Estimation of Ocular Axial Length Using Magnetic Resonance Imaging Technique among Adults in Jos Metropolis, North-Central Nigeria.
ABSTRACT
The purposes of this study are to generate an indigenous normogram for ocular axial lengths in a Nigerian population, determine whether there are differences in axial lengths between the right and left eye and among different adult age groups.
The study will also determine whether there are differences in axial lengths between males and females and possible racial differences between Nigerians and Caucasians.
This prospective, cross sectional study involving one hundred (100) Nigerian adults was carried out at Radiology Department, Jos University Teaching Hospital (JUTH), Jos, Plateau State. Convenience sampling method was used to select the subjects.
Pilot study was done to determine the intra-and inter rater reliability of MRI measurement of axial length. The equipment used is a Magnetom Concerto (Siemens) 0.2Tesla MRI machine manufactured in Germany in 2007.Head coils were used as standard practice for brain and ophthalmic scans.
Subjects were placed in the supine position with the scan plane parallel to the coronal plane.T2-weighted axial scans were obtained. Axial lengths of both eyes as well as the age, sex and weight of the subjects were recorded.
Axial length normogram was obtained as 2.46 ± 0.13cm. Measurements of axial length were reliable within and between radiographers ( p > 0.05).
There was no positive correlation with axial length of different age groups. There were no statistical significant difference with axial lengths of males and females( p=0.63) and Nigerians and Caucasians (p<0.05) .
Axial length normograms for a Nigerian population will be added advantage for radiologists and radiographers in Nigeria in their practice. Measurement of axial lengths outside the normal range will likely suggest any of the eye defects.
TABLE OF CONTENTS
Title page i
Approval page ii
Dedication iii
Acknowledgement iv
Table of contents v
List of Tables vii
List of Figures viii
Abstract ix
CHAPTER ONE: INTRODUCTION
1.1 Background of the Study 1
1.2 Statement of the Problem 3
1.3 Purpose of Study 4
1.4 Significance of Study 4
1.5 Scope of the Study 5
1.6 Definition of Terms 5
CHAPTER TWO
Literature Review 7
CHAPTER THREE: Research Methodology
3.1 Research Design 14
3.2 Duration 14
3.3 Study Population 14
3.4 Sampling Techniques 14
3.5 Sample Size 14
3.6 Subject selection criteria 15
3.7 Ethical Clearance 15
3.8 Equipment 16
3.9 Scanning Technique 16
3.10 Statistical method for Data Analysis 18
CHAPTER FOUR: Results
4.1 Data Presentation and Analysis 20
CHAPTER FIVE Discussion and Conclusion
5.1. Discussion 26
5.2. Conclusion 28
5.3. Recommendations 29
5.4. Limitations of the Study 29
5.5. Areas for further research 29
5.6. References 30
Appendices 33
INTRODUCTION
1.1 Background of the Study
The human eye is the sense organ with which we view the world. We use our eyes in almost every activity we perform whether reading, working, watching television, writing a letter, driving a car and in countless other ways (Lauterbur, 2003).
Most people probably would agree that sight is the sense they value more than all the rest. The eye allows us to see and interpret the shapes, colours and dimensions of objects in the world by processing the light they reflect or emit.
The eye is able to detect bright or dim light but it cannot sense objects when light is absent. The amount of light entering the eye is controlled by the pupil, which dilates and contracts accordingly.
The cornea and lens, whose shape is adjusted by the ciliary body, focus the light on the retina, where receptors convert it into nerve signals that pass to the brain.
A mesh of blood vessels, the choroid, supplies the retina with oxygen and sugar. Lacrimal glands (left) secrete tears that wash foreign bodies out of the eye and keep the cornea from drying out.
Blinking compresses and releases the lacrimal sac, creating a suction that pulls excess moisture from the eye’s surface.
REFERENCES
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Deller T., Smith A.D (2003). Axial length assessment using MRI techniques.23-26. Dichiro G. (1996). Angiographic assessment of axial length of eye. American Journal of Ophthalmology; 54:232
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