A comparative review of evaporative dry eye disease and meibomian gland dysfunction in dogs and humans

Correlation between meibomian gland dysfunction and sebaceous adenitis in dogs

BACKGROUND

Sebaceous adenitis (SA) is an immune-mediated disease targeting the sebaceous glands. Meibomian gland dysfunction is a disease affecting meibomian glands with inflammatory features. Sebaceous and meibomian glands share anatomical, physiological and embryological similarities. The involvement of meibomian glands in dogs with SA is currently unknown.

OBJECTIVES

To evaluate meibomian glands in dogs affected by SA and compare them with healthy dogs.

ANIMALS

Eighteen dogs were enrolled. Nine dogs with SA were retrospectively identified from clinical records and represented the case group. Nine healthy, breed- and age-matched dogs were prospectively enrolled in the control group.

MATERIALS AND METHODS

Both groups underwent dermatological examination, Schirmer tear test-1 (STT-1), tear meniscus height (TMH), slit-lamp biomicroscopy, interferometry (INT) and noncontact infrared meibography (NIM).

RESULTS

One third of SA dogs presented subepithelial crystalline opacities. No significant difference between groups was observed in TMH (p = 0.944) and STT-1 values (p = 0.066). INT (p = 0.016) and NIM grades (p = 0.010) were significantly higher and lower in the SA group compared to the control group, respectively. INT values decreased with age (η = 0.930), while NIM scores (η = 0.935) increased.

CONCLUSIONS

Clinical Relevance: Subepithelial crystalline opacities in SA dogs might reflect a reduced tear film quality. In the absence of standardised methods, INT and NIM proved to be noninvasive and useful methods to examine meibomian glands. Dogs with SA showed a thinner lacrimal lipid layer and more severe meibomian gland abnormalities than control dogs, which seemed to progress with age.

Preliminary clinical evaluation of the treatment efficacy of a temperature-adjustable cryotherapy device for chronic, recurrent blepharitis in dogs

OBJECTIVE

To preliminarily evaluate the treatment efficacy of a temperature-adjustable cryotherapy device for chronic, recurrent blepharitis in dogs.

ANIMALS STUDIED

Five dogs (eight eyes) of different breeds with blepharitis, which was unresponsive to systemic steroids.

PROCEDURES

The dogs were subjected to ophthalmic examination, including Schirmer tear test-1 (STT-1), tear film break-up time (TFBUT) test, and slit-lamp biomicroscope examination. Cryotherapy was performed using a device featuring precise low-temperature control. A bandage lens and ointment (2% hypromellose) were applied before cryotherapy to protect the cornea. Carbon dioxide gas at 0°C was sprayed on the lesion for 10 s. In all patients, only topical antibiotics and corticosteroid were applied twice a day; systemic corticosteroids were not used. Pruritus and ocular discharge were scored based on the visual analog scale (VAS) before and 3 weeks after cryotherapy. Qualitative changes in tear film were measured using STT-1 and a TFBUT test. The effects on erythema and swelling were evaluated by ophthalmic examination.

RESULTS

Pruritus improvement was confirmed in all eight eyes (five dogs). After cryotherapy, the average VAS score of pruritus significantly decreased from 4.12 ± 2.64 to 0.37 ± 0.51 (p < .001), and the average TFBUT significantly increased from 5.75 ± 4.80 to 13.75 ± 4.43 (p = .010). STT-1 and the VAS score of ocular discharge did not significantly differ. Erythema and swelling were improved in three out of eight eyes.

CONCLUSIONS

Cryotherapy is effective in treating blepharitis with pruritus and may become a new treatment option in patients in whom systemic corticosteroids are difficult to administer.

Investigation of ocular surface parameters in dogs with different cephalic conformations using veterinary ocular surface analyzer (OSA-VET)

OBJECTIVE

To compare ocular surface parameters in dogs with different cephalic conformations and evaluate correlations among tests.

ANIMALS STUDIED

Sixty-eight privately owned dogs.

PROCEDURES

The study categorized canine eyes into three groups based on the craniofacial ratio (CFR): brachycephaly (≤0.52), mesocephaly (>0.52 to <0.67), and dolichocephaly (≥0.67). All eyes were examined using an ocular surface analyzer (OSA-VET) to determine lipid layer thickness (LLT) of the tear film, tear meniscus height (TMH), non-invasive tear breakup time (NIBUT), and meibomian gland loss rate of the lower eyelids (MGLRL). Schirmer tear test 1 (STT-1) and tear film breakup time (TBUT) were also performed. Statistical analyses involved one-way ANOVA, Kruskal-Wallis H test, post hoc Holm-Sidak test, and Pearson correlation coefficient.

RESULTS

While STT-1 showed no significant difference among dog groups, brachycephalic dogs had significantly lower values in TBUT, NIBUT, and LLT, and a higher TMH, compared to mesocephalic and dolichocephalic dogs. Additionally, brachycephalic dogs exhibited a significantly higher MGLRL than dolichocephalic dogs. Correlations among tests were generally weak to moderate (r < .6) except for a strong correlation between CFR and LLT (r = .641, p < .001), and between TBUT and NIBUT (r = .899, p < .001).

