A study of occurrence and risk factors of age-related macular degeneration in a region of Central India

Archana Sunil Nikose; Arpita Sthapak; Mayuri Patil

doi:10.4103/jcor.jcor_87_17

ORIGINAL ARTICLE

Year : 2019 | Volume : 7 | Issue : 3 | Page : 97-100

A study of occurrence and risk factors of age-related macular degeneration in a region of Central India

Archana Sunil Nikose¹, Arpita Sthapak², Mayuri Patil¹
¹ Department of Ophthalmology, NKP Salve Institute of Medical Science and Research Center, Nagpur, Maharashtra, India
² Eye Center, Jan Jyoti Eye Hospital, Jabalpur, Madhya Pradesh, India

Date of Submission	09-Aug-2017
Date of Decision	06-Nov-2019
Date of Acceptance	11-Nov-2019
Date of Web Publication	11-Dec-2019

Correspondence Address:
Archana Sunil Nikose
Department of Ophthalmology, NKP Salve Institute of Medical Science and Research Center, Nagpur, Maharashtra
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jcor.jcor_87_17

Abstract

Purpose: The purpose of the study is to determine the occurrence of age-related macular degeneration (AMD) in patients aged >50 years and to study risk factors associated with it. Materials and Methods: It was a cross-sectional prospective study, in which 907 patients aged 50 years and above of both sexes were studied who visited eye outpatient department of our tertiary hospital between October 2014 and September 2016. Visual acuity, slit-lamp examination, and disc and macular evaluation with 90D lens and 20D using indirect ophthalmoscope were performed. AMD was confirmed by doing fundus fluorescein angiography. Association of AMD with hypertension, diabetes, cardiovascular disease, smoking, alcohol consumption, and body mass index were studied. Results: Out of 907 patients, 21 had AMD, i.e., the occurrence was 2.3%. Of 21 patients, 15 had early AMD (1.6%) and 6 had late AMD (0.7%). The highest occurrence of 9.75% was seen in age group of 80 years and above, whereas other risk factors of AMD, i.e., smoking showed P = 0.1261, cardiovascular disease P = 0.0251, and prior cataract surgery with P = 0.0001. Conclusion: Age was found to be strong and consistent risk factor of AMD. Smoking, cardiovascular disease, and prior cataract surgery were significantly associated with AMD.

Keywords: Age-related macular degeneration, drusen, fundus fluorescein angiography, optical coherence tomography

How to cite this article:
Nikose AS, Sthapak A, Patil M. A study of occurrence and risk factors of age-related macular degeneration in a region of Central India. J Clin Ophthalmol Res 2019;7:97-100

How to cite this URL:
Nikose AS, Sthapak A, Patil M. A study of occurrence and risk factors of age-related macular degeneration in a region of Central India. J Clin Ophthalmol Res [serial online] 2019 [cited 2023 Jun 2];7:97-100. Available from: https://www.jcor.in/text.asp?2019/7/3/97/272716

Age-related macular degeneration (AMD) is a disease of the elderly that leads to irreversible loss of vision. It is the third most common cause of blindness worldwide.^[1] AMD results in severe loss of central vision in advanced stages. With increase in life expectancy, the incidence of AMD will also increase.^[2] AMD accounts for 8.7% of global visual disability.^[1],[3] Prevalence of AMD in India ranges from 1.8% to 4.7%.^[1]

According to Age-Related Eye Disease Study classification, early stage includes soft drusen and pigmentary abnormalities of retinal pigment epithelium (RPE), whereas late stage includes geographic atrophy, choroidal neovascularization (CNV), pigment epithelial detachment (PED), and fibrous scarring of macula.

Geographic atrophy is a feature of dry AMD, and the wet AMD consist of choroidal neovascularization, PED, and disciform scar.

According to the international age-related maculopathy epidemiological study group, AMD is classified as early AMD which is characterized by medium or large drusen and RPE hyperpigmentation, whereas advanced AMD is characterized by geographic atrophy and CNV.^[4],[5]

The various known-risk factors are age, smoking, obesity, alcohol consumption, diabetes, hypertension, cardiovascular diseases, previous cataract surgery, and family history. With the introduction of new and effective treatments for AMD, there is a strong need for early identification of persons at high risk of progression to the late stages, as timely treatment at the onset of disease will lead to better visual prognosis. Hence, the purpose of our study was to find the occurrence and associated risk factors of AMD.

Materials and Methods

A total of 907 patients above the age of 50 years fulfilling the inclusion criteria were included in this study. The study was approved by the institutional ethical committee and abided the Declaration of Helsinki. Written informed consent was obtained from each patient and following data were collected, i.e., age, gender, address, and contact telephone number. History included patients' chief complaints and past history of ocular surgery.

