Post-LASIK dry eye with punctate epithelial erosions Source: William B. Trattler, M.D.
Dry eye severity grading scheme
If conventional wisdom holds true, an unlucky post-op LASIK or refractive IOL patient who goes home with an irritating case of dry eye will complain to a dozen or so friends about the experience. That number probably increases tenfold with social media thrown into the mix—not a good scenario for surgeons who count on these patients for their livelihood.
Dry eye has quite an impact on a patient's satisfaction after one of these elective procedures. Experts now advise colleagues to treat the dry eye before even scheduling the surgery. A healthy ocular surface has become a pre-op must.
Look for it
Surgeons should first know the potential exacerbating factors for dry eye disease, including various systemic medications such as antihistamines and antidiuretics and the presence of systemic diseases such as rheumatoid arthritis. Other ophthalmic conditions that can accompany dry eye disease or make it worse are blepharitis, meibomian gland dysfunction, lagophthalmos, and ocular rosacea. Those may be treatable with warm compresses and lid hygiene scrubs, as well as artificial tears, oral doxycycline, and possibly topical antibiotics and steroids.
"If patients have dry eye pre-operatively, they are at an increased risk of developing worsening signs and symptoms post-operatively," said William B. Trattler, M.D., cornea specialist, Center for Excellence in Eye Care, Miami. "Since dry eye is so common in patients, we have to be aggressive and look for it."
In LASIK, an unhealthy ocular surface will affect wavefront and topography readings. For cataract surgery, it could affect IOL calculations and the axis and magnitude of astigmatism.
"That can affect your planning for surgery," Dr. Trattler said.
How to test
Dr. Trattler said his preferred method of testing for dry eye is fluorescein straining and testing for tear break-up time (TBUT).
Don't expect patients to come in complaining of the common symptoms, he warned, because a good portion of them could be asymptomatic.
Dr. Trattler sited a prospective review of 272 eyes scheduled for cataract surgery. A majority of those patients were found to have dry eye and not even know it. Their history, which most surgeons are hard-wired to ask about, wasn't helpful.
"We had them fill out a questionnaire, but they didn't report any problems," he said. The testing told a different story, however. "We had about 62% of patients who had severely abnormal TBUT at 5 seconds or less," Dr. Trattler said. Most practitioners feel 7-8 seconds is abnormal.
The study was presented at World Cornea Congress VI in Boston in 2010, and it is submitted for publication.
Although dry eye is prevalent in older populations, especially peri- and post-menopausal women, Dr. Trattler said younger patients are also at risk, and contact lenses may be to blame for masking the symptoms.
Doctors should test all patients for dry eye, even those without clear evidence of the disease, especially since it's better to treat the disease pre-op, Dr. Trattler said. "Everyone thinks about symptoms of pain, irritation, and foreign body sensations, but in reality the more important issues are poor quality of vision issues," he said. "Without a good, healthy tear film, patients will complain of poor quality of vision, maybe even fluctuation of vision, and that their visual results after surgery are not what they expected. They may have paid a lot of money out of pocket and yet their quality of vision is less than satisfactory."
Besides TBUT and fluorescein, Stephen C. Pflugfelder, M.D., professor of ophthalmology, Baylor College of Medicine, Houston, recommends testing with lissamine green staining and Schirmer's test, which might help the practitioner decide whether the dry eye is aqueous deficient.
"There are some new sophisticated tests that can measure the volume of tears in the eye, like OCT [optical coherence tomography]," he said. "That's turning out to be a great test because we can see for the first time the area where tears accumulate along the lower lid."
A tear osmolarity test can measure the osmolarity and the tear film in a microdroplet, as well.
"That hasn't gotten widespread acceptance yet, and neither has OCT, but both of them have the potential to identify dry eye," Dr. Pflugfelder said. Other risk factors for dry eye include smoking, diet (lack of omega-3 and omega-6 fatty acids), and medications such as antidepressants and antispasmodics, like the ones that are used for bladder control.
Using DEWS Dr. Pflugfelder said he uses the Dry Eye Workshop (DEWS) system to evaluate a framework for treatment. DEWS was published in the April 2007 issue of The Ocular Surface as a follow up to the Delphi panel sponsored by the National Eye Institute and ophthalmic industry. Dr. Pflugfelder was the chairman of the management and therapy subcommittee.
DEWS, which expanded on the Delphi criteria, identified dry eye as "a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface."
It classified the etiology of the disease into two categories: aqueous tear deficient and evaporative. "With level 2 or worse, steroids should probably be used for treatment, at least short term," Dr. Pflugfelder said. "No one in level 4 should have LASIK. These people might not even be good candidates for IOLs."
Although post-op dry eye can be nerve-wracking for patients, Dr. Pflugfelder said it will resolve with time.
