Adjunctive cryotherapy for pigmentary keratitis in dogs: a study of 16 corneas

Ocular Surface Characteristics in Pugs with Pigmentary Keratitis in the Canary Islands, Spain

This study investigated the prevalence of pigmentary keratitis (PK) in Pug-breed dogs and described the ocular surface characteristics associated with this disease. A total of 219 eyes from 110 dogs were examined, with 94.5% of them affected by PK. Age, previous ocular diseases, corneal vascularization, and corneal sensitivity were significantly associated with the presence of PF and the severity of corneal pigmentation. The study also found that low tear production and blinks incomplete with tear signs, as well as reduced corneal sensitivity, were linked to more severe forms of corneal pigmentation. The Tear Ferning Test (TFT) was identified as a valuable tool for evaluating tear quality in dogs, with worse test results indicating a higher risk of severe PK. A lower mean Tear Break-Up Time (TBUT) test was observed in dogs with PK. Additionally, the study observed a statistically significant difference in corneal thickness between the nasal and temporal zones, with the nasal zone being thicker. It was also suggested that sex and fertility status may influence the incidence of PK and the severity of corneal pigmentation. Overall, these findings provide insight into the underlying causes of PK in Pugs and can inform future treatment strategies for this breed.

Diagnosing Corneal Pigmentation in Small Animals

The transparency of the cornea is critical to its role in transmitting light. Loss of corneal transparency results in visual impairment. Corneal pigmentation results from melanin accumulation in the epithelial cells of the cornea. Differential diagnosis for corneal pigmentation include corneal sequestrum, corneal foreign body, limbal melanocytoma, iris prolapse, and dermoid. These conditions must be excluded to reach a diagnosis of corneal pigmentation. A myriad of ocular surface conditions are associated with corneal pigmentation, including qualitative and quantitative tear film deficiency, adnexal disease, corneal ulceration, and breed-related corneal pigmentation syndromes. Accurate etiologic diagnosis is critical to determining effective treatment.

The Effect of the Cryotherapy on the Health and Welfare of Dogs: Preliminary Study

This study is focused on determining the cryotherapeutic effects in the treatment and welfare of dogs. We characterized the basic principles of cryotherapy as well as summarized and statistically processed the current state of the application of this form of therapy in a veterinary practice. Recent scientific studies have shown that cryotherapy is mainly effective in treating skin diseases and problems with the musculoskeletal system including minor injuries caused by excessive muscle strain. It can also be used in combination with anti-inflammatory drugs to treat the respiratory system. Moreover, cryotherapy can be an effective form of treatment for ageing. Our study involved a survey evaluation given to veterinarians in Slovakia, Czechia, and Hungary with a key question regarding their experiences with cryotherapy and cryosurgery in dog therapy. Statistical results demonstrated that Slovak veterinarians do not utilize cryo-methods satisfactorily. A summarization of the reasons could start a change in this unfavourable aspect in Slovak veterinary medicine and contribute to better promotion of cryotherapy application in the therapy of animals.

Effects of commercial amniotic membrane extract on the re-epithelialization time and the early expression of matrix metalloproteinase-9 in cats with experimentally induced corneal ulcers

OBJECTIVES

To investigate whether a commercially available amniotic membrane extract (AME) can accelerate corneal wound healing and suppress the early expression of MMP-9 in the tears of cats with experimentally induced superficial ulcerative keratitis.

PROCEDURES

A total number of 16 cats were included. At the end of keratectomy, cats in the treatment group (TG, n = 8) received 40 μl of AME (EyeQ® Amniotic Eye Drops, Vetrix®) four times daily, while cats in the control group (CG, n = 8) received 40 μl of saline at the same time points. Tears were collected 24 and 48 h after keratectomy, and the total MMP-9 was quantified by ELISA.

RESULTS

The corneal re-epithelialization rate did not differ between groups (p = .26), being 0.48 ± 0.05 mm² /h in the CG and 0.41 ± 0.03 mm² /h in the TG. Similarly, the average time to achieve corneal wound healing did not differ between groups (p = .25) and was 61.50 ± 3.54 h in the CG and 70.50 ± 6.71 h in the TG. The dimensions of the ulcerated areas also did not differ at any time point between the groups (p > .05). In both groups, corneas healed without scarring, pigmentation, or vascularization. The expression of MMP-9 in the tears was similar in both groups at 24 h post-keratectomy, with a slight decrease at 48 h (p > .05).

