What every pharmacist should know about post-LASIK dry eye

By Jay Shelvin posted 11-06-2019 11:18 PM

  

It’s the Wild West when it comes to treating dry eyes after LASIK. Overblown metaphor? I’m not so sure. I’m a LASIK surgeon who answers patients’ questions (yes, some of us talk to them!) about post-LASIK dry eye on a daily basis. Those conversations always feel like I’m trying to create some order in an unknown and lawless land. There’s rarely a concern or confusion about the steroid or antibiotic prescriptions. It’s always the treatments for dryness that feel as vague and shadowy as an old-fashioned, swinging-doors saloon. There’s a constant sense of “are there rules here? Is there some routine everyone knows but me? What’s inside this bottle?”

Our goal here is to try and bring some law and order to an untamed land to avoid the LASIK myths amplification. The frontiers of post-LASIK dry eye were discovered, named, and tamed a long time ago. For some reason — and I genuinely don’t know why — the news never made it to the rest of the population. So nearly every new LASIK patient enters into the inevitable state of post-LASIK dry eye with wildly different ideas about its cause, its nature, and its treatment. The laws governing these issues exist. They’ve already been set. Just like every other kind of law, however, it won’t accomplish anything if no one knows about it.

What causes post-LASIK dry eyes?

Theories about the etiology of this issue were all over the place for a long time. I remember attending a lecture at a conference detailing how the suction ring damages conjunctival goblet cells and causes dryness. Then an hour later at the same conference, I learned the excimer causes dryness as a result of both direct and reflected UV light on the surface of the eye. It was a confusing time for all of us.

At this point, we know the cause. That’s a big deal because it gives us a basis for treatment, a timeline for expected recovery, and even ways to speed the process. It’s the (temporary) impact on corneal nerves.

Normal baseline tear production depends on an afferent loop from corneal nerves that are terminal branches of the long posterior ciliary nerves. With LASIK, a percentage of those nerves are severed. That causes decreased baseline tear production. It’s almost always temporary because those nerve re-anneal over the next few months. As they do, tear production returns to normal.

Why is post-LASIK dry eyes hard to treat?

It’s not because there aren’t great treatments. It’s because the presentation of dry eyes after LASIK usually looks much different than a classic case of dry eyes. The symptoms of burning, scratchiness, and foreign body sensation typify “normal” dry eye syndrome. All of these, you’ll notice, have a common feature in that they feel bad. They feel the dryness. That’s because their sensory corneal nerves are fully intact and telling them, “it’s terrible up here! Get some tears!”

After LASIK, the reason patients have dryness is the same reason they can’t feel it the same way that non-LASIK patients do. The sensory nerves are the cause of the dryness, and the reason it doesn’t present like typical dryness. Patients will suffer from fluctuating visual clarity, night vision difficulty, and an overall “fuzzy” quality of vision. Most of them will see the results of dryness long before they will feel the dryness. This leads to difficulty convincing patients to use the medicines that would be the most helpful.

This is especially true when the dryness gets bad enough for reflex tearing to take over. Baseline tear production comes from small glands of Wolfring and Krause underneath the eyelids. Reflex tearing comes from the relatively giant lacrimal gland located above the eyeball. It exists to flood the eye when needed. Normal, walking-around, adequately lubricated eyes is the domain of baseline tear production. Watery, crying eyes because of an environmental allergen or a piece of dirt in the eye is the domain of reflex tearing.

When baseline tearing is impaired, reflex tearing will often take over to do slipshod job of trying to lubricate the eye. So I’ll often hear patients say, “My eyes aren’t dry. In fact, I have the opposite problem of tearing too much.” But that is precisely how we know their eye is very dry! Reflex tearing was never meant to handle normal lubrication of the eye’s surface. The only way to fix the problem is to convince patients to use treatments for decreased baseline tear production. And us LASIK surgeons can use all the help we can get in spreading the message that tearing is a symptom of that dryness, not a solution for it.

