Evaluation of corneal biomechanical changes after intrastromal corneal ring segment implantation in keratoconus patients using Corvis Oculus
Hesam Hashemian1 , Mehdi Khodaparast1 *, Mohammadnaser Hashemian1 , Sima Sheikhghomi1 , Kianoush Shahraki1 , Hooman Ahmadzadeh2
- Farabi Eye Hospital, Tehran University of Medical Sciences
- Tehran University of Medical Sciences
Abstract: Intrastromal corneal ring segment (ICRS) implantation is used as a safe and reversible surgical option in eyes with keratoconus. ICRS surgery is not a penetrating intervention, however, it needs manual or femtosecond laser-assisted stromal tunnels. The purpose of this study was to investigate whether ICRS could hinder progress of keratoconus or strengthen the biomechanical strength of cornea.
Methods: We recruited the patients with keratoconus who were candidates for ICRS implantation surgery in our hospital between January 2019 and July 2020. Patients with any history of ocular diseases and surgery, connective tissue disorders, pregnancy or lactation and CDVA less than 7/10 were excluded. Central corneal thickness, intraocular pressure, corneal inferior-superior steepening value, and also biomechanical parameters which could be obtained by Corvis Oculus including highest concavity deformation amplitude (HCDA), flattened segment length in the first and second applanations (A1L & A2L), highest concavity radius (HR), velocity of corneal displacement in the first and second applanations (A1V & A2V), peak distance between corneal edges at highest concavity (HCPD), corneal stiffness parameter at first applanation (SP-A1), deformation amplitude ratio (DA.ratio), Ambrósio Relational Thickness over the horizontal meridian (ARTh), Integrated radius (IR), and Corvis biomechanical index for detection of keratoconus (CBI) were recorded before and 6 months after surgery. All patients underwent Keraring implantation by manual technique by the same surgeon.
Results: In the total of 26 eyes, UDVA, CDVA, K max, I-S value improved significantly. CCT and IOP did not change significantly. The results of analysis of biomechanical parameters revealed that most of the biomechanical parameters had no statistically significant changes, except 2 parameters. One of them was ARTh which decreased in patients from the mean of 161.49 ± 31.58 to 126.16 ± 41.64 after the surgery with a P-value of 0.001. The other one was HR which decreased significantly from the mean of 6.42 ± 1.13 to 6.00 ± 1.26 with a P value of 0.022.
Conclusion: Results indicate that ICRS have no significant effect on corneal biomechanics and crosslinking should be considered in progressive or young patients.
