Relevance of Swept-Source Anterior Segment Optical Coherence Tomography for Corneal Imaging in Patients With Flap-Related Complications After LASIK

Late approach for LASIK flap striae

A 24-year-old man was referred for postrefractive surgery evaluation. The patient had a history of uneventful laser in situ keratomileusis (LASIK) in both eyes 3 months previously. According to the surgeon who originally performed the surgery, on slitlamp examination, only microstriae in the left eye was detected on postoperative day 1 and a more conservative follow-up approach was adopted without further immediate intervention. The patient returned only 3 months after surgery, complaining of low vision in the left eye that, according to the patient, had been present since postoperative week 2. The patient was then referred for examination and surgical procedure with a diagnosis of significant postoperative striae. The slitlamp examination revealed a LASIK flap with striae, epithelial filling, and a wrinkled appearance (Figure 1JOURNAL/jcrs/04.03/02158034-202312000-00017/figure1/v/2023-11-20T151558Z/r/image-tiff). There were no signs of infection or inflammation. Originally, the LASIK flap was programmed to be 110 μm. Preoperative manifest refraction in the right eye was -5.25 (20/20) and in the left eye was -5.25 (20/20). Assuming it is a case of late-approach LASIK flap striae, how would you proceed? Would you try to hydrate and lift the flap and just reposition it? Would you avoid lifting and associate phototherapeutic keratectomy (PTK) with excimer laser on top of the flap? Would you consider topo-guided surgery with regularization of the visual axis or even amputation of the flap?

Noninvasive diagnosis of oral squamous cell carcinoma by multi-level deep residual learning on optical coherence tomography images

BACKGROUND

Oral Squamous Cell Carcinoma (OSCC) is one of the most severe cancers in the world, and its early detection is crucial for saving patients. There is an inevitable necessity to develop the automatic noninvasive OSCC diagnosis approach to identify the malignant tissues on Optical Coherence Tomography (OCT) images.

METHODS

This study presents a novel Multi-Level Deep Residual Learning (MDRL) network to identify malignant and benign(normal) tissues from OCT images and trains the network in 460 OCT images captured from 37 patients. The diagnostic performances are compared with different methods in the image-level and the resected patch-level.

RESULTS

The MDRL system achieves the excellent diagnostic performance, with 91.2% sensitivity, 83.6% specificity, 87.5% accuracy, 85.3% PPV, and 90.2% NPV in image-level, with 0.92 AUC value. Besides, it also implements 100% sensitivity, 86.7% specificity, 93.1% accuracy, 87.5% PPV, and 100% NPV in the resected patch-level.

CONCLUSION

The developed deep learning system expresses superior performance in noninvasive oral squamous cell carcinoma diagnosis, compared with traditional CNNs and a specialist.

Clinical applications of anterior segment swept-source optical coherence tomography: A systematic review

Optical coherence tomography (OCT) is a non-invasive method that provides the opportunity to examine tissues by taking cross-sectional images. OCT is increasingly being used to evaluate anterior segment (AS) pathologies. Swept-source (SS) OCT allows greater penetration and achieves better visualization of the internal configuration of AS tissues due to the longer wavelength employed and high scan speeds. We reviewed the utilization of AS SS-OCT in various conditions including glaucoma, ocular surface pathologies, iris tumors, refractive surgery, cataract surgery, and scleral diseases. A systematic literature search was carried out on PubMed, Scopus, and Web of Science databases between January 1, 2008, and September 1, 2022 using the following keywords: AS SS-OCT; dry eye and SS-OCT; ocular surface and SS-OCT; cornea and SS-OCT; dystrophy and SS-OCT; glaucoma and SS-OCT; ocular surface tumors and SS-OCT; conjunctival tumors and SS-OCT; refractive surgery and SS-OCT; cataract and SS-OCT; biometry and SS-OCT; sclera and SS-OCT; iris and SS-OCT; ciliary body and SS-OCT; artificial intelligence and SS-OCT. A total of 221 studies were included in this review. Review of the existing literature shows that SS-OCT offers several advantages in the diagnosis of AS diseases. Exclusive features of SS-OCT including rapid scanning, deeper tissue penetration, and better image quality help improve our understanding of various AS pathologies.

'Infolded' LASIK flap: an unusual variant of early postoperative flap dislocation

Flap displacement is a rare but vision-threatening complication of laser-assisted in situ keratomileusis (LASIK). A young male patient underwent uneventful microkeratome-assisted LASIK. One-week postoperatively, flap displacement was noted in his right eye with its lower edge folded inwards, macrostria at the superior edge and the epithelium covering the bare stroma and into the interface. Anterior segment optical coherence tomography (AS-OCT) delineated the morphology of the displaced flap and the extent of epithelial ingrowth. The flap was repositioned by unrolling the fold and all the exposed surfaces were debrided to remove the epithelial ingrowth. Two months later, his corrected distance visual acuity improved to 20/30, and a smooth surface could be achieved. Infolded LASIK flap is a rare complication, which requires timely surgical intervention to achieve successful anatomical and functional outcomes. AS-OCT can be pivotal in determining the extent of infolding as well to delineate the extent of epithelial ingrowth within the interface.

