Ординатура / Офтальмология / Английские материалы / The Pediatric Glaucomas_Mandal, Netland_2006

13.Toker E, Seitz B, Langenbucher A, Dietrich T, Naumann GO. Penetrating keratoplasty for endothelial decompensation in eyes with buphthalmos. Cornea 2003; 22:198–204.

14.Ramchandani M, Mohammed S, Mirza S, McDonnell PJ. Penetrating keratoplasty in adults with congenital glaucomas. Eye 2004; 18:703–708.

15.Holland EJ, Djalilian AR, Schwartz GS. Management of aniridic keratopathy with keratolimbal allograft: a limbal stem cell transplantation technique. Ophthalmology 2003; 110:125–130.

16.Figueiredo RS, Araujo SV, Cohen EJ, et al. Management of coexisting corneal disease and glaucoma by combined penetrating keratoplasty and trabeculectomy with mitomycin C. Ophthalmic Surg Lasers 1996; 27:903–909.

17.Zacharia PT, Harrison DA, Wheeler DT. Penetrating keratoplasty with a valved glaucoma drainage implant for congenital glaucoma and corneal scarring secondary to hydrops. Ophthalmic Surg Lasers 1998; 29:318–322.

Introduction

Ocular hypertension versus glaucoma

Glaucoma after congenital cataract surgery

Mean time interval at onset of glaucoma following surgery

Causes of delay in diagnosis

Mechanism of intraocular pressure elevation and risk factors

Diagnostic clues and evaluation

Treatment

Conclusions

Introduction

Postoperative complications occur more commonly after congenital or infantile cataract surgery compared with adult cataract surgery, and many of these complications do not develop until years after surgery.1 Little has been written about pediatric glaucoma in aphakia and pseudophakia, a recognized complication of congenital cataract surgery.2

Despite improved surgical technique utilizing vitreous cutting instrumentation for lens removal and vitreous management, the incidence of glaucoma following successful cataract removal remains high.3,4

Transient or permanent intraocular pressure elevation occurs in aphakic and pseudophakic eyes as a result of one of several mechanisms, or it can be due to a combination of several causative factors. Hence, the use of the term ‘aphakic glaucoma’ is generally discouraged because it implies that the state of aphakia as such is the only cause of glaucoma, which is not observed in clinical practice. This group of glaucomas may be described as ‘glaucomas associated with aphakia and pseudophakia’ or ‘the glaucomas in aphakia and pseudophakia,’ which conveys the notion that multiple mechanisms contribute to the development of elevation of the intraocular pressure after congenital cataract surgery (Fig. 14.1).

glaucoma. Patients who have increased intraocular pressure without apparent disc damage must be examined for disc damage and cupping over time, without the benefit of visual field testing.

Egbert and coworkers5 conducted a prospective glaucoma evaluation to discover the prevalence of glaucoma and ocular hypertension in a group of pediatric subjects who underwent an automated lensectomy and anterior vitrectomy for congenital or pediatric cataracts during a nine-year period. The diagnosis of glaucoma required the intraocular pressure to be greater than 21 mmHg and the optic nerve head to have a cup-to-disc ratio greater than 0.5 or an asymmetry between optic nerve heads greater than or equal to 0.2. A diagnosis of ocular hypertension required the intraocular pressure to be greater than 21 mmHg with an absence of optic nerve abnormalities. In this study, the prevalence of glaucoma and ocular hypertension was 9.7% and 33%, respectively.5

Retrospective studies reporting the occurrence of glaucoma after surgery for congenital or pediatric cataract are limited by a short or undefined postoperative and follow-up periods. Most of these studies have not consistently stated the criteria

Ocular hypertension versus glaucoma

The difference between ocular hypertension and glaucoma is poorly understood in patients with aphakia and pseudophakia following surgery for congenital or infantile cataract. Children may not be able to perform visual field testing, which may preclude the use of this important diagnostic criteria for

Figure 14.1 Elevated intraocular pressure associated with aphakia. This infant had Lowe’s syndrome (oculocerebrorenal syndrome). A contact lens has been placed to correct the large refractive error.

for glaucoma, or define glaucoma as an intraocular pressure of 21 mmHg or greater on more than one occasion. Few authors have differentiated ocular hypertension and glaucoma.5–7 The importance of carefully defining the criteria for glaucoma is shown by the large increase in the prevalence of glaucoma in the study by Egbert and coworkers if they had defined glaucoma as intraocular pressure of 26 mmHg or greater.5 Glaucoma would have been diagnosed in 10 additional subjects, thus increasing the prevalence of glaucoma to 26% of their patient population, instead of 6 (9.7%) of 62 subjects found to have glaucoma defined as elevated intraocular pressure with glaucomatous optic nerve damage.

