|Year : 2022 | Volume
| Issue : 1 | Page : 18-23
Estimation of serum mineral levels in age-related macular degeneration
CS Sandhya1, N G Prasoona Devi2, Madhusudana Pulaganti1, GK Shambhavi1, V Padmavathi1, J Sri Lalitha1
1 Department of Ophthalmology, S V Medical College, Tirupati, Andhra Pradesh, India
2 Research Scientist- I, Multi-Disciplinary Research Unit(MDRU), S V Medical College, Tirupati, Andhra Pradesh, India
|Date of Submission||20-Dec-2021|
|Date of Decision||26-Apr-2022|
|Date of Acceptance||27-Apr-2022|
|Date of Web Publication||05-Oct-2022|
Dr. N G Prasoona Devi
Department of Ophthalmology, S V Medical College, Tirupati - 517 507, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: Age-related macular degeneration (ARMD) is a highly prevalent progressive retinal disorder which has multiple genetic, environmental, and nutritional risk factors, but the exact etiology is not yet fully understood. To unravel the mysterious etiology of ARMD, more than 100 different compounds have been analyzed in the blood, serum, plasma, aqueous, and vitreous humor for their association with AMD. The present study aims to estimate the serum levels of zinc (Zn), manganese (Mn), and selenium (Se) in ARMD patients when compared to normal. Aim: The aim of this study is to estimate the serum levels of Zn, Mn, and Se in ARMD patients and age-matched controls and to find out if any homeostatic alterations of these minerals occur in ARMD patients when compared to controls. Study Design: An observational study (pilot study). Methodology: 50 ARMD patients and 60 age matched controls included in the study were subjected to a detailed ocular examination . Fundus photography and Ocular Coherence Tomography were done in all ARMD patients. 5 ml of blood sample was collected from all cases and controls and sent for the estimation of serum levels of Zn, Mn, and Se. The results obtained were subjected to statistical analysis. Results: There was no statistically significant difference in the mean serum levels of Zn and Se between cases and controls. However, serum Mn showed a higher level in controls when compared to cases, and the difference was statistically significant. Conclusion: The present study showed a causal relationship between serum Mn level and ARMD.
Keywords: Age-related macular degeneration, manganese and selenium, serum levels of zinc
|How to cite this article:|
Sandhya C S, Devi N G, Pulaganti M, Shambhavi G K, Padmavathi V, Lalitha J S. Estimation of serum mineral levels in age-related macular degeneration. J Ophthalmol Clin Res 2022;2:18-23
|How to cite this URL:|
Sandhya C S, Devi N G, Pulaganti M, Shambhavi G K, Padmavathi V, Lalitha J S. Estimation of serum mineral levels in age-related macular degeneration. J Ophthalmol Clin Res [serial online] 2022 [cited 2023 Mar 21];2:18-23. Available from: http://www.jocr.in/text.asp?2022/2/1/18/357894
| Introduction|| |
The retina is highly susceptible to oxidative stress because of its high consumption of oxygen, its high proportion of polyunsaturated fatty acids, and its exposure to visible light. Oxidative stress can lead to the accumulation of debris and ultimately cell death in retinal pigment epithelium, which is manifested as drusen and geographic atrophy of age-related macular degeneration (ARMD). Several studies reported decreased antioxidant levels and elevated levels of oxidized proteins or lipids indicating oxidative stress in ARMD.,> Zinc (Zn) stabilizes proteins and reduces their vulnerability to oxidation. Several studies reported elevated cadmium levels in the blood and aqueous humor in ARMD patients.,> Both Zn and manganese (Mn) play a key role in reducing the uptake and accumulation of toxic cadmium. Glutathione peroxidase, which is an antioxidant, is dependent on the presence of essential heavy metal selenium (Se).,, Thus, there is a possibility of alteration of these three essential elements, Zn, Mn, and Se, in the eyes as well as in the blood and serum of ARMD patients. The study of alteration in the levels of these three essential trace elements in the blood and serum would be beneficial in the diagnosis and management of ARMD.
| Methodology|| |
Ethical and scientific committee approval was obtained for conducting the study. Fifty patients with different grades of ARMD and 60 age-matched controls were included in the study as per the inclusion criteria. Written informed consent was taken from all the cases and controls.
