Objective quantification of corneal haziness using anterior segment optical coherence tomography

Corneal densitometry measurements comparison between anterior segment OCT and scheimpflug imaging

PURPOSE

To evaluate and compare the repeatability of corneal densitometry (CD) measurements obtained using both an anterior-segment optical coherence tomography (AS-OCT) device and a Scheimpflug camera system, while also assessing the level of agreement. The study also sought to investigate the correlation of CD with age, gender, and central corneal thickness (CCT) in normal eyes.

METHODS

CD measurements were obtained using the Casia 2 and the Pentacam AXL Wave. Data were collected on Total Corneal Densitometry and 4 concentric corneal annular areas, these are referred to as zone 1, denoting the central area, through to zone 4, designating the outermost peripheral region. Repeatability was assessed using intra-session test-retest variability, coefficient of variation (CoV), and intraclass correlation coefficient (ICC). The agreement was evaluated using Bland-Altman plots. Correlation analysis was performed between CD, age, gender, and CCT.

RESULTS

The study included 96 healthy volunteers. The Casia 2 demonstrated high repeatability with ICC values exceeding 0.9 in all the corneal zones and lower CoV values compared to the Pentacam AXL Wave (ranging from 1.07% to 2.25% for Casia 2 and from 1.91% to 6.89% for Pentacam).95% LoA were within ± 2 standard deviation from the average mean except from zone 1 (± 2.42).However, the measurements showed a consistent bias among all the corneal zones. CD values were positively correlated with age, except for zone 1 with the Pentacam (p = 0.083).

CONCLUSIONS

The findings suggest that the Casia 2 can be a reliable tool for assessing corneal transparency in healthy individuals, however its measurements are not interchangeable with those provided by the Pentacam. The AS-OCT device may be more sensitive in detecting subtle age-related changes in CD within the central zone.

Loss of TRPM8 Exacerbate Herpes Simplex Keratitis Infection in Mice by Promoting the Infiltration of CD11b+ Ly6G+ Cells and Increasing the Viral Load in the Cornea

Purpose

To reveal the role of transient receptor potential cation subfamily M member 8 (TRPM8) channels in herpes simplex keratitis (HSK).

Methods

HSK models were established using TRPM8 knockout (TRPM8-/-) mice and their wild-type (WT) littermates. The infected corneas were graded and harvested to evaluate the mRNA levels of inflammatory factors through quantitative real-time polymerase chain reaction (RT-PCR), as well as the infiltration of inflammatory cells through immunofluorescence staining and flow cytometry. Viral titers were determined by plaque assay and absolute quantitative method. RNA-sequencing was conducted to elucidate the transcriptome of corneal epithelium in response to TRPM8 knockout after infection. The anti-inflammatory effect of TRPM8 agonist menthol was documented via subconjunctival administration.

Results

Compared to their wild-type counterparts, TRPM8-deficient mice exhibited exacerbated infection symptoms and thicker corneas in HSK models. Infection in TRPM8-deficient mice resulted in significant lymphocyte infiltration, primarily consisting of Ly6G+ CD11b+ cells. Additionally, TRPM8-deficient mice displayed increased levels of corneal viral titers after infection, along with decreased expression of interferon-stimulated genes (ISGs). Subconjunctival administration of menthol effectively alleviated infection-induced symptoms and Ly6G+ CD11b+ cell infiltration in herpes simplex virus type 1 (HSV-1)-treated mice.

Conclusions

TRPM8 promoted host resistance to HSV-1 infection by suppressing the accumulation of Ly6G+ CD11b+ cells and virus replication. These findings suggest that targeting TRPM8 could be valuable for therapeutic interventions against HSV-1 infections.

Small incision lenticule extraction and femtosecond-assisted laser in situ keratomileusis in patients with deep corneal opacity: case series

AIM

To report the safety, efficacy, and accuracy of small-incision lenticule extraction (SMILE) or femtosecond-assisted laser in situ keratomileusis (FS-LASIK) for the correction of myopia or myopic astigmatism in patients with deep corneal opacity denoted by anterior segment optical coherence tomography (AS-OCT).

