Intraoperative changes in corneal structure during excimer laser phototherapeutic keratectomy (PTK) assessed by intraoperative optical coherence tomography

Excimer Laser Phototherapeutic Keratectomy for Anterior Corneal Opacification After Descemet Membrane Endothelial Keratoplasty

PURPOSE

The aim of this study was to assess the long-term outcome of excimer laser phototherapeutic keratectomy (PTK) for treating remaining anterior corneal opacities after Descemet membrane endothelial keratoplasty (DMEK).

METHODS

This cohort study analyzed 67 eyes of 66 patients undergoing PTK in addition to and after DMEK between 2012 and 2021 at the Department of Ophthalmology, University of Cologne. Patients who were treated by PTK after previous DMEK on the same eye were included. The outcome parameters were best corrected visual acuity (BCVA), changes in refraction, endothelial cell density, corneal densitometry, central corneal thickness, and total corneal higher order aberrations. Patients with visual limitations in addition to anterior opacification were analyzed separately for their visual outcome. Eyes with severe visual limitations that have a very limited visual potential were excluded from the study. In addition, patients with not at least 1 postoperative follow-up examination were excluded from the study.

RESULTS

In this study, 67 eyes of 66 patients met all inclusion criteria. The median follow-up period was 13.1 (quartiles: 4.1; 30.7; interquartile range 26.6) months. The mean (±SD) BCVA improved from (logarithm of the minimum angle of resolution) 0.54 (±0.32) to 0.38 (±0.27) at the first postoperative visit ( P < 0.001) and remained significantly improved at all follow-up examinations compared with preoperative BCVA. Refraction and endothelial cell density did not change significantly after PTK. There was a significant decrease in corneal backscatter in the anterior corneal layer ( P < 0.001), and the total higher order aberration ( P = 0.02) and central corneal thickness were significantly reduced at the most recent postoperative visit ( P < 0.001). No immune reactions were observed.

CONCLUSIONS

Excimer laser PTK after DMEK for persisting anterior corneal opacities has the potential to significantly improve patients' vision without affecting refractive parameters or endothelial cell density.

Phototherapeutische Keratektomie bei rezidivierenden Hornhauterosionen verschiedener epithelialer Genese: Einfluss der Ablationstiefe auf Pachymetrie und Refraktion

Einführung

Die phototherapeutische Keratektomie gilt heute als etabliertes Therapieverfahren für Patienten, welche unter therapierefraktären genetisch bedingten Hornhautdystrophien oder rezidivierenden Erosiones ohne zugrunde liegende Basalmembrandystrophie leiden.

Ziel der Arbeit

Ziel der Arbeit war es, Änderungen der Refraktion und der Pachymetrie nach phototherapeutischer Keratektomie bei Patienten, welche eine epitheliale Basalmembrandystrophie oder rezidivierende Erosiones ohne zugrunde liegende Basalmembrandystrophie (traumatisch/nichttraumatisch bedingt) aufweisen, zu analysieren.

Material und Methoden

Die Patientendaten wurden retrospektiv aus dem Smart-Eye-Data-Datenbank-System der Augenklinik der LMU in den Jahren 2014 bis 2020 zusammen mit diagnostischen Daten aus Pentacam HR und Autorefraktometer ausgewertet. Als festes Therapieregime wurde eine Photoablation von 10 μm für epitheliale Basalmembrandystrophie und 6 μm für Patienten ohne Basalmembrandystrophie gewählt.

Ergebnisse

In beiden Kollektiven konnte eine Abnahme der Pachymetrie am Apex nachgewiesen werden (epitheliale Basalmembrandystrophie: Abnahme 25,8 μm, ±19,6 μm SD, Bandbreite −12–97 μm; keine Basalmembrandystrophie: Abnahme 12,3 μm, ±17,6 μm SD, Bandbreite −39–68 μm). Es kam zu keiner signifikanten Zu- oder Abnahme der „total corneal refractive power“ im epitheliale Basalmembrandystrophie-Kollektiv, im Kollektiv der rezidivierenden Erosiones ohne Basalmembrandystrophie zu einer signifikanten Zunahme von 42,3 dpt auf 42,6 dpt (Veränderung ±0,8 dpt SD, p < 0,05). Das sphärische Äquivalent zeigte keine Veränderung im Follow-up-Intervall für das epitheliale Basalmembrandystrophie Kollektiv. Hingegen zeigte das Kollektiv ohne Basalmembrandystrophie eine statistisch signifikante Abnahme des SE um 0,4 dpt (±0,7 dpt SD, p < 0,05). Das mittlere Follow-up-Intervall betrug 126 Tage (CI 95 %: 104 bis 147 Tage).

