Primary and Secondary Glaucoma- What are they?

Glaucoma is a group of conditions that have in common- A chronic progressive optic neuropathy that results in characteristic morphological changes at the optic nerve head and in retinal nerve fiber layer. 

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Mechanism Of action:

There are two theories about Mechanism of Action:

1. Mechanical Theory - Due to increase in intraocular pressure there is Mechanical damage of optic nerve
2. Vascular Theory - Due to Less blood supply

Classification of glaucoma:

• Open angle glaucoma- Primary Open-angle glaucoma.- It is due to blockage of trabecular meshwork
• Angle closure glaucoma- In Closed-angle glaucoma the angle gets obliterated and the aqueous is unable to reach the angle at all. E.g., pupillary block: Lens is touching the iris and due to this aqueous cannot flow and gets collected in posterior chamber and pushes the iris forward and blocks the angle
• Ocular Hypertension
• Normal-Tension Glaucoma (NTG)
• Chronic Glaucoma 
• Absolute glaucoma
• Secondary glaucoma 
• Pigmentary glaucoma
• Lens induced glaucoma
• Congenital glaucoma

Primary Open-Angle Glaucoma

Risk Factor

• High intraocular pressure, Difference of intraocular pressure between two eyes is ≥ 4mmhg
• Age > 40 years
• Positive family history
• Genes responsible for glaucoma
  • Myocillin – MYOC gene
  • Optineurin gene – OPTN gene
  • WDR- 36
• High Myopia (> 6 D)
• Race → More common in blacks
• DM → No increased risk of glaucoma

Pathogenesis

• Any mechanical or vascular cause leads to decrease in axoplasmic flow. It causes compromise in nutrition leading to oxidative injury which causes apoptosis of retinal ganglion cells.
• Thinning of optic nerve leads to  astrocytes/ glial cells Proliferation which causes alteration in extracellular matrix of lamina cribrosa leading to remodeling in optic nerve head and thus causes  cupping of optic disc.
  Lamina cribrosa is a sieve like part of optic disc and sclera

Clinical Feature

• Headache / Eye ache - It is the  Main complaint of the patient.
• Visual acuity is normal in the initial stage.
• Color vision is not affected.

On Examination

3 salient features which are found:

1.  IOP Changes
2.  Fundus Changes : Along with damage of optic nerve, there will be change in optic nerve head
3.  Visual field defect

IOP Changes

• Normal Intraocular pressure is  - 10-21 mmHg
• Normal diurnal variation is 5 mmHg.
• If diurnal variation is 5 -8 mmHg then we can suspect  glaucoma.
• If diurnal variation is ≥8mmHg then it can be diagnosed as glaucoma.
• IOP is more in the morning because of more cortisol levels in the morning.

 Other factors causing short term fluctuations of IOP

•  Max in a prone position. Prone > supine > sitting.
•  Exercise decreases IOP except during head stand.
•  Drinking water increases IOP.
•  General anesthesia decreases IOP except Ketamine
• Steroids increases IOP- Steroid responders:
  • Mild responders: < 6mmHg
  • Moderate responders: 6-15mmHg
  • Severe responders: pressure rises > 15mmHg (avoid steroids in these patients)

Fundus changes;

In fundus changes we observe Cupping of disc. The nerve fiber occupies the Neuro-retinal rim. Cup is considered a non-neuronal area. Normal ratio of the cup and the whole disc is called CD ratio, i.e. ≤ 0.3. If the C:D ratio increases, it is called cupping.

• Area of the cup is increasing i.e., the non neuronal area is increasing. It is remodeling of lamina cribrosa due to proliferation of astrocytes and glial cells. A patient is suspected with glaucoma if the C:D ratio is more than 0.7. Cupping of glaucoma is first vertically oval as in first damage in glaucoma occurs in arcuate fibers

Visual Field Defect

It is a three-dimensional representation of differential light sensitivity i.e., against particular background or luminescence how much luminescence of the target is increased so it is visible to the patient Extent of the visual field. Temporarily, it is 90 to 100 degrees, Inferiorly 70 degrees, nasally 60 degrees, and superiorly 50 degrees. · The extent of your visual field is maximum Temporally and minimum superiorly.

