Effects of vitamin D receptor knockout on cornea epithelium gap junctions

Management of Corneal Haze After Photorefractive Keratectomy

Photorefractive keratectomy (PRK) is a safe and popular corneal surgery performed worldwide. Nevertheless, there is potential risk of corneal haze development after surgery. Proper management of post PRK haze is important for good visual outcome. We performed a comprehensive review of the literature on the various risk factors and treatments for PRK haze, searching the PubMed, Google Scholar, SCOPUS, ScienceDirect, and Embase databases using relevant search terms. All articles in English from August 1989 through April 2023 were reviewed for this study, among which 102 articles were chosen to be included in the study. Depending on the characteristics of and examination findings on post PRK haze, different management options may be preferred. In the proposed framework, management of PRK haze should include a full workup that includes patient's subjective complaints and loss of vision as well as visual acuity, biomicroscopy, anterior segment optical coherence tomography, epithelial mapping, and Scheimpflug densitometry. Topical steroid treatment for haze should be stratified based on early- or late-onset haze. Mechanical debridement or superficial phototherapeutic keratectomy (PTK) may be used to treat superficial corneal haze. Deep PTK and/or PRK can be used to treat deep corneal haze. Mitomycin-C and topical steroids are prophylactic post-surgery agents to prevent recurrence of haze.

Effects of Topical 1,25 and 24,25 Vitamin D on Diabetic, Vitamin D Deficient and Vitamin D Receptor Knockout Mouse Corneal Wound Healing

Delayed or prolonged corneal wound healing and non-healing corneas put patients at risk for ocular surface infections and subsequent stromal opacification, resulting in discomfort or visual loss. It is important to enhance corneal wound healing efficiency and quality. Vitamin D (Vit D) is both a hormone and a vitamin, and its insufficiency has been linked to immune disorders and diabetes. For this study, wound healing and recruitment of CD45+ cells into the wound area of normoglycemic and diabetic mice were examined following corneal epithelial debridement and treatment with 1,25-dihyroxyvitamin D (1,25 Vit D) or 24,25-dihydroxyvitamin D (24,25 Vit D). Treatment with topical 1,25-dihyroxyvitamin D (1,25 Vit D) resulted in significantly increased corneal wound healing rates of normoglycemic, diabetic and diabetic Vit D deficient mice. Furthermore, 24,25-dihydroxyvitamin D (24,25 Vit D) significantly increased corneal wound healing of diabetic Vit D deficient and Vit D receptor knockout (VDR KO) mice. In addition, CD45+ cell numbers were reduced in diabetic and VDR KO mouse corneas compared to normoglycemic mice, and 24,25 Vit D increased the recruitment of CD45+ cells to diabetic mouse corneas after epithelial debridement. CD45+ cells were found to infiltrate into the corneal basal epithelial layer after corneal epithelial debridement. Our data indicate that topical Vit D promotes corneal wound healing and further supports previous work that the Vit D corneal wound healing effect is not totally VDR-dependent.

Topical calcitriol application promotes diabetic corneal wound healing and reinnervation through inhibiting NLRP3 inflammasome activation

Vitamin D (VD) deficiency delays corneal wound healing in those with diabetes, which cannot be rescued with supplemental diet. Here, we employed topical calcitriol application to evaluate its efficiency in corneal wound healing and reinnervation in diabetic mice. Type 1 diabetic mice were topically administrated calcitriol, or subconjunctivally injected with NLRP3 antagonist MCC950 or IL-1β blocking antibody after epithelial debridement. Serum VD levels, corneal epithelial defect, corneal sensation and nerve density, NLRP3 inflammasome activation, neutrophil infiltration, macrophage phenotypes, and gene expressions were examined. Compared with those of normal mice, diabetic mice showed reduced serum VD levels. Topical calcitriol application promoted corneal wound healing and nerve regeneration, as well as sensation recovery in diabetic mice. Moreover, calcitriol ameliorated neutrophil infiltration and promoted the M1-to-M2 macrophage transition, accompanied by suppressed overactivation of the NLRP3 inflammasome. Treatment with NLRP3 antagonist or IL-1β blockage demonstrated similar improvements as those of topical calcitriol application. Additionally, calcitriol administration upregulated desmosomal and hemidesmosomal gene expression in the diabetic cornea. In conclusion, topical calcitriol application promotes corneal wound healing and reinnervation during diabetes, which may be related to the suppression of the overactivation of NLRP3 inflammasome.

