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ORIGINAL ARTICLE
Year : 2021  |  Volume : 28  |  Issue : 2  |  Page : 87-92  

Burden and presentation of age-related macular degeneration among Nigerians


1 Department of Ophthalmology, Eye Foundation Hospital, Lagos, Nigeria
2 Department of Ophthalmology, University of Calabar Teaching Hospital, Calabar, Nigeria
3 Department of Ophthalmology, Jos University Teaching Hospital, Jos, Nigeria
4 Department of Ophthalmology, Irrua Specialist Hospital, Edo, Nigeria

Date of Submission28-Nov-2020
Date of Acceptance23-Jun-2021
Date of Web Publication25-Sep-2021

Correspondence Address:
Dr. Ogugua N Okonkwo
Eye Foundation Hospital, 27 Isaac John Street, GRA, Lagos
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/meajo.meajo_511_20

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   Abstract 


PURPOSE: Age-related macular degeneration (AMD) is a leading cause of visual impairment worldwide, and its prevalence may also be on the increase in Nigeria. The purpose of this study is to ascertain the burden and pattern of presentation of AMD in a developing country.
METHODS: We conducted a multicenter, prospective study from January to December 2018. Biodata and history of systemic disease were obtained from consecutive patients presenting at four collaborating retina clinics and diagnosed with a retina disease after dilated fundus examination and ocular investigations such as fundus photography, fluorescein angiography, and optical coherence tomography. All eyes diagnosed to have wet and dry AMD were used for the study analysis.
RESULTS: Out of 8614 patients, 156 eyes of 78 patients were diagnosed with AMD. The hospital-based prevalence for AMD was 0.91%. The mean age at presentation was 67.9 ± 9.2 years, ranging from 44 to 95 years. A majority (75.6%) of patients were between 60 and 79 years, 53.8% were females. Thirty-two eyes (20.5%) had wet AMD, while 124 eyes (79.5%) had dry AMD. Sixty-one eyes (39.1%) had moderate visual impairment (<6/18-6/60); 58 eyes (37.2%) had normal vision (6/18 and better); while 27 eyes (17.3%) were blind, and ten eyes (6.4%) had severe visual impairment.
CONCLUSION: AMD contributes to the burden of visual impairment and blindness in the elderly Nigerian. In Nigeria, AMD occurs more in females and most common between the ages of 60 and 79. Dry AMD is four times more common than wet AMD. About 24% of eyes have severe visual impairment or blindness, while about a third each have a moderate visual impairment and normal vision. Increasing awareness of AMD among the at-risk population will be beneficial in achieving early diagnosis and treatment.

Keywords: Ageing, age-related macular degeneration, blindness, Nigeria, visual impairment


How to cite this article:
Okonkwo ON, Ibanga A, Adenuga O, Nkanga D, Ovienra W, Agweye CT, Akanbi T, Oyekunle I, Udoh MM. Burden and presentation of age-related macular degeneration among Nigerians. Middle East Afr J Ophthalmol 2021;28:87-92

How to cite this URL:
Okonkwo ON, Ibanga A, Adenuga O, Nkanga D, Ovienra W, Agweye CT, Akanbi T, Oyekunle I, Udoh MM. Burden and presentation of age-related macular degeneration among Nigerians. Middle East Afr J Ophthalmol [serial online] 2021 [cited 2022 Jan 16];28:87-92. Available from: http://www.meajo.org/text.asp?2021/28/2/87/326673




   Introduction Top


Age-related macular degeneration (AMD) is a degenerative disease of the central retina known as the macula, resulting in loss of central vision, which is essential for most daily activities.[1] Its advanced stage causes irreversible destruction of the macula and results in loss of clear and detailed vision required for daily activities such as reading, driving, facial recognition, and color discrimination. It is a significant risk factor for disability in the older population and significantly affects the quality of life of elderly patients.[2]

AMD is the third leading cause of blindness globally and the leading cause of blindness in developed countries among persons 55 years and older. An estimated 5% of global blindness is due to AMD.[3] It is estimated globally that 196 million people have AMD in 2020, with an expected increase to 288 million in 2040.[4]

Two morphological subtypes are known. These are neovascular AMD and geographic atrophy, which are classified as late stages of AMD. Neovascular AMD accounts for two-thirds of late AMD and 90% of blindness from AMD.[5] If left untreated, neovascular AMD will cause severe visual impairment with an average loss of about four lines of visual acuity (VA) within 2 years of onset of the disease, while patients diagnosed with geographic atrophy tend to lose vision more gradually.[6]

