© Springer India 2017
Arup Chakrabarti (ed.)Posterior Capsular Rent10.1007/978-81-322-3586-6_55. Surgical Pearls to Minimize the Incidence of Posterior Capsule Rent
(1)
Cornea, Cataract & Refractive Surgery Services, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, 110029, India
The lens capsule in human eyes has the maximum thickness in the anterior midperipheral region located just anterior to the site of insertion of the zonules. The capsule thickness increases with age, especially at the anterior pole, while it stabilizes in the midperipheral zone or slightly decreases after the seventh decade. From this point, the posterior capsule becomes progressively thinner and also diminishes with age, except for the thinnest, but stable posterior pole [1]. The posterior capsule acts as an anatomical barrier between the anterior and the posterior segment and limits the spread of infectious and inflammatory processes [2].
Posterior capsular rupture (PCR) is one of the most significant complications of cataract surgery [3]. It is imperative for every phacoemulsification surgeon to continuously assess the intraoperative situation to prevent PCR. The posterior capsule is usually difficult to visualize unless it is opacified. Timely recognition of PCR limits the extent of damage to the eye and increases the probability of implanting the intraocular lens (IOL) into the capsular bag. Apart from failure in implanting a posterior chamber IOL, the other complications that are associated with PCR include nucleus drop, vitreous loss with subsequently increased chances of retinal detachment, cystoid macular edema, wound leak and/or endophthalmitis if the vitreous wick keeps the wound open, progression of diabetic retinopathy, increased incidence of floaters, and migration of previously injected silicone oil into the anterior chamber. There is also an increased incidence of secondary glaucoma and endothelial decompensation, resulting in suboptimal visual outcomes [4–12].
The incidence of PCR ranges from 0.68 to 4.4 %, varying according to the type of cataract surgery and the surgeon experience [13, 14]. Narendran et al reported an overall 1.92 % rate of PCR or vitreous loss or both in an audit of 55,567 operations performed in the United Kingdom [15]. In another series of phacoemulsification performed in 500 eyes by the ophthalmology residents, 10.2 % developed vitreous loss, and 9.6 % developed posterior capsular rupture and vitreous loss [16]. The high incidence of PCR signifies a need to understand the factors responsible and devise necessary precautions to help prevent PCR.
5.1 Surgical Pearls to Minimize PCR
5.1.1 Comprehensive Preoperative Evaluation
5.1.1.1 History and Examination
A detailed ocular and systemic history is essential in each and every case. History of previous ocular trauma as well as any ocular surgery should be carefully documented. History of chronic usage of medications, both ocular as well as systemic should be elicited.
A thorough preoperative assessment of the eye to be operated as well as the fellow eye is a prerequisite before performing cataract surgery. This prepares the surgeon for any potential intraoperative complications including PCR. Standard preoperative cataract assessment includes a comprehensive slit-lamp examination to assess the ocular surface, corneal clarity, anterior chamber depth, pupillary dilation, anterior capsule characteristics, zonular complex stability, grade of nuclear sclerosis, and status of posterior capsule. Intraocular pressure should be measured. Further, specular microscopy to evaluate the endothelial cell count and posterior segment evaluation to rule out any vitreoretinal pathology should be done.
Examination of the fellow eye is imperative, especially if a cataract surgery has already been performed in that eye. Any signs of a complicated cataract surgery in the fellow eye may be an indicator of similar intraoperative challenges in the eye to be operated.
5.1.1.2 Identification of High-Risk Cases
Certain systemic and ocular factors may require special precautions and expertise for successful surgical outcomes without causing a PCR. The challenging surgical cases that are at an increased risk for intraoperative complications should be identified preoperatively for optimal results [17–20].
Systemic Risk Factors
A proper supine position of the patient is essential for performing a cataract surgery. Various systemic co-morbidities affecting the musculoskeletal system impede proper positioning of the patient for surgery. Cardiopulmonary diseases, associated with difficulty in breathing that is aggravated in a supine position, also pose problems. Neurological and mental disorders may be associated with involuntary movements and also affect patient cooperation. Obesity and short neck can produce increased vitreous pressure with subsequent instability of the anterior chamber. Patients with long-standing diabetes mellitus often have poor pupillary dilatation. Systemic medications such as alpha-blockers predispose the patient for the development of intraoperative floppy iris syndrome.
