nghiên cứu thực trạng và một số giải pháp phòng chống cận thị ở học sinh trung học cơ sở khu vực trung du tỉnh thái nguyên bản tóm tắt tiếng anh

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

College of Medicine and Pharmacy - ThaiNguyen University


Scientific supervisor:
1. Assoc. Prof. Dr. Hoang Thi Phuc
2. Prof. Dr. Do Van Ham

Defender 1:



Defender 2:



Defender 3:
.

The thesis will be defended at the National level by the Board of
examiners in College of Medicine and Pharmacy - Thainguyen University in
September 2013





Thesis can be found at:
National Library
Resource Center ThaiNguyen University
Library of ThaiNguyen College of Medicine and Pharmacy

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

School myopia is increasing in many countries around the world as well as in
Vietnam. According to Kovin Naidoo (ICEE International Center for Eye Care
Education), in 2020, the refraction and glasses account for 70% of the global
population (5.3 billion people). In which myopia is 33% (3 billion people).
Currently, Asia has the highest incidence of school myopia in the world. In China
(2006), there are more than 300 million people with myopia. A study in India
(2003) showed that 13% of blindness and 56% of people had visual impairment due
to myopia. Thus, the program "Vision 2020" the World Health Organization ranked
school myopia is one of the five causes of blindness in the prevention programs
worldwide.
According to the investigation of many researchers recently, myopia is
increasing rapidly and it is the main cause of vision loss in Vietnam and other
regional countries. In Ho Chi Minh City (2006), published by Le Thi Thanh Xuyen
showed the percentage of myopia students increased alarmingly. The rate of
myopia was 8.65% in 1994 up to 17.2% in 2002 and 38.88% in 2006. According to
a research by the Institute of Educational Sciences of Vietnam (2008), the
prevalence of school myopia was high with an average of 26.14% of the total
student’s population.
There have been many studies on school myopia so far in both cities and
rural areas in many provinces around the country. However, there are no in-depth
studies of school myopia in the Midland regions of the Northern Mountains. Based
on the existent situation and concern for school myopia prevention, this study is
undertaken with the aims:
1. To describe the situation and identify a number of risk factors for school
myopia in secondary schools in midland regions of Thai Nguyen province in 2006.
2. To assess the effectiveness of preventive interventions for school myopia
for 2 years (2006-2008).
2
CONTRIBUTIONS OF THE THESIS

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.

3
Chapter 1. OVERVIEW
1.1. Status of school myopia recently.
1.1.1. The concept
School myopia (nearsightedness) is acquired in school ages. Degree of
myopia ≤ - 6.00D. Myopia is caused by the asymmetric axial length and the eye's
optical power that makes light come in front of the retina. The eyeball axial length
and focusing power increase lightly and often has no pathological lesions (retinal
degeneration, cornea, sphere lens…).
Evaluation school myopia: there are various methods of determining the
school myopia: subjective test (Dondes), retinoscope and autorefractor. This study
uses autorefractor: Eyes are regarded as myopic when measured by the
autorefractor after reducing accommodation is ≥ - 0.50 D.
1.1.2. Status of the current school myopia.
Issue on school myopia has studied only around 70 years of the nineteenth
century. Earlier, myopia was considered a genetic disease and malignant
progression, therefore myopia was considered a disease without prevention and
treatment. The World Health Organization estimates that there are 2.3 billion
people have refractive errors nowadays. In which myopia is the first reason for
vision loss and blindness (greater 2 times than the blindness caused by cataracts).
In Vietnam, school myopia is a public health concern because of a large number of
people has myopia which affected their learning, quality of life and social -
economical development. Approximately 15% to 20% of students in urban schools
have myopia and even it is higher in some big cities. A research in 16 schools in
2008 in Thai Nguyen showed that the rate of myopia accounted for 73.09% of total
refractive error. The prevalence of school refractive in the city is 16.48% and
6.11% in rural areas.
1.2. The risk factors of school myopia
There have been many studies on the risk factors leading to school myopia.
Factors can be classified into risk groups as follows:

