Preparation is key in managing difficult glaucoma cases

Phacoemulsification in patients who have undergone previous filtration surgery can cause long-lasting increases in intraocular pressure (IOP), but expert surgical technique can help minimise that effect, said Carlo E Traverso MD, PhD at the XXXIII Congress of the ESCRS in Barcelona, Spain.

“Glaucoma specialists are qualified for difficult phacoemulsification surgery, and glaucoma patients with cataracts can often be very challenging. Modern small-incision phacoemulsification has greatly improved our management of these difficult cases, although specific skills are still required,” said Prof Traverso, University of Genoa, Italy.

He noted that filtration surgery unquestionably increases the likelihood of patients developing cataracts in the short to medium term. Phacoemulsification often reduces IOP to normal levels in virgin eyes with angle-closure glaucoma and also tends to lower IOP slightly but significantly in unoperated eyes with primary open-angle glaucoma (POAG). Several studies showed that phacoemulsification in patients who have undergone previous filtration surgery results in a small increase of average IOP, which can be significant in some individuals.

“This is one of the problems with cataract surgery in these patients, the long-term increase of IOP in patients that have been stable after filtration surgery,” Prof Traverso said.

ELEVATED IOP AND DEFLATED BLEBS

As an example, he cited a fairly recent retrospective controlled study which showed that, in 50 POAG patients who underwent cataract surgery after having undergone a successful trabeculectomy, there was a significantly greater increase in IOP throughout 18 months of follow-up than there was in 72 POAG patients who underwent trabeculectomy alone. Both groups underwent trabeculectomy a mean of 20 months prior to the study period (Salaga-Pylak et al, BMC Opthalmol 2013;13:17).

He noted that among those who underwent phacoemulsification after having previously undergone trabeculectomy, the mean IOP was 13.2mmHg at 18 months follow-up, compared to 11.6mmHg prior to the cataract procedure. Among those who underwent trabeculectomy alone, mean IOP remained stable throughout the study period, increasing only slightly from 11.0mmHg, preoperatively, to 11.5mmHg at 18 months.

Furthermore, there was an increase in IOP in 70 per cent of those in the phacoemulsification group, compared to only 36 per cent of those in the trabeculectomy alone group. IOP remained stable in 49 per cent of patients who underwent trabeculectomy alone, compared to 12 per cent of those who underwent subsequent phacoemulsification.

In addition, IOP increased by more than 2.0mmHg in half of the patients in the phacoemulsification group, compared to only a sixth of those in the trabeculectomy alone group. Conversely, IOP decreased by more than 2.0mmHg in slightly over a third of those in the trabeculectomy alone group, compared to only a ninth of those who underwent phacoemulsification afterwards.

The study’s authors noted that patients in the phacoemulsification group had statistically significant reductions in the surface area and height of their blebs following the cataract procedure, whereas the blebs of those who underwent trabeculectomy alone had no statistically significant changes in surface area or height.

Prof Traverso suggested that it is likely that the inflammation resulting from cataract surgery plays a role in the increase in IOP and changes in bleb morphology that occur after the procedure in eyes with previous trabeculectomies. He pointed out that the functionality of a bleb depends almost exclusively on the integrity of the sclerostomy and on the efficiency of subconjunctival diffusion of fluid, both of which may be impaired by inflammation.

SURGICAL PEARLS

When performing phacoemulsification after filtration surgery it is important to remember that such patients are not routine cases, but can be difficult and challenging and frequently require very complex and specific technique.

“To younger and less experienced colleagues I suggest not to venture into this type of surgery unless you feel your training and experience are adequate, and perhaps refer the case to a more experienced surgeon, or do it together with such a colleague,” Prof Traverso said.

He added that preparation is the key to a successful outcome in unusual cases, and all the tools that might be needed to deal with the expected and unexpected difficulties that one might encounter should be made available and planned for.

Such tools include iris hooks or pupillary expansion rings, for eyes with poor mydriasis and/or floppy iris, and capsular tension rings or segments, for eyes with weakened zonules. He added that trypan blue is often useful for optimal visualisation when performing the capsulorhexis in such cases.

Prof Traverso noted that the IOP of the patient undergoing the procedure should be brought to normal or below normal levels at the time of surgery. Mannitol is better than Diamox for that purpose. In addition, gentle globe compression should be used to avoid further damage to the optic nerve. The choice of anaesthesia used – local, peribulbar or sub-Tenon’s – should be based on what the surgeon finds most appropriate for a particular case.

Carlo E Traverso: mc8620@mclink.it