Ocular Risk Factors
Deep set eyes and narrow palpebral apertures pose difficulty during various steps of the surgery, starting from the placement of a speculum to achieving an adequate exposure during surgery. There is frequent pooling of fluid that influences visibility, and the surgical maneuverability is also impeded. Patients with meibomian gland dysfunction may have frothy lipid secretions that impede visualization during surgery. Coexistent ocular surface disease, corneal opacities and endothelial dystrophies are also associated with poor intraoperative visibility. Both a shallow anterior chamber as in angle-closure glaucoma and an excessively deep anterior chamber as in high myopia predispose toward an increased risk of PCR. A poorly dilating pupil and the presence of posterior synechiae need expertise for successful management. Cases with fibrotic anterior capsule, capsular plaques, and a breached anterior capsule also pose a surgical risk. Pediatric capsules have increased elasticity and pose a difficulty during capsulorhexis. Certain types of cataract such as a hypermature intumescent cataract, posterior polar cataract and advanced nuclear sclerosis may be difficult to manage and should be identified preoperatively. Laxity of zonules and broken zonules should be expected in cases with pseudoexfoliation, hypermature cataracts, posttraumatic cataracts, and subluxated lenses. Ocular comorbidities such as uveitis, previous ocular trauma, previous pars plana vitrectomy, and oil-filled eyes also pose a surgical challenge.
5.1.1.3 Documentation and Counseling
Preoperative documentation of all the examination findings as well as the presence of any ocular or systemic risk factors is vital to prevent surgical as well as legal complications. All suitable ocular investigations, such as specular count, anterior chamber depth, intraocular pressure, direct/indirect/90 D ophthalmoscopy, as well as macular function tests should be performed to ensure complete preoperative workup. All relevant systemic examinations should be concurrently performed before the patient is deemed fit for surgery.
Proper patient counseling is a must and a written informed consent should be obtained in all cases. In cases with coexistent ocular or systemic risk factors, patients should be informed of the increased risk of intraoperative complications.
5.1.2 Preoperative Preparation
5.1.2.1 Anesthesia
A proper selection of the type of anesthesia is a must to achieve a successful surgical outcome. Topical anesthesia is adequate for a majority of adult patients without any ocular or systemic comorbidity. The patient should be counseled preoperatively regarding the procedure and the need to fixate on the microscope light. Pediatric patients, mentally unstable patients, and patients unwilling or unable to cooperate are not ideal candidates for topical anesthesia. It should also be avoided in challenging surgeries where a prolonged surgical time is expected. An uncooperative patient being operated under topical anesthesia is at a significantly increased risk for PCR and other complications.
Peribulbar anesthesia is ideal for anxious patients unwilling to cooperate for topical anesthesia and also for cases with a prolonged surgical time. Intravenous sedation may help in excessively anxious patients. After administration of peribulbar anesthesia, apply pressure to the eye digitally or with the help of a super pinky ball to reduce the vitreous upthrust. An upthrust during surgery due to improperly administered peribulbar anesthesia increases the risk for PCR. In special cases such as phacomorphic glaucoma, increased intralenticular pressure or shallow anterior chamber, intravenous mannitol should be given preoperatively to achieve vitreous deturgescence and reduce the intraoperative upthrust. General anesthesia is preferred in pediatric and mentally unstable patients.
5.1.2.2 Pupillary Dilation
An adequate pupillary dilation should be achieved preoperatively with a mydriatic-cycloplegic. Addition of a sympathomimetic such as phenylephrine enhances pupillary dilatation. Preoperative administration of 0.4 % ketorolac tromethamine (Acular LS; Allergan Inc.) helps prevent intraoperative miosis and should be administered in cases with poor pupillary dilation and in those undergoing femtosecond laser-assisted cataract surgery [21]. Nondilating pupils and cases with posterior synechiae should be identified, so that appropriate surgical precautions can be taken.
5.1.3 Intraoperative Surgical Tips
5.1.3.1 Surgical Drape and Speculum
The surgical drape should be expertly applied and should not allow the escape of any eyelashes. The surgical field should not be obscured by the drape. There should be no undue reflections of the drape on the corneal surface which will hamper visualization during the surgery. An ideal speculum should be lightweight, have minimum extraneous parts, and should avoid undue pressure over the globe. An improper speculum may cause undue pressure on the globe, thereby increasing the vitreous upthrust and risk of PCR.
