Introduction

Entropion is a common disorder affecting the adnexa of dogs. It is characterized by the inversion of the eyelid margin resulting in trichiasis, epiphora, keratitis, and ulceration, which can be superficial or globe threatening. Entropion can be classified as primary (congenital or developmental) or secondary (acquired). Primary entropion has been reported in the Shar-Pei, Chow Chow, Bouvier des Flandres, Rottweiler, Great Dane, Saint Bernard, Leonberger, Labrador Retriever, Golden Retriever, German Pointer, English Springer Spaniel, English and American Cocker Spaniels, and English Bulldog.^1,2 A difference in tension between the orbicularis oculi muscle and malaris muscle is proposed to be the cause of developmental entropion.¹ Other factors such as eyelid length, conformation of the orbit and skull, gender, and facial skin folds around the eyes can influence the development of entropion.¹

Temporary tacking procedures in puppies are rationalized because the entropion in young puppies may be transient due to anatomical differences in development of the face.^2,3 Tacking procedures are typically performed without general anesthesia in young puppies, in part to avoid potential anesthetic risks in pediatric patients. In addition to anesthesia considerations, there is concern that young dogs surgically corrected before development is complete may risk postoperative recurrence or overcorrection.⁴ Several veterinary ophthalmology publications recommend delaying entropion surgery until the dog has reached facial maturity, up to 1.5 to 2 years old for giant breeds.^1–3,4 Since temporary tacking sutures usually remain in place for 2 to 3 weeks, they may need to be repeated before the dog has reached maturity if the entropion persists.^2,3,5 Temporary tacking sutures performed in young puppies are purported to correct entropion because of the formation of scar tissue around the sutures, which can remain and result in permanent correction of the entropion.¹ No study has reported the success rate of temporary tacking procedures in a large population of young dogs of different ages and breeds with long-term follow-up. Furthermore, to the authors’ knowledge, no study has evaluated the success and complication rates of entropion surgery performed in dogs younger than 1 year of age.

The authors theorized that entropion surgery could be successful in young dogs and should be performed as early as necessary for long-term comfort; however, an attempt at temporary tacking may be appropriate in very young puppies. The purpose of this study was to report the long-term outcomes of entropion surgery in young dogs compared to that performed in adult dogs and to determine whether entropion surgery should be delayed after 1 year of age. This study also evaluated the success rates of temporary tacking sutures and effect of age on the outcome of this procedure to guide the clinician on whether temporary tacking sutures should be performed prior to entropion surgery.

Methods

A retrospective study was conducted, and medical records were selected of dogs younger than 3 years old diagnosed with primary lower eyelid entropion between January 2005 and July 2020 at Ophthalmology for Animals and Animal Eye Specialists. Signalment, age at presentation, concurrent ophthalmic abnormalities, age at the time of a temporary tacking procedure, age at the time of entropion surgery, weight at the time of surgery, eye(s) affected, complications, date of the last recheck exam, and outcome were recorded. A positive outcome was defined as a normal eyelid position and a comfortable eye. Recurrence of entropion was defined as an eye requiring an additional surgery or ongoing therapy to control signs associated with the recurrence of entropion.

The study was divided into 2 sections. The first section consisted of the evaluation of the temporary tacking procedure. Patients were subdivided into 2 groups. One group included dogs in which a temporary tacking procedure was performed but surgery was never required. The second group was composed of dogs in which entropion recurred following a temporary tacking procedure. The temporary tacking procedure was either a lateral temporary tarsorrhaphy or placement of vertical mattress sutures or staples and was performed by the referring veterinarian or a veterinary ophthalmologist. Dogs were included if they had reached 1 year of age at the last follow-up or recurrence of the entropion was documented prior to 1 year of age.

In the second part of the study, the population of dogs requiring entropion surgery was subdivided into 2 groups. Dogs from the first section of the study were included in the second part of the study if the surgery was done by an ophthalmologist and at least 6 months’ follow-up was available. The juvenile group was composed of dogs < 1 year of age at the time of entropion surgery. The adult group was composed of dogs that were over 1 year of age at the time of surgery. Dogs with < 6 months’ follow-up but recurrence of the entropion following surgery were also included.

