Management of paediatric cataract
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Paediatric cataracts can be congenital or acquired. Congenital cataract is one of the treatable causes of blindness in children. Acquired cataracts could be due to trauma, inflammation or other pediatric ocular diseases. Management of a cataract in a child is different from adults because of the anatomically younger ocular tissues, continuous ocular growth and other associated structural anomalies. Management can be challenging for a surgeon intra-operatively as well as post-operatively because of potential immediate and long term complications and the necessary long term follow up required for adequate management of associated amblyopia.
Age appropriate visual acuity testing to assess visual function helps establish the significance of the lens opacification on visual development and amblyopia.
• In preverbal children- assessment of ability to fixate and follow light or objects, response to optokinetic nystagmus (OKN) drum rotation, preferential looking test such as teller’s acuity card, patterned visual evoked potential (VEP), resistance to occlusion of either eye
• In verbal children- optotypes charts such as Allen pictures, LEA symbols
Evaluation of strabismus and nystagmus-
Strabismus common in patients with congenital cataracts, with variable incidence ranging from 26% to 78.9%, with higher rates in cases of bilateral congenital cataracts . Similarly, nystagmus is noted in nearly 24.2 % of patients with congenital cataract. Presence of amblyopia emphasizes the visual deprivation and significance of the cataract and suggests prompt surgery, ideally prior to onset of nystagmus.
Anterior and posterior segment examination-
A full exam must be done in detail before surgery for both congenital and acquired cataracts. Important points of the exam include:
• Examination with hand held slit-lamp, especially in infants
• Examination under anesthesia (EUA) is often required
• Measurement of corneal diameter
• Measurement of intraocular pressure
• Dilated fundus examination to look for persistant fetal vasculature ( PFV /PHPV) or any other posterior abnormalities
• B-scan ultrasound if fundus is not visible. US helps to rule out persistant fetal vasculature, retinal detachment, retinoblastoma or fundal coloboma.
• Measurement of axial length and anterior chamber depth (ACD) using A-scan
• Keratometry (details as described below).
Biometry and IOL power calculation-
Due to the continuous growth of the eyes after surgery and the difficulty in obtaining parameters required for IOL calculation in younger children, IOL power calculations are a challenging task in paediatric age group. Accurate measurement of all the parameters for IOL calculation can often only be obtained when a child is sedated or anaesthesized with general anaesthesia. Full sedation during an EUA allows for a thorough exam, including gonioscopy, corneal diameter measurement, retinoscopy, etc.
• Axial length(AL)- Axial length at birth is 17–17.5 mm approximately. It increases rapidly in the first 6 months (0.46 mm/month), then has a relatively slower (infantile phase) growth (0.15 mm/month) till 18 months, followed by a slow (juvenile phase) growth (0.10 mm/month). It can be estimated with both immersion A‑scan and indentation A‑scan.
• Keratometry - Keratometry values are obtained using auto keratometer. Keratometry also steeply reduces in the first 6 months (−0.40 D/ month), −0.14 D/month in the next 6 months, and − 0.08 D/month in the second year, reaching the adult range at about 3 years of age.
Optical biometer- can be used to calculate AL and keratometry in older children.
• IOL power calculation- The IOL power depends on various factors which include the age of presentation, morphology of cataract, visual acuity at presentation, time of development of cataract (congenital/developmental), biometry at presentation, unilateral or bilateral cataract, and refractive status of the fellow eye. IOL can be implanted in eyes with AL >17 mm and corneal diameter >10 mm. As the eyes grow, a myopic shift is expected. To compensate for this change, a goal for the immediate post operative period of moderate hyperopia is desired.
Methods commonly used to undercorrect the IOL power-
a. According to Dahan and Drusedau undercorrection of 20% in children <2 years and 10% in children between 2 and 8 years
b. Prost suggested 20% undercorrection between 1 and 2 years of age, 15% undercorrection between 2 and 4 years, and 10% between 4 and 8 years of age.
c. Enyedi suggested postoperative target refraction to be used for IOL power calculation according to age (age + postoperative refraction = 7)
Apart from routine blood check up for anaesthetic and operative purpose other tests are specific and chosen according to history and morphology of cataract. A thorough history of prenatal period with history of fever, rashes in mother helps to get a clue about intrauterine infectious causes and advising adequate investigations accordingly. Other important history to elicit which will further help in diagnosis are consumption of any drugs or alcohol, history of trauma during delivery, preterm delivery (retinopathy of prematurity), failure to thrive, and vomiting (galactosemia). Various laboratory tests in bilateral cataract includes-
• Blood sugars
• TORCH titers
• Venereal Disease Research Laboratory (VDRL) test
• Red cell galactokinase
• Serum Calcium and phosphorus
• Urine analysis for reducing substances and amino acids
• Newer tests- Advances in DNA sequencing technologies, so-called Next Generation Sequencing (NGS) not done commonly but is seen as a future testing to improve the diagnosis of congenital cataract especially for genetically heterogeneous conditions.
