abbas research.pdf
TRANSCRIPT
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Starting in the name of Almighty Allah most merciful, most beneficent
& most kind of all
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Comparison of accommodation between myopes and emmetropes
Among age group of 25 to 35 years
A THESIS SUBMITTED TO UNIVERSITY OF HEALTH SCIENCES IN FULLFILMENT
REQUIREMENT FOR THE DEGREE OF
B.Sc. (Hons) in Optometry & Orthoptics
Submitted by Miss Zubia Sattar
(2010-RMC-0418-UHS)
Supervisor Dr. Ali Raza
M.B.B.S, M.C.P.S, F.C.P.S
Course Coordinator Dr. Rasheed Shiekh
M.B.B.S
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It is certified that Miss Zubia Sattar has completed her study on Comparison of
accommodation between myopes and emmetropes among age group of 25 to 35 years for
the partial fulfillment of the degree requirement of B.Sc. (Honors) Optometry & Orthoptics from
Rawalpindi Medical College & Allied hospitals Rawalpindi.
Dated: _____________ _____________________
Signature of course supervisor
Dr. Ali Raza
M.B.B.S, M.C.P.S, F.C.P.S (Oph)
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ACKNOWLEDGMENT
Starting under the shadow of ALLAHS blessing-The most merciful the most Gracious. I am
thankful to Almighty Allah for wisdom, courage and perseverance that HE has bestowed upon
me during accomplishment of this research.
I would like to express my gratitude to my honorable coordinator Dr Rasheed whose stimulating
suggestions and encouragement helped me to complete my research. A special thanks goes to
Miss Saima who supervise me in whole duration with their full dedication and devotion. I would
pay thanks to Miss Kashmala who helped me to correct my mistakes in practical work. I would
also pay thanks to my husband Abbas Aslam for helping me a lot in making my results.
Last but not the least I express my deep feelings to my respected parents and loving friends
Attiya, Munam, Sadia, Rabia and Tayyaba for their support and encouragement.
Zubia Sattar
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Declaration
I hereby declare that all the data during this study was collected by me
and the data collection was used only for academic purpose.
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Dedication
Dedicated to my beloved parents
Zubia Sattar
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Abstract
Purpose: The purpose of my study was to compare the accommodation between myopes and
emmetropes among age group of 25 to 35 years.
Material and Method: 99 subjects between ages of 25 to 35 years in eye OPD of Benazir
Bhutto hospital were included in which there were 54 myopes and 45 emmetropes. Near point of
convergence and amplitude of accommodation were measured with RAF rule. Different
variables were also considered e.g. gender, visual acuity, cover test, and heishberg reflex test.
Objective refraction (AR) and subjective refraction were performed for myopic patients and pen
push up exercises were advice to convergence insufficiency patients.
Results: Comparison showed that average amplitude of accommodation is higher in myopes
than emmetropes.
Conclusion: Study showed that amplitude of accommodation from 1-10D is more in myopes
than emmetropes while amplitude of accommodation from 11-20D is more in emmetropes than
in myopes. Accommodation amplitude 20-25D and 30-35D is also higher in myopes. Hence,
myopic patients had more accommodation than emmetropes
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TABLE OF CONTENTS
UNIT-1 INTRODUCTION
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
Human eye
Anatomy of human eye
Accommodation
Mechanism of accommodation
Emmetropes
Myopia
Relationship of accomodaton with emmetropia and myopia
Literature review
Rational of study
Aim and Objective
UNIT-2 MATERIALS & METHODS
2.1
2.2
2.3
2.4
Subject
Study Design
Setting
Duration of Study
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2.5
2.6
2.7
2.8
2.9
2.10
Sample Size
Sampling Technique
Inclusion Criteria
Exclusion Criteria
Methodology
Statistical Analysis
UNIT-3 DISCUSSION
3.1
3.2
3.3
3.4
Results
Discussion
Conclusion
Limitation
UNIT-4 APPENDIX
4.1 References
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ABBREVIATION
Serial
no.
Terminology
Abbreviation
1.
OPD
Outdoor patient department
2.
SC
Sine correction(without glasses)
3.
CC
Cum correction(with glasses)
4.
PH
Pin hole
5.
NPC
Near Point of Convergence
6.
NPA
Near Point of Accommodation
7.
AA
Amplitude of Accommodation
8.
