This study was carried out to compare the amplitude of accommodation and binocular cross cylinder methods in determination of reading Add. A total of sixty two (62) presbyopic subjects where used and thirty were males and thirty were females. Amplitude of accommodation and binocular cross cylinder test were performed and the reading add were determined using amplitude of accommodation and binocular cross cylinder methods. The mean add determined through the amplitude of accommodation were 1.39 ± 0.57 and the mean add determined through the binocular cross cylinder were 1.89 ± 0.59. statistically software using pared sample T-test at 0.05 level of confidence and 95% confidence interval showed that there was a significantdifference (P<0.05) in obtaining the reading add using the amplitude of accommodation and binocular cross cylinder method. Reading add determined through binocular cross cylinder method provides a tentative reading add closer to the final reading add than the reading add determined through the amplitude of accommodation method. Binocular cross cylinder method should be used when determining reading Addition for presbyopes since it gives a tentative reading Addition closer to the final reading Addition for presbyopic subjects.
TABLE OF CONTENTS
Cover Page i
Title Page ii
Table of contents vi
List of Tables x
CHAPTER ONE: INTRODUCTION
- Background of Study 2
- Statement of Problem 14
1.3 Objective of Study 15
1.4 Research Questions 15
1.5 Research Hypothesis 16
1.6 Significance of Study 16
1.7 Scope of Study 16
1.8 Limitation of Study 17
Literature Review 18
CHAPTER THREE: MATERIALS AND METHOD
3.1 Area of Study 23
3.2 Research Design 23
3.3 Population of Study 24
3.3.1 Inclusion Criteria 24
3.3.2 Exclusion Criteria 24
3.4 Sample Size Determination 24
3.5 Sampling Technique 26
3.6 Instruments for Data Collection 26
3.6.1 Validation of Instrument 26
3.7 Procedure for Data Collection 27
3.8 Procedures for Data Analysis 27
3.9 Ethical Consent 28
CHAPTER FOUR: RESULTS
4.1 Presentation of Data 29
4.2 Testing of Hypothesis 41
CHAPTER FIVE: DISCUSSION
5.1 Contribution of knowledge 44
CHAPTER SIX: CONCLUSION AND RECOMMENDATION
6.1 Conclusion 45
6.2 Recommendation 45
LIST OF TABLES
Table 4.1: Age Distribution of subjects 29
Table 4.2: Age and gender distribution of subjects. 30
Table 4.3: Statistical data on Age of subjects 31
Table 4.4: Statistical data on AA and BCC of subjects 32
Table 4.5: Statistical data on Add with AA and BCC of subjects 33
Table 4.6: Distribution of reading add using amplitude of accommodation 34
Table 4.7: Gender distribution of amplitude of accommodation values 35
Table 4.8: Gender distribution of binocular cross cylinder values 36
Table 4.9: Distribution of reading add using amplitude of accommodation 37
Table 4.10: Gender distribution of reading add using binocular cross cylinder 38
Table 4.11: Statistical data on AA and BCC of subjects 39
Table 4.12: Statistical data on Add with AA and BCC of subjects 40
Aging is a normal physiological process, which is associated with changes in the functional capacity of the body. All vital organs of the body begin to lose function as one gets older. And therefore, the effect of aging on vision (the eye) cannot be over emphasized. The most distressing challenge an emmetropic aging adult (mostly from 42 years) has is difficulty in continuing to read tiny prints at hitherto, normal range of near distances (25cm – 60cm). This condition is known as presbyopia.
Caring for patients with presbyopia requires appropriate eye examination and management procedures to reduce the potential visual disabilities associated with presbyopia.Optometrists play an important role in evaluating patients with symptoms or functional disability resulting from presbyopia, an expected vision change that,in some way, affects everyone at some point in adult life.
Vision is the ability to see and the eye is the sense organ responsible for vision. Clinically, it is classified as far and near vision. It is termed far when an object of regard is at 6m and beyond, near when an object is at 40cm. near vision task may include reading, writing, needle work, computing etc. which are all performed at 40cm distance. To achieve clear retina image at 40cm, the mechanism of accommodation must come into play and this is necessary to enable an individual do near work comfortably (Nwala et al., 2015).