After taking a relevant and detailed ocular and systemic history from all the subjects, best-corrected visual acuity was noted. Anterior segment examination was conducted by slit-lamp biomicroscopy (CARL ZEISS MEDITEC AG 07740, Jena, Germany). The posterior segment was examined using +90D lens (Ocular Instruments Inc., USA) under a slit lamp with a special focus on the macular area. Cases diagnosed to have ARMD were further subjected to Optical Coherence Tomography (OCT) by spectral domain OCT ,Primus ,Carl Zeiss [Figure 1], [Figure 2], [Figure 3]. Documentation of the fundus findings was done with a fundus camera ( Model CF 1 ,CANON inc. Tokyo, Japan). The patients suspected to have choroidal neovascular membrane were further subjected to fundus fluorescein angiography, and the diagnosis was confirmed.
|Figure 1: OCT picture showing ARMD with drusenoid pigment epithelial detachment, (white arrow) showing RPE elevation, (*) showing drusen. ARMD: Age-related macular degeneration, OCT: Optical coherence tomography, RPE: Retinal pigment epithelium|
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|Figure 2: OCT picture of macula showing geographic atrophy, (white arrow) showing chorioretinal atrophy, (*) showing drusen. OCT: Optical coherence tomography|
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|Figure 3: OCT picture of macula showing wet ARMD, (white arrow) showing CNVM, (*) showing sub-retinal fluid. OCT: Optical coherence tomography, ARMD: Age-related macular degeneration|
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Grading of ARMD was done based on AREDS classification [Table 1].
|Table 1: Grading of age-related macular degeneration based on age-related eye disease study|
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5 ml of the venous blood sample was collected from both the cases and controls and was subjected to analysis for serum levels of Zn, Mn, and Se. Mn and Se levels were assessed at the National Institute of Nutrition, Hyderabad, by atomic absorption spectroscopy. Serum Zn levels were analyzed by an autoanalyzer (Biosystem A-25, Spain) at MDRU-SVMC.
The obtained serum levels of both the cases and controls were subjected to statistical analysis.
Statistical analysis was done with IBM SPSS 25.0 (IBM Corp released version 25 in 2017. IBM SPSS Statistics for Windows Armonk, New York). The Kolmogorov–Smirnov test and Mann–Whitney U-test were applied to arrive at a conclusion.
| Observation and Results|| |
Among 50 ARMD patients included in the study, a majority of 26 patients were in the age group of 51–60 years [Figure 4].
As age increased, the severity of ARMD also increased [Figure 5].
|Figure 5: Mean age distribution among different categories of ARMD. ARMD: Age-related macular degeneration|
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Among the patients' group, 26 were female and 24 were male. There was no significant difference with respect to gender [Figure 6].
Out of 50 patients, 37 (74%) had ARMD in both eyes, whereas in six patients (12%), the disease was unilateral [Figure 7].
Out of 50 patients with ARMD, 29 were residing in rural areas and 21 were from urban areas [Figure 8].
Smoking is very rare among females from this part of the country, so we have considered only males to study the effect of smoking. Out of 24 male patients included in the study, 11 were smokers (46%) and 13 were nonsmokers (54%) [Figure 9].
A maximum of 16 patients had category 2 ARMD followed by 12 each in category 3 and 4, while only 10 patients belonged to category 1 [Figure 10].
Among 12 Grade 4 ARMD patients, 7 had wet ARMD, whereas 5 showed dry ARMD [Figure 11].
|Figure 11: Distribution of wet and dry ARMD among Grade 4 ARMD patients. ARMD: Age-related macular degeneration|
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The mean serum Zn levels among controls were higher when compared to the level in patients, but the difference was not statistically significant [Figure 12] and [Figure 13].
|Figure 12: Box plot showing serum zinc levels among cases and controls. Serum zinc median value, lower, and upper quartile were higher in cases when compared with controls|
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|Figure 13: Box plot showing serum manganese levels among cases and controls. Serum manganese levels were more consistent in cases when compared with controls. The lower, median, and upper quartile were lesser in cases when compared with controls|
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The mean serum Mn levels among controls were higher when compared to the level in patients, and the difference was statistically significant [Figure 14] and [Figure 15].
The mean serum Se levels among controls were higher when compared to the level in patients, but the difference was not statistically significant [Figure 16] and[Figure 17].
|Figure 16: Box plot showing serum selenium levels among cases and controls. Serum selenium median value, lower quartile, upper quartile, and consistency of interquartile range were higher in cases than that of controls|
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In six patients (12%), there was no view of the fundus because of the presence of mature cataract in one eye. One patient had a unilateral full-thickness macular hole.
