MINISTRY OF EDUCATION AND TRAINING
THAI NGUYEN UNIVERSITY
 VU QUANG DUNG

STUDYING THE SCHOOL MYOPIA STATUS AND
PREVENTIVE INTERVENTIONS FOR SECONDARY
STUDENTS IN MIDLAND REGIONS
OF THAI NGUYEN PROVINCE

Speciality: Sociological Hygiene and Health Organization
Code number: 62.72.01.64

PHD THESIS SUMMARY THAI NGUYEN, 2013

The work was completed in

LIST OF PUBLISHED PAPERS RELATED TO THESIS

1. Vu Quang Dung, Do Van Ham, Mai Quoc Tung, Vu Thi Kim Lien, Do Thi
Yen, Nguyen Manh Hung (2008), "Studying the status of school
sanitation in two junior schools in Thai Nguyen", the third International
Scientific Conference of Occupational Health and Sanitation, Hanoi, pp.
279-286.
2. Vu Quang Dung, Do Van Ham, Mai Quoc Tung, Vu Thi Kim Lien, Dang
Thi Tam, Nguyen Manh Hung (2008), "Initial studying on myopia in
junior students in Thai Nguyen", the third International Scientific
Conference of Occupational Health and Sanitation, Hanoi, pp. 287-296.
3. Vu Quang Dung, Do Van Ham, Mai Quoc Tung, Vu Thi Kim Lien, Do Thi
Yen, Nguyen Manh Hung (2008), "Studying the status of school
sanitation in two junior schools in Thai Nguyen", The seventh National
Occupational conferences, Medical Publishing, Hanoi, pp. 70.
4. Vu Quang Dung, Do Van Ham, Mai Quoc Tung, Vu Thi Kim Lien, Dang
Thi Tam, Nguyen Manh Hung (2008), "Initial studying on myopia in
junior students in Thai Nguyen", The report summarizes scientific,
scientific conferences nationwide Occupational Health Seventh, Medical
Publishing, Hanoi, pp. 71.
5. Vu Quang Dung, Do Van Ham, Mai Quoc Tung, Vu Thi Kim Lien,
Nguyen Manh Hung, Do Thu Trang (2008), "The studying of refractive
errors in school students in Thai Nguyen province", in the National
Ophthalmology Conference, Ho Chi Minh City, pp. 5.
6. Vu Quang Dung (2008), "The studying on functional tests and the
correlation with refractive school students in Thai Nguyen," Vietnam
Journal of Medicine, 351 (2), pp. 338-344.

1
BACKGROUND


1. Its is the opening study about myopia status and preventive measurements
in secondary school in Midlands of Thai Nguyen and the Northern Mountainous
region.
2. The study has built an intervention model: Combination of community and
clinical interventions are effective, practical benefits and feasible. It can be widely
applied to midland and mountainous region.
3. The study has identified a number of risk factors which associated with
school myopia that other authors have not mentioned in Vietnam such as an
association between myopia and light intensity in each location of the classroom;
the relationship between myopia and suitable and unsuitable furniture size;
relationship between myopia with outdoor playing time and myopia with family
history.
4. The study implemented solutions which combined health education and
treatment intervention for preventing school myopia. These interventions are
feasible and are accepted by the community.

THESIS STRUCTURE

The thesis contents 121 pages, including the following parts:
Introduction: 2 pages
Chapter 1 - Overview: 31 pages
Chapter 2 - Subjects and Methods: 18 pages
Chapter 3 - Research results: 39 pages
Chapter 4 - Discussions: 28 pages
Conclusions and Recommendations: 3 pages
The list of published articles: 1 page
And 148 references, including 66 Vietnamese and 82 English.
The thesis has 41 tables and 5 charts and 4 diagrams.
The appendix includes 9 appendixes in 37 pages.

