Study links upper-eyelid SPL placement to more major complications: full analysis

A new prospective, randomized study in Equine Veterinary Journal gives equine clinicians stronger evidence on where to place subpalpebral lavage systems in horses: the lower eyelid may be the safer choice when either location is feasible. In 73 SPL systems placed in 68 horses at the University of Liverpool's Philip Leverhulme Equine Hospital, major complications were significantly more common with upper-eyelid placement than with lower-eyelid placement, even though total complication rates were similar between groups. (pmc.ncbi.nlm.nih.gov)

That matters because SPL systems are a core tool in equine ophthalmology, used to deliver frequent topical medications while reducing stress for the horse and improving safety for handlers and clinicians. But despite how common the technique is, evidence on the best placement site has been thin. A 2019 critically appraised topic by Harry Carslake, one of the current study authors, found that both upper- and lower-lid sites appeared acceptable, but the available evidence was limited, heavily retrospective, and not strong enough to support a firm recommendation. (aaep.org)

The new trial enrolled horses treated with SPL systems from February 2015 through January 2024 when the ocular condition did not require a specific insertion site. Placement was determined by coin toss, creating a prospective randomized comparison between central upper-eyelid and medial lower-eyelid systems. The study included 38 upper-lid and 35 lower-lid systems, with a median duration in place of 13 days. Major complications were defined as displacement of the footplate from the fornix, with or without corneal ulceration, loss of the footplate, or eyelid infection and abscess formation. Minor complications included issues such as loss of suture or tape, palpebral swelling, leakage, tube rupture, loss of the injection port, or subcutaneous swelling at a suture site. (pmc.ncbi.nlm.nih.gov)

The topline result was nuanced. Overall complication rates did not differ significantly between locations, but upper-eyelid systems carried a clearly higher rate of major complications, 14% compared with 3% for lower-eyelid systems. Conference material tied to the same Liverpool work, covering an earlier 2015-2023 dataset, pointed in the same direction and listed eyelid infection and abscess formation among the major events seen. The University of Liverpool team also deposited the underlying dataset in December 2024, adding transparency around the cases studied. (pmc.ncbi.nlm.nih.gov)

The findings also fit with a broader trend in the literature. Earlier retrospective reports have been mixed, but some have suggested practical advantages for lower-lid placement. The 2019 evidence review noted lower rates and severity of complications in one lower-lid series compared with an older upper-lid series, while also cautioning that differences in populations and devices limited direct comparison. Another retrospective study surfaced in search results reported that its team favored the lower fornix because placement and removal were easier and complications were less frequent in that hospital setting. (aaep.org)

Why it matters: For veterinarians, this study may influence standard operating choices in referral hospitals, ambulatory ophthalmology cases, and training settings. If disease location, concurrent pathology, or horse tolerance doesn't dictate the site, lower-eyelid placement now has prospective randomized support as a way to reduce the risk of the complications clinicians most want to avoid. That doesn't mean upper-lid placement should disappear; SPL location is still case-dependent, and the authors noted that treatment type and location both influenced complication occurrence. But it does mean clinicians have better evidence to discuss risk, technique selection, and monitoring plans with pet parents and care teams. (pmc.ncbi.nlm.nih.gov)

The paper also highlights a familiar challenge in equine ophthalmology: even when total complication rates are similar, not all complications carry the same clinical weight. A minor issue like tape loss or leakage is very different from footplate displacement with corneal injury or an eyelid abscess that forces early removal. For practices reviewing protocols, the distinction between "any complication" and "major complication" may be the most actionable takeaway from this study. (pmc.ncbi.nlm.nih.gov)

What to watch: The next step will be whether this evidence changes hospital protocols, teaching recommendations, and future guideline-style reviews, and whether follow-up studies clarify how treatment type, tubing management, or medication characteristics interact with eyelid location to shape complication risk. (pmc.ncbi.nlm.nih.gov)