CT
Cover test
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Chapter 01
1-INTRODUCTION
1.1Human Eye
The human eye is one of the most remarkable sensory systems. Leonardo da Vinci was acutely
aware of its prime significance: the eye, which is termed the window of the soul, is the chief
organ whereby the senso commune can have the most complete and magnificent view of the
infinite works of nature [1]. Human beings gather most of the information about the external
environment through their eyes and thus rely on sight more than on any other sense, with the eye
being the most sensitive organ we have. Besides its consideration as a window to the soul, the
eye can indeed serve as a window to the identity of an individual. It offers unique features for the
application of identification technology.
1.2 Anatomy of Human Eye
The adult eyeball, often referred to as a spherical globe, is only approximately spherical in shape,
with its largest diameter being 24 mm antero-posteriorly [2-3]. The anterior portion of the eye
consists of the cornea, iris, pupil, and crystalline lens. The pupil serves as an aperture which is
adjusted by the surrounding iris, acting as a diaphragm that regulates the amount of light entering
the eye. Both the iris and the pupil are covered by the convex transparent cornea, the major
refractive component of the eye due to the huge difference in refractive index across the air-
cornea interface [4]. Together with the crystalline lens, the cornea is responsible for the
formation of the optical image on the retina. The crystalline lens is held in place by suspensory
ligaments, or zonules, that are attached to the ciliary muscle. Ciliary muscle actions cause the
zonular fibers to relax or tighten and thus provide accommodation, the active function of the
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crystalline lens. This ability to change its curvature, allowing objects at various distances to be
brought into sharp focus on the retinal surface, decreases with age, with the eye becoming
presbyopic. Besides the cornea and crystalline lens, both the vitreous and aqueous humor
contribute to the dioptric apparatus of the eye, leading to an overall refractive power of about 60
diopters [5]. The aqueous humor fills the anterior chamber between the cornea and iris, and also
fills the posterior chamber that is situated between the iris and the zonular fibers and crystalline
lens. Together with the vitreous humor, or vitreous, a loose gel filling the cavity between the
crystalline lens and retina, the aqueous humor is responsible for maintaining the intraocular
pressure and thereby helps the eyeball maintain its shape. Moreover, this clear watery fluid
nourishes the cornea and crystalline lens. Taken all together, with its refracting constituents, self-
adjusting aperture, and finally, its detecting segment, the eye is very similar to a photographic
camera. The film of this optical system is the retina, the multilayered sensory tissue of the
posterior eyeball onto which the light entering the eye is focused, forming a reversed and
inverted image. External to the retina is the choroid, the layer that lies between retina and sclera.
The choroid is primarily composed of a dense capillary plexus, as well as small arteries and
veins [5]. As it consists of numerous blood vessels and thus contains many blood cells, the
choroid supplies most of the back of the eye with necessary oxygen and nutrients. The sclera is
the external fibrous covering of the eye. The visible portion of the sclera is commonly known as
the white of the eye.
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1.3 Accommodation
Accommodation is increase in dioptric power of the eye when eye changes fixation from
distance to near.
As we know that in an emmetropic eye, parallel rays of light coming from infinity are brought to
focus on the retina with accommodation at rest .Our eyes have been provided with the unique
mechanism by which we can even focus the diverging rays coming from a near object on the
retina in a bid to see clearly .This mechanism is called accommodation .In it, there occurs
increase in the power of the crystalline lens. [6]
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1.4 Mechanism of Accommodation
Several theories have been proposed to explain the mechanism of accommodation of the human
lens.
The more widely accepted Helmholtz theory of accommodation assumes that the zonules
supporting the crystalline lens are under maximal tension when the lens is at minimum optical
power.[7] The Helmholtz theory proposes that tension is exerted by the anterior and posterior
zonules together or by all three sets of zonules simultaneously. This theory states that the optical
power of the crystalline lens is increased by relaxation of the tension on these zonules, while an
increase in zonular tension causes a decrease optical power.
The Schachar theory of accommodation assumes that the equatorial zonules are under
minimum tension when the lens is at minimum optical power [8-12] it states that the equatorial
zonules apply increasing tension to the human crystalline lens during accommodation. This
increased equatorial zonular tension increases the equatorial diameter of the lens, alters the
surface curvatures of the human crystalline lens and, thereby, increases the central optical power
of the lens. The Schachar theory proposes that during the accommodative process increasing
tension is exerted exclusively by the equatorial zonules. In Schachars theory, the equatorial
zonules act similar to skeletal muscle tendons and are the components that transduce the force of
the ciliary muscle to change the shape and, thereby, the focal power of the crystalline lens. The
anterior and posterior zonules act like the supportive ligaments of skeletal joints and are
stabilizing components, which are tense during distance vision and relax during accommodation.
