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Keywords:

  • cats;
  • cornea;
  • dogs;
  • keratitis;
  • optical coherence tomography;
  • spectral domain

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Purpose

Morphologic evaluation of the cornea is based on the slit-lamp examination. In human ophthalmology, optical coherence tomography (OCT) has opened a new field in the clinical approach to anterior segment disorders and more specifically the cornea. The aim of our study is to describe spectral domain OCT examination of the cornea in dogs and cats in clinical practice conditions.

Material and methods

One hundred eyes were examined from 52 dogs and 41 cats presented to a private practice referral center with an Optovue iVue SD-OCT device. Sixteen healthy animals were used as control group, and the others were examined for various corneal conditions. All animals were examined after sedation or anesthesia.

Results

Normal and pathological aspects of canine and feline cornea were described for various conditions such as corneal ulcers, microbial keratitis, corneal sequestrum, infiltrations, foreign bodies, corneal dystrophies, and surgical conditions.

Conclusion

SD-OCT examination of normal and pathological corneal conditions in dogs and cats gave an accurate evaluation of each component of the cornea. The advantage of the technique is the in vivo, real-time evaluation of all corneal layers with the absence of corneal contact. Constraints included the necessity of sedation for precise focus and the low quality of images obtained with too pigmented or thickened corneas.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Several imaging methods exist for the evaluation of corneal morphology. The most frequently used method is slit-lamp biomicroscopy, but visualization of deeper corneal structures can be limited by light absorption and scattering through the cornea, particularly in case of corneal edema. The application of new technologies including high-frequency ultrasound (ultrasound biomicroscopy [UBM]), confocal microscopy, Scheimpflug imaging, and optical coherence tomography (OCT) has led to improved resolution and complementary evaluation of corneal conditions.[1-3] OCT, developed in 1990, was initially dedicated to evaluation of the retina in human ophthalmology.[4] The use of OCT for the examination of the anterior segment of the eye, a practice started in the early 2000s, has opened a new field in the clinical and experimental approaches to evaluating these structures.[1-3] Anterior segment spectral domain OCT (SD-OCT) has been the subject of more than 500 scientific articles over the last 5 years. The application of SD-OCT for medical and surgical purposes has been specifically described for the structural analysis of tear meniscus, normal and pathological cornea, and iridocorneal angle, as well as evaluation of the anterior chamber, iris, and lens.[5-16] OCT has also been compared with slit-lamp examination and with Scheimpflug imaging for corneal endothelial evaluation.[17]

Spectral domain optical coherence tomography function is similar to ultrasonography with a few major differences. Ultrasonography uses ultrasound waves emitted by a probe in contact with the tissue to be studied, whereas SD-OCT uses infrared (IR) light emitted at a distance from the cornea, making contactless image acquisition possible.[1] While optical transparency is not required for ultrasound, the use of IR light in OCT requires transparent media. The light passing through different ocular media experiences interference, which is compared with light reflected on a reference mirror at the same working distance. Scanning the reference mirror through a range of distances allows generation of an axial image (A-scan). A series of axial sections are combined to produce a composite image, similar to the standard two-dimension (B-scan) image produced in ultrasonography. SD-OCT images have an axial resolution of 2–4 μm and a lateral resolution of 20–25 μm. As a comparison, the axial resolution of 50-MHz ultrasonography is 50 μm.[12] Additional information about technical features of SD-OCT can be found elsewhere.[1, 4]

Heavy and costly SD-OCT devices were initially limited to specialized human ophthalmology centers or research centers. But now, lighter and more affordable models have become available. The use of SD-OCT for the morphological analysis of the cornea of dogs and cats in healthy and pathological conditions has yet to be described. Our study aims to evaluate spectral domain OCT for corneal imaging in dogs and cats in clinical practice conditions.

