Indications and visual outcomes of intrastromal corneal ring segment implantation in a large patient series

Visual Acuity Examination Methodology in Keratoconus

Visual acuity is one of the most important parameters for evaluating the vision of patients with keratoconus. This study reviewed 295 articles related to keratoconus published between 2017 and 2022 in which visual acuity was one of the parameters measured. The methodology of visual acuity testing in studies on keratoconus was thoroughly analyzed. The analysis showed that the most commonly indicated chart for testing visual acuity papers on keratoconus is the Snellen chart. It was shown that in 150 out of 295 articles, the authors do not describe the methodology for testing visual acuity. What is more, it was also shown that in 68 of the 295 articles which were analyzed, a procedure for converting visual acuity tested with a Snellen chart into a logMAR scale was used. In this review, we discuss the validity and reliability of such conversions. In particular, we show that insufficient description of visual acuity testing methodology and lack of information on the conversion of visual acuity results into the logMAR scale may contribute to the misinterpretation of visual acuity test results.

A Novel Mobile Application for Preoperative and Intraoperative Assessments of Intrastromal Corneal Ring Segments Implantation for Keratoconus

PURPOSE

To develop a mobile app that allows photographs to be captured and edited under the overlay of images and projection of a protractor with 360 degrees axis markings, which enables the surgeon to accurately visualize the programmed and marked alignment where the intrastromal corneal ring segments (ICRS) will be implanted, detecting possible marking errors.

METHODS

A codesign methodology was chosen to develop the Eye Axis Check application. After app development, measurements were obtained, and comparisons were made between manual marks and ICRS alignment with and without the app in 13 eyes that had undergone ICRS implantation for keratoconus. The mobile app was made available to 15 ophthalmic surgeons in different cities to assess its usability.

RESULTS

The users approved the developed application for ease of use and utility. No difference was found between the markings made manually and those made with the app, and the mean difference between ICRS centralization and assessment made by the app was 4.84 degrees (95% confidence interval: -5.32 to 15.01; P = 0.3193). On comparison of the agreement between app measurements and manual measurements for the ICRS centration, no significant differences were found, and excellent concordance (0.991) and a strong positive linear correlation (0.984) were observed.

CONCLUSIONS

A mobile app for preoperative planning and intraoperative ICRS alignment was developed and revealed to be useful and easy to use, allowing the surgeon to visualize the programmed alignment where the ICRS will be implanted.

One-year visual outcome of secondary piggyback pinhole device implantation in pseudophakic eyes with irregular corneal astigmatism and iris trauma

PURPOSE

Retrospective case series evaluating the efficacy and safety of implanting XtraFocus^™ pinhole device in pseudophakic patients with irregular corneal astigmatism with concurrent or standalone iris defect.

METHODS

Electronic case records were searched for: uncorrected distance visual acuities (UDVA) and corrected distance visual acuities (CDVA), automatic or manifest refraction and spherical equivalent (SE). All main outcomes were evaluated preoperatively and postoperatively at 1, 3, 6, 9 and 12 months, along with patients' satisfactory outcome and complications.

RESULTS

Eleven pseudophakic eyes of 11 patients with a mean age of 54 (range 27-81) years were included. Median UDVA improved significantly from logMAR 0.7 (range 0.1-1.22) pre-operatively to 0.4 (range 0-1.3) at 1-month (p = 0.002); median CDVA remained unchanged at logMAR 0.4 (range 0-0.1) pre-operatively and 0.4 (range 0-0.8) at 1-month (p = 0.36). There were no significant statistical differences in both UDVA and CDVA between the post-operative periods. Ten patients (90.9%) had initial UDVA improvement at 1-month post op. Eight (72.7%) patients expressed satisfaction with improved vision or reduction of glare/halos. Three (27.3%) patients had unsatisfactory visual outcome resulting in 2 requested for implant explantation due to worsening of glare and distressing floaters.

