Competencies in Cataract Surgery
Track No. 4: Retina specialists receive an update on cataract surgical standards.
The most important diagnostic tests for patients with cataracts are keratometry, manual or automated; A-scan ultrasonography; and automated optical biometry to measure corneal curvature and accurate axial length of the eye. Immersion ultrasound is the best way to measure the length of the eye and the axial length because the probe has no direct contact with the eye. This information is then used with one of the intraocular lens (IOL) calculation formulas (eg, Holladay, Holladay 2, SRK/T, Haigis, Aramberri double-K, Hoffer Q) to determine the correct lens power. Optical biometry (Lenstar, Alcon/Haag-Streit) has been used increasingly to measure both the axial length and central corneal curvature, as well as other parameters such as anterior chamber depth that are used with newer formulas.
ANTERIOR SEGMENT DISORDERS
Dry eye should be addressed prior to cataract surgery because there is a degree of dryness that typically is present postoperatively. Standard protocol for assessing patients for dry eye includes patient history, Schirmer testing, and lissamine green staining. Tear osmolarity testing is among the newer methods for assessing dry eye.
Patients with Fuchs dystrophy have low endothelial cell counts and must be evaluated, often with corneal pachymetry and endothelial cell counts to determine if a standard cataract surgery is possible or whether an alternative procedure should be performed.
Patients who have glaucoma should be evaluated to assess the angle. Although cataract surgery can help by deepening the angle, patients may require dilation drops, which can narrow the angle, causing increased intraocular pressure (IOP) and permanent damage. For these patients, a combined cataract and glaucoma surgery or preoperative glaucoma treatment may be advisable.
Because of the potential for complications in surgery resulting from zonular weakness and poor pupil dilation, patients with pseudoexfoliation should be screened prior to surgery for subtle lens subluxation, zonular dialysis, or phacodonesis. Lidocaine can be applied preoperatively and intraoperatively. Pupil expansion devices and capsular tension rings can be used to stabilize the eye.
A nuclear sclerotic cataract is the most common type, in which older patients develop diffuse yellowing of the lens. Posterior subcapsular cataracts are common in patients who have diabetes and often present in patients with decreased contrast sensitivity.
Cortical cataracts cause spoke-like changes in the lens of the patient, and the visual acuity result can be significant glare. The effect is not consistent, but, in photopic conditions, the glare effect is serious. Cortical cataracts create white spots on the lens and can make the creation of capsulorrhexis challenging in surgery due to poor visualization.
The rarer types of cataracts include congenital and traumatic cataracts. With these, it is important to stabilize the capsular bag, and anterior vitrectomy may be necessary to prevent dropped nuclei.
When considering infection prophylaxis, the patient should be evaluated for preexisting blepharitis because, although we prep and isolate the eyelid margins, Staphylococcus and Streptococcus usually originate from the eyelid margin. If a patient has blepharitis, it is advisable to pretreat with hygiene and antibiotic ophthalmic preparations. The typical regimen is to pretreat with antibiotics for 3 days prior to surgery and then to apply 5% povidone-iodine to the eyelid margin in preparation for surgery.
If complications arise during surgery, such as posterior capsular rupture and vitreous loss, patients are at a higher risk for infection. It is advisable to use systemic fluoroquinolones for 3 to 5 days postoperative.
Viscoelastic is either cohesive or dispersive in composition. These devices protect the corneal endothelium during surgery and create space for manipulation of the eye.
At the beginning of a case, the viscoelastic is injected into the anterior chamber. Because we want the viscoelastic to stay in the eye as we perform capsulorrhexis, we tend to use a dispersive agent, which will stay in place and protect the cornea and will also keep the lens pushed posteriorly so that there is less tendency for the capsulorrhexis or a capsular tear to expand peripherally.
Later, we inflate the capsular bag with a cohesive viscoelastic to facilitate IOL insertion. The cohesive viscoelastic protects the posterior capsule and the corneal epithelium, and we can remove it quickly after the lens is in place. Other situations for which we would use either type of viscoelastic include complicated situations such as zonular weakness or dropped nucleus to keep the vitreous back while proceeding to anterior vitrectomy.