Schlussfolgerung

Ein signifikanter Einfluss auf die Refraktion konnte in der durchgeführten Studie in Bezug auf die „total corneal refractive power“ für beide Kollektive nur in geringem Maße festgestellt werden. Der finale Abtrag anhand der Pachymetrie am Apex hingegen kann auf das 2,3- bis 2,6-Fache der ursprünglichen Ablationstiefe geschätzt werden. Ursachen hierfür sind einerseits der Laserabtrag selbst sowie der Einfluss der reaktiven Wundheilung des kornealen Epithels.

Application of Intraoperative Optical Coherence Tomography Technology in Anterior Segment Surgery

The use of optical coherence tomography (OCT) technology in anterior segment diseases allows for precise assessment of the changes following anterior segment surgery. Advances in microscope-integrated OCT systems have allowed the utilization of intraoperative OCT (iOCT) in anterior segment surgeries, i.e., cornea, cataract, and refractive surgery. iOCT has enabled real-time precise visualization of anterior segment tissues as well as interactions between surgical instruments and ocular tissue; thus, the device can facilitate surgical procedures and provide valuable information for decision-making during anterior segment surgeries. In this review, the authors will introduce studies regarding the development of iOCT technology and its application in various anterior segment surgeries. Multiple studies have shown the efficacy of the iOCT for intraoperative assistance and guidance, suggesting the potential of the device for optimizing the surgical outcomes after cornea, cataract, and refractive surgery.

Clinical applications for intraoperative optical coherence tomography: a systematic review

In this systematic review, we provide an overview of the current state of intraoperative optical coherence tomography (iOCT). As iOCT technology is increasingly utilized, its current clinical applications and potential uses warrant attention. Here, we categorize the findings of various studies by their respective fields, including the use of iOCT in vitreoretinal surgery, corneal surgery, glaucoma surgery, cataract surgery, and pediatric ophthalmology. The trend observed in recent decades towards performing minimally invasive ophthalmic surgery has caused practitioners to recognize the limitations of using a conventional surgical microscope for intraoperative visualization. Thus, the superior visualization provided by iOCT can improve the safety of these surgical techniques and promote the development of new minimally invasive ophthalmic surgeries. Landmark prospective studies found that iOCT can significantly affect surgical decision making and can cause a subsequent change in surgical strategy, and the use of iOCT has potential to improve surgical outcome. Despite these advantages, however, iOCT is still a relatively new technique, and beginning users of iOCT can encounter limitations that can preclude their reaching the full potential of iOCT and in this respect several improvements are needed.

INTRAOPERATIVE OPTICAL COHERENCE TOMOGRAPHY -AVAILABLE TECHNOLOGIES AND POSSIBILITIES OF USE. A REVIEW

Optical coherence tomography (OCT) is a non-contact and non-invasive imaging and diagnostic method, that allows the imaging of ocular tissues on transverse sections in extremely high quality of micrometer resolution. The physical principle of OCT is analogous to ultrasound, but it uses infrared radiation instead of acoustic waves. By using a low coherent radiation source, it is possible to achieve a higher resolution. Based on the obtained data, the computer can reconstruct two or three-dimensional images of the examined tissue. In recent years, we have seen a rapid development in ophthalmic surgery, especially in surgical instruments and imaging methods. However, the technology of surgical microscopes does not change significantly and thus becomes a limiting factor in the development of ophthalmic microsurgery. The integration of the OCT into surgical microscopes, so the introduction of the Intraoperative Optical Coherence Tomography (iOCT), opens up further possibilities for displaying/looking at the operating field and adapting surgical techniques to the current situation during the surgery. On the contrary, the disadvantage is the prolongation of the surgery time and thus the theoretical increase in possible complications related to the surgery. iOCT can be used for operations on the anterior and posterior segment of the eye. In anterior segment surgery, it is used mostly in penetrating and lamellar keratoplasty, glaucoma surgery and cataract surgery. In posterior segment surgery, it is used during pars plana vitrectomy. The aim of the article is to provide a comprehensive overview of the current possibilities of using iOCT in eye surgery.

