Appropriate preparation of the ocular surface can improve results
The preoperative condition of the ocular surface affects outcomes after implantation of IOLs in patients undergoing cataract surgery. Appropriate management to prepare the ocular surface for surgery can result in excellent visual outcomes.
Dr Elizabeth A. Davis, a cornea specialist in private practice in Maplewood, Minnesota, USA, explained how she prepares patients for cataract surgery and implantation of an IOL.
"Dry eye disease is a highly prevalent condition, and chronic dry eye affects about 4.3 million people in the US [alone]; 7 to 10 million people have dry eye symptoms that require the use of artificial tears," Dr Davis said. "From 5% to 15% of individuals who are 55 years and older, and more likely to be of an age to develop cataracts, have moderate to severe dry eye, and the incidence of dry eye disease increases with age."
"These problems are exacerbated especially with implantation of a presbyopic IOL," she said.
In addition, poor quality of the ocular surface can affect the accuracy of the preoperative measurements (i.e., the keratometry and topography measurements). The values obtained may be unreliable, unless the patient is treated.
Ocular surface disease can develop from a number of causes. These include neurogenic aetiology resulting from damage to the corneal sensory nerves that can lead to inhibition of the reflex arc through the brain and into the lacrimal glands and a decrease in the volume of aqueous tears, Dr Davis explained.
The nerves that are affected release epithelial trophic factors, which can result in inhibition of re-epithelialization and punctate keratopathy.
The conjunctival goblet cells can also be affected in a couple of ways, either mechanically or as a result of medication effects, resulting in decreased mucin production in the basal layer of the tear film. The cataract surgery itself can lead to release of cytokines and T-cell activation during the inflammatory cascade.
"One of the most significant precursors of ocular surface disease is blepharitis," Dr Davis said. "Most patients develop a combination of anterior and posterior blepharitis, which is highly prevalent in elderly patients."
Other factors that predispose patients to ocular surface disease are oral medications and systemic illnesses, especially autoimmune diseases.
Preparing the ocular surface
Certain diagnostic tests are necessary to prepare patients for cataract surgery, Dr Davis noted.
Surgeons should evaluate the lids and lashes for signs of blepharitis, the tear film break-up time, vital dye staining, and the height and quality of the tear lake. The Schirmer test may not be as valuable because of the interobserver and intraobserver variability.
The aetiology determines the treatment. For patients with blepharitis, Dr Davis uses warm compresses, azithromycin (AzaSite, Merck), oral doxycycline, and steroids prescribed for the short term. Artificial tears, topical cyclosporine (Restasis, Allergan), omega-3 supplements, steroids and punctal plugs improve dry eye.
The ocular surface is an important contributor to visual outcomes after IOL surgery, she said.
"Blepharitis and dry eye are prevalent in the cataract population and postoperatively can derail an otherwise good outcome," Dr Davis said. "It is important to look for risk factors for dry eye disease preoperatively. Dry eye disease is multifactorial but it is perpetuated by an inflammatory cascade.
"Lid hygiene, artificial tears, punctal tears help ameliorate dry eye disease," she added. "Azithromycin, cyclosporine and steroids work on the cause of dry eye. Appropriate management can result in excellent outcomes after cataract surgery.
Dr Davis is a consultant for Merck and can be contacted by E-mail: firstname.lastname@example.org