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Equine Lens Problems
Equine Ophthalmology Service
University of Florida
Capsule
Cortex Nucleus
•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
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
Criteria healthy foals
(Rhodococcus free) and
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
Trauma from cross ties
Aphakic crescent
X
4 wks later
Lens subluxation
Lens Cysts