- The risk factor of family characteristics, congenital and hereditary: family
history has people with myopia.
- The risk factor of school sanitation and hygiene practices: lack of lighting,
over or under size of tables and chairs, incorrect practices in learning hygiene.
4
- The risk factors of near vision prolongation: high-intensity learning,
learning pressure, playing game, less time for far looking, less outdoor activities
and limited vision.
- The risk factor of school myopia prevention is not good enough: the
awareness of eye care in schools is not enough attention, the quality of medical
activities is insufficient, most students do not have routine eye exam, week
cooperation between sectors and levels of work-related health care for students.
- Some other risk factors: lack of sleep, nutrition, ethnic groups and
educational level. The lack of understanding of myopia, risk factors and
preventions is also an important factor contributing to the increased incidence and
severity degree of myopia.
1.3. Some solutions to prevent myopia school
There have been many studies and prevention measures for school myopia in
the world and Vietnam. There are three stages in intervention to prevent school
myopia; however, in most localities in our country only implements Phase 1.
Currently, Vietnamese eye institute actively deploys interventional activities in
Phase 2. Many provinces have actively implement school myopia preventive
activities such as Hanoi, Ho Chi Minh City, Hai Phong, Nam Dinh, Ninh Binh,
Thai Nguyen, Hue, Da Nang, Ha Tinh These activities has received support and
facilitate of the ministries and society.
Many local and international organizations have supported for school
myopia prevention and intervention by positive activities such as Rang Dong
Corporation (RALACO), the Vietnam Urban Lighting , the Vietnam education and
health care communities, school equipment companies in Vietnam, Project
Management of Public Lighting in Vietnam (VEEPL), the World Health

n
Z
ε
α
−
=
−

The sample size was calculated at 95% confidence level, the relative
accuracy ε = 0.1 and p = 17.42%. n = 1,822, in fact, this study was conducted on
1.873 students. On average, each secondary school in Thai Nguyen province of has
about 450 students, therefore the number of schools should investigate are 4
schools. The schools are selected in a random method. Results of the random
selection are: Tan Thanh, Phu Xa, Quyet Thang, Hoa Thuong.
* Sample size for case-control studies:
- Sample size:
[
]
{
[
]
}
[ ]
2
2
*
211
)2/(
2
)1(

17.42% and desire to reduce to 7.5% with α = 0.05, β = 0.2. The sample size for
each group are 173 students.
Due to the intervention study is conducted in 2 years, to ensure that studied
subjects are continually monitored, this study is conducted on students grade 6 and
7 of the secondary schools, then randomly assigned 2 schools in the intervention
group and 2 schools in the control group by lottery method, the results are as
follows:
- Intervention group 1 (community intervention): students grade 6 and 7 of
Tan Thanh secondary school.
- Interventions group 2 (community combined treatment intervention):
students grade 6 and 7 of Phu Xa secondary school.
- Control group: students grade 6 and 7 of Quyet Thang and Hoa Thuong
secondary school.
As student’s grade 6 and 7 of those schools are more than calculated sample
size therefore all students were selected in the sample.
2.3.3. Content intervention
2.3.3.1. Intervention 1: Community intervention
- Forming the working group of myopia prevention in the interventional
schools.
- Communicating information on school myopia, myopia prevention
measures for students, parents and teachers.
2
21
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qpqpZZ

- Percentage of students already had glasses before investigated and the incident of
myopia.
* Risk factors for schools myopia:
- Classrooms’ sanitation: lighting system, lighting intensity, chalk board size and
the size of tables and chairs.
- The relationship between light intensity with school myopia.
- The relationship between the size of chairs and school myopia.
- The relationship between learning posture and school myopia.
- The relationship between the home learning place and school myopia.
- The relationship between the intensity of class learning and home learning and
school myopia.
8
- The relationship between the times spent on leisure activities with near vision and
school myopia.
- The relationship between the knowledge of students and parents and school myopia.
- The association of family history and school myopia.
- The relationship between school health activities with school myopia
* Effectiveness of interventions:
- The number of sessions that students and parents were communicated about
school refraction.
- The number of classrooms were repaired Ergonomics.
- The number of students worn glasses and taken medication to prevent myopia
progression.
- The ratio of myopia before and after the intervention in the intervention group 1,
2 and control groups.
- The incidence of school myopia in intervention groups 1, 2 and control groups.
- The degree of myopia and progression of myopia between the intervention groups
1, 2 and control groups: decreased, stable or increased in dioptre.
- The efficiency and effectiveness of the intervention measurements, comparisons
between the intervention and non-intervention.

