High blood pressure (hypertension) can damage small blood vessels in the eye, leading to hypertensive retinopathy – swelling of the optic disk and blurred vision as a result.

Eye doctors can detect glaucoma using an instrument known as a tonometer to measure eye pressure, with dilation of your pupils necessary to achieve accurate readings.

Tonometry

Tonometry allows your physician to measure the intraocular pressure (IOP). This test helps your physician assess your risk for glaucoma, which damages optic nerves and leads to vision loss. If this risk exists in you, eye drops could be prescribed by your physician in order to lower IOP and reduce it and thus protect vision loss.

To administer this test, your doctor will administer eye drops to numb the surface of your corneas and have you sit before an instrument called a Phoroptor that looks similar to a large mask with holes for your eyes and has multiple lenses which they can switch. Your doctor will ask you to read letters on a chart located approximately 20 feet away, before adjusting the lenses until all rows of letters can be seen clearly.

There are various tonometers used to measure intraocular pressure (IOP). While some require eye drops for numbing purposes, others do not. Of all of them, the Goldman applanation tonometer is considered the most accurate; it attaches directly to most doctors’ offices’ slit lamp biomicroscope and measures force required to flatten a small section of cornea; its output corresponds with normal IOP readings.

Rebound tonometers are another popular way of gauging IOP without needing eye drops; their plastic-tipped probe bounces softly against the cornea’s surface before reporting its measurements based on motion parameters. Being lightweight and portable makes this type of tonometer ideal for home and office use alike.

Other nonnumbing methods that do not require eye drops to measure IOP include the airpuff noncontact tonometer, which uses air puffs to measure IOP; and electronic indentation tonometer, which employs contact lens-assisted indentation force application on cornea. If this method proves unsuccessful due to scratched cornea, additional testing such as pachymetry will need to be conducted before repeating tonometry tests can take place.

Refraction

Refraction refers to the bending of electromagnetic radiation such as visible light, radio waves or ultraviolet rays between two mediums with different densities, at an interface. Refraction occurs because light travels faster in one medium compared to another; for instance if light passes from water into air it will bend; this optical effect is known as Snell’s Law.

An integral component of every eye exam is a refraction test to establish your prescription for corrective lenses (nearsightedness, farsightedness and astigmatism). You’ll sit in front of equipment called a Phoroptor that looks similar to a large mask with holes for your eyes; an eye doctor will ask you to read out loud the smallest row of letters that you can see on a chart in front of you and read back that information from memory.

Your eye doctor will use a handheld lighted instrument called a retinoscope to assess how effectively your eyes focus light, taking about five minutes per eye. Based on its results, additional testing may be necessary depending on this evaluation.

Refraction tests can also help detect certain conditions, including glaucoma. Glaucoma is an eye disease that can lead to blindness if left untreated, but early diagnosis and treatment can often save vision and save lives. As there are usually no symptoms for glaucoma until too late, scheduling regular eye exams with your O’Brien Vision Center could save both vision and life! Be proactive; schedule one today – you won’t regret it!

Gonioscopy

Gonioscopy is an eye exam that analyzes the drainage angle between your iris and cornea to diagnose open-angle or closed-angle glaucoma as well as congenital defects or scars that may contribute to its cause. The test typically takes only minutes in a doctor’s office. Once your eyes have been numbed with drops to numb them further, your doctor will use a goniolens to illuminate the surrounding area before using either a slit lamp or microscope to get a clear view of your drainage angle surface.

The drainage angle is where fluid drains from your eye. If it doesn’t function properly, high eye pressure may result in high eye pressure inside your eyeball. To assess this area of drainage properly, an eye examination must focus on testing your iridocorneal angle; which connects your iris to cornea and indicates whether its flow has been blocked by obstruction or not – an indicator that might suggest you may have glaucoma.

Normal eye drainage channels allow fluid produced within your eye (aqueous humor) to drain away properly, but if they’re not, more fluid could build up inside, leading to increased eye pressure or glaucoma. Your Iridocorneal angle may be evaluated using either gonioscopy lens or anterior segment optical coherence tomography (AS-OCT).

There are various types of gonioscopy lenses. Each lens differs in terms of number and angulation of mirrors, which affect their ability to identify an angle clearly. Some lenses feature one mirror while others feature more than three. Some also come equipped with an angled surface – an important consideration when performing indirect gonioscopy.

This study’s goal was to compare the results of gonioscopy with AS-OCT among US and Chinese patients with either ocular hypertension or open-angle glaucoma. They evaluated iridocorneal angles using both Shaffer gonioscopy and indirect gonioscopy; measurements were made at both baseline and four years of follow-up assessment. Researchers determined that standard Shaffer gonioscopy can detect angle closure in one quarter of cornea, but indirect gonioscopy provides less reliable results due to difficulty visualizing this angle in cases such as those phakic eyes or sector iridectomies.

Slit Lamp Examination

At an eye test, a doctor uses a special lamp and microscope to inspect the front of your eyes. He or she will administer drops to widen (dilate) them so he or she can see structures such as your iris, cornea, lens and retina under magnification using a slit lamp.

A slit lamp can also help assess how well your eyes are functioning by examining how the iris and lens function, as well as detect cataracts – clouding of lenses that cloud over over time – which should be treated early through regular visits to an eye doctor. Furthermore, slit lamps are capable of detecting glaucoma caused by high eye pressure that damages optic nerves if left untreated.

Tonometry, or tonometery, is another painless part of a slit lamp exam which measures the fluid pressure in your eye. A doctor will place yellow drops into your eye before resting a probe-shaped instrument on each front corner to assess pressure. There are various tonometer methods but one of the most popular approaches is called Goldmann applanation tonometry which uses numbing drops with a device resembling a pen with its tip touching your cornea’s front surface – instantly recording pressure measurements! Alternatively, doctors may use noncontact tonometers known as air puff tonometers (often called air puff tonometer).

Slit lamp examinations can detect many other diseases and health conditions. If you have diabetes, a doctor will check for diabetic retinopathy – a complication which can lead to vision loss – while for heart disease patients this exam checks for glaucomatous neuropathy caused by decreased blood flow to your eyes. Finally, they’ll inspect eye color patterns in order to detect abnormalities which could indicate cardiovascular disease or other illnesses.