CONCLUSIONS

XtraFocus^™ is effective in improving vision or reducing glare in pseudophakic patients with irregular corneal astigmatism or intragenic iris trauma, with over 70% expressed satisfactory outcome. Disturbing floaters and glare preclude its use in some resulting in implant explantation.

Toric Artisan after transepithelial topography-guided photorefractive keratectomy for higher-order aberrations following intrastromal corneal ring segments in keratoconus - Trioptics

We report a case of a 40-year-old female with keratoconus and high myopia who had previous ICRS implantation in both eyes (OU) and was intolerant to contact lenses. Manifest refraction was -8.50 -1.50 × 95 (20/25--) in right eye (OD) and -9.50 -2.50 × 60 (20/70--) in left eye (OS). A topography-guided transepithelial-photorefractive keratectomy (ttPRK) was performed to correct high-order aberrations on OS, resulting in corneal surface and coma improvement, and CDVA achieved 20/30. Correction of residual ametropia was performed with an iris-fixated toric phakic lens in OU. CDVA improved to 20/20- (Plano) in OD and 20/20- (Plano -1.00 90°) in OS. In conclusion, it is possible to rehabilitate a patient with keratoconus and high ametropia after intrastromal corneal ring segments (ICRS) implantation associating ttPRK and phakic lens ("Trioptics").

Intracorneal Stromal Ring Can Affect the Biomechanics of Ectatic Cornea

Purpose

The biomechanical properties of ecstatic cornea undergo changes. This study evaluates the biomechanical changes of ecstatic cornea after implantation of two types of intracorneal stromal ring (ICR).

Methods

For doing this prospective cross-sectional study, 32 patients with keratoconus (KCN) were randomly divided into two 16-member groups (group I: MyoRing, group II: KeraRing). The main inclusion criteria were transparent cornea with no scar in the central part, corneal thickness >450 µ in the incision region, keratometry within 48–52 diopters, and progressive course of corneal thinning. Biomechanics of the cornea was evaluated by “ORA” and “Corvis” devices. All of the data were recorded and analyzed before implantation of the rings and 6 months thereafter.

Results

The mean ages of patients of groups I and II were 26 ± 6.55 and 33.86 ± 8.5, respectively. The postoperative change of sphere refraction was significant in both groups. However, reduction in the astigmatism was significant only in group I. In addition, the change of flat meridian keratometry (Kf) was significant before and after ring implantation in group I, unlike group II. The changes in CH and CRF parameters (ORA) were not significant in either group before and after the operation. Besides, only HRC parameter (Corvis) decreased significantly in both groups before and after the operation.

Conclusion

Both MyoRing and KeraRings have positive effects on the biomechanics of cornea at least during the first year after implantation. Comparison of these two types of ICR did not show significant differences in Corvis and ORA parameters.

Clinical outcomes after implantation of a new intrastromal corneal ring with 140-degree of arc in patients with corneal ectasia

AIM

To evaluate the clinical and tomographic outcomes after implantation of a new intrastromal corneal ring segment (ICRS) with 140-degrees of arc in eyes with corneal ectasia.

METHODS

We evaluated patients with corneal ectasia implanted with Ferrara 140° ICRS from April 2010 to February 2015. Outcome measures included preoperative and postoperative corrected distance visual acuity (CDVA), keratometry simulated (K) reading, tomographic astigmatism and asphericity. All patients were evaluated using the Pentacam Scheimpflug system.

RESULTS

The study evaluated 58 eyes. The mean follow-up was 16.81±10.8mo. The CDVA (logMAR) improved from 0.5±0.20 (20/60) to 0.3±0.21 (20/40) (P<0.01). The average K reduced from 49.87±7.01 to 47.34±4.90 D (P<0.01). The asphericity changed from -0.60±0.86 to -0.23±0.67 D (P<0.01). The mean preoperative tomographic astigmatism decreased from -8.0±3.45 to -4.53±2.52 D (P<0.01).

CONCLUSION

The new ICRS model with 140-degrees of arc effectively improve the visual acuity and reduce the high astigmatism usually found in patients with corneal ectasia.