Cataract and Refractive Surgery Comanagement
Cataract Surgery Management
Jim Owen
Brian Chou
CATARACTS
ICD-9: 366.0—INFANTILE, JUVENILE, AND PRESENILE CATARACT
ICD-9: 366.1—SENILE CATARACT
ICD-9: 366.2—TRAUMATIC CATARACT
ICD-9: 366.3—CATARACT SECONDARY TO OCULAR DISORDERS
ICD-9: 366.4—CATARACT ASSOCIATED WITH OTHER DISORDERS
ICD-9: 366.8—OTHER CATARACT
ICD-9: 366.9—UNSPECIFIED CATARACT
ICD-9: 743.3—CONGENITAL CATARACT AND LENS ANOMALIES
THE DISEASE
Cataracts are a clouding of the crystalline lens. They are the leading cause of blindness in the world according to the World Health Organization. Depending on the location of clouding in the crystalline lens, cataracts are categorized as capsular, cortical, or nuclear.
Etiology
Although cataracts can be congenital, the most common cause of cataracts is because of natural aging. Other cataracts are associated with ocular inflammation, systemic disease (e.g., diabetes, Wilson’s disease), radiation exposure, trauma, and the prolonged use of corticosteroids and other medicines (e.g., phenothiazines).
The Patient
Clinical Symptoms
Patients with cataract may complain of reduced vision, glare while driving into oncoming headlights and sunlight, a dulling of colors, and double images.
Clinical Signs
Reduced best spectacle-corrected visual acuity with variable refraction.
Crystalline lens opacity noted with biomicroscopy. Dilated examination of the lens using an optic section and retroillumination assists in visualizing the affected portion of the crystalline lens.
The practitioner’s view of the posterior pole with fundoscopy is degraded proportionate to the density of the cataract.
Ancillary Tests
When a dense cataract obscures the practitioner’s view of the posterior pole during fundoscopy, the following measurements are useful:
Retinal acuity meter—This device provides an estimate of the patient’s achievable visual acuity following cataract surgery. A patient looks through pinhole glasses at a backlight visual acuity chart. Since the patient can alter head position and gaze, he or she is able to view around dense opacities.
B-scan ultrasound—When a dense cataract or vitreous hemorrhage obscure the direct view of the fundus, a B-scan can image the internal eye anatomy and determine whether the retina is intact.
The traditional indication for cataract surgery has been a best spectaclecorrected visual acuity worse than 20/40. However, functional disability can occur
even with acuity in the 20/25 to 20/30 range. When case history describes functional disability, cataract surgery can also be justified when the following measurements show visual reduction:
even with acuity in the 20/25 to 20/30 range. When case history describes functional disability, cataract surgery can also be justified when the following measurements show visual reduction:
Glare testing (e.g., Brightness Acuity Tester)
Contrast sensitivity (e.g., Bailey-Lovie and Pelli-Robson charts)
The Treatment
Cataract extraction with intraocular lens (IOL) implantation is appropriate if the cataract interferes with the patient’s activities of daily living. Surgery is also indicated if the cataract is obstructing examination of the posterior pole—for example, when the patient is under management for glaucoma or diabetic retinopathy.
Prior to surgery, a dilated fundus examination is necessary to rule out ocular pathology, which may contribute to reduced vision, such as macular disease. A-scan ultrasonography and keratometry are also required for calculating the power of the IOL implant. Specular microscopy is desirable for obtaining an endothelial cell count. An endothelial cell count of 1,000 cells/mm2 or less is at moderate to high risk of developing postoperative corneal edema (see section later).
Phacoemulsification describes cataract removal by emulsifying the lens with ultrasonic energy. Also called “phaco,” this technique requires a small incision at the corneal limbus followed by a capsulorhexis, or creation of an opening through the anterior capsule. These entries allow a small ultrasonic probe to contact the cloudy lens material, breaking it up into small pieces that are concurrently irrigated and aspirated from the capsular bag. In place of the cloudy lens, the surgeon places a folded IOL through the corneal incision into the capsular bag, where the IOL is unfolded and properly positioned. Sutures are not usually necessary to close the small incision.
