Glaucoma is among the leading causes of irreversible blindness worldwide. Precisely because of the risk of permanent vision loss, it is very important to understand how certain systemic conditions may also be associated with or increase the risk of developing glaucomatous disease. Let's look at some of the risk situations.
Inflammatory/autoimmune and infectious diseases
Certain inflammatory or infectious diseases of the eye can lead to the development of glaucoma. These include uveitis, i.e., inflammation of the uveal tissues (iris, ciliary body and choroid), which can cause an increase in intraocular pressure (IOP) due to obstruction and damage to the trabecular tissue, and is a factor in the onset of glaucoma.
Uveitic glaucoma can also be caused by systemic inflammation, which includes human leukocyte antigen B27 (HLA-B27) related diseases such as ankylosing spondylitis, psoriasis, inflammatory bowel disease and reactive arthritis. Other systemic inflammatory conditions known to cause uveitis and possibly glaucoma include juvenile idiopathic arthritis and sarcoidosis.
Furthermore, patients with uveitis have an increased risk of developing glaucoma not only due to the inflammatory nature of the uveitis itself, but also as a result of the use of corticosteroids to treat the condition. Finally, a rarer form of angle-closure glaucoma may result from Vogt-Koyanagi-Harada syndrome, which causes intraocular inflammation and oedema.
Dermatological conditions associated with glaucoma
Dermatological diseases that increase the risk of glaucoma include vitiligo, cutaneous sarcoidosis and cutaneous manifestations of systemic inflammatory diseases.
Vitiligo is an autoimmune disease, characterised by destruction of melatocytes and depigmentation of the macula. Patients with vitiligo may also have ocular pigmentation abnormalities in the retina and iris. Due to the increased risk of developing normal tension glaucoma, documented by numerous studies, frequent eye examinations and close monitoring are recommended.
Ocular sarcoidosis classically presents as anterior uveitis that can lead to uveitic glaucoma. For this reason, patients with sarcoidosis should have frequent eye examinations even in the absence of symptoms.
Finally, many systemic inflammatory diseases have cutaneous manifestations, including rheumatoid arthritis, systemic lupus erythematosus and scleroderma. All of these conditions can have ocular involvement, including retinal vasculitis, uveitis and scleritis. Patients with systemic inflammatory conditions should undergo thorough eye examinations as they are at risk of developing glaucoma as a complication.
Vascular conditions associated with glaucoma
Among the vascular conditions most commonly associated with glaucoma is diabetic retinopathy. This is a complication of diabetes mellitus, in which new abnormal blood vessels grow in the inner retina, which can extend into the vitreous and, in some cases, give rise to neovascular glaucoma. This type of glaucoma is considered an ophthalmic emergency and requires immediate treatment due to the rapid increase in intraocular pressure, with potential loss of vision.
Pulmonary conditions associated with glaucoma
Patients with chronic obstructive pulmonary disease (COPD), asthma and obstructive sleep apnoea may experience increased intraocular pressure. In addition, hypoxia can cause oxidative stress, which is also related to the onset of glaucoma.
Renal conditions associated with glaucoma
Patients with chronic kidney disease (CKD) have been found to have an increased risk of developing eye diseases, including glaucoma. A recent study found that the risk for developing glaucoma in patients with CKD increases with chronicity of the disease. While the causes of this association are still not entirely clear, we know that CKD and glaucoma share many pathogenic conditions, including oxidative stress, dysfunction of the renin-angiotensin system and atherosclerosis, which lead to optic nerve damage.
Neurological conditions associated with glaucoma
Many studies in recent years have explored the relationship between glaucoma and chronic neurodegenerative processes, such as Alzheimer's disease (AD) and Parkinson's disease. The association between glaucoma and AD has been investigated because the two diseases share several common features, including the age-related and irreversible loss of specific types of neurons. Epidemiological studies have shown an increased prevalence of glaucoma in AD patients.
Paediatric and Genetic Diseases
The incidence of glaucoma in the paediatric population is quite rare and most cases of paediatric patients with ocular malformations are associated with genetic syndromes. Genetic causes of early-onset glaucoma are also rare and include juvenile open angle glaucoma, anterior segment dysgenesis, congenital glaucoma and familial normal tension glaucoma. Furthermore, in children, as in adults, glaucoma may be associated with the presence of systemic disease.
In addition to the mechanical damage caused by optic nerve compression, other processes, such as vascular dysfunction of the eye, oxidative stress and neuroinflammation, are also implicated in the pathogenesis of glaucoma, which may also result from the presence of other underlying pathologies. For this reason, an integrated approach in the treatment of glaucoma, including drug therapy and the use of natural products which contain natural antioxidants and possess anti-inflammatory and neuroprotective properties, can be a successful strategy.
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