CONGENITAL / DEVELOPMENTAL GLAUCOMAS TERMINOLOGY The congenital glaucomas are a group of diverse disorders in which abnormal high intraocular pressure results due to developmental abnormalities of the angle of anterior chamber obstructing the drainage of aqueous humour. Sometimes glaucoma may not occur until several years after birth; therefore, the term developmental glaucoma is preferred to describe such disorders. Types 1. Primary developmental/congenital glaucoma. 2. Developmental glaucoma with associated ocular anomalies. PRIMARY DEVELOPMENTAL/CONGENITAL GLAUCOMA It refers to abnormally high IOP which results due to developmental anomaly of the angle of the anterior chamber, not associated with any other ocular or systemic anomaly. Depending upon the age of onset the developmental glaucomas are termed as follows: 1. True congenital glaucoma is labelled when IOP is raised during intrauterine life and child is born with ocular enlargement. It occurs in about 40 percent of cases. 2. Infantile glaucoma is labelled when the disease manifests prior to the child's third birthday. It occurs in about 50 percent of cases. 3. Juvenile glaucoma is labelled in the rest 10 percent of cases who develop pressure rise between 3-16 years of life. 212 Comprehensive OPHTHALMOLOGY When the disease manifests prior to age of 3 years, the eyeball enlarges and so the term‘buphthalmos’ (bull-like eyes) is used. As it results due to retention of aqueous humour (watery solution), the term ‘hydrophthalmos, has also been suggested. Prevalence and genetic pattern Most cases are sporadic. About 10 percent cases exhibit an autosomal recessive inheritance with incomplete peneterance. Although sex linkage is not common in inheritance, over 65 percent of the patients are boys. The disease is bilateral in 75 percent cases, though the involvement may be asymmetric. The disease affects only 1 child in 10,000 births. Pathogenesis Maldevelopment of trabeculum including the iridotrabecular junction (trabeculodysgenesis) is responsible for impaired aqueous outflow resulting in raised IOP. In primary congenital glaucoma the trabeculodysgenesis is not associated with any other major ocular anomalies. Clinically, trabeculodysgenesis is characterized by absence of the angle recess with iris having a flat or concave direct insertion into the surface of trabeculum as follows: Flat iris insertion is more common than the concave iris insertion. In it the iris inserts flatly and abruptly into the thickened trabeculum either at or anterior to scleral spur (more often) or posterior to scleral spur. It is often possible to visualize a portion of ciliary body and scleral spur. Concave iris insertion is less common. In it the superficial iris tissue sweeps over the iridotrabecular junction and the trabeculum and thus obscures the scleral spur and ciliary body. Clinical features 1. Photophobia, blepharospasm, lacrimation and eye rubbing often occur together. These are thought to be caused by irritation of corneal nerves, which occurs as a result of the elevated IOP. Photophobia is usually the initial sign, but is not enough by itself to arouse suspicion in most cases. 2. Corneal signs. Corneal signs include its oedema, enlargement and Descemet’s breaks. i. Corneal oedema. It is frequently the first sign which arouses suspicion. At first it is epithelial, but later there is stromal involvement and permanent opacities may occur. ii. Corneal enlargement. It occurs along with enlargement of globe-buphthalmos (Fig. 9.5), especially when the onset is before the age of 3 years. Normal infant cornea measures 10.5 mm. A diameter of more than 13 mm confirms enlargement. Prognosis is usually poor in infants with corneal diameter of more than 16 mm. iii. Tears and breaks in Descemet’s membrane (Haab’s striae). These occur because Descemet’s membrane is less elastic than the corneal stroma. Tears are usually peripheral and concentric with the limbus. 3. Sclera becomes thin and appears blue due to underlying uveal tissue. 4. Anterior chamber becomes deep. 5. Iris may show iridodonesis and atrophic patches in late stage. 6. Lens becomes flat due to stretching of zonules and may even subluxate. 7. Optic disc may show variable cupping and atrophy especially after third year. 8. IOP is raised which is neither marked nor acute. 