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Up Front | Mar 2008

Posterior Polar Cataract and Preexisting Posterior Capsule Defect

A clear understanding of phacodynamics helped to maintain an intact anterior vitreous face in this challenging case.

Posterior polar cataract(PPDC) is a dense white opacity situated on the central posterior capsule that consists of characteristic concentric rings around a central opacity, giving it a bull's-eye pattern (Figure 1). Formerly, the reported incidence1,2 of posterior capsule rupture (PCR) during surgery in eyes with posterior polar cataract was between 26% and 36%. In recent literature,3,4 the incidence of PCR is between 7% and 11%. Spontaneous PCR with dislocation of the nucleus in the vitreous cavity of an eye with a posterior polar cataract was previously reported.5

We present a case of preexisting PCR with an intact anterior vitreous face (Figure 2) in the left eye of a 35-year-old male. An oblong defect was located in the central region of the posterior capsule; the ends of the defect tapered peripherally but remained wide at the equator. The patient's right eye had complicated aphakia following cataract surgery. The case record revealed the diagnosis of bilateral posterior polar cataract. The left eye, with preexisting posterior capsule defect, was treated with phacoemulsification and in-the-bag IOL implantation. The surgical strategies used to prevent a dropped nucleus and maintain the integrity of the anterior vitreous face are described below.

Incision. Two paracentesis incisions were created with an angled dual-bevel knife (Alcon Laboratories, Inc., Fort Worth, Texas). Initially, Viscoat was injected into the eye followed by Provisc (both manufactured by Alcon Laboratories, Inc.).6 Care was taken not to inject excessive viscoelastic into the anterior chamber because if too much is injected, a sudden posterior capsule blowout may occur.7 Use of a cohesive viscoelastic in the anterior chamber prevents chamber collapse and forward movement of the iris-lens diaphragm during surgical entry into the eye. Subsequently, a temporal corneal single-plane incision of 2.6 mm was performed.

Capsulorrhexis. A capsulorrhexis was created of approximately 5 mm diameter. In cases where the nucleus must be prolapsed into the anterior chamber, a larger opening may not provide adequate support for a sulcus-fixated IOL if the anterior vitreous face is compromised.8

Inside-out delineation. A central trench was sculpted using the slow-motion technique9 with the Infiniti Phacoemulsifier (Alcon Laboratories, Inc.). The preset parameters were as follows: 30% ultrasound energy with a burst width of 5 milliseconds, 80 mm Hg vacuum, 16 cc/min aspiration flow rate, and 80 cm bottle height. Care was taken not to mechanically rock the lens. It was sculpted until the central opacity was exposed. Viscoat, a dispersive viscoelastic, was injected through the sideport before retracting the probe to avoid forward movement of the iris-lens diaphragm (Figure 3). A specially designed right-angle cannula, mounted on a 2-cc syringe filled with fluid, was then introduced through the main incision, and the tip was placed at an appropriate depth adjacent to the right wall of the trench. The syringe penetrated the central lens substance (Figure 4); fluid was injected through the right wall of the trench. Delineation was produced when the fluid traversed in the inside-out direction,10 and the presence of a gold ring within the lens was evidence of successful delineation (Figure 5). Fluid injection was repeated in the left wall of the trench (Figure 6). The delineation demarcated the nucleus from the epinucleus and created an epinucleus shell. Rotation of the nucleus was avoided.2

Nucleus removal. The nucleus was aspirated within the epinucleus shell using 30% ultrasound energy, a burst width of 5 milliseconds, 120 mm Hg vacuum, 16 cc/min aspiration flow rate, and 50 cm initial bottle height, which was later raised to a maximum of 80 cm (Figure 7).

Epinucleus removal. To begin, the distal epinucleus was stripped with the probe, leaving the central area attached2,7,11 (Figure 8). Before withdrawing the phaco probe, Viscoat was injected through the sideport. Next, the proximal epinucleus (ie, subincisional epinucleus) was mobilized by performing gentle and focal multiquadrant hydrodissection with a right-angle cannula facing right and left (Figure 9). Subsequently, the peripheral epinucleus and cortex were aspirated with bimanual automated I/A handpieces using an aspiration flow rate of 20 cc/min and a vacuum of 650 mm Hg. The initial bottle height (60 cm) was gradually increased to 80 cm. The handpieces were swapped, and the central area was lifted at the end. The central opacity was revealed as a thick, opaque plaque with the classic appearance of a defect in the posterior cortex at the site of the posterior polar cataract (Figure 10). Viscoat was injected through the paracentesis over the posterior capsule defect to tamponade the anterior vitreous face. The anterior chamber was then filled with Provisc. There was no peaking or distortion of the posterior capsule defect margins, thus indicating no disruption of the anterior vitreous face12 (Figure 11). Last, the central portion of the posterior capsule leaflets, within the visual axis, was removed (Figure 12).

