From the Guidelines
Bloodshot eyes are primarily caused by conjunctivitis, dry eye syndrome, and other inflammatory conditions, as well as irritants such as smoke, dust, and chlorine, according to the most recent evidence from 2024 1. The primary causes of bloodshot eyes can be classified into several categories, including:
- Infectious conjunctivitis, which can be caused by viruses or bacteria 1
- Noninfectious conjunctivitis, which can be caused by allergies, mechanical irritation, or toxic substances 1
- Dry eye syndrome, which occurs when tear production is insufficient 1
- Contact lens-related keratoconjunctivitis, which can cause conjunctival injection, corneal neovascularization, and superficial punctate keratopathy 1
- Giant papillary conjunctivitis (GPC), which is characterized by papillary hypertrophy of the superior tarsal conjunctiva and mucoid discharge 1 Other causes of bloodshot eyes include:
- Rosacea conjunctivitis, which is associated with bilateral chronic blepharitis, eyelid margin telangiectasias, and meibomian gland inspissation 1
- Mechanical or irritative conjunctivitis, which can be caused by exposure to wind, dust, or chemicals 1
- Allergic conjunctivitis, which can be caused by allergies to pollen, pet dander, or dust mites 1 It is essential to differentiate between primary conjunctival disease and conditions in which conjunctival inflammation is secondary to systemic or ocular diseases, as treatment should be directed at correcting the underlying problems 1.
From the Research
Primary Causes of Blood Shot Eyes
The primary causes of blood shot eyes can be attributed to various factors, including:
- Allergic conjunctivitis, which is an allergen-induced immune response secondary to the binding of immunoglobulin-E (IgE) to sensitized mast cells 2
- Dry eye syndrome, which may be associated with some systemic diseases and can cause redness, itchiness, and dryness in the eyes 3, 4
- Ocular allergies, which can lead to symptoms such as itching, tearing, chemosis, and hyperemia, resulting in blood shot eyes 5, 2, 6
Underlying Factors
Some underlying factors that may contribute to blood shot eyes include:
- Activation and degranulation of mast cells, leading to increased tear levels of histamine, tryptase, leukotrienes, cytokines, and prostaglandins 2
- Co-morbidities such as allergic rhinitis, which can increase the risk of developing ocular allergies and blood shot eyes 6
- Systemic diseases, which may be associated with dry eye syndrome and ocular allergies 3, 4
Overlap of Symptoms
It is essential to note that symptoms of allergic conjunctivitis and dry eye syndrome can overlap, making diagnosis and management challenging 4, 6. A comprehensive understanding of the patient's history, ophthalmologic examination techniques, and diagnostic procedures is crucial for accurate diagnosis and effective management of blood shot eyes 6