What it is
In short: the lens inside your eye, or a lens implant from cataract surgery, can move out of place. This can blur your sight or cause double vision in one eye. Some cases only need regular checks. Others need surgery to reposition, replace or remove the lens.
The natural lens sits behind the coloured part of your eye (the iris) and focuses light. It sits in a thin, clear bag called the capsule, held in place by fine fibres. If these fibres weaken or break, the lens can shift. A lens that has shifted partly out of place is called subluxed. A lens that has moved out of its normal position is called dislocated.
This can happen to your natural lens, or to an artificial lens (intraocular lens, or IOL) put in during cataract surgery. An implant can move soon after surgery or many years later. How well it stays in place depends on the implant and on the supporting tissue left in the eye.
Causes include:
- an eye injury
- conditions that weaken the supporting fibres
For a natural lens, these conditions include inherited conditions that affect the body's connective tissue, such as Marfan syndrome. For a lens implant, previous surgery, inflammation and a condition called pseudoexfoliation can weaken the support. The cause, and which way the lens has moved, affect the tests and treatment you need.
Symptoms
A lens that has moved can cause:
- blurred sight
- a change in focus that glasses do not fully correct
- seeing the edge of the implant
- two images when you look through one eye
A small shift may cause few symptoms. A larger one can affect your vision a lot.
Double vision has several possible causes. Dr Chin may ask whether it stays when you cover each eye in turn. This helps tell a problem inside one eye from a problem with how the two eyes line up. It does not show that the lens has moved, so you still need an examination.
When it is urgent
Get your eye checked urgently if you have:
- sudden loss of vision
- new double vision
- a lot of eye pain or redness
- an injury that has changed your sight, because the damage may go beyond the lens
Do not press or rub the eye to try to move the lens back.
Call the clinic at +65 6694 0400. Outside clinic hours, call the 24-hour answering service at +65 6535 8833, or go to a hospital A&E with eye services. Double vision after a head injury, or with a severe headache, needs emergency care.
What the assessment involves
Dr Chin will check your vision, focus and eye pressure, then examine the lens and its supports with a slit lamp, a microscope used for eye examinations. Drops to widen your pupils can show how far the lens has moved, and let Dr Chin check the retina. The drops take 20 to 30 minutes to work and blur your sight for a few hours, so arrange for someone to drive you home.
Your history matters. If you have records from a previous operation, or details of your lens implant, please bring them. Dr Chin will ask about any injury, other eye conditions and, where relevant, your family and general health. If a natural lens has moved without an obvious injury, you may need tests for an underlying condition.
The retina is checked for related problems. If the view is blocked, an ultrasound scan can help find the lens and check the back of the eye. After an injury, tests are chosen with any other injuries in mind. There is no single operation that suits every position or type of lens.
Treatment options
Regular checks
If the lens has moved only a little, your sight is good enough and there are no complications, regular checks or new glasses may be enough. The checks look for any change in the lens position or its effects. Treatment becomes more likely if the lens causes pain, raises the eye pressure, inflames the eye, touches the clear front window of the eye (the cornea), or blurs your sight.
A dislocated natural lens
Surgery may involve removing the lens. How your eye focuses afterwards depends on the support left and the condition of the eye. Options include a lens implant held in a different position, or glasses or a contact lens. These options have different practical demands and risks.
A dislocated lens implant
The implant may be moved back and fixed in place, or removed and replaced with a new one. The choice depends on the implant's design and condition, the capsule and the rest of the eye. A vitrectomy (removing the vitreous gel) may be needed, so that the lens can be handled without pulling on the retina. Cataract and retinal surgery techniques may be combined where needed.
Risks
Risks include:
- infection
- bleeding
- inflammation
- changes in eye pressure
- retinal detachment
- the lens moving again
Ask what the proposed operation is meant to fix, and whether you might need more treatment later.
Recovery and follow-up
Follow-up visits check the lens position, eye pressure and healing, and any related retinal problem. Use your prescribed drops, and follow the advice about protecting your eye and returning to activities. You may need new glasses once the eye has settled.
Recovery depends on whether the operation involved only the lens, or the vitreous and retina too. Arrange for someone to take you home after surgery. If a gas bubble is used as part of retinal treatment, you will be given instructions on head positioning and travel. Report worsening pain or vision promptly, even if you already have a follow-up appointment booked.