Corneal confocal microscopy identifies a reduction in corneal keratocyte density and sub-basal nerves in children with type 1 diabetes mellitus

PURPOSE

To assess whether alterations in stromal keratocyte density are related to loss of corneal nerve fibres in children with type 1 diabetes mellitus (T1DM).

METHODS

Twenty participants with T1DM and 20 age-matched healthy controls underwent corneal confocal microscopy. Corneal sub-basal nerve morphology and corneal keratocyte density (KD) were quantified.

RESULTS

Corneal nerve fibre density (CNFD) (p<0.001), corneal nerve branch density (p<0.001), corneal nerve fibre length (CNFL) (p<0.001) and inferior whorl length (IWL) (p<0.001) were lower in children with T1DM compared with healthy controls. Anterior (p<0.03) and mid (p=0.03) stromal KDs were lower with no difference in posterior KD (PKD) in children with T1DM compared with controls. Age, duration of diabetes, height, weight and body mass index did not correlate with anterior (AKD), mid (MKD) or PKD. Inverse correlations were found between glycated haemoglobin and PKD (r=-0.539, p=0.026), bilirubin with MKD (r=-0.540, p=0.025) and PKD (r=-0.531, p=0.028) and 25-hydroxycholecalciferol with MKD (r=-0.583, p=0.018). CNFD, CNFL and IWL did not correlate with AKD, MKD or PKD.

CONCLUSION

This study demonstrates a reduction in corneal nerves and anterior and mid stromal KD in children with T1DM, but no correlation between corneal nerve and keratocyte cell loss.

Effects of 1,25 and 24,25 Vitamin D on Corneal Fibroblast VDR and Vitamin D Metabolizing and Catabolizing Enzymes

Purpose: To investigate the effects of 1,25-Vit D3 and 24,25-Vit D3 on corneal fibroblast expression of the vitamin D-associated enzymes CYP27B1 and CYP24A1 and the roles of the vitamin D receptor (VDR) and protein disulfide isomerase, family A, member 3 (Pdia3) in these cells.Methods: CYP24A1, CYP27B1, VDR, and Pdia3 expression in corneas was detected using immunohistochemistry. Western blotting was used to measure protein expression in human and mouse fibroblasts, including VDR KO mouse cells, treated with 1,25-Vit D3 (20 nM) and 24,25-Vit D3 (100 nM). The Pdia3 inhibitor LOC14 was used to explore the role of Pdia3 as a Vit D3 receptor in these cells.Results: CYP24A1, CYP27B1, VDR, and Pdia3 were all expressed in mouse and human corneal fibroblasts. 1,25-Vit D3 significantly increased VDR expression in human and mouse fibroblasts. 1,25-Vit D3 and 24,25-VitD3 significantly increased CYP24A1 and CYP27B1 expression level in human, VDR WT mouse, and VDR KO mouse corneal fibroblasts. CYP24A1 and CYP27B1 expression was unchanged in VDR KO mouse fibroblasts treated with 1,25-Vit D3 or 24,25-Vit D3 plus LOC14. Human fibroblast VDR, CYP24A1, and CYP27B1 expression were unaffected by LOC14.Conclusions: Vitamin D metabolic enzymes, VDR, and Pdia3 are all expressed in mouse and human corneal fibroblasts. 1,25-Vit D3 modulates fibroblast vitamin D enzymes through both the VDR and Pdia3 pathways in a species-dependent manner. 24,25-Vit D3 can increase expression of fibroblast CYP24A1 and CYP27B1 in the absence of VDR and is likely involved in fibroblast regulation independent of 1,25-Vit D3 or VDR.