Information on risk factors of systemic disease such as hypertension (140/90 mmHg and above), diabetes (fasting levels above 110 mg/dl) and its duration, cardiovascular disease, and family history of AMD was evaluated. The questionnaire was designed to collect the data on personal history regarding the status of cigarette smoking, the patient was asked how long he had been smoking (years) and the current level (in number of cigarettes, beedies per day, and in hours per day for the hookah) of smoking and alcohol consumption. Anthropometric measurements such as height, weight, and blood pressure of all the participants were measured and documented. Body mass index (BMI) was calculated from the measured height and weight according to the formula: weight (in kilograms) divided by height (in meters) squared. Sample size was calculated by using the prevalence formula n = 4PQ/L2 where P is the prevalence, Q is (100-P), and L is the error, and also by referring the previous prevalence studies.

Inclusion criteria:

All patients above 50 years of age attending the eye outpatient department (OPD) of both sexes
Patient giving consent to participate in the study
Patients were included in the study if they fulfilled anyone of the following diagnostic criteria of AMD.

Presence of soft drusen (distinct or indistinct) of size >63 μ
Presence of hyperpigmentation or hypopigmentation of RPE
Atrophic macular degeneration known as geographic atrophy
Neovascular vessels of choriocapillaris plexus in macular area, exudative pigment epithelial defect, macular scar, or combination of any of three conditions.

The exclusion criteria were as follows:

Patients who did not understand and were not willing to participate in the study
Patients having other retinal and macular diseases
Patients having bilateral media opacities such as corneal dystrophies, corneal degenerations, and mature senile cataract
Patients in whom dilatation of pupil was either contraindicated such as angle-closure glaucoma or who did not dilate.

Distance visual acuity both uncorrected (UCVA) and best corrected (BCVA) were measured by using Snellen chart. C-type charts were used for illiterate individuals. Near visual acuity was measured by using Roman test type chart. External eye examination, assessment of pupillary reaction, and anterior segment examination were performed with a slit lamp. Cataract was graded by the Lens Opacities Classification System III classification. Examination of the disc and macula was done under full mydriasis with a 90-diopter (D) lens in conjunction with slit-lamp; a 20-D lens was used for indirect ophthalmoscopy. Patients diagnosed with AMD were further evaluated with a fundus camera and graded into following four groups based on their findings. Early AMD was defined by the presence of soft distinct or indistinct drusens and by the presence of pigmentary abnormalities which were classified as hypopigmentation or hyperpigmentation or by the presence of large soft drusen 125 μm or more in diameter or a large drusen area >500 μm in diameter circle, or by the presence of large soft indistinct drusen in the absence of signs of late AMD. Neovascular AMD lesions were defined as the presence of RPE detachment, neurosensory detachment, and subretinal or sub-RPE scar tissue. Subretinal hemorrhages within the macular area were considered as sign of neovascular AMD. Geographic atrophy was defined as the presence of visible choroidal vessels and a discrete atrophic area with sharp border and an area of ≥175 μm in diameter. Late AMD was defined as having either neovascular AMD or geographic atrophy.^[6] The patients who were diagnosed as having AMD were subjected to further investigations, e.g., fundus fluorescein angiography and treated if required.

The age- and gender-wise frequencies of AMD were obtained and evaluated for statistical significance of association with the disease using Pearson's Chi-square test. Further, data on other risk factors of AMD such as family history, smoking status, alcohol consumption, hypertension, diabetes, cardiovascular disease, BMI, and prior surgery of cataract were obtained and statistically evaluated against AMD status to determine the significance using Chi-square test. The univariate odds ratios (ORs) were obtained for different levels of each risk factor as a measure of risk associated with the occurrence of AMD. Further, the adjusted ORs were obtained using multivariate logistic regression analysis. The effect of age on AMD was studied in the presence of covariates found significant in univariate analysis.

Results

There were 907 patients who attended the tertiary care center during the study period, of which 21 had macular degeneration, resulting in an occurrence of 2.3% (95% confidence interval [CI] [1.47%–3.48%]). Of which, 15 patients had early AMD (1.6%) and six patients had late AMD (0.7%).

In [Table 1], univariate analysis was done showing the risk of AMD associated with different factors. OR, as a measure of risk of AMD, were obtained for each level of categorical variables. For age, considering 50–60 years as reference age group, the OR for higher age categories increased significantly. For the age group of 81–90 years, the odds in favor of AMD were 9.94 (95% CI: 2.16, 45.76) times higher than that of the reference age group. Other statistically significant risk factors were smoking, cardiovascular disease (CVD), and previous cataract surgery with P = 0.0001. Presence of family history, gender, alcohol, diabetes, hypertension, and obesity were nonsignificant.