The prevalence of AMD increases exponentially every decade after age 50 and is seen within ages 45–85 years. The global prevalence of AMD is reported to be less common in individuals of African ancestry.[7] However, recent studies have shown that it is more prevalent than earlier believed, particularly in India and Nigeria. The Nigerian blindness survey revealed that AMD was responsible for 3.9% of severe visual impairment and 1.8% of blindness.[8] The disease is becoming a significant cause of blindness and low vision in Nigeria and is reported in studies as a significant concern among the older population.[9],[10],[11],[12],[13]

There is no accurate database on the prevalence of AMD in Nigeria, as in several developing countries. It is, however, rational to expect that as life expectancy and longevity increase due to improved health care, the prevalence of AMD will experience a rise. Few reports on AMD from Nigeria have been based on local individual experience. Therefore, we designed this multicenter research to provide information on AMD and its impact on vision in Nigerians.


   Methods Top


This study was a hospital-based, multicenter, cross-sectional study carried out from January to December 2018 in four collaborating general ophthalmology and retina clinics in Nigeria to determine the prevalence, pattern, and systemic associations AMD in a population within sub-Sahara Africa. The clinics were situated in three public hospitals and one private eye hospital. These four clinics were located in different regions of Nigeria. There was one clinic each, in the north-central and south-west regions and two in the south-south region. We designated a retina specialist in each clinic as the coprincipal investigator, who ensured the accuracy and timely reporting of data collected.

Informed consent was obtained from each patient during the clinic visit before inclusion in the study. The patient's biodata was then obtained, and the investigator documented a history of any systemic disorder. Each patient underwent a comprehensive eye examination including Snellen visual acuity (VA) testing, anterior segment examination using a slit lamp, intraocular pressure measurement, dilated fundus biomicroscopy using a +90 D or +78 D lens, and binocular indirect ophthalmoscopy. We categorized the VA of study participants using the International Classification of Diseases 10 categorization of visual impairment, which is as follows; normal vision: ≥6/18, moderate visual impairment: <6/18–6/60, severe visual impairment: <6/60–3/60, blindness: <3/60 to no perception of light.

A diagnosis of AMD was made from clinical examination. However, additional ocular investigations, including optical coherence tomography, fundus photography, and fundus fluorescein angiography, were performed in clinics where these were available. Clinically, we characterized AMD into dry and wet forms. Dry AMD was diagnosed in the presence of any of the following: multiple small lipid deposits called drusen (<63 μm), medium drusen (63–125 μm), large drusen (>125 μm), retinal pigment abnormalities, and geographic atrophy of the retinal pigment epithelial (RPE) that does not involve the center of the fovea. Wet AMD was diagnosed when there were features of intra- or subretinal leakage, hemorrhage, RPE detachments, choroidal neovascularization in the presence or absence of subretinal lipid deposits [Figure 1].[14] Late AMD is vision-threatening and categorized as either pure geographic atrophy involving the foveal center (e.g., dry) or neovascular (e.g., wet).[15] We obtained ethical approval from the Health Research Ethical Committee of Jos University Teaching Hospital and adhered to the tenets of the Helsinki Declaration. Data from each of the four collaborating clinics were entered into an excel spreadsheet and transmitted at the end of each month to a central data collection point, where collation and analysis were done with IBM SPSS statistics version 22 (IBM Corp. Armonk, NY, USA). Frequencies, means, and standard deviations (SD) were determined, and tests of significance were computed using Pearson's Chi-square test. A P < 0.05 was considered statistically significant.
Figure 1: Fundus appearance of the right eye shows intraretinal hemorrhage and exudates in the macular. There is a pigment epithelial detachment superior to the area of hard exudates. There is widespread deposition of drusenoid material around the macular, and three well-circumscribed round focal hyperpigmented lesions can also be identified. There is also demonstrable widespread retinal pigmentary disturbance

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   Results Top


Eight hundred and seventy-six out of a total of 8614 patients seen within the study period had a retinal diagnosis, while 43 different retinal diseases were diagnosed. A total of 78 patients, 156 eyes, were diagnosed to have AMD. In all, 32 eyes (20.5%) had wet AMD, while 124 eyes (79.5%) had dry AMD (approximate ratio wet: dry of 1:4). Seventy-four patients had bilateral disease at presentation; 14 patients were diagnosed with wet AMD, while 60 patients had dry AMD. Four patients who had bilateral presentation had one eye diagnosed with dry and the fellow eye with wet AMD.

