1

Starting in the name of Almighty Allah most merciful, most beneficent

& most kind of all

2

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

3

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)

4

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

8

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

9

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

10

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

12

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.

13

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.

15

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]

17

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.

19

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

21

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.

22

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

24

Bar chart showing frequency of myopes and emmetropes:

40

42

44

46

48

50

52

54

56

myopes emmetropes

Series 1

Series 1

25

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

26

Graphical gender wise distribution of myopes and emmetropes

0

5

10

15

20

25

30

myopia emmetropia

males

females

27

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

29

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.

30

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.

31

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.

34

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: .. . ....

35

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