"Tear function tends to improve over the first 6 months after LASIK," he said. "The natural history is that it will improve on its own, but it may improve faster with treatment. LASIK satisfaction overall is extremely high, but there are a few vocal patients who are very unhappy."
Dr. Pflugfelder said those patients may be experiencing something beyond dry eye, a type of neuralgia. "The problem with post-LASIK dry eye is a lot of people who are diagnosed as having dry eye after LASIK really don't have dry eye. If they have irritation symptoms or pain, they may actually have a type of neuralgia due to the way that the nerves seal in the cornea. They become hypersensitized and it can drive them crazy," he said. Identifying the patients and treating them before operating can make a good procedure even better, Dr. Pflugfelder said. The same is true with multifocal IOL patients, he added.
"On a weekly basis, I see people with pretty bad dry eye after LASIK who probably should never have had the procedure to begin with," he said. "With multifocal IOL patients, a big problem is if they do have dry eye or an unstable tear film and you implant a multifocal IOL, it will divide light rays for distance and near. The light that now comes in the eye and hits the multifocal IOL no longer gives 100% of the light rays for distance or near. Contrast sensitivity goes down a little bit. In someone with a normal tear film, that's OK, but if the patient has an abnormal tear film, it can decrease contrast sensitivity and scatter light. It can drive some people with a multifocal IOL crazy."
Avoid dry eye in surgery
Creating smaller flaps during LASIK can help mitigate some of the follow-up dry eye complications, both surgeons said. "Smaller flaps are probably better because they don't cut as many nerves. The depth of the ablation is crucial," Dr. Pflugfelder said. "The deeper the laser ablation, the more chance patients are going to have dry eye, especially with LASIK because you're already cutting the flap and ablating deeper."
Hyperopic LASIK increases the risk. "I've seen some really miserable patients, especially hyperopic LASIK patients, because it's a bigger flap and bigger treatment zone," Dr. Pflugfelder said. "I think those patients are probably better off having refractive lens exchange because there's minimal risk of dry eye, and the quality of their vision would be a lot better."
Dr. Trattler agreed about the size of the flaps created during LASIK. "We believe that thinner flaps reduce the risk of developing dry eye afterward. Also, with a deeper flap, we sever more corneal nerves," he said. "A deeper, wider flap can make dry eye worse. You want to go with a small flap if you can. Obviously, if it's a hyperopic treatment you can't do that. With myopic treatments, don't make it extra wide. Try to narrow it down a bit. If you have a wider hinge, you're severing fewer nerves, too."
To get thinner flaps, Dr. Trattler uses the IntraLase (Abbott Medical Optics, Santa Ana, Calif.), which can target 100 or 110 microns versus 120 or 130 microns. "Make your hinge size a little bigger; that can help, too," he advised. "There's also the thought
that with the new model of the
IntraLase, the 150 kHz, you can make inverted flap edges. The flap fits in a tongue and groove, and there might be more reconnecting of the corneal nerves. The flap is beveled in."
Dr. Trattler uses Restasis (cyclosporine, Allergan, Irvine, Calif.) and topical steroids for a classic dry eye patient. "If it turns out the patient has more of a blepharitis picture, I will give the patient steroids and azithromycin topically," he said. Many times, surgery will have to be postponed until the ocular surface is healthy enough to handle it.
Despite the extra time, Dr. Trattler said it will be worth it, for both the patient and the surgeon.
"We want our patients to have the best experience and outcomes possible," Dr. Trattler said.
1. Nassaralla BA, McLeod SD, Nassaralla JJ Jr. Effect of myopic LASIK on human corneal sensitivity. Ophthalmology. 2003;110:497-502.
2. Donnenfeld ED, Ehrenhaus M, Solomon R, et al. Effect of hinge width on corneal sensation and dry eye after laser in situ keratomileusis. J Cataract Refract Surg. 2004;30:790-797.
3. Nassaralla BA, McLeod SD, Boteon JE, et al. The effect of hinge position and depth plate on the rate of recovery of corneal sensation following LASIK. Am J Ophthalmol. 2005;139:118-124.
4. Stern MF, Pflugfelder SC. Inflammation in dry eye. The Ocular Surface. 2004;2:1124-1130.
5. Dry Eye Workshop Panel. 2007 Report of the Dry Eye Workshop. Ocul Surf. 2007;5:2:65-204.
Editors' note: Dr. Pflugfelder has no
financial interests related to his comments. Dr. Trattler has financial interests with AMO, Alcon (Fort Worth, Texas), Allergan, and Inspire Pharmaceuticals (Raleigh, N.C.), among other companies.
Pflugfelder: 713-798-4732, firstname.lastname@example.org
Trattler: 305-598-2020, email@example.com