point. Based on the cut off 75% of the total score, divides practical knowledge into
2 levels: Good: ≥ 75% of the total points; Not good: < 75% of the total points.
2.4.4. Observation:
To observe student learning posture and assess as follows:
- Low head bowed: The distance from the eye to notebook less than 25 cm.
- Correct sitting posture: The distance from the eye to notebook ≥ 25 cm.
2.4.5. Discussion group:
Forming 3 focus groups of administrators, school health personnel,
representative of head teachers and representative of parents that discuses in focus.
2.4.6. Monitoring interventions
Intervention activities are monitored directly by PhD fellow, monitoring
monthly and when the school organizes media communication and parent meetings.
2.5. Methods of data processing:
SPSS 18.0 software with algorithms biostatistics is used in this study. The
results which compared before and after intervention are tested statistically (p
<0.05) and evaluated by effective indicators and interventional indicators.
2.6. Measures to control error
Avoid using subjective methods to diagnose myopia in order to avoid false
myopia cases. Using autorefractor identifies myopia.

10
Chapter 3. FINDINGS
3.1. The situation of school myopia in secondary school in Midlands region of
Thai Nguyen province
Table 3.3. The rate of school myopia in 4 schools.
School No students

No myopia
students
% p


11
Table 3.6. Distribution of myopia student by the time investigated
Secondary school
Number
myopia
students
Myopia already had
glasses
New incident case

N % N %
Phu Xa 95 41 43.2 54 56.8
Tan Thanh 84 41 48.8 43 51.2
Quyet Thang 51 25 49.0 26 51.0
Hoa Thuong 85 38 44.7 47 55.3
Total 315 145 46.0 170 54.0
Comment: Of those myopia students, only 46.0% of myopia students knew they
had myopia and worn glasses, 54% of myopia students just discovered when
examination.
Table 3.8. Degree of myopia
Degree
Right eye Left eye
N % N %
<-1.00 D 38 12.1 45 14.3
-1.00 to < -3.00 D 227 72.1 216 68.6
≥ -3.00 D 50 15.8 54 17.1
Comment: Most students had medium myopia (between -1.00 to -3.00 D). Rate of
high myopia in the right eye was 15.8% and the left eye was 17.1%.
Table 3.9. Visual acuity of myopia students

Average

164.33 ±46.15 58.84 ±22.91 124.80 ±43.18 292.53±164.26 162.94±119.93
Comment: The light illumination in classroom was the lowest in Tan Thanh
secondary school and did not reached the standard (> 100lux). Other schools had
standard of illumination, especially grades 7 of Hoa Thuong Secondary School.
Table 3.12. Relationship between light illumination and school myopia
Refractive status

Light illumination
Myopia
(n=240)
Emmetropia
(n=480)
Total
(n=720)

OR
(CI95%)
Under standard (<100 lux) 123 134 257
2.7
(1.9-3.8)
Standard (>100 lux) 117 346 463
Total 240 480 720
Comment: There was an association between light illuminations at learning sitting
and school myopia students. Not enough light illumination in learning area was risk
for school myopia 2.7 times.

