© Springer International Publishing Switzerland 2017
Shlomit Schaal and Henry J. Kaplan (eds.)Cystoid Macular Edema10.1007/978-3-319-39766-5_88. Cystoid Macular Edema in Retained Lens Fragments After Cataract Surgery
(1)
Department of Opthalmology, Hashemite University, Zarqa, Jordan
Introduction
Cystoid macular edema is a well-known complication of retained lens fragments after cataract surgery. It occurs in 11–28 % of cases [1, 2]. It is one of the causes of visual loss after uneventful cataract surgery also. It has been reported to occur in 2–3 % after phacoemulsification [3–5]. Retained lens fragment (RLF) is a serious event in cataract surgery that occurs in about 1 % of cases. It frequently requires both medical and surgical intervention to minimize complications and visual loss. In this chapter, we will discuss the pathophysiology of CME in RLF and proper medical and surgical management.
Incidence and Etiology
RLF is an uncommon complication of cataract surgery. It has been reported to occur in 0.18–1.1 % of cases [6–8]. Certain factors affect the incidence of RLF including the surgical technique that has been used to remove the cataractous lens (extracapsular extraction vs. phacoemulsification), surgeon’s experience, type of cataract such as posterior polar cataract, and hard nucleus [6, 9–11].
The size and nature of the dropped lens varies depending on the stage during phacoemulsification when the posterior capsule rupture (PCR) occurs. It may vary from a dropped whole nucleus if PCR occurred during initial hydrodissection, to only soft cortical matter if PCR occurred later during irrigation aspiration. The size and the nature of the dropped lens pieces will affect the level of induced inflammation, the potential complications, and the management plan.
CME has been reported to occur in 11–28 % of RLF and is a major reason for reduced visual acuity [1, 2] although CME is well known to occur even after uneventful phacoemulsification [12]. It is believed that the inflammatory mediators released in response to cataract surgery play a major role in the formation of CME [13].
Pathophysiology of Lens-Induced Immune Response
The anterior chamber of the eye is immunologically privileged, and lens proteins are sequestered from the host immune system by the lens capsule [14]. However, recently it has been shown that crystallin lens proteins are present within the anterior chamber [15] in other ocular tissues and in serum [16]. Nevertheless, the immune system is normally tolerant to lens crystallins via various immunoregulatory mechanisms [14, 17]. However, tolerance to these proteins is abrogated by inflammatory mediators released during cataract surgery [18] that induces an immediate autoimmune reaction [18–20]. An intense immune reaction ensues, involving macrophages, that breaches the blood retinal barrier resulting in cystoid macular edema (CME) [21, 22]. Rupture of the anterior vitreous face may contribute to the development of CME [23, 24].
Clinical Presentation
Patients with RLF present postoperatively with reduced visual acuity from several possible causes – anterior uveitis, elevated intraocular pressure, corneal edema, and CME [1, 2, 5, 10, 25–29]. Clinically significant CME may occur immediately after surgery or within several weeks, although 80 % of patients show spontaneous resolution [30].
Clinical examination will reveal intraocular inflammation with lens fragments floating in the vitreous cavity or lying on the retinal surface. Fundus fluorescein angiography will frequently show a typical petalloid pattern although optical coherence tomography is most helpful in demonstrating the anatomical presence of CME with multiple intraretinal cysts [31–33]. Retinal detachment has been reported to be present in 3.8–45 % of cases, most frequently secondary to unsuccessful attempts by the cataract surgeon to recover the dislocated fragments [34–37]. Among other complications are retained lens fragments in the anterior chamber, as well as posterior to the iris presenting as an iris mass [39–41].
Management of CME Secondary to RLF
Medical Management
Medical treatment of CME may include the use of topical nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroids [44]. Prophylactic use of NSAID agents has been shown to be effective in reducing the incidence of pseudophakic CME [42, 43]. However, since intraocular inflammation is the major cause of RLF, CME aggressive corticosteroid therapy is important both topically and systemically [44].However, surgical removal of the dislocated lens fragments via pars plana vitrectomy will remove the inciting proteins and lens fragments, as well as quell the inflammation.
Surgical Management
Dislocation of lens fragments during cataract surgery can be the result of several factors – a hard nucleus, posterior polar cataract, weak zonules (as in pseudoexfoliation or various genetic syndromes [Marfans, Ehlers-Danlos]), high myopia, but is most frequently associated with a poorly dilated pupil. In difficult cases, the surgeon may need to stabilize the lens capsule and detect/manage posterior capsular tears if they occur during the operation.
