EXPERIENCE OF USING OPTICAL COHERENCE TOMOGRAPHY IN CORNEAL INJURIES

two groups

Background.Eye trauma is one of the most common causes of monocular visual impairment and blindness worldwide.Each year, 55 million people suffer eye injuries that result in temporary or permanent disability [1,2].Modern classification divides eye trauma into two groups: open (penetrating) and closed (non-penetrating) trauma.This classification was introduced and approved in 1996 in accordance with the recommendations of the United States Registry of Trauma and the terminology of Birmingham Eye Trauma of the International Society of Eye Trauma, under the leadership of Professor Kuhn.Non-penetrating eye trauma includes contusion and erosion, while open globe eye trauma encompasses penetrating, perforating, with a foreign intraocular body, or without one [3].During the diagnostic phase, it is crucial to conduct a thorough examination and establish the appropriate diagnosis based on the existing classification, as it significantly influences the subsequent patient management and treatment outcomes.In cases of traumatic eye injuries where erosion is superficial and does not involve the basal membrane, the corneal wound typically epithelializes within 48-72 hours, restoring its structure and transparency.However, in cases of deep corneal damage, pathological regeneration may occur, leading to the development of fibrosis, impaired transparency, and reduced visual acuity.
Typically, routine ophthalmological diagnostic methods are used for the diagnosis of traumatic eye injuries, including visual acuity assessment, biomicroscopy, and corneal fluorescein staining [5].Additional visualization methods employed in cases of eye trauma include X-ray imaging, computed tomography (CT), magnetic resonance imaging (MRI), ultrasonography, and optical coherence tomography (OCT).The first three methods are useful for determining the localization of foreign bodies in eye injuries, while the latter methods allow for the assessment of the structure of both the anterior and posterior segments of the eye.
Optical Coherence Tomography (OCT) allows for real-time, high-resolution imaging of eye tissues.OCT is a diagnostic method that was initially developed for visualizing the posterior segment of the eye in 1991 [6,7].With advancements in technology, OCT has shown great potential for imaging the anterior segment of the eye, including the conjunctiva, corneal layers, sclera, and anterior chamber angle.Current applications of anterior segment OCT enable measurements of corneal thickness, the diagnosis of keratoconus, and the assessment of the anterior chamber angle in glaucoma diagnosis [7].In our research, we present our experience in using OCT for traumatic corneal injuries as an additional method to assess the depth and extent of damage and to monitor the healing process of corneal erosions.
Aim: To utilize optical coherence tomography of the anterior segment of the eye for the diagnosis and assessment of corneal wound healing processes.Data collection included demographic information of the patients, their occupations, the mechanism and duration of the trauma, the presence of recurrences, and the timing of seeking medical assistance.All patients underwent assessments of visual acuity, biomicroscopy, and evaluation of the conjunctiva and corneal status, as well as a fluorescein test.Biomicroscopic examination was used to assess the condition of the conjunctiva and cornea, as well as to localize the epithelial defect in corneal wound healing.

This
Using AS-OCT, we observed the corneal thickness and the size of the epithelial defect both before and after treatment.Corneal images were obtained using spectral-domain OCT with a wavelength of 830 nm and a scanning speed of 130,000 A-scans per second, providing an axial resolution of 5 µm.It is important to note that during the examination, the area of injury was matched biomicroscopically before and after treatment, and images were captured in the same plane while maintaining the research protocol.