A unilateral cataract doesn’t require extensive work up as most of them are isolated, non hereditary with no systemic and genetic abnormality.
General systemic evaluation-
Non surgical treatment-
Non- surgical treatment-
Indication- for visually insignificant cataract as follows-
• Cataract < 3mm
• Peripheral or paracentral cataract not obscuring the visual axis or vision
• Blue- dot cataract which is not afftecting the vision
• Presence of good red glow in distant direct ophthalmoscope
• Absence of strabismus or nystagmus
• Observation with careful regular monitoring to look for any change or progression in cataract and/ or development of amblyopia. In either of case, the treatment has to be converted into surgical.
• Dilating drops- can be used to increase the pupil size and making child use the part of clear zone. But strong cycloplegic drops should be avoided as they can cause loss of accommodation and can lead to amblyopia by themselves.
• Occlusion of other eye is useful in case of unilateral cataract, for few hours to prevent amblyopia until surgery is completed.
Indication for surgery-
• Any cataract that is visually significant: >3mm central opacity, centrally obscuring posterior pole , with strabismus or nystagmus
Timing of surgery-
• Unilateral cataracts should be operated on as early as possible between 4- 6 weeks of age. Operating a child before 4 weeks increases the risk of complications of general anaesthesia and increases the risk of aphakic glaucoma and operating after 6 weeks increases the risk of amblyopia.
• Bilateral cataracts should be operated by 6-8 weeks of age- each eye one week apart. If the child is systemically a high risk case for general anaesthesia, both eyes can be simultaneously operated by an experienced surgeon with completely different set of instruments for other eye.
The choice of anaesthesia depends upon age and systemic condition of patient. Risk and benefits of general anaeshthesia has to be considered. Infants less than 1 month have immature organ systems and thermoregulation system and are at greater risk for post-operative apnea. For older children, of more than 10 years age, who can understand and cooperate for local anaesthesia, peribulbar block with or without sedation can be used.
Surgical steps and consideration-
There are numerous important differences between pediatric and adults eyes to consider during surgery. Pediatric eyes have lower corneal and sclera rigidity, very elastic anterior capsules, soft lenses, and well‑formed vitreous. These factors play a role intraoperatively and warrant slight modifications in various steps of cataract surgery.
• Incision – superior incision is preferred as it is covered by the lid and protected by Bell’s phenomenon in case of any trauma, as children are more prone to trauma than adults. Either scleral or corneal incisions can be made, as the difference in post-operative astigmatism is insignificant. A paracentesis should also be made to aid in cataract extraction and cortical removal. In cases of infants less than 7 months of age who are left aphakic, lens aspiration can be done from paracenteses only.
• Anterior capsule management- An optimal anterior capsulotomy is important to facilitate intraocular lens (IOL) placement in the capsular bag. An ideal anterior capsulotomy should be a continuous curvilinear capsulorrhexis with a round, regular shape that is of adequate size (approximately 5.5-6mm). Capsules of paediatric patients are elastic and hence it is challenging to make a continuous curvilinear capsulorrhexis. Trypan blue(0.06%) is used to stain the anterior capsule for good visualization. Trypan also reduces the elasticity of capsule which aids in making a continuous capsulotomy. Anterior capsulorhexis is completed with the help of a cystitome or bent needles, utratas, intravitreal 23G forceps or Intraocular capslorrhexis forceps. Other methods of performing anterior capsulotomy in paediatric population are vitrectorhexis with low aspiration and high cut rate with the vitrectomy cutter. This technique is especially useful if IOL placement is not planned. The disadvantage of vitrectorhexis is that the irregular edges created by this method can lead to unanticipated tear of capsule. Radio-frequency diathermy and Fugo plasma blade have been also advocated for anterior capsulorhexis but have same disadvantages as vitrectorhexis. Femtosecond laser can be employed for both anterior and posterior capsulotomy with good precision and decreased corneal endothelial damage. However, its not cost-effective and may have micro- irregular edges. Studies that analyzed pediatric anterior capsulotomy techniques in the porcine model and found that manual capsulorhexis produced the most extensible capsulotomy with the most regular and stable edge. Precision pulse capsulotomy has also been shown to create well-centered and strong capsulotomies in a pediatric age-group.
• Hydrodissection – should be minimal, gentle and in all quadrants. Inadvertent excessive hydrodissection in patients with pre-existing posterior capsular rupture (PCR) can lead to drop of lens matter in vitreous cavity
• Lens aspiration- the lens in paediatric cataract is generally soft. After adequate hydrodissection, gentle lens aspiration can be performed using automated lensectomy techniques or manually with a simcoe cannula or irrigation-aspiratopn cannula from a limbal route. A pars plana approach is also acceptable, especially when IOL implantation is not planned.