Laser-integrated Real-Time Optical Coherence Tomography (LI-OCT) in Anterior Segment Procedures

ABSTRACT

Intraoperative optical coherence tomography (OCT) was so far only available as microscope-integrated or hand-held device. Recently, this technology has been integrated into a femtosecond laser (FS). This pilot-study analyzes the potential of intraoperative imaging using OCT during FS-assisted procedures of the anterior eye segment. Therefore, intraoperatively acquired videos using FS-integrated intraoperative OCT (LI-OCT) in 14 patients (Victus, Bausch and Lomb, Rochester, USA) where analyzed in different surgical. The results show, that all surgical steps could be successfully visualized by LI-OCT. LI-OCT added important information regarding the depth and location of the incisions and dissection planes. Moreover, dynamic processes could be observed in real-time. LI-OCT represents a novel imaging technology that makes it possible to visualize intraoperative steps during FS-assisted surgery. In the future, automatic image analysis based on artificial intelligence could be helpful to detect complications at an early stage and to automatically stop the laser process in relevant constellations.

Laser refractive surgery in corneal dystrophies

Twenty-eight case reports and case series published between 2000 and 2019 concerning laser refractive surgery in patients with corneal dystrophies, resulting in 173 eyes from 94 patients, were included in this systematic review. Best results were achieved in posterior corneal polymorphous and Cogan dystrophy. Unfavorable results were found in Avellino dystrophy and Fuchs endothelial corneal dystrophy (FECD). Photorefractive keratectomy was not indicated in Meesmann and Avellino dystrophy. Laser in situ keratomileusis was indicated in posterior polymorphous corneal dystrophy but not in FECD, Avellino, or Cogan dystrophy. Small-incision lenticule extraction and other dystrophies such as lattice, fleck, Lisch, or François did not achieve enough scientific evidence to report any recommendation.

Fourier-domain optical coherence tomography-guided phototherapeutic keratectomy for the treatment of anterior corneal scarring

AIM

To evaluate the safety, visual and anatomic outcomes of fourier-domain optical coherence tomography (FD-OCT)-guided excimer laser phototherapeutic keratectomy (PTK) combined with photorefractive keratectomy (PRK) surgery in treating anterior corneal scarring.

METHODS

Clinical data of 23 eyes of 21 patients with anterior corneal scarring underwent FD-OCT-guided PTK and PRK from Dec. 2014 to Jul. 2016 were reviewed. Patients were assessed for preoperative and postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), contrast sensitivity (CS), FD-OCT, corneal topography and colour figures of anterior segments.

RESULTS

The preoperative corneal pathologic conditions included viral keratitis (7 patients, 7 eyes), band keratopathy (2 patients, 4 eyes), corneal dystrophy (4 patients, 4 eyes), traumatic corneal disease (2 patients, 2 eyes) and corneal chemical injury (6 patients, 6 eyes). Mean follow-up time was 10.65 (range, 3-19)mo. UCVA (in logMAR) improved from a mean of 0.79 (95%CI, 0.28-1.29) preoperatively to a mean of 0.45 (95%CI, 0.29-0.62) postoperatively (P=0.021). BSCVA (in logMAR) improved from 0.57 (95%CI, 0.27-0.88) preoperatively to a mean of 0.28 (95%CI, 0.15-0.41) postoperatively (P=0.001). Corneal topographic indices postoperatively showed significant improvement in corneal cylinder (P=0.009), the surface regularity index (P=0.007) and surface asymmetry index (P=0.00). Postoperative spherical equivalent averaged -0.53 diopters (-1.49 to 0.42). No complications were associated with the treatment.

CONCLUSION

FD-OCT-guided PTK combined with PRK is safe and effective for the treatment of anterior corneal scarring by eliminating or reducing corneal opacities.

Intraoperative Optical Coherence Tomography Guided Ocular Surgeries: Critical Analysis of Clinical Role and Future Perspectives

Intraoperative imaging of ocular tissues for diagnostic and therapeutic applications has gained immense admiration in recent years. The real time cross-sectional imaging, as well as three and four dimensional reconstruction abilities of intraoperative optical coherence tomography (iOCT), has enhanced our knowledge on many fronts in surgical maneuvers. In this review, we discuss the iOCT discovered constructive knowledge in the cornea, cataract, refractive, glaucoma, pediatric ocular, and various retinal conditions. The practical utility with decision modifying aspects along the specified ocular tissues and with respect to specific ocular entities have been narrated. Moreover, limitations and future directions have also been emphasized to make ophthalmic care more comprehensive in the future.

