Visual acuity and refractive status of Omani students with refractive error in grades 1, 4 and 7: A retrospective cohort study.

BACKGROUND: The visual and refractive status were assessed for grade 7 students in seven governorates in Oman. The health records were reviewed to assess the rationale for their previous school-based vision screening.
METHODS: A representative sample of 7(th) grade students with a refractive error (RE) was examined by optometrists in 2012. Their compliance with spectacle wear was also reviewed. Each student's vision and refractive status in grades 1 and 4 were compared with the status in grade 7. Each student's use of eye care services between grade 4 and 7 was evaluated to determine the uptake of existing eye services for vision problems.
RESULTS: This study had 286, 7(th) grade students with RE (myopia [94%], hyperopia [4%] and astigmatism [>1D] [2%]). The types of RE between genders in each grade were not significant (P > 0.05). During their vision screening when they were in grade 4, 5 of 13 moderate myopes (>-2D to - 6D) and 3 of 4 high myopes (>-6D) were detected and managed. Ten students with moderate and high myopia were already using spectacles before they were screened in grade 7. The compliance for spectacle wear was 62% in grade 7. Between grades, 4 and 7, 140 (49%) students did not visit eye clinics or an optician.
CONCLUSIONS: Refractive services in grade 4 were an additional initiative from the eye health care systems in Oman to the actual World Health Organization recommendations of conducting vision screening and RE corrections at grade 7 and 10. However, this was not proved to be significantly effective in early detection, and even the uptake of eye care services by school children was also low.

Introduction

Visual impairment during childhood can affect overall development. Hence, the World Health Organization (WHO) recommended vision screening and refractive error (RE) services for schoolchildren at the ages of 12–13 years and 15–16 years of age.[1] Oman has a highly developed eye health care system through school health programs. For example, Oman adheres to the recommended WHO screening in addition to vision screening of 4th grade students.[2] However, grade 4 vision screening was not consistent with other school screening initiatives, and this unique initiative was posing some practical program management challenges. Although the screening is evidence-based, consistent with the expansion of eye care services in Oman, the rationale for grade 4 screenings needs to be re-evaluated.[3] Hence, we designed a study to generate evidence-based data from ongoing eye healthcare through school health programs. The objective of this study was to assess the level of visual impairment and RE in grade 7 students and compare their vision screening records to grades 1 and 4 screening to evaluate the benefit of grade 4 screenings. The compliance and uptake of existing eye care services between grades 4 and 7 were also evaluated.

Methods

The eye healthcare committee of the Ministry of Health, Oman approved this study. As this was operational research and part of eye healthcare service delivery at schools, verbal approval of school authorities was obtained, and consent of students was waived. Our study population comprised of students identified having RE during the grade 7 vision screening in seven governorates. Students who were absent during school visits or declined to participate in this study were excluded. This study was performed between January 2012 and September 2012.

To calculate the sample size, we assumed that a 5% prevalence of RE in 7th grade schoolchildren and in these children, during grade 4, the prevalence was 1%. To achieve 95% confidence and 80% power of the study, 285 children were required in grades 7, 4 and 1.[4] Of all schools in all governorates with grade 7 students with RE, 25% were randomly selected for inclusion in this study.

Health nurses in the schools, who were trained in eye screening, examined study participants. The Snellen illiterate “E” chart at 6 m was used for measuring the distance visual acuity (VA) of each eye. Students with spectacles and students whose vision improved with pinhole testing were reexamined by a school refractionist. The accommodative spasm was neutralized by fogging the eyes, objective refraction was performed with streak retinoscopy (Heine, USA). For students suspected with latent hyperopia and those complaining of eye strain, a cycloplegic refraction was performed using 1% tropicamide eye drops.[5] The students were retested after 48 h and a spectacle prescription was handed over to the school health authority. The screening data was maintained in his/her health record. These health records were reviewed to collect data on vision and refractive status when they were in grades 1 and 4. Procedures for vision testing and refraction in grades 1, grade 4, and grade 7 were similar. Students with visual impairment were graded for functional distance VA in the following manner: Mild visual impairment (VA <6/6 to ≥6/18), moderate visual impairment (MVI) (<6/18–6/60) severe visual impairment (<6/60–3/60), and blind (VA < 3/60).[6] The refractive status was defined as hyperopia, mild myopia (−0.25D to −2D), moderate myopia (>−2D to −6D), and high myopia (>−6D). Students who had their refraction between +0.25D and −0.25D was considered as emmetropic. Hyperopia was classified as any eye with a spherical equivalent of + 0.25D or greater. If astigmatism was <1D, the value was transposed to its spherical equivalent and added to the spherical value and then grade into different types of REs. If astigmatism was more than 1D, the eye was grouped as astigmatic myopia/hyperopia. The eye with worse vision and higher refractive status was used to classify student's visual impairment and RE.

The field staff inquired to the students about their visits to the eye clinic or optical shop in last 3 years. The student was also asked about the reason for noncompliance for spectacle wear.

The data were collected on a pretested form and after auditing, it was transferred to a Microsoft Excel; spreadsheet (Microsoft Corporation, Redmond, WA, USA). For univariate analysis, we used Statistical Package for Social Studies (SPSS 11; IBM Corp., New York, NY, USA). Frequencies and percentage proportion were calculated. The Chi-square and two-sided “P” value was used to compared with the rate of RE between genders for grades 1, 4, and 7. Children without RE in grades 1 and 4 grade were monitored for changes in vision or development of RE during the next screening.