CONCLUSIONS

The instillation of a commercial AME (EyeQ®) is safe, but it did not decrease the corneal re-epithelialization time or the early expression of MMP-9 in the tears of cats with experimentally induced superficial ulcerative keratitis in this study.

Progressive retrocorneal pigmentation in dogs: A clinical report of 34 cases

OBJECTIVES

To describe the signalment, ophthalmic examination findings, and follow-up of dogs affected with a previously unreported retrocorneal pigmentary lesion.

MATERIALS AND METHODS

Retrospective record evaluation spanning 2009-2019.

RESULTS

Retrocorneal pigmentary lesions were described in 34 patients (46 eyes). German Shepherds (n = 7), Jack Russel terriers (n = 5), and terrier crosses (n = 4) made up 16/34 (47.1%) of the cases. The mean age was 13.5 years (range 1.4-14.2 years), and 16/30 (53.3%) dogs were female. Most dogs were affected unilaterally (22/34 (64.7%)), the others bilaterally, and 5/34 (14.7%) were referred for it while the others were incidentally diagnosed. The lesions affected the ventral, peripheral, inner cornea and had a round/undulated leading edge. The number of corneal clock hours affected was known for 41/46 (89.1%) eyes and involved 1-3 clock hours in 32/41 (78.1%) eyes, 4-6 in 6/41 (14.6%), 7-9 in 2/41 (4.9%), and 10 in 1/41 (2.4%). The central cornea was affected in 9/46 (19.6%) eyes, and in 5/9 (55.6%), the median corneal clarity score was G2 (scale: G0-G4). The commonest additional findings included free-floating uveal cysts (11/34 dogs, 32.4%), cataracts (6/34 dogs, 17.6%), and primary glaucoma (5/34 dogs, 14.7%). Gonioscopy was available in 16/34 (47.1%) dogs and was normal except in primary glaucoma cases. Follow-up was documented in 13/34 (38.2%) dogs with a mean follow-up of 17 months (range: 5-26 months). Lesion progression was documented in 6/13 (46.2%) dogs.

CONCLUSIONS

Retrocorneal pigmentation occurs as a slowly progressive lesion of older dogs that could impact vision. Histological studies of affected eyes are warranted.

The effects of soft cryotherapy on conjunctiva and cornea in isolated pig eyes and comparison with standard liquid nitrogen: A pilot ex vivo study

PURPOSE

To evaluate the immediate effects on cornea and conjunctiva of a cryosurgical method based on the application of a dimethyl ether, propane and isobutene solution (DMEPI, Histofreezer^® ), and of Liquid Nitrogen (LN₂ ; Cry-Ac Cryogun^® ).

METHODS

A total of 52 isolated pig eyes were obtained at the slaughterhouse, preserved for less than one hour in Ringer Lactate and divided into four groups. The first group included eyes treated with two applications of DMEPI in the center of the cornea, the second group eyes treated with DMEPI on the third eyelid's conjunctiva, the third group eyes treated with LN₂ on the third eyelid's conjunctiva and the fourth group included eyes treated with LN₂ on the central cornea. Each cryogen application (0.8 cm area) lasted 40 seconds. Each group included one (untreated) control eye. The eyes were submitted for routine histopathological evaluation. Histological alterations were recorded and scored with a semiquantitative scoring system.

RESULTS

No tissue alteration was detected on the conjunctiva, in any of the groups. Treated corneas showed mild to moderate cytoplasmic vacuolization of epithelial cells, shrinkage and hypereosinophilia of small groups of basal epithelial cells and stromal cleft formation.

CONCLUSIONS

Soft cryosurgery caused no severe acute histologically detectable damage to cornea and conjunctiva in isolated pig eyes, and no significant difference was observed when LN₂ and DMEPI treatments were compared. Further in vivo studies should be performed in order to verify possible delayed effects and the clinical efficacy of DMEPI cryosurgery in specific corneal and/or conjunctival diseases.

Pigmentary keratitis in pugs in the United Kingdom: prevalence and associated features

Background

Pigmentary keratitis (PK) is commonly recognised in Pugs, but its aetiology is not completely understood. The aim of this study was to determine the prevalence and associated features of PK in Pugs in the United Kingdom (UK).