Glaucoma after congenital cataract surgery

Glaucoma is a well-recognized consequence of congenital cataract surgery. In a review of early literature on pediatric aphakia performed between 1943 and 1975, Francois8 found an average prevalence of glaucoma of 5.5%, with some authors reporting a prevalence up to 13–14% (Table 14.1). It was noted that glaucoma may not be recognized until years after cataract removal. These reports were prior to modern microsurgical techniques, including automated lensectomy and vitrectomy.

During the 1970s, microscopically controlled, automated lensectomy and vitrectomy gradually replaced one and twostaged needling as a method of pediatric cataract extraction. Lensectomy and vitrectomy remain the most commonly used technique. It was hoped that by removing lens and capsular remnants more effectively, this surgical approach would minimize postoperative inflammation and pupillary block, and would decrease the incidence of glaucoma.

A study reporting the initial experience with this technique was encouraging, with no cases of glaucoma reported.9 In

Table 14.1 Secondary glaucoma after congenital cataract surgery, prior to automated vitrectomy and lensectomy

Adapted from Francois J. Late results of congenital cataract surgery. Ophthalmology 1979; 86:1586–1589.

Table 14.2 Glaucoma after congenital cataract surgery, using automated vitrectomy and lensectomy

a longer follow-up study, Keech and associates10 found an 11% prevalence of glaucoma after lensectomy and vitrectomy. Subsequent studies reported prevalence of glaucoma ranging from 6% to 26% (Table 14.2).3–5,9–13 The reported incidence varies with the duration of follow-up after cataract surgery. A longer follow-up period has been associated with a higher prevalence of glaucoma.52

In a study by Simon and coworkers,3 with glaucoma defined as intraocular pressure of 26 mmHg or greater, glaucoma was diagnosed in eight (24%) eyes of seven (27%) children. Visual field and optic disc analysis in their patient population was difficult. The intraocular pressure ranged from 26 to 50 mmHg (average 34 mmHg) in patients with glaucoma. Glaucoma was found more commonly among children followed for more than 60 months and was diagnosed up to 105 months after surgery.3 Of the 17 eyes that were followed for at least 5 years after surgery, 7 (41%) had glaucoma. The authors commented that the relatively high proportion of glaucoma in their patients may reflect, in addition to their longer period of follow-up, the directed glaucoma examination they receive. They also stated that more of their patients may be diagnosed with glaucoma in the future.

Mills and Robb13 followed 125 eyes of 82 patients who underwent cataract surgery before the age of 10 years. Glaucoma developed in 13 (15.8%) of them from 5 months to 13.1 years after surgery. The authors projected a 30% prevalence of glaucoma at 13 years after cataract extraction. Asrani and Wilensky2 found glaucoma in 42 eyes (65.6%) after 10 years of age, with an average interval of 12.2 years between cataract surgery and the diagnosis of glaucoma.

Mean time interval at onset of glaucoma following surgery

Glaucoma may occur in either an acute or chronic time course. Acute glaucoma may be due to angle closure and usually presents in the early postoperative period. Lens remnants or vitreous block may prevent aqueous flow through the pupil, inducing iris bombe. In the study reported by Vajpayee and

coworkers,14 the duration between intraocular lens implantation and initial manifestations of pseudophakic pupillaryblock glaucoma varied between 12 and 16 days (mean ± standard deviation, 14 ± 2 days). Current surgical approaches more completely remove the lens and anterior vitreous, making this complication rare. Chronic angle-closure glaucoma may manifest months to years after congenital cataract surgery.

Unlike angle-closure glaucoma, which usually develops soon after surgery, open-angle glaucoma is usually not diagnosed until years later. Simon and coworkers3 reported a mean interval of 6.8 years from the time of cataract surgery until glaucoma was diagnosed, while Phelps and Arafat6 reported intervals ranging from two to 45 years.

Parks et al9 reported a mean onset of glaucoma of 5.3 years following congenital cataract surgery. Mills and Robb noted an average time at onset of 7.4 years for the nine patients with open-angle glaucoma in their study.13 Walton analyzed the number of patients who developed glaucoma after selected intervals following lensectomy.15 Forty of the 65 patients were not found to have glaucoma until two or more years after their lensectomy, while 24 of the 65 patients were found to have glaucoma four or more years after lensectomy.

Johnson and Keech16 found that glaucoma developed in approximately one-third of their glaucoma patients within a few months following cataract surgery; while glaucoma developed in the remaining two-thirds several years after surgery. The mean time of onset of glaucoma following surgery in their study was 64.6 months in the persistent hyperplastic primary vitreous cataract group and 47.5 months in the infantile cataract group, which was not a significant difference.

