Fig. 17.1
Optic disc asymmetry with thinning of the neuroretinal rim in the right optic disc in comparison to the left optic disc
Cornea features: Haab’s striae, enlarged corneal diameter (≥11 mm in newborn, > 12 mmHg in a child under 1 year of age, > 13 mHg at any age);
Refractive error: progressive myopia or myopic shift coupled with an increase in ocular dimensions out of keeping with normal growth;
Visual fields: Reproducible visual fields defect consistent with the glaucomatous optic disc findings with no other observable reason for the field defect.
17.3.1 Suspected Glaucoma
Glaucoma may be suspected when the constellation of features is incomplete, e.g. the presence of increasing ocular dimensions in the absence of raised IOP, or the presence of raised IOP without any other features of glaucoma. These children require close monitoring over time before a diagnosis of glaucoma can be made or excluded.
17.4 Incidence and Onset
A recent multicenter prospective study reported the incidence of glaucoma following cataract surgery to be 10 % in the first year of monitoring, with cases arising in both aphakic and pseudophakic eyes [2, 3]. A retrospective review of 165 cases in the UK reported an annual incidence of glaucoma following cataract surgery to be 5.25 per 100 surgeries [8], whilst another from Australia reported an incidence of 3.9 per 100 person years [9]. Glaucoma is therefore a frequent complication of cataract surgery and the risk is life-long [2, 3, 8–13].
17.5 Mechanisms of Glaucoma
In the majority of cases there are no pre-operative gonioscopy features to indicate the pathogenesis of glaucoma [13] and removing the lens has a direct role in the development of glaucoma [14]. The two main mechanisms of glaucoma are:
Open angle (>180° is open)
Closed angle (<180° is open), associated with either
acute pupil block, or
progressive peripheral anterior synechiae (PAS) formation.
17.6 Pathogenesis of Open Angle Glaucoma Following Paediatric Cataract Surgery
Open angle glaucoma is the commonest mechanism, and may present at any time following surgery. The pathogenesis is poorly understood but may include the following:
Trabecular meshwork (TM) dysfunction from inflammation and cellular obstruction
Insult to developing angle structures from interaction with lens epithelial cells or vitreous leading to reduced outflow facility and or developmental arrest [15]
TM collapse from lack of ciliary body traction
Postoperative inflammation with damage to the trabecular meshwork, which may then progress to angle closure
17.7 Pathogenesis of Closed Angle Glaucoma Following Paediatric Cataract Surgery
Angle closure mechanisms may occur either acutely with pupil block, or with progressive formation of PAS secondary to post-operative inflammation. It generally presents early following surgery.
17.8 Risk Factors for Developing Glaucoma Following Cataract Surgery
Risks due to pre-existing ocular features should be identified prior to cataract surgery, whilst risks directly related to the surgery may be mitigated with meticulous surgical technique and careful postoperative management.
Microcornea carries a significant risk of post-operative glaucoma [2, 3, 8, 12, 18, 23] both open and closed angle. In one study of 48 eyes with aphakic glaucoma 45 (94 %) were found to have microcornea [23].
Persistent foetal vasculature may carry additional risks of glaucoma although the evidence is conflicting [2, 3, 24].
Intra–ocular lens placement: The risk of developing glaucoma following intraocular lens implantation has generated much debate. An initial report that the presence of an intraocular lens was protective for the development of glaucoma [25] was also supported by a large multicenter meta-analysis [26]. However, selection bias potentially contributes to the lower rate of glaucoma in pseudophakic infants reported in these studies as lens implantation in infants less than 12 months old occurs in only a few selected cases. Three studies have reported that an intraocular lens is not protective for the development of glaucoma [2, 4, 5]. The recent 5 year outcome from the Infant Aphakia Treatment Study found no difference in glaucoma rates between the two groups [3]. Modern surgical techniques do not eliminate the early development of glaucoma following congenital cataract surgery with or without an intraocular lens implant [2]. These studies highlight the need for lifelong surveillance for glaucoma.
Hypotony is a sight threatening complication, which increases the risk of glaucoma. It is often associated with a shallow or flat anterior chamber, and if left untreated, may result in either PAS with angle closure glaucoma, or more seriously, aqueous misdirection. Per-operative steps to avoid hypotony include the use of an anterior chamber infusion and ensuring all surgical wounds are securely sutured to avoid aqueous leaks. Postoperative cycloplegia helps to maintain a deep anterior chamber and therefore minimizes the risk of PAS formation and aqueous misdirection.
