Lens dislocation is a condition in which the lens moves out of its rightful place. It occurs when some or all the supporting ligaments detach from the lens.
The lens is a transparent structure that lies at the centre of the eye. It focuses light coming from the outside to the retina. When the ligaments supporting it break off, the lens may fall back into the vitreous space (posterior lens luxation) or may push the iris and enter the anterior chamber (anterior lens luxation). In some instances, the lens is displaced but still remains within its space (lens subluxation).
The displacement of the lens is responsible for visual impairments in those affected. In partial dislocation, the retina sends fractions of light to the brain. In complete dislocation, no light is sent at all. Although not a common condition, lens dislocation can bring about several complications.
Also Known As
Causes and Risk Factors
Lens dislocation can occur due to either of the following:
- Trauma – It is the most common cause of dislocation. Trauma can occur after being hit by a blunt object directly on the eye or on the head. The ligaments may weaken or be broken off and detach as a result.
- Ocular diseases – The diseases can occur spontaneously or may be present from birth. They include simple ectopia lentis, syphilis congenital glaucoma, ectopia lentis et pupillae and among others. These ocular diseases are in most cases hereditary.
- Systemic diseases – They include Marfan syndrome, homocystinuria and Weill Marchesani syndrome.
Signs & Symptoms
The signs and symptoms may include:
- Blurred vision - Problems with visual acuity are most common in complete dislocation rather than in partial dislocation.
- Nearsightedness (myopia)
- Painful red eyes
- Trembling iris (iridodonesis) or lens (lentodonesis)
The diagnosis assesses lens that appears off the center. It may also determine specific underlying causes. Tests can include:
- History exam – The eye professional may inquire about previous injuries, visual disturbances or eye abnormalities in the patient/family.
- Dilated eye exam – Involves placing an eye drop to dilate the pupil. This allows for a proper view of the inside of the eye.
- Slit lamp exam – A microscope is used to magnify the structure of the dilated eye. The test may show trembling of the lens or iris during eye movement, an indication of dislocation.
- Corneal diameter measurement – The size of the cornea, if huge can indicate Marfan's syndrome which is associated with megalocornea.
- Tonometry – The test measures the intraocular pressure (IOP). Levels above 21 mmHg for those diagnosed with ectopia lentis could indicate glaucoma as a complication.
Treatment focuses on refractive correction as well as management of underlying diseases.
It depends on the underlying cause and the extent of damage. However, no drugs are usually given. The eye doctor may just monitor the condition. In some cases, glasses can be prescribed to correct blurry vision.
Surgical therapy may be carried out when there are complications involved. The procedures can include:
- Lensectomy – Done to remove lens which is then replaced
- Vitrectomy – Involves removal of vitreous gel
- Laser surgery – This may be carried out where glaucoma is an associated complication
Ectopia lentis is associated with various complications. They include:
- Retinal detachment – Dislocation of the lens can result in detachment of the retina. This is when the retina (light sensitive tissue at the back of the eye) is pulled away from its position. Permanent loss of vision is common in this case.
- Uveitis – This is the inflammation of the middle part of the eye known as the uvea.
- Pupillary block glaucoma – Forward displacement of the lens can cause pupillary block which may in turn narrow the drainage angle. Due to the slow draining of the eye fluid, pressure builds up and glaucoma can occur.
- Blindness – Eventually, if not treated, lens dislocation can on its own or due to underlying conditions cause blindness.
Individuals should wear protective eye wear when in a potentially hazardous environment to avoid traumatic ectopia lentis. It is also recommended that underlying conditions be well treated to lessen the risk of dislocation of lens.