Veterinarians got it right in the 1990s, when they developed an alternative to toppled stepstools, dropped eye ointment tubes, and the reduced compliance (read: epic struggles) that can come with medicating horses’ eyes for days or even weeks on end. A subpalpebral lavage (SPL) allowed them to administer drugs to the surface of a horse’s eye with the simple push of a plunger at a distant catheter port on his neck. But even with this handy tool complications can arise, so researchers in the U.K. recently took a closer look—pun intended—at which factors lead to failure of this eye treatment approach.

Gayle Hallowell, MA, VetMB, PhD, CertVA, Dipl. ACVIM, ACVECC, PFHEA, MRCVS, of the University of Nottingham, and colleagues studied 14 years of SPL records from the University of London’s Royal Veterinary College (2000-2013). They examined a variety of data points in each horse, ranging from age and ophthalmic condition to catheter position and clinician experience.

The team collated data from 138 SPL catheters in 135 horses aged 6 days to 30 years old. The most common conditions among these horses were corneal ulcers (37%), squamous cell carcinoma (18%), and uveitis (aka moon blindness, 16%).

The overall mean SPL complication rate among these animals was 15.9%. “These mostly were palpebral cellulitis (a diffuse bacterial infection of the skin and associated tissues) and corneal ulcers,” said Hallowell, who noted that clinician complication rate was lowest for medicine residents (10%), when compared with interns (42%), medicine clinicians (27%), and surgeons (16%)