The onset of glaucoma may occur several decades following congenital cataract surgery. Barnhorst and coworkers17 have observed an unusual case of lens-induced glaucoma that occurred 65 years after congenital cataract extraction. The intraocular specimen exhibited lens material, epithelial cells, and macrophages. It may have taken years for the residual lens material to denature and break into small pieces, which resulted in phacolytic and lens-particle glaucoma. This patient appeared to develop lens-induced glaucoma 65 years after congenital cataract surgery.

Chrousos and associates11 found glaucoma in 24 (6.1%) eyes after a variety of surgical techniques. Eighteen cases became apparent after a 3-year follow-up period and 12 became apparent after a 6-year follow-up period. Their finding of no glaucoma after lensectomy and vitrectomy was based on an average 2-year follow-up period. Other studies have shown that glaucoma may continue to develop in aphakic children many years after surgery.3,10

Asrani and Wilensky2 reported results of their retrospective review of patients treated for glaucoma that developed after congenital cataract surgery. In their study, 42 eyes (65.6%) were diagnosed with glaucoma after 10 years of age, and the average interval between the cataract surgery and the diagnosis of glaucoma was 12.2 years. They compared their study with that of Simon and co-workers, who reported a 24% prevalence of glaucoma with a mean follow-up of 6.8 years. Since the average interval between cataract surgery and

diagnosis of glaucoma was 12.2 years, Asrani and Wilensky2 believe studies with shorter follow-up in the literature underestimate the incidence of this complication. However, in their group, a majority of the eyes (n = 37, 57.8%) were found to have glaucoma after an interval of 5 years. In addition, 17 eyes (26.6%) developed glaucoma within 5 years of cataract surgery, and six eyes were found to have glaucoma within 1 year of the cataract surgery.

The prevalence of glaucoma after congenital cataract surgery is high with long-term follow-up. Chen et al52 retrospectively studied 170 eyes of 117 patients with mean ± SD 8.6 ± 7.6 years follow-up. The prevalence of glaucoma after lensectomy was 37.1% at 1 year, 75.9% by 6 years, and 100% by 33 years. Glaucoma can occur at any time after congenital cataract surgery; therefore, pediatric aphakic and pseudophakic patients should be routinely monitored for glaucoma throughout their lives.

Causes of delay in diagnosis

Early diagnosis of glaucoma following congenital cataract surgery may be difficult for a number of reasons. The ability to obtain intraocular pressure measurements, visual field assessment, and careful biomicroscopic examination of the optic nerve head is often difficult or impossible in these young patients. Furthermore, signs of congenital glaucoma such as epiphora, blepharospasm, photophobia, increasing corneal diameter, Haab’s stria, and corneal clouding may not be seen with pediatric glaucoma following congenital cataract surgery. Usually patients with glaucoma are without symptoms despite increased intraocular pressure.

Unless the examining ophthalmologist specifically is looking for glaucoma, the diagnosis is easily missed. As a result, many children may have elevated intraocular pressures for months or years before they are first detected. Frank signs and symptoms, such as redness and pain in the eye, are rare, especially because most of the glaucoma is the open-angle type. The presence of a clear cornea and the lack of ocular congestion gives the ophthalmologist a false sense of security. Also, symptoms such as loss of vision, especially in the unilateral cases, may never manifest or may appear very late in children, and thus the diagnosis of glaucoma may be missed. The existing loss of visual acuity accountable by amblyopia and nystagmus makes it difficult for the ophthalmologist to assess the vision accurately in these children, and early detection of loss of vision caused by glaucoma is problematic.

Glaucoma may threaten the vision of aphakic and pseudophakic eyes many years after congenital cataract surgery. A directed glaucoma evaluation that includes sedation or examination under anesthesia, if required, should be performed in the suggested follow-up schedule.2

Mechanism of intraocular pressure elevation and risk factors

Glaucoma is one of the most common complications of congenital cataract surgery. Both open-angle and angleclosure glaucoma may develop.

