INFANTILE AND PEDIATRIC GLAUCOMA

Mean defect (M): represents how far ‘‘the island of vision has sunk into the sea of darkness.’’ The lower the value, the higher the decrease in sensitivity.

Glaucoma hemifield test (GHT): mathematical model that compares the superior VF to the mirror image of points in the inferior VF; highly predictive of glaucomatous VF loss.

Pattern standard deviation (PSD) and corrected PSD (CPSD): the lower the number, the higher the decrease in sensitivity in a localized manner. CPSD is not available with SITA. A low PSD indicates localized decreased sensitivity. If both PSD and CPSD are low, then there is a significant decreased VF, and most likely glaucoma is present. This index factors out any generalized reduction and looks at how regular or irregular is the shape of the ‘‘island of vision.’’

Artifactual defects:

Lens rim defect: superior edge defect

Cloverleaf pattern: advanced glaucoma or inattention; patient loses concentration, and the four paracentral areas that are mapped the most show deeper scotomas.

Generalized field depression: caused by cataract, miotic therapy, and inappropriate optical correction

The myope not wearing a contact lens has an enlarged blind spot that is moved out when viewing through the HVF lens versus the aphakic patient’s blind spot, which is minimized and moved in.

Short-wavelength automatic perimetry (SWAP): blue-yellow perimetry to identify early magnocellular (M cell) loss. (M cells are not damaged earlier in glaucoma, but there is less redundancy with the M cell system; thus, may identify damage from a single axon). May identify VF defect 3 years earlier than with HVF perimetry. High false-positive rate.

Infantile and Pediatric Glaucoma

CONGENITAL GLAUCOMA, PRIMARY TRABECULODYSGENESIS 50 to 70% of cases of pediatric glaucoma are congenital, with a 1:12,500 incidence (increased with inbreeding). Two thirds of patients are male, two thirds of cases are bilateral. Defect is on chromosome 2, autosomal recessive, with increased gene frequency in patients of Middle Eastern ancestry (may have an X-linked variant, but do not confuse with X-linked megalocornea).

Two main symptoms: tearing and photophobia. Two main signs: corneal edema and buphthalmos (occurs only if age <3 years; the neonate cornea is normally 10 mm, 11 mm by 1 year). Also

Goodman, Ophtho Notes © 2003 Thieme

All rights reserved. Usage subject to terms and conditions of license.

156 GLAUCOMA

blepharospasm, increased IOP, Haab’s striae (horizontal Descemet’s membrane breaks that extend to the limbus). Patient may also have poor vision from progressive myopia due to globe enlargement.

Pathogenesis: ‘‘fetal angle configuration,’’ with a high insertion of the iris root; reported Barkan’s membrane, although a membrane is rarely seen covering the TM.

Treatment: a surgical disease, but treat IOP first with topical medication; when cornea clears, surgically open TM with goniotomy (90% curative for one to three surgeries) or trabeculotomy if the cornea is cloudy. May use Diamox, but generally avoid topical carbonic anhydrase inhibitors, Alphagan, and Xalatan in infants.

Poor visual prognosis if myopia, anisometropic amblyopia, strabismus, irregular astigmatism (from Haab’s striae), corneal edema, cornea >14 mm, and optic neuropathy. Amblyopia is the leading long-term cause of vision loss.

JUVENILE OPEN-ANGLE GLAUCOMA (JOAG) Autosomal dominant, chromosome 1q21–q31 GLC1A gene defect coding for myocilin (formerly TM induced glucocorticoid response [TIGR]) protein. Similar gene defect also present in 3 to 5% of POAG patients and in steroid-response glaucoma (increased TM GAG). Age of onset >3 years; thus, no risk for buphthalmos. JOAG has very high IOP and aggressive course.

SECONDARY GLAUCOMAS FROM CONGENITAL ANOMALIES

Aniridia: 50 to 75% secondary ACG from peripheral iris stump obstructing TM, bilateral. Associated with nystagmus, foveal hypoplasia, ON hypoplasia, corneal pannus, and anterior polar cataract. From PAX 6 gene defect, most are autosomal dominant, but if sporadic, then there is a 20% incidence of Wilms’ tumor (nephroblastoma).

Axenfeld-Rieger syndrome: 50% of patients have glaucoma from trabecular dysgenesis and PAS. It is an autosomal dominant, bilateral neural crest abnormality with iridocorneal adhesions; also associated with maxillary hypoplasia, dental abnormalities, hypospadias, and inguinal or, more specifically, umbilical hernias.

Lowe’s oculocerebrorenal syndrome: 67% risk of glaucoma. It is an X-linked recessive disorder characterized by bilateral cataracts, renal rickets, and aminoaciduria.

NF I: 50% unilateral glaucoma if upper-lid plexiform neurofibroma is present.

Peters’ anomaly: 50% glaucoma from anterior segment dysgenesis with lens attached to cornea, along with the absence of Descemet’s membrane and endothelium. May be autosomal dominant, recessive, or sporadic.

Goodman, Ophtho Notes © 2003 Thieme

All rights reserved. Usage subject to terms and conditions of license.

