Noor Eye Training center - NETC

Cavitary Anomalies of The Optic Disc:
▪️Excavated optic disc anomalies include megalopapilla, peripapillary staphyloma, optic disc coloboma, optic pit, and morning glory disk anomaly (MGDA).
▪️The optic disc anomaly seen in periventricular leukomalacia (PVL) and papillorenal syndrome are also often considered as cavitary anomalies of the optic disc.
▪️In the MGDA and peripapillary staphyloma, a congenital excavation of the peripapillary fundus surrounds and incorporates the optic disc.
▪️Ipsilateral intracranial vascular dysgenesis is seen in some patients with MGDA suggesting that MGDA results from a primary vascular dysgenesis with resulting mesenchymal abnormality.
▪️Peripapillary staphyloma appears to arise as a sequel to a localized disturbance in scleral development.
▪️Optic disc colobomas comprise a clearly demarcated bowl-shaped excavation of the optic disc, generally decentered and deeper inferiorly.
▪️Colobomas result from abnormal fusion of the two sides of the proximal end of the optic cup. They may be accompanied by multiple systemic conditions including the CHARGE association, Walker–Warburg syndrome, Goltz’ focal dermal hypoplasia, and Aicardi syndrome.
▪️Optic disc colobomas may be associated with PAX2 gene mutations as part of the papillo-renal or renal-coloboma syndrome (bilateral optic disc anomalies associated with hypoplastic kidneys).
▪️However, coloboma seems to be an inappropriate terminology to use in the papillo-renal syndrome as there is no evidence that the optic fissure fails to close.
▪️On the contrary, the optic disc anomaly in this condition has been shown to be a form of hypoplasia resulting from hereditary vascular dysgenesis affecting the ocular circulation.
▪️The optic disc cavitation seen with PVL (an abnormally large optic cup and a thin neuroretinal rim contained within a normal-sized optic disc) is also considered by some as a form of segmental optic nerve hypoplasia resulting from retrograde degeneration of axons secondary to injury to optic radiation after the scleral canals have established normal diameter.
▪️Megalopapilla is a generic term for an abnormally large optic disc that does not have the inferior excavation of an optic disc coloboma or the features of a MGDA. It is believed to result from altered optic axonal migration early in embryogenesis.
▪️Optic pit consists of a dysplastic retina that has herniated posteriorly into a collagen-lined pocket through a defect in the lamina cribrosa. The pathogenesis of optic pits is unclear. They are unassociated with systemic anomalies.

Vogt’s striae versus Haab’s striae:
▪️Vogt’s striae are vertical folds at the level of the posterior stroma and Descemet’s membrane, seen in patients of Keratoconus.
➖They occur in the area of maximal thinning and are best seen with a wide slit-lamp beam.
➖These are stress lines that can be made to disappear with gentle pressure at the limbus.
▪️Haab’s striae, or Descemet’s tears, are horizontal breaks in the Descemet membrane seen in primary congenital glaucoma. Haab’s striae are named after Otto Haab.
➖Haab’s straie are usually peripheral tears, concentric with limbus and appear as lines with double contour.
➖Haab’s striae, often oriented horizontally
or curvilinearly, are found in ~25% of eyes diagnosed with primary infantile glaucoma at birth, and in more than 60% of those diagnosed at 6 months of age.

Hirshburg corneal reflex test.

Large, mutton fat Keratitic precipitates (KPs)—seen in granulomatous uveitis with its Distribution — Inferior quadrant—base down triangle “Arlt’s triangle”under the influence of gravity and aqueous convection currents.