Optimizing the ocular surface before surgery may reduce dry eye postop
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An increase in dry eye symptoms after refractive or cataract surgery is a common occurrence, but the problem may be due to an exacerbation of a pre-existing condition rather than a new condition caused by ophthalmic surgery.
Cataract and refractive surgeries require the surgeon to cut across the corneal surface, severing nerve and fiber layers that are crucial for tear production. The surgical incision may cause dryness in patients eyes that is most likely self-limited or transient; however, a new occurrence of chronic dry eye that was caused by the surgery itself seems implausible to most surgeons.
Dry eye is exacerbated by any kind of eye surgery, OSN Cornea/External Disease Section Editor David R. Hardten, MD, said. I dont think it causes dry eye that wasnt there beforehand. It is an exacerbation of dry eye symptoms for a time after surgery, maybe 6 months to a year, and then it goes back to baseline.
Because dry eye can be chronic and progressive in nature, a report of worsened symptoms after surgery may, in fact, be due to the disease course itself, and not necessarily due to a surgical insult.
Image: Shari Fleming Photography
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Dry eye is not something that is static over time, so sometimes its going to get worse and sometimes its going to get better, Dr. Hardten said.
Pre-existing condition
In the context of cataract surgery, updated techniques that utilize smaller incisions and result in less damage to the ocular surface have been important in reducing complaints after surgery, Dr. Hardten said. However, these same techniques may have also increased the impact of dry eye symptoms after surgery.
Before the advent of microincisional techniques, for instance, a 10-mm incision for extracapsular cataract extraction may have resulted in significant astigmatism, swelling and iris irritation that led to slow or incomplete visual recovery.
Now, all those other things are pretty minimal, and the dry eye part of it starts to become a relatively bigger factor, Dr. Hardten said.
In refractive surgery, the surgery itself and the type of patient seeking correction may likewise be compounding factors in the assumption that surgery causes dry eye. According to OSN Refractive Surgery Section Editor Daniel S. Durrie, MD, the most likely patient to seek a surgical alternative to glasses is the one who becomes intolerant of contact lenses and many become contact lens intolerant because of dry eye signs or symptoms.
One of the biggest reasons people come in for refractive surgery is theyre having difficulty wearing their contact lenses, Dr. Durrie said. The most common reason they cant wear their contact lenses is their eyes are dry or they have blepharitis.
In patients who already have ocular discomfort, refractive surgery becomes a bigger challenge for the cornea, according to Dr. Durrie.
LASIK surgery is a stress test for dry eyes, he said. However, even in the context of a patient who does not have signs or symptoms of dryness before surgery, some degree of eye dryness may be expected postoperatively because the surgery cuts across the nerves, especially LASIK. PRK not as much, but definitely with LASIK. Those nerves send a signal to the lacrimal gland, and it gets interrupted.
Dr. Durrie likens the postoperative care of eye dryness to manually maintaining a system that would otherwise be automated if nerve and fiber layers had not been severed during surgery meaning it is important for the surgeon to provide good preop counseling and for patients to be diligent about instilling eye drops and, whenever possible, avoiding activities that might exacerbate dryness, such as staring at a computer screen without blinking.
Daniel S. Durrie |
If you look at young people without dry eyes that have healthy tear film, they dont have any problems with LASIK surgery, Dr. Durrie said. But even if I take a 20-year-old who has dry eyes going into it, they are going to get dry eye symptoms for 3 to 6 months afterwards, and then they are going to recover to their baseline.
While most postop dry eye may be due to exacerbation of a pre-existing condition, some eye dryness after surgery may be expected as part of the healing process. According to OSN Cornea/External Disease Section Member Terrence P. OBrien, MD, these self-limited cases may be due to LASIK-induced neurotrophic epitheliopathy.
In 2001, Wilson and Ambrósio described LASIK-induced neurotrophic epitheliopathy as likely caused by a loss of trophic influence to the epithelium attributable to cutting of the corneal nerve trunks during formation of the flap. This is supported by resolution of punctate epithelial erosions and rose bengal staining at 6 to 8 months after laser in situ keratomileusis when the corneal nerves tend to reinnervate the flap.
With LASIK we have a significant impact on corneal sensation because we are severing trunks of nerves that are important for mediating sensation of the cornea, Dr. OBrien said. Virtually every patient will have a transient neurotrophic keratopathy thats typically mild, and it recovers over a period of weeks to months.
Preparing the ocular surface
The potential for postoperative complications does not necessarily contraindicate surgery in dry eye patients, according to Dr. Durrie, but it should highlight the need to prepare both the ocular surface and the patient for potential postoperative dryness.
LASIK doesnt cause dry eye; it aggravates pre-existing dry eye, Dr. Durrie said. Ten years ago, we used to think that LASIK surgery caused dry eye. That was because we didnt do a good job of screening people, so people went into surgery and afterwards had dry eye.