Angle-closure glaucoma

In the era when needling was the treatment of choice for congenital cataract, angle-closure glaucoma occurred most commonly in the immediate postoperative period because of swelling of lens material causing pupillary block. This problem was reduced when Scheie popularized the aspiration technique. Pupillary block is also caused by a fibrin membrane extending across the pupil. Less commonly, pupillary block glaucoma may develop secondary to vitreous prolapsing into the anterior chamber. In 1968, while delivering the 24th Edward Jackson Memorial Lecture, Chandler commented that ‘the principal cause of the loss of an eye after congenital cataract surgery is pupillary block leading to peripheral anterior synechia and intractable glaucoma.’18

The incidence of serious postoperative complications including glaucoma following congenital cataract surgery has undoubtedly diminished during the last few decades. Walton19 describes four types of glaucoma following congenital cataract surgery, including pupillary block glaucoma, lens material blockage of the trabecular meshwork, phacolytic glaucoma, and chronic open-angle glaucoma following absorption of lens material. Uveitis also has been reported as a cause of aphakic glaucoma. Modern surgical techniques, including the operating microscope and newer microsurgical instrumentation, have probably all but eliminated the first three causes. Walton’s recent study15 confirms the infrequent occurrence (5 of 80 glaucoma eyes, 7%) of pupillary block glaucoma after congenital cataract surgery and supports the belief that contemporary pediatric aphakic glaucoma is most often an open-angle glaucoma.

In 1979, Francois8 reviewed the world literature along with his own experience on complications associated with cataract surgery in children. He enumerated the causes of angle-closure glaucoma after congenital cataract surgery as shown in Table 14.3. Vajpayee and co-workers14 reported development of pupillary block glaucoma in children after primary intraocular lens implantation in the posterior chamber secondary to iridopseudophakic synechiae. The exact pathogenesis of pupillary-block glaucoma with posterior chamber lenses is not clear and may be related to a number of other factors, including alteration of angle anatomy, forward movement of the vitreous caused by zonular or capsular disruption, pre-existing angle-closure glaucoma, and synechia formation between the lens and the iris or anterior capsule. Post-operative mydriasis, topical corticosteroids and a

B

A

Table 14.3 Causes of angle-closure glaucoma after congenital cataract surgery

1.Uveitis with seclusion or occlusion of the pupil and peripheral anterior synechiae

2.Pupillary block with inflammatory membrane

3.Delayed restoration of the anterior chamber after cataract extraction

4.Vitreous in the anterior chamber or loss of vitreous

5.Epithelial ingrowth in the anterior chamber after cataract extraction

6.Hyphema, intraocular hemorrhage

7.Prolapse of the iris

8.Associated with intraocular lens

Adapted from Francois J. Late results of congenital cataract surgery. Ophthalmology 1979; 86:1586–1589.

peripheral iridectomy are all helpful in reducing the incidence of pupillary block glaucoma in children following congenital cataract surgery.

Less commonly, chronic angle-closure glaucoma may develop in infantile eyes after cataract surgery. Chronic angleclosure glaucoma has been noted to occur less frequently after a lensectomy than after lens aspiration, presumably because the lens cortex is more completely removed. On the basis of clinical history and gonioscopic findings, Walton15 reported pupillary-block glaucoma in three eyes of three children after bilateral lens surgery and in two eyes after unilateral lensectomy. The majority of the children (60 of the 65 children) developed open-angle secondary aphakic glaucoma, rather than angle-closure.

Open-angle glaucoma

According to recent literature, the most common type of glaucoma after congenital cataract surgery is open-angle glaucoma (Fig. 14.2). While Chandler and Grant stressed that pupillary block is the usual mechanism, they mentioned ‘quite exceptional cases’ in which numerous operations for congenital cataract were followed by open-angle glaucoma. Phelps and Arafat6 documented a series of patients with open-angle secondary glaucoma following congenital cataract surgery, and subsequently similar observations were reported by others.

Phelps and Arafat6 reported 18 patients who had undergone operations for congenital cataracts in the past and were

Figure 14.2 Open-angle glaucoma associated with aphakia (A). The eye has microcornea and colobomatous macrophthalmia, and esotropia. Gonioscopy shows an open anterior chamber angle (B).

discovered to have high intraocular pressures. The age at which elevated intraocular pressure elevations was detected ranged from 6 to 56 years, and the interval between the cataract surgery and the diagnosis of glaucoma ranged from 2 to 45 years. The level of intraocular pressure when elevation was first detected ranged from 22 to 42 mmHg. Glaucomatous optic nerve damage was definitely present in six patients, probably present in six more, and questionable in six others. The anterior chamber angles of these patients were open.

In 1983, Pressman and Crouch20 reported three cases of pediatric open-angle aphakic glaucoma. These patients had congenital cataracts extracted by the extracapsular techniques of phacofragmentation or irrigation and aspiration. Each required a secondary membranectomy and had development of glaucoma 6 to 25 months after cataract extraction. Chronic glaucoma was found in 6.1% of the eyes as reported by Chrousos and co-workers.11 Although the majority of the eyes developing glaucoma manifested the complication in 6 or more years after the cataract surgery, two cases manifested glaucoma within the first postoperative year. One-third of the eyes developing glaucoma had a pre-existing ocular abnormality other than cataract. Therefore, possibly some of the glaucomas were destined to become manifest later in spite of cataract surgery. Secondary membrane surgery was performed in 62% of the eyes in which the aspiration procedure left the posterior capsule intact. The secondary membrane surgery itself appeared to increase the risk for development of glaucoma.