Association of vitamin D with incident glaucoma: findings from the Women's Health Initiative

The relationship between vitamin D and glaucoma is controversial. The objective of this study was to examine women from the Women's Health Initiative (WHI) to determine if there is an association between vitamin D and incident glaucoma in postmenopausal women. We examined the association between dietary vitamin D intake, vitamin D supplements and serum 25 hydroxyvitamin D (25(OH)D) levels and the risk of developing glaucoma. 143,389 postmenopausal women from the WHI including a subset with serum 25(OH) D measurements were examined to determine the association of dietary, supplemental and serum levels of vitamin D to the development of glaucoma. Dietary intakes of vitamin D, use of vitamin D supplements and serum levels of 25(OH) D were predictors examined for the main outcome of incident glaucoma. In multivariable models adjusted for demographic, clinical variables and medication use, dietary vitamin D, vitamin D supplements, total vitamin D intake (diet plus supplements) and serum 25 (OH) D measurements were not significantly associated with incident glaucoma. In the CaD placebo-controlled intervention clinical trial, there was also no association in the active intervention arm with glaucoma. We conclude that dietary vitamin D intake, supplements and serum levels are not significantly related to the risk of developing glaucoma in postmenopausal women.

Genistein-Calcitriol Mitigates Hyperosmotic Stress-Induced TonEBP, CFTR Dysfunction, VDR Degradation and Inflammation in Dry Eye Disease

Dry eye disease (DED) signs and symptoms are causally associated with increased ocular surface (OS) inflammation. Modulation of key regulators of aberrant OS inflammation is of interest for clinical management. We investigated the status and the potential to harness key endogenous protective factors, such as cystic fibrosis transmembrane conductance regulator (CFTR) and vitamin D receptor (VDR) in hyperosmotic stress‐associated inflammation in patients with DED and in vitro. Conjunctival impression cytology samples from control subjects (n = 11) and patients with DED (n = 15) were used to determine the status of hyperosmotic stress (TonEBP/NFAT5), inflammation (IL‐6, IL‐8, IL‐17A/F, TNFα, MMP9, and MCP1), VDR, and intracellular chloride ion (GLRX5) by quantitative polymerase chain reaction and/or immunofluorescence. Human corneal epithelial cells (HCECs) were used to study the effect of CFTR activator (genistein) and vitamin D (calcitriol) in hyperosmotic stress (HOs)‐induced response in vitro. Western blotting was used to determine the expression of these proteins, along with p‐p38. Significantly, higher expression of inflammatory factors, TonEBP, GLRX5, and reduced VDR were observed in patients with DED and in HOs‐induced HCECs in vitro. Expression of TonEBP positively correlated with expression of inflammatory genes in DED. Increased TonEBP and GLRX5 provides confirmation of osmotic stress and chloride ion imbalance in OS epithelium in DED. These along with reduced VDR suggests dysregulated OS homeostasis in DED. Combination of genistein and calcitriol reduced HOs‐induced TonEBP, inflammatory gene expression, and p‐p38, and abated VDR degradation in HCECs. Henceforth, this combination should be further explored for its relevance in the management of DED.

Serum 25-Hydroxy Vitamin D, Vitamin B12, and Folic Acid Levels in Progressive and Nonprogressive Keratoconus

PURPOSE

To evaluate the serum 25-hydroxy vitamin D, vitamin B12, and folic acid (FA) levels in progressive and nonprogressive patients with keratoconus (KCN).

METHODS

Fifty-five patients with KCN (28 progressive and 27 nonprogressive) who were followed up for at least 12 months were recruited and separated into 2 groups according to corneal topographic progression criteria. Age- and sex-matched 30 healthy individuals formed the control group. Serum vitamin D, B12, FA, and Ca levels were compared among control, nonprogressive, and progressive groups. The effect of gender, age, vitamin D, B12, and FA parameters on KCN progression was investigated.

