Reasons For Long Term Light Sensitivity After Cataract Surgery
One amazing thing about cataract surgery is just how well the vision improves afterwards. And it’s not only just being able to see clearer (and often without needing any prescription). Cataract surgery also improves the ability to see colors and light. But what if the light is toooo much.
Some individuals after cataract surgery can notice an increase in sensitivity of light. There are a few short-term reasons for this, such as having a perfectly clear lens after cataract surgery. But there are also more long-term causes of light sensitivity such as extra inflammation and perhaps the biggest cause being extra sensitivity on the cornea or dry eye.
Let’s see just how cataract surgery plays a role in causing extra light sensitivity and just how it can be managed and treated.
Immediate Light Sensitivity
A cataract is a cloudy lens. This cloudiness does a few things. It of course blurs vision. If light can’t pass through very well and scatters, things appear blurry.
But if light doesn’t pass through, it also makes things darker. Kinda like a built-in pair of sunglasses.
So what happens when we remove this cloudy lens and replace it with a clear lens? More light enters the eye. This of course, makes vision sharper and more vibrant. But it does mean everything is brighter.
If you sit in a dark room for a while and suddenly go outside, you will be sensitive to light. Until you adapt to that light. Our eyes and brain are capable of adjusting to the environment we are in. The same principal applies if you wear sunglasses inside to help treat sensitivity to light - wearing sunglasses will actually make you MORE sensitive to light since the eyes and brain adjust to the lower levels of light.
So, before cataract surgery, our brain adjusts to the vision it gets from the cataract. Because less light makes its way to the back of the eye, our brain adjusts to the lower levels of light. After cataract surgery, when the brain doesn’t need to be extra sensitive to light, it must re-adjust to the higher levels of light. This can add a little bit of sensitivity to light in the short term.
Not everyone is going to have this same sensitivity to light. Different thresholds or amounts of light will affect people differently. And this can even change by the season.
Beyond Short-Term: Extra Inflammation
But there is another, more abnormal cause of an increase in light sensitivity after cataract surgery: extra inflammation.
It turns out that the cataract proteins are “foreign” to our own immune system. As a result, the immune system MUST respond aggressively to clear those cataract proteins.
Fortunately, because the cataract is removed during cataract surgery, there aren’t many of these proteins left over for the immune system to attack. But everyone after cataract surgery will have a small degree of inflammation that is readily treated with steroid eye drops.
For some, however, the usual course of steroids doesn’t completely eliminate all of this inflammation and it can build up again a short while after cataract surgery.
When there is inflammation in the eye. Our iris (the colored part of the eye) becomes more inflamed. When light shines in our eyes, this iris contracts to make our pupil smaller. But if the iris is inflamed, this contraction becomes painful. Thus, inflammation inside the eye causes light to be uncomfortable and painful.
While typically this extra inflammation may only be a short term issue, about 1 in 400 may experience a much longer course of this inflammation. This will in turn cause long term light sensitivity.
To treat extra inflammation, steroid eye drops are added to the eye again to calm it back down.
Also to help with the extra sensitivity to light, paradoxically certain dilating drops can actually be used. Yes, dilating the eye will allow more light into the eye, but what these drops will do is prevent the iris muscle from constricting. Because movement of this inflamed muscle is causing the bulk of the light sensitivity, preventing it from moving can considerably improve the sensitivity to light.
The More Common Cause
Extra inflammation inside the eye is a very well known and understood cause of increased sensitivity to light after cataract surgery. But it turns out, it isn’t the most common reason to have long term light sensitivity after cataract surgery.
The most common cause is actually increased sensitivity of the cornea, typically because of dry eye.
The cornea (the front clear part of our eye), is the most sensitive structure in the body. Ever get a scratch on your eye? The terrible pain you had was because of the cornea. While this seems like a disadvantage, having a very sensitive cornea most likely helps insure that nothing intentionally messes with it and that it stays perfectly clear for good vision.
There are many nerves that run through the cornea. It turns out that many of these nerves that carry pain signals from our cornea meet up at a spot in our brain that also gets triggered by light. Thus, light can further trigger or amplify pain from the cornea! This results in sensitivity to light.
In fact, the light sensitivity with a migraine or after a brain injury even share this same pathway!
More sensitive cornea after cataract surgery
You may have a small scratch on the eye immediately after cataract surgery, but this isn’t the real reason for long-term sensitivity since this scratch goes away quickly within the first twenty-four hours.
What instead happens is that dry eye and thus sensitivity can increase within the first month out after cataract surgery.
- The surgery itself irritates the cornea; the cornea can dry out more during surgery and stuff such as betadine to sterilize the eye also happen to be toxic to the cornea.
- But the bigger reason (long-term wise) is that prescription eye drops can actually irritate the eyes.
Within prescription eye drops are preservatives. These preservatives are to prevent the growth of bacteria in the eye drop bottles. Of course, that’s a good thing. But the downside is that these preservatives also will be slightly toxic to us as well. Not enough to not use the drops - the drops still do have a huge benefit (see above on treating inflammation in case you forgot).
So between the drops and the surgery itself, many people can notice an increase in dry eye after cataract surgery. This is especially the case if you go into cataract surgery with pre-existing dry eye. In fact, you may even have dry eye without even realizing it. Have “tired eyes” or watery eyes? These are actually signs of dry eye.
So about 10-15% of everyone going through cataract surgery can notice more dry eye symptoms from a month out up to about three months out after cataract surgery.
When the eye dries out, there is extra inflammation on the surface of the eye. This inflammation can aggravate the nerves within the cornea and make them more sensitive. Because light triggers the pathway of these inflamed and irritated nerves, sensitivity to light ensues.
Treatment of a sensitive cornea
So what can be done about this long term light sensitivity? Well, the goal is to calm down those nerves so that they go back to normal.
The initial goal is to reduce inflammation on the surface of the eye. This will prevent the nerves from continuing to become aggravated. And there are a whole host of things designed to reduce inflammation on the surface of the eye - pretty much anything designed to treat dry eye.
The most simple treatment involves aggressive lubrication of the eyes with preservative free artificial tears. These tears help prevent the eye from drying out. This prevents the build-up of more inflammation as well as can help to some extent to wash away some of the already built up inflammation on the eye.
Beyond artificial tears,
- Starting warm compresses or omega 3 supplements can help for many. This helps improve the flow of oils from our eyelids that protect our eye from drying out
- Great prescription eye drops exist to target that inflammation and allow us to produce more tears
- Small plugs can be placed in the corner of the eyelids to prevent tears from draining off the surface of the eye
Finally, for chronically inflamed corneal nerves, medications used to treat nerve pain, such as gapapentin are being used with success.
Of course, the best treatment is prevention. And after cataract, surgery, using artificial tears aggressively can prevent the build-up of dry eye and light sensitivity. But if it's already developed, check with your eye doctor to see what can be done for you to help get it to resolve.
Many people will have an immediate sensitivity to light after cataract surgery. Removing the cataract removes the built-in “light filter”. But longer out after cataract surgery there are two main causes: a return of inflammation inside the eye or an increase in dry eye or sensitivity on the outside of the eye. With treatment, however, both conditions can be improved.
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