Whether you’re a new graduate or a general practitioner, keeping up with the latest evidence in veterinary medicine can be hard work. This month, we’ve gathered some of the best studies published since 2023 in small animal ophthalmology, summarised them for you and produced key takeaways so you can discover why and how they might change the way you practise.
Four studies in small animal ophthalmology
1. Prevalence and outcome of lens capsule disruption in routine canine cataract surgery
This study, published in Veterinary Ophthalmology, retrospectively looked at the medical records of 520 eyes that underwent phacoemulsification at the Queen Mother Hospital for Animals, Royal Veterinary College. The authors included eyes with and without lens capsule disruption (LCD) and then looked at the aetiology of the LCD, the location of the LCD, whether a lens was placed and the results of the surgery, including any vision loss up to two years later.
Why is the study important for small animal ophthalmology?
It also revealed the first reported cases in the literature of spontaneous LCD in non-diabetic patients with non-rapidly progressing cataracts
LCD is a recognised complication of cataracts and cataract surgery in human and small animal ophthalmology, but this study provides more information as to the prevalence and risks of LCD, which is important for surgical planning and informed consent. It also revealed the first reported cases in the literature of spontaneous LCD in non-diabetic patients with non-rapidly progressing cataracts.
Key takeaways for vets
- LCDs were shown to be more common than previously thought: 27.9 percent of eyes were affected
- Of the spontaneous LCDs, 73.1 percent were diagnosed on preoperative ocular ultrasound (eg irregularity of lens capsule, hyperechoic amorphous material within the vitreous), making this a useful method for preoperative planning, especially where opacity from the cataracts prevents good visualisation with a slit lamp
- Spontaneous LCDs are more common in diabetic patients, but were present in other types of patients, making preoperative ultrasound important in all patients, not just those at high risk
- Although the placement of an intraocular lens was significantly decreased in the LCD group, it was still 73.8 percent, showing that with an experienced surgeon, modern lenses and good planning, these eyes can still have optimal surgery and good potential for vision restoration
- Despite this, eyes without LCD were significantly more likely to have vision at one year than those with LCD, mainly due to retinal detachment
- Post-operative complications were not significantly more likely in either group when measured across all timepoints
You can read the full paper here.
2. Treatment of canine spontaneous chronic corneal epithelial defects with corneal thermal cautery
In this retrospective study, the authors looked at 20 years of records from the Veterinary School of Toulouse to find patients who had had treatment for spontaneous chronic corneal epithelial defects (SCEEDs) using corneal thermal cautery (CTC) alongside debridement (eg cotton tip debridement or diamond burr debridement). They found records for 89 eyes (77 dogs from 28 breeds) that met the criteria, then examined the variables leading to healing rates and complication rates.
Why is this an important study in small animal ophthalmology?
SCEEDs (also known as indolent ulcers, Boxer ulcers and refractory/recurrent corneal erosions) are common and painful, and can last for weeks or months if not handled correctly. Corneal thermal cautery was first described in animals in 2004 with a 100 percent success rate, but just nine cases were investigated. This paper aimed to describe the outcomes of CTC in a larger group of dogs.
Key takeaways for vets
- Brachycephalic breeds, especially French Bulldogs, English Bulldogs and Boxers, continue to be over-represented in SCEEDs cases
- The average success rate for the first procedure was about 65.1 percent, but didn’t differ between those treated with CTC and cotton bud debridement versus those treated with CTC and diamond burr debridement. The success rate could be underestimated though, as 23 dogs were lost to follow-up
- The complication rate was 22 percent, with corneal pigmentation being the most common complication
- CTC is a safe and effective adjunct to epithelial debridement for dogs with SCEEDs, and can be undertaken with no sedation, unlike the main alternative, which is a grid keratotomy
You can read the full paper here.
3. Detection of Mycoplasma spp. and feline calicivirus in cats with ocular surface disease
The authors analysed samples from 255 cats with ocular surface disease (OSD) living in animal shelters in the US. Each cat was scored using an objective scoring scheme, then the sample was taken and the pathogens present were compared.
Why is this an important study in small animal ophthalmology?
Ocular surface disease is extremely common, especially in young cats and those in shelters. Since many of the diseases found to be present are highly contagious and can have long-lasting effects, understanding the likelihood of particular diseases being the cause of OSD is helpful. In addition, this paper adds to the evidence that Mycoplasma and feline calicivirus may act as primary pathogens in OSD.
Key takeaways for vets
Non-infectious causes such as allergic/hypersensitivity conditions, tear film disorders and eosinophilic conjunctivitis should be considered by vets being presented with OSD
- Clinical scores of OSD were similar between different numbers and types of pathogens, so clinical examination is not recommended as a way to diagnose the cause of OSD
- While herpesvirus (FHV-1) was commonly detected (42.7 percent), Mycoplasma was more commonly detected (76.4 percent). This is interesting, as FHV-1 was hypothesised by the authors as being the most common pathogen. In addition, lots of treatments for OSD target viral DNA polymerase, and these would be ineffective if FHV-1 isn’t present
- None of the tested pathogens were found in 7.1 percent of the samples, suggesting that non-infectious OSD (or OSD caused by an unidentified pathogen) is also common in shelter cats. Non-infectious causes such as allergic/hypersensitivity conditions, tear film disorders and eosinophilic conjunctivitis should be considered by vets being presented with OSD
- Mycoplasma was the most common mono-infection (12.5 percent of animals), increasing the likelihood of this pathogen being capable of causing OSD in cats. However, it’s also possible that these patients had a non-clinical cause or an unidentified primary pathogen, and Mycoplasma was incidental
You can read the full paper here.
4. Schirmer tear test with open or closed eyelids: an evaluation in brachycephalic and non-brachycephalic dogs
In this paper from Veterinary Ophthalmology, the authors compared Schirmer tear test (STT) readings in healthy dogs. They tested 15 Shih Tzus (as a brachycephalic breed) and 15 Labrador Retrievers (as a non-brachycephalic breed) with their eyes open or closed, then, after a 30-minute break, with the other testing method. The idea was to discover the extent to which the eyelid status (open or closed) influenced STT readings.
Why is this an important study in small animal ophthalmology?
Schirmer tear test readings are often compared over time to assess deterioration or response to treatment, so any technique-related differences in results are important to address
The Schirmer tear test is a common test in small animal practice and is often undertaken by general practitioners as well as by veterinary ophthalmologists. STT readings are often compared over time to assess deterioration or response to treatment, so any technique-related differences in results are important to address.
Key takeaways for vets
- Closed eyelids significantly decreased the likelihood of the STT strip being dislodged and having to be replaced
- Closed eyelids significantly increased the STT readings, so vets should be consistent with their STT technique to ensure repeatability. If other vets are likely to see the patient at follow-up appointments, the method used (closed versus open) should be outlined in the notes so that the STT results are comparable
- A survey of the veterinary ophthalmology community showed that 34.6 percent of vets didn’t pay attention to whether their STT tests were open or closed, suggesting technique-based differences in results may be a common problem with this test
You can read the full paper here.
Conclusion
Like all areas of veterinary medicine, the world of small animal ophthalmology is constantly evolving thanks to the hard work of researchers. If you enjoyed catching up with the latest in small animal ophthalmology, you might be interested in taking a veterinary ophthalmology certificate. Our teaching programme for the PgC in Ophthalmology is available as a 14-module course online (starting in September).
