Ultrasound biomicroscopy in dogs suggests postoperative ocular hypertension may be associated with ciliary cleft changes related to cataract surgery.

Objective: To determine whether novel pre- and postsurgical ultrasound biomicroscopy (UBM) measurements of the canine ciliary cleft (CC) are associated with postoperative ocular hypertension (POH) following cataract surgery and to explore the relationship between intraocular pressure and CC UBM measurements.

Methods: Following pharmacologic mydriasis, UBM images were obtained from 31 client-owned dogs before elective cataract surgery, immediately postsurgery, and 4 to 6 hours following surgery or while experiencing POH ≥ 25 mm Hg. Presurgery and the pre- to postsurgery change in CC measurements were assessed for association with POH using individual mixed-effects logistic regression models and forward variable selection models. Linear mixed-effects models were used to evaluate the relationship of intraocular pressure to UBM measurements within the same eye across multiple time points.

Results: Presurgical measurements were not predictive of POH development. An increase in pectinate ligament distance and CC area from presurgical baseline to immediate postsurgical measurement was associated with reduced odds of developing POH, while increasing CC length (from apex to mid point on the pectinate ligament) from pre- to postsurgery and immature cataracts was associated with increased odds of POH.

Conclusions: The change in CC morphology following cataract surgery appears more impactful in the development of POH than individual variations in presurgery CC measurements. Several changes in the CC dimensions following surgery appear associated with POH risk.

Clinical relevance: This understanding of a potential mechanism of POH development opens new avenues for researching preventative measures associated with modifying surgical techniques to influence CC morphology following cataract surgery.