Timing & preparation for the diabetic eye
While it is not the ophthalmologist’s role to manage a patient’s diabetes, there are things they can do to optimise surgical outcomes
As a vitreoretinal and cataract surgeon, reading “diabetes mellitus” in a medical chart sets all the alarm bells ringing even before the patient enters the examination room. Undesirable scenarios pop into my head: early-onset cataract with suboptimal pupillary dilation, postoperative macular oedema, systemic comorbidities and anticoagulant use…
It always takes a moment or two before I manage to reassure myself that our current, collective knowledge of the ocular complications of the disease is sufficient to manage (or, preferably, prevent) anything we come across these days. But is this true? Can we?
The risks of cataract surgery in the diabetic patient can be divided into the standard surgical complications and diabetes-related complications, the latter of which can be further subdivided into progression of diabetic retinopathy and appearance or worsening of DME.
And although diabetic retinopathy does not seem to worsen due to cataract surgery, diabetes itself is a risk factor for disappointing visual outcomes.
Professor Morten la Cour
“Poor visual outcome after cataract surgery in diabetics is more closely correlated with poor metabolic control rather than the surgical trauma itself,” said Professor Morten la Cour, University of Copenhagen, Denmark, during the ESCRS/ EURETINA Symposium: The Diabetic Eye at the combined 18th EURETINA Congress and 36th Congress of the ESCRS in Vienna in September 2018.
“Diabetes mellitus, even in the absence of diabetic retinopathy or pre-existing DME, is the most significant risk factor for postoperative macular oedema,” said Dr la Cour. The risk of postoperative diabetic macular oedema (pDME) is 1.8 times higher after cataract surgery in diabetics, and increases with the severity of the diabetic retinopathy. This risk increases with longer duration of diabetes and poorer metabolic control.
As ophthalmologists, we have a very limited role in the management of the diabetes itself. However, there are several things that we can do to optimise surgical outcomes.
“Before referring my diabetic patients for cataract surgery, I make sure that the retinal situation is as good as it can possibly be,” says Julie De Zaeytijd, a medical retina specialist at Ghent University Hospital in Belgium. She tailors the treatment plan to each individual patient depending on their prior history and the current situation.
“In diabetic patients with no prior history of DME, the preoperative preparation does not differ from that of non-diabetic patients: preoperative NSAID drops suffice,” says Dr De Zaeytijd. Perioperative topical NSAID is superior to topical steroid monotherapy in the prevention of postoperative CME in both diabetics and non-diabetics, so NSAID prophylaxis should thus be used in all diabetics.
However, pre-existing DME should be treated prior to performing cataract surgery. “If the patient is already suffering from DME, I prescribe three monthly anti-VEGF injections. I then plan the phaco one week after the last injection and pre-plan an appointment to see my patient three weeks after surgery,” she says.
What about patients with a history of DME but whose foveas are currently ‘dry’ when cataract surgery is planned? “These patients receive an anti-VEGF injection one week prior to cataract surgery,” she says, the timing of which her administrative staff coordinates with the surgeon’s planning team.
The same thing goes for patients with proliferative diabetic retinopathy (PDR) and a fundus that is difficult to visualise due to advanced cataract. “A preoperative anti-VEGF decreases the chances of haemorrhage and it buys us a bit of time until laser can be performed two weeks after surgery,” she said. It is useful to note that there is no advantage of performing panretinal photocoagulation (PRP) prior to surgery. Further, preoperative PRP is often difficult due to lens opacities.
Although standard surgical complications, such as capsular rupture, are not encountered more frequently in diabetic eyes, despite previous literature suggesting the opposite, some small adjustments might need to be made more frequently in diabetic eyes.
Thierry Derveaux, a cataract specialist at Ghent University Hospital, speaks from the surgeon’s point of view.
“In patients who have received intravitreal injections, we have to remember to be wary of occult lens touches or punctures of the posterior capsule. When in doubt, perform hydrodelineation rather than hydrodissection,” Dr Derveaux recommends, which will help avoid putting pressure on a posterior capsule that might be compromised.
“Preoperatively, it’s important to determine the maximum obtainable mydriasis. A pupil that doesn’t sufficiently dilate pharmacologically is not likely to respond to additional intracameral mydriatics, so be prepared to use devices such as iris retractors if necessary,” says Dr Derveaux.
In patients with diabetes, it’s very important that the retinal specialist can continue examining the retina for years after surgery. “In order to prevent anterior capsular phimosis, I enlarge my capsulorhexis if it is smaller than 5mm and carefully remove all lens epithelial cells from the anterior capsular rim to the equator,” he says. “And in cases of zonular weakness or large, stretched capsular bags, I have a low threshold to implant a capsular tension ring in an attempt to prevent phimosis,” although he adds that this is not necessarily supported by the literature.
As for postoperative care: “Whereas I generally only see my patients one day and one month post-op, I am more likely to see my diabetic patients one week after surgery and will exchange the topical NSAID for preservative-free artificial tears if the corneal epithelium is suffering,” he says. OCTs are performed at one month and two months post-op to detect the occurrence or recurrence of macular oedema.
Close collaboration between the doctor treating the diabetic macular oedema or diabetic retinopathy are paramount, and both communication and advanced planning are crucial.
“I make every effort to streamline everything during the perioperative period, which includes making the surgeon’s life as easy as possible so (s)he doesn’t have to think about what has to happen a few weeks after surgery,” said Dr De Zaeytijd. This includes writing her preferred treatment plan in the patient’s chart and working closely with her support staff to make sure post-op appointments are already made before referral to the surgeon.
Despite the increased risks encountered in patients with diabetes, most studies agree that cataract extraction results in visual improvement in the clear majority of diabetics with modern minimally invasive cataract surgery.