Bad oral health can cause blindness!

We have tired ourselves out explaining to patients that maxillary tooth extraction does not affect eyesight. However, new research reveals that bad oral health does!

Glaucoma – the silent thief of sight

Retina is the part of the eye responsible for vision. With more than a million nerve fibers, the optic nerve connects the retina to the brain. Glaucoma is a group of diseases of the optic nerve that slowly cause a loss of vision and can lead to blindness. This occurs due to degenerative changes in both retinal ganglion cells and optic nerve, mostly due to high intraocular pressure. Primary open-angle glaucoma (POAG) is the most common glaucoma type followed by primary closed-angle glaucoma (PCAG).

Primary open-angle glaucoma is the leading cause of blindness globally. A whooping 60 million people are visually impaired due to glaucoma.

Etiology

Although its etiology is still not sufficiently understood, there are numerous genetic and environmental risk factors for developing glaucoma such as:

• positive family history
• race – being Black, Asian or Hispanic
• age -being over age 60
• high intraocular pressure
• irregular lifestyle
• poor sleep quality
• eye conditions – extremely thin cornea, very high myopia/hypermetropia
• corticosteroid use
• comorbidities – such as diabetes, heart disease, high blood pressure and sickle cell anemia
• diet – low in antioxidants, nitrates & vit B3
• exercise – low intensity, yoga with head below heart positions

One more risk factor has been recently added to this list – periodontitis.

Connection between oral health and glaucoma

Oral infections, leading to tooth loss or periodontal disease, have been related to a multitude of systemic diseases, such as diabetes, cardiovascular disease, rheumatoid arthritis, certain cancers and neurodegenerative diseases like such as Alzheimer's and Parkinson's diseases.

• Periodontitis is associated with systemic endothelial dysfunction, which has been implicated in glaucoma as well.
• Periodontitis is associated with impaired flow-mediated vasodilation, associated with glaucoma too.

This pushed researches to study a possible connection between chronic periodontitis and glaucoma, namely POAG type of glaucoma.

A population-based study in Taiwan (3), published in Nature Research, 2020 and conducted on 194,090 adults analyzed the occurrence of glaucoma in individuals with periodontitis and without periodontitis. Results showed that:

• Compared to people without periodontitis, the presence of periodontitis was associated with a significant risk of glaucoma.
• As expected, the risk of glaucoma increased in older people, those with comorbidity, and those with corticosteroid use.
• However, glaucoma was more likely in the periodontitis group than in the group without periodontitis – regardless of age, sex, presence of comorbidity, or corticosteroid use.
• Moreover, patients with periodontitis had more association with POAG than PCAG.

It is important to note that it is periodontitis – not dental caries – that is associated with glaucoma, which can ultimately cause blindness if left untreated. Which brings us to the next question – how is periodontitis associated with so many systemic illnesses?! It is because of the underlying body mechanisms, similar to those causing ‘referral pain’.

Mechanisms causing this strange association of oral health and glaucoma

There are several mechanisms underlying the association of periodontitis with systemic illnesses, such as glaucoma.(4)

1. Periodontitis is a common bacteria-induced oral inflammatory condition that destabilizes the tooth structural support apparatus and it can produce transient bacteremia, which may lead to systemic endothelial dysfunction and chronic inflammatory responses in various extra-oral tissues.
2. Second, inflammatory markers generated from the affected periodontal tissue can also travel via the bloodstream to reach other tissue beds like the eye. For example, in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, there is growing evidence that peripheral inflammation exacerbates the development of neuronal cell loss.
3. The third mechanism is the immune response to the bacteria, which involves the generation of antibodies to bacteria and their toxins, which may have off-target effects in extra-oral tissues (e.g., cross-reactive antibodies that contribute to atherosclerosis).

In simple words – Periodontitis may trigger a series of events where the bacteria from the inflamed gums spreads to the optic nerve. This can cause pressure on the optic nerve, putting the patient at a high risk for glaucoma. Hence it’s important to ensure that any infection in that area be treated as quickly as possible to avoid its spread.

What can a responsible dentist do?

• For patients with chronic periodontitis, insist on regular dental exams and scalings. Counsel the patient that this is important to keep their mouth healthy and lower chances of infection spreading to other parts of body.
• If any dental procedure requires sedation in a glaucoma patient, you should avoid sedatives that contain ingredients that can increase pressure in the optic nerve. These includes benzodiazepine sedatives such as diazepam, alprazolam and triazolam.
• In cases of trigeminal neuralgia coupled with periodontitis, avoid using topiramate. Topiramate is contraindicated in glaucoma and if the patient has poor oral health, he is at risk for developing glaucoma.
• If a patient has extreme chronic periodontitis, suggest an ophthalmic examination to him. If such a patient complains of blurry vision, eye pain, redness or halos around eyes, refer him to an ophthalmologist immediately with a note explaining the possibility of glaucoma in chronic periodontitis patients.
• If the patient gives a history of anti-depressant use, and has extreme chronic periodontitis, refer him to his psychiatrist with a note explaining the possibility of glaucoma in chronic periodontitis patients. Tricyclic antidepressants such as amitriptyline are contraindicated in patients with glaucoma or at risk, and the psychiatrist may consider changing his medication if necessary.

To conclude

Bad oral health can cause devastating effects in extra oral tissues and body systems too. People with periodontitis are at a greater risk of glaucoma than individuals without periodontitis. Ocular health exams and good oral health maintenance should be emphasized for such patients.

References

1 Abbayya K, Puthanakar NY, Naduwinmani S, Chidambar YS. Association between Periodontitis and Alzheimer's Disease. N Am J Med Sci. 2015 Jun;7(6):241-6.

2 Gonzalez A, Hyde E, Sangwan N, Gilbert JA, Viirre E, Knight R. Migraines Are Correlated with Higher Levels of Nitrate-, Nitrite-, and Nitric Oxide-Reducing Oral Microbes in the American Gut Project Cohort. mSystems. 2016 Oct 18;1(5):e00105-16

3. Sun KT, Shen TC, Chen SC, Chang CL, Li CH, Li X, Palanisamy K, Hsia NY, Chang WS, Tsai CW, Bau DT, Li CY. Periodontitis and the subsequent risk of glaucoma: results from the real-world practice. Sci Rep. 2020 Oct 16;10(1):17568.

4. Pasquale LR, Hyman L, Wiggs JL, Rosner BA, Joshipura K, McEvoy M, McPherson ZE, Danias J, Kang JH. Prospective Study of Oral Health and Risk of Primary Open-Angle Glaucoma in Men: Data from the Health Professionals Follow-up Study. Ophthalmology. 2016 Nov;123(11):2318-2327.