Material and Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Animals

One hundred eyes were examined in 93 animals. The group studied included 52 dogs and 41 cats examined between July and November 2011 at the Acacias Veterinary Clinic Ophthalmology department. The healthy animal control group included eight dogs and eight cats. Control animals did not have any ocular lesions and were anesthetized for minor operations with no ocular involvement. The remaining animals (44 dogs and 33 cats) were anesthetized prior to an examination or ocular surgery for the following conditions: chronic superficial corneal ulcers (13 cases), deep corneal ulcers (10 cases), anterior uveitis (three cases), bacterial keratitis (10 cases), corneal wound (14 cases), conjunctival grafts (eight cases), corneal sequestra (five cases), corneal foreign body (three cases), corneal dystrophy (three cases), chronic superficial keratitis (three cases), Florida keratopathy (two cases), stromal hemorrhage (one case), glaucoma with marked corneal edema (two cases), and bullous keratopathy (one case). All animals were examined after consent was obtained from their owner. All procedures were performed in accordance with the French guidelines for animal care.

Anesthesia

All animals examined were sedated or under general anesthesia. Cats were anesthetized with 0.01 mg/kg medetomidine (Domitor®, Pfizer, NY, USA) and 5 mg/kg ketamine (Imalgene 1000®, Merial, Lyon, France) via intramuscular administration. Dogs were anesthetized with 300 μg/m² medetomidine and 5 mg/kg ketamine delivered intravenously followed by 0.5–2% isoflurane (Isoflurane Belamont®, Nicholas Piramal Ltd, London, UK) in oxygen after endotracheal intubation.

Ophthalmologic examination

All animals were submitted to a thorough ophthalmologic examination including slit-lamp examination, Schirmer test, and tonometry. In cases where bacterial infection was suspected, samples were submitted for a bacteriologic analysis in a local laboratory dedicated to veterinary bacteriology (Laboratoire Meynaud, Toulouse, France).

Imaging

Imaging was performed using an iVue SD-OCT system (Optovue EBC Medical, Paris, France) connected to a computer interface and a laptop (Fig. 1). The system functions at 840 nm, which is in the IR radiation range, and can perform 26 000 A-scans per second. The imaging unit has a working distance of 13 mm and can be positioned to capture A-scans horizontally on a table or vertically, held in place by an adjustable support for use in the operating room. For this study, the image capture unit was positioned vertically (Fig. 1a).

image

Figure 1. The OCT device (a) and the animal in examination position (b).

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The iVue device is designed to examine the retina and the anterior segment. There are two operating modes for imaging the anterior segment, both of which require installation of an additional corneal-anterior module (or CAM) at the end of the image capture unit. The ‘pachymetry’ mode images eight, 6-mm wide radial sections of the cornea, with the focus line positioned in the center of the cornea. The ‘angle’ mode images a section along a line chosen to correspond with the area or interest.

Animals were placed in dorsal recumbency, with the head supported by a vacuum cushion (Fig. 1b). The image capture unit, supported by an articulated arm, was brought close to the eye and then focused using an adjustment knob. Care was taken to humidify the corneal surface with artificial tears during imaging to avoid desiccation artifact. Images were captured using a foot control and converted to two-dimensional B-scans on which it was possible to draw, write, and measure with calipers. Image analysis was performed in the same manner as ultrasound image analysis and covered three aspects: structure identification, description of lesions by analysis of light interference areas (increased or reduced reflection), and measurements. The same operator (Frank Famose) performed image examination and processing.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Normal cornea

Examination in ‘pachymetry’ mode reveals the different layers in the cornea (Fig. 2a,b). The cornea appears as a composite of three layers of varying reflectivity and thickness. The epithelial layer appears homogeneous with a relatively low reflectivity compared with the pre-corneal tear film and anterior stroma. The stromal layer is thicker and appears heterogeneous with an intermediate reflectivity. In the deepest layer, Descemet's membrane and the endothelium combine as a thin, dense line.

image

Figure 2. Normal cornea of dog (a) and cat (b) in pachymetric mode. The values in green represent the total thickness of the cornea and that of the epithelium.

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The average corneal thickness was 535 μm in dogs (interval of values 500–620 μm) and 600 μm in cats (interval of values 540–660 μm). In cats, the heterogeneously organized anterior stroma was distinguishable from the posterior stroma where the homogeneous organization of collagen lamellae was visible (Fig. 2b).

In the healthy animals, the average measured epithelial thickness was 55 μm in dogs (interval of values 50–60 μm) and 60 μm in cats (interval of values 55–65 μm). The average measured stromal thickness was 480 μm in dogs (450–560 μm) and 540 μm in cats (485–595 μm). The number of healthy animals imaged was not sufficient to perform a statistical analysis on these parameters, and the endothelio-Descemet layer was not thick enough to be measured in healthy animals.

