Weak zonules surgery requires slow and gentle approach

Bekir Sitki Aslan MD

In eyes with weak zonules, cataract surgery requires a slow and gentle approach with additional support for the capsule throughout the procedure, said Bekir Sitki Aslan MD, Liv Ankara Hospital, Ankara, Turkey.

“Weak zonules present a real challenge to the cataract surgeon, and careful planning and intraoperative care are required to increase the margin of safety in these potentially complex procedures,” he told the 19th ESCRS Winter Meeting in Istanbul.

When assessing an eye’s zonular integrity prior to cataract surgery, the first step is to review the patient’s history for risk factors, such as trauma, pseudoexfoliation syndrome, and Marfan’s syndrome. Eyes that have undergone previous intraocular surgery and highly myopic eyes are also prone to weak zonules.

Signs to look for under the slit-lamp include phacodonesis or other abnormal position of the lens and a red reflex beyond the lens periphery. When performing a capsulorhexis, difficulty with incising the capsule, because of a tendency for the capsular bag to be pulled along with the tear, is another sign of a weak zonule.

If the equator of the lens capsule is flat at the zonulolysis area, it is a sign of local zonular weakness which will not continue to extend after the surgery. However, if the equoatorial edge of the zonular weakness becomes rounder it is a sign of generalised and severe zonular weakness and zonular breakdown will continue after the surgery.

Dr Aslan noted that providing support to the capsule during cataract surgery is essential in eyes with zonular deficiencies. The two most commonly used tools for that purpose are iris hooks and capsular hooks. The capsular hooks differ from iris hooks in that they reach farther inside the capsule and can therefore provide a better stabilization of the lens with less likelihood of trauma to the capsule than is the case with the shorter iris hooks.

Capsular tension rings are another tool for stabilising the capsular bag. However, they are best placed after phacoemulsification is complete, otherwise they will make cortical clean-up very difficult. The devices have several diameters, one should calculate the size of the ring to use in a particular eye by adding 1.0mm to its white-to-white measurements. For eyes with very poor zonular integrity, there are capsular rings like the Cionni rings and the Malyugin ring that have eyelets for fixation to the sclera.

During phacoemulsification, it is best to lower the fluidic settings and perform a thorough viscodissection with a dispersive viscoelastic, he said. That will relieve the zonular capsular tension and torsion and provide adequate access to the cortex without endangering the capsule. To reduce postoperative capsular contraction and capsular phimosis, Dr Aslan recommended using a three-piece hydrophobic IOL with stiff broad haptics. One technique he has found particularly useful is to place the haptics in the sulcus and capture the optic in the capsular bag, he said.

Bekir Sitki Aslan: bsa@outlook.com