- 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

Organization (WHO ), the Organization for International Prevention of Blindness
(IAPB), the UN Children's Fund (UNICEF), Christoffel Blindenmission
Organization (CBM), the Atlantic Philanthropies (AP), the Fred Hollows
Foundation (FHF), The First Sight, ORBIS International (OI)
5
Chapter 2: SUBJECTS AND METHODS
2.1. Subjects
Secondary students in Midlands region of Thai Nguyen, parents, secondary
school administrators, head teachers, school health personnel, facilities and sanitary
conditions of school: tables, chairs, light
2.2. Time and place of study
- Study period: from 11/2006 to 12/2008.
- Location of research: the study was conducted in four schools in the midland
regions of Thai Nguyen province including: Phu Xa, Tan Thanh, Quyet Thang, Hoa
Thuong secondary schools.
2.3. Research methodology
2.3.1. Study Design: Using 3 types of research design as follows:
- Descriptive studies, cross-sectional design to determine the rate of school myopia.
- Case-control study to identify a number of risk factors for myopia in secondary
school students.
- Intervention study with community and clinical intervention.
2.3.2. Sample size and sampling technique
* Sample size for the descriptive studies:
2
2
)2/1(
).(
)1(
p
pp

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(

)1(/1)1(/1
ε
α
−
−+−
=
∗∗∗
In
PPPP
Zn

The sample size is calculated based on the percentage of students with low
bowed head when learning. It is estimated for the control group 20% and OR = 2
with the expected accuracy of the OR was 0.35. As the sample size for each group
are 223 students, rounded to 240 students. Select the ratio of case/control is 1/2.
Thus the sample size for case groups are 240 students and the control group are 480
students.
6
The case group inncludes students identified as myopic from -0.50 D to ≤-
6.00D as measured by autorefractor after dropping cyclogyl. Using single
randomized method selects 240 students from the list of myopia students of
descriptive study.
Control group includes students with normal health status; emmetropia,
similar to the case group on age, sex, school and class grade following the rate: 1
case and 2 controls.
* Sample size for the study intervention:

- Sample size:

The sample size is calculated based on the estimated the ratio of myopia

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
2211
2
12/1
)(
)()(
pp
qpqpZZ

n
−
++
=
−−
βα
7
- Fixing Ergonomics: discussing how to fix, set up the standard of furniture, lighting,
chalk board Mobilizing the contribution of parents to ensure hygiene in learning.
- Medical intervention: the head of schools together with leaders of the local to
strengthen and promote the school health department and local health services for
early detection of school myopia.
2.3.3.1. Intervention 2: Community and clinical interventions
Conclude the intervention 1 following measures:
- Wearing glasses: guiding myopia students used correct glasses and appropriate
time to wear (wearing glasses when looking up the chalk board, while traveling;
put off glass when using near eyesight)
- Medications:
+ Reduce accommodation: using Cyclogyl 1% or Cyclopentolat eye drops once a
day at bedtime.
+ Using drugs to prevent the progression of myopia: using 4-6 bilberry tablets
(cranberry extract and vitamin E) per day, 15 days per month for 2 years.
+ Using eye drops to reduce accommodation: solution Correctol 2% x 4 times daily.
- Guiding the parents and students added vitamin A from foods in their diet daily.
2.3.4. The study variables
* Status of school myopia:
- The rate of myopia by school, grade (grade 6,7,8,9), by gender.
- Percentage of students with visual impairment in levels: reduced, decreased or blind.
- Percentage of students with mild, moderate and severe myopia.
- Percentage of myopia in one or two eye.

- 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.