Although care was taken to humidify the corneal surface during examination, artifact lesions due to superficial corneal desiccation were observed and appeared as a notch in the corneal thickness, with a reduction in epithelial thickness (Fig. 3a,b).

image

Figure 3. Corneal modification due to desiccation. The red arrow represents the section area on the macroscopic view (a). OCT (b) revealed reduced epithelial thickness (white arrows).

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Epithelial and subepithelial disorders

Thirteen chronic epithelial ulcers were examined. The main features observed in both species were an increase in the thickness and reflectivity of the epithelial layer, accompanied by epithelial detachment and a clearly visible increase in anterior stromal reflectivity (Fig. 4a2). Epithelial thickness at the margins of the ulcer ranged from 80 to 150 μm.

image

Figure 4. Epithelial and subepithelial conditions. The red arrow represents the section area. (a1,a2) Chronic epithelial erosion in a dog. Hyperplastic epithelium is shown by green arrows. Yellow arrows show epithelial detachment. Stromal increased density is shown by the white arrows. (b1,b2) Superficial corneal melanosis. The presence of melanocytes is shown by increased superficial reflectivity (yellow arrows). Stromal image is homogeneously attenuated. (c1,c2) Presumed lipid and/or calcic degeneration. Presumed lipid and/or calcic deposits are identified by high reflectivity in the anterior stroma (green arrows). Posterior stroma is unchanged. Epithelium thickness is heterogeneous. Melanosis (yellow arrows) and a corneal blood vessel (red arrow) are visible.

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Three cases of canine chronic superficial keratitis with corneal melanosis were examined. In all cases, we observed a sharp increase in the reflectivity of the epithelial layer, with a homogeneous attenuation of the stromal image (Fig. 4b1,b2). This increased anterior reflectivity is due to the presence of melanocytes, including melanic pigments, which absorb light in the IR range.

In the two cases of presumed lipid and/or calcium corneal degeneration, we observed increased anterior stromal reflectivity with no modification of the posterior stroma. Variations of the epithelial thickness were observed and were associated with the density of the presumed lipid and/or calcium deposits (Fig. 4c1,c2). Total corneal thickness was 380 and 530 μm, respectively, presumed lipid and/or calcic deposit depth ranged from 80 to 250 μm. Melanosis, and corneal blood vessels were clinically present and visible on OCT scans.

Stromal disorders

Ten cases of suspected bacterial keratitis were evaluated. Positive cultures confirmed the diagnosis in eight of the ten cases. SD-OCT analysis revealed a reduction in stromal thickness localized to the anterior stroma (Fig. 5). The center of the lesion appeared either as a homogeneous loss of stroma or as a heterogeneous association of high- and low-reflectivity zones. High-reflectivity zones corresponding to cellular infiltration surrounded these lesions. The epithelial layer was partially absent, and in some cases of deep stromal destruction, Descemet's membrane was pushed forward by intraocular pressure. Residual stromal thickness was measurable.

image

Figure 5. Infectious keratitis and deep ulcers. The red arrow represents the section area. (a1,a2) infection with loss of surface substance (grey arrows) in a homogeneous stroma. (b1,b2) deep keratitis with an area of collagenolysis (yellow arrows) and increased peripheral stromal reflectivity. (c1,c2) deep corneal ulceration. Area of stromal densification (white arrows) and debris (pink arrow) are visible. Residual stromal thickness can be measured. (d1,d2) deep keratitis with loss of stromal continuity and central elevation of deep stroma (green arrows). (e1,e2) Predescemetic lesion. The residual corneal thickness is 50 μm.

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Spectral domain optical coherence tomography evaluation of deep corneal ulcers revealed a homogeneous increase in stromal reflectivity surrounding the ulcerated area and the presence of debris at the bottom of the ulcer. Analysis allowed measurement of the ulcer depth, information that is critical to choosing the appropriate surgical treatment.

