Fig. 5.7  Morning glory disc. Note marked vessel abnormalities with “looping” vessels at the disc margin. The central space can sometimes be seen to “open” and “close”

Different authors have proposed the source to be liquid vitreous (through a retinal tear or optic nerve head), incompetent retinal or choroidal vessels, subarachnoid fluid, or fluid from the orbit. Von Fricken and Dhungel have reported a case with a retinal tear at the edge of the optic nerve that was successfully treated with pars plana vitrectomy and gas–fluid exchange [20].

5.2.8  Associations and Complications

A number of authors have reported the association of MGDA and basal encephalocele. Patients may have hypertelorism and flattened nasal root or present with masses in the nasal or oral cavities. Care should be taken before performing oral or nasal surgery in patients with MGDA to rule out basal encephalocele [15].

5.2.6  Diagnosis

The diagnosis of MGDA is based solely on the clinical appearance of a symmetric excavated disc lesion with a surrounding elevated annulus of pigmentary changes (Figs. 5.6 and 5.7). Blood vessels are increased in number and appear to loop around the edges of the disc. A central core of white glial tissue occupies the position of the normal optic cup. Some morning glory discs pulsate with widening and narrowing of the opening. This can be stimulated with light in some patients. The etiology of this phenomenon is poorly understood. There have been radiologic studies showing a cone-shaped defect as the optic nerve enters the globe.

5.3  Optic Nerve Head Pits

5.3.1  Introduction

Optic nerve head pits (ONHP) are a small depression or excavation of the optic nerve head (Fig. 5.8). They may be located temporally, centrally, or elsewhere on the disc and have been associated with serous

5.2.7  Treatment

Care should be taken to monitor for amblyopia and retinal detachment. Patching therapy can be useful to maintain the best possible vision in eyes with MGDA. As in any patient with poor vision in one eye, protective eyewear should be stressed to the patient or the parents.

Retinal detachment is a frequent complication in MGDA, occurring in approximately 30% of eyes [19, 20]. There is some controversy regarding the origin of the subretinal fluid in these detachments.

Fig. 5.8  Optic nerve pit – temporal depression of the left optic nerve. These will often communicate with the subretinal space causing a localized retinoschisis or detachment

detachment of the macula when temporal in location. Some detachments regress spontaneously, but most result in significant visual deterioration. Multiple etiological theories have been implicated including vitreous fluid escaping through the pit causing macular retinoschsis or elevation of the neurosensory retina in the macular area. Most of these cases have been associated with posterior vitreous detachment (PVD).

the disease [25–27]. Different optic disc congenital morphological changes have been described in the same family. Corbett et al. [28] considered optic disc colobomas and optic disc pits to be a morphologically related but separate developmental defect. Although most of the optic disc pits are considered of congenital origin, an acquired nature of these anomalies has been described [29]. However, there has been no photographic evidence of this occurrence [30].

5.3.2  Overview with Clinical Significance

Most ONHP are asymptomatic, but a small subset can develop a serous macular detachment, which often results in permanent visual loss. Since small pits can be easily overlooked, a diagnosis of idiopathic central serous retinopathy should not be made without a detailed optic nerve examination.

5.3.3  Classification

There has been no formal classification for optic pits in the literature. However, different stages have been postulated (Table 5.3) based on the optical coherence findings of the optic pit and the associated macular changes [21–24].

5.3.4  Genetics

Congenital pits of the optic nerve head are isolated, generally nonfamilial unilateral malformations. There have been only three reports of familial origin of

Table 5.3  Stages of optic nerve pits

5.3.5  Pathophysiology

The embryological defect leading to optic pits and the origin of the submacular fluid in this condition have been debated for over half a century. Some authors have felt that pits were really colobomas [31, 32] and the finding of pits associated with colobomas in some reports supports this conclusion [30, 33]. If pits are to be considered colobomatous defects, they are an atypical form of such an anomaly [34, 35]. Most pits occur in a temporal or inferotemporal location in the optic disc [30, 36] emphasizing that pits are not true colobomas. Mann [37] has suggested that pits may occur as a result of failure of closure of only the upper end of the fetal fissure or maybe an anomalous differentiation of pluripotent cells within the optic vesicle wall.

Macular changes associated with optic pits have been described in the early literature but were thought to be coincidental [34, 38, 39]. In 1958, Peterson suggested a relation between optic pits and the occurrence of subretinal fluid [40]. In 1960, Kranenburg described optic pits in assocaition with a serous maculopathy [36, 41–46]. Subretinal fluid has been associated with temporal optic pits, and not central or nasal optic pits [30].