Postoperative inflammation may directly damage the functionality of the trabecular meshwork, or may lead to PAS with angle closure, or an occlusive pupillary membrane leading to pupil block glaucoma. Inflammation may be minimized by meticulously removing all the lens material, avoiding unnecessary iris surgical trauma, using intra-cameral heparin [27, 28] and subconjunctival steroid at the end of the procedure. Postoperative frequent topical steroids (e.g. dexamethasone three to four times a day as a starting point) should be used, supplemented if necessary with further peri-ocular steroid injections.
17.9 Assessment and Monitoring for Glaucoma
The glaucoma risk is lifelong [2, 3, 10–13] so monitoring should continue indefinitely, and should be aimed at early detection before vision has been affected, and before the child becomes symptomatic.
17.9.1 History
The child’s caregivers, may identify features of raised IOP including: photophobia, lacrimation, blepharospasm, intolerance of contact lens, visible enlargement of the globe, dull corneal reflex (sometimes described as a change in colour of the child’s eye by the parents), poor sleep pattern, signs of distress, refusal to feed and failure to thrive. These symptoms and signs are related to enlargement of the globe and corneal oedema. Observation of the child in the clinic setting will also often elicit many of the above signs.
17.9.2 Examination
Examination to assess for the presence of glaucoma requires the clinician to be patient and to adjust the techniques used to the age of the child and their level of cooperation (Fig. 17.2). More than one visit may be necessary to obtain all the necessary information. Lowering the ambient lighting levels may assist when photophobia is an issue, and opportunistically examining an infant when they are feeding or sleeping may be helpful.
Fig. 17.2
iCareTM rebound tonometry (Icare Finland Oy Vantaa, Finland) allows regular and frequent clinic intraocular pressure measurements
Modern equipment allows assessment in the outpatients for most children, however it may be necessary to perform an examination under anesthesia to fully determine the glaucoma status. Inhaled anaesthetic agents are associated with a reduction in IOP and measurements need to be taken as early as possible in the induction process with agreement from the anaesthetist. Ketamine does not affect the IOP as dramatically as inhaled anaesthesia but is less frequently used in current clinical practice.
Monitoring should be at intervals chosen according to the perceived risk of developing glaucoma and according to breadth and accuracy of the possible assessments at each visit. Assuming the ophthalmologist is confident that adequate assessment has been achieved, and there is no evidence of glaucoma, some experts have suggested the following monitoring review intervals: 1 week and then 1 month following cataract surgery and then 2–4 month review; thereafter high risk cases may be monitored at 2–4 monthly intervals and low risk 6–12 monthly intervals [29]. However, when development of glaucoma is suspected, or when full assessment has not been possible earlier review must be considered (Table 17.1).
Table 17.1
Examination features and techniques
Test | Features | Equipment | Notes |
|---|---|---|---|
Visual Acuity | Sequential recordings assessing for change | Preferential Looking Cards for pre-verbal children, | |
Matching shapes (Kay Pictures) for toddlers, | |||
Matching letters (HOTV, or Sheridan Gardner) pre-school age | |||
Snellen charts with single or linear letters or LogMAR visual acuity charts for school aged children | |||
Intra-ocular pressure (IOP) | Sequential recordings: Accuracy may be affected by corneal thickness, off-axis measurements, corneal scarring, lid squeezing, breath holding, crying, and use of a speculum or fingers to hold the lids. | Goldmann applanation tonometry (GAT) GAT may be performed by Perkins tonometer | GAT is the reference standard for IOP measurement |
Other methods: iCareTM rebound tonometer Pneunotonometry TonopenTM | |||
Corneal Assessment | Corneal Diameter | Calipers and ruler estimating to nearest 0.25 mm | Limbal-to-limbal measurement preferably in horizontal meridian. Progressive enlargement may indicate poor IOP control [41] |
Corneal edema | Direct observation | May indicate raised IOP | |
Haab’s Striae | Direct observation | ||
Central corneal thickness (CCT) | Pachymetry | ||
Anterior chamber (AC) assessment | Anterior chamber depth | Redmond Smith method [49], anterior segment OCT, or UBM | |
Iris and pupillary profile | Direct observation | e.g. Bombé with pupil block, or peripheral tenting with PAS formation | |
Inflammation | Direct observation | Inflammation should be graded during monitoring and treatment | |
Angle | Gonioscopy | ||
Additional features: e.g. pupillary membrane, Elschnig pearls, vitreous in the anterior chamber | Direct observation | ||
Optic Disc Assessment | Size, shape, colour, neuroretinal rim configuration, Cup:disc ratio, Nerve fibre layer defects, congenital anomalies | Direct or indirect ophthalmoscopy, imaging e.g. photography, OCT, HRT, GDx | Baseline images should be obtained when possible with further images as and when changes occur. |
Axial length measurement | Sequential recordings particularly up to age of 3 years of age | A-scan or B-scan ultrasound | |
Refraction | Sequential measurements | Retinoscopy or auto-refraction | Myopic shift, often with increased axial length, may be indicative of poorly controlled IOP; reversal of myopic shift may occur with improved IOP control |
Visual Field Assessment | Sequential recordings | Confrontation visual field, or automated visual field testing | Use of automated perimetry to monitor visual field when ability of child allows |
Other investigations that assist in assessment of glaucoma include: anterior segment OCT, ultra-sound biomicroscopy allowing imaging of the ciliary body and angle; B-scan ultrasound to image the posterior pole and exclude other pathology such as retinal detachment or supra-choroidal hemorrhage.
