Glaucoma refers to a group of eye conditions that damage the optic nerve, which transmits visual information from the eye to the brain. This damage often occurs when fluid builds up in the front of the eye, increasing pressure inside the eye (intraocular pressure or IOP). Regular eye examinations are important for early detection, allowing timely intervention to preserve vision and prevent irreversible vision loss.
Preparing for Your Eye Examination
An eye examination typically begins with a discussion of your medical history. This includes current medications, past eye conditions, and any vision symptoms you might be experiencing. Providing this history helps the eye care professional understand your overall health and potential risk factors for glaucoma.
Following this, preliminary checks like visual acuity tests measure how clearly you see. Your eye doctor will then explain the diagnostic process, which may involve dilating eye drops.
These drops temporarily widen your pupils, allowing for a better view of the back of your eye. They can cause temporary blurred vision and increased sensitivity to light for several hours after the examination. It is advisable to arrange for someone to drive you home and bring sunglasses for comfort.
Core Glaucoma Diagnostic Tests
Tonometry
Tonometry measures the pressure inside your eye (intraocular pressure or IOP). One common method is Goldmann applanation tonometry, often considered the gold standard, where a small, flat-tipped probe gently touches the surface of your eye after numbing eye drops are applied. Another method, sometimes referred to as the “air puff test,” directs air at your eye to measure corneal resistance. High IOP is a risk factor, but it does not solely confirm a diagnosis; some individuals with high pressure do not develop optic nerve damage, and others can develop glaucoma with normal pressure.
Ophthalmoscopy
Ophthalmoscopy inspects your optic nerve for signs of damage. During this test, your pupils are typically dilated. The doctor uses an ophthalmoscope to view the back of your eye, looking for specific changes in the optic nerve’s appearance. These include an increase in “cupping” (the indentation in the center of the optic nerve head) or changes in color or shape, which can indicate glaucoma damage.
Perimetry
Perimetry, or a visual field test, assesses your peripheral vision and helps detect any blind spots caused by glaucoma. You sit in front of a dome-shaped instrument and focus on a central point. Small, dim lights flash randomly in your peripheral vision, and you press a button whenever you see a light. This test maps out your field of vision, identifying areas where vision might be diminished or lost due to optic nerve damage.
Gonioscopy
Gonioscopy allows the eye care professional to view the drainage angle of your eye, which is the area where the iris and cornea meet. This angle contains the eye’s drainage system. A special mirrored contact lens is gently placed on your numbed eye, providing a clear, magnified view. This helps determine if the angle is open or closed, which is important for classifying the type of glaucoma.
Pachymetry
Pachymetry measures the thickness of your cornea. A small probe is gently placed on the surface of your numbed eye to take the measurement. Corneal thickness can influence intraocular pressure readings; a thicker cornea might lead to a falsely high IOP reading, while a thinner cornea might result in a falsely low reading. Understanding your corneal thickness helps the eye care professional interpret your IOP measurements more accurately.
Interpreting Test Findings
No single test definitively diagnoses glaucoma; instead, the eye care professional integrates the results from all these diagnostic procedures. The readings from tonometry are considered alongside the detailed observations from ophthalmoscopy regarding the optic nerve’s health. Visual field test results indicate any functional vision loss, complementing the structural information gathered from other tests.
Information from gonioscopy helps classify the type of glaucoma based on the drainage angle’s condition. Pachymetry provides context for the intraocular pressure readings. By synthesizing all these findings with your medical history and risk factors, the eye care professional forms a comprehensive picture of your eye health.
Following the completion of these tests, the eye care professional will discuss the findings with you. They will explain whether the results indicate glaucoma, a risk of developing it, or if your eyes are healthy. This discussion also covers the implications of the findings and outlines the recommended next steps, which may include further monitoring or the initiation of specific treatment options.