Fig. 17.1
Ectopia and coloboma of the lens (arrow) in the right eye of a 13-year-old girl
17.1.1.3 Ectopia Lentis Associated with Concurrent Systemic Maldevelopment
Marfan Syndrome
Marfan syndrome is the most common type of congenital EL (Fig. 17.2a). Its incidence rate is between 3 and 10/10,000, and there are no significant differences between genders, regions, or races [6–9]. This disease shows an autosomal dominant inheritance pattern and generally presents as multiple connective tissue abnormalities. It is caused by the mutation in the fibrillin-1 encoding gene FBN1, which is involved in mesodermal development. At present, more than 1200 FBN1 mutation sites have been found [10]. Multisystem involvements are common in Marfan syndrome, including the musculoskeletal system, the heart and blood vessels, and the eyes [11, 12]. Most affected children have an unusually long-limbed body habitus (Fig. 17.2b), arachnodactyly, scoliosis, pectus carinatum, and ligamentous laxity; the cardiovascular abnormalities include atrial septal defect, heart valve abnormalities, aortic dilatation, and aortic aneurysm, which are the main causes of death in these children [13]. The current international diagnostic criteria, proposed by Loeys et al. in 2010 [14], further emphasizes the importance of ocular and cardiovascular lesions in making a definite diagnosis of Marfan syndrome compared with previous diagnostic criteria.
Fig. 17.2
Clinical manifestations of Marfan syndrome. (a) An 8-year-old boy with Marfan syndrome presented with EL in the right eye. The lens displacement was in the superior and nasal direction, and the excessively stretched zonules were visible with pupil dilation. (b) The boy had concomitant musculoskeletal abnormalities of arachnodactyly and syndactyly (black arrow) and a tall, slim figure
The typical ocular manifestation of Marfan syndrome is progressive development of EL, which occurs in about 30–50 % of patients. The lens displacement is usually bilateral, symmetrical, and with a superior and nasal direction. When the pupil is dilated, the lens equator and the excessively stretched zonules are visible (Fig. 17.2a) [15, 16]. The ectopic crystalline lenses can cause refractive errors that are difficult to correct (mostly high myopia), as well as an increased risk of strabismus and amblyopia [17]. Other ocular abnormalities include macrocornea, poor elasticity of the iris, disappearance of the iris crypts, primary open-angle glaucoma, peripheral retinal degeneration, and retinal detachment [18, 19]. Initial subluxation of the lens may progress to complete dislocation, which gives rise to complications such as secondary glaucoma and phacogenic uveitis [18].
Homocystinuria
Homocystinuria is another common syndrome associated with congenital EL and occurs as an autosomal recessive condition. Mutation in the coding gene of cystathionine beta-synthase (CBS) [20, 21] leads to CBS defect, which causes increased cystine levels in the blood of the affected child, which in turn causes metabolic disorders. The typical ocular manifestation is bilateral and symmetrical EL, where the lens is often displaced toward in an inferior and nasal direction. EL can be accompanied by corneal opacity, congenital cataract, iris atrophy, optic nerve atrophy, and retinal detachment [22]. Systemic pathologies of homocystinuria include osteoporosis, mental retardation, epilepsy, thrombophilia, and, in severe cases, pulmonary embolism.
Weill–Marchesani Syndrome
Weill–Marchesani syndrome is an autosomal recessive genetic disease, and it is primarily associated with mutation in the ADAMTS gene, which is related to fibrillin-1 [20, 23]. Its clinical manifestations are contrary to those of Marfan syndrome, and the affected child has a short, fat figure and brachydactyly (Fig. 17.3). The typical ocular manifestations include spherophakia and the resulting high myopia, as well as EL toward the nasoinferior quadrant. In severe cases the crystalline lens can be dislocated into the anterior chamber. Therefore, there is a high incidence of secondary glaucoma in patients with Weill-Marchesani syndrome [24].
Fig. 17.3
Weill-Marchesani syndrome. (a) An 8-year-old girl with Weill-Marchesani syndrome had ectopic spherophakia; (b) the affected child had a short, fat figure and brachydactyly
Hyperlysinemia
Hyperlysinemia is a rare autosomal recessive genetic disease characterized by lysine dehydrogenase deficiency, which is caused by mutations in the AASS gene that encodes lysine-ketoglutarate reductase and saccharopine dehydrogenase (SDH) [25]. Increased plasma lysine concentration is the main criterion in making an unequivocal diagnosis. The disease mainly presents as mental retardation, spherophakia, and EL. Spherophakia is the pathognomonic manifestation of this syndrome.
