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The Ophthalmic Refractometer - Vision Matters?

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You may have been to the eye doctor's office and felt like they were speaking an entirely different language. For example, one of the phrases might include words such as "ophthalmic refractometer."

It makes you wonder what on earth these doctors are referring to when giving out prescriptions?

What is a Refractometer?

The refractometer is used to identify vision errors and determine if you need new, stronger prescription lenses for clearer sight.

It can also be used as an early warning system for conditions such as myopia or hyperopia, which leads to vision loss from restricted incoming light rays on the retina at different distances.

Myopia and hyperopia can be seen in many ways. One way to show the severity will be with a refractometer, which measures diopter correction if you are nearsighted (indicated by – sign) or farsighted (plus +). It also tells us how much power our lenses need for that level, knowing what type best fits.

Astigmatism is the most common type of vision problem in humans. A recent study found that up to 20% of men and 10-30% of women suffer from this condition. Astigmatic people have slightly curved eyes, unlike those without astigmatisms whose eyes may be perfectly round like a ball.

The refractometer will identify your level and what axis (or angle) it falls under so the doctor can decide how severe this condition is before recommending some corrective eyewear options.

Pupillary Distance (PD) is the distance between your pupils. It ensures that you are getting proper fit glasses by determining whether they will be aligned to match up properly against both of them. This ensures no misalignment occurs when looking through lenses, which can lead to an issue in seeing clearly without any corrective action.

You can measure your pupillary distance at home with a PD ruler or, even better, using an innovative tool like EyeQue. The EyeQue Personal Vision Tracker (PVT) is an ophthalmic refractometer you can use to determine exactly how far your pupils are in front of the screen so that glasses will be appropriately aligned for optimal vision correction without any hassle. More on that later.

How a Refractometer Works

When light enters the water, it changes direction, and this is how refraction works. So a refractometer measures angles of reflection on the concentration's nD values that have been established.

Using this information, you can determine concentrations within solutions. Different indexes are present depending upon what they're mixed in with, like alcohols having higher numbers due to their lower index than gases, which would be considered 0%.


A refractometer is used to measure the concentration of substances in solutions. It operates on light, so its readings are always precise and accurate, with no outliers or errors.

The angle of refraction is related to a value called the 'index' or degree that bends light. Different compounds have different indices, which determine how much they bend (refract) incoming rays of solar energy and cause them to diverge outwards into space with increasing degrees at higher concentrations. It's also important for determining testing environments since the temperature has its own effect on angles.

The use of refractive light to determine salt concentrations is an example that is used in several industries. For example, when preparing products such as brines or sauces, the ratio between sodium chloride (NaCl) concentration and other ingredients must remain constant for quality control purposes.

For instance: A ship carrying bottled water from a pristine mountain spring may have been contaminated by seawater while traveling through rough seas; this would cause its salinity levels ​​to rise gradually over time until they reach around 35%.

Refractometers give readings that are based on how light interacts with different substances. There's an analog type, which retains its accuracy better than the digital version because it doesn't rely so much on electronics. There is also a refractometer for laboratories called Abbe (Laboratory) Refractor Meters that requires more precise measurements due to high precision glassware used in research settings, but these instruments have been around since 1876.

What Is the Difference Between an Analog and a Digital Refractometer?

Analog Refractometers measure color changes in solutions, while Digital ones use a drop of solution to illuminate their light source. This creates two types: handheld (with cover plate) or benchtop models placed on top for stability reasons to avoid shaking during readings. These are known as Abbe type laboratories too.

Refractometers are an essential tool for any scientist who wants to analyze the density of their samples, but they can be difficult and tedious instruments. The handheld analog refractor requires you to place your sample on top of a cover plate with prisms (after removing all air bubbles), then hold it up against light so you can view what's inside. This type of device usually has numerical readings to make reading more accessible than interpreting prism colors or patterns that could change depending upon how much moisture was present.

There are various scales that refractometers can measure, including:

  • Salt content (sodium chloride),
  • Brix percentage for quality control in food and beverage industries, 
  • Coolant freezing point effectiveness between ethylene glycol or propylene glycol coolants with this device. 

EyeQue FDA-Registered Ophthalmic Refractometer

This device is the perfect solution for patients with diabetes or other chronic conditions who need to monitor their eye prescription more often. One example my doctor provided was a patient whose health deteriorated after an accident and who needed frequent checkups from an ophthalmologist rather than annually.

EyeQue device is an FDA-registered ophthalmic refractometer that uses the light from a smartphone screen. It can measure your eye and take pictures for you to send in with prescriptions or share online, so it's like having two devices rolled into one.

Buy EyeQue device
Written by Eric Parker

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