Keech and associates10 found an 11% (12 eyes) incidence of glaucoma after surgery for congenital and infantile cataracts. Glaucoma associated with open angles occurred in one eye of the aspiration group and three eyes of the lensectomy and vitrectomy group. Four patients (six eyes) had anomalies of the anterior chamber angle similar to congenital glaucoma. Each eye had a flat iris plane with no angle recess and a poorly defined scleral spur and ciliary body. Prominent iris processes and peripheral iris hypoplasia were present in some cases. According to the authors, anterior chamber angle abnormalities unrelated to cataract surgery may have predisposed to the development of postoperative glaucoma.

Parks and colleagues9 found that aphakic glaucoma of the open-angle-type developed in 26 eyes (14.9%) of 18 patients (15.3%) treated with cataract surgery. Angle-closure glaucoma did not develop in any of the patients in this report. Simon and coworkers3 noted that glaucoma after pediatric (below the age of 11 years) lensectomy and vitrectomy is typically of the open-angle-type and asymptomatic. They speculated that a substance in the vitreous humor diffuses forward and damages the trabecular meshwork following infantile cataract surgery.

There are few reports in the literature documenting that patients with bilateral cataracts who have unilateral aphakia do not usually have bilateral glaucoma, and bilateral aphakia patients do not usually have unilateral glaucoma. Munoz and associates21 reported an infant with familial cataracts in whom bilateral open-angle glaucoma developed shortly after pars plicata lensectomy with anterior vitrectomy. Simon et al3

found that of the seven patients who developed open-angle glaucoma after pediatric lensectomy and vitrectomy, one patient with bilateral asymmetric cataract developed glaucoma in the operated eye but not in the unoperated eye with its partial cataract. This supports the concept that cataract surgery is in some way responsible for the onset of the glaucoma in certain predisposed children with congenital cataracts.

Microcornea has been associated with glaucoma in aphakia and pseudophakia after congenital cataract surgery (Fig. 14.3). In a study by Robb and Petersen,12 late onset of open-angle glaucoma developed in 8 of the 29 patients with extensive lens opacities and early visual impairment. In patients with less severe cataracts and visual impairment, surgery for cataract was performed after three years of age, but no patient developed delayed open-angle glaucoma in this group. Similar observations were made by Mills and Robb,13 who identified an increased relative risk of developing postoperative glaucoma in eyes with microcornea, congenital rubella syndrome, and poor pupillary dilatation with 1% cyclopentolate. Parks and colleagues9 stated that aphakic glaucoma with open angle is related to two types of cataracts: nuclear and persistent hyperplasia of the primary vitreous, both of which are associated with microcornea.

Forty-five of 48 patients (94%) in the study reported by Wallace and Plager22 had microcornea associated with aphakic glaucoma. In this series, seven of the eight cases of unilateral aphakia and glaucoma had smaller corneal diameters in the aphakic eye compared with the normal eye. This is similar to the report by Parks and coworkers9 that 23 of 26 patients (88%) with aphakic glaucoma had microcornea. According to the experience of Wallace and Plager,22 the majority of cases of aphakic glaucoma in children have open angles. They suspected that microcornea is indicative of an abnormal anterior segment and angle development that results in a deficient angle filter mechanism, and that this altered filtering mechanism is the major factor responsible for the development of glaucoma in these patients.

The cause of the open-angle glaucoma may remain uncertain in most of the patients who develop open-angle glaucoma after cataract surgery. Both mechanical and chemical theories have been proposed.23 One possibility is that release of tension on the zonules after removal of the lens may reduce traction on the trabecular meshwork, potentially decreasing the trabecular spaces and reducing outflow facility. Another possibility is the influence of lens particles

Figure 14.3 Microcornea and aphakia. The patient is now an adult and has developed elevated intraocular pressure.

or proteins, inflammatory cells, and vitreous-derived factors on the trabecular meshwork. Also, the possibility of a steroidinduced glaucoma is high, because steroids are used for a longer period after cataract surgery in children who usually show increased inflammation, even with the newer techniques of cataract surgery.

Risk factors

Development of glaucoma in aphakia and pseudophakia after congenital cataract surgery is multifactorial. Its occurrence has been associated with risk factors, including age at surgery, pre-existing ocular abnormalities, type of cataract, and the effect of lens particles, lens proteins, inflammatory cells, and retained lens material. In addition, microcornea, secondary surgery, chronic postoperative inflammation, the type of lensectomy procedure or instrumentation, pupillary block, and the duration of postoperative observation have been found to influence the likelihood of glaucoma after pediatric cataract surgery.