METHODS

Four patients with monocular corneal opacity (3 due to mechanical injury, 1 due to a firecracker wound) were recruited and treated with refractive surgery (3 for SMILE, 1 for FS-LASIK combined with limbal relaxing incision (LRI). Preoperative ocular manifestations, surgical details, postoperative visual outcomes, corneal opacity parameters, and corneal topography were analyzed.

RESULTS

Preoperatively, spherical diopter ranged from -3.0 D to -4.75 D with cylinder ranging from -0.75 to -5.0 D, and corrected distance visual acuity (CDVA) ranging from 20/25 to 20/20. One eye's corneal opacity was located in the central zone and three were in the mid-peripheral optical zone. Three patients underwent uneventful SMILE in both eyes, whilst one patient underwent FS-LASIK for high astigmatism in both eyes and LRI in the right eye. CDVA of the eye with corneal opacity ranged from 20/22 to 20/20 one to six weeks postoperatively. Two patients achieved better CDVA and no patients lost Snellen lines. The postoperative diopter was within ±0.75 D for all eyes. Significant edema existed above the corneal opacity in one eye and dissipated soon. No eccentric corneal topography or morphological anomaly of the corneal cap or flap was observed.

CONCLUSION

The cases demonstrate that SMILE or FS-LASIK is safe and effective to treat myopic astigmatism combined with deep corneal opacity lesions after comprehensive preoperative evaluation and appropriate candidate selection. FS-LASIK combined with LRI is also sufficient for correcting high astigmatism due to corneal scarring.

Case report: Utilization of neutral density filters for densitometry analysis of dense corneal opacities

Purpose

This report describes the technique of utilizing a neutral density filter (NDF) during Scheimpflug imaging of a dense corneal opacity in order to increase data acquisition success and improve data reliability for densitometry analysis.

Observations

A 49-year-old female with Steven-Johnson Syndrome secondary to sulfonamide use presented for routine follow up evaluation of her customized ocular surface prosthetic device (PD). Her ocular history was significant for mucous membrane grafting and limbal stem cell transplant in both eyes. The ocular surface examination of the left eye was notable for chronic dense neovascularization and scarring of the temporal and inferior cornea which extended into the visual axis. Scheimpflug imaging and densitometry analysis were performed in order to quantify the severity of the scar, however, there was significant difficulty in acquiring densitometry data. During a subsequent follow-up visit to monitor the scar, standardized room lighting and a neutral density filter were used to obtain reproducible and reliable imaging for densitometry analysis. The corneal scar was monitored over time using this standardized imaging protocol and by densitometry analysis minimal progression of the scar was evident, suggesting that recently documented significant vision loss in the left eye could not be attributed solely to changes in the scar.

Conclusion and Importance

The use of a neutral density filter along with standardized ambient lighting conditions when performing Scheimpflug imaging may be necessary to reliably monitor densitometry progression of clinically severe corneal opacities.

Inter-changeability Between Anterior Segment Optical Coherence Tomography and Scheimpflug Imaging in the Evaluation of Corneal Opacity

Purpose

To compare the results of corneal evaluation, either the total corneal thickness and corneal opacity depth by both technologies AS- OCT and Scheimpflug imaging by Sirius Scheimpflug placido topography.

Methods

sixty-eight eyes of sixty- eight consecutive patients with corneal opacities were examined by both AS-OCT and Sirius Scheimpflug imaging. Corneal thickness and corneal opacity depth were measured and compared determining the interchangeability using Bland–Altman plotting.

Results

Total corneal thickness was (470.32±62.10) and (463.47±56.47) by AS. OCT and Sirius Scheimpflug imaging, respectively (P value = 0.8).

While the actual measurement of corneal opacity, corneal opacity depth was (135.39±119) and (85.45±128) by AS-OCT and Siris Scheimpflug imaging respectively with P value (0.004).

Conclusion

AS-OCT and Scheimpflug imaging Sirius may be used interchangeably for measuring both total corneal thickness, while in the determination of corneal opacity depth. the AS-OCT is superior to Scheimpflug imaging in the accuracy of determination of actual boundaries of the corneal opacity.