Photo of a woman wearing veterinary clothing (Hanna Holmqvist, SLU) shining an eye lamp on a horse standing in a stable aisle.
Photo: Lisa Chröisty, SLU

The Eye’s Fragile Window: Research for rapid and reliable treatment of corneal ulcers in animals

News published:  01/01/2026

The cornea is the eye’s window to the world and its first line of defence. Ingeniously built but highly vulnerable, it requires swift and accurate treatment when injured. Researchers in Sweden are now working to improve treatment of corneal ulcers in our most cherished animal species.

The cornea – a transparent shield between the eye and the world

Much like a car windscreen, the cornea serves two vital purposes: it allows clear vision through its transparent structure, while simultaneously protecting the valuable and delicate tissues behind it. The eye is also assisted by tear fluid, which – like windshield washer fluid – is constantly present and can rinse away debris when visibility is compromised. And of course, there are the eyelids, blinking like windscreen wipers to sweep away dust, eyelashes and other unwanted intruders.

But the transparent window that the cornea forms between the eye and the world only functions as intended as long as it remains intact. In a collision, the windscreen may crack – and what happens then?

Suddenly, everything fragile that was protected behind the glass is exposed, says doctoral student Hanna Holmqvist, and continues: And that is exactly what can happen when the cornea is damaged – which can very quickly become dangerous.

When a small injury becomes a big problem

There are many reasons why corneal wounds and ulcers may occur. In dogs, tear production or tear film quality may be inadequate, failing to keep the cornea sufficiently lubricated and protected against dust, eyelashes and debris entering the eye. In both dogs and cats, a claw during a fight can easily perforate the cornea.

And if you are a horse, the most common cause is external trauma – for example, running into something or rubbing the eye forcefully against an object that presses into and injures it, says Hanna Holmqvist.

And suddenly, the very feature that makes the cornea so effective – its transparency – becomes its greatest weakness.

Collage with several images of a horse being examined by an eye specialist veterinarian.
Photos: Lisa Chröisty, SLU

Smart yet fragile – transparency at a cost

Because the cornea is transparent, it contains no blood vessels.

If there were a network of blood vessels in the cornea, vision would no longer be clear, but obstructed by the fibrous, coloured structures that blood vessels are, Hanna Holmqvist explains.

Elsewhere in the body, the immune system is an extensive and efficient network. Through interconnected blood vessels, white blood cells can be rapidly transported to wherever they are needed. This allows bacteria and other foreign agents to be stopped at the breach that a wound represents, while the healing process begins.

But because the cornea lacks blood vessels, the immune system does not have the same fast and direct access.

Instead, the body has to start building new blood vessels into the cornea so that immune cells can reach the injured area of the eye more effectively.

And that takes time – time that gives infections a significant opportunity to gain a foothold before the body’s defences arrive, says the doctoral student.
Infection or inflammation?
A corneal injury always triggers inflammation. Only when bacteria or other microorganisms colonise the wound and multiply does it become an infection. Inflammation: the body’s own protective response to injury, aiming to limit damage, eliminate the cause, and initiate healing. Infection: occurs when microorganisms such as bacteria, viruses, fungi or parasites enter the body – for example through a wound – and proliferate, potentially causing disease.

Understanding this, it becomes clear why veterinary medicine strives to assist the healing of corneal ulcers – and why this research project was initiated.

Because it is not only about treating quickly, but about treating precisely.  

Photo of a woman wearing veterinary clothing (Hanna Holmqvist, SLU) shining an eye lamp on a horse standing in a stable aisle.
Damage to the cornea creates breaches in the eye’s protective barrier, allowing bacteria to enter. Photo: Lisa Chröisty, SLU

Precise treatments reduce the risk of antibiotic resistance

To prevent bacteria from invading the eye, corneal injuries are treated as soon as they are detected – most often with antibiotics. But treatment must be targeted and appropriate.

Antibiotics are medicines used to treat bacterial infections.
Antibiotic resistance develops when bacteria evolve mechanisms that render antibiotics less effective, or completely ineffective. This is a serious and growing public health problem, both in Sweden and globally.

To avoid contributing to this problem, the research group aims to identify which bacteria most commonly infect corneal ulcers in animals in Sweden. This knowledge will help Swedish veterinarians make informed decisions when treating suspected infections and choose antibiotics with the highest likelihood of targeting only the bacteria actually present in the damaged cornea.

– Treatment of corneal injuries often consists of eye drops, eye drops – and yet more eye drops. So it really matters that you are using the right ones, says Hanna Holmqvist, doctoral student in the project.

One foot in the lab, the other at the clinic

When a deeper or more complicated corneal ulcer is left to heal on its own, the eye gradually forms new blood vessels that grow from the edge of the cornea towards the wound – like fine threads creeping across an otherwise transparent surface

The vessels grow toward the injury at a rate of 1-2 mm per day, explains Hanna Holmqvist, doctoral student in the project.
Photo of a horse's eye with a corneal ulcer.
An equine eye with an infected corneal ulcer between seven and eight o’clock. Red blood vessels can be seen growing from the corneal margin towards the lesion, along with surrounding oedema (fluid accumulation). Photo: Hanna Holmqvist

In the best-case scenario, these blood vessels regress once the injury has healed and the visual field clears again.