Phacoemulsification is currently the preferred form of cataract removal and has essentially replaced the older technique of extracapsular cataract extraction (ECCE), where the entire crystalline lens (except for the capsule) was removed in one piece through a larger incision. The use of a small selfsealing incision in phacoemulsification allows for a faster recovery with less patient discomfort. Small incisions also minimize any change in corneal curvature, which could negatively affect the postoperative refractive outcome. In selected cases, however, ECCE is still appropriate over phacoemulsification, including congenital cataracts and extremely hard and dense cataracts.
IOL Options
Currently, there are IOL’s that correct more than spherical distance vision (Fig. 22-1). Toric IOLs can correct
corneal astigmatism, diffractive lenses provide vision at far and near, and there is a flexible plate haptic lens that provides vision at distance and up to intermediate distances.
corneal astigmatism, diffractive lenses provide vision at far and near, and there is a flexible plate haptic lens that provides vision at distance and up to intermediate distances.
 Figure 22-1. The Synchrony lens (Visiogen, Irvine, CA), a dual optics lens with a high plus anterior lens connected by a spring haptic to a low powered, static minus lens. |
The toric IOLs (Alcon Arcysof Toric, Staar Toric) have powers that range from -1.50 to -3.00 giving them an effective power of up to -2.00 at the corneal plane. Higher amounts of astigmatism can be treated by limbal relaxing incisions. Accurate corneal cylinder measurements are required either from keratometry or IOL Master measurements. Patients who have an unstable capsular bag, including pseudoexfoliation and weak zonules may not be good candidates for these lenses as the lens may not remain stable in the capsular bag.
Two lenses use diffractive technology to obtain near and far vision. The first diffractive lens approved was the Alcon Acrysof ReStor 4.0 Multifocal IOL. Recently, Alcon received approval for a 3.0 version of the ReStor lens. The ReStor lens is a single-piece aspheric, ultraviolet and blue light blocking, diffractive lens. The lenses use a mathematical concept of apodization to produce a gradual blending of the diffractive steps in the lens. These steps can be as small as 0.2 µm. The difference between the 4.0 and the 3.0 is the add power. As expected, the 4.0 is a 4.0 D add yielding a 3.2 D add at the spectacle plane and the 3.0 D add yielding a 2.5 add at the spectacle plane.
The Tecnis Multifocal IOL (AMOIrvince, CA) uses an aspheric optic design to offset the spherical aberration of the cornea. The lens has a prolate anterior surface with 0.27 µm of negative spherical aberrations and a posterior surface with diffractive rings to provide the near and distance images.
The principle side effect of diffractive lenses is glare and halos. This symptom is secondary to the two light foci within the patient’s eye. Additionally, these lenses cause a reduction in contrast sensitivity as a result of the separation in light energy into the two bundles.
The Crystalens HD (Baush and Lomb; Rochester, NY) is a plate haptic IOL with several unique features. The optic of the lens moves forward with the contraction of the ciliary muscle through an increase in vitreous cavity pressure. Secondarily, there is an “arching” of the lens centrally that results in an increase in negative spherical aberrations and coma. Finally, the HD version of the lens has a central asphericity that increases depth of focus resulting in improved near vision. A careful discussion regarding the limitations and potential complications of each of these lenses is important to have with each patient prior to surgery.