RESULTS

Serum vitamin D levels were 12.77 ± 5.52, 11.78 ± 4.32, and 17.40 ± 5.12 ng/mL in nonprogressive, progressive, and control groups, respectively. The serum vitamin D levels in KCN groups (nonprogressive and progressive) were significantly lower than the control group (P = 0.002 and P < 0.001, respectively). There was no significant difference between all groups in serum vitamin B12, FA, and Ca levels (P > 0.05). Decreased vitamin D levels significantly increased nonprogressive KCN probability 1.23 times and progressive KCN probability 1.29 times more than the control group (P = 0.002, 95% confidence interval, 0.708-0.925; P < 0.001, 95% confidence interval, 0.668-0.888, respectively).

CONCLUSIONS

Serum vitamin D levels were significantly decreased in both KCN groups. However, serum vitamin B12, FA, and Ca levels were similar in all groups. Serum vitamin D evaluation of patients with KCN at onset and follow-up examinations may help to predict the course of the disease.

Association between vitamin D and dry eye disease: A systematic review and meta-analysis of observational studies

PURPOSE

A number of studies have examined the association between vitamin D and dry eye disease in different populations, but findings are inconclusive. Herein, available observational studies were systematically reviewed to elucidate the overall relationship between vitamin D and dry eye disease among adult population.

METHODS

PubMed, Scopus, Google scholar and ISI web of science databases were searched until January 2020 for studies assessing the association between vitamin D and dry eye disease. The Newcastle-Ottawa Quality Assessment Scale was used to examine the quality of each study.

RESULTS

A total of 14 studies out of 252 met the inclusion criteria and were included in this systematic review and meta-analysis. Serum 25(OH) D3 was lower in dry eye disease subjects compared to healthy ones (WMD -5.93; 95 % CI, -7.47 to -4.40; P < 0.001) with evidence of significant heterogeneity (I² = 94.6 % p < 0.001). Also, in final analysis, vitamin D correlated significantly with ocular surface disease index (Fisher's Z: -0.26; 95 % CI, -0.48 to -0.04; P = 0.018), with significant heterogeneity between studies (I² = 59.3 %, P = 0.043).

CONCLUSION

It was found that serum vitamin D had a significantly lower level in dry eye disease patients, and correlated with ocular surface disease index but no other dry eye disease parameter. The findings add to the existing literature supporting the concept that nutrition especially vitamin D plays an important role in human eye health. Prospective studies are needed to confirm this relationship.

Transient Cell Membrane Disruptions induce Calcium Waves in Corneal Keratocytes

The purpose of this study was to determine if transient cell membrane disruptions (TPMDs) in single keratocytes can trigger signaling events in neighboring keratocytes. Stromal cells were cultured from human corneas (HCSC) and mouse corneas (MCSC). TPMDs were produced using a multiphoton microscope in Cal-520-AM loaded cells. TPMD-induced calcium increases (Ca⁺⁺_i) were measured in Ca⁺⁺-containing and Ca⁺⁺-free solutions containing thapsigargin, ryanodine, BAPTA-AM, 18-α-glycyrrhetinic acid (18α-GA), apyrase, BCTC, AMG 9810, or AMTB. Fluorescence intensity was recorded as the number of cells responding and the area under the fluorescence versus time curve. The maximum distance of responding neighboring cells in ex vivo human corneas was measured. Connexin 43 protein in HCSC and MCSC was examined using immunofluorescence staining, and corneal rubbing was applied to confirm whether TPMDs occur following mechanical manipulation. Our results demonstrate that single cell TPMDs result in Ca⁺⁺ waves in neighboring keratocytes both in culture and within ex vivo corneas. The source of Ca⁺⁺ is both intra-and extra-cellular, and the signal can be mediated by ATP and/or gap junctions, and is species dependent. Stromal rubbing confirmed that TPMDs do occur following mechanical manipulation. Keratocyte TPMDs and their associated signaling events are likely common occurrences following minor or major corneal trauma.

Influence of Vitamin D on Corneal Epithelial Cell Desmosomes and Hemidesmosomes

Purpose

We have observed noticably weak epithelial attachment in vitamin D receptor knockout mice (VDR KO) undergoing epithelial debridement. We hypothesized that VDR KO negatively affects corneal epithelial cell desmosomes and/or hemidesmosomes.

