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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