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Respect the DED

Prevention is better than cure when it comes to dry eye disease (DED) and ocular surgery. Dermot McGrath reports.

Dermot McGrath

Posted: Monday, November 1, 2021

Prevention is better than cure when it comes to dry eye disease (DED) and ocular surgery. Dermot McGrath reports.

Under-diagnosed, underestimated, and poorly understood, dry eye disease (DED) can negatively affect cataract and refractive surgery outcomes and lead to significant postoperative symptoms that can last anything from days to a lifetime for some unfortunate patients.

The stakes are high, yet screening for DED remains a hit-and-miss affair which too often leaves patients suffering a broad spectrum of complaints that can severely impact their quality of life and well-being.

The incidence and prevalence of DED after cataract surgery are widely underestimated, according to Béatrice Cochener- Lamard MD, PhD, Professor and Chairman of the ophthalmology department at the University Hospital of Brest, France.

“The rates in the scientific literature are anywhere between 10% to 34%, so it is quite common. There is a peak of severity that usually occurs around day seven postoperatively, but it may persist in some patients and become a chronic disease,” she said.

Dry eye symptoms are also very common in patients before and after refractive surgery. “Post-surgical tear dysfunction is the major cause of complaint after premium surgery including corneal refractive surgery,” said Jesús Merayo-Lloves MD, PhD, Director of the Instituto Universitario Fernández-Vega and Professor of Ophthalmology at the Universidad de Oviedo, Spain.

The prevalence of dry eye symptoms before undergoing LASIK is estimated to be between 38% and 75%, with contact lens intolerance due to dry eye a key reason why many patients pursue excimer laser ablation. Although post-LASIK dry eye usually peaks in the first few months after surgery and improves gradually thereafter, chronic dry eye disease has been reported to occur in anything from 20% to 40% of patients at least six months or longer after surgery.

WHY IS DED MISSED?

There are several reasons why DED tends to slip under clinicians’ radar so easily, according to Christophe Baudouin MD, PhD, Professor of Ophthalmology at Quinze-Vingts National Ophthalmology Hospital, Paris, France, and President of the newly formed European Dry Eye Society (EuDES).

“Dry eye is often not considered as sufficiently deserving of interest to many ophthalmologists. Compared to glaucoma, keratoconus, or other diseases, it seems far less severe. The attitude is ‘OK you have dry eye, you put in some drops, and it will be fine, end of problem,’” he told EuroTimes.

Another problem is patients with clinical signs of DED under slit-lamp examination are often asymptomatic.

“This is really a major problem. We regularly see patients with meibomian gland disease (MGD) or eyelid inflammation who never complain and tell us they are okay. However, these are the patients who will develop problems after surgery. Why are they asymptomatic despite the fact they have clinical signs? We really don’t know,” he said.

BELOW THE THRESHOLD

Marc Labetoulle MD, PhD, Université Paris-Saclay, Paris, France, believes many of these patients have active ocular surface disease that lies just below a threshold where the dry eye is not really apparent to them.

“However, this changes once they have cataract or refractive surgery, which takes the DED from below the threshold into something very real and tangible for the patient. They will then have the impression the dry eye problem is because of their surgery rather than the reality of the surgery bringing to light a pre-existing condition,” he said.

DIGGING DEEPER

An impaired ocular surface will affect preoperative planning, biometry, and IOL calculation. The workup to identify patients with ocular surface problems before cataract or refractive surgery typically involves a combination of patient history (comorbidities, medications, and epidemiological factors), a dry eye questionnaire, and clinical evaluation with corneal staining and tear breakup (TBUT) assessment.

Other tests such as Schirmer, meniscometry, meibography, or point-of-care exams such as MMP-9 or TearLab’s Osmolarity System may also obtain more detailed information in the presence of an abnormal result after staining or TBUT.

In addition to the Ocular Surface Disease Index (OSDI), Prof Labetoulle said he regularly uses a questionnaire called Pentascore, developed in association with Prof Baudouin and other co-workers, to assess DED quickly.

“A lot of dry eye questionnaires are very detailed and not very practical for everyday clinical use. Pentascore uses five short questions to obtain a quick assessment of whether the patient has DED or not. We have validated its use in a recent study published in the British Journal of Ophthalmology, ” he said.

Prof Baudouin says careful discussion with the patient using targeted questions can raise potential red flags before any clinical examination.

“Ask the patient if they have a stinging sensation, foreign body sensation, or a burning sensation. If they do, look closely at the eyelid. If the patient has swollen, red, or crusted eyelids, be careful, as they probably have MGD,” he said.

Fluorescein staining can quickly reveal potential issues with the ocular surface to an experienced observer, Prof Baudouin said.

“Put one drop of fluorescein in the eye and look for three key factors in less than 10 seconds: does it stain the cornea, does it stain the conjunctiva, and how does the tear film react. We are not necessarily calculating the TBUT very precisely, but if you observe a TBUT of fewer than five seconds, be very careful, as the patient probably has DED,” he said.

PREOPERATIVE TREATMENT

If a patient has dry eye prior to surgery, surgeons need to establish whether it is mild, moderate, or severe and treat accordingly. A wide array of treatment options is available depending on the type of ocular surface problem present, including artificial tears, hyaluronic acid, punctal plugs, autologous serum, anti-inflammatory topical drugs, oral omega-3 supplements, lid hygiene measures, warm compresses, thermal pulsation, and meibomian gland probing. Several algorithms such as the TFOS DEWS II and CEDARS are available to help guide DED management for clinicians.

Patients with uncontrolled or severe DED may need to be referred to a specialist and the cataract or refractive surgery deferred until the ocular surface has stabilised.

“If the DED is severe, the main problem is not the cataract or refractive error anymore,” Prof Labetoulle noted. “The priority is to optimise dry eye disease with all the tools in our arsenal. I will explain to the patient the severity of their DED and why it is important to improve the disease before proceeding to the surgery.”

INTRAOPERATIVE MEASURES

There are several measures to take to reduce the risk of inducing or aggravating DED during cataract surgery. Avoiding femtosecond-laser-assisted cataract surgery (FLACS) might be advisable in patients identified preoperatively with DED.

“Some reports in the scientific literature [say] FLACS is more damaging to the ocular surface than traditional phacoemulsification,” Prof Baudouin said. “However, we have performed a lot of FLACS in our hospital without seeing any major complications, so I don’t think the technique is the major factor in causing DED. It’s just probably safer to avoid FLACS in confirmed DED patients.”

Surgeons should also take care with anaesthetic and mydriatic eye drops that are potentially toxic to the corneal epithelium. “I have seen a lot of improvement in the ocular surface of my patients since I switched to intracameral mydriasis with Mydrane (Thea Laboratories), which works to dilate the pupil and reduce the pain because it contains an anaesthetic as well,” Prof Labetoulle said.

Other tips include avoiding the use of aspirating speculums and limiting light exposure from the operating microscope by using appropriate filters and reducing surgical time.

For refractive surgery, Prof Merayo-Lloves stressed the importance of rigorous surgery to reduce trauma and epithelial defects.


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