testeyesight.org

Introduction

Optometrists and ophthalmologists have made invaluable contributions to public health. Through comprehensive exams and the prescription of corrective lenses, they help millions achieve improved vision and early detection of disease.

Although the current system has produced strong results, there is still room to improve the precision of astigmatism correction.

The Problem

Current refraction methods often involve iterative adjustments to both sphere and cylinder values. However, changes in cylinder strength inherently affect the spherical component (e.g., a +0.50 cylinder shift typically causes a +0.25 sphere shift). When the cylinder is adjusted, optometrists must assess whether the sphere also needs to change.

In theory, any resulting imperfection should be small. In actual practice, however, it does not work that way--even when procedures are followed precisely.

Sometimes, the cylinder is adjusted when the real issue lies in the sphere. The final prescription--unknown even to the most skilled optometrists--may fall within a range of sphere and cylinder combinations. Multiple tests can yield consistent yet inaccurate results.

What is needed is a way to test eyesight that maintains an accurate sphere as much as possible, while also achieving highly accurate astigmatism measurements that are not influenced by or intermingled with the sphere. There are two ways to do this, which I will explain later.

The eye is physically incapable of making focusing adjustments to correct for inaccurate astigmatism. It can only adjust for an imprecise sphere. When astigmatism correction is off, the eye attempts to compensate by altering spherical focus.

When astigmatism is corrected accurately, children and young adults require fewer prescription updates. The eye is free to concentrate on adjusting for sphere alone.

In older adults and senior citizens, even a small amount of remaining accommodation can be better utilized to focus at varying distances. Remarkably, even patients with no accommodation ability at all can benefit from sharper vision across different distances when astigmatism correction is precise.

Inaccurate prescriptions may go unnoticed during the day, but at night, when the pupil dilates, imperfections become more apparent. Accurate correction improves night vision--and therefore, driving safety. Accurate astigmatism correction plays a crucial role.

With accurate astigmatism correction and progressive lenses, patients require less head movement to find the right focal zone.

What optometrists need is a way to measure astigmatism more accurately--one that preserves spherical accuracy while isolating astigmatism measurements from spherical interference.

There are two ways to accomplish this objective.

One approach involves the use of EyeQue. While EyeQue does not claim to improve the accuracy of astigmatism measurement, it often can. However, it is not suitable for clinical use by optometrists. There is a different approach to testing vision--one that achieves superior results.

The procedure is straightforward and quick to learn, and once understood, it allows for efficient and accurate vision testing. While it differs from standard refraction techniques, it can be used effectively with minimal training.

This approach to testing eyesight is not designed for use with a phoropter. Instead, it requires:

   A lens set kit

   A trial frame

   A ±0.25 Jackson Cross Cylinder (occasionally a ±0.50)

The optometrist must be able to identify the red and silver etched lines on the Jackson Cross Cylinder.

This interactive guide to testing eyesight is not found on our web site, testeyesight.org, but it is found on refractionsteps.org

There is one imperfection with refractionsteps.org. There are two places in the interactive guide where some math is required and an optical calculator would be helpful. Since refractionsteps.org has not provided the optical calculator, testeyesight.org has stepped in to help.