Context:Subclinical keratoconus is contraindication to refractive surgery. The currently used methods of preoperative screening do not always allow differentiating between healthy eyes and those with subclinical keratoconus.Aim:To evaluate biomechanical parameters of the cornea, waveform score (WS), and intraocular pressure (IOP) as potentially useful adjuncts to the diagnostic algorithm for precise detection of the early keratoconus stages and selection of refractive surgery candidates.Settings and Design:Department of Ophthalmology and prospective cross-sectional study.Patients and Methods:Patients enrolled in the study were diagnosed with refractive disorders. We assessed parameters of corneal biomechanics such as corneal hysteresis (CH), corneal resistance factor (CRF), Goldman-correlated IOP (IOPg), corneal compensated IOP, WS, and keratoconus match index (KMI). They were classified into one of three groups based on the predefined KMI range: Group 1 (from 0.352 to 0.757) – 45 eyes, Group 2 (from −0.08 to 0.313) – 52 eyes, and Group 0 - control group (from 0.761 to 1.642) – 80 eyes.Results:In both study groups, IOPg, CRF, and CH were decreased when compared to control (P < 0.0001). In control group, there was positive correlation between CH and KMI (P < 0.05), with no correlations in any of the two study groups. CRF correlated positively with KMI in control (P < 0.0001) and in Group 2 (P < 0.05).Conclusions:CH and CRF, together with WS and IOPg, consist a clinically useful adjunct to detect subclinical keratoconus in patients referred for refractive surgery when based on KMI staging.

The role of corneal biomechanics in laser vision correction (LVC) is currently being raised in the assessment of postoperative corneal ectasia risk. The aim of the paper was to evaluate the changes in corneal biomechanics after LVC procedures based on a systematic review of current studies. The results of a search of the literature in the PubMed, Science Direct, Google Scholar, and Web of Science databases were selected for final consideration according to the PRISMA 2020 flow diagram. Included in our review were 17 prospective clinical studies, with at least 6 months of follow-up time. Corneal biomechanical properties were assessed by Ocular Response Analyzer (ORA), or Corvis ST. The results of the study revealed the highest corneal biomechanics reduction after laser in situ keratomileusis (LASIK) followed by small incision lenticule extraction (SMILE) and surface procedures, such as photorefractive keratectomy (PRK) or laser-assisted sub-epithelial keratectomy (LASEK). In SMILE procedure treatment planning, the use of thicker caps preserves the corneal biomechanics. Similarly, reduction of flap thickness in LASIK surgery maintains the corneal biomechanical strength. Future prospective clinical trials with standardization of the study groups and surgical parameters are needed to confirm the results of the current review.

To define the influence of air, SF6 gas and silicon oil 1000cs tamponade injection and oil tamponade removal on corneal biomechanics, central corneal thickness and intraocular pressure. 77 eyes referred to vitrectomy were divided into 4 groups: 19 to air tamponade, 21 to SF6 tamponade, 19 to oil tamponade, 18 to oil tamponade removal. Pre- and postoperative corneal hysteresis, corneal resistance factor, corneal thickness, Goldman intraocular pressure (GAT) and corneal compensated intraocular pressure (IOPcc) were analysed. GAT and IOPcc did not change after the air or SF6 tamponade. The oil tamponade injection caused increase in GAT and IOPcc, while the oil removal caused reduction in those parameters. In all groups, preoperative and postoperative values of GAT and IOPcc did not differ. There was no change in corneal thickness and biomechanics after air, SF6 or oil tamponade while after removal of oil those parameters are decreased. The air, SF6 and oil tamponade does not change the corneal thickness and corneal biomechanics. The removal of oil causes decrease in corneal thickness and biomechanics which can lead to bias in intraocular pressure measurement. GAT and IOPcc did not differ in eyes pre- and post-vitrectomy, being similarly reliable measure.

The role of corneal biomechanical properties in patients referred to laser vision correction (LVC) is currently being raised. Understanding of corneal biomechanics may support the proper selection of refractive surgery candidates, improve the refractive outcomes and safety of refractive procedures. The Ocular Response Analyzer (ORA) and Corvis ST are commonly used devices to assess corneal biomechanical parameters in LVC. The vertical corneal incisions have a greater impact on corneal biomechanics weakening than horizontal incisions. Maintaining the high biomechanical strength of the cornea following LVC can decrease the potential risk of postoperative ectasia.

Purpose: To determine the pathomechanism of increased intraocular pressure after penetrating and lamellar keratoplasty based on clinical observation and literature data. Materials and methods: Morphometric analysis of the anterior segment of the eye using spectroscopic optical coherence tomography, gonioscopy and biomicroscopy. Results: Pre- and postoperative spectroscopic optical coherence tomography scans in patients after keratoplasty reveal deformation of the peripheral cornea, narrowing of the iridocorneal angle, presence of anterior synechiae and various types of pupillary block. Conclusions: The mechanism of elevated intraocular pressure after corneal grafting is complex and depends on pre-, intra- and postoperative factors, such as anatomy changes of the iridocorneal angle, presence of anterior synechiae, as well as anterior and posterior pupillary block. Spectroscopic optical coherence tomography plays an important role in diagnosis and further treatment management.