Cataract surgery more than meets front of the eye

By Roibeard O'hÉineacháin

NICE - Anterior segment surgeons should pay more attention to the posterior part of the eye, Philippe Sourdille MD told a clinical research sysmposium at the XX ESCRS Congress.

While most of the action in cataract surgery takes place in the anterior segment of the eye, the procedure can nonetheless have deleterious effects on the posterior segment, including the onset of macular oedema and accelerated macular degeneration, he noted.
Cataract surgery has the potential to induce changes in the eye which can have longstanding consequences, most of which occur in the posterior segment.

The invasive nature of the procedure means surgeons should consider the risk of altering the blood-ocular barriers in some way, which in some patients will lead to macular oedema, he noted.

Furthermore, unless special care is taken, the surgery can worsen pre-existing conditions such as age-related macular degeneration (AMD) and predisposing conditions (drusen) and diabetic retinopathy, he added.

One of the underestimated sequelae of cataract surgery is postoperative hypotony. While the condition is infrequent and generally short-lived, long-lasting hypotony could be responsible for macular folds.
It is always the result of high pressure changes during the operation which in turn causes an unnoticed cyclodialysis cleft, he noted.

"I think we should be aware especially in these times when we use both high quantities of serum in the anterior chamber and high vacuum that we may be more prone than before to inducing potentially clinically important pressure changes during the operation," Dr Sourdille said.

The treatment involves a transcleral suture of the ciliary body, a procedure which most ophthalmic surgeons can accomplish in a few minutes using topical anaesthesia.
In virtually all patients it results in total anatomical and functional resolution of the condition.

Retinal changes arising from the use of ocular hypotensive medication (Latanoprost) in the treatment of glaucoma and ocular hypertension is another factor cataract surgeons increasingly need to take into account.
Blood-retinal barrier ruptures occur in up to 6% of patients receiving such agents.

Several reports in the literature have shown that they occur more frequently in aphakic eyes than phakic eyes. Cataract might therefore also increase the risk.
"Blood-retinal barrier ruptures resolve after treatment interruption. It is therefore wise to do some laser flare cell measurements preoperatively in patients receiving long-term hypotensive therapy to detect flare elevation.

"Treatment should be stopped two weeks prior to the operation and patients should receive NSAIDs postoperatively. Such cases require a careful macular follow-up and patients should be given all the necessary information about their changing drug regimen," Dr Sourdille explained.

While most patients with AMD obtain an improvement in vision from cataract surgery, the procedure can actually increase the risk for the condition in some patients.
Furthermore, the increased light that reaches the retina may accelerate the disease, even in eyes with IOLs which have UV filters.

"This increased rate of macular degeneration together with an increased number of cataract operations might become a public health problem," he noted.
Patients at risk from developing AMD after cataract procedures generally have other predisposing factors, including drusen, increased autofluorescence of the retina and pigment accumulation.

There are also iatrogenic factors associated with the surgery itself that can increase the risk. They include surgically induced macular changes and CMO.
With regard to the IOLs themselves, additional filters may provide more protection against the acceleration of AMD.

In a study done by Kensaku Miyake MD in Japan, patients with yellow filters had significantly less AMD during a nine-year follow-up than those with no filters or those with conventional blue filters.

In patients with diabetic retinopathy there is the danger that the condition may change from the non-proliferative form to the proliferative form of the disease.
The risk is highest in insulin-treated patients and in those who have higher immunoglobulin levels and when CMO is present preoperatively.

Patients with diabetic retinopathy should therefore undergo special examinations such as preoperative angiography, laser treatment if needed and, if possible, laser flare cell measurements before the cataract operation.

"Retinal diabetic retinopathy and cataract means a combined operation. We should remember that combined operations require combined surgeons who are as skilled with vitreoretinal surgery as they are with cataract operations," he said.

A one-step operation - vitreoretinal and cataract - is safer than two successive procedures which increase the risk of retinal complications
Ophthalmologists currently have many ways available to them to monitor changes in the retina after cataract surgery. They include laser flare cell measurement, fluorescein angiography and nerve fibre analysers.

One of the more recently available technologies for the early detection of CMO is optical computerised tomography (OCT), which provides a reproducible and non-invasive way to measure changes in macular thickness.

In a study involving a consecutive series of cataract patients, Dr Sourdille and his associates were able to identify macular thickness changes, earlier with OCT than they were with fluorescein angiography.
OCT detected changes from a normal thickness of 160 microns to 400 microns and more. Such changes can give rise to CMO, he noted.
"This is a very elegant and clinical way to follow any modification of the blood-retinal barrier and of the macular thicknesses after operation.

"We were surprised that even after uncomplicated surgery, we still had 20% with macular thickness changes that correlate with published angiographic CMO levels after cataract operation," Dr Sourdille said.

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