What Is the Impact of Intraoperative Microscope-Integrated OCT in Ophthalmic Surgery? Relevant Applications and Outcomes. A Systematic Review

Background: Optical coherence tomography (OCT) has recently been introduced in the operating theatre. The aim of this review is to present the actual role of microscope-integrated optical coherence tomography (MI-OCT) in ophthalmology. Method: A total of 314 studies were identified, following a literature search adhering to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. After full-text evaluation, 81 studies discussing MI-OCT applications in ophthalmology were included. Results: At present, three microscope-integrated optical coherence tomography systems are commercially available. MI-OCT can help anterior and posterior segment surgeons in the decision-making process, providing direct visualization of anatomic planes before and after surgical manoeuvres, assisting in complex cases, and detecting or confirming intraoperative complications. Applications range from corneal transplant to macular surgery, including cataract surgery, glaucoma surgery, paediatric examination, proliferative diabetic retinopathy surgery, and retinal detachment surgery. Conclusion: The use of MI-OCT in ophthalmic surgery is becoming increasingly prevalent and has been applied in almost all procedures. However, there are still limitations to be overcome and the technology involved remains difficult to access and use.

[Corneal dystrophies in optical coherence tomography]

BACKGROUND

Corneal optical coherence tomography (anterior segment OCT, AS-OCT) is described in the current IC3D classification of corneal dystrophies to be a method for improvement of clinical diagnostics and treatment.

OBJECTIVE

In this case series AS-OCT images of corneal dystrophies were analyzed with respect to morphological changes.

MATERIAL AND METHODS

This was a retrospective imaging and morphological case series with 38 eyes. For image acquisition the corneal module of the high-resolution spectral-domain OCT Zeiss Cirrus HD-5000 platform (Oberkochen, Germany) was employed. The following corneal dystrophies were analyzed: epithelial basement membrane dystrophy, Meesmann corneal dystrophy, Reis-Bücklers corneal dystrophy, granular corneal dystrophy type 1, granular corneal dystrophy type 2 and macular corneal dystrophy.

RESULTS

The AS-OCT images showed the typical changes of the dystrophies through hyperreflectivity and hyporeflectivity in the individual corneal layers. The findings in the AS-OCT images correlated well with the histological descriptions in the literature and provided additional information to the slit lamp examination, especially with respect to the exact location of the alterations.

CONCLUSION

Corneal AS-OCT imaging seems to be a helpful tool for determination of morphological changes in patients with corneal dystrophies and can facilitate both the diagnostics and surgical treatment decisions.

[Unmet research and developmental needs in ophthalmology : A consensus-based road map of the European Vision Institute for 2019-2025]

PURPOSE

To define unmet needs in ophthalmology which can realistically be addressed in the next years (2019-2025) and to describe potential avenues for research to address these challenges.

METHODS

Outcomes of a consensus process within the European Vision Institute (EVI, Brussels) are outlined. Disease areas which are discussed comprise glaucoma, retinal dystrophies, diabetic retinopathy, dry eye disease, corneal diseases, cataract and refractive surgery.

RESULTS

Unmet needs in the mentioned disease areas are discussed and realistically achievable research projects outlined.

CONCLUSION

Considerable progress can be made in the field of ophthalmology and patient-relevant outcomes in the near future.

Unmet Needs in Ophthalmology: A European Vision Institute-Consensus Roadmap 2019-2025

PURPOSE

To define unmet needs in ophthalmology that can realistically be addressed in the next 5 years (2019-2025) and describe potential avenues for research to address these challenges.

METHODS

Outcomes of a consensus process within the European Vision institute (Brussels) are outlined. Disease areas that are discussed comprise glaucoma, retinal dystrophies, diabetic retinopathy, dry eye disease, corneal diseases, cataract and refractive surgery.

RESULTS

Unmet needs in the mentioned disease areas are discussed and realistically achievable research projects outlined.

CONCLUSIONS

Considerable progress can be made in the ophthalmic field and patient-relevant outcomes in the near future.