The three corneal foreign bodies (Fig. 6) were characterized by the presence of a posterior cone-shaped shadow related to their opacity. Depending on the penetration depth, an endothelial reaction was visible. Localization of the end of the foreign body was challenging, and serial scans were required to identify perforations.

image

Figure 6. Corneal foreign body. The red arrow represents the section area. Corneal foreign body (FB) appears with a strong IR absorption with posterior cone-shaped shadow (***). Endothelial reaction (yellow arrows) is visible. Serial scans (a1–c2) show total corneal perforation.

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We also examined two cases of Florida keratopathy (Fig. 7a1,a2). In SD-OCT images, these lesions were characterized by a clear increase in superficial and deep stroma reflectivity. This increased reflectivity was deeper than that observed in the case of stromal hemorrhage (Fig. 7b1,b2). The lesions were not accompanied by epithelial alteration, an increase in stromal thickness, or increased IR light reflexion behind the lesions.

image

Figure 7. Diffuse stromal lesions. The red arrow represents the section area. (a1,a2) Florida spots with stromal cellular infiltration (white arrows). (b1,b2) stromal hemorrage (green arrows).

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Spectral domain optical coherence tomography imaging of feline corneal sequestrum was challenging. In the five cases examined, sequestrum appeared as an intense, localized light reflection in the anterior stroma. IR light reflection varied according to the density and thickness of the sequestrum. In two cases, the posterior stroma remained visible (Fig. 8a1,a2), making it possible to measure the thickness of the necrotic area before making a decision concerning an operation. In the three remaining cases, this pre-operative evaluation was not possible due to high lesion reflectivity (Fig. 8b1,b2).

image

Figure 8. Feline corneal sequestrum. The red arrow represents the section area. (a1,a2) corneal sequestrum (grey arrow) with deterioration of stromal signal. (b1,b2) corneal sequestrum with total signal absorption (yellow arrows).

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Three cases of major increase of the stromal thickness were observed. In two cases of glaucoma with an intense corneal edema, corneal structure was maintained, but the spacing of collagen lamellae was altered (Fig. 9a1,a2). In the other case, a feline bullous keratopathy, the normal stromal architecture was severely disrupted, and pockets of liquid among highly modified stromal structures were observed (Fig. 9b1,b2). Corneal thickness could not be measured in either case due to the size of the cornea, which was not entirely visible on the screen.

image

Figure 9. Major stromal alterations. (a1,a2) intense corneal edema due to glaucoma in a cat. Collagen lamellae are separated by aqueous hyporeflective material. (b1,b2) Feline Bullous keratopathy. Stromal structure is replaced by ‘pockets’ of fluid.

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Endothelial disorders

In a case of persistent pupillary membrane with localized endothelial dystrophy (Fig. 10a1,a2), a localized endothelial hyper-reflectivity was observed supported by a suspended structure in the anterior chamber. Filaments were difficult to highlight in two-dimensional scans, and serial scans were required to monitor the filament trajectory.

image

Figure 10. Endothelial alterations. (a1,a2) persistent pupillary membrane with endothelial attachment (grey arrows). (b1,b2) retrokeratic precipitates (green arrows) with heterogeneity of anterior chamber. (c1,c2) anterior synechia (green arrows).

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In the three cases of anterior uveitis, precipitates behind the cornea appeared in SD-OCT imaging as highly reflective wide-based lesions on the endothelium (Fig. 10b1,b2). A diffuse inhomogeneous granular reflectivity of the anterior chamber was observed. Anterior synechia appeared as dense lesions attached to the endothelium in continuity with the anterior face of the iris (Fig. 10c1,c2).

Surgical disorders

Corneal structure was evaluated after conjunctival grafts in eight animals using SD-OCT (Fig. 11a1,a2). The images obtained showed a conjunctival structure covered with an epithelium and embedded in the stroma. The conjunctival structure was recognizable due to higher density and the presence of blood vessels.

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Figure 11. Surgical disorders. The red arrow represents the section area. (a1,a2) conjunctival graft in a dog. The conjunctiva (green arrows) is denser than the cornea and has blood vessels (yellow arrows). (b1,b2) traumatic cornea wound. Blood clot is present near the edge of the wound. (c1,c2) Surgical corneal wound in a cat. Wound edge coaptation is shown by white arrows.

