# Phacoemulsification Combined with Pars Plana Vitrectomy: Outcome in Horses with Acquired Cataracts Associated with Uveitis

## TL;DR

This study evaluates the effectiveness of a combined surgical procedure in horses with uveitis-related cataracts, finding that while it reduces active uveitis, retinal detachment remains a major cause of blindness.

## Contribution

The study compares surgical techniques with and without posterior capsulorhexis in treating uveitis-associated cataracts in horses.

## Key findings

- More eyes treated without posterior capsulorhexis remained visual compared to those with it.
- Retinal detachment was the sole long-term cause of blindness in treated horses.
- The surgery significantly reduced postoperative active uveitis.

## Abstract

Uveitis in horses is the most common ocular disease and causes blindness and cataracts in horses. The aim of this study was to evaluate vision and complications after phacoemulsification (emulsification and aspiration of the lens cortex/nucleus from the eye) combined with pars plana vitrectomy (removal of vitreous body from the vitreous chamber) in horses with uveitis-associated cataracts. Additionally, the surgical technique with and without posterior capsulorhexis (removal of the posterior lens capsule) during phacoemulsification (PE) was compared. Uveitis-associated cataracts were treated with phacoemulsification combined with pars plana vitrectomy under identical conditions in 12 eyes of 10 horses with posterior capsulorhexis and 20 eyes of 18 horses without posterior capsulorhexis. Horses underwent pre-, postoperative, and follow-up examinations. In the period 12–18 months postoperatively, 3/7 (42.9%) eyes treated without posterior capsulorhexis, and 2/9 (22.2%) eyes treated with posterior capsulorhexis were visual. In the period > 24 months postoperatively, 2/7 (28.6%) eyes treated without posterior capsulorhexis and 1/8 (12.5%) eyes treated with posterior capsulorhexis were visual. In the overall population, a significant decrease in the number of eyes with postoperative active uveitis was observed during follow-up examinations (p < 0.001). A significant increase in the number of eyes that were blind due to retinal detachment was observed in the overall patient population as the examination period progressed (p < 0.001). Retinal detachment was the sole long-term cause of blindness. In horses diagnosed with uveitis-associated cataracts, no persistent active uveitis was observed following the described treatment during the follow-up examinations. However, the proportion of eyes that were blind due to retinal detachment increased. Thus, while the surgery may prevent postsurgical persistent active uveitis and remove lens opacity, the prognosis for a visual outcome is guarded. A superior outcome in postsurgical vision was observed in eyes treated without posterior capsulorhexis.

Background: Cataracts resulting from equine recurrent uveitis (ERU) or other forms of uveitis are usually associated with rapid progression. ERU is the most common ocular disease cause of blindness and cause of cataracts in horses. The necessity for the posterior capsulorhexis (PC) during phacoemulsification (PE) is controversial. This study aimed to evaluate vision and complications after PE combined with pars plana vitrectomy (PPV) in horses with uveitis-associated cataracts and compare the PE technique with and without posterior capsulorhexis. Methods: Thirty-two eyes of 28 horses with uveitis-associated cataracts aged 14 months to 19.6 years were treated with PE-PPV under identical conditions. Twenty-three eyes of 21 horses were affected by an ERU-associated (ERU group), and nine eyes of 7 horses were affected by cataracts related to uveitis with pathogenesis different to ERU (non-ERU group). PE-PPV was performed in 12 eyes of 10 horses (PC group) and 20 eyes of 18 horses without posterior capsulorhexis (NPC group). Follow-up examination was performed at a mean of 1.7 ± 1.8 years postoperatively (range: 1 month–6.4 years). Results: In the period up to 1 month postoperatively, 17/20 (85%) NPC-eyes and 8/12 (67%) PC-eyes (total: 25/32 [78%]) were visual. From 1–6 months postoperatively, 16/20 (80%) NPC-eyes and 7/12 (58.3%) PC-eyes (total: 23/32 [72%]), and from 6–12 months, 7/11 (63.6%) NPC-eyes and 3/8 (37.5%) PC-eyes (total: 10/19 [52.6%]) were visual. From 12–18 months postoperatively, 3/7 (42.9%) NPC-eyes and 2/9 (22.2%) PC-eyes (total: 5/16 [31.3%]), and from 18–24 months, 3/8 (37.5%) NPC-eyes and 1/8 (12.5%) PC-eyes (total: 4/16 [25%]) were visual. After 24 months postoperatively, 2/7 (28.6%) NPC-eyes and 1/8 (12.5%) PC-eyes (total: 3/15 [20%]) were visual. Despite the higher number of visual eyes in the NPC group at each time point, differences were not significant. No obvious differences regarding postsurgical vision were observed between the ERU- and non-ERU groups at each time point. In the overall population, a significant decrease in the number of eyes with postoperative active uveitis was observed during the follow-up examinations (p < 0.001). A significant increase in the number of eyes that were blind due to retinal detachment was observed in the overall patient population as the examination period progressed (p < 0.001). Retinal detachment was the sole long-term cause of blindness. Conclusions: In horses diagnosed with uveitis-associated cataracts and treated with PE-PPV, no persistent active uveitis was observed in the present study during follow-up examinations. However, the proportion of eyes that were blind due to retinal detachment increased. Whilst PE-PPV may prevent postsurgical persistent active uveitis and remove lens opacity, the prognosis for a visual outcome is guarded. A superior outcome in postsurgical vision was observed in the NPC group. However, caution is required when interpreting these results due to several factors that affect the independent comparison of the surgical groups.