Options for anesthesia include topical, regional block, and general. The increasing trend is to perform cataract surgery under topical anesthesia. The most common regimens are preoperative topical proparacaine or tetracaine drops instilled onto the cornea 15 to 20 minutes prior to surgery. Sometimes lidocaine gel is used to apply anesthesia to the surface structures of the eye, and there is some penetration inside the eye. Many surgeons inject intracameral nonpreserved 1% lidocaine to provide additional anesthesia to the iris and the ciliary body.
If there is a concern that the case will be complicated or if there is an issue with patient cooperation, it is common to use a block. Some surgeons, however, still block all their patients. The most common block is to use 2% lidocaine, sometimes in combination with 0.5% or 0.75% bupivacaine in either a peribulbar or retrobulbar block to stabilize the eye and keep it from moving during surgery.
The last option is to use general anesthesia, which is typically reserved for very young patients or those who have great difficulty cooperating or sitting still.
SURGICAL TOOLS and TECHNIQUES
The most recent technological advance in the cataract subspecialty is laser cataract surgery, in which a femtosecond laser is used to create incisions and to fragment the lens. The use of ultrasound phacoemulsification, however, remains the most common technology for cataract removal. Although intracapsular cataract extraction (ICCE) and extracapsular cataract extraction (ECCE) are no longer frequently employed, ICCE may be employed for patients in whom the lens is free floating or in patients with Marfan disease, when there is no way to stabilize the lens because the zonules are either gone or almost gone.
ECCE is still used in situations in which economy dictates the need for a cheaper procedure that does not require advanced equipment. Although a large incision (10-12 mm) that must be sutured is required, resulting in higher rates of astigmatism and longer recovery times, there are no data showing that the long-term overall visual acuity outcomes with ECCE are significantly worse than with phaco.
Phacoemulsification, the most common method of cataract extraction in the United States, typically requires an incision that ranges from 2.2 mm to 3.0 mm. Three common techniques used in phaco include the standard divide-and-conquer technique, in which the nucleus is grooved into four pieces and extracted; the stop-and-chop technique, in which the lens is cut in half and then sliced into smaller and smaller pieces; and the pure chop technique, in which the lens is grabbed with the phaco probe and then little pieces are carved off for extraction.
There are two major subtypes of IOLs: anterior chamber IOLs and posterior chamber IOLs. Posterior chamber IOLs are available as one-piece or three-piece lenses. Refractive IOLs are the most recent addition to the category of posterior chamber IOLs.
Anterior chamber IOLs are implanted in front of the iris and are uncommonly used today, as it is preferred to implant the IOL in the posterior chamber. However, if the situation is such that the lens support has been completely lost or if there is significant trauma to the lens capsule, an anterior chamber IOL may be implanted. Anterior chamber IOLs cannot be folded, so a large 6-mm incision is required for implantation and the incision must be sutured.
One-piece posterior chamber IOLs are the most commonly used IOLs. These can be made of acrylic or silicone, although acrylic IOLs are more widely used because the material is softer and more maneuverable once in the eye. These IOLs are foldable so they fit in a smaller incision. However, they can only be implanted in the capsular bag—not in the sulcus for more complicated cases.
A three-piece posterior chamber IOL can be placed directly in the capsular bag, and, if there is a hole in the capsule, it can be placed alternatively in the sulcus so that it fits in front of the iris. There are foldable and nonfoldable versions of three-piece IOLs. Although posterior chamber lenses are usually placed in the capsular bag, some can be sutured to the iris or sclera.
Toric and multifocal IOLs are specialty lenses used to correct astigmatism (toric) or to address a patient’s need to see at distance, intermediate, and close ranges (multifocal). These IOLs are not typically covered by insurance and often come at an out-of-pocket cost to the patient for routine cataract surgery.