Comparison of Flap Characteristics Created with Two Different Methods in Laser in Situ Keratomileusis (LASIK)

BACKGROUND

The creation of corneal flap is considered to be the most critical part of laser in situ keratomileusis (LASIK) surgery. Currently, flaps can be created with mechanical micorkeratomes or femtosecond lasers.

OBJECTIVE

To analyze and compare flap characteristics created with two different methods for flap creation in Laser in situ keratomileusis (LASIK).

METHODS

This was a retrospective study. The thickness and morphology of the flap were compared between the two mechanical microkeratomes (group I - Moria M2, group II - Moria SBK One Use Plus) and femtosecond laser (group III - Ziemer Femto LDV). Central flap thickness was measured intraoperatively, while the flap profile was measured with anterior optical coherence tomography at two axes (90° and 180°) and 5 measuring points on the first day, the first week, and one month after the surgery.

RESULTS

Central flap thickness was 110.91±15.79 micrometers (µm) (80-164 µm) in group I, 98.08±13.33 µm (65-136 µm) in group II and 103.52±13.89 µm (66-138 µm) in group III. Anterior optical coherence tomography revealed a meniscus-shaped flap in all three groups at both axes (90° and 180°). The least variability in flap thickness was observed in group III (±6 µm).

CONCLUSION

All three methods of flap creation provide good shape and thickness reproducibility. Ziemer Femto LDV femtosecond laser had the least variable flap thickness in a single flap. Mechanical microkeratomes had slightly lower performance.

Evaluation and management of a spontaneous corneal rupture secondary to pellucid marginal degeneration, using swept-source anterior segment optical coherence tomography

We describe a case of bilateral spontaneous corneal perforation secondary to pellucid marginal degeneration and present the associated swept-source anterior segment optical coherence tomography (SS-ASOCT) findings and management principles used.

A 47-year-old woman presented with ocular pain, redness, foreign body sensation and clear discharge in the right eye in 2017 and with very similar symptoms in 2019 in the left eye. Clinically she had a corneal perforation at the inferior cornea with associated loss of anterior chamber volume. Corneal topography demonstrated peripheral thinning and steepening in the contralateral eye. ASOCT images revealed full-thickness perforation, iridocorneal touch and iris stranding. The patient was managed with a combination of contact bandaging and corneal gluing.

SS-ASOCT is a useful adjunctive tool in the clinical assessment and evaluation of spontaneous corneal perforation. Alongside the clinical evaluation, it can be used to monitor the clinical response.

Clinical role of swept source optical coherence tomography in anterior segment diseases: a review

PURPOSE

To note the comprehensive role of swept source anterior segment optical coherence tomography (SS-ASOCT) in anterior segment diseases.

METHODS

A systematic literature search was carried out on various medical databases using the keywords, swept source anterior segment optical coherence tomography; SS-ASOCT; Cornea and SS-ASOCT; SS-ASOCT and glaucoma; SS-ASOCT and cataract; SS-ASOCT and biometer; SS-ASOCT and tear film and ocular surface.Original works and novel reports describing the potential role of SS-ASOCT in various anterior segment conditions were included.

RESULTS

After a thorough assessment of literature, it was clear that the SS-ASOCT did provide newer insights into many anterior eye conditions. The rapid scan acquisition, deeper tissue penetration, and higher magnification did enhance many of our understandings, which were previously not possible. In addition, lenticular assessment under complex clinical scenarios with automated values on objective scale has made it a worthy tool with immense future possibilities.

CONCLUSIONS

SS-ASOCT unveiled various anterior segment findings which were of clinical importance.

Identification of oral cancer in OCT images based on an optical attenuation model

Surgery is still the first choice to treat oral cancer, where it is important to detect surgical margins in order to reduce cancer recurrence and maintain oral-maxillofacial function simultaneously. As a non-invasive and in situ imaging technique, optical coherence tomography (OCT) can obtain images close to the resolution of histopathology, which makes it have great potential in intraoperative diagnosis. However, it is not enough to find surgical margins accurately just observing OCT images directly and qualitatively. The purpose of this study is to identify oral cancer in OCT images by investigating the quantitative difference of cancer and non-cancer tissue. Based on an available optical attenuation model and the axial confocal PSF of a home-made swept source OCT system, by using fresh ex vivo human oral tissues from 14 patients of oral squamous cell carcinoma (OSCC) as the samples, diagnosis with sensitivity (97.88%) and specificity (83.77%) was achieved at the attenuation threshold of 4.7 mm^-1, and the accuracy of identification reached 91.15% in our study. Our preliminary results demonstrated that the oral cancer resection will be guided accurately and the clinical application of OCT will be further promoted by deeply mining the information hidden in OCT images.