2.4. Methods of collecting information
2.4.1. Diagnose for myopia
- Test visual acuity using Landolt chart: test all students to identify students with
visual impairment. Assessment the visual acuity by the classification of the World
Health Organization:
+ Visual acuity above 7/10: Normal
+ Visual acuity from 3/10 to 7/10: Decrease
+ Visual acuity from count finger at 3m to VA 3/10: Highly decrease.
+ Visual acuity <cont finger at 3m: Blind
- Diagnoses myopia: the students had visual impairment examined by autorefractor
with cyclogyl 1% eye drop. Eyes are regarded as myopic as myopia degree above
0.50D when measured by autorefractor after dropping cyclogyl.
2.4.2. Measuring classroom’s hygiene index:
- Illuminate coefficient is evaluated based on "Regulations on school hygiene" by
the decision No 1221/2000/QD-BYT of the Minister of Health issued 18 April
2000: The total lighted area is not under one fifth of classroom area.
9
- The intensity of illumination in the classroom: measured by Luxmeter made in
Japanese. Evaluated criterion: 100-300 lux: standard, <100 lux: under standard.
- Tables and chairs dimensions: measuring the height, length and width of tables
and chairs with millimeters. Then the difference between tables, chairs and
student’s build are compared.
- Dimension of chalk board and on high hanging: the length and width of chalk
board and the length hanging up are measured.
2.4.3. Interview:
Students and parents are direct interviewed by questionnaires about the intense
of learning, time for leisure activities with near vision such as reading, watching
television, playing video games and knowledge of school myopia and preventive
measurements. Knowledge of students and parents are evaluated based on the
correct answers on the questionnaire form, each correct answer is counted as 1

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

Phu Xa secondary school 573 95 16.6

>0.05
Tan Thanh secondary school 441 84 19.1
Quyet Thang secondary school 371 51 13.8
Hoa Thuong secondary school 488 85 17.4
Total 1.873 315 16.8
Comment: There was no significant difference in the ratio of myopia among 4
investigated schools (p> 0,05). School myopia rate was 16.8% on average.
Table 3.4. The rate of school myopia following class grade
Class grade Number students
investigated
Number myopia
students
%
Grade 6 457 65 14.2
Grade 7 468 58 12.4
Grade 8 467 93 19.9
Grade 9 481 99 20.6
p (test
χ
2
) <0.001
Comment: myopia rate in grade 6, grade 7 was lower than grade 8, grade 9. School
myopia rate in grade 7 was the lowest (12.4%), the highest myopia rate was in
grade 9 (20.6%), the difference was statistically significant with p <0.001.

Chart 3.1. Myopia rate by gender and by class grade
Comment: In all surveyed schools, the percentage of myopia in female
students was higher than male students.

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

Visual acuity
Right eye (n=315) Left eye (n=315)
N % N %
> 7/10 8 2.5 11 3.5
> 3/10 - 7/10 209 66.4 204 64.8
CF 3m - 3/10 92 29.2 94 29.8
< CF 3m 6 1.9 6 1.9
Comment: Most myopia students had mild visual acuity (visual acuity from 3/10 to
7/10). There were 19 students had one eye nearsighted vision but the visual acuity
of other eye were > 7/10. Nearly 30% of myopia students had decreased highly
visual acuity (CF3m - 3/10), especially, there were 6 myopia students (1.9%)
considered to be blinded as the visual acuity classification of World Health
Organization.


12
3.2. Risk factors for school myopia in secondary students.
3.2.1. Classrooms’ sanitation.
Table 3.11. Average light illumination in the secondary schools (Lux)
Phu Xa Tan Thanh

Quyet
Thang
Hoa Thuong

Average
Grade 6 190.78 ± 50.36 65.10 ±30.36 101.53 ±22.09 326.57±125.43 172.52±116.96
Grade 7 190.78±50.36 45.27 ±14.22 101.53±22.09 71.37 ±51.36 109.05±69.29
Grade 8 137.88 ±30.38 44.33 ±6.47 148.07±54.91 391.90±108.10 177.26±139.11
Grade 9 137.88±30.38 80.67±18.87 148.07±54.91 358.35±148.90 190.79±136.26

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

myopia (r = -0.66). The more light intensity increases, the less school myopia.
myopia (%)

13
Table 3.13. Effect of average height tables and chairs in the Secondary School (cm)
Phu
Xa
Tan
Thanh
Quyet
Thang
Hoa
Thuong
Total Standard

Grade 6

32.0±0.0 31.0±0.0 32.0±0.0 30.0±0.0 31.3±0.9 23
Grade 7

32.0±0.0 31.33±0.58 32.0±0.0 29.67±0.58 31.3±1.0 23
Grade 8

32.0±0.0 31.0±0.0 32.0±0.0 30.0±0.0 31.3±0.9 25
Grade 9

32.0±0.0 31.0±0.0 32.0±0.0 30.0±0.0 31.3±0.9 28
Total 32.0±0.0 31.0±0.43 32.0±0.0 29.69±0.85 31.2±1.1
Comment: Performance of tables and chairs between schools and classes grades
were similar. It is beyond the standard: high tables and low chairs.

