Blue sclerae is a condition in which the whites of the eyes, otherwise known as the sclera, appear bluish in colour. This condition is often a result of the thinning out of collagen fibres in the sclera, leading to a more transparent sclera wherein the underlying blood vessels become visible. Blue sclera often occurs in the setting of connective tissue diseases; however, the condition can also result as a side effect of certain medications or from other systemic diseases unrelated to connective tissue diseases. Blue sclera can also occur just because an individual was born with a sclera that is thinner than it should be.
The eye is made up of three layers:
- The outer fibrous layer: It consists of the sclera and cornea. The sclera is what makes up the whites of our eyes.
- The middle vascular layer: This layer is otherwise known as the uvea. The uvea is made of the iris, the coloured part of our eyes, the ciliary body, and the choroid (which is composed of blood vessels and many supporting cells).
- The inner neural layer. It is composed of the retina. The retina is responsible for sensing light and relaying the light signal to our brain so that we can interpret what we see.
In certain cases, the sclera may thin out allowing the vascular layer underneath to be visible. Blue sclera is associated with many conditions, especially connective tissue disorders where the collagen fibres are weak to begin with. Most connective tissue disorders are inherited, and the manifestations are apparent even in childhood. Some connective tissue disorders that can result in blue sclera include: Marfan syndrome, Ehlers Danlos syndrome, Epidermolysis bullosa, and Osteogenesis imperfecta. Blue sclera is a key finding in children with Osteogenesis imperfecta, otherwise known as brittle bone disease.
Non connective tissue disease causes
In adults, systemic medications may cause pigmentation changes in several areas of the body, including the eyes. These medications include the antiarrhythmic medication amiodarone, antipsychotics such as phenothiazines, minocycline antibiotics, and even long-term corticosteroid use. Topical eye medications containing epinephrine may also induce pigment changes in the sclera. It is important to note that medication induced blue sclera occurs as a result of long-term use. Excessive exposure to soluble silver compounds, which often happens in the setting of industrial exposure or medication containing silver salts, can lead to a permanent bluish-blackish discoloration of the skin and eyes, called argyria and argyrosis respectively. Rarely, blue sclera can be a symptom of severe iron deficiency.
The primary presentation of blue sclera is a bluish hue in the whites of the eye. Other symptoms may accompany the underlying cause. For example, in the case of Osteogenesis imperfecta, children will also have multiple fractures and early hearing loss
Most cases of blue sclera are harmless, and treatment only involves identifying and eradicating the underlying cause (in cases where it can be eradicated). Supportive treatment may sometimes be offered to ensure that the condition does not deteriorate.