RESULTS AND DISCUSSION
The study included 28 males (60.9%) and females (39.1%), with ages ranging from 22 to years (mean age 41.5 ± 2.4).The average duration of symptoms before patients sought medical attention was 2.2 ± 1.2 days.In terms of the type of trauma, non-occupational trauma was more com- AS-OCT was performed for all patients on the day of their initial visit and after treatment.Image of the cornea in the control group is presented in Fig. 1 and corresponds to a normal cornea.In the image, distinct layers are clearly distinguishable, including the tear film, epithelium, basement membrane, Bowman's layer, stroma, and Descemet's-endothelial complex.The corneal epithelium is represented by a weakly reflective layer, above which we observe a hyper-reflective layer corresponding to the tear film.Between the epithelium and the stroma, a highly reflective line is visualized, morphologically corresponding to the basement membrane, while a hypo-reflective line corresponds to Bowman's layer.The results indicate that the basement membrane appears as a hyper-reflective line, which aligns with its histological struc-ture since it consists of various types of collagens (collagen types IV and VII) [7,8].
Identification of the basement membrane line serves as an important diagnostic criterion since its involvement in the pathological process affects the outcome of corneal trauma [9].The next layer of the cornea is the stroma, which has a homogeneous and uniform structure across its entire plane, thanks to the content and arrangement of type 1 collagen.The Descemet's-endothelial complex corresponds to a hyper-reflective line located just below the stroma.Comparing the histological structure of the cornea with the obtained OCT images of the cornea allows for an accurate diagnosis of the depth of corneal damage, which subse-Fig.3. AS-OCT of traumatic corneal erosion, clinical case 13.A 32-year-old patient, while working with metal, suffered an injury from a foreign metal body.Upon examination, visual acuity was 0.6 without correction.On OCT : 1) multiple irregularly shaped epithelial disruptions, 2) uneven basal membrane, with some areas thickened and others thinned, 3) heterogeneity in the reflective properties of the stroma Fig. 2. AS-OCT image of traumatic corneal erosion, clinical case №3.A 30-year-old female patient sustained an injury from a tree branch impact.Upon examination, her visual acuity was 0.2 uncorrected.In the OCT image: 1) There is an epithelial layer defect.
2) The surface of the anterior stroma appears heterogeneous and mixed.
3) The reflectivity of the underlying stroma is hypo-reflective and disorganized quently influences the treatment method and the consequences of the trauma [8,10].
During OCT examination of traumatic corneal erosion, in most cases, the following features were visualized: an irregularly shaped epithelial defect with uneven borders, an irregular mixed anterior surface of the stroma, heterogeneous reflectivity of the stroma, and corneal thinning.After treatment, the results corresponded to corneal re-epitheliali-zation: thick and intact epithelium, hyper-reflective stroma, and a demarcation line confirming the wound healing process.After treatment, the corneal thickness was restored to (529 ± 144 μm), which corresponds to the thickness of a healthy cornea.
Using OCT, traumatic corneal erosions with damage to the basal membrane (Fig. 3) were detected, which later clinically resulted in erosion EXPERIENCE OF USING OPTICAL COHERENCE TOMOGRAPHY IN CORNEAL INJURIES recurrence (one month after the initial visit).OCT in this case revealed multiple irregular epithelial disruptions and the absence of a uniform basal membrane line.
AS-OCT provides high-resolution, in vivo cross-sectional images of the cornea and anterior chamber of the eye, corresponding to the histological structure of the corneal tissue.It allows for the assessment of morphological and structural changes in various layers of the cornea in cases of trauma, inflammatory processes, and dystrophic changes, as well as after ophthalmic surgeries [9,10,11].
The use of OCT in traumatic corneal injuries is an important additional instrumental method of examination.With AS-OCT, we can assess the epithelialization of corneal layers, the depth and area of damage, and the involvement of the basal membrane in the pathological process, especially in cases of prolonged healing.In situations where the epithelium and basal membrane are restored, transparency and optical properties of the cornea are preserved [12].On the other hand, prolonged inflammation and the inability to restore the basal membrane initiate corneal fibrosis, leading to a disruption of its optical properties.With OCT, we can observe the morphological structure of the cornea and the wound healing process, which allows us to predict the consequences of trauma.

CONCLUSION
OCT is an informative additional diagnostic method for corneal injuries that allows for the evaluation of corneal morphology, including the status of the basal membrane, corneal thickness, and epithelialization.Based on these results, we can predict the course of corneal trauma and its possible consequences, enabling us to adjust treatment to prevent fibrosis development and minimize the consequences of the injury.

Fig. 1 .
Fig. 1. Anterior segment optical coherence tomography (OCT) image depicting a healthy cornea The study also adhered to the regulations of the Ministry of Health of Ukraine, including Orders No. 690 of September 23, 2009, No. 944 of December 14, 2009, No. 616 of August 3, 2012, as well as those approved by the Commission for Bioethical Expertise and Ethics in Scientific Research of Bogomolets National Medical University under Protocol No. 138 dated November 10, 2020.Informed consent was obtained from each patient for their participation in the study.

Table 1 Clinical characteristics of patients with corneal injuries
EXPERIENCE OF USING OPTICAL COHERENCE TOMOGRAPHY IN CORNEAL INJURIESmon, occurring in 26 cases (56.5%), while occupational trauma accounted for 20 cases (43.5%).Among patients with occupational trauma, 50% did not use protective eyewear during work.The control group consisted of 15 healthy individuals with an average age of 32.5 ± 2.4.The clinical characteristics of the patients, including visual acuity, localization of the injury, and corneal thickness, are presented in Table1.