DETECTING AND TREATING OCULAR SURFACE DISEASE

Cataract and refractive surgeons must be careful not to misjudge the importance of detecting and treating ocular surface disease (OSD), said Béatrice Cochener MD, PhD, at the second EuCornea Congress.

“As we aim for perfection in our surgical outcomes, we are coming close to achieving super vision with excimer laser vision correction as well as with our intraocular procedures. However, OSD continues to be a source of postoperative frustration for patients and surgeons,†said Prof Cochener, chair, Department of Ophthalmology, University of Brest, France.

“Preoperative identification of OSD is necessary not because its presence contraindicates surgery, but because it can guide appropriate strategies. Optimising outcomes and patient satisfaction after surgery depends on preparing the ocular surface for the procedure, protecting it with appropriate intraoperative techniques, and rehabilitation of the ocular surface after the procedure with awareness that long-term care may be needed to maintain ocular surface integrity.â€

Data on the prevalence of OSD and its adverse sequelae in patients undergoing laser and cataract refractive surgery underscore the importance of undertaking a careful evaluation to identify a pre-existing condition or risk factors for dry eye after surgery. OSD resulting from dry eye disease associated with blepharitis, ocular allergy, or other etiologies is estimated to be a significant comorbidity in up to 30 per cent of LASIK candidates and in up to 50 per cent of the older cataract surgery population, said Prof Cochener.

In addition, corneal surgery can induce or exacerbate OSD through multiple pathways mediated by inflammation or involving alterations in various components of the ocular surface system or its secretions. The result may be bothersome, irritation-related symptoms after surgery causing patient dissatisfaction. However, there may also be fluctuating vision, refractive regression, deterioration in visual quality, decrease in visual acuity, as well as glare and night symptoms.

Furthermore, OSD and its underlying etiologies, including blepharitis and ocular allergy, are risk factors for true complications after laser vision correction, including infection, increased inflammation, delayed healing, and corneal opacity, while pre-existing OSD in patients undergoing cataract surgery can affect the accuracy of IOL power and astigmatic axis calculations because of its impact on topographic and keratometric measurements.

Being proactive

Unfortunately, OSD often emerges as a postoperative surprise because unless the patient spontaneously volunteers complaints preoperatively, a careful evaluation for OSD may not be undertaken. To avoid this situation, all refractive and cataract surgery candidates should have a thorough history and evaluation focusing on detecting dry eye and predisposing factors. The workup should include questions about vision-related quality of life, a systemic and ocular history, medication history, and slit-lamp examination of the ocular surface and lids. Standard clinical tests, including staining

for ocular surface damage, measurement of tear breakup time, and a Schirmer's test, help to detect frank OSD, but may not identify patients with subclinical disease that can be worsened postoperatively, said Prof Cochener.

Increasing appreciation for the prevalence and clinical importance of OSD has prompted industry to develop new diagnostic tools. A device for non-invasive measurement of tear osmolarity (TearLab) in the office is now commercially available. However, Prof Cochener stated that considering its cost, she believes it is best reserved for use in clinical research studies in academic settings.

Another new commercially available device (InflammaDry Detector, RDS) evaluates the tears for an elevated level of matrix metalloproteinase-9 (MMP-9), a nonspecific marker of inflammation that has been shown to be consistently elevated in dry eye. When present at high levels, MMP-9 can cause functional alteration of the epithelial barrier, corneal desquamation, and surface irregularity, Prof Cochener explained.

The Optical Quality Analysis System (OQAS, Visiometrics) provides an optical assessment of tear film quality dynamics based on a double-pass technique, and Prof Cochener said she has found it very useful for the detection and follow-up of tear film abnormalities in surgical patients pre- and postoperatively.

Another manufacturer, TearScience, has introduced three devices for detecting and treating abnormalities due to meibomian gland dysfunction. One device (LipiView) is an ocular surface interferometer that provides a quantitative analysis of the lipid layer of the tear film. Another instrument (Meibomian Gland Evaluator) is designed to enable detection of meibomian gland obstruction at the slit-lamp, and a third technology (LipiFlow) works with thermal pulsation to open obstructed meibomian glands.

Postoperative care

Dryness after LASIK results in part from changes in corneal shape that affect tear film distribution, but flap creation also plays an important role because transection of afferent sensory nerves results in decreases in the neurotrophic influence on epithelial cells, blink rate and reflex and basal tear production. Making a thinner flap with a larger hinge and smaller diameter can help to minimise the impact of flap creation on postoperative dryness. Use of the femtosecond laser to create a flap with inverted edge geometry may also be helpful, although lower energy settings are also important.

Prof Cochener said that all patients should be educated about the risk of dryness after corneal surgery and routinely treated with non-preserved artificial tears postoperatively for at least one to three months with ongoing use maintained as needed based on patient comfort. For patients with more severe dry eye, topical cyclosporine 0.05 per cent emulsion (Restasis, Allergan) started preoperatively and continued after surgery is an option in the US.

Treatment of blepharitis should be continued after surgery, application of a bandage soft contact lens is helpful after PRK, and some surgeons recommend nutritional supplementation with omega-3 fatty acids to improve the tears, although its benefit is controversial. Punctal plugs can help to maintain the tear film on the ocular surface, and a multicentre study is currently under way in Europe investigating this strategy using the Painless Plug (FCI).