Dr Marguerite McDonald believes preoperative treatment of dry eye limits complications
We know that the tear film is the most important refracting surface of the eye, and dry eye is the most common and potentially the most devastating complication of surgery. In addition, we also know that disruption of the tear film very much magnifies the glare and halo that accompany all multifocal IOL surgeries.
Peer-reviewed literature supports the idea that every patient experiences dry eye after lenticular surgery, and infers that not all patients necessarily develop symptoms. Statistics show that dry eye is a major factor when assessing the success of ocular surgery. Peer-reviewed publications submit that there is a great prevalence of postoperative dry eye. While LASIK and PRK have been studied exhaustively, there are few publications concerning post-cataract dry eye.
Interestingly enough, however, the postoperative incidence of dry eye is even higher after lenticular surgery; one frequently cited study reveals that 87% of patients suffer from postoperative dry eye.1
In 2007, my colleague, Dr X-M Li, published a paper in Cornea, attesting to this figure,2 having studied 50 eyes of 37 patients. This paper documented that most patients suffered from ocular discomfort (as measured with the OSDI questionnaire) and exhibited corneal flourescein staining in the early postoperative period. Dr Li concluded that postoperative dry eye peaks at one month after cataract surgery, but persists for at least three months, and that visual function may be negatively impacted if the dry eye symptoms persist. In the discussion section of the paper, Dr Li stated that symptoms of dry eye will inevitably emerge in most patients and that misuse of their prescription eye drops was a major pathogenic factor.
Corneal sensation is absolutely critical for maintaining corneal epithelial integrity. We know that cataract patients are already at risk of dry eye because they are older. In addition, the temporal clear corneal incision - as small as it is - may actually transect one of the two main nerve bundles that enter the cornea at three and six o'clock. In many cases, limbal relaxing incisions are also performed, leading to the transaction of even more corneal nerves. Of course, LASIK denervates much more of the cornea because of the flap creation and then the ablation. It is important to note that at least 10% of refractive IOL patients (and perhaps as many as 30%) will undergo both cataract surgery and laser vision correction.
Preoperative treatment urged
Preoperative treatment of dry eye is a proven way to limit complications linked to dry eye; it improves outcomes because it decreases the incidence and severity of postoperative dry eye, and speeds visual recovery. In addition, with lenticular surgery, there is more reliable keratometry and improved IOL power accuracy. In the case of a patient needing LASIK after lenticular surgery (i.e. bioptics), the effective treatment of dry eye allows for an improved wavefront evaluation.
Many treatment options exist to help manage the ocular surface. Recently, our practice has employed a new tear formulation that has just become available over-the-counter. blink Tears (AMO), as research shows, is uniquely suited for post-cataract surgery. Dr Eric Donnenfeld, the lead author on a study that we performed last year, confirmed this in a poster presentation made at this year's ASCRS congress.3
The blink Tears formula has polyethylene glycol 400 as one of the active ingredients, sodium hyaluronate as a viscosity enhancer, a number of beneficial electrolytes, and Ocupure, as a very gentle preservative.