As mentioned earlier, viscoelastic is useful in protecting the corneal endothelium, and it is also important to avoid any contact between the surgical instruments and the endothelium. The most common intraoperative complication is extension of the capsulorrhexis, which is basically when a circular capsulorrhexis is not achieved and the opening extends into the zonules, creating a risk for posterior capsular tear. An extension of the capsulorrhexis can also affect the positioning of the IOL.
Another complication is when nuclear or cortical fragments are left behind. These do not tend to spontaneously dissolve, and the concern is that secondary glaucoma may develop from the lens’ proteins clogging the trabecular meshwork. In some cases, a small amount of cortical material can be watched and may absorb, but, if there is a large amount, it may have to be removed. In general, lens material left behind in the eye is something that is discovered postoperatively.
A posterior capsular tear can result in dropped lens fragments to the vitreous, raising the risk for endophthalmitis and postoperative inflammation. If a hole is seen in the capsule, dispersive viscoelastic can help create a barrier for lens fragments, but postoperative intervention may be necessary. In the presence of vitreous loss, an anterior vitrectomy may be necessary to ensure that the vitreous is not extending to the incision, putting the patient at higher risk for inflammation, cystoid macular edema (CME), and infection.
Uncommon complications include retinal detachment from manipulation of the eye. For patients at high risk for retinal detachment, such as those with high myopia, one performs a careful preoperative evaluation, but this complication can still occur in some cases.
A suprachoroidal hemorrhage or a choroidal effusion may also occur intraoperatively, which can happen when the pressure goes low during the case. Hyperopic and smaller eyes are at a higher risk, as are patients who have had prior glaucoma surgery or vitrectomy. In cases of suprachoroidal hemorrhage or choroidal effusion, the eye must be closed immediately to stop the contents from expelling.
A common complication after cataract surgery is corneal edema, particularly after longer cases that have required extensive manipulation, raising the risk of endothelial cell dysfunction. Corneal edema is typically treated with antiinflammatory therapy. In severe cases, more aggressive therapy may be required to help improve endothelial cell function. Patients who have had inflammation or uveitis before surgery may also require more aggressive antiinflammatory therapy.
CME is a concern after surgery, causing blurry vision, but the use of topical nonsteroidal antiinflammatory agents (NSAIDs) along with steroids can reduce the occurrence. One study cited CME rates as low as 2.4% in over 1500 patients with the use of NSAIDs.1
Another complication that can arise postoperatively is increased IOP. The most common cause of an IOP spike is that some viscoelastic has been left in the eye. This can be treated with glaucoma medications or, if retained viscoelastic is the suspected cause, the surgeon can remove the viscoelastic material by reopening the paracentesis.
The most devastating postoperative complication is endophthalmitis, which presents approximately 3 to 5 days postoperative. The infection prophylaxis discussed earlier is critical, particularly with more aggressive organisms, as blindness can result. Postoperative examination and early recognition are paramount to prevent blinding complications from infection.
Special cases include pediatric cataract, in which the most significant concern is amblyopia. Other cases include patients with narrow- or closed-angle glaucoma, in which the cataract affects the angle, and floppy iris syndrome, in which a patient may be taking the selective alpha-blocker tamsulosin. For these, preoperative evaluation is critical.
Trauma cases can also be difficult and may require an alternative surgical approach. Patients who have had prior vitrectomy may have a lens that is less stable due to a lack of the vitreous pressure. When a patient requires a combination cataract and vitrectomy surgery, it is important for the cataract surgeon to communicate with the retina surgeon to plan the case and determine whether the surgeries should be performed separately or in conjunction.
More information and complete study materials can be found on the American Academy of Ophthalmology website at: http://one.aao.org/CE/MOC/default.aspx.
1. Henderson BA, Kim JY, Ament CS, Ferrufino-Ponce ZK, Grabowska A, Cremers SL. Clinical pseudophakic cystoid macular edema. Risk factors for development and duration after treatment. J Cataract Refract Surg. 2007;33(9):1550-1558.
Robert J. Noecker, MD, MBA
• in private practice at Ophthalmic Consultants of Connecticut in Fairfield, Conn.
• financial interest: none acknowledged