Methods

Transcript levels of desmosome and hemidesmosome proteins in VDR KO corneas were assessed by qPCR. Western blotting and immunochemistry were used to detect proteins in cultured cells exposed to 1,25(OH)₂D3 and 24R,25(OH)₂D3.

Results

VDR KO resulted in decreased corneal desmosomal desmoglein 1 (DSG1) and desmocollin 2 (DSC2) mRNA, and hemidesmosomal plectin mRNA. DSG1 and plectin protein expression were reduced in VDR KO corneas. DSG1 protein expression increased in VDR wild types (VDR WT) and VDR KO mouse primary epithelial cells (MPCEC) treated with 1,25(OH)₂D3 and 24R,25(OH)₂D3. 24R,25(OH)₂D3 treatment resulted in increased plectin and integrin β4 levels in VDR WT MPCEC, and decreased levels in VDR KO MPCEC. Treatment of human corneal epithelial cells (HCEC) with 1,25(OH)₂D3 and 24R,25(OH)₂D3 resulted in increased DSC2 and DSG1 protein expression. Plectin and integrin β4 were only increased in 24R,25(OH)₂D3 treated HCEC.

Conclusions

VDR KO results in reduced desmosomal and hemidesmosomal mRNA and protein levels. 1,25(OH)₂D3 and 24R,25(OH)₂D3 increased DSG1 protein in all cells tested. For hemidesmosome proteins, 24R,25(OH)₂D3 increased plectin and integrin β4 protein expression in VDR WT and HCEC, with decreased expression in VDR KO MPCEC. Thus, vitamin D3 is involved in desmosome and hemidesmosome junction formation/regulation, and their decreased expression likely contributes to the loosely adherent corneal epithelium in VDR KO mice. Our data indicate the presence of a VDR-independent pathway.

Serum 25-Hydroxyvitamin D, Selenium, Zinc and Copper in Patients with Keratoconus

PURPOSE

To assess the possible association between keratoconus (KC) and serum levels of 25-hydroxyvitamin D (25OHD), Selenium (Se), Zinc (Zn), and Copper (Cu) and to compare it with age-matched healthy subjects.

METHODS

One hundred patients with KC and 100 normal subjects were included. The two groups were compared for serum 25OHD and serum levels of three trace elements: Se, Zn, and Cu. These factors were also compared between groups with different KC stages.

RESULTS

Serum levels of vitamin D, Zn, Cu, and Se were significantly different between the KC and normal groups (P = 0.006, P = 0.015, P = 0.004, and P = 0.038, respectively). Although a lower level of 25OHD was found in severe stages of KC, it was not significantly different among different KC groups (P = 0.441). KC stage groups were not significantly different for mean serum Zn, Cu, and Se (P = 0.130, P = 0.98, P = 0.113, respectively). Although the Cu/Zn ratio was higher in cases than in controls, there was no significant difference between the two groups and between KC stages (P = 0.168, P = 0.143, respectively).

CONCLUSION

Lower serum 25OHD, Cu, Zn, and Se were found in the KC group compared to the control group. The results of this study suggest that a lower antioxidative activity may be involved in the possible etiology of KC.

Vitamin D receptor and metabolite effects on corneal epithelial cell gap junction proteins