CONCLUSIONS

Brachycephalic morphology predisposes dogs to a significantly thinner lipid layer and diminished tear film stability, likely due to factors such as impaired meibomian gland function and increased ocular exposure compared to other cephalic conformations, thereby increasing their risk of keratoconjunctivitis sicca (KCS). OSA-VET shows a valuable tool to provide more comprehensive and precise diagnosis for canine ocular surface disorders.

Lateral canthal reconstruction for the treatment of macroblepharon/diamond eye conformation in dogs

PURPOSE

To introduce a novel surgical technique for treatment of macroblepharon and diamond eye conformation in dogs.

METHODS

Lateral canthal reconstruction was used in dogs with prominent eyelid malformations resulting in ocular surface disease. Lateral canthus was resected and new lateral canthus was created using a two-layer closure. This technique was performed either alone or in combination with additional procedure(s). Additionally, this technique was used to resect lateral canthal dermoid.

RESULTS

One hundred and fifty-three eyes of 85 dogs were included in the study. Procedure was done for macroblepharon and/or lateral canthal entropion (149 eyes of 81 dogs) or for lateral canthal dermoid (four eyes of four dogs). Procedure was done either alone (n = 68 eyes) or in combination with additional procedure (n = 85 eyes). Favorable cosmetic outcome and client satisfaction was achieved in all dogs. Good to excellent functional outcome was recorded in all but 6 eyes of 4 dogs, which required additional surgery. Most common complications included slight undercorrection or overcorrection.

CONCLUSIONS

Lateral canthal reconstruction is a simple yet effective surgical procedure for macroblepharon and/or lateral canthal entropion. If done early, it prevents development of secondary eyelid malformation ("pagoda defect") in giant breed dogs. If done after severe eyelid malformation has developed, combining this technique with concurrent pagoda resection is recommended to achieve ideal eyelid conformation. None.

Topical netarsudil for the treatment of primary corneal endothelial degeneration in dogs

This study evaluated the tolerability and efficacy of the topical rho-kinase inhibitor netarsudil for canine primary corneal endothelial degeneration (PCED). Twenty-six eyes of 21 client-owned dogs with PCED were enrolled in a prospective, randomized, vehicle control clinical trial and received topical netarsudil 0.02% (Rhopressa®) or vehicle control twice daily (BID) for the first 4 months. Then, all patients received netarsudil for the next 4 or 8 months. Complete ophthalmic examination, ultrasonic pachymetry, Fourier-domain optical coherence tomography, and in vivo confocal microscopy were performed at baseline and 1, 2, 4, 6, 8 and 12 months. Effect of netarsudil on central corneal thickness (CCT), percentage of cornea with edema, and endothelial cell density (ECD) were evaluated by repeated measures ANOVA. Kaplan-Meier curves and log-rank test were used to compare corneal edema and clinical progression of eyes in netarsudil versus vehicle control groups. All dogs developed conjunctival hyperemia in at least one eye while receiving netarsudil. Unilateral transient reticulated intraepithelial bullae and stromal hemorrhage were observed respectively in 2 dogs in the netarsudil group. Two dogs showed persistently decreased tear production while receiving netarsudil, requiring topical immunomodulatory treatment. No significant differences in CCT, ECD, corneal edema or clinical progression were observed between netarsudil or vehicle treated eyes. When comparing efficacy of topical netarsudil BID and topical ripasudil 0.4% administered four times daily from our previous study, dogs receiving ripasudil had significantly less progression than those receiving netarsudil.

Randomized comparison of in vivo performance of TearLab® and I-PEN® osmometry in normal dogs

OBJECTIVE

To compare tear film (TF) osmolarity measured using TearLab® and I-PEN® osmometers in the same dogs without any ocular surface disease.

ANIMAL STUDIED

Fifty-two dogs (98 eyes) of different breeds were evaluated.

PROCEDURES

Tear film (TF) osmolarity was evaluated at 2-min intervals. The test was randomly determined, and single measurements were performed using each osmometer. Subsequently, complete ophthalmologic examinations were performed based on Schirmer tear test-1 (STT-1) analysis, tear film breakup time (TFBUT), and slit-lamp biomicroscopy. For each osmometer, the mean ± standard deviation of the TF osmolarity was calculated, and a paired Student's t-test was used to compare the values obtained. Pearson correlation analysis was performed to assess the association between osmolarity and other values such as STT-1, TFBUT, and age.

RESULTS

Tear film osmolarity determined using TearLab® (340.42 ± 15.87 mOsm/L) and I-PEN® (321.58 ± 17.39 mOsm/L) were significantly different (p < .001). However, statistical significance could not be confirmed between osmolarity and other values, such as STT-1, TFBUT, and age.

CONCLUSIONS

In dogs, the TF osmolarity values obtained using TearLab® tend to be higher than those obtained using I-PEN®, contrary to that observed in humans. These findings can serve as a reference for establishing normal values for each osmometer for clinical use in measuring TF osmolarity in dogs.