Accommodation has been define as the process whereby changes in the dioptric power of the crystalline lens occurs so that an in-focus retinal image of an object of regard at near (40cm) is obtained and maintained at the eyes high resolution area (Nwala et al., 2015). Accommodation is achieved by fine adjustment brought about by a change in the shape of crystalline lens. The cilliary muscle is the active element which facilitates the anatomical changes that occur during accommodation. During accommodation, the cilliary muscle contracts pulling the cilliary ring forward and inward, relaxing the tension on the zonule of zinn while the shape of the crystalline lens (especially of its anterior surface) changes, rounding up and becoming more convex. As a result, the power of the crystalline lens increases bringing about a clearer near vision (Millodot, 2004).
Presbyopia is an age-related progressive loss of crystalline lens power of accommodation resulting in the inability to focus at near distance (Emerole et al., 2014). The ability of the eye to focus clearly for objects at various distances is called accommodation (Grosvenor, 2007). Presbyopia is an aging alteration causing a gradual reduction in near vision which is initially noticed at the age of 45-45 years.
1.1 BACKGROUND OF STUDY
Presbyopia is an age-related progressive crystalline lens power of accommodation resulting in the inability to focus at near distances (Emerole et al; 2014). It is a slow, normal naturally occurring age-related irreversible reduction in maximal accommodative amplitude (recession of near point) sufficient to cause symptoms of blurred vision and eye discomfort or asthenopia at customary near working distance (Nwala et al., 2005), clinically, presbyopia can be defined as a condition whereby the amplitude of accommodation diminishes with increasing age to a point where comfortable or clear vision at near is no longer achieved by mechanism of accommodation (Nwala et al., 2015). The term presbyopia mean “old eye” and is a vision condition involving loss of the eyes ability to focus on close objects. It is a condition that occurs as a part of normal aging and is not considered to be an eye disease. Presbyopia is characterized by long sightedness caused as a result of aging. Presbyopia involves the normal decreasing elasticity of the crystalline lens causing loss of accommodation, and far sightedness. There is a reduced ability to form a clear image of a near object due to this loss of elasticity of the crystalline lens thus, bringing about asthenopic systems such as headache and fatique (Donnell, 2007). The human lens (crystalline lens) makes the fine adjustment which brings the image into sharp focus on the retina. This is done by a change in the thickness of the lens when focusing on a distance objects, the lens become thinner and when focusing on near object, the lens bulges or become falter (More convex). This changes in the shape of the lens are brought about by the cilliary muscles (Benjamin, 2006). Presbyopia a condition of physiological insufficiency of accommodation leading to a progressive fall in near vision, it is not a refractive error (Ametropia), but is now increasingly recognized as an aspect of refractive error that needs to be addressed, it is also called eye sight of old age. The cause is as a result of decrease in the accommodative power of the crystalline lens with increasing age, which occurs due to:
- Age-related changes in the lens which includes decrease in the elasticity of the lens capsule, and progressive increase in size and hardening (Sclerosis) of the lens substance.
- Age-related decline in cilliary muscle, power may also contribute to presbyopia.
(Khurana, 2012). Good near vision is important even among population who use it for task other than reading and working. The age of onset of presbyopia is usually between 38 and 45 years and prevalence is 100% by age 55 (Benjamin, 2006). For most people, doing close work becomes difficult when the amplitude of accommodation is less than 5.000 (corresponding to a near point of accommodation while wearing lenses to correct any distance refractive error) (Grosvenor, 2007). The use of convey lenses (plus lens) to compensate for the reduction in the range of accommodation associated with presbyopia, brings the near point of accommodation to a comfortable distance for a near visual task.
The prevalence of presbyopia in 68 years has been estimated to be 58.15% (Hashemi et al; 2012). Presbyopia affect the patients and also created economic burden if it is left untreated. Factors which can lead to presbyopia include a gradual reduction of zonular tension to increase lens power (Glasser et al., 1998) gradually altered anterior segment geometry and increased lens thickness. Changes in crystalline materials due to the ageing process and the accommodation mechanics by which the alteration in the ciliary muscle position leads to the flattening of crystalline lens decreasing its power (Mancil, 2011). The initial progression depend on several factors and environmental elements such as illumination and temperature (Macmillan et al; 2011).