17.1.2 Traumatic Ectopia Lentis
Traumatic EL is typically caused by blunt trauma. Affected children have a history of trauma that may be left unnoticed until visual symptoms emerge and ophthalmic examination reveals traumatic EL. It is unilateral in most cases and may be associated with concurrent traumatic cataract, angle recession, secondary glaucoma, and commotio retinae (contrecoup injury to the retina due to blunt ocular trauma).
17.1.3 Spontaneous Ectopia Lentis
Mechanical stretching of zonular fibers due to intraocular lesions or weakening of the zonules due to inflammation and degeneration can lead to spontaneous EL. The former is seen when enlargement of the eye occurs due to congenital glaucoma (buphthalmos) or posterior staphyloma. It can also be found in traction or occupying intraocular lesions, such as inflammatory adhesion of the ciliary body, vitreous strands, and intraocular tumors [26].
17.2 Clinical Manifestations of Ectopia Lentis in Children
Ectopia lentis is clinically divided into lens subluxation and lens dislocation according to the range of zonular dehiscence and the severity of lens displacement.
17.2.1 Lens Subluxation
When an area of the zonular fibers are weakened or ruptured and the crystalline lens deviates from its normal anatomical position, the condition is referred to as lens subluxation. There are two major manifestations. First, the partially weakened or ruptured zonules cause an increase in lens curvature and subsequent lens-induced myopia; second, the lens displacement or tilting can cause lens-induced irregular astigmatism, which is often difficult to correct using spectacles or contact lenses. If the ametropia cannot be corrected, amblyopia and strabismus will eventually occur. Monocular diplopia and glare can occur in children with severe subluxation, as well as secondary glaucoma.
Slit-lamp examination may reveal iridodonesis, phacodonesis, and/or vitreous hernia [27]. In some affected children, the equator of the lens and the stretched or ruptured zonular fibers may be observed in the pupillary zone when the pupil is dilated. Double moon-shaped reflections and double fundus images are observed in direct ophthalmoscopy.
17.2.2 Lens Dislocation
When there is complete rupture of all zonular fibers, the crystalline lens leaves its normal anatomical position to enter the anterior chamber or vitreous cavity; this is known as lens dislocation. The dislocated lens may occlude the pupil and displace anteriorly into the anterior chamber (Fig. 17.4a) or displace posteriorly into the vitreous cavity (Fig. 17.4b). Lens dislocation can cause serious complications such as secondary glaucoma, phacogenic uveitis, and retinal detachment [28, 29]. A dislocated lens may even prolapse outside the eye through a cornea perforation or enter the subconjunctival or subtenon space through a scleral rupture. The pediatric patient may present with the following clinical findings depending on the position of the dislocated lens:
Fig. 17.4
Lens dislocation. (a) The crystalline lens was dislocated into the anterior chamber, and its edges showed a golden reflection. (b) B-scan ultrasonography of another case of lens dislocation revealed the dislocated lens (arrow) in the vitreous cavity
- 1.
Captured in the pupil: Blurred vision and acute ocular hypertension together with pupillary block.
- 2.
Dislocated into the anterior chamber: On slit-lamp examination, the dislocated lens appears as an oil droplet with a golden reflection at its edges. Lens opacity may be present. It can cause acute elevation of intraocular pressure. Corneal endothelial loss or decompensation and anterior uveitis may also occur [30].
- 3.
Dislocated into the vitreous cavity: Slit-lamp examination shows a deepened anterior chamber, iridodonesis, absence of the crystalline lens in the pupillary zone, and sometimes vitreous hernia in the anterior chamber. A small mass with the shape of an oil droplet with dark edges is seen using direct ophthalmoscopy. If the lens capsule is intact and no complications occur, the affected eye remains aphakic without other symptoms; if the capsule has been ruptured, the escaped cortex may give rise to lens-induced uveitis and phacolytic glaucoma [31].
