This paper compares corneal biomechanical parameters among three groups - patients suffering from delayed-onset mustard gas keratitis (DMGK), chronic corneal scarring and normal group- by Corvis ST device.

Forty- five eyes of the patients in 3 groups of DMGK , chronic corneal scarring and normal cornea were enrolled in this study. After assessing the criteria all patients were under undergone slit lamp and corneal biomechanical parameters achieved by Corvis ST. Corneal biomechanical parameters included Time of Applanation 1 (AT2), Length of Applanation (AL1), Velocitgy of Applanation (AV1), Time of Applanation 2 (AT2), Length of Applanation 2 (AL2), Velocity of Applanation 2 (AV2), Deformation Amplitude (DA), Highest Concavity-Time (HCT), Peak Distance (PD), Highest Concavity Radius (HCR), Central Corneal Thickness (CCT), IOP Corrected and IOP Non-Corrected

The mean age was 49.20 + 5.16, 60.40 + 22.92 and 44.60 + 8.32 years for DMGK, chronic corneal scarring and normal group, respectively. There was a significant difference between DMGK and Scaring group between the range of AT1, AT2, IOP corrected and IOP Non-Corrected parameters; likewise, there was a considerable difference in AT1,AT2, HCR,DA, and IOP non-corrected while comparing DMGK and normal group; nevertheless, no meaningful difference was observed while comparing the scarring and normal group.

It seems that due to decreasing level of corneal rigidity and stiffness, DMGK's cornea is more easily applanated, and it lasts a longer time to turn back to its initial condition. Moreover, they showed less intraocular pressure compared with normal population, therefore, the mis-diagnosis of glaucoma is probable is this group.