The mean age of patients with AMD was 67.9 ± 9.2 years, ranging from 44 to 95 years. The majority (75.6%) of patients were between 60 and 79 years. We compared the age of patients with AMD with the age of patients diagnosed with other retinal diseases within the same study period, and there was a statistically significant difference (P < 0.001) [Figure 2] and [Table 1]. There were more females (53.8%) than males (46.2%) [Figure 3]. Gender had no significant effect on the diagnosis of AMD (P = 0.190) [Table 1]. The mean duration of symptoms was 18.6 months (SD: 19.1 months) with a median of 12 months.
Table 1: Comparison of age, gender, and associated systemic comorbidities in age-related macular degeneration patients versus other retinal diseases

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Figure 2: Age distribution of patients, n = 78

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Figure 3: Gender distribution of patients with age-related macular degeneration, n = 78

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Concerning the impact of AMD on binocular vision, a minority of patients presented blind (<3/60 in the better eye) and with severe visual impairment (<6/60–3/60 in the better eye), 6.4% and 2.6%, respectively. A majority of patients (34.6%) had moderate visual impairment (<6/18–6/60 in the better eye), while 56.5% had normal vision (6/18 and better in the better eye), as shown in [Table 2].
Table 2: Visual acuity in better-seeing eye (n=78) and monocular visual acuity of all age-related macular degeneration eyes (n=156)

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Concerning monocular vision, there were 61 eyes (39.1%) that presented with moderate visual impairment, 58 eyes (37.2%) with normal to mild visual impairment, while 27 eyes (17.3%) were blind, and ten eyes (6.4%) had severe visual impairment [Table 2].

Hypertension was the most common systemic comorbidity identified among the AMD patients (50%), and by extension, 65.4% had either hypertension or diabetes or both, while 28.2% did not have any associated systemic comorbidity [Table 3]. This finding was statistically significant compared with other retinal diseases (P < 0.0001), as shown in [Table 1].
Table 3: Associated systemic comorbidities (n=78)

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Sub analysis of wet and dry AMD eyes revealed that 56.3% of wet AMD were males, and the age range (60–69 years) had the highest number of patients, 16 (50%). On the other hand, for dry AMD, 56.5% were females, and the age range (70–79 years) contributed the highest number of patients, 52 (41.9%) [Table 4]. There was no statistically significant difference in the age distribution between dry and wet AMD patients (P = 0.215).
Table 4: Age, gender, and associated systemic conditions comparison between dry and wet age-related macular degeneration

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Most of the wet AMD eyes had moderate visual impairment (62.5%), while most of the dry AMD eyes (42.7%) had normal or mild visual impairment. There were more eyes with only mild visual impairment and normal vision among the dry AMD group compared to the wet AMD group, as evidenced by 5 wet AMD eyes (15.6%) versus 53 dry AMD eyes (42.7%) (P = 0.008) [Table 4].

Associated systemic comorbidities were a more common finding in dry AMD eyes; since there was in wet AMD, 13 eyes (40.6%) versus dry AMD 33 eyes (26.6%) that had no associated systemic conditions [Table 4]. Hypertension was the most common associated systemic condition (46 patients: 59%), as shown in [Table 3]. Of those with dry AMD, 63.7% had hypertension, while 34.4% of wet AMD patients were hypertensive (P = 0.020).


   Discussion Top


AMD is the third leading cause of blindness after cataracts and glaucoma globally. It is becoming a primary concern in Nigeria and a significant cause of blindness and visual impairment. AMD accounted for 8.9% of all the retinal diagnoses within a year and ranked third as a cause of retinal disease, as revealed in a previous study involving the same centers.[16] The Nigerian National Blindness survey reported AMD as a significant retinal disease, accounting for 3.9% of severe visual impairment and 1.8% of blindness.[8]

There are modifiable and nonmodifiable risk factors for AMD, including age, genetic factors, tobacco smoking, and obesity. Others include consumption of an unbalanced diet, association with cardiovascular disease, degree of pigmentation (with light-colored eyes being at higher risk), arterial hypertension, and ultraviolet rays. There is increasing evidence to suggest that cataract surgery is a significant predictor, with a four and threefold increase in the risk of neovascular AMD and geographic atrophy, respectively.[14],[17] It is, therefore, pertinent to identify individuals with potential risk factors for early intervention, which may range from health education and counseling to mitigate the effect of the risk factors to delay or slow the progression of AMD. Although this study did not consider risk factor identification, several listed modifiable and nonmodifiable risk factors exist among Nigerians. Efforts at educating the at-risk population on the need for lifestyle change could reduce the rise in the prevalence of AMD.