Postoperative Cataract Management
For the uneventful cataract surgery, an acceptable course of postoperative management includes the following:
Antibiotic drops (e.g., moxifloxacin HCl 0.5%, one drop four times a day for 1 week)
Nonsteroidal anti-inflammatory drops (e.g., diclofenac sodium 0.1%, one drop four times a day for 1 week)
Corticosteroid drops (e.g., prednisolone acetate 1.0%, one drop four times a day for 1 week, then one drop two times a day for 2 weeks)
The patient should use nighttime protective goggles and avoid strenuous activity for 1 to 2 weeks following surgery. No hot tubs, saunas, or swimming for 2 weeks after surgery
Although there is no universal postoperative schedule, the following
represents the author’s usual schedule and measurements performed at each:
represents the author’s usual schedule and measurements performed at each:
Postop 1 day. Unaided visual acuity, pinholed visual acuity, biomicroscopy, tonometry
Postop 1 week. Unaided visual acuity, refraction, biomicroscopy, tonometry
Postop 4 weeks. Unaided visual acuity, refraction, biomicroscopy, tonometry, prescribe eyewear
Postop 3 months. Spectacle-corrected visual acuity, biomicroscopy, tonometry, dilated fundus examination, recheck in 3 to 6 months
Postoperative Cataract Complications
Jim Owen
Brian Chou
UVEITIS
ICD-9: 364.23—LENS-INDUCED IRIDOCYCLITIS
ICD-9: 364.04—SECONDARY IRIDOCYCLITIS, NONINFECTIONS
THE DISEASE
Some inflammation in the anterior chamber is expected during the immediate postoperative recovery. However, an unusually severe degree of cell and flare early after surgery or the persistence of intraocular inflammation beyond 4 weeks is not typical and requires further investigation.
Etiology
There are multiple causes of abnormal intraocular inflammation following phacoemulsification. The differential diagnosis includes infectious endophthalmitis, phacoanaphylaxis to lens protein remnants, abrupt taper of corticosteroids, patient nonadherence in using corticosteroid drops, preexisting uveitis, epithelial down growth, use of prostaglandin-like ocular hypotensives, uveitis-glaucoma-hyphema (UGH) syndrome, and incarceration of vitreous or iris to the wound.
The Patient
Clinical Symptoms
The patient may complain of photosensitivity, eye pain, and blurred vision, each with a wide range of severity.
Clinical Signs
Biomicroscopy will show inflammatory cells and possibly flare (protein transudate) in the anterior chamber. Other findings may include keratic precipitates, ciliary injection, a miotic pupil, and an intraocular pressure that is lower in the affected eye. In severe cases, a hypopyon may be present with fibrin in the anterior chamber.
Ancillary Tests
If infectious endophthalmitis is suspected, perform cultures and sensitivities on samples of the aqueous and vitreous. Gonioscopy is sometimes useful for detecting vitreous or iris to the wound and detecting remnants of lens material in the anterior chamber.
The Treatment
Treatment is based on the suspected cause of postoperative uveitis. For infectious endophthalmitis, refer to the section “Infectious Endophthalmitis” of this chapter. For phacoanaphylaxis, refer to Chapter 10, section “Anterior Uveitis”. If case history indicates patient nonadherence in using the corticosteroid drops or an abrupt taper, the use of the drops should be reinstituted, emphasizing the importance of compliance to the patient. For preexisting uveitis, refer to Chapter 10, section “Anterior Uveitis”. For epithelial down growth, the patient should undergo argon laser treatment of the affected areas. In the case of prostaglandin-analog-induced uveitis, switch the patient to another class of ocular hypotensive. With UGH syndrome, the patient should
have the IOL explanted or reanchored to prevent further iris chafing. For vitreous to the wound or iris prolapse, the patient should be referred promptly to the cataract surgeon for surgical management.
have the IOL explanted or reanchored to prevent further iris chafing. For vitreous to the wound or iris prolapse, the patient should be referred promptly to the cataract surgeon for surgical management.
CORNEAL EDEMA
ICD-9: 371.2—CORNEAL EDEMA
ICD-9: 371.20—CORNEAL EDEMA, UNSPECIFIED
ICD-9: 371.22—SECONDARY CORNEAL EDEMA
ICD-9: 371.23—BULLOUS KERATOPATHY
THE DISEASE
Pseudophakic bullous keratopathy describes irreversible corneal edema following cataract surgery with IOL implantation. Surgical trauma and inflammation can damage the corneal endothelium, the layer of cells that regulates corneal hydration. The effect of mild corneal edema is limited to the stroma, while moderate to severe corneal edema also affects the epithelium. When the corneal epithelium is edematous, blisters or “bullae” form that substantially reduce vision.