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Hence, following are the changes occur during accommodation:
Lens become more globular in shape
Dioptric power of eye increases
Pupil constricts
Eyes converges
Cilliary muscles contracts
Zonules relaxes
1.5 Emmetropia
Emmetropia (optically normal eye) can be defined as a state of refraction wherein the parallel
rays of light coming from infinity are focused at the sensitive layer of retina with the
accommodation being at rest.
Emmetropia describes the state of vision where an object at infinity is in sharp focus with the eye
lens in a neutral or relaxed state. This condition of the normal eye is achieved when the refractive
power of the cornea and the axial length of the eye balance out, which focuses rays exactly on
the retina, resulting in perfect vision. An eye in a state of emmetropia requires no correction [13].
1.6 Myopia
Myopia or shortsightedness is a type of refractive error in which parallel rays of light coming
from infinity focused in front of the retina when accommodation is at rest. . It is evident that
during excessive near work, accommodation and convergence are continuously used. According
to an international study, longer time spent on reading for pleasure and reports of close reading
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distance (< 30 cm) were associated with a more myopic refraction[14]. The worldwide urban and
rural patterns derived from both incidence and prevalence data are consistent with the near work
hypothesis that increased reading and computer use may be a risk factor for myopia[15-16].
The following diagram shows refraction of light in myopic eye.
1.7 Relationship of accommodation with emmetropia and myopia
Myopes are suspected to be poorer at responding to accommodative stimuli than emmetropes,
and this may worsen the degree of their myopia. [17]
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There is a strong association between myopia and near work, and it has been reported that the
rapid rise in the prevalence of myopia in Singaporean children may be related to an increase in
near work demands such as reading. [18-22]Although the mechanism by which near work affects
myopia progression is not known, prolonged chronic accommodation during close work has been
implicated in myopia. Supporting evidence for this theory provided by several researchers have
demonstrated that myopic subjects tend to accommodate less to near targets, or that they
exhibited a greater lag of accommodation than no myopic subjects. [23-25]
1.8 Literature review
Case 01:
1.1 A study conducted in Sydney shows myopic eyes have reduced accommodative
facility at distance, and accommodative responsiveness to both positive and negative
defocus is slow. However, accommodative facility as a test does not have sufficient
power to discriminate eyes with myopia from other refractive errors.
Case 02:
2.1 A study in England shows all accommodative behaviors have large inter-subject
variability at all of the reading demands. Accommodative lags significantly increased
with closer demands (Mean lag (D): 0.689D at 1.5D, 0.877D at 2.5D, 0.987D at 3.5D
(ANOVA:p
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Case 03
3.1 A study conducted in United States shows eyes with lower amplitudes of
accommodation must use more of their accommodative reserve for near work. Myopia
may be an adaptation that develops in eyes with reduced accommodative amplitudes.
1.9 Rational of the study
In Pakistan to the best of my knowledge there are no published studies on relationship of
accommodation between emmetropia and myopia.
The present study aims to compare accommodation between emmetopes and myopes among age
group 25-35 years.
1.10 Aim and objective of the study
To find out comparison of accommodation between myopes and emmetropes (25-35years)
attending ophthalmology out-patient department at Benazir Bhutto Hospital Rawalpindi during the
time period of three months.
Objectives:
To find out amplitude of accommodation in myopes and emmetropes.
To compare the amplitude of accommodation between myopes and emmetropes.
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Chapter no.2
2.1 Subject:
Comparison of accommodation in myopes and emmetropes
2.2 Study design:
It was cross sectional descriptive study.
2.3 Setting:
Benazir Bhutto Hospital.
2.4 Duration of study:
Two months after the approval of synopsis.
2.5 Sample size:
99 subjects were selected depending upon the time available.
2.6 Sampling technique:
Consecutive sampling
2.7 Inclusion criteria:
Patients having age group of 25-35years.
Patients of both sexes.
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Patients having complained of headache.
Patients with complain of blurred or decreased vision.
Co-operative patients.
2.8 Exclusion criteria:
Traumatic eyes.
Patients with ocular pathology.
Patients with any systemic disease affecting eyes.
Spherical corrections of more than 6.00 DS of myopia.
Cylindrical correction of more than 0.75 DC
Non Cooperative patients
2.9 Study methodology:
The study started on 1st November 2014 and continued till 1st January 2015. 99 subjects between
ages of 25 to 35 years in eye OPD of Benazir Bhutto hospital were included in which there were
54 myopes and 45 emmetropes .Visual acuity of all were taken by Snellens acuity chart at 6m.