Sturge-Weber syndrome: 33% glaucoma if lid or conjunctiva is involved with the hemangioma; patients may have late-onset glaucoma from increased EVP and blocked aqueous outflow.

Rubella: trabeculodysgenesis usually from in utero infection in the third trimester (TM forms in the third trimester vs. rubella cataract, which is usually from infection in the second trimester, when the lens forms; thus, they are not seen together). Patients may also have cardiac abnormalities, salt and pepper retinopathy. Responds well to goniotomy, even with adults.

Others: PHPV, microphthalmia, nanophthalmos, traumatic, uveitic, and ectropion uveae

Primary Open-Angle Glaucoma

Primary open-angle glaucoma (POAG), which represents 80% of glaucoma cases in the United States, is an acquired, chronic, bilateral disease that is often characterized by asymmetric ON damage. It is diagnosed by the appearance of the disk and VF abnormality, with open angles and no secondary cause. Genetic mutation is seen in some patients at chromosome 3q21–24 gene GLC1C (probably is late-onset variant of autosomal dominant hereditary glaucoma). Etiology is probably from decreased outflow (increased GAG in the TM and loss of trabecular beam endothelial cells).

Diagnosis is done by ruling out angle closure or secondary causes. Usually two of three conditions are present: characteristic ON appearance, glaucomatous VF defect, and increased IOP. May use water provocative test: 1 liter H2O increases IOP >8 mmHg.

Six major risk factors: weaker association with hypertension, coronary artery disease, migraine, or other vasospasm disorder.

Age: better predictor of glaucoma than IOP (Collaborative Glaucoma Study).

Diabetes: 2–3 more prevalent.

Elevated IOP: if IOP is 20–25 mmHg, 7% have ON or VF damage; 26–30 mmHg, the risk of glaucoma is 12%; >30 mmHg, the risk is 28%. The yearly risk of VF loss if IOP is 21–30 mmHg is 1%; if >30 mmHg, the risk is 10%.

Heredity: 25% of POAG patients have a positive family history. There is a 10% risk of POAG if a first-degree relative is affected (especially a sibling).

Myopia: 3 POAG risk if greater than 6 D. Glaucoma diagnosis may be confounded by myopic signs: PPA, tilted or oval disk, and scleral crescent.

Race: African-American patients have higher IOP, larger C:D ratio, and greater glaucoma prevalence, with earlier onset and 8 increased risk of blindness from glaucoma.

Goodman, Ophtho Notes © 2003 Thieme

All rights reserved. Usage subject to terms and conditions of license.

158 GLAUCOMA

Treatment: often begin with a topical beta-blocker or prostaglandin agonist, then add other medications as needed. Topical alpha agonists (Alphagan or Iopidine) have similar efficacy as beta-blockers but have more side effects (allergy, respiratory issues in children, etc.). Most drops are equivocal (timolol is the most studied; Ocupress has intrinsic sympathomimetic activity and is thus better in treating hyperlipidemia and nocturnal hypotension but is only a partial agonist). Adding a topical carbonic anhydrase inhibitor (e.g., dorzolamide) to timolol will decrease IOP about 2–3 mmHg. May also use ALT early in treatment course. For medication or laser treatment failures, consider trabeculectomy.

Collaborative Initial Glaucoma Treatment Study (CIGTS): an ongoing, randomized, controlled clinical trial evaluating initial medical treatment versus trabulectomy, and has thus far found no difference in glaucoma progression between the two groups.

NORMAL TENSION GLAUCOMA (NTG) Characterized by ON cupping and VF loss with normal IOP. VF defects tend to be steeper, deeper, and closer to fixation and more commonly have disk hemorrhage, which is a predictor of VF deterioration. Some patients have chromosome 2cen-q13 defect in GLC1B gene and also etiology from vascular factors.

Differential diagnosis: burned out POAG, SOAG, shock optic neuropathy (hypotensive episode, anemia), AION, myopic disk, other optic neuropathies (think of especially in younger patients, or if rim pallor, central VF loss or color deficits are present). Consider work-up with CBC and ESR to rule out anemia and giant cell arteritis or temporal arteritis (GCA).

Collaborative Normal Tension Study Group (CNTSG): a multicenter, controlled clinical trial that randomized normal tension glaucoma patients into treatment (medications, laser, or surgery) versus observation groups. Thirty-five percent of untreated eyes worsened within 3 years (the other 65% eventually showed some slow progression); 7% of treated eyes worsened. The CNTSG is the first conclusive study that showed decreasing IOP by 30% prevents vision loss (aim for IOP <15 mmHg), but 9% of patients progress even despite a very low IOP.

OCULAR HYPERTENSION (OHT) Characterized by IOP >21 mmHg, with an open angle, no ON or VF defect. Only 1% of patients per year develop VF loss or diagnosis of true glaucoma.

Ocular Hypertension Treatment Study (OHTS): an ongoing, multicenter, controlled clinical evaluation of medical treatment for OHT, which has thus far shown that subjects who received topical glaucoma medication experienced conversion to glaucoma at less than half the rate of subjects who were monitored without treatment.

Goodman, Ophtho Notes © 2003 Thieme

All rights reserved. Usage subject to terms and conditions of license.