This concept of corneal surface optimization is, I think, very important before proceeding with LASIK or, for that matter, refractive IOL, Dr. OBrien said. Having an aggressive approach to dry eye in these patients, and particularly this corneal surface optimization, will require a multifaceted approach both diagnostically and therapeutically to restore the stability of the tear film before surgery and allow repair of the cells and provide sustained protection of the cells, especially during the inter-blink interval when patients are most vulnerable.
Terrence P. O'Brien |
According to Dr. Hardten, in the context of cataract surgery, in which patients often demand refractive results, preop screening and counseling may help protect against patients blaming the surgery or the surgeon for their newly evident dry eye.
I dont think [dry eye] excludes a patient from having surgery, but I think the surgeon is more aggressive about dry eye management and blepharitis management if you are dealing with those tougher patients, Dr. Hardten said.
Dr. Hardten said he performs an ocular surface stress test in every patient. Before surgery, a patient has a local anesthetic for the typical pressure reading and vision test and dilating drops for the fundus examination, and is then re-examined after the usual waiting period with special attention paid to see if irregular epithelium or punctate keratopathy is present.
Other measures may be useful for screening, including the Ocular Surface Disease Index, which Dr. OBrien called a validated questionnaire that had been used in some other dry eye treatment trials and was found to be a useful tool. More specific diagnostic testing in suspect cases, he said, should include corneal and conjunctival staining and assessing the tear film breakup time.
According to Dr. Durrie, ocular surface optimization before surgery should center on getting the surface healthy enough to operate on because if you have a hostile environment and trying to get them to heal well, youre asking for trouble.
Refractive surgeons today, he said, have an advantage because treatments for dry eyes and other ocular surface maladies have been established over the last decade. Treatment can start with lid hygiene and omega-3 oral nutritional supplementation and progress, as signs and symptoms warrant, to tear replacements, anti-inflammatory agents and punctal occlusion.
For cataract patients, medical management of the ocular surface has advanced to the point where virtually any ocular surface can be brought to viability, Dr. Hardten said. In addition, the techniques of lens removal and IOL insertion are less harmful to the cornea than in the past.
Likewise, in refractive surgery, most patients can eventually receive laser correction, although it may be prudent to delay surgery until medical management can prepare the ocular surface for the challenge of surgery.
A comprehensive refractive surgeon who is going to take care of their patients long-term is going to spend a lot of time looking at patients tear film and their dry eye symptoms before they even consider any kind of surgery, Dr. Durrie said.
Just as minimally invasive surgery is important in cataract surgery, surgery that is minimally traumatic to the ocular surface is also important during a refractive correction, according to Dr. Durrie. In particular, laser cut flaps may be preferable to manual microkeratomes because they can potentially cut thinner flaps with greater predictability.
The femtosecond laser in general and I mainly use IntraLase (Abbott Medical Optics) allows us to do thinner flaps, smaller flaps, which cut less fibers and cut less nerves, Dr. Durrie said
Delayed procedures
Whereas cataract surgery removes an impediment to vision, refractive surgery is still an elective procedure with viable alternatives. As a result, not all patients will benefit from refractive surgery, especially if the potential for dry eye is overwhelming.
The majority of patients can still proceed with the procedure, but we have a threshold to delay procedures until things are optimized, Dr. OBrien said.
In addition, it might be necessary to opt for a surgical procedure that does not require as much nerve truncation on the ocular surface, such as PRK, if predisposing risk factors suggest a greater likelihood of postoperative dry eye.
One group would be postmenopausal women who have a low amount of refractive error, Dr. OBrien said. I think in these older individuals who are already predisposed, it is better to avoid the LASIK flap and a surface ablation, especially if it is going to be a low treatment.
However, while the ocular surface can be repaired and maintained through surgery in most patients, Dr. OBrien said that there will always be a subset of patients who will not recover viability of their ocular surface and, therefore, will be unable to endure the challenge of eye dryness after refractive surgery.
Identify risk factors
Risk factors may be useful in identifying patients who are more prone to dry eye symptoms after surgery. According to OSN Contact Lenses Section Editor Penny A. Asbell, MD, FACS, MBA, some risk factors may be underappreciated or unknown to physicians. In particular, diabetes may confer a two times greater risk for developing dry eye than what is seen in age-matched subjects who do not have diabetes.
Penny A. Asbell |
[Diabetes is] something to think about whether you have LASIK or not if you have persistent dry eye and you cant figure out whats going on, especially if they have type 2 diabetes and it hasnt been diagnosed or they havent told you about it, Dr. Asbell said.
In a prospective, observational cohort by Kaiserman and colleagues that investigated the prevalence of keratoconjunctivitis sicca in a cohort of 22,382 diabetic patients, 20.6% of diabetic patients reported using ocular lubrication compared with 13.8% of nondiabetic patients. While the prevalence of dry eye increased with advancing age, the presence of diabetes remained an independent risk factor for need for the ocular lubrication.
Of all the risk factors looked at in the study, poor glycemic control, measured by annual HbA1c levels, yielded the most significant association with dry eye.