Vitamin D is a fat-soluble prohormone that can be activated both systemically and within individual tissues. Our lab has previously demonstrated that the corneal epithelium can activate vitamin D and that the vitamin D metabolites 1,25(OH)₂D3 and 24R,25(OH)₂D3 can affect corneal epithelial migration, proliferation, and tight and gap junction function. These vitamin D-derived metabolites signal through the vitamin D receptor (VDR). The purpose of this study was to specifically determine the effects of 1,25(OH)₂D3 and 24R,25(OH)₂D3 on corneal epithelial cell gap junction proteins. Connexin (Cx) 26, 30 and 43 protein expression was detected in a human corneal epithelial cell line (HCEC), wild type and vitamin D receptor knockout (VDR^-/-) mouse corneas, and cultured mouse primary epithelial cells (MPCEC). In vitro gap junction function was assessed using the scrape loading/dye transfer assay. HCEC and MPCEC were treated with 1,25(OH)₂D3 or 24R,25(OH)₂D3. Western blotting was used to detect gap junction proteins. Vitamin D3 effects on epithelial intracellular Ca⁺⁺ (Ca⁺⁺_i) were determined using the dye Cal-520. Cx26 and Cx43 protein levels were significantly increased in HCEC and MPCEC treated with both 1,25(OH)₂D3 and 24R,25(OH)₂D3. Cx30 and Cx43 protein levels were also significantly increased in VDR^-/- MPCEC. In vitro gap junction connectivity was significanlty enhanced in HCEC and MPCEC cultured with 24R,25(OH)₂D3 and 1,25(OH)₂D3. Ca⁺⁺_i was not affected by 1,25(OH)₂D3 or 24R,25(OH)₂D3 in HCEC or MPCEC. We conclude that both 1,25(OH)₂D3 and 24R,25(OH)₂D3 are positive regulators of connexin proteins and gap junction communication in the corneal epithelium. These vitamin D metabolites appear to signal through both VDR-dependent and -independent pathways. The effects of vitamin D on corneal epithelial gap junctions do not seem to be dependent on Ca⁺⁺_i.

Are Serum Vitamin D Levels Associated With Dry Eye Disease? Results From the Study Group for Environmental Eye Disease

Objectives

Dry eye disease (DED) is an increasingly important public health problem in Korea. Previous studies conducted in Korea have reported inconsistent results regarding the protective effects of vitamin D on DED, and these discrepancies may be related to the relatively simple questionnaire that has been used. Thus, we evaluated the association of serum vitamin D levels with DED using the ocular surface disease index (OSDI).

Methods

The present study evaluated data from participants in the Study Group for Environmental Eye Disease (2014-2015). This group included data from 752 participants, and data from 740 participants (253 men and 487 women) were analyzed in the present study. DED severity was evaluated using the OSDI.

Results

Higher serum vitamin D levels were associated with a non-significantly reduced risk of DED in the crude analysis (odds ratio [OR], 0.991; 95% confidence interval [CI], 0.971 to 1.011) and in the adjusted analysis (OR, 0.988; 95% CI, 0.966 to 1.010). In the crude analysis of no/mild DED vs. moderate/severe DED, men exhibited a decreased risk with increasing serum vitamin D levels (OR, 0.999; 95% CI, 0.950 to 1.051), while women exhibited an increased risk (OR, 1.003; 95% CI, 0.979 to 1.027). In these analyses, we found no significant associations.

Conclusions

The findings of the present study support previous reports that serum vitamin D levels are not associated with DED.

Vitamin D Replacement Improves Tear Osmolarity in Patients with Vitamin D Deficiency

BACKGROUND

Vitamin D deficiency is a common health problem worldwide. Many parts of the human eye, including the epithelium of the cornea, lens, ciliary body, and retinal pigment epithelium, as well as the corneal endothelium, ganglion cell layer, and retinal photoreceptors, contain vitamin D receptor (VDR). Dry eye is also a common health problem. An adequate tear film is required for maintaining health and function of the eye. Tear hyperosmolarity is considered to be the cause of ocular surface inflammation, symptoms, and tissue damage. It is well-documented that vitamin D has an anti-inflammatory action. We aimed to investigate the effect of vitamin D replacement on tear osmolarity in patients with vitamin D deficiency.

METHODS

A total of 44 patients (38 females, six males, mean age:43.5 ± 12.8 years) with vitamin D deficiency currently managed by the Endocrinology and Metabolism Department of Diskapi Training and Research Hospital in Turkey were enrolled in the study. Patients were given 50,000 units of 25(OH)D₃ intramuscularly, once weekly, over a period of eight weeks. All of the patients underwent tear function osmolarity (TFO) measurement initially and eight weeks after vitamin D replacement. Demographic, anthropometric, and biochemistry data of patients were recorded.

