Glaucoma Examination & Tests

Tonometry

Tonometry measures the pressure within your eye (Intraocular pressure – IOP).

The range for normal pressure is 10-21 mm Hg. Most glaucoma cases are diagnosed with pressure exceeding 22 mm Hg. However, some people can have glaucoma at pressures between 12 -22mm Hg. Eye pressure is unique to each person.

Ophthalmoscopy

This diagnostic procedure helps the doctor examine your shape and color of the optic nerve for glaucoma damage.

If your intraocular pressure is not within the normal range or if the optic nerve looks unusual, your doctor may ask you to have one or two more glaucoma exams: perimetry and optical coherence tomography or gonioscopy.

Perimetry

Perimetry is a visual field test that produces a map of your complete field of vision. Visual field testing identifies, locates, and quantifies the extent of field loss. This test will help a doctor determine whether your vision has been affected by glaucoma.

After glaucoma has been diagnosed, visual field tests are usually done one to four times a year to check for any changes in your vision depending on the severity of visual defects. The presence of visual field damage may indicate moderate to advanced disease. Monitoring the visual field is important to determine disease instability.

Gonioscopy

This diagnostic exam helps determine whether the angle where the iris meets the cornea is narrow or closed and blocked (a possible sign of angle-closure ) or wide and open (a possible sign of open-angle).

Pachymetry

Pachymetry is a simple and painless test to measure the thickness of your cornea. Pachymetry can help your diagnosis, because corneal thickness has the potential to influence eye pressure readings. With this measurement, your doctor can better understand your IOP reading and develop a treatment plan that is right for you.

Optic Nerve Image Analyzers

Digital imaging is recommended as a clinical tool to enhance and facilitate the assessment of the optic disc and retinal nerve fibre layer in the management of glaucoma. Imaging your optic nerve over time can help monitor and detect loss of optic nerve fibers.

The devices include confocal scanning laser ophthalmoscopy, optical coherence tomography (OCT), and scanning laser polarimetry.

Corneal Hysteresis (CH) Measurement

Corneal hysteresis is an indication of the biomechanical properties of the cornea. It has consistently shown to be predictive of, or strongly associated with glaucoma progression, making it an indispensable tool in the glaucoma decision making process.

Types of Glaucoma

Open Angle Glaucoma: In this type of glaucoma, the angle between the iris and cornea is wide and open. This type of glaucoma may either be primary, a form most frequently encountered in patients of Caucasian and African ancestry, or secondary to other conditions such as pigment dispersion syndrome, pseudoexfoliation syndrome or traumatic glaucoma.

Most of kinds involve elevated eye pressure. Normal-tension glaucoma (NTG), also known as normal pressure glaucoma, is a form of open angle glaucoma in which damage occurs to the optic nerve without eye pressure exceeding the normal range.

Angle Closure Glaucoma: In this type of glaucoma, the angle between the iris and the cornea comes into contact resulting in a blocked trabecular meshwork. It is more common in patients of Asian ancestry. Angle-Closure Glaucoma is often chronic, like primary open angle glaucoma, but can sometimes be acute, in which case it usually presents as a very painful ocular condition leading to rapid vision loss. Angle-closure glaucoma can be either primary or secondary to other conditions such as uveitis, neovascularisation or iridocorneal endothelial syndrome (ICE).

Congenital (Childhood) Glaucoma: 

This type of glaucoma is the common term used for a glaucoma diagnosed in infancy or early childhood and often runs in the family. 

Treatment and Long-Term Care

The goal of glaucoma therapy is to prevent vision deterioration, and retain useful vision for the remainder of the patient's life, thus preserving the patient's quality of life. The only proven treatment strategies to achieve this goal is lowering high eye pressure with eye-drops, medication, or laser/surgery which can halt or slow down any further vision loss. Surgery is recommended if medications and/or laser don’t yield the desired result, or with an aim to prevent further vision loss or blindness. Surgical options may be favored earlier, wherever equipment and expertise are available.

Medications

Topical medications for lowering intraocular pressure.

Prostaglandins. Medicines in this category include latanoprost (Xalatan), travoprost (Travatan Z), tafluprost (Zioptan), bimatoprost (Lumigan), latanoprostene bunod (Vyzulta) and Monopost latanoprost. This class of drug is prescribed for once-a-day use.

Beta blockers. Examples include timolol (Betimol, Istalol, Timoptic) and betaxolol (Betoptic). This class of drugs can be prescribed for once- or twice-daily use depending on your condition.

Alpha-adrenergic agonists. Including apraclonidine (Iopidine) and brimonidine (Alphagan P, Qoliana). This class of drug is usually prescribed for twice-daily use but sometimes can be prescribed for use three times a day.

Carbonic anhydrase inhibitors. Including dorzolamide (Trusopt) and brinzolamide (Azopt). This class of drug is usually prescribed for twice-daily use but sometimes can be prescribed for use three times a day.

Rho kinase inhibitor. Available as netarsudil (Rhopressa); is prescribed for once-a-day use.

Miotic or cholinergic agents. This class of medicine is usually prescribed to be used up to four times a day. Because of potential side effects and the need for frequent daily use, these medications are not prescribed very often anymore.

Oral medications. Usually a carbonic anhydrase inhibitor, acetazolamide.

Procedures

Open Angle Glaucoma Care:

On the basis of glaucoma severity:

Early to moderate stage — medications, or laser trabeculoplasty, minimally invasive glaucoma surgery (MIGS), trabeculectomy ± mitomycin C or Tube (+ cataract removal and intraocular lens).

End-stage (refractory glaucoma) — medication and/or cyclophotocoagulation (or cryotherapy) and rehabilitation services.

Angle Closure Glaucoma Care:

A treatment of closed angle glaucoma requires medical and surgical intervention to prevent vision loss. The cause of angle closure will determine the clinical care pathway, and as pupil block is the most common cause, laser iridotomy is recommended as the first line treatment for all patients.

Others include: constrict pupil and lower IOP, laser iridotomy (desirable) or surgical iridectomy (laser to fellow eye), surgical option: Lens extraction/IOL + Trabeculectomy + Mitomycin C; laser iridoplasty for closed angle with plateau iris.

Ongoing management of glaucoma is important. A rise in IOP, progressive optic nerve damage, or progressive visual field loss signal the need for additional medical or surgical intervention to prevent sight loss. More frequent follow-up is suggested in the presence of an advanced disease, multiple risk factors, or progression within a short period.

Dr. Si created an electronic method (www.targetiop.com) to help clinicians obtain an estimated range of target intraocular pressure (IOP). She aims to help clinicians focus on the whole situation of the patient in glaucoma practice and educate the patient on the objective of therapy and risk factors. It was designed on the basis of the major worldwide guidelines for glaucoma practice and recent literatures.