The data on Zn, Se, and Mn were significantly different from normal distribution (evidenced by the Kolmogorov–Smirnov test which had P < 0.05), and hence, comparison between the cases and controls was made using Mann–Whitney U-test, which is a nonparametric test. In all the tests, the null hypothesis is that the data distribution is normal.
As summarized [Table 2], no statistically significant difference was found between cases and controls in case of Zn and Se. In contrast, a significant difference was observed in the case of Mn with cases showing a lower mean than controls.
|Table 2: Summary results and comparison of various parameters between cases and controls|
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| Discussion|| |
In the present study, 50 cases of different categories of ARMD and above 50 years of age were studied, and the mean age of the patients in the study was 63.8 years. In AREDS2 study, the mean age of the patients was 74 years. In the present study, the mean age of category 1 patients was 61.9 years; in category 2, it was 62.3 years, 64.3 years in category 3, and 66.9 years in category 4. This shows that as age increases, the severity of the disease also increases. This is similar to the Andhra Pradesh Eye Disease study done by Krishnaiah et al. in 2005. The Aravind Comprehensive Eye Study by Nirmalan et al. in 2004 had similar findings. The prevalence of late ARMD increased with increasing age.
No significant gender difference was found in the study population in the present study, with 26 out of 50 (52%) patients being female and 24 (48%) being male. This is similar to the results of other studies such as ARMD, etiology, pathogenesis, and therapeutic strategies by Ambati et al., The Aravind Comprehensive Eye Study by Nirmalan et al. in 2004, all of which did not found any association between gender and ARMD. In a study by Kochami in 2018, (analytical study of prevalence and risk factors for ARMD in a tertiary eye care center), 55% were female and 45% were male.
In the present study, 74% of the patients had ARMD in both eyes, whereas 12% of the patients showed unilateral ARMD. The prevalence and determinants of ARMD in the 80 years and older population: A hospital-based study in Maharashtra, India by Sucheta R Kulkarni et al. ARM was unilateral in 64 (29.2%) and bilateral in 155 (70%) of patients.
Smoking was found in 22% of patients in the present study; 11 out of 24 males in the present study were smoker. Smoking is a consistent risk factor for ARMD according to ARMD etiology, pathogenesis, and therapeutic strategies by Ambati et al.
In the present study, 14% of the patients had wet type of ARMD. Among 12 patients who belonged to category 4, seven had the wet type of AMD, and the remaining five showed dry AMD. In an Analytical Study of Prevalence and Risk factors for ARMD by Kochami. Among patients with late ARMD, dry type was noted in 38.4%, and eight patients had neovascularization.
In the present study, though serum levels of Zn, Mn, and Se were low in the ARMD group when compared to the control group, only the difference in Mn levels was found to be statistically significant. Risk factors for neovascular ARMD from Archives of Ophthalmology Dec 1992 showed no support for Zn levels as a risk factor for ARMD. In a pilot study of homeostatic alterations of mineral elements in the serum of patients with ARMD through elemental and isotopic analysis using inductively coupled plasma (ICP)-mass spectrometry, higher serum concentrations of Zn were established in AMD.
In a study by Jünemann et al., PLOS One 2013 levels of aqueous humor trace elements in patients with nonexudative ARMD the aqueous levels of Mn, Se, and Zn measured by using Flow-injection-ICP-mass-spectrometry, higher aqueous Zn levels were found in patients with ARMD whereas no significant differences were observed in aqueous humor levels of Mn and Se between patients with and without ARMD.
In a study by Tsang et al. Doc. Ophthalmol. 1992 serum levels of antioxidants and ARMD, there was a borderline association between ARMD and serum Se levels.
Whole-blood Se in exudative age-related maculopathy by Mayer et al. showed that Se concentration was significantly lower in the ARM group (186.6 μg/l) than that in controls (207 μg/l). In the present study, the mean Se was 107.48 ng/ml in the AMD group, and it was 119.28 ng/ml in the control group. No statistically significant protective effect was found for Se individually in a study entitled Antioxidant status and neovascular. age-related macular degeneration.
| Conclusion|| |
A statistically significant difference of mean serum Mn level was noted in the study between the case and the control groups, which could mean that the deficiency of Mn could be one of the risk factors for ARMD. However, as this being a pilot study, involving a small sample size, similar larger studies are recommended to establish a causal relationship between the serum Mn level and ARMD.
Financial support and sponsorship
We are thankful to the Department of Health Research Government of India and Multidiscipilinary Research Unit S.V. Medical College Tirupati, for financial support.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17]
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