Results

The study sample was comprised of 286 students. There were 186 (65%) females. Dhofar and North Batinah governorates comprised of 34% and 27% of the cohort respectively.

From the study sample, there were 239 emmetropes in grade 1. Data were missing for four students, and 43 students had RE (Hyperopia [3] + mild myopia [26], moderate myopia [1] and astigmatic myopia [13]). Of the 239 emmetropes in grade 1, there were 144 (60%) who remained emmetropic by grade 4. Data were missing for nine students and 86 (36%) developed RE. In grade 4, there were 70 students with mild myopia, six with moderate myopia, three with severe myopia eight with hyperopia and 46 with astigmatic myopia. By grade 7, all 286 students (the entire study sample) had RE. Mild, moderate and severe myopia was noted in 184, 14 and four students respectively. There were 13 hyperopes and 71 astigmatic myopes. The RE profile in all three grades is presented in Figure 1. Distance VA in all three grades is presented in Table 1.

Figure 1

Presenting vision of schoolchildren with refractive error in grades 1, 4 and 7

Table 1

Presenting distance visual acuity (in the better eye) of students in grades 1, 4 and 7

In grade 7, there were 5 of 13 moderate myopes and 3 of 4 high myopes from the 4th grade vision screening. Hence, RE was detected and managed at least 2 years earlier. All these cases had MVI. Of the 17 cases of newly detected moderate and severe myopia in the 7th grade, 10 were already using spectacles prescribed by an optometrist or ophthalmologist.

Between grades 4 and 7, 42 (14.7%) had visited a Ministry of Health eye clinic, 24 (8.4%) visited private optometrists and 80 (28%) visited both. Nearly half of participants did not seek assistance with an existing eye care service during this period.

There were 176 (61.5%) of students with RE, who were wearing prescription glasses in grade 7 (spectacle wear compliant). The parents of 170 (59.4%) students paid for spectacles and the Ministry of Education provided funds for six students. The parents of 108 (38%) participants felt that spectacles were not required for their children. Thirty-one (11%) children with spectacles received a prescription from optometrists at private optical shops.

The refractive status for males and females is presented in Table 2. The gender variation in RE between grades was not statistically significant (P > 0.05).

Table 2

RE in males and females students in grades 1, 4 and 7

Discussion

In this study of a vision and refraction screening program in Oman, we found that screening at grade 4 was not beneficial for detecting students with visual impairment and RE. The existing eye care service was accessible to students who had ocular symptoms due to RE between grades 4 and 7 grade. Although mild myopia and astigmatism developed in students between grades 4 and 7, visual impairment was not advanced enough to be noticed by parents or school health staff and teachers.

Our study was based on a well-established school screening program in Oman that has been in place since 1991 and is endorsed by international agencies for eye care.[78] Therefore, the study outcomes are less likely to be affected by observer and measurement bias. Since students with RE in grade 7 were randomly selected to represent the student population with RE, the study outcomes could be representative of the seven governorates of Oman. As this was a retrospective review of school records when the students in the study sample were in grade 1 (7-year-old records), some missing data were inevitable. Unfortunately, computerized school health records were implemented in 2011 in some governorates as a pilot project and then expanded to all over Oman in 2012. Hence, the records from grade 1 were not digitized at the time of this study that makes data retrieval more complicated. If all cases with missing data in grade 1 were considered to have some sort of RE, universal grade 4 vision screening would be even less justified.

Progression of myopia and determinants of myopia such as family history, the presence of myopia in younger ages and anthropometric measurements of school students have been previously identified.[91011] These factors can be used by school health nurses while screening grade 4 students to decide whom to screen for vision instead of universal vision screening.

We found very few students sought eye care services in 3 years despite nearby ophthalmic units or optometry outlets. This observation could be due to the nonsymptomatic nature of emmetropia and mild myopia. Additionally, school teachers and parents could be less aware of the signs of visual impairment and RE in children. Cost is not a factor in the low uptake of eye care services in Oman as eye care by ophthalmic units is available to all Omani citizens at <1 US$.

The compliance of spectacle wear among grade 7 students was 62%. In view of the proactive eye and vision screening in schools and provision of spectacles at a reduced cost, the uptake rate is considered low. The principle of healthcare screening is that early detection leads to the need for remedial action promptly.[12] VA <6/18 due to RE is a predictor of poor compliance with spectacle wear.[13] Thus, better counseling of students and parents regarding the need for spectacles and continual use for overall development of the child could improve compliance.

Eye care program staff often question what the optimal frequency is for eye care screening for schoolchildren. In resourceful countries such as Saudi Arabia, students undergo annual vision screenings.[14] The results of our study indicate that Oman's initiative of screening at grades 1, 4, 7, and 10 is perhaps too frequent. The WHO has recommended vision screening in grades 7 and 10 grade and providing refractive services to those with RE.[15] This recommendation seems to be the best option where eyecare services are easily accessible to the students when they have symptoms or are at high risk of developing severe RE within the two screenings. More frequent screenings will likely result in limited yield and may not be cost effective.

Conclusions

Vision screening and refractive services in grade 4 was an additional initiative to the WHO recommendation of screenings at grades 7 and 10. Grade 4 screenings had limited yield in Oman where eye services are available to students between grades 4 and 7. Lower compliance with spectacle wear among students with mild myopia is understandable. There was no significant variation in RE based on gender at different grades.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.