Objective refraction (AR) and subjective refraction were performed and pen push up exercises
were advice to convergence insufficiency patients. Near point of convergence and amplitude of
accommodation were measured with RAF rule after performing subjective refraction. Data was
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collected on specially designed Performa under supervision of senior refractionists. Subjects
having any ocular pathology other than refractive error were excluded from my study.
2.10 Data analysis:
All the data was analyzed using MS Excel 2010. Categorical data was represented by frequency,
percentage and cross tabulation.
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Chapter no. 3
Results:
Total sample population was 99 out of which 50 were males and 49 were females.
gender of subjects
Frequency Percent Valid Percent
Cumulative
Percent
Female 49 49.0 49.0 49.0
Male 50 50.0 50.0 99.0
Total 99 100.0 100.0
Bar graph showing gender wise distribution of patients
48.4
48.6
48.8
49
49.2
49.4
49.6
49.8
50
50.2
males females
Series 1
Series 1
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Total Frequency of myopes and emmetropes:
The results showed that myopia was present in 54 subjects (54.54%), and rest of 45(45.45%)
were emmetropes out of 99.
Frequency Percentage Cummulative
frequency
Myopes
Emmetropes
Total
54.00
45.00
99
54.54
45.45
100
54.45
99.99
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Bar chart showing frequency of myopes and emmetropes:
40
42
44
46
48
50
52
54
56
myopes emmetropes
Series 1
Series 1
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Gender wise distribution of myopia and emmetropia:
In sample population of 99 there was 50 males out of which 20 were myopes and 30 were
emmetropes while there were 49 females out of which 24 were myopic and 25 were emmetropes.
Myopia
frequency
Males
females
20.00
24.00
Emmetropia
frquency
Males
Females
30,00
25.00
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Graphical gender wise distribution of myopes and emmetropes
0
5
10
15
20
25
30
myopia emmetropia
males
females
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Accommodation in emmetropes and myopes * myopes
and emmetropes Cross tabulation
Count
myopes and emmetropes
Total myopes emmetropes
Accommodation(in
Diopters) in
emmetropes and
myopes
1-5 10 4 14
6-10 19 11 30
11-15 12 17 29
16-20 7 11 18
21-25 4 0 4
26-30 0 1 1
31-35 2 1 3
Total 54 45 99
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Pie chart showing comparison of accommodation in myopes and emmetropes
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Statistics
Comparison of
Accommodation in
emmetropes and
myopes
Accommodatio
n in myopes
Accommodation
in emmetropes
N Valid 99 54 45
Missing 0 45 54
Mean 1.8283 11.54545 12.84118
Std. Deviation
Z test
1.33279
-6.18
.50046
1.32842
[Zcal] > 1.96 =Results are significant.
3.2Disscusion:
The study was conducted to find out comparison of accommodation between myopes and
emmetropes among age group 25-35y.Study showed that amplitude of accommodation from 1-
10D is more is more in myopes than emmetropes while amplitude of accommodation from 11-
20D is more in emmetropes than in myopes. Accommodation amplitude 20-25D and 30-35D is
also higher in myopes. Z test showed that results are significant.
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3.3Conclusion:
Results showed that overall average amplitude of accommodation is higher in myopes than in
emmetropes. Myopic patients had more accommodation than emmetropes.
3.4Limitations:
Limitation of the study is small sample size.
Limited resources.
Short duration of study.
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Chapter 04
4.1References:
1. Pevsner, J.: Leonardo da Vincis contributions to neuroscience. Trends Neurosci. 25, 217220
(2002)
2. Davson, H.: The Eye, vol. 1a, 3rd edn. pp. 164. Academic Press, Orlando (1984)
3. Born, A.J., Tripathi, R.C., Tripathi, B.J.: Wolffs Anatomy of the Eye and Orbit, 8th edn. pp.
211232, 308 596. Chapman & Hall Medical, London (1997)
4. Ian Hicksons Description of the Eye. http://academia.hixie.ch/ bath/eye/home.html. Accessed
(1998)
5. Warwick, R., Williams, P.L. (eds.): Grays Anatomy, 35th British edn. pp. 11001122. W.B
Saunders, Philadelphia (1973)
3) Christopher Candland, "Pakistans Recent Experience in Reforming Islamic Education" in
Education Reform in Pakistan: Building for the Future, Washington, D.C. 2005: 151-153
4) Abdullah Nowaira Khadija, Abdullah Tanveer Muhammad. Reaching out a strategy to provide
primary eye care through the indigenous educational system in Pakistan. Community Eye Health
J 2006; 19(59):52-53
5)Ip JM, Saw SM, Rose KA, Morgan IG, Kifley A, Wang JJ, Mitchell P. Role of near work in
myopia: findings in a sample of Australian school children. Invest Ophthalmol Vis Sci. 2008 Jul;
49(7):2903-10.
