In vivo ocular imaging of the cornea of the normal female laboratory beagle using confocal microscopy

A review of diagnostic tests for qualitative and quantitative tear film deficiency in dogs

Dry eye disease (DED) is a complex multifactorial condition caused by loss of ocular surface homeostasis from quantitative and/or qualitative tear film deficiency. Schirmer tear test (STT) is often the only diagnostic test used to assess for DED in veterinary practice. STT is invaluable in the diagnosis and monitoring of quantitative tear film deficiency (i.e., keratoconjunctivitis sicca); however, it is not sufficient to optimize therapy and fully recognize other contributing factors for the disturbance in ocular surface homeostasis. The present work reviews diagnostic tests for assessing aqueous tear production in veterinary medicine, as well as the quality of tears, corneal epithelial barrier integrity, and the lacrimal functional unit.

A multicenter retrospective evaluation of the prevalence of known and presumed hereditary eye diseases in Lagotto Romagnolo dog breed within a referral population in Italy (2012-2020)

OBJECTIVE

To describe the ophthalmological findings of Lagotto Romagnolo dog breed and to report the prevalence of Known and Presumed Hereditary Eye Diseases (KP-HED).

ANIMALS STUDIED

Two hundred sixteen dogs were examined and included in this retrospective study.

PROCEDURES

Medical records of Lagotto Romagnolo dogs between 2012 and 2020 were included. Data about the ocular status were collected through ocular screening examinations (OSE) or clinical ophthalmic examinations (COE). The prevalence of each KP-HED was expressed as a function of the total number of the KP-HED in this referral population.

RESULTS

A total of 85 dogs (39.35%) were ophthalmologically healthy, ocular diseases presumably not hereditary were found in 43 dogs (19.91%), and 88 dogs (40.74%) were affected by one KP-HED. The most common KP-HEDs diagnosed were cataract (28/88; 31.82%), corneal endothelial dystrophy (17/88; 19.32%), retinal dysplasia (9/88; 10.23%), lens instability (7/88; 7.95%), progressive retinal atrophy (6/88, 6.82%), and keratoconjunctivitis sicca (6/88, 6.82%). Most of dogs with a KP-HED (77.27%, 68/88) were identified within COE group.

CONCLUSIONS

To the authors' knowledge, this is the first report of the prevalence of ocular disease in the Lagotto Romagnolo dog breed within a referral population in Italy. This study suggests a relatively high prevalence of KP-HED, with a characteristic late-onset presentation in some diseases. Many of these KP-HED's, lead to ocular pain and irreversible blindness, for this reason, the authors highlight the importance of aiming for an early diagnosis. Breeder's efforts and breeding programs should be directed at limiting such disorders.

The Clinical Guiding Role of the Distribution of Corneal Nerves in the Selection of Incision for Penetrating Corneal Surgery in Canines

The cornea is one of the regions with the highest density of nerve terminals in the animal body and it bears such functions as nourishing the cornea and maintaining corneal sensation. In veterinary clinical practice, the corneoscleral limbus incision is frequently applied in cataract surgery, peripheral iridectomy, and other procedures for glaucoma. Inevitably, it would cause damage to the nerve roots that enter the cornea from the corneal limbus, thus inducing a series of complications. In this paper, the in vitro cornea (39 corneas from 23 canines, with ages ranging from 8 months old to 3 years old, including 12 male canines and 11 female canines) was divided into 6 zones, and the whole cornea was stained with gold chloride. After staining, corneal nerves formed neural networks at different levels of cornea. There was no significant difference in the number of nerve roots at the corneoscleral limbus between different zones (F = 1.983, p = 0.082), and the nerve roots at the corneoscleral limbus (mean value, 24.43; 95% CI, 23.43-25.42) were evenly distributed. Additionally, there was no significant difference in the number of corneal nerve roots between male and female canines (p = 0.143). There was also no significant difference in the number of corneal nerve roots between adult canines and puppies (p = 0.324). The results of the above analysis will provide a reasonable anatomical basis for selecting the incision location and orientation of penetrating surgery for the canine cornea in veterinary practice.

