Factors associated with the prevalence of refractive errors among medical students in the United Arab Emirates

Study design and setting

This was a cross-sectional study performed through a survey that involved medical students at the United Arab Emirates University (UAEU), the largest university in the UAE with the only public medical school in the country. According to the 2023/2024 academic year record, the total number of medical students at the UAEU was 602. Ethical approval for the study protocol was obtained from the Research Ethics Committee at the UAEU (approval # ERSC_2023_3755). The committee waived the need for written or verbal consent because the study was based on an anonymous questionnaire, filled out voluntarily and without any personally identifiable information. The questionnaire aimed to assess the incidence of different types of REs (myopia, hyperopia, and astigmatism) among medical students and their associated risk factors.

Questionnaire design

The survey was based on a questionnaire developed by our Jordanian collaborators,¹⁹ with minor modifications to reflect the study curriculum at the UAEU and certain physical aspects of the students that might be associated with REs (height and weight). The survey questions were reviewed by several experts, including ophthalmologists and statisticians, who deemed the questions to be reasonable. The questionnaire was developed in English.

The complete questionnaire comprised 14 systematic, accurate questions. Eight questions inquired about the risk factors associated with REs. Four of these were related to the student’s physical characteristics: sex, age, height, and weight. The other four were related to the student environment: study level, family history, use of electronic devices, and exposure to sunlight.

Notably, the medical program at the UAEU is divided into three phases. These are the premedical phase, covering the foundation and basic medical sciences; the preclinical phase, where medical students learn integrated medical sciences in systemic modules; and the clinical phase, where medical students receive proper clinical training through hospital rotations. One of the objectives of this study was to verify if there was an association between the study level (phase) and the development of REs among medical students. Therefore, the frequency of REs was compared among the students in the three different medical phases.

One question related to the family history of REs inquired about having a first-degree relative (parent or sibling) with REs. Additionally, two questions related to the student’s behavior inquired about the daily period of using electronic devices and the daily period of sunlight exposure, as it has been established that myopia is significantly associated with reduced sunlight exposure time.¹¹

The remaining six questions were related to the: presence of an RE, type of RE, dioptric degree, diagnosis age, correction method used, and laser refractive surgery. The REs were classified into five categories: myopia alone, myopia and astigmatism, hyperopia alone, hyperopia and astigmatism, and astigmatism alone. The last question inquired about why the student did not opt to undergo laser refractive surgery because we also aimed to investigate the students’ attitudes toward this ultimate correction method.

Sampling

A link to the survey, which was developed through Google Forms, was distributed to the medical students at the UAEU through repeated official emails between November 2023 and February 2024. This data collection method was more convenient for the students and researchers, and it was rapid and efficient. The link included a preface that explained the aim of the study; a statement that ensured the optionality, anonymity, and confidentiality of the study; the right to withdraw anytime; and the consent to participate.

Statistical analysis

Statistical analyses were performed using IBM SPSS Statistics software (standard version 29.0.0.0, IBM, Armonk, NY, USA). The data were extracted into an Excel file and then transferred to an SPSS spreadsheet. Data were expressed as frequency (percentage) for categorical variables and mean ± standard deviation of the mean (SD) for continuous variables. Cases containing contradictory answers were excluded from the analysis. The level of statistical significance was set at p < 0.05. This was determined using Pearson’s chi-squared test for categorical variables and student’s t-test for continuous variables. Multivariate logistic regression was also applied to determine the main predictors of the incidence of REs among medical students.

Prevalence of REs

A total of 336 students completed the survey, producing a response rate of 55.8% (336/602). However, eight participants were excluded because they provided contradictory answers, such as answering that they had no REs and had myopia as an RE or that they had no REs and used spectacles as a correction method. Three of these eight cases were excluded because the students answered that they used spectacles as a correction method and also answered that they had undergone laser refractive surgery as a correction method.

Among the 328 participants, there were 201 (61.3%) students with REs and 127 (38.7%) without REs. Regarding sex, there were 239 (72.9%) females and 89 (27.1%) males. Most of the participants were in the age range of 17–25 years. The students who completed the survey were distributed according to the three phases of the medical curriculum at the UAEU as follows: 161 (49.1%) in the premedical phase, 98 (29.9%) in the preclinical phase, and 69 (21.0%) in the clinical phase. Most of the students (282/328, 86.0%) had a first-degree relative with an RE and had exposure to sunlight for less than 3 h per day (275/328, 83.8%). Additionally, most of the students (304/328, 92.7%) used electronic devices for more than 5 h per day.

