Table 1

Differentiating clinical features of corneal ectasias20

CharacteristicsKeratoconusPMDKeratoglobusTMD
FrequencyMost commonLess commonRareRare
LateralityUsually bilateralBilateralBilateralUsually bilateral
Age at onsetPuberty20–40 yearsUsually at birth20–40 years
ThinningInferior paracentralInferior band 1–2 mm wideMaximum in peripherySuperior cornea
ProtrusionThinnest at apexSuperior to band of thinningGeneralisedNone
Iron lineFleischer ringSometimesNoneNone
ScarringCommonOnly after hydropsMildLess common (vascularisation and lipid deposition seen)
StriaeCommonSometimesSometimesNone
  • PMD, pellucid marginal degeneration; TMD, Terrien’s marginal degeneration.