How to manage macular development phases

September 1, 2010

Optical coherence tomography is an invaluable tool for diagnosing macular holes in clinical practice, according to one expert.

Orlando, FL-It wasn't until the advent of optical coherence tomography (OCT) that clinicians could prove that vitreous traction was the underlying cause of most cases of idiopathic macular holes. OCT is also invaluable as a diagnostic tool in the clinical practice, said William L. Jones, OD, FAAO, Albuquerque, NM.

"If you have a case where you can't explain the vision loss or some visual distortion or symptomology, or something just looks weird about the macular area, do an OCT," Dr. Jones continued, adding that macular holes may have multiple manifestations.

"If you know there is macular hole formation, follow it," Dr. Jones said, suggesting that the point at which the optometrist makes a referral depends on his or her comfort level with management of macular holes.

The etiology of macular holes includes vitreous traction, tangential traction, trauma, and macular cysts. The overall prevalence of macular holes in the United States is 3.3 cases per 1,000 individuals in the population over 55 years of age. Most cases occur between the ages of 60 and 69-also the time that posterior vitreous detachment is most likely to occur.

"It is not true that everyone will have a posterior vitreous detachment by the age of 80. But if you do get one, it may be problematic," he said. He also noted that macular holes are usually monocular and are more often seen in women, although the reason for this gender discrepancy is unclear.

As Dr. Jones explained, the vitreous is relatively firm through the early years but with aging begins to liquefy and shrink. The early signs of separation may be present in the late 30s or 40s, but are not visible except by OCT and in most cases are benign. As we age, the vitreous pulls on the retina, and this may tear off a piece of the retina or pull the thin fovea depression apart if the vitreous is still firmly attached. When this occurs in the macula, the result is a macular hole.

The Gass classification identifies four stages of macular holes. Stage 1A is an impending hole (yellow spot); in 1B, the yellow spot changes into a doughnut-shaped ring; stage 2 is pseudo-operculum formation; stage 3 is a hole more than 400 μm in diameter; stage 4 is a full-thickness hole with complete separation of the vitreous from the macula and optic disc.

In his practice, Dr. Jones classifies vitreomacular traction syndrome as either vitreofoveal or vitreoparafoveal for greater precision. If the vitreous is pulling on the parafoveal area (thicker retina), the risk is lower than if the traction is occurring in the foveal area.

Patients with impending macular hole formation usually note mild visual blurring and some distortion that may be observed on an Amsler grid. Vision usually stabilizes at about 20/200 for a full-thickness macular hole. However, a patient with a lamellar hole may still have 20/20 vision due to neuro bridges still connecting the foveal outer retinal layer to the retinal nerve fiber layer, Dr. Jones said.

Describing some of the features of macular holes, he stated that the white collar often seen in conjunction with a macular hole may be a localized retinal detachment less than one disc diameter from the edge of the break produced by separation of the sensory retina from the pigment epithelium. The white collar may also be due to a perimacular retinoschisis.

Drusen in the base of the macular hole, known as giant pathologic drusen, are the result of malfunctioning of the retinal pigment epithelium, which is no longer covered by the sensory retina. They are small domes or piles of waste material visible on ophthalmoscopy and OCT. OCT can distinguish drusen from similar-looking white or yellow specks in retina that are areas of sensory retinal degeneration.

Although early-stage macular holes often resolve without complications, holes in the later stages require treatment with vitrectomy. However, once the separation has occurred, it may be permanent. Before performing a vitrectomy, Dr. Jones informs his patients that visual improvement is not guaranteed. "Just because you separate the vitreous cortex from pulling on that area doesn't mean it's all going to go back together nicely," he said.

FYI

William L. Jones, OD, FAAO
Phone: 505/243-4066
E-mail: wjones556654@comcast.net

Dr. Jones has no relevant disclosures.