The probability of success of entropion surgery was determined using logit mixed models, as there were 2 measurements/dog (2 eyes). Individual dogs were used as the random effect and risk factor variables (age, sex, breed types, eyelid, age at surgery, age at presentation, and tacking) as the fixed effect. Variable selection was performed by backward selection (P = .1 to retain). Missing data were treated by list-wise deletion. Residual plots were used to screen for outliers and fit of the model. Multicollinearity of variables was also assessed by calculating their variance inflation factors in corresponding linear models with a cutoff of 10. A similar approach was used to model the probability of success of tacking surgeries. A Mann-Whitney U test was performed to evaluate the median difference between the age of dogs successfully treated with temporary tacking procedure and those requiring surgery. A Fisher exact test was used to compare the success rate of entropion surgery between the juvenile group and adult group. An α of 0.05 was used for statistical significance. R (version 4.0.4; R foundation for Statistical Computing) was used for statistical analysis.

Results

Discussion

This retrospective study demonstrated that there was no significant difference in outcome if entropion surgery was performed early in the dog’s life, during the active growth phase, as compared to after 1 year of age. Entropion surgery in juvenile dogs resulted in a similar rate of complications and recurrence of entropion compared to adult dogs. No factors were identified as affecting the success rate of entropion surgery in young or adult dogs.

This study reported a success rate of 36.6% with a temporary tacking procedure in dogs. The group of dogs successfully treated with a temporary tacking procedure were younger than the individuals requiring surgery. However, recurrence of entropion following a temporary tacking procedure occurred in dogs of any age, and age was not a significant factor affecting the success rate of a temporary tacking procedure when evaluated in the mixed model. This means that younger dogs may have a higher success rate following a temporary tacking procedure as compared to older dogs, but clients should be aware of the possibility of recurrence for dogs of all ages. Unfortunately, no factors were identified to help predict which dogs are most likely to be permanently resolved with this technique. The effect of age on the success rate of the temporary tacking procedure could have been different if a larger number of pediatric-aged animals had been included. Animals presented by the breeder at an early age were lost to follow-up when adopted and therefore excluded.

The success rate of the temporary tacking procedure was much lower (36.6%) than the success rates reported in previous studies (57% to 77%).^6,7,8 Multiple temporary tacking techniques can be used to evert the eyelids.^4,5,7,8 Temporary tacking sutures were first described in 1980 and resulted in permanent correction of entropion in 77% of Shar-Pei puppies.^4,6 The use of lateral tarsorrhaphy sutures or a fornix-based suture placement under general anesthesia can also provide temporary relief from the pain associated with entropion; these techniques have a reported success rate of 57% or 70%, respectively.^7,8 However, all juvenile dogs treated with the fornix-based suture technique necessitated entropion surgery after the procedure.⁸ Like our study, the retrospective studies done by Williams⁸ and Lewin⁷ included a variety of breeds and dogs of different ages; however, Lenarduzzi⁶ only looked at the temporary tacking procedure in young Shar-Pei puppies. Limitations of these studies were the small number of dogs included and short follow-up period, which was either not mentioned or < 6 months.^4,7,8 It is possible that the population of dogs included in the present study differed from the population of dogs in studies conducted 20 to 40 years ago because selective breeding may have led to changes in breed-related facial conformation. These factors may have been responsible for the lower success rate of the temporary tacking procedure in our study. Because of the nature of retrospective studies, it is impossible to know exactly when entropion reoccurs after a temporary tacking procedure. In our study, entropion surgery after failure of a temporary tacking procedure occurred in a time range beginning immediately after the removal of the sutures to up to 17 months after the procedure was performed. It is possible that the previous study would have had a lower success rate if a longer follow-up had been performed. A prospective study with at least 6 to 12 months of follow-up and fewer variables would be required to better determine the success rate of the temporary tacking procedure.

The success rate of entropion surgery in this retrospective study was 89.6%, which is lower than the 94.1% of dogs treated successfully with 1 procedure in the study by Read and Broun⁹ when the entropion was corrected using a combination of the Hotz-Celsus surgery with a lateral eyelid wedge resection. However, the success rate in our study was higher than the success rate of 85.5% reported by Bigelbach¹⁰ when a combined tarsorrhaphy-canthoplasty technique was used and similar to the success rate of 90.4% by Robertson and Roberts¹¹ with a lateral canthal tendonectomy surgery. Different surgeons and surgical techniques may have affected the success rate in our study. However, the success rates of all these studies are similar and comparable clinically.