Scotoma - Area of reduced sensitivity or total absence but surrounded by normal area 

Isopter · Line joining the corresponding area of same light sensitivity

Blind Spot

It is a physiological scotoma. Located between 10-to-20-degree isopters. In this the Projection of retina is always crossed. ·Normally the optic disc is nasal to the macula so blind spot is temporarily placed. Blind spot is an absolute scotoma. · Blind spot is a negative scotoma. 

Primary angle closure Glaucoma

Angle is a peripheral space between iris and cornea. This space is occluded the most when the pupil is dilated. Maximum closure of angle occurs in mid dilated pupil.

Risk Factors:

• Small eye: Very common in the nanophthalmos (<20mm of Axial length) or hypermetropia – shallow anterior chamber/narrow angle
• More common in females.
• More prevalent in families, the exact gene is not defined.

Mechanisms:

• With Pupillary Block- For any relative pupillary block means the aqueous cannot flow anteriorly and it gets collected in the posterior chamber. Which results in Iris bombe. 
• Without Pupillary Block (Plateau-iris)-·Plateau iris is an anteriorly rotated ciliary body; any rotation will push the iris anterior and make it flatter. · Peripheral anterior chamber is shallow and the central anterior chamber is deep. · It is caused by a narrowing of the anterior chamber angle induced by insertion of the iris anteriorly on the ciliary body or anterior displacement of the ciliary body, which affects the location of the peripheral iris about the trabecular meshwork (i.e., placing them in apposition).
• Combined mechanism

Ocular Hypertension:

• Increased IOP (No damage in the optic nerve)
• No Fundus findings
• No visual Field effects.

Normal-Tension Glaucoma (NTG)

• In normal tension glaucoma the  IOP is normal. Fundus changes Present
• Visual field defect present. Etiology can be explained by vascular theory of axonal loss.

It can be seen in patients with  Nocturnal Hypotension patient (associated with early morning surge in blood pressure), Sleep Apnoea patient, Migraine patient, Significant positive family history.

Chronic Glaucoma

Clinical Features of chronic glaucoma are:

• Raised IOP.
• Fundus changes present.
• Visual Field defects present

Absolute Glaucoma

It is a painful blind eye.in this we will find 100% cupping. The eye is stony hard as it is not responding to any treatment. All the nerve fibers are damaged.

Secondary Glaucoma

It can be:

A) Open angle glaucoma-it is divided into:

1. Pre trabecular: Causes NVG, ICE syndrome or it could be epithelial ingrowth in the angle.
2. Trabecular: Pigmentary glaucoma, PEX syndrome, Uveitis, Haemorrhage, Phacolytic.
3. Post trabecular: All the causes of increased episcleral venous pressure.
   • Carotico Cavernous Fistulas.
   • Sturge-Weber syndrome (SWS).
   • TED (thyroid eye disease.)

B)Angle Closure glaucoma:

• With pupillary block:
  •  Phacomorphic
  •  Phacotopic : Due to dislocation of lens
  •  Seclusio pupillae.
• Without pupillary block:
  •  ICE syndrome.
  •  PAS in advanced NVG.

Pigmentary Glaucoma:

Secondary open-angle glaucoma known as Pigmentary glaucoma. It  is characterized by severe homogeneous. Trabecular meshwork pigmentation, Iris transillumination defects, and pigment along the corneal endothelium .(krukenberg spindles in cornea). It is  More common in males and young myopes. There is a common history of person coming from gym or heavy workout seen with pigmentary glaucoma. It is the pigment dispersion from iris flowing through aqueous blocking the DM causing the open angle glaucoma Therefore, pigmentary glaucoma also known as reverse glaucoma. If it is concave it will rub against the suspensory ligament which will cause release of pigments. Any pigment dispersion at equatorial area near the zonula insertion is called Scheie/zentamayer's line.