17.3 Ophthalmic Examination of Ectopia Lentis in Children
A complete examination of the patient is important for the development of a therapeutic regimen. If necessary, uncooperative children may undergo examinations under sedation or general anesthesia.
- 1.
Visual acuity
The dislocated lens may lead to myopia, hyperopia, and astigmatism. If not promptly corrected, the risk of amblyopia and strabismus is increased. Therefore, distance and near visual acuities (VA) should be examined, and best corrected visual acuity (BCVA) should be obtained through accurate refraction. This will provide a basis for determining treatment options.
- 2.
Intraocular pressure
Both EL and disorders of ocular development can cause secondary glaucoma. Therefore, measurement of intraocular pressure is important for timely detection of glaucoma.
- 3.
Ocular alignment
Children with congenital EL may have concurrent strabismus. A simple test of alignment may be applied, using penlight reflection on the cornea combined with a cover test.
- 4.
Anterior segment examination
The grading of the extent of zonular weakness/dehiscence and the severity of EL is an important guide for clinical treatment. Hoffman et al. [32] divided lens subluxation into minimal to mild, moderate, and severe based on the findings from slit-lamp examination after pupil dilation: (1) minimal to mild subluxation in which the lens edge uncovers 0% to 25% of the dilated pupil; (2) moderate subluxation in which the lens edge uncovers 25% to 50% of the dilated pupil; (3) and severe subluxation in which the lens edge uncovers greater than 50% of the pupil.
The pupils of children with EL should be fully dilated for slit-lamp examination of the anterior segment. This enables the extent and direction of EL, as well as the severity and range of zonular abnormality, to be carefully examined. Alteration of lens location between erect and recumbent positions is noted to help determine the status of the zonular fibers [33]. Sometimes gonioscopy is also necessary.
- 5.
Posterior segment examination
EL is often associated with retinopathy; thus, a retinal examination should also be performed.
- 6.
Biological measurement of the eyeballs
Axial length measurements using A-scan ultrasonography or IOLMaster, keratometry using a keratometer or IOLMaster, and corneal diameter and anterior chamber depth measured by IOLMaster are all obtained to evaluate the pediatric patient’s status of eye development.
- 7.
Ultrasound biomicroscopy (UBM)
UBM enables a more detailed examination of the anterior segment, including the zonule, the lens, the anterior chamber angle, and the ciliary body, providing extra details compared to slit-lamp examination alone. This information is essential for the diagnosis and treatment of EL.
- 8.
Systemic examination
Congenital EL may be associated with concurrent abnormalities in other organ systems such as the cardiovascular, musculoskeletal, and nervous systems. Cardiovascular diseases are often insidious and therefore have a high mortality rate. 60–80 % of patients with Marfan syndrome have aortic dilation, and 82 % of them have mitral valve prolapse [34–36]. Children with binocular EL should undergo systemic examination and echocardiography, lumbosacral magnetic resonance imaging (MRI), and chest X-ray or chest CT that sometimes can lead to the timely detection of comorbidities and ensures the safety of ophthalmic surgery. Early systemic intervention and monitoring are beneficial to enhancing patients’ survival and improving their quality of life.
17.4 Treatment of Ectopia Lentis in Children
The treatment of pediatric EL includes nonsurgical and surgical approaches. With current advances in techniques and equipment for cataract surgery, the surgical treatment of pediatric EL has improved significantly, but it still carries a greater risk when compared with routine cataract surgery. Radical surgery may result in adverse consequences, including blindness. Determination of treatment options for children should be comprehensively considered based on the severity of lens opacity and the range of zonular abnormalities, visual functions of both the affected and the fellow eye, other ocular conditions, as well as the patient’s age, the availability of surgical instruments, and the surgeon’s experience.
17.4.1 Nonsurgical Treatment
At present, most surgeons recommend observation with regular follow-up for patients with transparent crystalline lenses and mild EL without complications. Because the affected children are at a critical stage of visual development, if the myopia and astigmatism caused by EL are not corrected in time, visual development will be disrupted [37–39]. The mild ametropia caused by EL can be corrected with spectacles; when there is anisometropia, contact lenses can avoid interocular disparity of the image size. For some children who see through the aphakic pupillary zone, spectacles may achieve an unexpectedly favorable visual outcome [40]. The amblyopia caused by EL requires refractive correction combined with occlusion and visual training, and these should be managed in a timely manner [41]. Children with EL who undergo nonsurgical treatment should adhere to a long-term follow-up schedule and receive regular examinations with pupil dilation, so as to determine whether the EL is progressing. Refraction should also be performed at the same time, and new spectacles are prescribed if there are changes in the refractive status. This prevents the risks of alternate fixation, strabismus, and amblyopia, preserves binocular vision and stereopsis, and improves overall visual quality. When the outcome of conservative treatment is poor or complications occur, reassessment should be conducted, and new treatment options should be formulated.
