Posterior keratoconus is a rare, non-inflammatory thinning of the posterior cornea that is usually congenital and unilateral. It can be associated with corneal opacity or pigment deposits on the back of the cornea. Ultrasound biomicroscopy and anterior segment OCT can be used to confirm the diagnosis. The cause is thought to be a developmental defect involving delayed separation of embryonic tissues. It may occur with other ocular abnormalities or as part of a genetic syndrome. Treatment depends on the severity but may include refractive correction, grafting, or penetrating keratoplasty.

1. Dr. K. Vasantha M.S.,F.R.C.S
Director RIO Chennai Rtd

2.  Non inflammatory, non progressive ectasia of the
posterior surface of the cornea
 Rare
 May be associated with opacification of the cornea
 Usually congenital
 Mostly unilateral
 Familial incidences reported

3.  Keratoconus posticus generalis- the cornea will be clear.
Hence difficult to diagnose. Pachymetry will be needed
to diagnose and to assess the amount of defect
 Keratoconus posticus circumspectus is of two types.
Either central or paracentral
 In this type opacity is common. Pigment deposits also
will be seen.
 Visible with retro illumination
 UBM and AS-OCT will confirm the diagnosis

4.  ? Cleavage abnormality
 ? Mild form of Peters anomaly
 The presence of anterior lens abnormalities suggest
delayed separation of surface ectoderm from lens
epithelium
 Pigments on the back suggest delayed separation of the
iris epithelium

5.  ? Mesenchymal dysgenesis
 Delayed separation causing defects in migration of
mesenchyme in to the a.c
 So development of the endothelium is affected causing
defective development of the stroma
 In familial cases systemic associations are seen. But no
genetic associations have been noted

6.  Anterior lenticonus
 Anterior polar cataract
 Congenital cataract
 Indentation of the anterior surface of the lens
 Optic nerve coloboma, tilted disc
 Macular scarring

7.  Extra ocular – ptosis, proptosis, hypertelorism, squint
 Anterior chamber may be shallow
 Iris – Synechiae, atrophy, iridoschisis, coloboma
 Systemic- waddling gait, barrel chest, webbed neck
 Maxillary hypoplasia, large head, cleft palate,
preauricular pit, deafness
 Short arms
 Hypothyroid, amenorrhea, absence of uterus
 Mental retardation

8. Keratoglobus Posterior keratoconus
 Rare
 Bilateral
 Thinning is more in the
periphery
 Generalized protrusion
 Mild or no scar
 Striae very rare
 Very rare
 Usually unilateral
 Paracentral and posterior
 No protrusion
 Scarring is common
 No striae

9.  This condition is usually bilateral
 Begins after the age of 20
 There is an inferior band of thinning
 The bulge is above the band of thinning
 Scarring is rare (only if hydrops occur)
 Stromal striae may be seen

10.  Any refractive error if present must be corrected.
 Prevent amblyopia
 For a localized opacity rotation graft can be done
 If it is too large penetrating keratoplasty
 It must be remembered that IOL power calculation is
difficult in these cases as corneal power will be over
estimated

11.  Rarely thinning can occur following injury or infection
 Will be unilateral