Table 1: Univariate analysis showing association of different risk factors with age.related macular degeneration

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Multivariate logistic regression analysis was performed. In the model, those variables showing significant relevance with AMD, i.e., age, smoking habit, CVD, prior and cataract surgery were retained and accordingly the adjusted ORs were obtained. It is evident from the table that compared to the reference age of 50–60 years, the odds associated with age group 61–70 years were 2.62 (95% CI: 0.74–9.21) with P = 0.13. In other words, the risk of AMD associated with age group of 61–70 years is 2.62 times more as compared to that of patients in the age group 50–60 years, although statistically insignificant. Similarly, for age category of 71–80 years, the OR was 4.85 (95% CI: 4.85–19.47] with P = 0.02 implying significant risk to patients in this category as compared to reference age group. Further, for age category of ≥81 years, the OR was 15.26 (95% CI: 3.29–70.68) with associated P < 0.0001. The risk of AMD associated with smoking was 2.23 times more as compared to that of nonsmoking category, although the effect was statistically insignificant with P = 0.12 (P > 0.05). The risk of AMD associated with CVD was 3.58 times higher as compared to that of non-CVD cases, and the effect was statistically significant with P = 0.02 (P< 0.05). The risk of AMD in patients undergone cataract surgery was 6.36 times higher as compared to those who did not underwent cataract surgery, and the effect was highly significant with P < 0.0001.

Discussion

AMD being the prime cause of posterior segment blindness in elderly patients which is difficult to prevent and treat, hence it is essential to identify the risk factors. With the introduction of new and effective treatments for AMD, there is a strong need for early identification, as timely treatment will lead to better visual prognosis.

In our study, the prevalence of AMD was 2.3%. Proportion of early AMD was 1.6% and late AMD was found to be 0.7% which is very similar to Nidhi et al.^[7] Nirmalan et al.^[8] conducted a hospital-based descriptive study in South India. We also found that the occurrence of AMD increases with age in the age group of 50–60 years, the occurrence was 1.06%, which increased to 2.22% in the 61–70 year age group, 3.81% of occurrence was observed in the age group of 71–80 years. Maximum occurrence of AMD was seen in the age group of ≥80 years (9.75%) which was comparable to the study conducted by Vashi et al.^[9] in 2015 stated that all patients above 85 years had the highest prevalence of 6.13%.

In our study, the occurrence of AMD in nonsmokers was 1.90%, and in smokers, it was more than double which was 5%. The association of smoking status with AMD occurrence was found to be statistically significant with P = 0.03 and OR of (2.74 [0.95–6.97] 95% CI). Nidhi et al.^[7] and Krishnaiah et al.^[10] also found that cigarette smoking was constantly associated with AMD, and the study also showed a strong association between AMD and heavy smoking (OR 5.58).

In the present study, we found that the occurrence of AMD was 5.49% in patients with history of CVD as compared to 1.96% in patients without history of CVD. The association between CVD and occurrence of AMD was statistically significant with P = 0.03 and OR of 2.96 (95% CI: 0.93–7.85). Singare et al.^[4] also found the similar association of the prevalence of AMD in patients with history of CVD was highly significant with OR of 2.00, 95% CI 1.21–3.31, P = 0.0058.

In our study, we too found statistically significant association between prior surgery and occurrence of AMD as indicated by P < 0.0001, the odds associated with AMD for patients who underwent cataract surgery were 5.83 (95% CI: 2.39–14.41) times higher than those who had no such prior surgery. In a cross-sectional study conducted by Krishnaiah et al.,^[10] in 2005, found that prior cataract surgery was strongly associated with AMD in bivariate analysis (P< 0.0001) and also in multivariable logistic regression analyses with adjusted OR (95% CI) =3.79 (2.12–6.78). In our study, the presence of family history, gender, alcohol, diabetes, hypertension, and obesity were nonsignificant. Similar results were found in Krishnaiah S et al.,^[10] Kanski JJ^[11] Ho L et al.,^[12] Chakravarthy et al.^[13] and Krishnaiah S et al.^[14]

It would have been ideal if the patients were selected from the community to get a proper prevalence rate. The limitation of our study was that the patients were selected from the OPD of general eye OPD from a rural-based tertiary care center.

Conclusion

In our study, occurrence of AMD is 2.3%. Of which, 1.6% patients had early AMD and 0.7% patients had late AMD. Advanced age of >80 years was found to be the most significant risk factor for AMD with P = 0.0001. The occurrence of AMD was higher in smoking population with P = 0.0357. The other risk factors observed in our study were associated cardiovascular diseases (P = 0.0335) and previous cataract surgery (P ≤ 0.0001).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Annexure ii

Questionaire

1) Do you smoke?

a) Yes

b) No

If yes, duration of smoking ___________

In which form- _____________________________________________________________

amount of smoking- ________________

2) Do you drink alcohol?

a) Yes

b) No

If yes, since how many years _______________

How much alcohol do you drink everyday (ml)?

3) Are you suffering from high blood pressure or Are you taking some anti hypertensive drugs?

a) Yes

b) No If

yes, since how many years do you have the complain of high blood __________________

4) Are you suffering from diabetes mellitus or Are you taking some anti- diabetic drugs?

a) Yes

b) No

If yes, since how many years do you have the complain of diabetes mellitus

5) Are you suffering from any heart disease e.g. heart attack, angina or have undergone any heart operation/procedure?

a) Yes

b) No

6) Have you undergone cataract surgery?

a) Yes

b) No

If yes, for which eye I eyes- Right I left / both How many years back ______________________________

7) Does any of the family member suffer from age related blindness?

a) Yes

b) No

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