Chart 3.2. Correlation between light intensity and school myopia
Comment: There was a negative correlation between light intensity and school

Table 3.14. The correlation between the size of tables and chairs and school myopia
Refractive Status

Tables/chair size
Myopia
(n=240)
Emmetropia
(n=480)
Total
(n=720)

OR
(CI95%)
Suitable 172 304 476
1.5
(1.1-2.1)
Unsuitable 68 176 244
Total 240 480 720
Comment: Unsuitable tables and chairs was the risk factor for school myopia 1.5
times higher.
Table 3.15. The relationship between learning posture and school myopia
Refractive Status

Learning posture
Myopia
(n=240)
Emmetropia
(n=480)
Total
(n=720)


8

3
.
00 ± 0
.
00

1
.
30 ± 0
.
00

0
.
80
± 0
.
00

Hoa Thuong

13

3
.
20 ± 0
.

(n=720)
OR
(CI95%)

Presence 16 29 45
1.1
(0.6-2.2)

Absence 224 451 675
Total 240 480 720
Comments: There was no known relationship between the presence or absence
home learning location and school myopia.

Table 3.18. The relationship between type of learning tables and chairs and
lighting at home with school myopia
Tables and chairs
and lightings
Myopia
(n=240)
Emmetropia
(n=480)
p
(test χ
2
)
n % n %
Type of table and chair
Table attach chair 57 23.8 95 19.8 >0.05
Table separate chair 158 65.8 366 76.3 <0.05
Study on bed 15 6.3 18 3.8 >0.05

over 5 hours 17 7.1 15 3.1 3.2 1.5-7.1
Note: * The variable reference
Comment: There was a closely correlation between time for self study and additional
study and myopia. Long time studying was highly risk for myopia.
Table 3.21. The relationship between time for looking near distance and myopia
Looking near distance
activities
Myopia
(n=240)
Emmetropia
(n=480)
OR CI95%
n % n %
Reading stories/books
0- less than 2 hours* 194 80.8 429 89.4 1.0
2 less than 5 hours 46 19.2 51 10.6 1.9 1.3-3.1
over 5 hours 0 0 0 0.0 -
Using computers
0- less than 2 hours* 196 81.7 475 99.0 1.0
2 less than 5 hours 44 18.3 35 7.3 2.8 1.7-4.7
over 5 hours 0 0 0 0.0
Playing computer games
0- less than 2 hours* 187 77.9 444 92.5 1.0
2 less than 5 hours 50 20.8 34 7.1 3.5 2.1-5.7
over 5 hours 3 1.3 2 0.4 3.6 0.5-30.7

Watching televisions
0- less than 2 hours* 172 71.7 427 89.0 1.0
2 less than 5 hours 65 27.1 52 10.8 3.1 2.0-4.7
over 5 hours 3 1.3 1 0.2 -

Not good 96 39.8 146 30.4
1.5 1.1-2.1
Good 144 60.2 334 69.6
Comment: Students with not good knowledge on school myopia was risk for
myopia 1.8 times than those who had good knowledge; parents with not good
knowledge, their children were risk for myopia 1,5 times more than those who had
good knowledge.
3.2.5. Some other risk factors
Table 3.25. The link between family history and school myopia school
Refractive statusFamily history
Myopia
(n=240)
Emmetropia
(n=480)

OR CI95%

n % n %
Myopia 21 8.7 19 4.0
2.3 1.2 - 4.6
Emmetropia 219 91.3 461 96.0
Comment: The family having myopia relatives (parents, grandparents, siblings)
was risk for myopia 2.3 times than those their relatives had no myopia.
Table 3.26. School health activities in secondary schools

Sessions No people Sessions No people
School myopia and other
related disease
2 861 2 1159
Cause and risk factors for
school myopia
2 865 2 1152
School myopia preventions

3 869 3 1156
Self test visual acuity and
practices for eye
2 442 2 525
Guideline for wearing
glasses
2 845 2 1154
Communication in parents’
meting
2 435 2 546
Total 13 4.317 13 5.692
Comment: In each school intervention, 13 communication sessions was held
for students and parents about school myopia, risk factors and preventions. The
total number of listeners in Tan Thanh Secondary School was 4,317 and 5,692 in
Phu Xa respectively.