RESULTS

The mean TFO was significantly decreased (313.7 ± 17.3 mOsm/L; 302.7 ± 14.2 mOsm/L, p<0.001) at the end of the second month; 25(OH)D₃ concentrations increased from 8.3 ± 3.5 ng/mL to 68.8 ± 22.3 ng/mL (p<0.001). The mean levels of hsCRP, FPG, P were 2.5 ± 2.5 mg/L, 5.09 ± 0.48 mmol/L, 1.06 ± 0.16 mmol/L initially, and 3.8 ± 5.9 mg/L, 5.11 ± 0.68 mg/dL, 1.09 ± 0.16 mmol/L after vitamin D replacement, respectively (p>0.05). The mean Ca level was 2.37 ± 0.07 mmol/L initially and 2.35 ± 0.07 mmol/L after vitamin D replacement (p<0.05). The change of TFO was negatively correlated with the variation of 25(OH)D₃ before and after replacement in patients with dry eye disease (r=-0.390, p=0.049).

CONCLUSIONS

As a consequence of the presence of VDR and 1α-hydroxylase in different parts of the eye, vitamin D replacement improves tear hyperosmolarity that is considered to be induced by ocular surface inflammation.

Low Serum 25-Hydroxyvitamin D Levels Are Associated with Dry Eye Syndrome

Background

Dry eye syndrome (DES) is a common tear film and ocular surface disease that results in discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. Systemic diseases associated with DES include diabetes mellitus, rheumatoid arthritis, depression, anxiety, thyroid disease, allergic diseases, irritable bowel syndrome, chronic pain syndrome, and hyperlipidemia. Interestingly, it has been found that most of these are associated with low levels of serum 25-hydroxyvitamin D (25(OH)D) or inadequate sunlight exposure.

Methods

In this cross-sectional data analysis, noninstitutionalized adults aged ≥19 years (N = 17,542) who participated in Korean National Health and Nutrition Examination Survey 2010–2012 were included. Information regarding duration of sunlight exposure was collected from the survey participants. Serum 25(OH)D and zinc levels were measured. The confounding variables were age, gender, sunlight exposure time, region of residence, obesity, serum 25(OH)D level, diabetes mellitus, rheumatoid arthritis, depression, thyroid disorder, atopic dermatitis, history of ocular surgery, regular exercise, and walking exercise.

Results

Mean serum 25(OH)D levels of subjects with and without DES were 16.90 ± 6.0 and 17.52 ± 6.07 (p<0.001). Inadequate sunlight exposure time (odds ratio [OR], 1.554; 95% confidence interval [CI], 1.307–1.848), urban residence (OR, 1.669; 95% CI, 1.456–1.913), indoor occupation (OR, 1.578; 95% CI, 1.389–1.814), and low serum 25(OH)D level (OR, 1.158; 95% CI, 1.026–1.308) were the risk factors for DES. After adjusting for age, sex, obesity, diabetes mellitus, rheumatoid arthritis, depression, thyroid disorder, atopic dermatitis, history of ocular surgery, regular exercise, and occupation, low serum 25(OH)D level (OR, 1.178; 95% CI, 1.010–1.372) and deficient sunlight exposure time (OR, 1.383; 95% CI, 1.094–1.749) were the risk factors for diagnosed DES.

Conclusion

Low serum 25(OH)D levels and inadequate sunlight exposure are associated with DES in Korean adults. These results suggest that sufficient sunlight exposure or vitamin D supplementation may be useful in DES treatment.

Vitamin D: Implications for ocular disease and therapeutic potential

Vitamin D is a multifunctional hormone that is now known to play a significant role in a variety of biological functions in addition to its traditional role in regulating calcium homeostasis. There are a large number of studies demonstrating that adequate vitamin D levels are important in maintaining health and show that vitamin D is able to be utilized at local tissue sites. In the eye, we have increasing evidence of the association between disease and vitamin D. In this narrative review, we summarize recent findings on vitamin D and its relationship to various ocular pathologies and the therapeutic potential for some of these, as well as examine the basic science studies that demonstrate that vitamin D is biologically relevant in the eye.