Tag Archives: Optic Nerve

Diopsys Pattern Electroretinograph Predicts Early Glaucomatous Vision Loss

Pattern Electroretinography (pERG) Gives up to 8 Years of Advanced Warning

Pattern ElectroretinographIncorporating the most advanced technology available in caring for our patients is important to the way we practice at Total Eye Care. The Diopsys® Pattern Electroretinograph is the newest addition to our suite of technology. The Pattern ERG (PERG) measures the signal strength of the retinal information being sent to the optic nerve. Studies show that a 10% decrease in this signal can be detected up to 8 years earlier with a Pattern Electroretinograph than a scanning laser ophthalmoscope.  This technology thus allows for much earlier diagnosis and treatment.

The Pattern Electroretinograph Helps Prevent Vision Loss in Glaucoma

Early detection and treatment of glaucoma is important due to the fact that nerve tissue cannot be regenerated. Twenty years ago, in the absence of a very high intra-ocular pressure, it was a common practice to wait until a visual field defect was present before initiating treatment. There is a significant amount of redundancy in the retinal nerve fibers. Studies have shown a patient must lose approximately 50% of the nerve fibers before visual field loss is detectable. The scanning laser ophthalmoscopes changed all of that allowing us to detect earlier, more subtle changes in the retinal nerve fiber layer. Now patients are treated before visual field defects become apparent.

The Diopsys® Pattern Electroretinograph is the next step in early detection. The PERG will not replace the scanning laser ophthalmoscopes such as the Zeiss Cirrus Optical Coherence Tomographer (OCT) in the diagnosis of glaucoma; however, it gives us another valuable tool in the diagnosis and treatment of glaucoma.

How Does Glaucoma Damage the Eye?

Glaucoma Blindness Theories

We are frequently asked to explain how glaucoma causes blindness. Glaucomatous damage to the eye is caused when the pressure within the eye is greater than the optic nerve can tolerate. How does the pressure cause blindness? The simple answer is we don’t know exactly; however, there are two main theories as to why the damage occurs. Neither theory fully explains how the optic nerve damage occurs in the different types of glaucoma.

The Vascular Theory of Glaucoma

The premise of the vascular theory is that high pressure inside the eye restricts blood flow to the optic nerve causing the optic nerve to slowly die from lack of oxygen and nutrients.

The Mechanical Theory of Glaucoma

Physical glaucoma damage is the underlying hypothesis of the mechanical theory of glaucoma. It is thought that the high pressure damages the optic nerve fibers.

So Which One Is It?

That’s a good question the leading researchers can make a convincing case for both theories and neither theory, by itself, completely explains how glaucoma damages the eye. In reality, both probably play a role in how an eye is damaged by glaucoma.

Stumble It!

Q: If My Blood Pressure is High Does That Mean the Pressure in My Eye is High Too?

A: This is a great question that gets asked a lot. The pressure inside your eye is completely unrelated to your blood pressure. The intra-ocular pressure system and the blood pressure are completely separate systems and fluid is not exchanged between them. Therefore, if you have high blood pressure you won’t necessarily have glaucoma.