In vivo confocal microscopic features of naturally acquired canine herpesvirus-1 and feline herpesvirus-1 dendritic and punctate ulcerative keratitis

OBJECTIVE

To describe the in vivo confocal microscopy (IVCM) features of the corneal epithelium and stroma in dogs and cats with herpetic dendritic ulcerative keratitis.

ANIMALS

6 client-owned dogs and 10 client-owned cats with herpetic dendritic ulcerative keratitis (affected group) and 10 dogs and 10 cats from specific-pathogen-free laboratory colonies (nonaffected group).

PROCEDURES

After complete ophthalmic examination, IVCM corneal examination was performed on the clinically diseased eyes of animals in the affected group and on both eyes of animals in the nonaffected group. Results by species were compared between groups.

RESULTS

In the affected group, all 6 dogs had unilateral ocular lesions (total, 6 eyes examined), whereas 7 cats had unilateral lesions and 3 cats had bilateral lesions (total, 13 eyes examined). For the nonaffected group, 20 cat eyes and 20 dog eyes were examined. Corneal epithelial morphological abnormalities were identified in all examined eyes of animals in the affected group and in no examined eyes of the nonaffected group. Hyperreflective punctate opacities and inflammatory cells were present in all epithelial layers in examined eyes of affected animals but were absent in nonaffected animals. Similarly, Langerhans cells and anterior stromal dendritic cells were identified in corneas of eyes examined for animals in the affected group but not in any eye of animals in the nonaffected group. Stromal changes were less consistent in the affected group, but absent in the nonaffected group.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that herpetic dendritic ulcerative keratitis in dogs and cats is associated with microanatomic corneal abnormalities that can be detected by IVCM.

Endothelial keratoplasty for corneal endothelial dystrophy in a dog

OBJECTIVE

To assess the efficacy of an endothelial keratoplasty procedure at defined intervals to 1 year postoperatively for the treatment of corneal endothelial dystrophy (CED) in a canine patient.

PROCEDURE

A dog diagnosed with CED with progressive corneal edema underwent an endothelial keratoplasty. The patient was examined pre- and postoperatively with slit lamp biomicroscopy and ultrasonic pachymetry.

RESULTS

Mean central corneal thickness (CCT) measured with pachymetry was >1400 μm preoperatively and decreased postoperatively to 725 μm. The transplanted donor tissue became transparent 2 weeks postoperatively and incorporated with the recipient cornea. The graft remained transparent throughout the duration of the postoperative period evaluated in this study (2 weeks postoperatively to 1 year). The canine patient was comfortable pre- and postoperatively.

CONCLUSIONS

Endothelial keratoplasty is a potential therapeutic option for canine cases with progressive corneal thickening due to CED. As this is a single case study, further investigation into the use of endothelial keratoplasty to treat CED is warranted. Moreover, canine patients with CED might serve as a surgical model for human patients with Fuchs' Endothelial Corneal Dystrophy.

Comparison of automated vs manual analysis of corneal endothelial cell density and morphology in normal and corneal endothelial dystrophy-affected dogs

OBJECTIVE

To determine the efficacy of automated imaging software of the Nidek ConfoScan 4 confocal biomicroscope at analyzing canine corneal endothelial cell density and morphology in health and disease, by comparing to a manual analysis method.

ANIMAL STUDIED

Nineteen eyes of 10 dogs were evaluated and include three Beagles, three Jack Russell Terriers, and four miscellaneous breeds. Twelve clinically normal and seven eyes affected with corneal endothelial dystrophy (CED) were scanned and analyzed.

PROCEDURES

Endothelial cell density (ECD), mean and standard deviation (SD) of cell area, percent polymegathism, mean and SD of the number of cell sides, and percent pleomorphism were calculated using automated and manual methods for each scan.