18
Table 3.28. Results of intervention in classes sanitary conditions at 2
interventional schools
Number of classroom
had sanitary

withdrawn from the trial (5.3%). Students complying correctly guide was 74.7%.

3.3.2. Effectiveness of myopia school interventions.
In order to follow ongoing school myopia in 2 years, this study used the
initial examination results of students in grades 6, 7 and re-examined these students
in grade 8, 9 to calculate effectiveness of the interventions.

19

Chart 3.3 Comparison of changes in students' knowledge between the 2
intervention groups after 2 years
Comment: Knowledge of students in the two intervention groups was significantly
changed to compare with before intervention (approximately more than 50%) and
there were no difference between community intervention and community and
clinical combination.

Chart 3.4. Comparing the change in students' practice between 2 intervention
groups after 2 years
Comment: Myopia risk behaviors were declined similarly in the 2 groups, but the
behavior of eye protection in intervention group 2 tended to better than intervention
group 1.

20
Table 3.36. The ratio of myopia before and after intervention
Before Ater Difference p
(test χ
2
)
n % n %
Intervention

myopia in the control group tended to increase from 11% - 12% after 2 years.
Table 3.37. Compare the progression of myopia between intervention and
control groups
Intervention
school
*

Control
school
**
p
(test χ
2
)
n % n %
Intervention
group 1
Myopia degree reduce 10 29.4 2 5.6 <0.05
Myopia degree stable 13 38.2 9 25.0 >0.05
Myopia degree increase 11 32.4 25 69.4 <0.05
Intervention
group 2
Myopia degree reduce 16 44.4 1 5.9 <0.05
Myopia degree stable 14 38.9 4 23.5 >0.05
Myopia degree increase 6 16.7 12 70.6 <0.05
Notes: * School intervention: Tan Thanh school: 34 myopia students; Phu Xa school: 36 myopia students
** Control school: Hoa Thuong school: 36 myopia students; Quyet Thang school: 17 myopia students
Comment: Most of the students in the control groups (both intervention 1 and
intervention 2) had myopia degree increase after 2 years (69.4% and 70.6%). In the
intervention group 1, students with myopia degree increase was only 32.4%, the rest

Note: * Number of students without myopia at baseline (2006)
Comment: The incidence ratio of myopia in the intervention groups’ was lower
than the control groups. Cumulative incidence in 2 years was the lowest (4.2%) in
the community and clinical intervention (intervention group 2) and 6.2% in the
community intervention group (intervention group 1). The incidence in control
group was 9.4% and 11.6% respectively. The significant difference was in the
intervention group 2 with p<0.05.
Table 3.41. Effective interventions for school myopia
Effective
indicator
(intervention)

Effective
indicator
(control)

Effective
intervention
indicator (%)
Intervention group 1

24.8 -75.5 100.3
Intervention group 2

38.0 -120.9 158.9
Comments: Effective intervention indicator in intervention group 1 (community
intervention) was 100.3%. It was lower than the intervention groups 2 (community
and clinical intervention).
Chapter 4. DISCUSSIONS
4.1. The situation of school myopia in secondary schools in Midland regions of

to increase from 11% - 12% after 2 years. Cumulative incidence in 2 years was the
lowest (4.2%) in the community and treatment intervention group (intervention
group 2), followed by community intervention group (6.2%) (intervention group 1).
The incidence in control groups were 9.4% and 11.6% respectively. The noticeable
difference was in the intervention group 2 with p <0.05. In the intervention groups,
the progression of myopia was significantly slower than the control groups.
Effective intervention of intervention group 1 (community intervention)
(100.3%) was lower than intervention group 2 (158.9%). (community and treatment
intervention). Effective intervention of the intervention group was significant
because the ratio of myopia was not only increase but also decreases. Unlikely, in the
control groups, after one year, the incidence of school myopia have increased
significantly. Effective interventions had a positive impact on limiting the increase of
school myopia in interventional school by both the incidence and ratio of myopia.