In their work on AMD in Nigeria, some researchers have noted AMD as a significant retinal disease and cause of vision loss.[10],[18],[19],[20] AMD has been reported as a leading retinal disease in reports from Nigeria.[21],[22] Furthermore, studies emerging from low vision clinics in Nigeria report AMD as one of the common causes of low vision in the country.[23] Life expectancy among Nigerians has been on an upward trend; this may contribute to the increasing importance of AMD as a cause of vision loss. Adopting Western lifestyle regarding nutrition and perhaps smoking may also have a role in the perceived rise in the number of persons living with AMD in the country.

Dry AMD was more prevalent in our study, with up to 124 eyes (79.5%) affected compared to 32 eyes (20.5%) with wet AMD. This high prevalence is similar to studies in developed and developing countries.[24],[25] Wet AMD may have been underdiagnosed and therefore underreported. Some of the study sites in our study did not have the required technology outside of clinical examination for further disease evaluation after diagnosis had been made from findings on clinical examination. Lack of appropriate technology for disease evaluation and monitoring is common in several underserved clinics in developing countries and affects service delivery to patients. This situation of lack can be addressed by providing subsidy and advocacy for the public-private partnership model, which has been shown to work elsewhere.

The mean age of patients in the studied population was 67.9 ± 9.2, and the majority (75.6%) of patients were between 60 and 79 years. Our peak age agrees with reports in literature from both developed and developing countries.[10] Age is a significant factor in AMD, as revealed by this study since comparison with the age of other retinal diseases diagnosed within the same study period was statistically significant.

Although there were more females in this study, it was not statistically significant. Some studies have reported similar gender differences, which may be because females live longer than males, thus having more time to develop the disease. Global data have it that majority of diagnosed incident AMD cases in the seven major markets of the US, France, Germany, Italy, Spain, UK, and Japan occur in women (65.76%) with just over 7.40 million cases, while men accounted for 34.24%, with just under 3.85 million cases in 2016.[24] We found that wet AMD was more common in males while dry AMD tended to affect more females; this finding was not statistically significant.

In terms of monocular vision, a majority (39.1%) of eyes in this study had moderate visual impairment (<6/18–6/60). Eyes with wet AMD had more moderate visual impairment, while eyes with dry AMD had more of normal or mild visual impairment [Table 4]. This finding supports the notion that wet AMD is associated with worse VA, reported previously in studies from Nigeria and the Western world.

Hypertension was the most common systemic comorbidity in our study. Other researchers in Nigeria have reported a similar finding. Dry AMD was more common than wet variant in this cohort of patients. Case–control and population-based studies that have examined the relationship between AMD, hypertension, and other cardiovascular diseases have shown conflicting results. However, these systemic comorbidities have a damaging effect on the eyes apart from acting as AMDs risk factor. A study in Onitsha, Nigeria, reported hypertension as a common systemic comorbidity.[24] According to the Beaver Dam Eye Study, controlling for other factors, persons with controlled hypertension at baseline were about twice as likely, while persons with uncontrolled hypertension were thrice as likely to develop exudative macular degeneration.[26] Other studies have also linked moderate to severe hypertension to exudative AMD.[27]


   Conclusion Top


AMD is a significant cause of vision loss in Nigeria and perhaps other developing countries in sub-Saharan Africa. This research found that AMD is more common in females and affects mainly persons between the ages of 60 and 79 years. Dry AMD is four times more common than wet AMD. About 24% of eyes have severe visual impairment or blindness, while over a third of eyes have a moderate visual impairment and another third normal vision. An association between hypertension and AMD was established, which may be stronger for dry AMD than wet AMD. We suggest that those strategies and interventions for managing AMD adopted by more developed countries (with local modifications to suit the Nigerian situation) will benefit Nigerian AMD patients. Therefore, there is an urgent need to institute awareness campaigns among the at-risk population, including screening programs and health education. Provision of appropriate diagnostic technology and treatment facilities will also be necessary.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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