Results

A total of 210 Pugs (420 eyes) were recruited from 12 UK dog shows and social events. The median age of Pugs recruited was 2.50 years (range 0.25–16.25 years). Pigmentary keratitis was detected in 369/420 (87.8%) eyes and in at least one eye 193/210 (91.9%) Pugs, of which 17/193 (8.8%) were affected unilaterally and 176/193 (91.2%) bilaterally. Pigmentary keratitis was typically mild to moderate (46.3 and 49.9% of eyes, respectively). Detection of PK was significantly associated with increased age (P = 0.002) and the presence of medial entropion of the lower eyelid (MELE) (P = 0.001). Severity of PK was significantly associated with the grade of MELE (P < 0.001). There was also a correlation between the presence of limbal pigment and PK (P = 0.036) that warrants further study.

Conclusions

This study estimated a high disease prevalence of PK in UK Pugs, and demonstrated significant associations with age and the presence of MELE. These associations, which have not been previously reported, offer an insight into the underlying pathophysiology of this condition in Pugs. The results encourage further population research, such as prospective longitudinal studies. These findings also support the development of clinical and breeding strategies based on the reduction of MELE and, possibly, limbal pigment.

Preliminary results of a prospective study of inter- and intra-user variability of the Royal Veterinary College corneal clarity score (RVC-CCS) for use in veterinary practice

OBJECTIVE

To introduce a new corneal clarity score for use in small animals and describe its inter- and intra-user variability.

ANIMALS STUDIED

Twelve dogs and two cats with corneal abnormalities and five dogs with healthy corneas.

MATERIALS AND METHODS

Four examiners scored every patient twice and never consecutively, focusing on the central cornea. The peripheral cornea was scored separately. The following scoring system was used to describe corneal clarity: G0: no fundus reflection is visible on retroillumination (RI) using a head-mounted indirect ophthalmoscope. G1: a fundus reflection is visible with RI. G2: a 0.1-mm diameter light beam is visible on the anterior surface of the iris and/or lens. G3: gross fundic features are visible when viewed with indirect ophthalmoscopy (IO) using a head-mounted indirect ophthalmoscope and a hand-held 30D lens, although fine details are not clear. G4: fine details of the fundic features are clearly visible with IO. The minimum grades given were analyzed for inter- and intra-user variability with kappa analysis.

RESULTS

Intra- and interuser variability of the central corneal clarity ranged from 0.78 to 0.96, showing substantial to almost perfect reproducibility, and from 0.66 to 0.91, showing substantial to almost perfect reliability, respectively. Intra- and interuser variability of the peripheral cornea ranged from 0.83 to 0.95, showing almost perfect agreement, and from 0.53 to 0.91, showing moderate to almost perfect agreement.

CONCLUSIONS

The RVC-CCS is well suited to assess and monitor central corneal clarity in small animals and to compare outcomes between studies and different surgeons.

A retrospective survey of ocular abnormalities in pugs: 130 cases

OBJECTIVES

To determine the types and frequency of ophthalmic findings in pugs.

MATERIALS AND METHODS

Retrospective analysis of case records of pugs presented to an ophthalmology unit between 2001 and 2012. Ophthalmological findings were correlated with age, gender, presenting signs and time of onset of disease.

RESULTS

In total, 130 pugs (258 eyes) with a mean (±sd) age of 2 · 8 (±2 · 87) years were examined. Ocular abnormalities identified included keratoconjunctivitis sicca (n = 39 eyes), macroblepharon (n = 258 eyes), entropion (n = 258 eyes), distichiasis (n = 56 eyes), ectopic cilia (n = 8 eyes), conjunctivitis (n = 88 eyes), corneal pigmentation (n = 101 eyes), opacity (n = 63 eyes), ulceration (n = 46 eyes), vascularisation (n = 35 eyes), iris-to-iris persistent pupillary membranes (n = 21 eyes) and cataract (n = 18). Keratoconjunctivitis sicca was significantly associated with the presence of corneal pigmentation (P = 0 · 007 for left eyes; P = 0 · 043 for right eyes). However corneal pigmentation was also identified in pugs (n = 61) without keratoconjunctivitis sicca. There was a significant influence of ectopic cilia on corneal ulceration (P < 0 · 001). Younger dogs (mean age, 1 · 28 (±0 · 45) years) were significantly more affected by distichiasis.

CLINICAL SIGNIFICANCE

The high number of cases of corneal pigmentation without keratoconjunctivitis sicca suggests that there may be additional yet undetermined factors involved in the development of corneal pigmentation in pugs.