ABNORMAL DISC SIZE
Small
Hypermetropia
Definition
- •
A very common, usually bilateral, condition associated with reduced axial length and smaller than normal scleral canal.
Signs
- •
Slightly elevated pink disc with a small or absent cup ( Fig. 12.1 ).
Fig. 12.1
- •
Crowding of central retinal vessels.
- •
Absence of capillary dilatation on the disc.
Look for
- •
Chorioretinal folds (rare).
- •
Shallow anterior chamber.
Differential diagnosis
- •
Early papilloedema.
- •
Buried drusen.
Tilted disc
Definition
- •
A common congenital condition frequently associated with myopia.
Signs
- •
Oval or D-shaped disc in which the axis is most frequently directed obliquely ( Fig. 12.2 ) but may be horizontal or nearly vertical ( Fig. 12.3 ).
Fig. 12.2
Fig. 12.3
- •
Situs inversus, in which the temporal vessels deviate nasally before turning temporally ( Fig. 12.4 ).
Fig. 12.4
- •
Hypopigmentation of the inferonasal fundus ( Fig. 12.5 ).
Fig. 12.5
Look for
- •
Temporal visual field defects are often present but visual acuity is usually normal.
Hypoplastic disc
Definition
- •
A congenital, unilateral or bilateral, condition that may be associated with a variety of ocular and systemic conditions ( Table 12.1 ).
Table 12.1
Associations of optic disc hypoplasia
- 1.
Ocular
- •
Albinism and foveal hypoplasia
- •
Axial myopia
- •
Microphthalmos
- •
Aniridia
- •
Persistent hyaloid artery
- •
- 2.
Maternal
- •
Drug ingestion during pregnancy (e.g. phenytoin, quinine, LSD, steroids)
- •
Intrauterine infections
- •
Diabetes mellitus
- •
- 3.
Neurological
- •
Isolated pituitary dysfunction
- •
Partial or complete absence of the septum pellucidum
- •
De Morsier syndrome
- •
Basal encephalocele
- •
Posterior fossa cyst
- •
Anencephaly
- •
Hydranencephaly
- •
Apert syndrome
- •
- 1.
Signs
- •
Small disc surrounded by a halo of pigmentary change (double-ring sign – Fig. 12.6 ).
Fig. 12.6
- •
Blood vessels have normal calibre although they are often tortuous ( Fig. 12.7 ).
Fig. 12.7
- •
In some cases only a part of the disc is hypoplastic ( Fig. 12.8 ).
Fig. 12.8
Large
High myopia
Definition
- •
Refractive error more than −6D and axial length more than 26 mm with a corresponding larger than normal scleral canal.
Signs
- •
The appearance of the large disc may be exaggerated by surrounding chorioretinal atrophy ( Fig. 12.9 ).
Fig. 12.9
Congenital pit
Definition
- •
An isolated, usually unilateral, congenital, condition that is associated with mild enlargement of the optic nerve head.
Signs
- •
The pit is a round or oval depression of variable size, most frequently involving the temporal margin of the disc ( Fig. 12.10 ).
Fig. 12.10
Look for
- •
Serous macular schisis and detachment ( Fig. 12.11 ) that eventually develops in about 30% of cases.
Fig. 12.11
Differential diagnosis of macular detachment
- •
Central serous retinopathy.
Coloboma
Definition
- •
A unilateral or bilateral, congenital, condition caused by failure of fusion of the fetal fissure that may be associated with a variety of ocular and systemic anomalies ( Table 12.2 ).
Table 12.2
Associations of optic disc coloboma
- 1.
Ocular
- •
Other colobomas
- •
Serous macular detachment
- •
Microphthalmos with cyst
- •
Persistent hyaloid artery
- •
Retinal dysplasia
- •
- 2.
Chromosomal disorders
- •
Patau syndrome (trisomy 13)
- •
Edward syndrome (trisomy 18)
- •
Cat-eye syndrome (trisomy 22)
- •
- 3.
Brain malformations
- •
Anencephaly
- •
Agenesis of corpus callosum
- •
Basal encephalocele
- •
- 4.
Other syndromes
- •
CHARGE
- •
Meckel–Gruber
- •
Goltz
- •
Lenz microphthalmos
- •
Aicardi
- •
Hallermann–Streiff–François
- •
Clefting
- •
Goldenhar
- •
- 1.
Signs
- •
The disc contains a partial inferior excavation that has a glistening appearance ( Fig. 12.12 ).
Fig. 12.12
Differential diagnosis
- •
Mild cases may be mistaken for glaucomatous cupping, but the splayed appearance of the central blood through the colobomatous area gives the clue.
Morning glory anomaly
Definition
- •
A usually unilateral, congenital, condition that may be associated with a variety of ocular and systemic anomalies ( Table 12.3 ).
Table 12.3
Associations of morning glory anomaly
- 1.
Ocular
- •
Aniridia
- •
Cataract
- •
Lens coloboma
- •
Persistent primary fetal vasculature
- •
Foveal hypoplasia
- •
Serous macular detachment
- •
- 2.