RESULTS

The automated analysis showed significantly greater ECD in comparison with the manual frame method due to misidentification of cell domains in CED-affected dogs. No significant differences in ECD were observed between normal and CED-affected dogs in automated analysis, while CED-affected dogs showed significantly lower ECD in manual frame method and planimetry. Using both automated and manual methods, CED-affected dogs showed greater variability of cell area or the number of cell sides than normal dogs.

CONCLUSION

The automated imaging software is unable to accurately identify cell borders in CED-affected dogs resulting in inaccurate estimates of ECD. Thus, manual analysis is recommended for use in clinical trials assessing adverse events associated with novel medical treatments and/or surgical procedures.

Effects of 5% sodium chloride ophthalmic ointment on thickness and morphology of the normal canine cornea

OBJECTIVE

To determine the effect of 5% sodium chloride ophthalmic ointment (5% NaCl) on thickness and morphology of the normal canine cornea using ultrasonic pachymetry (USP), in vivo confocal microscopy (IVCM), and Fourier-domain optical coherence tomography (FD-OCT).

METHODS

Five healthy laboratory Beagles received ophthalmic examinations including USP, IVCM, and FD-OCT prior to and at fixed intervals following treatment. The right and left eyes were treated with 5% NaCl and artificial tears ophthalmic ointment (AT), respectively, every 2 hours for 4 treatments/d (days 2-9), and then hourly for 7 treatments/d (day 10). Treatment groups were statistically compared using mixed-effects linear regression.

RESULTS

Treatment with 5% NaCl resulted in a 12 μm decrease in corneal thickness from baseline (P < .001), while there was no significant difference in corneal thickness between values obtained at baseline and following treatment with AT (P = .82). Epithelial cell density significantly increased from baseline (530 ± 52 cells/mm² ) to 577 ± 43 and 567 ± 15 cells/mm² with 5% NaCl and AT, respectively (P = .003 and .005, respectively). However, keratocyte cell density in the anterior and posterior stroma and endothelial cell density did not significantly differ following treatment with 5% NaCl or AT ointment (P > .05).

CONCLUSIONS

Short-term topical treatment with 5% NaCl decreased corneal thickness in normal dogs with no observable changes in corneal morphology or signs of ocular toxicity.

Phenotypic Characterization of Corneal Endothelial Dystrophy in German Shorthaired and Wirehaired Pointers Using In Vivo Advanced Corneal Imaging and Histopathology

PURPOSE

To evaluate corneal morphology using ultrasonic pachymetry (USP), Fourier-domain optical coherence tomography (FD-OCT), and in vivo confocal microscopy (IVCM) in 2 related canine breeds-German shorthaired pointers (GSHPs) and German wirehaired pointers (GWHPs)-with and without corneal endothelial dystrophy (CED). This condition is characterized by premature endothelial cell degeneration leading to concomitant corneal edema and is similar to Fuchs endothelial corneal dystrophy.

METHODS

Corneas of 10 CED-affected (4 GSHP and 6 GWHP) and 19 unaffected, age-matched (15 GSHP and 4 GWHP) dogs were examined using USP, FD-OCT, and IVCM. A 2-sample t test or Mann-Whitney rank-sum test was used to statistically compare parameters between both groups. Data are presented as mean ± SD or median (range).

RESULTS

Central corneal thickness determined using USP was significantly greater in CED-affected than in unaffected dogs at 1179 (953-1959) and 646 (497-737) μm, respectively (P < 0.001). Central epithelial thickness was found to be significantly decreased in CED-affected versus unaffected dogs at 47 ± 7.1 and 55 ± 7.1 μm, respectively (P = 0.011), using FD-OCT. With IVCM, corneal endothelial density was significantly less (P < 0.001) in 5 dogs with CED versus 19 unaffected controls at 499 ± 315 versus 1805 ± 298 cells/mm, respectively. CED-affected dogs exhibited endothelial pleomorphism and polymegethism, whereas CED-unaffected dogs had regular hexagonal arrangement of cells.

