Posters

Comparaitive study of Goldmann applanation tonometer and Corvis ST in patients undergoing accelerated collagen cross-linking (KXL)

Poster Details

First Author: N. Ds INDIA

Co Author(s):    V. Bhandari   S. Arun   S. Ganesh              

Abstract Details

Purpose:

To assess and compare Intra ocular pressure(IOP) changes Pre and Post accelerated Corneal collagen crosslinking using Riboflavin (C3R- KXL) using Goldmann Applanation tonometer(GAT) and Scheimpflug based CORVIS ST tonometer and also evaluate the changes in corneal biomechanics before and after the procedure.

Setting:

Single centre prospective case series Nethradhama Superspeciality Eye Hospital

Methods:

The study included 12 eyes of 12 patients with progressive Keratoconus central corneal thickness >400µm and astigmatism <3D. Accelerated Crosslinking was done with 0.1% Riboflavin instilled in the eye every 2 mins for 20 mins , UV-A radiations of 365nm energy of 5.4J/cm2 and irradiance of 30mW/cm2 delivered for 3 minutes using Avedro c3r kxl machine. Mean follow up was at 6 months and at each follow up UDVA(uncorrected distant visual acuity), CDVA(corrected distant visual acuity), corneal topography to assess average Keratometry value, IOP using GAT and IOP and corneal biomechanical changes using Corvis ST tonometer were done.

Results:

Corvis ST tonometer showed a significant difference of 1.042 mmHg( p = 0.022) in intra ocular pressure (without pachymetric correction) and a difference of 1.058 mmHg(p=0.021) before and after KXL.Before and after KXL GAT showed an IOP change of -0.583 mmHg and IOP corrected for Central corneal thickness(CCT) showed a change of -0.667 mmHg. There was a significant change of 4.917µm (p= 0.019) on Pachymetry and 0.092m/s (p<0.001) change in Applanation velocity 2.

Conclusions:

CORVIS ST can be an excellent, easy and less cumbersome alternative to GAT with the added benefit of information on corneal biomechanics and an inbuilt calculation of Pachymetry corrected IOP. It can also been used as a tool to measure IOP post surgery as it is a Scheimpflug based non contact tonometry and can reduce the corneal surface damage associated with GAT. However, we need further long term studies to validate our outcome.

Financial Disclosure:

NONE