17.4.2 Surgical Treatment
17.4.2.1 Surgical Indications
There is no unified standard regarding the timing of surgery for pediatric EL. It is generally considered that when EL seriously impairs vision and quality of life of the pediatric patient and conservative treatment has been ineffective, surgical intervention should be adopted.
Detailed indications are as follows:
- 1.
Significant double vision is present due to EL, which cannot be corrected by spectacles [42].
- 2.
- 3.
The lens equator is at the pupil center and results in ametropia that is difficult to correct [36].
- 4.
Significant opacification develops in the dislocated lens, which impairs visual function.
- 5.
Serious complications occur such as secondary glaucoma, corneal endothelial decompensation, and retinal detachment.
17.4.2.2 Surgical Techniques for Lens Extraction
Most displaced lenses in children have a soft nucleus. Lens extraction for pediatric EL is performed by either an anterior or a posterior approach. The anterior approach employs a corneal, limbal, or scleral incision. The operation is relatively simple and posterior irrigation is not required. This avoids entry through the pars plana, which is not fully developed in children. It also reduces disturbance to the vitreous and retina and therefore is more popular in the surgery for pediatric EL. Phacoaspiration is the mainstay surgical technique for pediatric EL, but in the case of severe EL, or in an under-equipped clinical setting, intracapsular lens extraction or manual irrigation/aspiration of the lens is still performed [37]. The posterior approach works through pars plana incisions, and the surgeon can manage the vitreous and retinal lesions after lens removal. The major technique is the pars plana lensectomy (PPL) and requires that the surgeon is familiar with vitreoretinal surgery [37]. It is recommended that an appropriate surgical technique is selected based on EL severity, availability of surgical equipment, and the surgeon’s experience.
Intracapsular Lens Extraction
Intracapsular lens extraction is indicated for almost complete dislocation with the lens visible in the pupillary area or lens dislocation into the anterior chamber. Typically, a modified superior scleral tunnel incision is made, and its size is selected based on the diameter of the lens and rigidity of the nucleus. Ophthalmic viscosurgical device (OVD) is injected both anteriorly and posteriorly to the lens to protect the corneal endothelium and the vitreous. The entire lens is delivered directly out of the capsule using an irrigating lens loop. Vitreous strands in the anterior segment are removed completely. This technique requires a large incision and is associated with a high risk of complications. Therefore, for pediatric EL with a soft nucleus, intracapsular lens extraction is gradually being replaced by the following techniques that use smaller incisions.
Manual Irrigation/Aspiration of the Lens
Manual irrigation/aspiration of the lens is indicated for patients with mild to moderate subluxation in the presence of a soft nucleus. A 2–3 mm limbal incision is made, followed by can-opener capsulotomy or continuous curvilinear capsulorhexis (CCC) and the subsequent hydrodissection. A Simcoe cannula is used for cortex aspiration. Caution should be exercised to maintain the balance between irrigation and aspiration and the anterior chamber depth (ACD) during surgery. OVD tamponade on the capsular bag may be used to avoid its aspiration. If vitreous prolapse occurs, the prolapsed vitreous should be eliminated first, before continuing with lens cortex aspiration. This technique preserves the capsule and enables in-the-bag implantation of the IOL. It does not require a phaco machine and therefore is still used in developing countries.
Lensectomy via Anterior Approach
Lensectomy via anterior approach is indicated for soft-nucleus lenses that are subluxated or dislocated into the anterior chamber. An anterior vitreous cutter is introduced through a corneal, limbal, or scleral incision of ≤ 3.0 mm for lensectomy.