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)

OR
(CI95%)

Low bowed head (<25cm) 115 151 266
2.0
(1.4-2.8)

Correct learning posture 125 329 454
Total 240 480 720
Comments: Those students who often bowed head low were risk for school myopia
2 times than correct posture.
Table 3.16. The dimensions and hanging chalkboard in surveyed schools

Secondary school
N The length
(m)
The width
(m)
Distance above
floor (m)
X
± SD
X
± SD
X
± SD
Phu Xa 8 3.00 ± 0.70 1.20 ± 0.00 0.60 ± 0.00
Tan Thanh 12 3.00 ± 0.00 1.30 ± 0.00 0.80 ± 0.00
Quyet Thang

8

3
.
00 ± 0
.
00

1
.
30 ± 0
.
00

0
.
80
± 0
.
00

Hoa Thuong

13

3
.
20 ± 0
.

30

1
.
20 ± 0
.
30

0
.
70 ± 0
.
00

Comment: The dimension of chalkboard was nearly similar between schools and
class grade and satisfied hygiene classes, however, hanging chalk board of Phu Xa,
Hoa Thuong Xa schools was incorrect, lower than standard regulations.

14
3.2.2. Learning conditions at home

Table 3.17. The correlation between the home learning place and school myopia
Myopia status

Home learning location
Myopia
(n=240)
Emmetropi
an=480)
Total

(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

Handmade 10 4.2 1 0.2 >0.05
Lightings
Fluorescent Lamps 77 32.1 191 39.8 <0.05
Hair Lamps 62 25.8 105 21.9 >0.05
Table lamps 101 42.1 184 38.3 >0.05

Comment: Most of students had learning table and chair separate at home. In
myopia groups, table separate chair (65.8%) was lower than emmetropia group
(76.3%). Especially, there were 6.3% of myopia students regularly learning on the
bed. Also, artificial lighting fluorescent lamps was lower in myopia group than
emmetropia groups with p <0.05.

15
3.2.3. The intensity of student learning
Table 3.20. The relationship between home study and extra study with myopia
Time for self study and
additional study
Myopia
(n=240)
Emmetropia
(n=480)
OR CI95%
n % n %
Time of self study
0- less than 2 hours* 63 26.3 224 46.7 1.0 -
2 less than 5 hours 151 62.9 231 48.1 2.5 1.8-3.6
over 5 hours 26 10.8 25 5.2 3.7 1.9-7.2
Time of additional study
0- less than 2 hours* 118 49.2 335 69.8 1.0 -
2 less than 5 hours 105 43.8 130 27.1 2.3 1.6-3.2

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 -

16
Comments: Read stories/books, using computers, playing computer games and
watching television with duration over 2 hours/day were firmly association with
myopia.
3.2.4. Knowledge of school myopia of students and parents.
Table 3.23. The relationship between students and parents knowledge with
school myopia
Refractive status


Knowledge
Myopia
(n=240)
Emmetropia
(n=480)

OR



CI95%


n % n %
Students
Not good 138 57.3 209 43.6
1.8 1.3-2.4
Good 102 42.7 271 56.4
Parents

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 status


Family 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

School health activities Number
School health personnel work full time 0
School health personnel work part time 4
Organized propagation of prevention school myopia 3
Annually health examination for students 4
Plan to build and repair schools annually flowing to Ministry of
Health standards of school hygiene.
2

17
Comment: There was no school health personnel worked full time in 4
schools, only had school health personnel worked part time. 4 schools had annually
communication and examination. Only two quarters had planned to build and repair
schools annually according to the school hygiene standards of Ministry of Health.
Results of group discussion gave a number of difficulties in school hygiene
activities and school myopia:
- Lack of funds to repair and renovate schools.
- Lack of specialized staff on school sanitation.
- Insufficient knowledge of the disease and prevention measurements.
- Lack of the necessary media communication.
3.3. The effective interventions to prevent school myopia.
3.3.1. Results of interventions to prevent school myopia.
Table 3.27. The result of media communication in the 2 intervention

