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Cataract Surgery | Apr 2014

Mature Cataracts

Surgery in these eyes is less than routine.

A mature cataract is opaque, whether white (Figure 1) or brunescent, and, therefore, has complete absence of red reflex. This is not the only challenging characteristic of mature cataracts, however, and trap doors lurk in every step of cataract surgery in these eyes.

Removal of a mature cataract is challenging, regardless of its etiology. Although maturity typically develops over a long duration, cataracts can harden in as few as 2 to 3 days following trauma. A rare and spectacular occurence is the development of an opaque cataract within 48 hours after a very high glucose level in a patient with diabetes. This is the consequence of glucose entering the lens and converting to sorbitol, which cannot be metabolized. Once the osmotic gradient results in water influx, the lens opacifies and swells. In these and other cases, mature cataracts can become intumescent.

The term hypermature applies when cortical material leaks through the capsule, leaving the lens wrinkled and shrunken. The danger with hypermature cataracts is the risk for phacolytic glaucoma. Further liquefaction of the cortex may allow movement of the nucleus within the capsular bag, known as a morgagnian cataract. Complicated hypermature cataracts can eventually calcify.

PREOPERATIVE ASSESSMENT

A mature cataract imposes significant challenges during the surgical course. Therefore, preoperative assessment is not only crucial but is more demanding than for a routine procedure.

First, patients whose vitreous cavity and posterior pole cannot be viewed should undergo B-scan ultrasonography in order to rule out intraocular pathology such as vitreous organization, retinal detachment, and tumors (Figures 2 and 3). If the B-scan is normal and the patient can localize light with the eye, surgery will most likely result in a return of visual function. When performed by experts, electrophysiology can also reinforce the prognosis for recuperation.

Partial coherence interferometry with the IOLMaster (Carl Zeiss Meditec) or the Lenstar (Haag-Streit) does not provide an accurate IOL power in the presence of an opaque cataract. Instead, ultrasound axial length measurement, either contact or immersion, should be performed. Contact with the A-scan probe can slightly reduce the axial length; immersion avoids this drawback.

SURGICAL STEPS

Anesthesia. I have abandoned periocular injections, and in routine cataract surgery I prefer topical and intracameral anesthesia. In a one-eyed patient with an intumescent mature cataract, however, I resort to general anesthesia.

Incisions. Formation of the main and sideport incisions can be done using the surgeon’s routine preferences.

Capsular staining. Because mature, rock-hard, white or brunescent cataracts present with no red reflex under coaxial illumination of the operating microscope, the capsule must be stained to facilitate performing the capsulorrhexis. Trypan blue is currently my dye of choice, injected under an air bubble (Figure 4). First, to prevent the air from escaping, an ophthalmic viscosurgical device (OVD) is placed in the incision, and then a few drops of dye are injected onto the capsule. More OVD is then injected to spread the trypan blue dye, ensuring that it comes in contact with the entire capsular surface. In white cataracts with possible intumescence, extra OVD can be helpful to reduce the risk for what is called the Argentinian flag sign, capsulorrhexis tear extends toward the equator, forming a white stripe (the visible cataract) in a field of blue (the stained capsule), like the flag. This complication can become dramatic if the tear extends to the posterior posterior capsule, allowing the nucleus to fall into the vitreous cavity.

Capsulorrhexis. In white mature cataracts, the capsule can be brittle. This fragility is accentuated by the trypan blue dye. Moreover, the milky cortex may be under pressure. Therefore, opening the capsule must be done progressively, under counterpressure from a strong OVD. First, a small central puncture is performed with a 30-gauge needle; this frequently releases a smoke-like wave of liquefied cortex. Injection of additional OVD can be helpful to express and clear this milky material and to avoid extension of the puncture. Second, the capsulorrhexis is created with forceps. Because there is no intumescence in a brunescent mature cataract, the capsulorrhexis is less delicate.

Both white and brunescent cataracts require a large capsulorrhexis because the capsule and zonules are fragile. Additionally, maneuvers with the phaco probe are less dangerous when the capsulorrhexis is between 5 and 6 mm. To get a rhexis close to the zonular insertion in a capsule lacking elasticity and with possible zonular weakness, the surgeon must regrasp the capsular edge more frequently than is his or her habit in nonmature cataracts.

Hydrodissection. In the presence of a mature cataract, the fluid wave usually seen behind the nucleus in hydrodissection is not visualized, and the capsule is fragile, necessitating care. On the plus side, the attachment of cortex to the capsule is often weak. One should first try to rotate the nucleus without hydrodissection. If this is unsuccesful, cautious hydrodissection is the safest approach.

Phacoemulsification. It is not necessary to change one’s preferred phaco technique (eg, divide-and-conquer, phaco chop) in these eyes. However, phacoemulsification should be performed slowly and with low parameters. Supracapsular phacoemulsification or phacoemulsification in the anterior chamber with several additional injections of OVD may be the most prudent procedure if capsular or zonular damage is observed. Whatever the technique, start with the lowest settings possible and adapt the power, flow, vacuum, and bottle height to the eye’s behavior.

Despite the obvious disadvantages, converting to manual extracapsular cataract extraction is an option for a rock-hard nucleus and in eyes with concomitant cornea guttata.

Cortex removal. Most mature cataracts do not have much cortex. But be aware that, during phacoemulsification, the protective layer that normally lies between the nucleus and the capsule is reduced. This is another reason to elevate the nucleus away from the posterior capsule during phacoemulsification.

IOL implantation. The surgeon’s usual IOL choice, implanted in the capsular bag, is adequate for mature cataracts. Because of the need for a large capsulorrhexis, however, IOLs with C-loop haptic designs, with their dual optic-haptic junctions, create an axis of tilt and have a tendency for partial optic capture in the capsulorrhexis (Figure 5). Generally, 10º of tilt induces around 0.75 D of astigmatism. This drawback may be avoided by choosing IOLs with a four-loop haptic design (Figure 6).

OVD removal. I call this step visco and bugs removal because contamination from the eye flora is common. OVD must be completely removed, especially as more than usual is used in these eyes and surgical time is relatively long.

CONCLUSION

To date, I have not used femtosecond laser technology for mature cataracts. Issues including capsulotomy tags, loss of mydriasis, and pressure in the capsular bag could make mature cataracts more challenging. However, time will tell if this new technology is advantageous for surgery in mature cataracts.

Regardless of the technique chosen, anterior segment surgery remains an enormous responsibility, but good results are always possible (Figure 7).

Albert Galand, MD, PhD, is the former Head of the Ophthalmology Department, Hospital of the Université de Liège, Belgium, and is in practice at the Cataract Clinic in Neupré, Belgium. Professor Galand states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +32 497 089 064; e-mail: professeur. galand@gmail.com.

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