A major review on disorders of the animal lacrimal drainage systems: Evolutionary perspectives and comparisons with humans

Nasolacrimal sac foreign body extraction using vitreoretinal forceps in 28 dogs

PURPOSE

To describe a novel technique of nasolacrimal foreign body extraction in dogs by using a 20G vitreoretinal forceps introduced through the superior lacrimal punctum.

METHODS

A retrospective review of the medical records of dogs with dacryocystitis due to nasolacrimal foreign bodies between the years 2001 and 2022 was performed. We recorded the breed, age, affected eye, type and number of foreign bodies, concomitant diseases, and the use of imaging techniques. All animals underwent the same procedure of a 20G vitreoretinal forceps insertion through the upper canaliculus reaching the lacrimal sac and retrograde extraction of the foreign bodies.

RESULTS

A total of 28 dogs were included, 16 males and 12 females, with a mean (±SD) age of 4.7 (±3.2) years. The most common breeds were Wire-Haired Dachshund (4/28; 14.29%) and Labrador Retriever (3/28; 10.71%). Additional imaging techniques were used, such as orbital ultrasound in 13 cases (13/28; 46.43%) and computed tomography in one case (1/28; 3.57%). The most common type of foreign body retrieved was grass awns, although seeds and plant debris were also found. Dacryocystitis resolved after removal of the foreign body and appropriate medical therapy was ensured in all cases in the 1-month postprocedure follow-up.

CONCLUSION

Extraction of nasolacrimal foreign bodies with vitreoretinal forceps is a novel, noninvasive, and easily applicable technique that, although not successful in all cases, can be attempted before performing more aggressive surgery.

Effect of Topical 5-Fluorouracil on Lacrimal Drainage System: Histopathological Evidence From Animal Experiments and Potential Clinical Implications

PURPOSE

The purpose of this study is to investigate the histopathological changes in the lacrimal drainage system of rabbits following the application of 1% topical 5-fluorouracil (5-FU) for 4 weeks.

METHODS

Ten eyes of 10 healthy New Zealand white rabbits were subjected to topical instillation of 1% (10 mg/mL) 5-FU, 1 drop 4 times a day for 4 weeks. Rabbits underwent a detailed ocular examination including eyelids, ocular surface, punctal, peri-punctal changes, and nasolacrimal duct patency at baseline and after 4 weeks of 5-FU. The rabbits were then sacrificed, and the eyelid, conjunctiva, lacrimal gland, and the entire lacrimal drainage system were retrieved for histopathological analysis as per standard protocols.

RESULTS

Clinically demonstrable peripunctal changes and canalicular stenosis were noted in 6 (60%, 6/10) rabbits. Two of these (20%, 2/10) had additional complete regurgitation of clear fluid, indicating a nasolacrimal duct obstruction. The remaining 4 (40%, 4/10) clinically did not demonstrate lacrimal drainage changes and were patent on irrigation. The conjunctiva showed focal loss of goblet cells in several areas. Significant changes were noted in the canalicular, lacrimal sac, and the nasolacrimal duct tissues in the form of epithelial hyperplasia, subepithelial inflammation, edema, dilated and congested vessels, and fibrosis. The lacrimal gland, eyelid tissue (excluding tarsal conjunctiva), and cornea showed no significant histopathological changes.

CONCLUSIONS

Clinical and histopathological changes were noted in the lacrimal drainage system of rabbits subjected to topical 5-FU application. These findings can have potential clinical implications for patients receiving 5-FU therapy.

Case series: Computed tomography (CT) demonstrates lacrimal canal involvement in koalas (Phascolarctos cinereus) with maxillary incisor dental disease

Dental disease is common in wild and captive koalas. Effective treatments are limited and dental disease may not be recognised until it is quite severe. We describe the appearance of varying severities of dental disease on computed tomography (CT) images in a case series of six koalas. This case series demonstrates the use of CT to detect both mild and severe dental disease in koalas. The study also documents the normal CT appearance of the nasolacrimal duct in the koala. The only clinical abnormality in koalas with the mildest dental disease was ocular discharge. Computed tomography findings associated with ocular discharge were periapical lysis of first maxillary incisors, lacrimal canal remodelling and subsequent nasolacrimal duct obstruction. Dental disease should be a differential diagnosis for ocular discharge in koalas and CT examination enables visualisation of early stages of dental disease.

Anatomy of the nasolacrimal duct in Persian cats determined by computed tomographic dacryocystography

OBJECTIVE

This study sought to describe the anatomical characteristics of the nasolacrimal duct of Persian cats as observed by computed tomographic dacryocystography.

ANIMAL STUDIED

Ten cats weighing 3-6 kg (three live cats and seven cadaveric specimens).

