Equine Lens Problems Nucleus Cortex Equine Ophthalmology Service University of Florida •The Lens Sits in the Patellar Fossa of the Vitreous

Capsule Equine Lens Problems Nucleus Cortex Equine Ophthalmology Service University of Florida •The lens sits in the patellar fossa of the vitreous.

The horse has weak accommodation (< 2.0 D) to maintain a focussed retinal image.

Cataracts

 Post-inflammatory etiologies

??? ERU cataract/synechia

Matt Stevens  Multifocal lens with horizontal pupil  Zones of optical discontinuity

Nuclear cataract Immature cataract

Morgan horse hereditary nuclear cataract nuclear hereditary horse Morgan

Whip injury Therapy for Uveitic Cataracts

 Medical: Oral aspirin might delay cataract formation in a few ERU horses  10 mg/kg q24h

 Surgery: Only chance for vision – Not easy – Client must be educated about the risks and benefits, and must have realistic expectations! Cataract Patient  healthy foals (Rhodococcus free) and Criteria adult horses  no uveitis  visual impairment  the personality to tolerate topical therapy  Brisk PLRs and a dazzle indicate a functional retina.  US (RDs)  ERG (esp Appaloosas)  ERG: Dark adapt 20 minutes ERG Light Stimulus X

US: mature cataract US: posterior lens capsule rupture RD: “seagull” sign Lens fragments lying on retina. “Phaco” Phaco Surgical Procedure

• Paralysis with atracurium • Scleral tunnel w/cautery • CCC • Standard SA needle; 15 mm • Horse needle is 23 mm • Machines • Hylartin-V™ viscoelastic • Mean phaco time: 10:05 minutes (range 4:32 – 15:49)

Medications Postoperatively

 Sulfas systemically for 5 days  Banamine (+/- omeprazole): several weeks  Topical Atropine: 2 weeks  Topical antibiotics: 2 weeks  Topical Prednisolone acetate: 1-3 months  Hospital stay: avg 8 days, range 3-15 days Phacoemulsification.

 Success rate ~ 83-98% initially in horses. – Declines rapidly with time due to capsuler scarring and persistent uveitis – 49% at one month (OSU) – 44% at one year (TAMU) – 39% at 18 months (UF)  Surgery is easiest in foals and yearlings.  Complications: corneal ulcers, persistent corneal edema and ulcers, glaucoma, hyphema, and infectious endophthalmitis – Vision is functional but the aphakic horse should be hyperopic “far-sighted”  The aphakic equine globe is +9.9 D hyperopic (20/1200). – A 25 D IOL = +8.0 D

IOL Intraocular Lenses (IOLs) in Horses

Knotty06 Lens Luxation in Horses

Anterior lens luxation Aphakic crescent

Trauma from cross ties X

4 wks later

Lens subluxation Lens Cysts