This is a supplement to EyeWorld Magazine that doctors can take a test after reading and receive CME credits for.
Issue link: http://cmesupplements.eyeworld.org/i/719259
The ocular surface: The first refractive interface of the eye 2 by Elizabeth Yeu, MD Symptom questionnaires: Necessary but not sufficient for preoperative patients Adequate screening necessitates additional targeted steps B ecause many cataract patients with ocular surface disease (OSD) are asymptomatic, a preoperative symptom questionnaire may not be ade- quate to detect this condition. According to a study by Trattler et al., more than 70% of our patients arriving for a cataract evaluation may have at least moderate dry eye disease. 1 OSD is so common in our older population that chronic dry eye can damage the sub- basal nerve plexus, resulting in a neurotrophic component. Therefore, they will not experi- ence irritation or foreign body sensation even if they have signif- icant staining. If OSD is not detected and managed before cataract and refractive surgery, it may adverse- ly impact postoperative visual outcomes. Preoperative examination Although it is important to es- tablish a standardized protocol to identify OSD, it does not need to be complicated. All of our new patients—es- pecially patients who are being evaluated for cataract surgery— complete a dry eye questionnaire. We specifically like the SPEED questionnaire, which is a bit shorter than the OSDI question- naire. Next, our technicians ask pa- tients about their blurred vision, specifically to tease out any inter- mittently blurred vision—one of the most common clinical symp- toms of dry eye. They also ask about the quality of their vision and whether their vision worsens with prolonged activity, such as driving, watching television, or reading. Cataracts can cause glare and impair vision, but if patients have fluctuating visual symptoms, need to blink frequently, or have excessive tearing, OSD is probably the cause. Based on results from these questions, our technicians perform tear osmolarity testing, which is very useful in determin- ing the stability of their overall tear film, as well as a range of different non-contact assessments (see sidebar), which are used to si- multaneously assess keratometric measurements and the pre-corne- al tear film quality. Research by Epitropoulos et al. demonstrated that K readings varied significantly in patients with hyperosmolar eyes compared with those that were normal. 2 Furthermore, among hyperos- molar eyes, there was a greater percentage of eyes with at least a 1.0 D difference in anterior corneal astigmatism, which was statistically significant. If OSD is not detected and treated before surgery, it will adversely affect preoperative measurements and IOL selection. When I review a corneal to- pography, my attention is focused on two images: the axial image to assess the regularity of the corneal astigmatism and the actual cor- neal exposure of the capture, and the Placido disc image in order to review the regularity of the mires. If the quality of the mires appears smudged or they are distorted, I'm immediately concerned about the accuracy of the topography as significant OSD is likely present. Some topography systems have built-in software that will display the surface regularity indices, which can also highlight distor- tions of the ocular surface that can be from dry eye disease. Disparity between the ker- atometric values from different devices or between the two eyes may also represent OSD, which directs a closer slit lamp ocu- lar surface exam. I thoroughly examine the ocular surface and evaluate the lids, everting and expressing them, trying to assess meibomian gland function. Another essential step is vital dye staining using lissamine green and fluorescein strips, particularly after some of the dye has disap- peared, in order to check for both positive and negative staining of the corneal surface. Expanding OSD testing options I n addition to administering a symptom questionnaire, asking a few targeted questions, and performing a thorough clinical examination, clinicians may turn to additional tests to diagnose ocular surface disease (OSD). Anterior segment optical coherence tomography (OCT) measures the tear film height, area, and conjunctivochalasis. With Placido disc topography, the quality of the mires allows me to gauge disease" may not be driven by very high numbers for inflammatory mediators. 3 If patients have severe symptoms but normal MMP-9 results, I look for other causes for their symptomatology, such as lid tarsal fibrosis, ABMD, or conjunctival chalasis. Because many dry eye cases have an MGD component, meibomography is one of our most useful tests and has been a tremendous advancement in OSD diagnosis and management. If we find significant meibomian gland their preoperative surface before we instill drops in their eyes. Surgeons also may consider MMP-9 testing, which provides an objective measure of inflammation and dry eye disease. I generally perform this test as a follow-up to the tear osmolarity, and to ascertain the presence of inflammation despite the patient's current treatment regimen. However, even patients with severe symptoms may not have positive results. Sambursky et al. has shown that 30 to 40% of cases of "dry eye atrophy, we know patients need a higher level of therapy and intervention to improve the existing gland function. Meibomography is also helpful in examining the anatomy and structure of the meibomian glands, especially if they are truncated or appear very congested. We can perform this in conjunction with expressing the glands to assess the quality of the meibum.