Phacoaspiration
Phacoaspiration utilizes the quick and stable irrigation and aspiration modules of a phaco machine. Lens material is removed through a corneal or limbal tunnel incision of less than or equal to 3.0 mm. The incision for this technique is small and the complication rate is low. The use of CCC, together with iris retractors, capsular hooks or capsular tension ring (CTR), greatly improves surgical safety. The surgical procedure is described below.
Pars Plana Lensectomy
Pars plana lensectomy is used for severe EL or when the lens has dislocated into the vitreous cavity. At present, a 23-gauge vitrectomy system is commonly used to perform 3-port pars plana lensectomy and vitrectomy. If a retinal tear or degenerative lesion exists, photocoagulation or other vitreoretinal surgical techniques may be conducted in the same surgery [43].
17.4.3 Phacoaspiration
Phacoaspiration is currently the preferred technique for lens subluxation. It is a closed-chamber procedure and thus reduces the risk of vitreous prolapse [44]. The zonular fibers in congenital EL are sparse and overstretched, but none or only a small proportion of the fibers are ruptured. The intact zonules and the capsule can be used as a barrier protecting the anterior vitreous. The nucleus and cortex of the lens are removed before management of the capsule. The zonules in traumatic EL are often broken and may be associated with prolapsed vitreous in the anterior chamber. In such cases the vitreous strands in the anterior chamber should be dealt with first, before removal of the crystalline lens.
17.4.3.1 Surgical Technique
Incision Construction
Because the posterior chamber pressure in children is high and iris prolapse occurs more often, a tunnel incision is typically/usually used. At present, it remains controversial over the selection of incision locations for pediatric EL. Vasavada et al. [45] recommend a temporal clear corneal incision, while Cionni et al. [44] recommend the incision should be away from the zone of zonular weakness. In our experience, for children with congenital EL where the zonules are stretched but not broken, the area of zonular weakness is selected for a clear corneal tunnel incision of ≤3.0 mm to facilitate management of the part of the lens behind the iris; for children with traumatic EL with ruptured zonules and perhaps vitreous strands in the anterior chamber, an incision is made in the area of intact zonules to prevent vitreous prolapse out of the incision interfering with lens aspiration. For children less than 9 years of age, a superior scleral tunnel incision is recommended.
Capsulorhexis
The pediatric capsule is highly elastic, and the loose or ruptured zonules give rise to reduced tension on the capsular bag, which makes capsulorhexis more difficult. To tackle this problem, it is suggested that the surgeon use OVD to dilate the pupil and then slowly inject OVD to the part of lens equator with zonular weakness/rupture. These maneuvers fully expose the lens and restore lens centration for capsulorhexis, thus protecting the residual zonules and anterior hyaloid membrane. If there are numerous vitreous strands in the anterior chamber, anterior vitrectomy is performed first. A cystotome is used to create a flap on the anterior capsule in the area with intact zonules. A cystotome or capsulorhexis forceps are used to complete a CCC of 4.5–5 mm. A capsulotomy device using radiofrequency diathermy can also be applied to complete capsulorhexis [46]. Gentle maneuvers are preferred to prevent further disturbance or damage to the zonules and vitreous. For significant lens subluxation, capsulorhexis can be completed with the assistance of iris retractors and capsular retractors. Depending on the area of zonular weakness and rigidity of the nucleus, one to four iris retractors are used to hold the capsular bag at the pupillary center. Capsulorhexis is performed with timely adjustment of the traction by retractors. Overstretching of the capsular bag may lead to rupture of the capsule (Fig. 17.5). Capsule staining can be applied to increase visibility of the capsular membrane.
Fig. 17.5
Capsulorhexis. (a) Two iris retractors are implanted. The anterior capsule opening of the lens is engaged, and the capsular bag is fixed. (b) Capsulorhexis is completed with the assistance of iris retractors
Hydrodissection and Hydrodelineation
The displaced crystalline lens in children lacks normal zonular tension; therefore, surgical maneuvers should be as gentle as possible to avoid pressure on the lens during hydrodissection and hydrodelineation. Multiple injections of small volumes of fluid may be applied and OVD may be used if necessary. The cortex and capsular membrane should be separated to reduce traction on the capsular membrane during subsequent removal of the cortex. In addition, when the lens has a hard nucleus, it should be completely separated. However, excessive rotation of the nucleus should be avoided because it may aggravate the damage to the zonules.
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