Marfan Syndrome and the Eye
In Marfan Syndrome an important protein called Fibrillin is abnormal.
This protein is important for its weight-bearing and elastic properties. It is common in the eye, so people with Marfan Syndrome commonly have issues with their eyes.
Normal structure of the Eye
The lens in the eye works to focus light on the retina, which changes light into an electrical signal, which passes back along the nerve to the brain and then turned back in to images. This is a lot like a digital camera, (in fact the eye is also called the camera) where light is focused by a lens on a sensor, which turns light into electricity and the signal sent by wire to your computer (the brain), which turns it back into pictures.
Structure of the eye Marfan Syndrome
In Marfan Syndrome, because of weak fibrillin there are poor connections and certain eye conditions may occur, these include most commonly: Dislocated lens, short-sight (myopia), retinal detachment, squint and glaucoma.
We will now discuss these eye conditions further:-
Dislocated lens is the most common eye problem that Marfan patients experience and occurs in between 50% and 80% of such patients over their lifetime.1
The lens normally sits behind the iris (coloured part of the eye) and is clear, so all light going through the pupil is focused on the retina. In Marfan Syndrome it often moves up and we say it is decentred or subluxed. Patients may experience blurred vision at this stage, because they are looking through the edge of the lens and not the middle. The lens moves because the zonules or little threads holding it in place break easily, it is though that the sun shining down on the lower zonules weakens them more that the upper ones, which are shaded by the iris. The lens may move completely and fall into the back of the eye and rest on the retina.
If the dislocated lens is causing difficulties, the patient may request to have it removed and have an artificial lens as a replacement. The replacement lens may be stitched into the area behind the iris, clipped on to the front of the iris or just rest in front of the iris. There are pros and cons for each type of lens, so the individual surgeon decides this with each patient.
Myopia or short sight is present in 34% to 44% of Marfan Syndrome patients. This is way above the 4.8% average.1 So quite often patients will need to wear glasses to see distant objects clearly. It happens because the eyes become longer and the focus point is now in the middle of the eye not on the retina.
Retinal detachment occurs in 5 to 10 % of Marfan Syndrome patients, but this goes up to 8 to 38%, if the lens is dislocated or 69% if the other eye had a retinal detachment already.1 This is a potentially blinding condition and needs urgent assessment and prompt treatment.
Patients may experience flashing lights, increased objects floating in their vision, fogging of vision or loss of an area of vision.
It often occurs because the vitreous (gel in front of retina) pull firmly on one part of the retina and tears a hole, then fluid gets in through that hole and strips the retina from the underlying layer like wallpaper off a wall. When retina is detached, it is separated from its nutrient supply and starts to die, so reattaching it is a priority. Also the goal is to prevent the macula from detaching, this is the retina responsible for centre of your vision.
There are several ways to perform retinal detachment surgery, but they usually involve simple principles. Drain the fluid from between the layers to allow it to reattach, use a gas or silicone oil to press the layers together from the inside of the eye, sew a “buckle” onto the outside of the eye to flatten the layers from the outside, seal the tear using laser or freezing therapy and remove the vitreous to stop it pulling on the retina. There are pros and cons for each step, so the individual surgeon decides this with each patient.
A small retinal break may only need laser.
Squint, also known as strabismus, a cast in the eye or a turn in the eye, is quite common in children with Marfan Syndrome (19 to 45%).1 It may be due to poor support for the muscles or reflect a need for glasses.
If it isn’t treated in children younger than 8.5 years, the brain often neglects the squinting eye and the visual development of that eye doesn’t occur. We call that amblyopia or a lazy eye. It’s actually the brain that doesn’t develop its ability to refine the images being send to it. Treatment is usually with glasses or patching of the non-squinting eye. Surgery to straighten the eyes may be necessary in some patients.
Glaucoma is a problem where pressure within the eye damages the nerve and can cause loss of vision if not treated. It occurs in 35% of Marfan patients.1 Treatment is usually with drops but some patients require surgery, to relieve the pressure.
For further reading see review article in publications, it is freely available online and covers in more detail what we have discussed today: Nahum Y, Spierer A. Ocular features of Marfan syndrome: diagnosis and management. Isr Med Assoc J 2008;10(3):179-81.
1. Nahum Y, Spierer A. Ocular features of Marfan syndrome: diagnosis and management. Isr Med Assoc J 2008;10(3):179-81.
Explanation provided with thanks by Dr Ian Dooley, Specialist Registrar in Ophthalmology, Royal Eye and Ear Hospital, Dublin.