Surgical treatment of primary open angle glaucoma Indications

❖ Medical therapy is insufficient.

❖ The patient does not tolerate medical therapy. Reactions include allergy, reduced vision due to narrowing of the pupil, pain, and ciliary spasms, and ptosis.

❖ The patient is not a suitable candidate for medical therapy due to lack of compliance or dexterity in applying eyedrops.

Table 1G.3 Medical treatment of glaucoma

Active ingredients and preparations (examples)

Mode of action

Indications

Side effects

Parasympathomimetic

agents

❖ Direct parasym-

❖ Improve

❖ Primary

❖ Younger pa-

pathomimetic

drainage of

open angle

tients frequent-

agents:

aqueous humor

glaucoma

ly do not

Cholinergic agents

in primary

❖ Acute angle

tolerate the

- Pilocarpine

open angle

closure

temporary

- Carbachol

glaucoma. The

glaucoma

myopia due to

effect is prob

contraction of

- Aceclidine

ably purely

the ciliary

mechanical via

muscle.

contraction of

❖ Miosis with

the ciliary

worsening of

muscle and ten-

the night vision

sion on the

and narrowing

trabecular

of the peri-

meshwork and

pheral field of

scleral spur.

vision.

❖ In acute angle

closure glau-

coma, the

forced narrow-

ing of the pupil

and the extrac-

tion of the iris

from the angle

of the anterior

chamber are

most impor-

tant.

Continued ^

Active ingredients and Mode of action Indications Side effects preparations (examples)

❖ Indirect parasym-

❖ Improve

❖ Primary

Cholinesterase

pathomimetic

drainage. Con

open angle

inhibitors are

agents: cholin-

traction of the

glaucoma

no longer rou-

esterase inhibitors

ciliary muscle

if other

tinely used

- Neostigmine

and sphincter

miotic

today because

pupillae muscle

agents are

of their signifi-

is more pro-

no longer

cant ocular and

nounced than

effective.

systemic side

with other

effects. They

miotic agents.

are only used in

isolated cases

such as when

other medica-

tions fail to

control intra-

ocular pressure.

Direct sympathomi-

❖ Improve

❖ Primary

10-15% of pa-

metic agents

drainage of

open angle

tients develop

- Dipivefrin

aqueous humor

glaucoma

an allergy.

(epinephrine deriva-

and reduce pro-

Paradoxical in-

tive)

duction of

crease in intra-

aqueous hu-

ocular pressure

mor.

occasionally

❖ Used in combi-

occurs.

nation with

Epinephrine de

pilocarpine and

rivatives have

carbonic anhy-

been shown to

drase inhibitors,

cause cystoid

these agents

maculopathy in

also reduce

patients with

intraocular

aphakia.

pressure.

Oxidation prod

ucts of epine-

phrine deriva-

tives form de-

posits in the

conjunctiva

(adrenochrome

deposits) and

can lead to ob-

struction of the

canaliculus (see

Fig. 4.24 h).

Continued ^

Continued ^

Table 10.3 (Continued)

Active ingredients and preparations (examples)

Mode of action

Indications

Side effects

Clonidine:

❖ Reduces

❖ Particularly

❖ Lowers blood

intraocular

suitable for

pressure.

pressure by

young

Should be used

about 20%, pri

patients

only in low con

marily by vaso-

with pri-

centrations

constriction

mary open

(1/16% and

without in

angle glau-

1/8%) because

fluencing the

coma.

the effect on

size of the pupil

intraocular

and accommo-

pressure is the

dation.

same as with

higher concen-

trations but the

side effects are

significantly

less.

Apraclonidine:

❖ Also reduces

❖ Very good

❖ Beware of car

aqueous humor

reduction

diovascular dis-

production.

of intraocu-

ease.

In contrast to

lar pressure

clonidine, this

in decom-

agent does not

pensated

reduce sys-

glaucoma.

temic blood

pressure.

Brimonidine:

❖ Improves

As with apra-

As with apra-

drainage of

clonidine.

clonidine.

aqueous humor

by reducing

episcleral ve-

nous pressure

and reducing

aqueous humor

production by

decreasing cili-

ary body perfu-

sion.

Continued ^

Active ingredients and Mode of action Indications Side effects preparations (examples)

Sympatholytic agents ❖ Direct sympatholytic agents: beta blockers

- Timolol:

- Betaxolol:

- Carteolol:

- Levobunolol:

- Metipranolol:

Indirect sympatholytic agents: Guanethidine:

Reduce pressure by decreasing production of aqueous humor without influencing pupil size and accommodation.

Decrease aqueous humor production.

Primary open angle glaucoma Secondary open angle glaucoma Secondary angle closure glaucoma

Reduce pressure only slightly.

Reduce heart rate and increase bron-chiospasms in asthma patients.

Contraindications: Beta blockers should used with caution in patients with obstructive lung disease, cardiac insufficiency, or cardiac arrhythmia and only after consulting an internist. Absorption from topical application can produce systemic side effects.

Red eyes.

Continued -

260 10 Glaucoma Table 10.3 (Continued)

Active ingredients and Mode of action Indications Side effects preparations (examples)

Prostaglandin ana

❖ Increase

Suitable for

❖ No known sys-

logues:

uveoscleral

all patients

temic side

- Latanoprost:

aqueous humor

with pri

effects.

drainage.

mary open angle glaucoma.

❖ Local changes in the color of the iris in 16%

Adjunctive therapy with beta blockers, epine-phrine derivatives, pilocarpine, and carbonic anhy-drase inhibitors.

of all patients.