In summary, it’s hard to treat a condition that feels like a mystery. And dryness after LASIK feels (or looks) mysterious for most patients. The first and most important step is helping people understand the cause of their problems. After that, helping fix the issue becomes much more straightforward.

Frontline treatment for post-LASIK dryness

I’m always a little self-conscious when telling people to use artificial tears. It feels like such a homespun, uneducated solution to their problem. That feeling is amplified by the fact that most patients are only half-convinced that dryness is the cause of their problem. I can’t count how many times someone has stared at me incredulously when I tell them that the solution to their eyes watering is to use more artificial tears.

And yet, here we are. The best solution for the majority of the symptoms caused by post-LASIK dryness is artificial tears. Specifically, preservative-free artificial tears. I’ve found that for the first two months after LASIK, it’s better to avoid tears with preservatives in them. It’s easy to describe which tears are the right ones for patients. I tell them they’ll know if they are preservative-free if they come in those highly inconvenient, single-use vials. There are a couple companies who (through wizardry beyond my understanding) have regular screw top bottles labeled as preservative-free. Those don’t count. There’s trickery afoot with those bottles. Single-use vials are the only acceptable option.

I give the same starting instruction to every LASIK patient. Use one drop of preservative-free tears in each eye every two hours for the first two months after surgery. Why so often? It’s because we’re trying to stay ahead of the problem instead of playing catch up. My comparison for them is thirst. By the time you’re thirsty, you’re already dehydrated. Similarly, by the time you are seeing the symptoms of dryness (fuzzy vision fluctuations), you’re already dry.

This is necessary throughout the whole day because normal baseline tear production suffers (with our without LASIK) at the beginning and end of the day. It’s for two different reasons. The natural circadian rhythm for tear production hits its nadir early in the morning when first waking up. As the day wears on, there’s a cumulative evaporative loss. By the end of the day, the tear film is trying to keep up with the evaporative loss accumulated throughout the day. That’s why patients will say their vision is the worst early in the morning or late at night, or both. Using a drop of preservative-free tears every two hours mitigates these problems dramatically.

Pharmacologic treatments

Restasis (cyclosporine) Restasis after LASIK is amazing. I used to require it for the first two months after LASIK. It caused so much stress for people who couldn’t afford it that now I only recommend it. But it is always recommended. It is able to do something that preservative-free tears cannot do. Namely, it increases the speed of healing for the corneal nerves. It resolves the dryness significantly faster than waiting on the normal healing time.

I spent countless hours involved in a study on Restasis during my fellowship. We used an esthesiometer made specifically for the cornea. It looked like a piece of fishing line that could be lengthened in specific increments. The longer the line, the more sensitive the cornea would need to be to feel it touch its surface. We found that Restasis brought the return of normal corneal sensation much faster than the control group. After hours of sitting in a dark room, gently poking people in the eyeball with fishing line, I’m glad it finally pays off by sharing this with you. If people wonder why they’re taking Restasis after LASIK, the answer is that it pushes a fast-forward button on their healing process. Clinically, I’ve had similar results with Xiidra.

Muro (hypertonic saline) This deserves mention in the hopes that I can steer more people away from its use. There are cases where Muro solution or ointment is very helpful (e.g. Fuchs’ dystrophy, recurrent corneal erosions). But post-LASIK is rarely one of those cases.

The post-LASIK I’ve seen where Muro was recommended haven’t had a logical reason why. It’s not that it seems to cause damage. That’s not the reason for mentioning it here. It’s because any treatments we recommend that aren’t necessary have a chance to crowd out a treatment that will help. When patients are taking medications that aren’t producing results, it can make it much harder to convince them to use medications that will actually help.

Steroids Every patient needs steroid drops for the first week after LASIK. As I tell patients, “No matter how quick and elegant the surgery is, your eye still thinks it’s an injury.” Injuries cause inflammation, and we need steroids the first week to act as the powerful anti-inflammatory regulator of that inflammation.

