Posterior Capsular Rent

A posterior capsular break is a complication that may occur in the best of hands during cataract surgery—both in the phacoemulsification and extracapsular cataract extraction stages. Varying incidence ranging from 0.2% to 14% has been reported depending on factors such as systemic, orbital, and ocular characteristics of the patient, type of cataract, experience of the surgeon, and the available operating facilities. Vitreous loss may occur in up to 5% of cases. Improper management of the posterior capsular rent (PCR) can lead to further complications and less than desirable visual results. RISK FACTORS Systemic risk factors for PCR include a short neck, obesity, inability to cooperate or lie still, dementia, old age, respiratory difficulty, and use of systemic drugs such as tamsulosin. A poorly positioned patient with chin turned downwards and iris not parallel to the floor can result in a poor red reflex, as can a contralateral tilt to the head or a deep-set eye, which can result in pooling of fluid and disturbing light reflexes. A patient lying low on the trolley makes the surgeon lean forward to operate with resultant discomfort and difficulty during surgery. Likewise, a poorly placed drape obstructs a clear view. Excess fluid in the fluid collection bag, a tight speculum, a tight/shallow orbit (either anatomical or secondary to retro), or peribulbar injection can lead to increased vitreous pressure, causing the posterior capsule to bulge forward and increase the risk for PCR. Deep-set eyes, prominent nose and brows, small palpebral aperture, and strong Bell’s phenomenon cause difficulty in manoeuvring instruments. Ocular conditions can increase the risk of PCR. This includes a shallow or deep anterior chamber, low scleral rigidity, vitrectomised eye, high myopia, liquefied vitreous, weak zonules, a floppy bag, small pupil, and pseudoexfoliation. Media opacities such as post-anaesthetic epithelial haze, corneal scars, asteroid hyalosis, or vitreous haemorrhage can all increase PCR risk. The type of cataract also affects the incidence of PCR: for instance, posterior polar cataracts, white or hard brown cataracts, intumescent cataracts, and traumatic or paediatric cataracts all have a higher risk. Poor quality of instruments, machines, or the operating microscope; machine malfunction; and inexperienced persons assisting or adjusting machine parameters/tubing can also affect the incidence of PCR. Finally, surgeon experience also affects the rate with a higher risk earlier in the learning curve. Improper surgical technique for almost any step can lead to a cascading effect in increasing the difficulty of surgery, ultimately culminating in a PCR or other complications if not managed appropriately. A poorly constructed wound can result in ante LEGEND FOR FIGURE: IOL scaffold technique: A) Intravitreal triamcinolone acetonide is used to stain vitreous. Vitrectomy performed. B) A three-piece IOL is injected under the nuclear fragments. C) Phacoemulsification with the IOL acting as a scaffold. D) Pars plana vitrectomy is performed for any residual vitreous prolapse and aspirating residual cortex by alternating between cut and aspirate modes. The IOL is then transferred to the sulcus.37 rior chamber shallowing, iris prolapse, intraoperative pupillary constriction, iris trauma, and difficult surgery. Similarly, a small rhexis can cause capsular blowout, difficult nucleus, and cortex management in addition to risking rhexis and PC tears. Uncontrolled movements of the phaco probe, poor foot-pedal control, mismatch between fluid inflow and outflow, post-occlusion surge, going too close to the anterior or posterior capsule, and accidental purchase of capsule by the phaco or irrigation/aspiration (I/A) probe are some other causes for PCR. IMMEDIATE RESPONSE TO A PCR The first thing to not do is to pull out the phaco or I/A probe, as this disturbs the intraocular pressure equilibrium, causing the PCR to enlarge and the vitreous to prolapse out. The surgeon should instead remain in foot position one and inject dispersive viscoelastic through the side port with the non-dominant hand while holding the dominant hand steady. Once the dispersive viscoelastic tamponades the break, stabilizes any remnant nuclear fragments, and fills the AC, the probe may gently be withdrawn. The next step is to analyse the situation, as further management depends on when the PCR occurred, the surgeon’s experience in managing such situations, the availability of required machines and instruments, and the presence of vitreoretinal backup. STAGE AT WHICH PCR OCCURS PCR most commonly occurs towards the end of phacoemulsification—while removing the last nuclear fragment, during cortex aspiration, or polishing the PC. PCR during hydrodissection can result in the entire nucleus sinking. Posterior polar cataracts with inherent weakness in the PC are especially predisposed to this. Post-traumatic cataracts, post-vitrectomised eyes, or eyes with a history of intravitreal injections may have unnoticed/iatrogenic posterior capsular breaks that may extend to sudden increase in pressure from the hydrodissection wave. Very small incisions, high viscosity, viscoelastic blocking egress of fluid, mature cataracts that fill the entire capsular bag, a small rhexis, rapid hydrodissection, or sudden use of large volume of fluid can cause the nucleus to float up against the anterior capsular rim. This creates a seal, which causes an accumulation of fluid within the capsular bag that ultimately leads to capsular block syndrome (CBS) and PC blowout. Multiple gentle injections of small volumes of fluid, tapping the nucleus gently to break the seal and allow entrapped fluid to escape, and depressing the posterior lip of the incision are manoeuvres that allow excess fluid to exit. This is also important in myopic eyes, microincision coaxial phaco, and bimanual phaco, where the incisions are smaller. Femtosecond laser-assisted cataract surgery (FLACS) creates gas bubbles within the lens, which, unless released, add to the intralenticular pressure during hydrodissection, risking CBS and capsular blowout. Attempts at nucleus rotation in the presence of a compromised capsule can also result in nucleus drop. If the PCR involves retained nuclear fragments without vitreous loss, the management depends on the size and hardness of the remaining nucleus. A large nucleus or hard fragment can be brought out after conversion to extra-capsular cataract surgery. A small fragment or a soft nucleus may be emulsified within the anterior chamber, taking care to avoid chamber fluctuations and vitreous prolapse by using dispersive viscoelastic and slow-motion phacoemulsification. The IOL scaffold technique described by Agarwal et al. can be used where a foldable IOL is pre-placed within the AC—over the iris and under the nuclear fragments so the IOL haptic occludes the pupil and prevents fragment drop, vitreous prolapse, or PCR enlargement. To be continued in next issue. Dr Soosan Jacob is Director and Chief of Dr Agarwal’s Refractive and Cornea Foundation at Dr Agarwal’s Eye Hospital, Chennai, India, and can be reached at dr_soosanj@hotmail.com. EVERYTHING YOU ALWAYS WANTED TO KNOW ABOUT....

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