There has been considerable speculation as to the origin of the subretinal fluid associated with optic pits. Cerebrospinal fluid has been implicated [41, 47], but this was not supported in a study by Kalina and Conrad [48], which, after injecting intrathecal fluorescein, failed to find a connection between the two spaces. Some authors have shown that liquefied vitreous entering through the pit [42–44], or through a macular hole [49], can track under the retina causing a localized detachment. Evidence to support this mechanism includes the biomicroscopic finding of channels extending from the pit toward the subretinal space combined with a PVD and liquefaction of the vitreous [50]. The concept that macular detachment associated with optic pits may be of rhegmatogenous origin

due to unnoticed hole in the diaphanous tissue of the optic disc has also been suggested [51].

Lincoff described the macular changes seen as retinoschisis instead of retinal detachment [52]. Optical coherence tomography (OCT) has demonstrated that the retinal elevation that communicates with optic nerve pits is frequently a separation of the inner layers of the retina, not the whole retina. They have suggested that fluid separates the nerve fiber layer forming the schisis-like cavity. Secondary degeneration may follow in the outer retina causing outer holes and later localized neurosensory detachment [21, 22].

5.3.6  Incidence

Reis has estimated the frequency of optic pits to be approximately one in every 11,000 patients [32].

5.3.7  Natural History and Prognosis

(Signs, Symptoms, Timing, etc.)

Visual acuity is usually unaffected in optic pits unless it is complicated by serous macular detachment [53], which can occur in 25–75% of cases, usually during the third or fourth decade of life [30, 36, 54]. Sugar reported resolution of untreated retinal detachment in eight out of nine eyes [44]. However, Brown et al. followed untreated serous detachment for more than 1 year with poor final visual acuity secondary to the macular detachment in over 50% of the cases. In about 75% of these cases, the subretinal fluid did not resolve with time. Sobol et al. followed patients for 9 years and had similar results with most patients having final visual acuity of 20/200 or less [55].

5.3.8  Diagnosis and Diagnostic Aids

Pits are mostly unilateral but can be bilateral in 10–15% of cases [56]. Most of the pits exhibit a gray coloration [38, 57] and are normally located straight temporal or inferotemporal and rarely inferonasal on the disc (Fig. 5.8).

Fluorescein angiography of an optic pit usually shows early hypofluorescence and late hyperfluorescence [41, 45]. The late hyperfluorescence has been associated with cases of retinal detachment and could be due to late leakage from poorly visible blood vessels in the pit base, or fluorescein flow from the vitreous cavity to the pit late in the angiogram [30]. Indocyanine green angiography shows absolute hypofluorescence of the optic disc pit and late delineated hyperfluorescence corresponding to the area of macular elevation similar to fluorescein angiography. The degree of hyperfluorescence was less prominent in eyes with long-standing maculopathy [58].

OCT can demonstrate the separation of the retinal layers, the elevation of the outer retina, lamellar and outer retinal holes, and the cystic macular changes [21–24]. Response to treatment can also be assessed by OCT [23, 24].

Visual field changes have been well described with optic pits and include enlargement of the blind spot, central scotoma associated with retinal detachment, arcuate scotoma, and localized constrictions in the peripheral field [36, 40, 59, 60]. Outer layer detachment complicating optic pits can result in a dense central scotoma.

5.3.9  Treatment

A variety of treatment modalities have been tried aiming at resolution of the serous macular detachment. These include mannitol [61], patching plus bed rest [61, 62], steroids [46, 49], diathermy [63], photocoagulation along the periphery of the detached retina [64], intravitreal injection of expanding gas without vitrectomy [54], focal laser, and macular scleral buckling [58]. Outer layer detachment associated with optic pits can be reversed with a tamponade procedure with improvement of visual acuity. Multiple studies with varying success rates have demonstrated the usefulness of a pars plana vitrectomy, detaching the posterior hyaloid, air-gas/fluid exchange, laser photocoagulation, and gas tamponade in macular detachments associated with optic disc pits [51, 62, 65–72]. Silicon oil has also been used for tamponade [73]. However, the persistence of the inner layer separation or schisis may provide a reservoir of continuous fluid flow from the pit, causing recurrent outer layer detachment and worsening visual acuity [23]. Reversal of the dense central scotoma due to the outer layer detachment can occur after gas