Prevalence of Congenital Colour Vision Deficiency In Nigerians Living in UGEP, Cross River State

ABSTRACT

Colour vision and colour blindness are synonymous terms describing poor colour discrimination by the visual senses. Congenital colour vision defects are common, x-linked inherited, non-progressive and untreatable disorders.

Elsewhere, screening for these disorders is an established practice so that those affected can be advised about occupational preclusions.

However, population-based study on the broader impact of colour vision defects is limited. A descriptive cross-sectional survey was conducted using Plates 1-17 of the 2008 edition of the Ishihara’s colour album. The study was undertaken in Ugep, a rural community in Cross River State, Nigeria.

A convenient sample of 1500 male and female subjects ranging from 10-60 years of age was used and the selection was based on sampling.

The reveals that the prevalence of congenital colour vision deficiency in  Nigerians living in Ugep is 1.87%(28 of 1500  subjects) and that of total colour blindness is barely 0.20%.

The gender of colour blindness in the sample 2.8% for males and 0.7% for females indicates a significantly greater frequency of defect among males than females (p<0.001,df=1).

The distribution of colour blindness based on age brackets 10-20,21- 30,31-40,41-50,51-60 years was 16,2,1,9,0 and this reveals no  sequence between age and the defect (p<0.001,df=1).

The  findings which serve as data for the area under investigation are inconsistent with Nigerian samples reported for other regions in the country but the regional variations are not accounted for. Population- based screening for colour vision deficiency helpful for prevocational counselling is recommended.

TABLE OF CONTENTS

Certification i
Dedication ii
Acknowledgement iii
Abstract iv
Table of Content v
List of tables vii
List of figures viii
Glossary ix

CHAPTER ONE

1.0 Introduction
1.1. Background of the Study – – – – – 1
1.2. Statement of Problem – – – – – 2
1.3. Significance of Study – – – – – 3
1.4. Purpose of Study – – – – – 4
1.5. Objectives of Study – – – – – – 4
1.6. Research Hypotheses – – – – – – 4
1.7. Research Questions – – – – – – 4
1.8. Glossary – – – – – – – – 4

CHAPTER TWO

2.0 Review of Related Literature
2.1. Basic Theories of Colour Vision – – – – 5
2.2. Classification of Congenital Colour Vision – – 6
2.3. Prevalence of Congenital Colour Vision Deficiency – 8
2.4. Importance of Investigating Colour Vision Deficiency 10
2.5. Clinical Tests of Colour Vision – – – – 12

CHAPTER THREE

3.0 Methods and Methodology
3.1. The Research Design – – – – – – 15
3.2. The Study Area – – – – – – 15
3.3. The Sample – – – – – – – 15
3.4. Sampling Procedure – – – – – – 16
3.5. Instrument for Data Collection – – – – 16
3.6. Procedure for Data Collection – – – – 16
3.7. Method of Data Analysis – – – – – 17
3.8. Validity of Ishihara Test Plates – – – – 17
3.9. Ethical Consideration – – – – – – 18

CHAPTER FOUR

4.0 Presentation of Results
4.1 Frequency of Colour Vision Deficiency — – 19
4.2 Frequency of Different Types of Colour Vision Defect – 20
4.3 Frequency of Colour Vision Deficiency Based on Gender -22
4.4 Frequency of Colour Vision Deficiency Based on Age -24

CHAPTER FIVE

5.0 Discussion of Findings
5.1 Discussion – – – – – – – 26
5.2 Summary and Conclusion – – – – – – 30
5.3 Recommendation – – – – – – – 30
5.4 Suggestion – – – – – – – – 31
References – – – – – – – – 32
Appendix I – – – – – – – – 38

INTRODUCTION

1.1 Background to the Study

Colour identification is one of our most important visual abilities and nearly everyone including colour vision defective individuals can see colour and make discriminations based on colour.

This  general tendency seems to query the rationale for screening colour vision and minimizes the benefits derived from available reports on colour  blindness.

In the course of studying normal colour vision, investigators have observed a wide range of colour discrimination ability especially under such circumstances as the absence of cues, poor illumination, working at speed and viewing objects that subtend a narrow angle at the eye.

It  is further observed that colour vision defectives show colour vision  deficits when compared with those with normal colour vision (Ishihara, 2008; Williams et al, 1998; and Balasundaram and Reddy, 2006).

However, some claim that colour vision deficiency does not interfere with daily routine or lifestyle since a reduced visual acuity is not associated with it.

Most people with colour vision defects develop effective adaptive strategies and behaviours, and they use other cues such as colour saturation, to deal with any potential limitations in their professional personal life.

This makes it possible for most colour blind individuals not to be aware of their deficiency (Holroyd and Hall, 1997). Others speculate that clinicians are reluctant in colour vision investigations because should a congenital deficiency be identified there is no treatment  for those affected (Adams and Haegerstrom, 1987).

REFERENCES

Adams, A. and Haegerstrom-Portnoy, G. (1987). In Amos, J. (1987) Diagnosis and Management in Vision Care. Boston: Butterworth, 671-771
Adams, A. J. (1974) Colour Vision Testing in Optometric Practice. Journal of the American Optometric Assoc., 45:35-42.
Adam, A. J., Bailey., Harwood, L. W. (1983) Colour Vision  Screening:  A comparison of the AOHRR and Farnsworth F₂ Tests. Am. optom. Physiol. Opt 61:1-9.
Balasundaram, R. and Reddy, S. C. (2006) Prevalence of Colour Vision Deficiency Among Medical Students and Health  Personnel.  Malaysian  Family  Physician, 1(2&3): 52-53
Birch, J., Hrisholm, I., Kinner, P. et al  (1979) Clinical Testing Methods. In  Pokorny,   J., Smith, V., Verriest, G. and Picker, A. (1979) Congenital and  Acquired  Colour Vision Defects. NY: Grune and Stratton.
Bowman, K.J. (1982) A method of Quantitative scoring of the Farnsworth Panel D- Acta Ophthalmol. 60:907-16