Etiology
The corneal epithelium and endothelium are semipermeable membranes involved in regulating corneal hydration. The stroma lying in between contains proteoglycans that attract fluid into the collagen. Intraocular pressure also tends to drive fluid into the cornea. When the stroma imbibes fluid, the tissue swells. To prevent excess corneal swelling, the endothelium drives fluid out of the cornea by creating an osmotic gradient. If the endothelial pump is impaired by disease or trauma, steady-state hydration is lost, causing corneal edema.
The Patient
Clinical Symptoms
Blurry and cloudy vision results with epithelial edema. The rupture of the epithelial bullae can cause pain, foreign body sensation, and photophobia.
Clinical Signs
Biomicroscopy will show folds in the corneal stroma, areas of microcystic epithelial edema, and epithelial bullae. Chronic cases may have corneal neovascularization. Endothelial guttata may be observable in cases of preexisting endothelial dystrophy (e.g., Fuchs).
Ancillary Tests
Although the clinical diagnosis of corneal edema is primarily made with biomicroscopy, specular microscopy and pachymetry can assist in the diagnosis. These measurements are also useful preoperatively for assessing the risk of persistent postoperative corneal edema.
Specular microscopy. Imaging the endothelial layer provides a method for obtaining endothelial cell density. Normal densities may range from 2,000 to 3,500 cells/mm2 depending on the age of the patient. Densities of 1,000 cells/mm2 or less present an increased risk of problematic postoperative corneal edema.
Pachymetry. The average central corneal pachymetry is approximately 550 µm, but in an edematous cornea, the tissue can swell substantially and result in increased corneal thickness of over 600 µm. This measurement is not diagnostic alone, since some individuals without corneal edema have thick corneas. However, within an individual, serial pachymetry can indicate diurnal fluctuations in corneal hydration or show longer term changes in corneal hydration because of endothelial damage.
The Treatment
Medical therapy primarily involves topical hyperosmotics, including 2% and 5% NaCl drops and ointment. Topical hyperosmotics draw out excess fluid from the cornea. Hyperosmotic ointment is
usually used at bedtime, while the drops are used three to five times daily in the morning. In some cases, ocular hypotensives can also minimize the degree of corneal edema.
usually used at bedtime, while the drops are used three to five times daily in the morning. In some cases, ocular hypotensives can also minimize the degree of corneal edema.
When there is a rupture of epithelial bullae, a high dK bandage soft contact lens (e.g., lotrafilcon A) can control the discomfort until re-epithelialization. Since ruptured bullae create the potential for microbial entry, a broad spectrum antibiotic drop should be prescribed for prophylaxis (e.g., moxifloxacin 0.5% t.i.d.).
Corneal transplantation is reserved for severe corneal edema where hyperosmotics provide insufficient benefit.
INTRAOCULAR PRESSURE SPIKES
ICD-9: 365.04
THE DISEASE
Increased intraocular pressure is commonly detected in the early postoperative cataract recovery. While a nonglaucomatous eye can sustain an IOP into the mid-20s mm Hg for a short duration without damage, higher IOPs require clinical action.
Etiology
Intraocular pressure spikes may result from a variety of causes:
Retained viscoelastic. Viscoelastic is the thick cushioning solution used to “inflate” the anterior chamber during surgery and to protect the endothelium from mechanical insult. In some individuals, viscoelastic can significantly impede aqueous outflow, causing an IOP spike.
Inflammatory material, hyphema, and dispersed pigment. The trabecular meshwork can become clogged with any of these components, leading to an IOP spike. Retained cortical fragments can incite an inflammatory response in proportion to the amount of cortical remnants. Uncommonly, an IOL may incarcerate an iris blood vessel, causing hemorrhage or rub against the iris dispersing pigment granules.
Pupillary block. Formation of synechiae between the iris, and IOL can disrupt aqueous outflow and increase IOP. Pupillary block is rare and is seen mostly with anterior chamber IOLs where an iridectomy was not performed.
Malignant glaucoma. This rare condition results when aqueous is misdirected into the vitreous cavity causing the iris to bow forward, causing a shallow anterior chamber. Unlike pupillary block, a peripheral iridotomy does not resolve the increased IOP.
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