Rarely, we need to use them again in a lesser dose and over a longer tapering period. This is because dryness, on a biochemical level looks exactly like inflammation. For the vast majority of cases, we can treat the dryness by making sure the eye stays lubricated during the healing phase.

I view it as a spectrum of inflammation. On the mild side of the spectrum, the symptoms and pathology looks like normal post-LASIK dryness. On the other end of the spectrum, it is a full-fledged inflammatory condition. If the dryness continues or gets worse with time, the eye’s surface starts tilting more towards the inflammatory side of the spectrum.

The reason this is problematic (beyond the obvious) is that inflammation will lead to more dryness — which will lead to more inflammation. The meibomian oils on the surface of the eye get broken down into soaps (saponification) and the spiral of inflammation continues downward. The solution, in this case, is to stop focusing on lubrication and start focusing on inflammation.

Thankfully, it’s uncommon to get to this point. But when necessary, a drop schedule with a steroid taper can help with a dramatic turnaround. That’s why we leave this “big gun” therapy on the shelf except for cases where we really need it.

Other treatments

Omega-3 Oils These are a game-changer. We know baseline tear production will be reduced in the first few months after LASIK. We can add to the aqueous (water) layer of the tear film with preservative-free tears. There is, however, a “topcoat” layer to the tear film that is largely untreated with artificial tears. The lipid layer.

Each eyelid has about 30-40 meibomian glands lining the eyelid margin. They sit just posterior to the lash line. From these openings, meibomian oil spills out and is wicked onto the front of the eye. Once there, it floats on the surface of the tear film. Its job is to reduce the evaporative loss of the aqueous layer.

The incidence of meibomian gland dysfunction is just over 50% in the general population. That’s okay for the majority of people because it doesn’t reach a level that will cause dry eye symptoms. The baseline tear production level is robust. A little decrease in the lipid layer compared to idea doesn’t cause problems.

After LASIK, the baseline tear production is diminished. Therefore, a compromised lipid layer — that never caused problems before — turns into a problem. They aren’t making enough tears, and the ones they do make are evaporating quicker than they can be replaced. This is especially likely if a patient notices their symptoms are worst in the evening. That’s a sign that the evaporative loss of the day is causing the visual symptoms associated with their dryness.

A good omega-3 supplement helps dramatically in these cases. I’ve witnessed the turnaround firsthand countless times. My preference is Nordic Naturals (I have no financial interest with them) because the triglyceride formulation gives faster results in my experience. Every LASIK post-op patient can benefit from taking 2000 mg of omega-3 fatty acids daily. The ration of EPA and DHA doesn’t seem to make a difference in my experience. That’s a hefty dose, so it helps to be able to give the reason for taking it. That reason: a nice, thick lipid layer will help keep the eye lubricated during long days of staring at the computer. It is our silver bullet against the annoying effects of evaporative dry eye.

Lid scrubs These are used to treat anterior blepharitis. Anterior blepharitis is caused by a range of different bacterial flora and it is pretty common. After years of recommending demanding routines involving cotton-tipped applicators, distilled water, baby shampoo, and tea tree oil, OTC lid scrubs are a Godsend. My personal theory is that we will never know if the previous routine actually treated anterior blepharitis because no patient ever followed the instructions.

We recommend people take a week off of lid scrubs after LASIK. After that, it is recommended to continue with their normal routine. Anterior blepharitis contributes to the symptoms of dry eye after LASIK. The “scruff” on the base of the eyelashes causes inflammation and break up of the already weakened tear film. In general, lid scrubs with a dilute antiseptic tend to give better results than lid scrubs using only a detergent. Both are able to debride the lash line, but the antiseptic helps combat the bacterial flora causing the issue.

Conclusion The goal of this article is to help us all get on the same page. Decreased baseline tear production can be managed if we add some tears (that are preservative-free!) and help the tear film with the auxiliary supports mentioned here. Hopefully, this helped achieve that goal and makes post-LASIK dryness feel more like a bump in the road to recovery and less like the Wild West.

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