Treatment:

•  Medical therapy with antiglaucoma drugs
• ALT: Argon Laser Trabeculoplasty.
• It is more effective in pigmentary glaucoma

Lens Induced Glaucoma

This can be of 4 types

• Phacolytic glaucoma: It is seen in morgagnian cataracts It is a Secondary open angle glaucoma (SOAG.)
• Phacotoxic glaucoma: It is caused due to trauma and is also known as lens particle glaucoma. It is Secondary open angle glaucoma – SOAG.
• Phacomorphic: It is caused due to intumescent cataracts causing pupillary block (It is Secondary angle-closure glaucoma - SACG).
• Phacoanaphylactic: It is also known as Phacogenic and is caused due to the immune reaction towards the lens protein. It is Secondary open angle glaucoma – SOAG

Congenital Glaucoma

1. PCG : Primary Congenital Glaucoma
2. SCG : Secondary Congenital Glaucoma

Primary Congenital Glaucoma · Primary congenital is generally considered sporadic. · If it is hereditary, it is autosomal recessive.  More common in males than females.

Pathogenesis 

• Trabeculodysgenesis.
• Commonly due to anteriorly located iris insertion

Clinical feature

• Presence of watery eyes
• Photophobia
• Blepharospasm

On examination:

• Buphthalmos leads to large cornea, white cornea, haab's striae Haab's striae later leads to corneal scarring and vascularization.
• Deep Anterior chamber
• Angle anomaly
• Iridodonesis
• Flat lens
• Breaking of suspensory ligaments leads to subluxation of lens
• Cupping of disc.

Conditions of Secondary congenital Glaucoma

• Sturge weber syndrome
  • Hemangioma on the face
  • Hemangioma in the brain
  • Glaucoma

• NF-1
  • Glaucoma is due to angle anomalies.it is Associated with plexiform Neurofibroma (s-shaped lid) · Aniridia
  • Rudimentary frill of iris. occurs due to  Mutation in PAX-6 gene .It May  be associated with Wilms tumor.

Symptoms of glaucoma:

Most people with open-angle glaucoma don't have any symptoms. In the event that symptoms do manifest, they frequently do so at the end of the illness. As a result, glaucoma is often called the "sneak thief of vision." Often, the main symptom is a loss of peripheral vision or side vision.

The signs and symptoms of angle-closure glaucoma often manifest earlier and are more severe. Damage may occur suddenly. If you notice any of these signs, get medical help right away:
viewing the lights that surround the halo,absence of vision
You have a crimson eye. fuzzy-looking eye (particularly in neonates)
nausea or vomiting discomfort in the eyes

Ophthalmology Related articles:

DIAGNOSIS OF GLAUCOMA:

The glaucoma test is quick and painless. Your vision will be evaluated by an eye doctor. pupils will be  (dilated) with drops on inspection.Your optic nerve will be examined for glaucoma symptoms. They might take pictures so they can document changes on your subsequent appointment. To check your eye pressure, a procedure known as tonometry will be performed. To determine if you have lost peripheral vision, they could also perform a visual field exam.Your doctor may request specialized imaging examinations of your optic nerve if they have glaucoma suspicions.If you have undergone refractive surgery, such as LASIK, let your doctor know. The reading of your ocular pressure may be impacted.Eye pressure that is higher than usual does not necessarily indicate glaucoma. In fact, some individuals with normal blood pressureEye pressure that is higher than usual does not necessarily indicate glaucoma. In actuality, some individuals with normal blood pressure may experience it, while those with higher levels may not. Ocular hypertension is high pressure without harm to the visual nerve. Your doctor will want to check your eyes frequently if you have this.

Vogt triad:

A TRIAD OF VOGT IN GLAUCOMA

Post Congestive glaucoma and cases of acute congestive glaucoma that have been treated both exhibit Vogt's triad.

It has the following traits:

• (Anterior subcapsular lenticular opacity) Glaucomflecken
• Iris patches deteriorate
• Sphincter atrophy causes the pupil to be slightly dilated but not react.

Bayoneting sign in glaucoma:

A blood artery may travel beneath the cup's overhanging edge and produce a steep bend when it passes the cup's margin as a result of cupping and excavation in glaucoma. This is referred to as the bayonet vessel sign and results from brain tissue loss that extends past the cup's edge.

• It is so named because the vessel's acute angle resembles the acute angle of a rifle bayonet.
• This arrangement is typical of glaucomatous lesions and is infrequently observed in healthy eyes.
• It is important to distinguish the bayonet vessel from a blood vessel that normally perforates the neuroretinal rim.