In every age category, in almost every age group, [dry eye] was almost two times higher in the diabetic group vs. an age-controlled normal group of patients, Dr. Asbell said.
A study by De Paiva and colleagues highlighted another potential risk factor: depth of ablation and degree of refractive error correction. The study, a prospective, single-center, randomized, 6-month trial comparing two microkeratomes, indicated that dry eye occurs commonly after LASIK surgery in patients with no history of dry eye.
Cox regression analysis showed that the preoperative spherical equivalent of myopia had a 20% chance of developing dry eye with each increase of 1 diopter, the study authors wrote. Laser calculated ablation depth and combined ablation depth and flap thickness had a 1% greater chance of developing dry eye with every 1-µm increase.
Evidence gathered from other studies indicates that dry eye after LASIK may present a different clinical picture than classic dry eye syndrome, Dr. Asbell said.
When you look at dry eye after LASIK, it happens equally in men and women. We often think of dry eye as a womens thing, but it is actually common in both, she said. The etiologies that cause dry eyes normally may not be exactly the same in LASIK patients.
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Other factors recent lid surgery or lid inflammation that leads to poor tear production or tear distribution across the ocular surface, damage to the conjunctiva, systemic diseases that may cause or exacerbate dry eye, and the use of certain medications may also contribute to dry eye after LASIK.
Identifying patient-specific responses to the LASIK procedure may also help elucidate the cause or causes of dry eye in patients after refractive surgery. For instance, Dr. Asbell said, goblet cells may be damaged by the suction device used to hold the eye during LASIK surgery, and some patients may have a hyperalgesic response to truncation of nerve and fiber networks on the cornea, which may increase cytokines either independently or as a result.
Dry eye after LASIK is not an uncommon problem and can exist even in those that had no prior history before the LASIK, Dr. Asbell said. by Bryan Bechtel
References:
- Albietz JM, Lenton LM. Management of the ocular surface and tear film before, during, and after laser in situ keratomileusis. J Refract Surg. 2004;20(1):62-71.
- Ambrósio R Jr, Tervo T, Wilson SE. LASIK-associated dry eye and neurotrophic epitheliopathy: pathophysiology and strategies for prevention and treatment. J Refract Surg. 2008;24(4):396-407.
- De Paiva CS, Chen Z, Koch DD, et al. The incidence and risk factors for developing dry eye after myopic LASIK. Am J Ophthalmol. 2006;141(3):438-445.
- Hardten DR. Dry eye disease in patients after cataract surgery. Cornea. 2008;27(7):855.
- Kaiserman I, Kaiserman N, Nakar S, Vinker S. Dry eye in diabetic patients. Am J Ophthalmol. 2005;139(3):498-503.
- Lam H, Bleiden L, de Paiva CS, Farley W, Stern ME, Pflugfelder SC. Tear cytokine profiles in dysfunctional tear syndrome. Am J Ophthalmol. 2009;147(2):198-205.
- Li X, Hu L, Hu J, Wang W. Investigation of dry eye disease and analysis of the pathogenic factors in patients after cataract surgery. Cornea. 2009;26(Suppl 1):S16-S20.
- Salomão MQ, Ambrósio R Jr, Wilson SE. Dry eye associated with laser in situ keratomileusis: Mechanical microkeratome versus femtosecond laser. J Cataract Refract Surg. 2009;35(10):1756-1760.
- Savini G, Barboni P, Zanini M. The incidence and risk factors for developing dry eye after myopic LASIK. Am J Ophthalmol. 2006;142(2):355-356.
- Savini G, Barboni P, Zanini M, Tseng SC. Ocular surface changes in laser in situ keratomileusis-induced neurotrophic epitheliopathy. J Refract Surg. 2004;20(6):803-809.
- Wilson SE, Ambrósio R. Laser in situ keratomileusis-induced neurotrophic epitheliopathy. Am J Ophthalmol. 2001;132(3):405-406.
- Penny A. Asbell, MD, FACS, MBA, can be reached at Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 118, New York, NY 10029; 212-241-7977; fax: 212-289-5945; e-mail: penny.asbell@mssm.edu.
- Daniel S. Durrie, MD, can be reached at Durrie Vision, 5520 College Blvd., Suite 200, Overland Park, KS 66211; 913-491-3737; fax: 913-491-9650; e-mail: ddurrie@durrievision.com. Dr. Durrie is a paid consultant for Abbott Medical Optics.
- David R. Hardten, MD, can be reached at Minnesota Eye Consultants, 710 E. 24th St., Suite 100, Minneapolis, MN 55404; 612-813-3600; fax: 612-813-3658; e-mail: drhardten@mneye.com.
- Terrence P. OBrien, MD, can be reached at Bascom Palmer Eye Institute, 7108 Fairway Drive, Palm Beach Gardens, FL 33418; 561-515-1544; fax: 561-515-1588; e-mail: tobrien@med.miami.edu.