Carbonic anhydrase

❖ Reduces

Acute glau-

❖ Prolonged ther

inhibitors:

aqueous humor

coma.

apy causes

- Dorzolamide:

production. The

Surgical

malaise, nau-

enzyme car

procedures

sea, depres-

- Acetazolamide:

bonic anhy

that can

sion, anorexia,

- Dichlorphenamide:

drase con-

increase

weight loss,

tributes to the

intraocular

and decreased

production of

pressure.

libido in

aqueous humor

40-50% of

via active secre-

glaucoma

tion of bicar-

patients.

bonate.

Continued ^

Active ingredients and Mode of action Indications Side effects preparations (examples)

Argon laser trabeculoplasty:

•:• Principle: Laser burns in the trabecular meshwork cause tissue contraction that widens the intervening spaces and improves outflow through the trabecular meshwork.

• Technique: Fifty to 100 focal laser burns are placed in the anterior trabecular meshwork (Fig. 10.15).

• Comment: Laser surgery in the angle of anterior chamber is possible only if the angle is open. The surgery itself is largely painless, may be performed as an outpatient procedure, and involves few possible complications. These may include bleeding from vascular structures near the angle and synechiae between the iris and individual laser burns. Argon laser trabeculoplasty can bring improvement with intraocular pressures up to 30 mm Hg. It decreases intraocular pressure by about 6 - 8 m Hg for about two years. Argon laser trabeculoplasty is only effective in about every second patient. The full effect occurs about four to six weeks postoperatively.

Osmotic agents:

- Mannitol:

- Glycerine:

Decrease • Exclusively intraocular indicated in pressure pre- acute in-sumably by creases of producing an intraocular osmotic pres- pressure sure gradient such as by means of angle clothe hyper- sure glau-osmotic sub- coma due stances re- to its short leased into the duration of bloodstream. action (only This draws a few water from the hours). fluid-filled spaces, especially from the vitreous body and aqueous humor.

262 10 Glaucoma — Argon laser trabeculoplasty.

262 10 Glaucoma — Argon laser trabeculoplasty.

Cyclodiathermy
Fig. 10.15 An argon laser beam is focused on the trabecular meshwork through a gonioscopeand slit lamp. Approximately 100 laser burns are placed in a circle in the trabecular meshwork to improve aqueous humor drainage.

Filtration surgery:

❖ Principle: The aqueous humor is drained through the anterior chamber through a subconjunctival scleral opening, circumventing the trabecular meshwork. Formation of a thin-walled filtration bleb is a sign of sufficient drainage of aqueous humor.

❖ Technique (Fig. 10.16a-c): First a conjunctival flap is raised, which maybe either fornix-based or limbal-based. Then a partial-thickness scleral flap is raised. Access to the anterior chamber is gained via a goniotomy performed with a 1.5 mm trephine at the sclerocorneal junction or via a rectangular trabeculectomy performed with a scalpel and dissecting scissors. A peripheral iridectomy is then performed through this opening. The scleral flap is then loosely closed and covered with conjunctiva.

❖ Comment: A permanent reduction in intraocular pressure is achieved in 80-85% of these operations.

Cyclodialysis:

❖ Principle: The aqueous humor is drained through an opening into the suprachoroidal space.

❖ Technique: A full-thickness scleral incision is made down to the ciliary body 4 mm posterior to the limbus. The sclera is then separated from the

Primary Open Angle Glaucoma

Fig. 10.16 a The trabecular meshwork is excised with dissecting scissors.

b The partial-thickness scleral flap is closed with two sutures.

Fig. 10.16 a The trabecular meshwork is excised with dissecting scissors.

b The partial-thickness scleral flap is closed with two sutures.

c The postoperative photograph shows a prominent bleb beneath the conjunctiva.

ciliary body with a retractor and retracted anteriorly into the anterior chamber. The ciliary body atrophies in the area of the incision, which also helps to decrease the production of aqueous humor.

❖ Comment: This procedure is less common today than it was in the 1980 s. One reason for this is that it is difficult to gauge accurately the atrophy to the ciliary body. Occasionally severe hypotonia of the globe will result, which then requires surgical intervention to close the dialysis opening.

Cycloablation:

❖ Principle: Atrophy is induced in portions of the ciliary body through the intact sclera to reduce intraocular pressure by decreasing the amount of tissue producing aqueous humor.

- Cyclocryotherapy: A cryoprobe is used to freeze the ciliary body at several points through the sclera. This procedure can be repeated if necessary; the interventions have a cumulative effect.

- Cyclodiathermy: This method is similar to cyclocryotherapy except that a diathermy needle is advanced through the sclera into the ciliary body to cauterize it with heat. The procedure may be performed with or without prior dissection of a partial-thickness scleral flap.

- Laser cycloablation induces atrophy in the ciliary body using YAG laser or high-energy diode laser pulses.

- Ultrasound disruption induces atrophy in the ciliary body with high-frequency ultrasound waves. These last two forms of therapy have been developed to induce atrophy more effectively, more accurately, and in more controlled doses, which is less traumatic for the eye.

❖ Comment: All these forms of cycloablation are irreversible and cause permanent hypotonia. Therefore, they represent the last line of treatment options.

Prophylaxis: No prophylactic action can be taken to prevent primary open angle glaucoma.

H Early diagnosis is crucial and can only be made by an ophthalmologist. By the age of 40 at the latest, patients should have their intraocular pressure measured regularly. The ophthalmologist performs regular glaucoma screening examinations of intraocular pressure and pupil. Therefore, the first pair of reading eyeglasses should always be prescribed by an ophthalmologist.

Prognosis: The prognosis depends greatly on the stage at which primary open angle glaucoma is diagnosed. As a general rule, therapy is more effective the earlier it can be initiated.

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