Since primary entropion is usually diagnosed at an early age and known to be a painful and sight-threatening condition, it may be unwarranted for dogs to wait for maturity for a definitive surgery to be performed. Fourteen percent of eyes were presented with a corneal ulcer at the initial presentation, with some of them being globe threatening and 6.9% with corneal granulation tissue or corneal fibrosis. Chronic pain has also been associated with changes in learning and performance in dogs. Furthermore, animals in pain express higher levels of anxiety and can also develop adjunctive behavior such as comfort seeking or defensive aggression behavior.¹² Hence, prolonged discomfort from entropion could harm the optimal development of the dog’s behavior, prompting correction of the entropion early in the process.

Mild to moderate fear when examined by the veterinarian is reported in 41% of dogs, and 14% of dogs experience severe to extreme fear during veterinary visits.¹³ Multiple factors contribute to this fear. The breed group, employment, source, and size of the dog are the most important predictive factors. Toy breeds, mixed breeds, hounds, dogs involved in field trials or hunting, dogs purchased from a pet store, and dogs smaller than 22 kg have a higher score of fear when examined by a veterinarian compared to dogs used for breeding and showing, with a working background, from a breeder, and larger than 22 kg.¹³ But these factors only contribute to a small percentage of the dog’s predisposition for the development of fear in veterinary clinics, and individual experience such as the association made with handling and potential painful experiences are of much greater importance.¹³ The temporary tacking procedure is described as being performed with topical ophthalmic anesthetic and manual restraint, with the use of local anesthesia or under general anesthesia.^4–8 Staples and skin-crushing methods can also be considered animal-unfriendly techniques.¹ Negative veterinary experiences can have a long-term impact on a dog’s fear of veterinary examination, hence the importance of proper sedation and analgesia when a temporary tacking procedure is performed. Because of the cost associated with sedation and general anesthesia, stress associated with these visits and procedures, and high probability of recurrence of entropion following a temporary tacking procedure, the veterinarian should take these factors into consideration when deciding whether a temporary tacking procedure should be performed or repeated versus surgical correction of the entropion in juvenile dogs.

Pediatric patients < 12 weeks of age can be considered at increased risk of complications during general anesthesia because of their immature cardiovascular, hepatic, and renal systems.^14,15 Age-related hypoalbuminemia and increased permeability of the blood-brain barrier make these patients more sensitive to anesthetic drugs. Furthermore, because of their small body size and low body fat percentage, pediatric animals are highly susceptible to hypothermia, which can increase their risk of complications. Neutering of dogs between the ages of 6 weeks and 16 weeks is reported and associated with minimal anesthetic complications.^16,17 By using age-appropriate anesthetic protocols and monitoring, entropion surgery can be performed safely in puppies prior to maturity.

Limitations of this study were inherent to retrospective studies in veterinary medicine. Incomplete medical records and animals’ loss to follow-up limit the capacity to draw conclusions. It is possible that our results were influenced by the population referred to a veterinary ophthalmologist. Animals successfully treated with temporary tacking procedure by the primary veterinarian were not referred for entropion surgery and therefore not included in this retrospective study. Because of this, it was impossible to evaluate whether the success rate of the temporary tacking procedure is better if performed by the primary veterinarian or an ophthalmologist. Moreover, the small number of animals of each breed precluded breed comparisons. To try to avoid this limitation, breeds were grouped into giant, brachycephalic, and other breeds; nevertheless, no significant difference in success after entropion surgery was found between breeds or breed groups. Lastly, 1 year of age was somewhat arbitrarily defined as the separation between age groups. This is a practical way to define study groups but doesn’t take into consideration that dogs of different breeds reach maturity at different ages.^18,19 To conclude whether a dog has reached maturity is subjective and unfortunately relatively impractical in a retrospective study; therefore, groups were divided by age to provide consistency.

In conclusion, the outcome of entropion surgery in juvenile dogs resulted in resolution of the disease with little risk of short- or long-term complications including overcorrection. Temporary tacking procedures can be attempted in younger dogs, but the owner should be aware of the possibility of recurrence. Repeated temporary tacking procedures may not be necessary for the intention of delaying surgery until maturity, as early surgery may be beneficial.

Disclosures

The authors have nothing to disclose. No AI-assisted technologies were used in the generation of this manuscript.

Funding

The authors have nothing to disclose.