Uncommon systemic
- •
Hare lip and cleft palate
- •
Cranial vault anomalies
- •
Basal encephalocele
- •
Absent corpus callosum
- •
- 1.
Signs
- •
Large disc with a core of white tissue occupying the central area ( Fig. 12.13 ).
Fig. 12.13
- •
Blood vessels emerge from the edge of the disc in a spoke-like manner.
- •
The lesion itself is surrounded by an elevated annulus of chorioretinal pigmentary disturbance.
Megalopapilla
Definition
- •
A very rare usually bilateral congenital condition in which the disc diameter is 2.1 mm or more.
Signs
- •
Large cup–disc ratio with a round or horizontally oval cup without vertical notching ( Fig. 12.14 ).
Fig. 12.14
- •
Reduced distance between the temporal edge of the disc and the foveola by approximately one disc diameter.
Combined coloboma and pit
Signs
- •
Temporal pit and an inferior coloboma is an extremely rare anomaly ( Fig. 12.15 ).
Fig. 12.15
LARGE CUP
Large physiological excavation
Signs
- •
Large cup with a pink neuroretinal rim with absence of notching and bayoneting of blood vessels.
- •
The inferior neuroretinal rim is the broadest followed by the superior, nasal and temporal (‘ISNT’ rule – Fig. 12.16 ).
Fig. 12.16
- •
The striations of the peripapillary nerve fibre layer can be seen up to the disc margin.
Glaucomatous cupping
Signs
- •
Large cup with notching and thinning of the neuroretinal rim, and bayoneting of blood vessels ( Fig. 12.17 ).
Fig. 12.17
- •
‘ISNT’ rule is broken.
- •
Disc pallor and peripapillary atrophy.
- •
Retinal nerve fibre layer defects best seen with red-free light ( Fig. 12.18 ).
Fig. 12.18
Megalopapilla
- •
See above.
OPTIC ATROPHY
Primary
Pathogenesis
- •
A process affecting the visual pathways from the retrolaminar portion of the optic nerve to the lateral geniculate nucleus ( Table 12.4 ).
Table 12.4
Causes of primary optic atrophy
- 1.
Optic neuritis
- •
Multiple sclerosis
- •
Devic disease
- •
Schilder disease
- •
- 2.
Compression
- •
Bony
- •
Pituitary tumours
- •
Optic nerve tumours
- •
Aneurysm
- •
Orbital cellulitis
- •
- 3.
Primary hereditary optic atrophies
- •
Kjer syndrome (AD) presents in 1st or 2nd decades
- •
Behr syndrome (AR) presents in the 1st decade
- •
Wolfram syndrome (AR) – DIDMOAD = diabetes insipidus, diabetes mellitus, optic atrophy, and deafness; presents 1st or 2nd decades
- •
Leber hereditary optic neuropathy (mitochondrial) presents in the 2nd to 4th decades
- •
- 4.
Hereditary neurological disorders – present during the 1st decade
- •
Friedreich ataxia (AR)
- •
Charcot–Marie–Tooth disease (XL-D)
- •
Adrenoleukodystrophies (may be XL-R or AR)
- •
Cerebellar ataxia type I (AD)
- •
- 5.
Toxic
- •
Methanol
- •
Ethambutol
- •
Isoniazid
- •
- 6.
Nutritional deficiency
- •
Thiamine (tobacco-alcohol amblyopia and beriberi)
- •
Vitamin B12 (pernicious anaemia)
- •
Niacin (pellagra)
- •
- 7.
Trauma
- •
With or without optic nerve transection
- •
Retrobulbar haemorrhage
- •
- 1.
Signs
- •
White, flat disc with a clearly delineated outline ( Fig. 12.19 ).
Fig. 12.19
- •
Reduction in the number of small vessels on the disc.
- •
Attenuation of the peripapillary vessels.
- •
Thinning of the retinal nerve fibre layer.
Secondary
Pathogenesis
- •
Long-standing swelling of the optic nerve head.
Signs
- •
White or dirty grey slightly raised disc with poorly delineated margins ( Fig. 12.20 ).
Fig. 12.20
- •
Reduction in number of small vessels on the disc.
- •
Surrounding ‘water marks’.
Causes
- •
Chronic papilloedema.
- •
Anterior ischaemic optic neuropathy.
- •
Papillitis.
Consecutive
Pathogenesis
- •
Diseases of the inner retina or its blood supply ( Table 12.5 ).
Table 12.5
Fundus changes associated with consecutive optic atrophy
- 1.
Vascular attenuation or sheathing
- •
Old occlusion of the central retinal artery or ophthalmic artery
- •
Retinitis pigmentosa
- •
Toxic optic neuropathy
- •
Old vasculitis as in Behçet disease
- •
- 2.
Macular lesions giving rise to temporal disc pallor
- •
Toxoplasmosis
- •
Cone dystrophy
- •
- 3.
Chorioretinal atrophy
- •
Degenerative myopia
- •
Extensive panretinal photocoagulation
- •
- 4.
Diffuse retinal necrosis
- •
Cytomegalovirus retinitis
- •
Acute retinal necrosis
- •
Progressive outer retinal necrosis
- •
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