GLAUCOMA

Glaucoma: group of diseases in which increased IOP (intraocular pressure) in an eye produces optic disc cupping and visual field defects.

Normal IOP: 10-21 mm Hg
- Usually slightly high in the morning and slightly deceased at night.


PRODUCTION OF AQUEOUS HUMOR:
(a) Active Secretion: 80% ultrafiltration & 20% diffusion
(b) Drainage: 90% through the Trabecular pathway & 10% through the Uveo-scleral pathway
(c) Level o episcleral venous pressure


CLASSIFICATION:
A. Developmental aka. Congenital: Children present with BUPTHALMOS (increased corneal diameter)
- Primary
- Rubella
- Secondary to other ocular causes such as aniridia
B. Acquired
1. Open angle
- Primary – chronic open angle
- Secondary
2. Closed angle
- Primary – Acute and Chronic closed angle
- Secondary – Due to trauma, raised episcleral venous pressure, steroid induced, associatd with other ocular disease such as uveitis


TONOMETRY (measurement of tension or pressure, particularly IOP)
1. Goldmann tonometer
2. Schiotz tonometer
3. Perkin’s tonometer
4. Air Puff tonometer
5. Tono pen

EYE EXAM:
1. Check IOP
2. Look for optic disc cupping
3. Test field of vision

GONIOSCOPY (examination of anterior chamber of the eye to demonstrate ocular motility and rotation)
- Done to identify structures in the irideo-corneal angle.
- Use a triple-mirror GONIOLENS to visualize the angle and the periphery of the retina
- Opening of the angle is graded (Grades 0-4)
Grade 0: Closed angle
Grade 1:Narrow angle
Grade 2: Moderately narrow angle
Grade 3: Open angle
Grade 4: Widest angle


OPTIC NERVE HEAD CHANGES SEEN IN GLAUCOMA:
1. Retinal nerve fiber changes
2. Concentric expansion of optic disc cup
3. Localized expansion of optic disc cup (notching at inferior or superior pole)
4. Narrowing of neuro-retinal rim
5. Pallor
6. Splinter hemorrhages on disc margin
7. Deepening of optic cup
8. Nasalization of vessels
Note: Papillomacular area is spared and tunnel vision is preserved!!


PERIMETRY:
Visual field: an island of vision surrounded by a sea of darkness.
Normal visual field:
- Superiorly 50 degrees
- Inferiorly 70 degrees
- Nasally 60 degrees
- Temporally 90 degrees

VISUAL FIELD DEFECTS SEEN IN GLAUCOMA:
1. Arcuate Scotomas
2. Isolated paracentral scotoma
3. Nasal step
4. Temporal wedge
5. Ring scotoma


PRIMARY OPEN ANGLE GLAUCOMA:
1. Adult onseT
2. IOP > 21mm Hg at some point in the course of the disease
3. An open angle of normal appearance
4. Glaucomatous optic nerve damage
5. Visual field defect


RISK FACTORS for the development of glaucoma:
1. Age > 40 years
2. Race (higher incidence in Black people)
3. Family history
4. Diabetes
5. Hypertension
6. Myopia
7. Prolonged use corticosteriods (oral or topical)


SYMPTOMS: Usually symptomless & diagnosed on routine eye examination!!
- Patient with Acute closed angle Glaucoma may present with : photophobia, and painful eye, loss of vision, watering of the eye

SIGNS:
1. Increased IOP
2. Fluctuating IOP
3. Optic disc changes
4. Glaucomatous field change


TREATMENT:
1. Medical :
- Alpha-2 agonists eg. Apraclonidine
- Beta Blockers eg. Timolol, Carteolol
- Carbonic anhydrase inhibitors eg. Brinzolamide, Dorzolamide
- Prostaglandins eg. Latanoprost, Travaprost
- Sympathomimetic and Parasympahtomimetic agents eg. Adrenaline, Pilocarpine

2. Laser cyclophotocoagulation

3. Surgery (has a lot of complications and is therefore the last resort of treatment!)
- Argon Laser trabeculoplasty
- Trabeculectomy (a fistula is created between the angle of the anterior chamber and sub Tenon’s space to allow drainage of the fluid)
- Cryotherapy of ciliary body

Management of TRABECUECTOMY FAILURE:
1. Adjunctive Antimetabolites- such as 5-FU and Mitomycin
2. Artificial drainage shunts
3. Cyclodestructive procedure using Lasers OR Cryotherapy


LOW-TENSION GLAUCOMA:
- Also known as Normotensive Glaucoma
- The intraocular pressure is normal but optic disc cupping and field defects are present


OCULAR HYPERTENSION: IOP > 21 mm Hg but there’s no cupping and visual field defects