Corneal cross-linking as a treatment for corneal dystrophy with secondary bacterial infection in a Friesian horse

Corneal cross-linking should be considered as treatment option in Friesian horses with infectious keratitis and corneal dystrophy. Optical coherence tomography, giving information of corneal structure, can help for diagnosis and monitoring.

Flap Sliding Technique for Managing Flap Striae following Laser In Situ Keratomileusis

Purpose

To assess the efficacy and safety of a simple, noninvasive, "flap-sliding" technique for managing flap striae following laser in situ keratomileusis (LASIK).

Methods

This prospective, interventional study included eyes with post-LASIK flap striae. All eyes underwent flap sliding 1-2 days after surgery. Following flap edge epithelialisation, a cellulose sponge was used to gently slide the flap perpendicular to the striae direction. This technique allows for flap striae treatment without flap lifting, avoiding any associated lifting complications. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and refractive error were monitored one day after the flap-sliding procedure.

Results

Fifteen eyes (15 patients) with post-LASIK flap striae were managed using the flap-sliding technique. The procedure did not successfully relocate the flap striae in 1 eye, and flap elevation and floating (using a balanced salt solution) were required. Therefore, 14 eyes were included in post-flap-sliding analyses. The UDVA improved in all patients the first day after the flap-sliding procedure was performed, with 11 of 14 eyes (78.57%) reaching an UDVA of 20/25 or better. Complications following flap sliding occurred in 2 eyes (14.29%). One eye had intraoperative epithelial abrasion, and 1 eye had residual postoperative striae outside of the optical zone.

Conclusion

The flap-sliding technique is a simple, noninvasive, efficient, and safe technique for managing post-LASIK flap striae that develop after epithelial healing in the early post-LASIK period. This trial is registered with NCT04055337.

Appearance of herpes simplex keratitis on anterior segment optical coherence tomography

PURPOSE

To describe the anterior segment AS-OCT findings of herpetic simplex keratitis.

METHODS

Forty-two eyes of 42 patients with proven herpetic keratitis of varying severity were included in this prospective, observational, non-comparative case series study. All subjects underwent ophthalmologic examination and AS-OCT imaging.

RESULTS

Twenty-five of the 42 eyes (59.5%) had sub-epithelial infiltrates. In 11 of these cases, the overlying epithelium appeared intact, but in 14 cases, hydropic changes, heaping, and defects were observed. Seventeen eyes (40.5%) showed stromal involvement: six cases with scar at presentation and one case associated with uveitis. Stromal infiltrates were also seen, in ten cases, as a diffuse or local lentiform or spindle-shaped hyper-reflective area in the stroma.

CONCLUSION

Herpetic keratouveitis has characteristic features on AS-OCT images. This study demonstrates that herpetic keratitis also has characteristic AS-OCT features, including sub-epithelial infiltration and specific stromal hyper-reflective patterns. These features are not unique to herpetic keratitis, but AS-OCT imaging may provide useful supplementary information for diagnosing and monitoring herpetic keratitis.

Anterior Segment Optical Coherence Tomography: Applications for Clinical Care and Scientific Research

Anterior segment optical coherence tomography (AS-OCT) is a non-contact imaging technique that produces high-resolution images and quantitative measurements of the anterior segment and its anatomical structures. There has been rapid development of OCT technology over the past 2 decades, with the transition from time-domain to Fourier-domain OCT devices. By integrating these advancements in OCT technology, AS-OCT devices have evolved into versatile clinical and research tools for studies of the anterior segment and ocular surface. The primary purpose of this article was to review OCT technology and AS-OCT devices as well as applications of AS-OCT for clinical practice and scientific research. We first describe the different types of OCT technology, how they have been adapted for AS-OCT imaging, and differences between various AS-OCT devices. We then review the applications of AS-OCT for characterizing the anatomical structures of the anterior segment and aqueous outflow pathways, including the anterior chamber angle, trabecular meshwork, and Schlemm canal. We also describe glaucoma-related applications of AS-OCT imaging, which include evaluating patients for static and dynamic biometric risk factors of primary angle closure disease and assessing the efficacy of glaucoma interventions, such as laser peripheral iridotomy and glaucoma surgery. Finally, we review other clinical applications of AS-OCT imaging for detection and management of diseases of the ocular surface, cornea, and lens.