Optic disc drusen

DEFINITION/OVERVIEW AND ETIOLOGY

The majority of cases of anomalous elevations of the optic disc (pseudopapilledema) are associated with hyaline bodies of the optic nerve called drusen. Drusen are frequently bilateral and are inherited in an AD pattern.

CLINICAL PRESENTATION

Drusen may initially occur beneath the optic disc surface, so-called buried drusen. Subsequently, the drusen may enlarge and the disc axons may degenerate, resulting in visible drusen at the optic disc surface. The drusen appear as shiny refractile bodies with a gray-yellow translucent appearance. They may cause an irregular optic disc border. They do not obscure the retinal vessels overlying the disc (230).

Central visual acuity is generally normal. However, asymptomatic peripheral visual field defects such as constriction, arcuate defects, and nasal steps, commonly occur.

DIAGNOSIS

Optic disc drusen must be differentiated from papilledema. In contrast to papilledema, disc drusen occur without disc hyperemia, vessel obscuration, nerve fiber layer hemorrhages, or exudates. Optic disc drusen may be associated with subretinal hemorrhages as well as peripapillary subretinal avascular membranes.

Fluorescein angiography shows autofluorescence of the drusen without disc leakage. B-scan ultrasonography and CT may demonstrate drusen as noted above. These modalities are helpful for the detection of buried disc drusen that are not clearly visible on clinical examination.

Disorders of the nasolacrimal system are among the most common ocular disorders that a pediatrician will encounter. Knowledge of the natural history of various abnormal conditions of the nasolacrimal system and their associated treatment options will allow for assured discussion with parents to alleviate fears and increase awareness of the child’s condition. It can also act as a guide to ascertain when more serious conditions may be present, and when further ophthalmologic evaluation may be necessary.

The nasolacrimal system consists of both a secretory portion (lacrimal and accessory lacrimal glands) and a drainage portion (the puncta, canaliculi, lacrimal sac, and nasolacrimal duct). Abnormalities at any point along the system can manifest clinically. The lacrimal gland is the main producer of reflex tear secretion, and is generally functional between birth and 2 months of age. The accessory lacrimal glands are responsible for basal tear secretion, and are functional at birth. The puncta are openings at the medial eyelid margin which the tears enter. They are usually situated on a mildly elevated area of eyelid called the ampulla. Absence of both punctum and ampulla suggests complete agenesis as opposed to simply an imperforate punctum. The eyelid puncta begin to open at approximately 6 months gestation.1 The canalicular system takes the tears from the punctal opening into the nasolacrimal sac. The upper and lower canaliculi usually (~90%) connect into a common canaliculus just prior to entering the nasolacrimal sac. The nasolacrimal duct exits the nasolacrimal sac and traverses through bony canal into the inferior meatus beneath the inferior turbinate. The nasolacrimal duct begins as a cord of surface ectoderm. It cannulates from the proximal end to the distal end. It is most common for the distal end to open at about term, though about 6% of neonates will have an imperforate nasolacrimal duct.2

ETIOLOGY

A dacryocele is formed when the nasolacrimal duct is obstructed at both the proximal and terminal ends, both at the valve of Rosenmuller (at the level of the common canaliculus entering into the nasolacrimal sac) and the valve of Hasner (at the level of the nasolacrimal duct entering the inferior meatus in the nose). Blockage of both the inlet and the outlet of the duct leads to sequestration of mucus which can become secondarily infected.

CLINICAL PRESENTATION

The presentation of a dacryocele (sometimes called amniotocele, lacrimal sac mucocele, dacryocystocele) is usually at birth. A bluish mass is noted inferior to the medial canthal angle (231). In the case of infection, the skin overlying the lacrimal sac can be erythematous. Schnall and Christian (1996) found that 4/21 (19.0%) dacryoceles had evidence of infection, with three occurring at the time of presentation.3 Becker (2006) found a much higher percentage of secondary infection, with 21/29 (72.4%) developing dacryocystitis and/or cellulitis.4 A dacryocele may also exhibit intranasal extension, causing respiratory distress in the newborn. Paysse et al. (2000) found a concurrent intranasal mucocele in 23/30 (~77%) dacryoceles, with respiratory distress present in seven patients.5

DIAGNOSIS

The diagnosis of a dacryocele is usually clinical. As noted above, it is usually a bluish elevation occurring below the medial canthal tendon. The differential diagnosis for such a lesion includes meningoencephalocele (which are normally located superior to the medial canthal tendon), dermoid cyst, or hemangioma. Imaging is not normally necessary. MRI can be performed to assess the area should an atypical lesion be present.6 Suggestions of an atypical presentation include an elevation occurring above the medial canthal tendon, hypertelorism, pulsation, and known CNS abnormality.6 Prenatal diagnosis of dacryocele has also occurred using ultrasound.7 Nasal examination using a nasal speculum or endoscope can be performed to evaluate for the presence of an intranasal mucocele.

MANAGEMENT/TREATMENT

There are differing opinions regarding the treatment of dacryoceles. Current conservative measures include digital massage of the lacrimal sac in an attempt to hydrostatically decompress the lacrimal sac. Infrequently, the dacryocele can decompress through the canalicular system, but the nasolacrimal duct can remain blocked distally at the valve of Hasner.4 Schnall and Christian (1996), in a prospective study, found that 16/21 (76%) resolved with conservative treatment consisting of antibiotics (topical and/or systemic based on presence of infection), digital massage, and warm compresses.3 In addition, 4/4 dacryoceles that were infected at presentation or became infected after presentation resolved with conservative therapy. All dacryoceles resolved within 1 week,

thus a recommendation was made that 1 week of conservative therapy is indicated in these patients prior to nasolacrimal duct probing. Becker (2006), however, found that 7/7 (100%) of patients without infection who had a nasolacrimal duct probing had resolution, whereas only 10/19 (~53%) who had infection had resolution following a nasolacrimal duct probing.4 He advocated early probing in an attempt to open the system prior to the development of thickened cyst wall and turbid purulent fluid, which can lead to early closure. The failure rate of initial probing was highest in those patients who had an infection. Should initial probing fail, repeat probing with or without silicone tube intubation, balloon dacryoplasty, or marsupialization of the intranasal cyst can be undertaken.4