CONCLUSIONS

GSHPs and GWHPs with CED exhibit marked differences in corneal morphology when compared with age-matched control dogs. These 2 CED-affected breeds represent spontaneous, large animal models for human Fuchs endothelial corneal dystrophy.

In Vivo Imaging of Corneal Endothelial Dystrophy in Boston Terriers: A Spontaneous, Canine Model for Fuchs' Endothelial Corneal Dystrophy

Purpose

Boston Terriers (BTs) have a greater prevalence of corneal endothelial dystrophy (CED), in comparison to other canine breeds. Similar to Fuchs' endothelial corneal dystrophy (FECD), this condition is characterized by endothelial cell degeneration with secondary corneal edema. This study assessed corneal morphology using in vivo confocal microscopy (IVCM) and Fourier-domain optical coherence tomography (FD-OCT) in BTs with and without CED.

Methods

The corneas of 16 BTs with CED and 15 unaffected, age-matched BTs underwent clinical evaluation and were imaged using IVCM and FD-OCT. A two-sample t-test or Mann-Whitney rank sum test were used to statistically compare parameters between groups. Data are presented as mean ± SD or median (range).

Results

Mean age did not significantly differ between affected and unaffected dogs at 10.0 ± 2.0 and 10.6 ± 2.4 years, respectively (P = 0.437). Females (69%) were overrepresented among the CED-affected dogs. In CED patients, IVCM demonstrated endothelial polymegathism and pleomorphism. Corneal endothelial density was significantly less (P < 0.001) in dogs with CED (1026 ± 260 cells/mm²) versus age-matched controls (2297 ± 372 cells/mm²). Fourier-domain OCT demonstrated a significant increase (P < 0.01) in central corneal and endothelium-Descemet's complex thickness in dogs with CED versus age-matched controls at 1019 (485–1550) or 536 (464–650) μm and 32 (22–56) or 25 (15–34) μm, respectively.

Conclusions

Corneal endothelial dystrophy in BTs is a bilateral, adult-onset condition that shares many similarities with FECD. Thus, CED could serve as a spontaneous disease model to study the pathogenesis of and develop novel treatments for FECD.

Superficial Keratectomy and Conjunctival Advancement Hood Flap (SKCAHF) for the Management of Bullous Keratopathy: Validation in Dogs With Spontaneous Disease

PURPOSE

To evaluate the efficacy of superficial keratectomy and conjunctival advancement hood flap (SKCAHF) for the treatment of bullous keratopathy in canine patients.

METHODS

Nine dogs (12 eyes) diagnosed with progressive corneal edema underwent superficial keratectomy followed by placement of conjunctival advancement hood flaps. The canine patients were examined pre- and postoperatively using in vivo confocal microscopy, ultrasonic pachymetry (USP), and Fourier-domain optical coherence tomography (FD-OCT). All owners responded to a survey regarding treatment outcomes.

RESULTS

Mean central corneal thickness (CCT) as measured by FD-OCT was 1163 ± 290 μm preoperatively and significantly decreased postoperatively to 795 ± 197 μm (P = 0.001), 869 ± 190 μm (P = 0.005), and 969 ± 162 μm (P = 0.033) at median postoperative evaluations occurring at 2.2, 6.8, and 12.3 months, respectively. Owners reported significant improvement (P < 0.05) in vision and corneal cloudiness at 6.8 and 12.3 months postoperatively. The percentage of cornea covered by the conjunctival flap was correlated (P = 0.0159) with a reduction in CCT by USP at 12.3 months postoperatively. All canine patients were comfortable pre- and postoperatively.

CONCLUSIONS

SKCAHF results in a reduction of corneal thickness in canine patients with bullous keratopathy. The increase in corneal thickness over time, after performing SKCAHF, is likely because of progressive endothelial decompensation. This surgery is a potentially effective intervention for progressive corneal edema in dogs that may have value in treatment of human patients with bullous keratopathy.