Rabiah24 identified several strong predictors of glaucoma after pediatric cataract surgery, including surgery at ≤ 9 months of age, secondary membrane surgery, microcornea, and primary posterior capsulotomy with anterior vitrectomy. In this study, chronic glaucoma was common after cataract surgery performed at or before, but not after, a threshold age in childhood (approximately 9 months). Glaucoma developed in 37% of eyes after cataract surgery at ≤ 9 months of age, and 6% in eyes undergoing cataract surgery after 9 months of age during an average 9 years follow-up. Survival analysis predicted higher rates of glaucoma with longer follow-up (Fig. 14.4).

Diagnostic clues and evaluation

Glaucoma evaluation in aphakia and pseudophakia following congenital cataract surgery should include assessment

Figure 14.4 Survival curve analysis for development of glaucoma after pediatric cataract surgery. The data was estimated from multivariable Cox proportional hazards model with adjustment for intrasubject correlation. In this study, age at time of cataract surgery was a risk factor for the development of glaucoma, with a higher risk in children who underwent cataract surgery up to 9 months of age. Modified with permission from Rabiah PK. Frequency and predictors of glaucoma after pediatric cataract surgery. Am J Ophthalmol 2004; 137:30–37.

of corneal diameter, slit-lamp evaluation, applanation tonometry, and estimation of the glaucomatous optic nerve damage. Visual field measurements can be performed with the Goldmann perimeter or with automated perimetry (Humphrey, Octopus, and others), if the child is old enough to co-operate.

The diagnosis of glaucoma may be difficult to establish in children after congenital cataract surgery since they often lack the classic signs of congenital glaucoma, such as buphthalmos, epiphora, and blepharospasm. Moreover, the intraocular pressure may be difficult to measure with the child awake, and the view of the optic disc may be compromised by lens remnants, miosis, and nystagmus. Also, visual fields usually cannot be accurately assessed until later in childhood. When an adequate examination cannot be obtained while a child is awake, an examination should be performed under sedation or general anesthesia, especially if there is a high index of suspicion of glaucoma. An ideal evaluation should include measurement of the corneal diameter, intraocular pressure, cycloplegic refraction and an optic nerve head evaluation. Ancillary testing should include measurement of axial length by A-scan ultrasonography and optic nerve head photographs.

Measurements of corneal diameter is important, not only to identify buphthalmos, but also to identify microcornea, which has been associated with pediatric aphakic glaucoma. Wallace and Plager22 found that 45 of the 48 (94%) eyes in their series had microcornea when compared with the normal corneal diameter of their age. They concluded that the clinician should be aware that the children with a small corneal diameter at the time of surgery are at risk for glaucoma. If the corneal diameter is noted to be smaller than normal for the child’s age or, in the cases of unilateral cataract, smaller than the phakic eye, the child should be followed closely throughout childhood and beyond for signs of glaucoma.

Egbert and Kushner25 presented four patients of juvenile aphakic glaucoma in whom an excessive loss of hyperopia was the initial clinical sign that alerted them to the diagnosis of glaucoma. The authors believe that this is an important sign in patients who are unable to cooperate with intraocular pressure measurements and visual field or meticulous optic nerve head examinations. They believe aphakic patients exhibiting a marked loss of hyperopia should be considered glaucoma suspects. Walton15 mentioned that in absence of regular tonometry, recognition of corneal clouding, ocular enlargement, and contact lens intolerance aided in the diagnosis of glaucoma in his series of 65 children who had glaucoma after congenital cataract surgery.

The appearance of anterior chamber angle is very important in disclosing the mechanism of glaucoma in the aphakic or pseudophakic eye following congenital cataract surgery. Walton15 performed gonioscopic evaluation with Koeppe gonioscopy, a Barkan hand-held microscope with 6 × magnification, and a hand-held light. Abnormalities were found in the angles of 76 of the 80 glaucoma eyes. The angles were open in 79 of 80 eyes; however, 5 eyes with a history of treated pupillary block glaucoma showed variable degrees of peripheral anterior synechiae. In 1 of these 5 eyes, very little

open angle was present. In the 79 eyes with open angles, the most consistent defect was a circumferential repositioning of the iris insertion anteriorly at the level of the posterior or mid trabecular meshwork, with resultant loss of view of the ciliary body band and scleral spur. Scattered pigment deposits were frequent; less frequent were white crystalline deposits suggestive of residual lens material caught in the meshwork.

