	Aljouf University Medical Students-Saudi Arabia	83.1
Al-Rashidi et al. 2018[5]	162	Medical Students of Qassim University-Saudi Arabia	53.7*
Alruwaili et al. 2018[17]	167	Northern Border University-Saudi Arabia	67.1
Algorinees 2017[18]	504	Hail University and Prince Sattam University-Saudi Arabia	53.5*
Jyothirmai et al. 2017[30]	361	Andhra Medical College-Visakhapatnam	70.7
Salih 2017[19]	330	El-Mustansiriyah Medical Students-Iraq	33
Kshatri et al. 2016[20]	506	Medical College of Odisha-India	54.5*
Basu et al. 2016[21]	244	Medical Student of Kolkata-India	26.23
Grigoras et al. 2016[22]	576	Medical students from “Grigore T. Popa” University of Medicine and Pharmacy-Romania	73.8*
Parveen et al. 2015[23]	500	Liaquat National Medical College-Karachi Pakistan	47*
Sharvani et al. 2015[24]	100	RIMS KADAPA-India	32.24
Dey et al. 2014[25]	580	Burdwan Medical College-India	56.90
Ahmed et al. 2014[9]	419	Medical Students of King Saud University-Saudi Arabia.	44.4*
Krishnakumar et al. 2014[26]	235	Myopia and Digit Ratio in Medical College Students-India	54*
Megbelayin et al. 2014[27]	83	Nigerian MedicalSchool-Nigerian	79.5
Rajdeep and Patel 2013[28]	283	Baroda Medical College - India	54.06%
Gopalakrishnan et al. 2011[12]	425	AIMST University - Malaysia	32.24%

*The prevalence in those studies was based only on myopia

The prevalence revealed by the present study was lower than those previously reported in some districts of Saudi Arabia (Aljouf and Northern Border Universities).[817] It was also lower than what was reported in China, Romania, Nigeria, and Andhra Medical College in India.[3162227] However, it was higher than the prevalence recorded in other parts of India.[2124] It was also higher than the prevalence observed in Iraq and Malaysia.[1219]

Nevertheless, several studies reported a similar prevalence to that of our study including studies conducted in Saudi Arabia (in Dammam, Qassim, Hail, and Riyadh),[591418] India, Pakistan, and Nepal.[10152023252628] Those variations in prevalence could be related to differences in lifestyle, socioeconomic status, and environmental factors.

Furthermore, the present study showed that myopia was the most common type of REs, affecting one-third (33.8%) of the students compared to hyperopia and astigmatism. While other studies conducted in the KSA agreed that myopia was the most common type of REs among students,[589] they reported a higher prevalence of myopia than our study.

Regarding hyperopia and astigmatism, our study revealed that 10.5% of the students had hyperopia and 10.5% had astigmatism. These percentages are higher compared to those previously reported by Al-Rashidi et al. in Qassim, who reported that only 3.7% of the students had hyperopia and only 1.2% had astigmatism.[5] Similarly, Alruwaili et al. reported a low prevalence of hyperopia (3.5%) and a significantly higher prevalence of astigmatism (53.7%) among Aljouf students.[8]

Regarding the RE risk factors, our results showed that family history is a major risk factor for myopia, by twofold, as had also been found among students of Hail University and Prince Sattam University.[18] In agreement with results from King Saud University, we found that females were more affected than males.[9]

Our results also revealed a strong association between TV distance and myopia, with a larger distance being associated with a higher risk of having myopia, which is completely different from what was documented in Jazan.[29] However, usage of electronic devices was insignificant in our study, which was clearly shown in GMERS University in India.[10] We also found that wearing contact lenses is associated with hyperopia, while in another study in Saudi Arabia, they found that it was associated with myopia.[18] However, age was insignificant in our findings, unlike what was previously reported in Hail University and Prince Sattam University study.[18]

While conducting our study, we came across some limitations. First, the study is based on a cross-sectional study design; therefore, temporal associations cannot be properly established. The second limitation of the study was the short timetable to collect our data. In addition, collecting the data while students attend their lectures or take exams affected their participation in the study. Finally, since we used an autorefractor test to measure the REs among students, the results were objective rather than subjective.

Conclusion

REs, mainly myopia, were highly prevalent among medical students at Jazan University, Saudi Arabia. Female students were more affected than male students. We recommend increasing awareness among medical students of RE and carrying out screening programs to early detect and correct RE to prevent future vision problems.

Financial support and sponsorship

This research project was funded by the Deanship of Scientific Research at Jazan University (Project number FS10-057).

Conflicts of interest

There are no conflicts of interest.