The main goals of intraoperative management is to maintain anterior chamber depth, prevent vitreous prolapse, avoid dislocation of lens material into the vitreous cavity, and finish the case as safely and quickly as possible with or without intraocular lens implantation [45–48].
From a vitreoretinal perspective, the anterior segment surgeon should minimize the manipulation of posteriorly dislocated lens fragments in the vitreous cavity to avoid the creation of vitreous traction resulting in retinal tears, detachment, and/or vitreous hemorrhage.
Conservative Management Versus Pars Plana Vitrectomy
The ultimate goal in the management of RLF cases is to ensure a good visual outcome. Pars plana vitrectomy surgery has been shown to be effective in resolution of corneal edema, control of intraocular pressure, and preservation of good vision [9, 10, 26]. In 2009, Barr and Schaal reported a retrospective case series of 42 patients divided into three groups: group 1 (12 patients) had early vitrectomy (<1 week), group 2 (15 patients) late vitrectomy (>1 week), and group 3 (15 patients) only medical treatment. At 1 year, there was no statistically significant difference in final visual acuity between the three groups (group 1, 20/25; group 2, 20/28; group 3, 20/38, p = 0.52) or intraocular pressure [1].
Although there are no established guidelines to determine when to treat cases conservatively, their results suggested that if there isn’t a rapid response to medical therapy, vitrectomy surgery should be performed.
Other reports also did not find any relationship between timing of vitrectomy and final visual outcome [34, 35, 49–54].
The most important factor in determining the timing of vitrectomy surgery is the severity of the intraocular inflammation – mild intraocular inflammation may be managed initially by topical or systemic therapy. Persistent inflammation, worsening of visual acuity, increasing intraocular pressure, and severe ocular pain are indications for early vitrectomy.
Technique of Pars Plana Vitrectomy
The most common technique reported by retinal surgeons to remove residual lens matter is three-port 20-gauge pars plana vitrectomy. They allow use of the ultrasonic fragmatome if necessary to remove large nuclear fragments from the vitreous cavity. Some surgeons crush the retained lens pieces between the light pipe and vitrectomy probe which facilitates their removal by the vitrectomy probe without the use of the fragmatome [29, 35, 49]. Some surgeons have used the OZil phaco handpiece instead of the fragmatome and showed very good results [55].
The most important step during vitrectomy surgery for removal of RLF is to perform a complete vitrectomy, including meticulous removal of the vitreous around the lens fragments before removal to prevent traction on the retina. This will reduce the incidence of retinal tears and retinal detachment. Some surgeons suggest the use of perfluorocarbons (a heavy liquid frequently used in vitreoretinal surgery especially in retinal detachment) to separate the lens fragments from the retinal surface and bring them into the mid-vitreous cavity for safer removal by the fragmatome or vitrectomy probe [29, 35, 49, 56, 57].
With the introduction of the small gauge sutureless vitrectomy (23 and 25 gauge), surgeons have began to use small ports for the removal of RLF [58–62]. In 2009, Ho and colleagues reported a case series where 25-gauge vitrectomy was used exclusively to remove lens fragments of various sizes [60]. They reported comparable outcome and rate of complications to 20-gauge vitrectomy [60]. In an era where there is a continuous shift toward less-invasive and sutureless surgeries, small gauge vitrectomy surgery will continue to gain popularity for the removal of RLF.
Outcome of Pars Plana Vitrectomy Surgery for RLF
Pars plana vitrectomy surgery to remove vitreous lens fragments has been shown to be associated with improved visual acuity, reduction of intraocular inflammation, and intraocular pressure; 20/40 or better vision ranged from 44 to 72 % [9, 26, 50]. In a multivariate analysis to identify predictive factors of poor visual outcome (20/200 or worse), the following were shown to be anterior vitrectomy at the time of cataract surgery, absence of sulcus lens, preexisting eye disease, and development of glaucoma [50]. Other factors associated with a poor visual outcome include retinal detachment and CME [28, 35, 37, 38].
Conclusion
CME is a major complication after cataract surgery complicated by RLF. The introduction of modern phacoemulsification techniques resulted initially in an increased incidence of posterior lens fragment dislocation. Management of CME includes aggressive medical therapy with topical and oral NSAIDs and corticosteroids. If severe intraocular inflammation doesn’t resolve quickly, pars plana vitrectomy with removal of residual lens material should be performed.
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