Download Equine Lens Problems - University of Florida

Capsule
Cortex
Equine Lens Problems
Equine Ophthalmology Service
University of Florida
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
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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!
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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)
Cataract Patient
Criteria

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
•
•
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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