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6) AK Khurana, (Ed.). (2008) Theory and Practice of Optics and Refraction. Reed Elsevier India
Private Limited.
7) von Helmholtz H. Uber die accommodation des auges. Albrecht von Graefes Arch
Ophthalmol. 1855; 1:1-89.
8) Schachar RA. Cause and treatment of presbyopia with a method for increasing the amplitude
of accommodation. Ann Ophthalmol. 1992; 24:445-452.
9) Schachar RA. Zonular function: A new hypothesis with clinical implications. Ann
Ophthalmol. 1994; 26:36-38.
10) Schachar RA, Anderson DA. The mechanism of ciliary muscle function. Ann Ophthalmol.
1995; 27:126-132.
11) Schachar RA. Histology of the ciliary muscle-zonular connections. Ann Ophthalmol. 1996;
28:70-79.
12) Schachar RA. Is Helmholtzs theory of accommodation correct? Ann Ophthalmol. 1999;
31:10-17.
13) Wikipedia, the free encyclopedia- Emmetropia
14) Linn LK, Shih YF, Tsai CB, et al. Epidemiologic study of ocular refraction among school
children in Taiwan in 1995. Optom Vis Sci1999; 76: 275-281
15) Saw SM, Katz J, Schein OD, et al. Epidemiology of myopia. Epidemiol Rev. 1996;
18(2):175-87
16) Ophthalmology. 2008 Apr; 115(4):678-685.e1.
17) McBrien NA, Millodot MOphthalmic Physiol Opt. 1986; 6(2):145-9. [PubMed] [Ref list]
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18) Saw SM, Chan B, Seenyen L, Yap M, Tan D, Chew SJ. Myopia in Singapore kindergarten
children. Optometry 2001; 72:286-91.
19) Saw SM, Wu HM, Seet B, Wong TY, Yap E, Chia KS, et al. Acade achievement, close up
work parameters, and myopia in Singapore military conscripts. Br J Ophthalmol 2001; 85:855
20)Saw SM, Hong RZ, Zhang MZ, Fu ZF, Ye M, Tan D, et al. Near-work activity and myopia in
rural and urban schoolchildren in China. J Pediatric Ophthalmol Strabismus 2001; 38:149-55.
21)Saw SM, Chua WH, Hong CY, Wu HM, Chan WY, Chia KS, et al. Near work in early-onset
myopia. Invest Ophthalmol Vis Sci 2002; 43:332-9.
22) Saw SM, Zhang MZ, Hong RZ, Fu ZF, Pang MH, Tan D. Near-work activity, night-lights,
and myopia in the Singapore-China Study. Arch Ophthalmol 2002; 120:620-7.
23) Abbott ML, Schmid KL, Strang NC. Differences in the accommodation stimulus curves of
adult myopes and emmetropes. Ophthalmic Physio Opt 1998; 18:13-20.
24) Gwiazda J, Thorn F, Bauer J, Held R. Myopic children show insufficient accommodative
response to blur. Invest Ophthalmol Vis Sci 1993; 34:690-4.
25) McBrien NA, Millodot M. The effect of refractive error on the accommodative response
gradient. Ophthalmic Physiol Opt 1986; 6:145-9.
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HISTORY PERFORMA
Patients Name: Age/ Gender: .
HISTORY
Chief complain ..
...
Ocular History ....................................
Family Ocular History .
Medical History ..
Family Medical History .
Contact lens History
EXAMINATION
Slit lamp examination
Lids ..
Pupil .
Cornea .
Conjunctiva
Visual Acuity SCC CC PH
Rt Eye: .. . ....
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Lt Eye : . .
Hirschberg reflex:Cover test ...................................................................
REFRACTION
1. Objective Refraction (Retinoscopy )
Rt.Eye: .. Lt.Eye: ..
2 Subjective Refraction
Rt Eye: Lt Eye:
Final Prescription:
Rt. Eye: Lt. Eye: ...
Type of refractive error: Myopia Hypermetropia Astigmatism
Amblyopia Anisometropia
Visual Acuity with glasses: Rt. Eye Lt. Eye
Diagnosis: ____________________________________________________________________________________________
ADVICES:
1.___________________________________________________________________________________
_______________________________ _______________________________
Sign of student sign of supervisor