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Dry eye prevention and management crucial to refractive surgery success
The changes in corneal shape affect tear film dynamics, leading to increased osmolarity and altered distribution of the tear film.
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 Béatrice Cochener |
Prevention and management of dry eye plays a crucial role in the success of refractive surgery, according to a specialist.
“A careful preoperative assessment allows us to identify the patients who have to be excluded, but also those who can still be candidates to refractive surgery if the dry eye condition is properly treated preoperatively and for a longer time postoperatively,” Béatrice Cochener, MD, OSN Europe Edition Chairperson of the Editorial Board, said in a keynote lecture at the winter meeting of the European Society of Cataract and Refractive Surgeons in Istanbul.
The definition of dry eye has changed in recent years, she said. Dry eye was defined by the 1995 National Eye Institute Industry Dry Eye Workshop as “a disorder of the tear film due to tear deficiency or excessive evaporation, which causes damage to the interpalpebral ocular surface and is associated with symptoms of ocular discomfort.”
According to a 2007 updated definition by the Dry Eye Workshop Definition and Classification Subcommittee, “dry eye is 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.”
Key factors
Three important factors were introduced in the updated dry eye definition, Dr. Cochener said: the multifactorial complexity of the disease, the concept of osmolarity and the key role of inflammation.
The ocular surface is a system, and as such it is deregulated by any alteration of its individual components, she said. A shift in the balance between tear production and evaporation results in increased osmolarity. In turn, the excessive concentration of salts in hyperosmolar tears triggers a self-perpetuating inflammatory response because tear production is insufficient for washing out the pro-inflammatory mediators. Nerve stimulation also leads to inflammation of the lacrimal gland and consequent tear film dysfunction.
Refractive surgery impacts the ocular surface and tear film dynamics. While the damage caused by surface ablation is more superficially confined and transient, the LASIK flap transects many afferent sensory nerve fibers. In addition, the changes in corneal shape affect tear film dynamics, leading to increased osmolarity and altered distribution of the tear film.
“Dry eye in LASIK is not rare; it is estimated to occur in 50% of the cases. Common symptoms of dryness, occurring between 1 and 3 months, are foreign body sensation, burning, itching, stinging and lid heaviness,” Dr. Cochener said. “They can progress in some cases to involve punctate epithelial keratopathy within the flap. Visual symptoms may appear, such as fluctuation of vision, glare, night vision problems and severe discomfort in 10% of the population.”
Therapeutic strategies for dry eye begin with non-preserved artificial tears. Cyclosporine is available in some countries and can be used along with anti-inflammatory agents in cases of severe dry eye.
In PRK cases, a bandage soft contact lens is often used until the point of epithelium regrowth and nerve regeneration. However, to avoid discomfort and potential infection, a bandage contact lens should only be used when tear production is normal. In some cases, temporary punctal occlusion may be necessary.
There is no evidence of the efficacy of nutritional supplements in these cases.
“There is a place for autologous serum in severe dry eye, but it should be used with caution and not routinely, as it may promote hyperplasia, regression and infection,” Dr. Cochener said.
Detecting dry eye
A preoperative dry eye condition is a risk factor for postoperative dry eye and must be identified and treated before refractive surgery.
“Patients with preoperative dry eye will have their condition exacerbated by severing the nerves with the flap cut and photoablation. This is a risk we don’t want to run,” Dr. Cochener said.
All available methods for ocular surface evaluation should be used, and risk factors such as contact lens intolerance, systemic conditions and use of specific classes of medications should be considered. However, preoperative assessment is not always easy because dry eye is frequently subclinical and may remain undetected by traditional tests such as slit lamp, Schirmer and staining.
The TearLab Osmolarity Test (TearLab Corporation) measures tear osmolarity and provides data for preoperative ocular surface assessment. The rapid, non-invasive test is normally performed by a technician and can detect aqueous defect and evaporation.
“We used it in 36 eyes of 28 patients prior to PRK and found that 44% of the patients had hyperosmolar tears and therefore asymptomatic dryness before surgery, with no correlation between objective tests and subjective scores,” Dr. Cochener said.
In these cases, prophylactic optimization of the ocular surface for a few weeks to 3 months before surgery helps to avoid postoperative dry eye. Pretreatment can even allow patients who would otherwise be excluded to successfully undergo refractive surgery, provided that a more intensive and prolonged treatment is also administered after surgery, Dr. Cochener said.
“Although the price of the TearLab [Osmolarity Test] is a limitation to its introduction in routine practice, this device could greatly improve our standards of care,” Dr. Cochener said. “We can clearly define the subpopulation of patients who are at risk of postoperative ocular surface-related complications, exclude those who have to be excluded, divert to PRK some LASIK candidates, and pretreat those who are still eligible for surgery. We can also test the osmolarity changes after the use of lubricants and compare the efficacy of different agents.”
According to Dr. Cochener, several additional tools that could be used in the detection and quantification of dry eye have recently been developed: Optical Quality Analysis System (Visiometrics), with double-pass measurement of diffusion and light scatter; InflammaDry Detector (RPS), a rapid, point-of-care test to detect the MMP-9 inflammatory marker; LipiView (TearScience), a single platform combining lipid phase measurement and a mask for secretion stimulation and treatment of meibomian gland dysfunction; Painless Plug (FCI) for punctal occlusion after refractive surgery in cases of preoperatively detected ocular surface disease; and updated masks and goggles for management of meibomian gland dysfunction. – by Michela Cimberle
- Béatrice Cochener, MD, can be reached at Institut de Synergie des Sciences de la Santé – LATIM – CHRU Morvan, Bât 2 bis – 5 avenue FOCH, 29609 Brest Cedex, France; +33-2-98-01-81-30; fax: +33-2-98-01-81-24; email: beatrice.cochener-lamard@chu-brest.fr.
- Disclosure: Dr. Cochener has no relevant financial disclosures.