• Posterior capsulotomy- performed in children less than 6 years of age to prevent post op visual axis opacification (VAO). It can also be also be performed in children older than 6 years (with developmental delay or with nystagmus) who may not cooperate for laser capsulotomy on a slit lamp later. Techniques to perform posterior capsulotomy are similar to anterior capsulotomy including capsulorhexis using forceps, vitrectorhexis, radio-frequency Endodiathermy and Femtosecond laser assisted capsulotomy . The size of posterior capsulotomy is made 1-2mm smaller than the anterior capsulotomy.
• Anterior vitrectomy- It is done when there is break in anterior vitreous face due to posterior capsulotomy or in attempts to prevent VAO by breaking the scaffold for proliferating lens epithelial cells (LECs) and metaplastic pigment cells. Additionally, in younger children, post-operative inflammation causes a fibrous reactionary membrane over an intact anterior vitreous face, leading to VAO. A thorough anterior vitrectomy is often done in children of less than 6 years old following posterior capsulotomy. Vitrectomy can be performed through anterior route or pars plana route depending on surgeon’s preference.
• Lens implantation- IOL implanatation is the primary mode of visual rehabilitation in children more than 1 year of age. In younger children, especially in infants it is almost impossible to predict the adequate IOL power because of their fast growing eyes and change in parameters. In a multicenter, randomized clinical trial done by The Infant Aphakic Treatment study, it was found that compared to infants with no IOL after cataract removal, patients treated with primary IOL implantation prior to 7 months of age had more adverse events and required more additional intraocular surgeries over the first five years following surgery for unilateral congenital cataract, with most occurring during the first postoperative year. IOL placement in the bag is most preferred site, though IOL can be placed in ciliary sulcus when posterior capsular support is inadequate. Infants who are left aphakic are planned for secondary IOL later and until that time visually rehabilitated with glasses or a contact lens.
• Preferred IOL material- Acrylic hydrophobic foldable IOLs have unique benefits in children due to increased biocompatibility. There is less chance of postoperative inflammation and posterior capsular opacification with this type of IOL. Due to its foldability, it can be inserted through a smaller incision than PMMA lenses. PMMA (polymethylmethacrylate) lenses also have good biocompatibility but are not foldable and large incisions are required for insertion. In terms of safety profiles, studies have shown that primary implantation of PMMA in paediatric cataract surgery is comparable to acrylic IOLs. Due to their low expense, PMMA lenses are commonly used in developing countries. Many PMMA lenses are also useful for in-sulcus implantation or for optic capture with haptic in sulcus when thin capsule rim cannot support the optic of the lens.
• Closure of wound- After completion of surgery and thorough washing of viscoelastic from anterior chamber, the wounds are sutured using 10-0 suture, often nylon or vicryl. Vicryl has the advantage of dissolving and not requiring surgical removal, but can be more inflammatory.
a. Wound leakage
b. Iris or vitreous incarceration in wound
c. lOL/iris capture
d. Post-operative inflammation
e. Post operative increased IOP
f. Vitreous haemorrhage
g. Retinal haemorrage due to low IOP
h. Retinal detachment
i. Post-operative endophthalmitis
a. Secondary glaucoma- due to postoperative inflammation or structural and anatomical damage as a result of surgery. The incidence of secondary glaucoma is found to be higher in aphakic patients, history of surgery within the first month of life, children with family history of aphakic glaucoma, persistent fetal vasculature syndrome, and nuclear cataract. The risk of developing glaucoma is life-long; hence, regular monitoring of IOP is prudent.
b. Visual axis opacification(VAO)- if not detected and managed can cause amblyopia. Apart from posterior capsulotomy and anterior vitrectomy, some surgeons prefer optic capture in the posterior capsulotomy (also known as posterior optic button hole) to prevent lens epithelial cell migration and VAO. In cases of VAO, immediate treatment with Nd:YAG laser capsulotomy under general anesthesia or surgical capsulotomy should be performed.
c. Retinal detachment- Its rare but there is life long risk of RD in these patients, especially with PFV. Life-long monitoring with regular dilated fundus examinations is required.
Post operative treatment-
• Post operative inflammation is more pronounced in paediatric cataract surgery due to the immature blood aqueous barrier. Patients are typically prescribed topical steroids (example: prednisolone acetate 1% six times/day) and cycloplegics (example: homatropine 2%) postoperatively along with antibiotic drops. Steroid drops are tapered over a period of 6-8 weeks. Patient is followed up frequently up to 1 month and every 3 monthly thereafter.
• Visual rehabilitation – in the form of glasses. or contact lenses to correct post operative refractive error. These should be started as soon as possible. Treatment of amblyopia with occlusion therapy should also be implemented early.
Paediatric cataract surgery is challenging but has evolved tremendously. After thorough preoperative work- up, the standard treatment of significant paediatric cataracts is lens aspiration with anterior vitrectomy and primary or secondary IOL implantation. The management of this condition requires proper post-operative visual rehabilitation with correction of post operative refractive error and treatment of amblyopia with patching. Life-long follow-up is required so as to monitor for any late complications and to treat them adequately.
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