Content in
communication
Tan Thanh school
(intervention 1)
Phu Xa school
(intervention 2)

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

improvement
Tan Thanh school
(intervention 1)
Phu Xa school
(intervention 2)
n Standard (%) n Standard (%)
Classrooms were fitted
with lights to ensure
sufficient light (>100lux)
12 100.0 8 100.0
Classrooms with the right
light regulations.
12 100.0 8 100.0
Classrooms hanged chalk
board in standard
regulations.
0 100.0 8 100.0
Classrooms had tables and
chairs to be repaired or
replaced
50 100.0 35 100.0
Comment: 100% classrooms in 2 interventional schools reached school sanitary
standard after repairing or replacing of furniture, tables, and lights.
Table 3.29. Intervention results of using medicine and wearing glasses
Clinical intervention n %
Number of students using medicine 95 100.0
Number of students complying correctly guide 71 74.7
Number of students complying un correctly guide 19 20.0
Number of students withdrawing guide 05 5.3
Comment: Of those 95 students were attended clinical interventions, 5 students

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

group 1
Tan Thanh
(Intervention)
34 16.1

24 12.1 -4.0
>0.05
Hoa Thuong
(Control)
36 15.9

57 27.9 12.0
<0.05
Intervention
group 2
Phu Xa
(Intervention)
36 12.1

22 7.5 -4.6
>0.05
Quyet Thang
(Control)
17 9.1 36 20.1 11.0
<0.05
*Intervention group 1: community intervention (before: n = 211, after: n = 198)
Intervention group 2: community and clinical intervention (before: n=298, after: n = 296)
Comments: The ratio of myopia in 2 intervention groups were reduced, in which
the community and treatment combination were reduced higher than the
community intervention only (4.6% compared with 4.0%). In contrast, the rate of

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

students had myopia degree stable or reduced. Interventions group 2, the progression
of myopia is slowly than the intervention group 1, 44.4% of students had myopia
degree reduce, only 16.7% of students had myopia degree increased (p <0,05).

21
Table 3.40. Compare the rate of cumulative incidence of myopia in 2 years in
the intervention and control groups
No of
students*

No of
incidence
Ratio of
incidence

p
(test χ
2
)

Intervention
group 1
Tan Thanh 177 11 6.2
>0.05
Hoa Thuong 191 18 9.4
Intervention
group 2
Phu Xa 262 11 4.2
<0.05
Quyet Thang 172 20 11.6

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

Thai Nguyen province
In Vietnam and other countries in the region, school myopia is a special
concern and became a public issue of Ophthalmology. Recently, school myopia
rate in Vietnam accounts for about 10-20% of secondary school students. This rate
is equivalent to other Asian countries such as Thailand, Malaysia, lower than
China, Taiwan, Japan; it is higher than Laos, Cambodia and Mongolia. The results
of our study showed that the average ratio of myopia school is 16.8%, highest in

22
Tan Thanh secondary school (19.1%) and lowest Quyet Thang secondary school
(13.8%). The ratio of school myopia in our study is similar with other studies.
Table 4.2. Compare the school myopia ratio in the midlands of Thai Nguyen
province with other studies in Vietnam
Location Authors Year (%)
Ha Noi HaNoi eye institution 1994 4.75
Ha Noi Ha Huy Tien 1998 16.32
Ha Noi Ha Huy Tien 1999 22.52
Ha Noi Trinh Bich Ngoc 2009 25.5
Ho Chi Minh HCM eye institution. 1994 9.75
Ho Chi Minh Le Thi Thanh Xuyen 2002 17.20
Ho Chi Minh Le Thi Thanh Xuyen 2006 38.88
Thai Nguyen Vu Quang Dzung 2002 8.9
Thai Nguyen (data input) Vu Quang Dzung 2006 16.8
4.3. Some effective interventions for preventing school myopia
The results in the intervention and control group before the intervention showed
that the selection of two groups was appropriate. School myopia rate in 2 groups
did not differ with p> 0.05. After two years of intervention, the rate of myopia in
the 2 intervention groups were reduced, in which combination of community and
clinical intervention was reduced higher than community intervention only (4,6%
compared with 4.0%). In contrast, the ratio of myopia in the control group tended

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.