5.1.3.2 Proper Wound Creation
Design and construction of the corneal incisions for cataract surgery is fundamental for an optimum functional result. By incorporating both vertical and horizontal elements, multiplanar incisions are thought to better resist leakage under extreme pressures. In a coaxial system, precision of incision size becomes increasingly critical, with too small an incision restricting infusion flow and too large an incision allowing excessive fluid leakage.
An excessively tight wound increases the risk of wound burns. It also leads to localized corneal edema which increases progressively during surgery and impedes visualization. Intraocular manipulation of instruments becomes difficult with a tight wound associated with a long tunnel. The compatibility of the sleeve diameter with the incision size should be checked. The use of a large-diameter sleeve with a small corneal incision may be perceived as a tight wound and cause difficulties in surgical manipulations. In cases where the sleeve is appropriate for the incision size, the tight incision may be slightly enlarged with the help of a keratome.
While tight wounds increase the chances of burns, leaking wounds are the major cause for chamber instability. Irrigation-aspiration is difficult in cases with a leaky wound, with an increased risk of PCR especially during the aspiration of the last piece. The sleeve-incision relationship should be checked in all cases of leaky wounds, and an appropriate size of the sleeve should be selected in case of a mismatch. In cases with excessively leaky wound with frequent anterior chamber shallowing, the incision should be sutured and a separate site chosen to make another corneal incision. The rest of the surgery should be completed through the new adequate incision.
Femtosecond laser cataract surgery has now led to the customization of the incision with increasing reproducibility.
5.1.3.3 Proper Selection of Phacoemulsification Tip/Sleeve
During phacoemulsification, the size of the phaco tip and sleeve should match with each other and also with the wound incision to maintain a stable anterior chamber. Phacoemulsification tips are made of titanium, and they can have an opening angulation of 0 °, 15 °, 30 °, and 45 °. Greater angulation facilitates sculpting, whereas lower angle is good for occlusion. A 30 ° tip is suitable for both functions and is the most preferred one.
5.1.3.4 Good operating microscope with depth and coaxiality
An ideal microscope should provide good coaxial illumination for best visibility along with good stereoscopic depth perception. A wireless foot pedal should allow the surgeon to independently adjust the magnification and zoom during surgeries.
5.1.3.5 Intraoperative Maintenance of Visibility
Pooling of fluid occurs in various situations and hampers intraoperative visibility. Deep set eyes with narrow palpebral apertures are predisposed to accumulation of fluid. Improper patient position with the head tilted away from the operating surgeon may also lead to pooling. The head should be properly positioned to allow drainage of fluid. Methylcellulose may be used to avoid drying of the cornea in deep set eyes, and frequent instillation of fluid should be avoided. Hydroxypropyl methylcellulose 2 % has been found to provide better optical clarity than BSS during cataract surgery, as it does not require frequent instillation and prevents desiccation of the cornea. It is associated with better optical clarity and patient comfort [22]. Speculums with attached suction devices may be used to avoid pooling.
An inadvertent nicking of the conjunctiva during creation of incisions or incisions placed posterior to the limbus can lead to continuous accumulation of subconjunctival fluid throughout surgery. Clear corneal incisions are preferred, and care should be taken during creation of incisions to avoid breaching the conjunctiva. Massaging the conjunctiva with a dry sponge after making multiple stab incisions may relieve the ballooning of the conjunctiva to a certain extent [23].
5.1.3.6 Management of Nondilating Pupil
Intracameral adrenaline may help in achieving pupillary dilation in some cases with a small pupil (floppy iris/senile cataract/diabetes). Posterior synechiae should be released with the help of a Sinskey hook after instillation of a viscocohesive ophthalmic viscosurgical device (OVD) in the anterior chamber. A viscocohesive OVD further helps in achieving viscomydriasis. Use of Malyugin Ring and nylon iris hooks are vital in the management of cataract associated with nondilating pupil or intraoperative floppy iris syndrome. Increased intraoperative visibility helps in proper management of nucleus and hence minimizes the risk of PCR.
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