Optical coherence tomography sees new opportunities

January 1, 2010

In the realm of posterior vitreous detachment, optical coherence tomography provides a never-before-seen clinical view.

Dr. Jones, who presented on vitreo-macular, vitreo-retinal, and vitreo-disc traction at the 2009 International Vision Expo West, Las Vegas, said that, in the realm of posterior vitreous detachment (PVD), OCT provides a never-before-seen clinical view.

Vitreal traction on the posterior inner wall surface of the globe is primarily attributable to the slow development of PVD, which is crucial in one's understanding of how vitreal traction causes many intraocular complications (partial to total PVD).

PVD and vitreous traction

The vitreous commonly separates from the inner eye wall in people who are 55 and older, or as the result of trauma. The resulting PVD is associated with vitreous traction on the retina and formation of a large reservoir of fluid in the vitreous cavity, both of which are closely related to retinal tear and detachment formation.

"Vitreal traction is best seen with OCT and, to a lesser degree, with ultrasonography," Dr. Jones said.

Floaters are the most common symptom of PVD; others include photopsia, blurred vision, glare, and rarely, metamorphopsia. Dr. Jones cited a study by Hikichi and colleagues of 902 consecutive symptomatic eyes in which 342 had floaters only; PVD was found in 40% of the eyes, as compared to 20% in a control group.

"Among patients over 50 years of age, sudden onset of floaters is associated with a PVD in 95% of the cases," he said.

Retinal, preretinal, disc, and vitreous hemorrhages commonly occur after PVD. This is either the result of rupturing a superficial blood vessel or shearing a vessel during the formation of a retinal tear.

"It is very important for patients who are having a PVD to have an OCT evaluation to see if there is any residual traction to the macular area. It is just as important to scan the fellow eye, for it is going through the same process of vitreous separation but may be weeks to months behind in forming the total PVD in most cases," he said.

Retinal tears, detachments

Retinal tears and detachments are other sequelae of PVD.

Generally, retinal tears occur between the equator and ora serrata. Because the retina is so thin there, that traction can cause a full thickness retinal tear. While most retinal tears secondary to PVD are discovered at the initial examination, breaks might not appear for 2 weeks to 10 years after initial symptoms.

Retinal detachments, usually rhegmatogenous in nature, are a natural aftermath of retinal tear formation in patients with PVD, he said.

Vitreous traction can produce edema of the macula, which can be due to pulling on the surface of the retina. The traction may lead to spaces being produced in the retina that are naturally filled with fluid, according to Dr. Jones.

"The edema may disappear if vitreoretinal adhesions are broken, but if the traction exists for a prolonged period of time, they may become long-standing in nature," he said.

The traction can lead to a break in the internal limiting membrane. This, in turn, can result in retinal and glial cells migrating onto the surface of the retina and forming a membrane, which has the ability to contract, producing wrinkling which may result in metamorphopsia and decreased vision, he said.

Optometrists might see macular hole formation, a consequence of PVD, without OCT but in many cases (especially in partial macular holes), OCT can make detection much easier, Dr. Jones said.

"Years ago, many called macular holes 'senile idiopathic macular holes' because of their unknown cause. Now, we know that the vast majority are caused by vitreal traction," he said.

Follow up

It is best to see patients who complain of recent onset of visual floaters or light flashes within 1 to 2 days, according to Dr. Jones.

"I then follow up with them every 2 weeks, up to 6 weeks," he said. "According to the literature, the danger period for PVD is considered 6 weeks-especially the first 2 weeks. If there is persistent traction on the macular area seen on OCT, we follow patients until the traction is gone. Next, I talk to the patient about the 6-month follow-up, for it is known that if there are no problems after this period of time, problems are not likely to occur following a total PVD."

While there is no way known to prevent the occurrence of PVD, optometrists can stay on top of the condition by using OCT to evaluate patients' macula and disc areas for vitreal traction and possible PVD development.

"Vitreal traction occurs years before you have a full-blown PVD," Dr. Jones said.