Zonulopathy is a condition where zonular support for the lens capsule is lacking as a result of zonular dialysis or weakness. The condition may include lens subluxation or dislocation. A cataract surgeon needs to consider zonulopathy because it can impede successful outcomes. Creating a continuous curvilinear capsulorhexis (CCC) can be quite challenging if zonulopathy is present. Likewise, with zonulopathy, intraocular lens (IOL) implantation and lens fragmentation can make cataract surgery more challenging.
Cataract surgery planning must, therefore, involve detection of zonulopathy to enable the surgeon to plan reasonably, including which tools to use. Diagnosing zonulopathy on ultrasound biomicroscopy, slit lamp exam, or anterior segment optical coherence tomography is often inconclusive. The surgeon will usually encounter zonulopathy at the beginning of surgery. If zonulopathy is not well-handled during surgery, cataract extraction can lead to further zonular damage.
Therefore, the surgeon must adopt a cataract surgical approach based on the degree of zonulopathy present. S/he must be conversant with whether zonulopathy in the patient is segmental (caused by trauma) or diffuse (associated with various diseases). The goal of surgery is to ensure the integrity of the remaining zonular fibers is preserved to stabilize the lens capsule for better long-term visual outcomes.
Also Known As
- Zonular dialysis
- Zonular dehiscence
- Diffuse zonulopathy
- Segmental zonulopathy (traumatic or iatrogenic)
Causes & Risk Factors
Causes and risk factors of zonulopathy may include:
- Advanced age
- External trauma
- Extreme myopia
- Retinitis pigmentosa
- Intraocular neoplasm
- Ultra-brunescent cataracts
- Previous cataract extraction
- Pseudoexfoliation syndrome
- Repeat intravitreal injections
- Previous pars plana vitrectomy
- Congenital or systemic conditions like Marfan syndrome, Rieger syndrome, homocystinuria, Crouzon syndrome, Weil-Marchesani syndrome, retinopathy of prematurity, retinitis pigmentosa, and Ehlers Danlos syndrome
Signs & Symptoms
Signs and symptoms may include:
- Poor mydriasis
- Decentered nucleus
- Traumatic mydriasis
- Smaller pupils (advanced zonulopathy)
- Spaces between the anterior lens surface and iris
- Iridodonesis (vibration of the iris with eye movement)
- Shallow anterior chamber (despite a normal axial length)
- Glaucoma (it may be an indication of zonular deficiency)
- Iridodialysis (traumatic separation of iris from ciliary body)
- Brunescent nucleus (nucleus that has turned hard and brown)
- Vitreous herniation (vitreous protrudes into the anterior chamber)
- Pseudoexfoliation characterized by white-like deposits on the zonules, pupillary margin, and the posterior iris surface
- Lens malposition (subluxation or dislocation), leading to fluctuations in vision. Primary symptoms may include distortion of vision, monocular diplopia, or blurry vision
A patient’s medical history is essential because it can direct the eye doctor to findings not easily seen in physical examinations. Systemic disorder or trauma history needs disclosure before cataract surgery.
A physical examination is performed and may include:
- Visual acuity (clarity of vision)
- Objective and manifest refraction
- Focused slit-lamp examination paying particular attention to lenticular malposition or centration. The eye doctor determines how severe the dehiscence is
Treatment is aimed at preserving the integrity of the remaining zonular fibers so that they can support the lens capsule during cataract surgery. There are many surgical options open to the cataract surgeon.
In creating a CCC, there may be difficulties initiating a capsular tear. Hence, the surgeon directs shearing force toward the zonulopathy area to create counter-forces in areas where the zonules are intact. A rhexis may tear out; thus, the surgeon will use viscoelastic to counterbalance outward forces on the anterior capsule.
Hydrodissection and rotation
The procedure aims to mobilize the lens inside the capsular bag to minimize zonular fiber stress when the surgeon rotates the lens and disassembles the nucleus. To make lens rotation easier in the event of zonular weakness, the surgeon can use a bimanual technique to reduce the force placed on the capsule.
The surgeon can use the ‘cross chop’ and ‘double-chop’ techniques to divide and remove the lens in nuclear fragmentation and phacoemulsification. These methods minimize the stress on the zonules.
In older patients with zonular dialysis and severe diffuse zonular laxity, 'central cortical cleanup' can be used. The surgeon leaves a central clear visual axis and a peripheral without stress. A bimanual technique that elevates the central cortical fibers and aspirates them towards the periphery can also help preserve zonular fibers.
The surgeon inserts the retractors through limbal incisions to minimize anterior iris' tenting. The hooks help to reduce cataract surgery complications caused by an unstable capsular bag.
Capsular Tension Ring
The surgeon can use a capsular tension ring (CTR) to support zonular laxity areas and maintain the shape of the bag or zonular integrity. The timing of the CTR is essential because early implantation may cause significant zonular stress. The 'fishtail,' suture-guided CTR placement,' and 'fishtail on a line' techniques can be used to minimize stress on the zonules.
Sometimes early CTR implantation is necessary, which can compromise zonular integrity. Henderson CTR uses scalloped depressions to assist with the removal of lens fragments.
Cionni Ring – Modified CTR
Scleral fixation is used to stabilize the capsular bag orientation and location. The surgeon secures the Cionni ring to the scleral wall without compromising the capsular bag . The ring provides both scleral fixation and capsular support at a go.
Capsular tension segments
The surgeon inserts the capsular tension segment (CTS) into the capsular bags for support before lens removal.
The Hoffman Pocket technique improves zonular support, reduces the risk of suture exposure, and aids in rapid healing and postoperative comfort.
Femtosecond laser-assisted cataract surgery
A femtosecond laser can be used to treat lens subluxation or zonulopathy and offer zonular support.
Prognosis & Long-Term Outlook
Skilled and experienced surgeons often help reduce stress on the zonules and enable successful cataract processes like lens fragmentation and CCC creation. Surgery to minimize zonular stress helps with successful IOL implantation.
Prevention & Follow Up
Patients can be followed up for three years or more to ensure the capsule has not collapsed and that the cataract removal procedure was successful.