17.10 Management
Management of glaucoma or IOP rise following cataract surgery depends on the mechanism causing raised intra-ocular pressure:
17.10.1 Corticosteroid Induced IOP Rise
Topical corticosteroid therapy is the mainstay treatment for postoperative inflammation following cataract surgery. However steroid induced raised IOP is a significant risk in children. Children have been noted to have a higher frequency, worse severity and shorter time to peak corticosteroid response. Potency and mode of administration of corticosteroids plays a major role in the degree of corticosteroid response [16, 17]. It is important not to compromise the treatment of post-operative inflammation, and the addition of topical glaucoma medications may alleviate the raised IOP.
17.10.2 Pupil Block
Pupil block may occur in the post-operative period as a result of excessive post-operative inflammation and pupillary membrane formation, vitreous, remaining capsule or a proliferating lens fibers occluding aqueous flow through the pupil. Surgical intervention is then required to remove these and a peripheral iridectomy may also be performed as prophylaxis against recurrence of pupil block. Intra-cameral sodium heparin [27, 28] and intensive post-operative topical steroid may help reduce post-operative inflammation. Late pupil block may occur due to secondary lens proliferation [52] or Soemmerring’s ring formation (particularly in smaller eyes), which again is managed with surgical removal (Fig. 17.3).
Fig. 17.3
(a) Ultrasound Biomicroscopy (UBM) of anterior segment of a pseudophakic eye with angle closure. The posterior chamber intraocular lens (IOL) located in the ciliary sulcus (large arrow). Anterior lens capsule (arrow head) and posterior capsule (thin arrow) with secondary lens proliferation (Soemmerring’s ring) between the capsule leaflets. The combination of the secondary lens proliferation and sulcus IOL contribute to the angle closure. (b) Twenty three gauge cutter and infusion cannula removing secondary lens proliferation from under the sulcus placed IOL (same patient as a)
17.10.3 Glaucoma Without Pupil Block
This is the most common presenting form of glaucoma following cataract surgery and in choosing the appropriate management consideration needs to be given to the following:
The underlying cause and ocular characteristics of the glaucoma: Cataract surgery may be the sole cause of the glaucoma and the mechanism may be open angle, or closed angle with peripheral anterior synechiae formation. Alternatively there may be a pre-existent condition associated with glaucoma as the underlying cause e.g. aniridia
The severity of the glaucoma including the level of IOP rise and the magnitude of the associated ocular changes including disc changes, corneal diameter and axial length. Mild to moderate intra-ocular pressure rise with early glaucomatous changes may respond well to topical medication. Advanced glaucoma usually warrants surgical intervention. If buphthalmos is present surgery is more challenging with a greater risk for complications including hypotony.
The intolerance and allergy to topical medications: The dosage of topical medications is not titrated according to body mass, and children may suffer greater side effects from medications than do adults as a result of proportionally greater drug load, and their immature metabolism, blood–brain barrier and excretory systems. Local side effects from topical medication may reduce tolerance particularly when refractive correction is provided in the form of contact lenses. Preservative-free medication may be used in the presence of preservative intolerance or in the presence of a poor corneal surface, such as aniridia.
Family and social factors: The effectiveness of any topical medication depends upon reliable instillation, with adherence to a regular dosing regimen and persistence in the long term. Parents and caregivers should be supported in learning the best method for instilling topical drops, which will vary according to the age and cooperation of the child. In determining a workable drop regimen, consideration must be given to social and family factors and constraints. Surgical treatment may reduce or eliminate the need for topical medications in the medium to long term. However, surgery often carries significant risks, requires a commitment to a more intense topical drop regimen in immediate post-operative period and the need for more frequent hospital visits for post-operative assessment and monitoring in the short term.
Choice of treatment therefore needs to be tailored to the individual child and negotiated with the parents and caregivers with regular review as circumstances change.
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