But unfortunately, it is not uncommon for the cornea to never fully regain its transparency. After inflammation and neovascularisation, the healed area may remain covered by grey scar tissue that permanently impairs vision, the doctoral student explains. If we, as veterinarians, intervene early with the correct antibiotic treatment, we have a much better chance of reducing inflammation quickly – and thereby minimising long-term damage to the eye.

Research with a clear goal: safer, sharper treatments

Until 2029, Hanna Holmqvist will devote her full working time to this project, aiming to improve the safety and precision of treatments for corneal ulcers in animals.

With a veterinary degree under her belt, she is able to contribute both by assisting at the eye clinic with sampling and patients, and in the lab with examining and analyzing.

But it is important to emphasise that this is a team effort. We are a research group with complementary expertise, all contributing towards the same goal, she says.

Already within the first months of the project, more than 200 samples from horses, dogs, cats and rabbits have been collected – a strong start to the four-year study.

  • Investigate which factors influence the healing of corneal ulcers.
  • Map the bacterial species most commonly associated with infected corneal ulcers in horses, dogs, cats and rabbits in Sweden.
  • Evaluate which types of antibiotic treatment are effective against specific bacterial pathogens, and, based on this knowledge, assess whether current Swedish veterinary treatment guidelines should be revised.

– Although a substantial body of international research already exists, differences in climate, animal breeds, and Sweden’s comparatively strict antibiotic policy mean that international recommendations are not necessarily optimal under Swedish conditions. This may ultimately influence which treatments are most appropriate to use here, explains the doctoral student.

In addition, the research group aims to compare different diagnostic sampling methods, to ensure that test results are consistent regardless of which method is used.

– This includes both sampling with a special type of cotton swab for bacterial culture and sampling with a cytology brush for cellular analysis, Hanna Holmqvist explains, and continues:

– The latter is much faster, as the brush can be examined directly under the microscope. But does it provide the same information as a swab that is cultured in the laboratory, allowing bacteria time to grow to detectable levels? That is what we want to find out.

Collage with several images of a horse being examined by an eye veterinarian.
Photo: Lisa Chröisty, SLU

Take home advice to readers and animal owners: “All eyes need help – and they need it fast”

Key advice from veterinarian and doctoral student Hanna Holmqvist:

  1. The eye is a delicate structure. If something seems wrong, seek medical or veterinary attention immediately – whether it concerns you or your animal.
  2. A wound to the eye is not comparable to a wound elsewhere in the body. Because the cornea lacks blood vessels in order to remain transparent, the body’s immune response is much slower here. If an infection develops, there is a real risk of permanent damage and impaired vision.
Portrait of a woman (Hanna Holmqvist, SLU) standing indoors.
Hanna Holmqvist, PhD student in the project. Photo: Lisa Chröisty, SLU

About the project

  • Officially titled: “Infectious ulcerative keratitis in horses and companion animals in a Swedish context; prevalence of bacteria and fungi, resistance patterns and prognosis of healing”
  • Expected to run during the period 2025-2029
  • Funding bodies include the Horse Research Foundation, The Greater Stockholm Veterinary Care Foundation and the Agria and SKK Research Fund.
  • The doctoral student in the project is Hanna Holmqvist, together with a research group consisting of:
    • Ingrid Hansson, principal supervisor and professor of bacteriology at the Swedish University of Agricultural Sciences (SLU).
    • Lena Ström, veterinarian, European eye specialist, and researcher at SLU.
    • Katarina Nostell, veterinarian and associate professor of internal medicine at SLU.
    • Oskar Nilsson, antibiotics expert and laboratory veterinarian at the Swedish National Veterinary Institute (SVA).
    • Plus two clinically active veterinarians undergoing training to become Swedish eye specialists: Sara Littorin and Kristian Poulsen.

The project can be broadly divided into the following parts:

  1. The project will begin during the first two years with the collection and analysis of samples from horses, dogs, cats, and rabbits.
  2. The latter two years will then be devoted to mapping the collected and analyzed material, focusing on the following questions:
    1. Which bacteria are found in each animal species in Sweden?
    2. Is it possible to identify which types of antibiotics the above bacteria are sensitive to (known as resistance patterns)?
    3. Is it possible to equate different diagnostic methods?

As a complement to the study, the research team will also work to increase understanding of why some corneal ulcers take longer to heal, or do not heal at all.

Photo of a woman wearing veterinary clothing (Hanna Holmqvist, SLU) standing with a bright eye lamp directed at a horse's eye.
The results from this project are expected to provide greater security for veterinarians working clinically in Sweden. “Many veterinarians are contributing to the project by submitting samples, and we aim to give back by providing a better scientific basis on which to make treatment decisions,” says Hanna Holmqvist. Photo: Lisa Chröisty

Contact

  • Hanna Holmqvist, PhD student
    HBIO, Bacteriology, Virology, Food Safety and Veterinary Public Health