- Created: 13-12-21
- Last Login: 13-12-21
Auto refractometer is used to determine an individual's prescription by measuring how light is affected as it reflects through the eyeball. The process is quick and painless for the patient, and the data ensures a baseline to determine the correct eyeglass or contact lens prescription.
What is Autorefractor keratometer?
Autorefractor/keratometers (ARKs) are computerized devices that provide both refractive testing and keratometry measurements. This allows eyecare professionals to determine both a baseline for the patient's prescription as well as the curvature of the cornea for contact lenses.
What is Autorefractometry?
INTRODUCTION S Refractometry is the estimation of refractive error with a machine, called refractometer or optometer. S Automated Refractometers (AutoRefractors) are designed to objectively determine the refractive error & are of various types depending upon the underlying principle they are based on.
How does a refractometer work?
Refractometers measure the degree to which the light changes direction, called the angle of refraction. A refractometer takes the refraction angles and correlates them to refractive index (nD) values that have been established. Measurements are read at the point where the prism and solution meet.
The chart projector is an AC-powered device intended to project an image on a screen for vision testing.
Ophthalmic examination chart projector including a rotatable chart carrying disc and a mask plate which are co-axial with each other. A light source and a projecting lens assembly are provided for projecting one of the charts on the disc and one of the mask openings onto a screen. An index tube is rotatably mounted in the projecting optical path and carrying a colored filter on the inner periphery thereof. Thus, an astigmatic index can be projected on the peripheral portion of the astigmatic examination chart. The chart carrying disc, the mask plate and the astigmatic index tube can be controlled by knobs all provided on the front panel of the projector.
There are important applications for a handheld autorefractor in the clinical setting. A portable but powerful handheld autorefractor such as the SVOne (Smart Vision Labs; Figure 1) can be used in place of a desktop unit if, for instance, the desktop unit malfunctions or needs servicing. The SVOne adds flexibility to the clinic because it is transportable. This can improve patient flow dynamics, taking the testing modality to the patient rather than having the patient leave the exam room to go to a testing station. A handheld autorefractor serves to relieve bottlenecks if a testing station is occupied; it also allows clinicians to carry the technology to satellite offices that may not have the same diagnostic equipment as the main office.
Where a handheld autorefractor such as the SVOne could have its greatest impact, however, is in teleophthalmology settings. In certain rural areas, there are coverage gaps where patients often have to travel great distances to be seen by an eye care provider. Using the SVOne, which is a Hartmann-Shack wavefront sensor affixed to an iPhone, it would not take much to design a protocol to remotely screen patients to detect refractive errors in need of follow-up.
Understanding and caring for a lensmeter
A lensmeter or lensometer is an instrument used to verify the prescription of eyeglasses or spectacles. Many lensmeters can also verify the power of contact lenses with the addition of a special lens support. The values obtained from a lensmeter are the values specified on the patient's eyeglass prescription: sphere, cylinder, axis, add, and in some cases, prism. It is commonly used prior to an eye examination to obtain the last prescription the patient was given, in order to expedite the examination.
In one commonly used type of lensmeter the target seen through the eyepiece consists of a set of three wide lines with wide spacing between them and another set of three narrow lines with smaller spacing between them. These two sets of lines intersect at right angles. The closely spaced lines represent the sphere component of lens power and the thicker, widely spaced lines represent the cylinder power. In the case of a spherical lens, all of the lines of the target will focus at the same time, while in the case of a sphero-cylindrical lens, the lines will focus separately at different power drum readings (see illustration).
In another type of lensmeter, a series of light dots forming a circle is used as a target instead of the two sets of parallel lines described earlier. If a spherical lens is measured, the circle remains a circle and the power drum is adjusted to obtain a sharp image of the dots. For sphero-cylindrical lenses the dots, when focused, will display a sharp ellipse. The major and minor axes of the ellipse can be read on the scale provided in the instrument.
A phoropter is a machine that stores all the range of lenses optometrists use to check your eye's prescription. These are traditionally operated by hand to rotate different lenses into place. An autophoropter is exactly what it sounds like - it automates this process, so that during your eye exam your optometrist will only need to press buttons on a remote control to change to any combination of different lenses. This speeds up the time it takes to work out your prescription leaving more time to thoroughly check the health of your eyes and discuss other aspects of your vision. The autophoropter head can also test a range of near vision aspects to ensure your multifocals and bifocals give you the appropriate focus.
Trial frame refracting for the primary-care optometrist may seem low tech in today's electronic driven world. Aside from its use by low vision specialists like myself, few still utilize it, as the phoropter, and, more recently, the automated phoropter have pretty much taken its place. That said, you should consider reacquainting yourself with trial frame refracting because the aging population (those age 65 and older) is on the rise, increasing the need for this classic technology.
In fact, the aging population comprised 39.6 million of the U.S. population in 2009, according to the Administration on Aging, (U.S. Department of Health & Human Services). Specifically, they represented 12.9% of the U.S. population — roughly one in every eight Americans. This is a growth of 5% from 2000. Further by 2030, about 19%, or 72.1 million, older persons will comprise our country.
Ophthalmoscopy (also called fundoscopy) is a test that lets a doctor see inside the back of the eye, which is called the fundus. The doctor can also see other structures in the eye. He or she uses a magnifying tool called an ophthalmoscope and a light source to see inside the eye. The test is done as part of an eye exam. It may also be done as part of a routine physical exam.
The fundus has a lining of nerve cells called the retina. The retina detects images that pass through the clear, outer covering of the eye, called the cornea. The fundus also contains blood vessels and the optic nerve.
Different Types of Retinoscopes
There are two different types of retinoscopes: the spot retinoscope and streak retinoscope.
History of the Spot Retinoscope
The earliest pioneers created their own mirrors with a slit in the middle to convert the spot into a linear beam. The first electric, self-illuminated retinoscope was developed in 1901 by Wolff. This device included a tiny bulb that directed a spot of light into the eye. Later, different models resulted in the spot being reflected by a plane mirror, or less commonly, a concave mirror.
History of the Streak Retinoscope
The father of the streak retinoscope was Jack C. Copeland. After dropping and damaging the bulb on his Wolff Spot retinoscope, Copeland 'invented' the first variable vergeance streak retinoscope and patented it in 1927. This instrument produced a linear beam that could rotate throughout the ocular medians.
Spot Retinoscope vs Streak Retinoscope
Both types of retinoscopes can be used to perform different retinoscopy techniques. Because astigmatic eyes create a linear fundus reflex, a streak of light or rectangular beam may be more useful in detecting astigmatism — instead of a spot retinoscope.
The streak retinoscope includes both a plano mode and converging mode. For most types of retinoscopy, the streak instrument should be used in plano mode. In contrast, the spot retinoscope only has plano mode, so there's no adjustment needed to perform many of the dynamic retinoscopy techniques.
Whenever the streak retinoscope is in plano made, it's basically a spot with the sides cut off. The streak retinoscope offers less illumination, while the optical phenomenon taking place away from the center of the streak is obscured. It's more difficult to observe subtle changes in the brightness or color or alterations in the cylinder. Simply put, the spot retinoscope may offer more information.
Since the development of the spot and streak retinoscope, innovation has paved the way for stronger, more robust equipment. And Keeler Ophthalmic Instruments has remained on the forefront of innovation. For more than 100 years, Keeler has been manufacturing ophthalmic instruments, and today Keeler offers several world-class ophthalmic instruments to further advance your ability to detect and diagnose conditions of the eye.