The frequency of follow-up examinations after pediatric cataract surgery varies depending upon individual patient factors. In one recommendation for follow-up examinations after infantile cataract surgery, screening examinations for glaucoma were suggested for every three months during the first postoperative year, twice yearly until the 10th year, and annually thereafter.2

Treatment

Medical

Initial medical treatment is usually tried in children with aphakia or pseudophakia and glaucoma, because the surgical options in these eyes are less successful and are associated with greater morbidity than in phakic eyes. Medical therapy with beta-blockers, carbonic anhydrase inhibitors, and prostaglandin-related drugs may be used, as described in Chapter 9. Pilocarpine (1 or 2%), which has a better sideeffect profile in aphakic or pseudophakic patients compared with phakic patients, may also be helpful. The risk of retinal detachment has to be borne in mind with pilocarpine. Epinephrine or propine are not useful because of the low efficacy of these drugs and the risk of cystoid macular edema.

Pressman and Crouch20 reported 3 cases of pediatric aphakic glaucoma initially treated with medical treatment, but long-term control of intraocular pressure was not achieved. In the series reported by Asrani and Wilensky,2 medications alone successfully controlled the intraocular pressure in 21 (63.6%) of 33 eyes. In the series reported by Simon and colleagues,3 six of eight eyes were controlled medically (below 21 mmHg) with a combination of miotics and beta-blockers.

Unlike primary congenital glaucoma, which responds poorly to medical therapy, it appears that at least some patients with glaucoma associated with aphakia or pseudophakia may achieve long-term control of intraocular pressure with medical therapy alone. In some types of glaucoma in aphakia and pseudophakia, there may be an element of inflammation, which warrants anti-inflammatory treatments together with the antiglaucoma treatment. Miotics and prostaglandin analogues should be avoided in such cases.

Laser treatment

The argon or diode lasers are usually not effective in management of glaucoma associated with aphakia or pseudophakia in children. Pressman and Crouch20 performed argon laser trabeculoplasty in one case using 100 to 150 spots with 50 μm spot size and 1000–1250 mW with a duration of 0.1 second. This treatment was not effective.

The Nd:YAG laser is particularly useful for iridotomy in pupillary block glaucoma in children. Vajpayee and co-

workers14 reported a series of 16 children with pseudophakic pupillary-block glaucoma that was managed with Nd:YAG laser iridotomy. After intraocular pressure was controlled initially with medications, Nd:YAG laser iridotomy was performed within two to three days in all eyes. Initial Nd:YAG iridotomy failed in all eyes, but repeat Nd:YAG iridotomy one week later was performed successfully in all eyes. Satisfactory control of intraocular pressure was achieved in 13 of 16 patients (81%) after Nd:YAG iridotomy.

Surgical treatment

Surgical iridectomy

With the advent of Nd:YAG laser, laser iridotomy is the procedure of choice. There are few indications for surgical iridectomy when laser facilities are available. In the series reported by Vajpayee and co-workers,14 no patient required surgical iridectomy, although all patients required repeat Nd:YAG laser procedure to relieve pseudophakic pupillaryblock glaucoma. However, if Nd:YAG iridotomy fails repeatedly, surgical iridectomy is advisable, especially in patients with severe postoperative inflammation leading to pupillary block glaucoma. However, in such a situation, the clinician should evaluate whether iridotomy alone will be sufficient or a more definitive filtering surgery will be required.

Filtering surgery with or without antifibrosis drugs

Trabeculectomy is the most commonly performed filtering surgery in aphakia and pseudophakia following infantile cataract surgery, but the success rate is variable. Barriers to success include a thick and active Tenon’s capsule with rapid wound healing response in children.26 Aphakia or pseduophakia and young age are risk factors for failure of trabeculectomy.27–29

Pressman and Crouch20 reported three children with pediatric aphakic glaucoma who showed poor results with trabeculectomy and required repeat surgery. Trabeculectomy alone was successful in three out of five eyes whereas trabeculectomy with antimetabolite was successful in controlling the intraocular pressure in six out of seven eyes as reported by Asrani and Wilensky.2 Walton15 assessed the results of surgical treatment for 42 eyes of the 65 children. Initially, goniosurgical procedures were performed, with 11 goniotomy operations for 13 eyes considered failures. Trabeculectomy with mitomycin-C was helpful for 9 of 14 eyes (64%) with pediatric aphakic glaucoma. Lichter commented that trabeculectomy with antimetabolite is probably the preferred approach in managing glaucoma in aphakia and pseudophakia following congenital and infantile cataract surgery.

