What is a dislocated lens?
A dislocated lens, also known as ectopia lentis, occurs when the eye’s natural lens is displaced from the center of the eye where it is normally located behind the pupil. Because the lens helps the eye focus on objects at different distances, it is a significant component of your vision.
The lens is referred to as luxated if it is located outside the lens space. It can be dislocated to one of four areas:
Sitting outside the hyaloid fossa, the depression in the front of the vitreous body (the clear, gel-like substance that fills the space in the middle of the eye)
Floating in the vitreous body
Sitting in the anterior chamber (the space between the lens and the cornea)
Sitting on the retina
If the lens is still somewhat in the lens space, it is referred to as subluxated, or a lens subluxation.
Ectopia lentis can cause a variety of complications within the eye, such as: blurred vision, double vision, glaucoma, retinal damage and blindness. It is a rare condition, affecting less than 10 out of every 100,000 people worldwide.
Causes and risk factors
Causes of lens dislocation include trauma and genetic mutations. Additionally, people with certain ocular and systemic disorders can be at greater risk of developing ectopia lentis.
Trauma
Trauma is the most common cause of lens dislocation. Those that play sports are at higher risk of dislocating their lens. This is due to actions such as being struck in the eye by a baseball or hockey stick. Other types of trauma include falls and car accidents.
Ocular diseases
Simple ectopia lentis and ectopia lentis et pupillae are two ocular conditions that involve lens dislocation but vary in a few ways.
Simple ectopia lentis – Lens dislocation that is hereditary and occurs in both eyes, usually in the superotemporal (the upper and outer) regions of the eye. It can be congenital or appear spontaneously later in life. Mutations occur with the ADAMTSL4 and FBN1 genes.
Ocular disorders
People with the following ocular disorders are also at risk for lens dislocation:
Aniridia – A congenital or acquired disease where there is a partial or complete absence of the iris.
Retinitis pigmentosa – A group of inherited rare diseases where the photoreceptor cells in the retina slowly degenerate. Blindness can occur as a result.
Congenital glaucoma – A condition that occurs at birth and is due to abnormally high pressure within the eye. This can damage the optic nerve and lead to vision loss.
Axenfeld-Rieger syndrome – A group of rare congenital genetic disorders that affects the development of the front of the eye. It can lead to glaucoma.
Pseudoexfoliation syndrome – A condition that causes flakes of fiber to deposit in the body, particularly in the front of the eye. This may cause eye pressure to rise and lead to glaucoma and vision loss.
Ocular syphilis – A condition that occurs when syphilis, a sexually transmitted disease, goes untreated. This can lead to vision loss.
Megalocornea – A rare condition where the diameter of the cornea is bigger than normal. It presents in both eyes.
Hypermature cataract – A cataract that has gone untreated and has become whitish and dense, making it difficult to remove.
High myopia – Severe nearsightedness, typically -6.00 diopters or greater.
Buphthalmos – An enlarged eyeball, usually caused by increased pressure within the eye and present at birth.
Intraocular tumor – An abnormal mass in the eye.
Systemic disorders
Numerous systemic disorders (affecting the entire body) can predispose a person to lens dislocation, which is most commonly associated with Marfan syndrome, Weill Marchesani syndrome and homocystinuria.
Marfan syndrome is the most common systemic disorder associated with ectopia lentis. It is an inherited condition that causes abnormal development of the connective tissue in the body. This includes the tissue that keeps the lens of the eye in place. Ectopia lentis occurs in about 75% of patients with Marfan syndrome.
Weill Marchesani syndrome is an inherited connective tissue disorder that can cause abnormalities of the lens and secondary glaucoma. These abnormalities are usually found in childhood. Those with Weill Marchesani syndrome may also have joint stiffness, cardiovascular defects, bone defects and intellectual disabilities, among other issues.
Another common cause of inherited ectopia lentis is homocystinuria (HCU). HCU is a disorder caused by a lack of the enzyme that is needed to metabolize homocysteine, an amino acid produced in the body. It causes lens dislocation in 90% of patients. HCU can also cause osteoporosis, behavior disorders, intellectual disabilities, high blood pressure and stroke.
Other systemic disorders associated with ectopia lentis include:
Ehlers Danlos syndrome – A disorder that affects the connective tissue in nearly every organ system of the body. It is a genetic disorder relating to collagen formation and how it functions.
Sturge-Weber syndrome – A rare disorder that affects the blood vessels and is present at birth. It can cause high eye pressure, leading to buphthalmos.
Sulfite oxidase deficiency – A nervous system disorder that appears shortly after birth. It causes facial feature abnormalities, including the eyes. Many babies do not survive past a few months, but those that do develop ectopia lentis.
Mandibulofacial dysostosis – A genetic condition which affects the structure of the face and neck. This leads to possible eye complications. Also referred to as Treacher-Collins syndrome.
Wildervanck syndrome – A condition that affects the bones in the eyes, ears and neck. Lens subluxation is a possible symptom.
Conradi syndrome – A rare genetic disorder that causes skeletal abnormalities, eye issues, vision issues and other symptoms. Also known as Conradi Hünermann syndrome.
Crouzon syndrome – A genetic disorder where the seams of the skull do not fuse in a normal fashion. This can cause shallow eye sockets, leading to bulging eyes and eye exposure issues.