PROCEDURES

The animals were submitted to bilateral computed tomographic dacryocystography, totaling 20 nasolacrimal ducts. Dorsal, sagittal, and transverse planes were studied. Two additional skulls were also dissected following latex injection into the nasolacrimal duct. The length and width of the nasolacrimal duct and lacrimal canaliculi, and the distance between the nasolacrimal duct and the root of the upper canine tooth at the point of closest proximity were measured.

RESULTS

The nasolacrimal duct followed a convoluted course, particularly in the middle and rostral portions. Duct stenosis (width reduction equal to or >75%) and dilations (width increase equal to or >50%) were also detected, particularly in the rostral portion. Nasolacrimal duct length and width ranged from 1.3 to 1.5 cm and 1.5 to 2.3 mm, respectively. Mean lacrimal canaliculus length and width corresponded to 3.1 mm and 0.4 mm, respectively. Mean distance from the nasolacrimal duct to the canine tooth was 2.4 mm. The root of this tooth interfered with the course of the nasolacrimal duct.

CONCLUSION

This study provided anatomical information for clinical assessment of the nasolacrimal drainage system in Persian cats.

Is it necessary to wait several minutes between applications of different topical ophthalmic solutions? A preliminary study with tropicamide eye drops in healthy dogs

OBJECTIVE

To evaluate the efficacy of topical tropicamide when placed at different time intervals before or after a saline drop.

ANIMALS STUDIED

Eight healthy Labrador and golden retriever dogs.

PROCEDURES

The effect of 1% tropicamide on pupillary diameter (PD) was measured over 240 min when administered alone (control) and then 1 and 5 min prior to, or following, application of a saline drop, with 1-week washout between each of the five trials. Data were analyzed using repeated-measures ANOVA and Tukey post hoc test.

RESULTS

Only 6/110 pairwise comparisons among the 5 trials were statistically significant (p ≤ .035), with post-hoc analysis showing no significant differences (p ≥ .14) between the overall means of all trials. In all five trials, maximal PD was reached 30 min after tropicamide application and maintained until 210 min for 180 min (p = .0005).

CONCLUSIONS

Our results suggest that waiting 1 min between applications of different ophthalmic solutions may be sufficient for maximal drug effect. Care should be taken when extrapolating these results to other species and different ophthalmic formulations.

Developing the rabbit canalicular injury model: Biophysical changes of masterkaR stents and implications for future research

BACKGROUND

To describe the preparation of a rabbit lacrimal canalicular injury model, assess the canalicular healing, and determine the suitability of this model to study the biophysical changes of mono-canalicular stents.

METHODS

Twelve canaliculi of twelve eyes of six healthy New Zealand white rabbits were included in the study. A canalicular injury model was prepared under general anesthesia. The injury was then repaired using modified Masterka^R stents and peri-canalicular wound closure. The stents were extubated at eight weeks, and specific surgical techniques used to obtain the healed canaliculi. Histopathological analysis was carried out on the canaliculi samples, and the stents were examined ultra-structurally using the scanning electron microscopy (SEM).

RESULTS

At eight weeks, the canaliculus maintained its integrity and demonstrated good healing with epithelium continuity. However, the area of incision and suture showed hyperplastic epithelium with significant sub-epithelial fibrosis. Lacrimal irrigation following stent extubation confirmed patency of all the canalicular systems studied. SEM study revealed the biofilm formation and physical deposits over the external, luminal, and adluminal surfaces of all Masterka^R stents with intervening skip areas. Although these changes were seen all over the stent, the most preferential site for physical deposits and biofilm aggregates was the ampullary portion of the stent's head. None of the rabbits showed any evidence of a post-operative ocular infection or local inflammation.

CONCLUSION

Rabbits are good candidates for the preparation of a lacrimal canalicular injury model. The canalicular tissues demonstrate changes following repair. The biophysical changes on the extubated stents resembled those obtained from the humans.

An eye on the dog as the scientist's best friend for translational research in ophthalmology: Focus on the ocular surface

Preclinical animal studies provide valuable opportunities to better understand human diseases and contribute to major advances in medicine. This review provides a comprehensive overview of ocular parameters in humans and selected animals, with a focus on the ocular surface, detailing species differences in ocular surface anatomy, physiology, tear film dynamics and tear film composition. We describe major pitfalls that tremendously limit the translational potential of traditional laboratory animals (i.e., rabbits, mice, and rats) in ophthalmic research, and highlight the benefits of integrating companion dogs with clinical analogues to human diseases into preclinical pharmacology studies. This One Health approach can help accelerate and improve the framework in which ophthalmic research is translated to the human clinic. Studies can be conducted in canine subjects with naturally occurring or noninvasively induced ocular surface disorders (e.g., dry eye disease, conjunctivitis), reviewed herein, and tear fluid can be easily retrieved from canine eyes for various bioanalytical purposes. In this review, we discuss common tear collection methods, including capillary tubes and Schirmer tear strips, and provide guidelines for tear sampling and extraction to improve the reliability of analyte quantification (drugs, proteins, others).