9. Axial myopia may occur because of increase in axial length which may give rise to anisometropic amblyopia. Examination (Evaluation) A complete examination under general anaesthesia should be performed on each child suspected of having congenital glaucoma. The examination should include following: Fig. 9.5. A child with congenital glaucoma. GLAUCOMA 213 1. Measurement of IOP with Schiotz or preferably hand held Perkin’s applanation tonometer since scleral rigidity is very low in children. 2. Measurement of corneal diameter by callipers. 3. Ophthalmoscopy to evalute optic disc. 4. Gonioscopic examination of angle of anterior chamber reveals trabeculodysgenesis with either flat or concave iris insertion as described in pathogenesis. Differential diagnosis It is to be considered for different presenting signs as follows: 1. Cloudy cornea. In unilateral cases the commonest cause is trauma with rupture of Descemet’s membrane (forceps injury). In bilateral cases causes may be trauma, mucopolysaccharidosis, interstitial keratitis and corneal endothelial dystrophy. 2. Large cornea due to buphthalmos should be differentiated from megalocornea. 3. Lacrimation in an infant is usually considered to be due to congenital nasolacrimal duct blockage and thus early diagnosis of congenital glaucoma may be missed. 4. Photophobia may be due to keratitis or uveitis. 5. Raised IOP in infants may also be associated with retinoblastoma, retinopathy of prematurity, persistent primary hyperplastic vitreous, traumatic glaucoma and secondary congenital glaucoma seen in rubella, aniridia and Sturge-Weber syndrome. Treatment Treatment of congenital glaucoma is primarily surgical. However, IOP must be lowered by use of hyperosmotic agents, acetazolamide and betablockers till surgery is taken up. Miotics are of no use in such cases. Surgical procedures for congenital glaucoma 1. Goniotomy (Fig. 9.6). In this procedure a Barkan's goniotomy knife is passed through the limbus on the temporal side. Under gonioscopic control the knife is passed across the anterior chamber to the nasal part of the angle. An incision is made in the angle approximately midway between root of the iris and Schwalbe's ring through approximately 75°. The knife Fig. 9.6. Technique of goniotomy : A, showing position of goniotomy knife in the angle under direct visualization; B, showing procedure of sweeping the knife in the angle. is then withdrawn. Although the procedure may have to be repeated, the eventual success rate is about 85 percent. 2. Trabeculotomy. This is useful when corneal clouding prevents visualization of the angle or in cases where goniotomy has failed. In this, canal of Schlemm is exposed at about 12 O’clock position by a vertical scleral incision after making a conjunctival flap and partial thickness scleral flap. The lower prong of Harm’s trabeculotome is passed along the Schlemm’s canal on one side and the upper prong is used as a guide (Fig. 9.7). Then the trabeculotome is rotated so as to break the inner wall over one quarter of the canal. This is then repeated on the other side. The main difficulty in this operation is localization of the Schlemm's canal. 3. Combined trabeculotomy and trabeculectomy is now-a-days the preferred surgery with better results. 214 Comprehensive OPHTHALMOLOGY DEVELOPMENTAL GLAUCOMAS WITH ASSOCIATED ANOMALIES A wide variety of systemic and/or ocular anomalies have an associated raised IOP, usually due to developmental defects of the anterior chamber angle. Some of the associations are as follows: 1. Glaucoma associated with iridocorneal dysgenesis. These include: posterior embryotoxon characterised by a prominent Schwalbe’s ring (Axenfeld anomaly), Rieger anomaly, Rieger syndrome, Peter’s anomaly and combined Rieger syndrome and Peter’s anomaly. 2. Glaucoma associated with aniridia (50% cases). 3. Glaucoma associated with ectopia lentis syndromes, which include Marfan’s syndrome, Weil-Marchesani syndrome and homocystinuria. 4. Glaucoma associated with phakomatosis is seen in Sturge-Weber syndrome ( 50% cases) and Von Recklinghausen’s neurofibromatosis (25% cases). 5. Miscellaneous conditions. Lowe’s syndrome (oculo-cerebro-renal syndrome), naevus of Ota, nanophthalmos, congenital ectropion uveae, congenital microcornea and rubella syndrome.
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