Antifibrosis drugs are known to inhibit fibroblast proliferation and have been found to improve the success rate of filtering surgery in adults as well as in children.30 Mitomycin- C and 5-fluorouracil (5-FU) are the most commonly used antifibrotic agents in glaucoma filtering surgery. Subconjunctival injection of 5-FU in children requires use of multiple

general anesthesias31 and thereby is not a suitable option in children with aphakic or pseudophakic glaucoma. Moreover, several prospective randomized studies in adults with high risk glaucoma filtering surgery have shown that intraoperative mitomycin-C may be a better alternative to postoperative 5-FU because mitomycin-C has resulted in lower overall intraocular pressure, decreased dependence on postoperative antiglaucoma medications, and decreased corneal toxicity. Several reports have been recently published on the successful use of mitomycin-C in children with refractory congenital glaucoma.32–34

Reports of clinical experience with trabeculectomy with mitomycin-C in pediatric aphakic and pseudophakic glaucoma are summarized in Table 14.4.2,15,34–39 With the exception of the report by Azuara-Blanco et al,37 the success rate varied from 50% to 85%. According to Wallace et al,35 trabeculectomy with mitomycin-C is the most effective treatment in aphakic glaucoma following congenital cataract surgery. In contrast, Azuara-Blanco et al37 had a poor outcome and commented that an alternative approach to aphakic childhood glaucoma may be necessary.

The optimal dose of mitomycin-C in children is yet unknown, although clinicians often use dosage of mitomycin-C ranging from 0.2 to 0.4 mg/ml for 2–3 minutes, which is safe and effective in children with aphakic and pseudophakic glaucoma based on our personal experience. However, prospective, randomized controlled clinical studies with larger number of patients and longer follow-up period are required to determine the optimal dosage and the application time of mitomycin-C, as well as the ocular and systemic factors that may predispose the eyes with refractory glaucoma to late complications. Early complications like shallow anterior chamber, corneal epitheliopathy, and hypotony with or without choroidal detachment are managed according to the standard treatments. Devastating complications, such as late infections, remain a potential danger with the use of

mitomycin-C as adjunctive therapy during trabeculectomy with refractory glaucoma in aphakia and pseudophakia following congenital cataract surgery.34–36,39 After trabeculectomy with mitomycin-C, these children require periodic examinations and the parents should be educated about the possible late complications.34

Glaucoma drainage implants

Drainage implant surgery appears to be a viable option for the management of those patients that are unresponsive to medical treatment or an initial conventional glaucoma filtering surgery. These drainage devices have been designed to maintain communication between the anterior chamber and the subconjunctival or sub-Tenon’s space posterior to the limbus (near the equator), in cases where there is a high risk of scarring of the filtration fistula. Certain implants have flowresistive valves (Ahmed and Krupin implants), whereas others are open-tube, non-valved implants (Molteno and Baerveldt implants). The long-term bleb-related complications and the potential risk of chemotherapeutic exposure are avoided with the use of drainage implants.

Encouraging reports obtained with the Molteno implants in young patients have led several investigators to use other implants in children with refractory glaucomas, including children with aphakia or pseudophakia. Satisfactory success rates have been reported by several investigators.40–45 Contradictory reports have also been published, with variable success rates ranging from 33% to 60%.35,46,47 In general, the success rates of glaucoma drainage devices in refractory pediatric glaucoma are variable and also the complication rates vary. Drainage implants may be a useful alternative to trabeculectomy with mitomycin-C for aphakic patients who are contact lens dependent, and who may be at greater risk for late-onset bleb-related infection and endophthalmitis after surgery.48

Cyclodestructive procedures

Cyclophotocoagulation is usually considered for eyes with poor vision that are refractory to other treatments. Previously, cyclocryotherapy was the most commonly used method of cycloablation, but cyclophotocoagulation with the diode laser has become popular. Laser cycloablation is generally better tolerated by patients. Both cyclocryotherapy and cyclophotocoagulation have been used for treatment of pediatric aphakic and pseudophakic eyes that are refractory to other treatments.49,50 Success rates with long-term follow-up are low, and serious vision-threatening complications may occur. Repeated cyclophotocoagulation treatments may have a role as a temporizing measure, as an adjunct to surgery, or in managing select patients in whom surgery is undesirable because of a high risk of surgical complications.51

Conclusions

Up to a quarter or more of pediatric patients with pseudophakia or aphakia may develop glaucoma after cataract surgery.24 The onset of glaucoma may occur years after cataract surgery, thus the proportion of affected children increases with longer follow-up. Patients may develop angleclosure glaucoma, but more commonly develop open-angle glaucoma. Life-long monitoring for glaucoma is necessary. Antiglaucoma medications may be helpful in some patients, whereas laser therapy for open-angle glaucoma is generally not effective. Patients with aphakia or pseudophakia and glaucoma that is refractory to medical therapy may be treated with trabeculectomy with mitomycin-C or glaucoma drainage implant.

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