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In the 14 cases of corneal wounds, the images obtained did not identify the precise area of perforation. However, images did show the presence of fibrin and blood in the anterior chamber (Fig. 11b1,b2). Evaluation of corneal incisions (Fig. 11c1,c2) to check the wound edge junction was possible, although assessment of deep sections of the stroma was difficult because of the IR absorption related to the corneal edema.

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

The goal of this study was to test the feasibility of using SD-OCT to image the cornea in cats and dogs in common practice situations. Our results confirm that this technique is applicable to the evaluation of the cornea in healthy and pathological conditions. For most cases studied, SD-OCT evaluation provides reliable and accurate additional information to the standard examination using a slit lamp for corneal disorders. Through the study of many different conditions, we were able to underline diagnosis- and image-related advantages and limitations of SD-OCT.

This study is one of the first evaluations of SD-OCT for corneal diseases in private practice conditions. This means, we have evaluated the pathological conditions that came through our clinic during the time of the study. Although a wide range of conditions has been examined, many other conditions such as extended endothelial dystrophies or eosinophilic keratitis were not evaluated because we were not presented with those conditions during the study.

The SD-OCT imaging resolution was excellent at all depths, and we were able to measure the central cornea thickness with a resolution of 5 μm. This measurement required the device to be positioned axially in the center of the cornea. The results obtained in the ‘pachymetry’ mode were compatible with available data.[18, 19] However, statistical analysis of these data was not the aim of this study and has not been performed. The influence of the corneal curvature on the pachymetry value is known in humans,[20] but has not been measured in this study. As is the case with humans, the central trajectory of IR illumination was accompanied by a central reflection that could disturb tissue analysis. This reflection was not systematic and was related to the perpendicular position of the incident light in relation to the corneal surface.[7]

In all pathological cases studied, qualitative and quantitative analyses of the lesions were possible using SD-OCT. In the case of chronic superficial corneal ulceration, we were able to detect both epithelial detachment and hyperplasia, as well as the increased reflectivity of the anterior stroma. The analysis of bacterial keratitis highlighted the presence and the intensity of cellular infiltration, corneal edema, and tissue destruction. Measurements made on the different compartments of the cornea allowed us to monitor the development of these lesions over time. Our observations were similar to those performed in human ophthalmology for which SD-OCT is now a useful additional technique in the evaluation of bacterial keratitis.[21, 22] However, in some cases, the hyper-reflectivity of lesions limited the assessment of deep corneal areas, and as a result, evaluation of the entire stroma was not always possible.

Images of corneal dystrophy and degeneration were correlated with available histologic data by identifying areas of high reflectivity in the anterior stroma.[23] We were able to measure the thickness of these high-density regions in vivo using SD-OCT. These observations were similar to human data produced from analysis of presumed calcified lesions.[24, 25] Precise localization in the subepithelial stroma, specific reflectivity, and evaluation of the deposits thickness provided a noninvasive confirmation of clinical diagnosis. The deepest stromal lesions, Florida spots, were also characterized by the presence of an infiltrating component without any epithelial modification. SD-OCT imaging of major stromal changes such as complete corneal edema and bullous keratopathy produced spectacular pictures showing profound changes in the stromal architecture that could not be evaluated by slit-lamp examination. What we call feline bullous keratopathy is named, in human ophthalmology, corneal hydrops, a condition associated with endothelial rupture or detachment.[26] SD-OCT examination failed to show endothelial structures in bullous keratopathy because it was not technically possible to have the entire corneal thickness on the same scan, so results could, therefore, not be compared with human data.[27] Similarly, when imaging endothelial lesions, the SD-OCT examination provided an accurate evaluation as long as the corneal thickness was <1300 μm, and thus, absorption was minimal. This limitation can be further investigated by imaging endothelial dystrophies and degenerations, which were not included in our study. This limitation could also be handled by the use of UBM that uses high-frequency ultrasound, which does not depend on corneal transparency. UBM can scan extremely thick corneas but with a lower resolution than OCT.[6]

We also used SD-OCT for evaluation and follow-up of surgical procedures. The preoperative analysis of corneal sequestra in cats was not reliable. Our aim was to anticipate the choice of the surgical technique and of the prognosis by preoperative evaluation. In two cases, the size and position of the lesion were accurately measured, while in other cases, the reflectivity of the pigmented lesion produced a posterior shadow that made analysis of the deep stroma impossible. However, this lack of information about the depth of the sequestrum did not change either the treatment choice or the outcome of the surgical procedure. OCT was used after the keratectomy to measure the corneal thickness and to detect residual hyper-reflective areas. The shadow effect was also observed in the evaluation of corneal foreign bodies. Serial scans were required to overcome this difficulty and accurately quantify the depth of penetration.