Treatment of Glaucoma

There are 3 types of treatments : Medical, Laser and Surgery

Medical: Antiglaucoma drugs which can be either topical or systemic

1. The drugs either decrease the formation of aqueous or increase the drainage to ultimately decrease the IOP.
2. Target IOP: It prevents the progression of visual field defects without compromising the quality of life. This is of two types:
   1. Topical: There are six types of topical drugs:
      1. Beta-blockers: These decrease the formation of aqueous. For example: Timolol, betaxolol, levobunolol, etc. These are contra-indicated in asthma. Nasolacrimal duct obstruction is caused by Timolol. Side effects: Corneal anesthesia and Blepharo conjunctivitis.
      2. Alpha agonists: They have dual action i.e decreasing the aqueous formation and increasing the drainage (uveoscleral outflow). For example - Adrenaline/epinephrine, dipivefrin,brimonidine, and apraclonidine. The last two are selective alpha agonists and can be given to hypertension and heart disease patients. Brimonidine causes drowsiness. Brimonidine is contraindicated in children because it causes sleep apnea and heart blocks in children. Brimonidine can be given in pregnancy. Apraclonidine can cause lid retraction. Adrenaline causes conjunctival pigmentation or deposits. Specific side effect of adrenaline is cystoid macular edema. Adrenaline is C/I in aphakic glaucoma.
      3. Miotics: These increase the trabecular outflow and open the angle blockage. For example - Pilocarpine. Side effects of pilocarpine: It causes spasms of the ciliary muscles leading to pseudo myopia. In severe cases, it can lead to retinal detachment. It also leads to a shallow anterior chamber. It can also cause iris cysts. It increases the capillary permeability leading to uveitis. Thus, it is contraindicated in uveitis.
      4. PGF2ɑ agonists: It increases the uveoscleral outflow. These are also contraindicated in uveitis and asthma.For example - Latanoprost, bimatoprost, travoprost, tafluprost, and unoprostone isopropyl. Latanoprost cause heterochromia iridis (difference of iris color between the 2 eyes ). Bimatoprost can increase both outflows: trabecular outflow and uveoscleral outflow Side effects: hypertrichosis
      5. Topical carbonic anhydrase inhibitors: These decrease the formation of aqueous. For example - Dorzolamide and brinzolamide. These are contraindicated in sulfa allergies.
      6. Newer anti-glaucoma drugs: These are- Netarsudil: This increases the contractile property of the trabecular meshwork, thus increasing the trabecular outflow and it also decreases the aqueous production. It also decreases episcleral venous pressure.This is given as 0.02% once a day. This is a Rho-kinase inhibitor and is available by the name of Rhopressa.
   2. Systemic: These are of 2 types
      1. Carbonic anhydrase inhibitor : For example, acetazolamide and methazolamide. Side effects: These cause tingling and numbness, constipation, renal stress, and a bad metallic taste. Itb is Contraindicated in sulfa allergy.
      2. Hyperosmotic agents: These draw the aqueous out of the eye.  For example: I/V mannitol (CI in heart disease), glycerol (CI in diabetes), isosorbide, and urea.

Laser Treatment for Glaucoma is divided into -

1. Open-angle glaucoma
2. Angle-closure glaucoma

ACG

• Angle-closure glaucoma is a peripheral iridotomy by NdyAG. We should always use prophylactic peripheral iridotomy in the other eye. So it means even if the other eye is not suffering from acute angle closure we have to do peripheral iridotomy on the other eye as well.
• For angle closure, if it is a plateau iris, then peripheral iridotomy is not effective, so in that case, perform laser iridoplasty. They give peripheral burns by using a photocoagulation laser. Iris contract and angle opens.

Open angle glaucoma:

• Blockage in the trabecular meshwork trabeculoplasty using photo coagulative laser increases inter-meshwork distance.
• Management of absolute glaucoma · Cyclophotocoagulation for absolute glaucoma and refractory glaucoma. (like neovascular glaucoma, malignant glaucoma ) · Cyclophotocoagulation can be done either endoscopically or over the sclera i.e. called transscleral.

Management of primary congenital glaucoma

• Goniotomy is a Treatment of choice (Use a lens called a goniolens to see the structure of the front part of the eye.) cut in TM is given. If the cornea is hazy we do trabeculotomy. Here we go through schelmm's canal and cut is given in TM and SC

• Second choice of treatment is Trabeculectomy +Trabeculotomy

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