IOL implantation. The sides of the main incision were marginally extended to prevent any undesirable globe deformation during IOL implantation. A one-piece AcrySof IOL (6-mm optic using 13-mm overall diameter) was implanted in the bag through the Monarch (Figure 13) injector system (both manufactured by Alcon Laboratories, Inc.). The trailing haptic was deposited in the bag with a Lester manipulator instead of being dialed into the bag. The main incision and the paracentesis were subsequently sutured.

Viscoelastic removal. The residual viscoelastic was removed with bimanual automated I/A handpieces. No attempt was made to remove the viscoelastic from behind the IOL. The main incision and the paracentesis were sealed by hydrating the corneal stroma13 (Figure 14). The pupil was constricted with intracameral pilocarpine at the end of the surgery

Follow-up. The IOL remained stable during subsequent follow-ups (Figure 15). Periodic evaluation was carried out over 3 years; no intraocular pressure rise, retinal break, or cystoid macular edema were discovered.

Phacoemulsification, more specifically slow-motion phacoemulsification as recommended by Robert H. Osher, MD, of Cincinnati, Ohio, facilitated a closed-chamber technique. Slow-motion phaco features low aspiration flow rate, vacuum, and infusion pressure to prevent PCR.9 We advocate the use of inside-out delineation instead of cortical cleaving hydrodissection14 or conventional delineation,15 as cortical cleaving hydrodissection may lead to hydraulic rupture.1,2 With conventional delineation, fluid may inadvertently be injected into the subcapsular plane, leading to unwarranted hydrodissection. Inside-out delineation can precisely delineate the central core of the nucleus.

The creation of a trench to perform inside-out delineation allows precise injection of the fluid within the central core of the nucleus. Fluid was injected at a desired depth, under direct vision, and therefore an epinucleus cushion of desired thickness could be achieved (Figure 7). This tactic provided a precise epinucleus bowl that acted as a mechanical cushion, protecting the posterior capsule during subsequent maneuvers. Inside-out delineation is easy to perform, provides superior control, reduces stress to the zonules, and precisely demarcates the central core of the nucleus.

Slow-motion phacoemulsification reduces turbulence in the anterior chamber. The contours of the cornea and globe were maintained throughout the procedure by injecting viscoelastic before withdrawing the probe. This prevented anterior chamber collapse and a forward bulge of iris lens diaphragm.16

If multiquadrant, focal, cortical cleaving hydrodissection is done after the nucleus is aspirated, it does not threaten the compromised integrity of the posterior capsule, as the capsular bag is not fully occupied. Therefore, the build-up of hydraulic pressure is not sufficient to blow out the posterior capsule. When separate paracentesis incisions are used to carry out irrigation and aspiration for epinucleus and cortex removal, it ensures anterior chamber maintenance and aids in complete cortex removal.

The liberal use of Viscoat in the anterior chamber tamponades the anterior vitreous face and compartmentalizes the posterior segment from the anterior maneuvers. The use of an AcrySof IOL is recommended because it unfolds gently in the eye and therefore does not extend the tear.

These surgical strategies, the availability of modern instrumentation and devices, a better understanding of phacodynamics, and our cumulative surgical experience have enabled the maintenance of an intact anterior vitreous face in an eye with posterior polar cataract and preexisting posterior capsule defect.

Abhay R. Vasavada, M, FRCS, is the Director of the Iladevi Cataract & IOL Research Centre, Raghudeep Eye Clinic, India. Dr. Vasavada states that he has no financial interest in the companies or products mentioned. He may be reached at tel: +91 79 27492303; fax: +91 79 27411200; or icirc@abhayvasavada.com.

Shetal M. Raj, MS, is a consultant at the Iladevi Cataract & IOL Research Centre, Raghudeep Eye Clinic, India. Dr. Raj states that she has no financial interest in the companies or products mentioned. She may be reached at tel: +91 79 27492303; fax: +91 79 27411200.