Preoperative and post-operative evaluation during superficial keratectomies and conjunctival or biomaterial (such as porcine intestine submucosa) grafts was possible with SD-OCT. The thin graft material was transparent enough to allow unobstructed imaging of underlying structures and the measurement of their dimensions. These observations were similar to those made in humans where OCT is used frequently in the operative scope of corneal surgery to aid in choice of treatment strategy.[2, 5, 7, 11, 25, 28] Currently, more data are needed to support this kind of protocol, but we believe that increasingly widespread use of OCT will improve treatment strategies in the future. For example, the ability to accurately evaluate corneal thickness before or during the surgical procedure will allow the veterinary surgeon to use novel surgical tools like lasers or corneal cross-linking, which should only be used when minimal residual corneal thickness can be guaranteed.

The analysis of corneal wounds proved more difficult. Perforation areas were not always visible in SD-OCT because they required the beam to be oriented accurately along the axis of the wound. In addition, the IR absorption due to corneal edema limited the imaging of deep structures in most of the cases. In these conditions, the use of SD-OCT adds little to no value to the slit-lamp examination.

The SD-OCT images of healthy corneas in carnivores were comparable to images of the human cornea, where different layers are easily distinguishable.[6] These results correlate strongly with a previous study performed on a smaller group.[29] However, the SD-OCT image of Descemet's membrane and the endothelium fades as the thickness of the cornea increases.

The use of SD-OCT for corneal evaluation in normal and pathological conditions in dogs and cats opens an investigative field that is comparable to the existing field in human ophthalmology. In our study, the advantages of this technique were found in the ability of giving a qualitative and quantitative evaluation of all cornea layers, in vivo, in real time. The rapid acquisition time and the absence of contact with the ocular surface make the method insensitive to eye movements and compatible with the fragility of the cornea to be examined. Furthermore, the production of quantitative images and measurements allows us to monitor clinical situations in an objective manner, particularly in the context of microbial keratitis.

However, we encountered three types of difficulties in the application of SD-OCT to corneal evaluation. First, focusing must be very precise, and it was very difficult to use the device on conscious animals. This fact led us to use SD-OCT on sedated animals only, which added the necessity of permission, from the owners, for repeated sedations for follow-up imaging sessions. Additionally, due to the fine focus requirements, small lesions were not easily detected during the examination, as was the case for the corneal wounds and foreign bodies. Serial scans were required to obtain useable evaluation images in such cases. Finally, for certain disorders, opacity of corneal structures obscures image acquisition and interpretation, and thus, accurate analysis of corneal sequestra was difficult using SD-OCT. In these cases, SD-OCT presented the same limitations as slit-lamp examination. For highly edematous lesions, examination was limited by corneal thickness for which it was not possible, with our device, to scan the entire cornea. The use of UBM, which does not depend on corneal transparency but has a lower resolution than OCT, could help to evaluate such corneal conditions.

We were driven to complete this study because of the possibility of obtaining equipment that is compatible with veterinary practice. Here, we demonstrate the successful use of the SD-OCT technique for the imaging and evaluation of canine and feline cornea in clinical conditions for a wide range of corneal diseases. This technique is not intended to replace careful slit-lamp examination. The results and images presented here show that SD-OCT optical analysis has a resolution comparable to low-magnification histologic images, and the images obtained are in agreement with available clinical and histologic data in the literature. In most of the cases, images provided us with quantitative information that completed the slit-lamp examination. The major advantage of this technique is real-time, in vivo, contactless evaluation of animal corneal structures, and SD-OCT corneal evaluation in pathological and surgical conditions is very promising diagnostic tool for therapeutic decision-making and for follow-up of corneal healing.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Material and Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
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