Risk factors associated with REs

The independent risk factors that might be associated with the development of REs are summarized in Table 1. Most of these factors were independently associated with the prevalence of REs among medical students in the UAE. Student sex was significantly associated with REs (p < 0.01), with female students having a higher-than-expected prevalence (67.4%). Older and shorter students were more likely associated with REs (p < 0.05). Moreover, the statistical analysis revealed a significant association between the study level and the prevalence of REs (p < 0.05). Students in the premedical phase had a less-than-expected prevalence rate of REs (54.0%), while students in the clinical phase had a more-than-expected prevalence rate (72.5%) ( Table 1). The presence of a first-degree relative with REs was significantly associated with the prevalence of REs (p < 0.001), as most of the students who had a first-degree relative with REs (68.1%) had REs, while most students who did not have a first-degree relative with REs (80.4%) did not have REs. There were no significant associations between the use of electronic devices or the exposure to sunlight and the prevalence of REs among the medical students.

Nevertheless, a multivariate regression analysis model was generated to determine the true predictors of REs from the previously described risk factors. The model revealed that sex and the presence of a first-degree relative with an RE were the only two true predictors of the incidence of REs among medical students in the UAE ( Table 2). Female students had a more than 3-fold greater risk of developing REs than male students (p = 0.01). Additionally, students who had a first-degree relative with an RE had a 7.6-fold higher risk of developing REs than students who did not have one (p < 0.001).

Characteristics of the students with REs and distribution of the different types of REs

Table 3 presents the characteristics of the students with REs and the distribution of the different types of REs among the students. Most of the students with REs were females (80.1%), corroborating the previous finding that sex is a predictor of REs. Additionally, most of the students with REs (95.5%) had a first-degree relative with an RE, which also corroborates the previous results above. Most of the students with REs (83.1%) had exposure to sunlight for less than 3 h/day ( Table 3). However, this is considered a normal situation, taking into consideration the hot environment of the UAE. Similarly, most of the students without REs (108/127, 85.0%) had exposure to sunlight for less than 3 h/day.

Regarding the types of REs, myopia, with or without astigmatism, was the most frequent type among the medical students with REs (84.1%). This constitutes a myopia prevalence rate of 51.5% of the total sample (169/328). Twenty-four (12.0%) students had hyperopia with or without astigmatism. Only eight (4.0%) students had astigmatism alone, as most astigmatism cases (83 students, 41.3%) were associated with either myopia or hyperopia. Most students with REs (44.8%) had myopia or hyperopia within the range of 1–3 diopters, 26.9% had >3–6 diopters, 17.9% had <1 diopter, and 5.5% had >6 diopters. Regarding the age at diagnosis, approximately two-thirds of the students (67.6%) were diagnosed between 10 and 20 years. Only 4.5% of the students were diagnosed before the age of 5 years; 22.4%, between 5 and 10 years; 35.8%, between 10 and 15 years; 31.8%, between 15 and 20 years; and only 4.0%, above 20 years.

Most of the students with REs (155/201, 77.1%) used eyeglasses for correction. Out of the 201 medical students who had REs, only seven (3.5%) did not use any correction method. Eleven (5.5%) students underwent laser refractive surgery. A question was asked about why the students chose not to perform laser refractive surgery, and most of them (127/201, 63.2%) stated that they were thinking of doing it later. However, 29 students (14.4%) preferred other methods, while the other 26 (12.9%) were not candidates for laser refractive surgery.

Myopia versus hyperopia

The factors that might be associated with the type of REs (myopia or hyperopia) among medical students in the UAE are summarized in Table 4. Only the students’ heights and weights were significantly associated with the type of REs (p < 0.05). Taller students were associated with hyperopia, while shorter ones were more associated with myopia. Additionally, students with a greater body weight were associated with a higher prevalence of hyperopia, while those with a lower body weight were associated with a higher prevalence of myopia. However, the multivariate regression analysis, including all factors reported in Table 4, revealed that weight was the only predictor of the type of RE. Students with a higher body weight had a 1.175-fold higher prevalence of hyperopia than those with a lower body weight (p < 0.05). None of the remaining factors were significantly associated with the type of RE.