Exam 1: Management of Glaucoma

define glaucoma

• a group of disorders which result in an increase in the intraocular pressure of the eyye resulting in damage to the nervous tissue of the eye resulting in vision loss

types of glaucoma

• primary= inherited

• secondary= due to acquired abnormality of the drainage system

• congenital = rare, young animal abnormal developmentv

aqueous humor flow 

• fluid is made in the ciliary body epithelium = aqueous humor 

• must flow around the lens and through the pupil to enter the front compartment of the eye 

  • primarily driven by carbonic anhydrase 

intraocular pressure of the eye 

• inflow = outflow 

• production by the ciliary body epithelium 

• outflow at the iridocorneal angle 

• increased IOP almost ALWAYS due to impaired outflow 

iridocorneal angle

• fluid enters drainage system through pectinate ligament

  • the pectinate ligament becomes fenestrated after birth to allow fluid to flow into the drainage system

two types of primary glaucoma

• angle closure glaucoma, an abnormal angle, goniodysgenesis

• open angle glaucoma

clinical signs of primary glaucoma 

• sudden vision loss 

• pain 

• episcleral injection 

• dilation of the pupil 

• diffuse corneal edema 

primary angle closure galucoma

• most common form of primary glaucoma- sudden onset of clinical signs

• typically vision loss one eye at a time, floow eye generally normal

• history/clinical exam important in differentiating from secondary glaucoma

primary open angle glaucoma

• angle appears open on gonioscopy- material is present on frozen section of the eye, but this material is not visible clinically

• beagles, PBGV primarily affected

• both eyes affected at the same time

• slow progression

markers of a poor prognosis primary glaucoma 

• buphthalmic 

• cupped optic nerve 

• Haab’s striae 

• fixed pupil with no light reflex responses 

how do drugs work for primary galucoma

• increase outflow

• reduce production

• dehydrate vitreous

osmotic agents for primary glaucoma

• used with an intact blood aqueous barrier

• IV mannitol (can be used twce)- ensure no CV, kidney disease or dehydration, withhold water and fluids for 4 hrs, give with a filtered needle

• oral glycerol- may cayse vomiting, contraindicated in diabetics, causes short tern reduction

topical prostaglandin analogues primary glaucoma 

• iatanoprost, travoprost 

• rapid reduction in ocular pressures 

• improve aquous humor outflow 

• apply and if no response within 30 mintes reapply, consider V osmotic 

• may cause inflammation 

  • not effective in cats!

  • always ensure there is no pupil blocage

  • not first line

topical carbonic anhydrase inhibitors primary glaucoma

• dorzolamide, dorzolamide with B- blocker, brinzolamide

• can use hourly until pressures down, then TID as maintenance (not when contain B blockers!!)

• non-inflammatory

• reduce production of aqueous

B-blockers primary glaucoma

• timolol/betaxolol

• reduce blood flow to ciliary body= reduced production of AH

• not a good solo agent for treatment of glaucoma

• most important for treating the fellow eye to delay onset of glaucoma

• minor presure reduction

• cardiopulmonary effects

• typically used twice daily

lens luxation 

• inherited defect of the lens zolules 

• affects terrier breeds and shar pei

• 3-8y/o

• autosomal recessive 

• bilateral disease with asymmetrical presentation 

• may present as an anterior luxation, posterior luxation or subluxation 

manage secondary glaucoma caused by anterior lens luxation

• causes blockage at the pupil

• topical carbonic anhydrase inhibitor

• consider IV mannitol, dilation of the pupil to relieve pressure spike and transcorneal reduction (may increase intraocular pressure)

• DO NOT USE MIOTICS

if luxated lens is still posterior to the iris ???

• deep or asymmetrical anterior chamber

• increasing intraocular pressures

• consider miotic therapy

chronic uveitis causing secondary glaucoma 

• obstruction may occur at the pupil and or angle- synechia (use of atropine with active uveitis reduces risk but ensure IOP is low)

• obstruction of iridocorneal angle- cellular material, inflammatory products, vascularization 

manage crhonic uveitis causing secondary glaucoma

• control inflammation

• carbonic anhydrase inhibitors- monitor for systemic hypokalemia in cats

• B-blockers- bronchoconstriction, bradycardia

gonioimplant 

implant to bypass the faulty drainage system- for visual eyes 

cyclophotocoagulation

• laser the ciliary body to reduce fluid production - diode laser 810nm

• transscleral or endolaser technique

enucleation

• complete removal of the eye

• lids sewn shit

intrascleral prosthesis 

• removal of the intraocular contents 

• implant within the cornea, scleral shell 

• eye remains open, cosmesis 

ciliary body ablation

• injection of gentocin

• long term inflammation

• risks = tumors in cats, kidney damage