OD News Articles

19th September 2019

Diagnosing Vitreomocular Disorders with OCT

by Michael Van Brocklin, OD Tacoma, WA

As age takes its toll on the vitreous, posterior vitreous detachments, retinal tears, and retinal detachments become more common. Vitreomacular interface (VMI) disorders can also present about the same time that cataracts are beginning to cause visual symptoms. As our patients get older, the detection, diagnosis, treatment planning (including OCT imaging) and education are all critical in providing exceptional care.



VITREOUS STRUCTURE

The vitreous structure is a translucent gel consisting of 98% water. It includes fibrils of macromolecules, glycosaminoglycans, and collagen. The fibrils are arranged in an anterior-to-posterior configuration which allows light to pass through the vitreous with minimal scattering. The posterior cortex (posterior hyaloid) is a layered membrane adhered to the internal limiting membrane (ILM) of the retina. Vitreous attachments are strongest at the vitreous base of the peripheral retina, optic disc, macula, and retinal blood vessels.

THE IMPACT OF AGE

Vitreous gel liquefaction (synerysis) occurs with age, creating pockets of fluid that grow in number and size. This is a lifelong process that begins in young children. By age 20, there is 20% liquefaction that progresses to 50% by age 70. Aging also leads to separation of the posterior vitreous cortex interface from the internal limiting membrane of the retina. And weakened adhesion increases the likelihood of this happening.

POSTERIOR VITREOUS DETACHMENT

Posterior vitreous detachment (PVD) happens when large areas of liquefaction and weakened vitreoretinal interface collapse. Usually, the entire posterior vitreous cortex pulls away from the ILM. As the posterior vitreous collapses, vitreous fibrils become disoriented, resulting in increased light scatter, glare and floaters.

The vast majority of PVD cases happen without retinal complications, and can also occur without symptoms. PVD typically occurs after age 60. People with high degrees of myopia or retinal disease, or those who have recently had intra-ocular surgery, are at higher risk.

A small percentage of PVD cases occur when liquification exceeds vitreoretinal dehiscence—often referred to as an anomalous PVD. Incomplete vitreoretinal separation may result in local retinal traction or splitting of the posterior vitreous cortex (vitreoschisis). When this process occurs at the macula, it is termed vitreomacular traction. If the posterior hyaloid splits instead of releasing, some lamellae of the posterior cortex will remain on the retinal surface. The release of hyalocytes along the retinal surface can lead to cell proliferation, migration, avascular membrane formation, or epiretinal membrane.

DIAGNOSIS AND TREATMENT

Diagnosis and treatment of VMI diseases have been greatly enhanced by optical coherence tomography (OCT). This technology provides a repeatable, easy-to-access cross-sectional view of the posterior vitreous and macular structure. Before OCT, biomicroscopic classification of macular traction and hole formation was the clinic standard.

OCT-BASED CLASSIFICATION

Several years ago an international panel of vitreoretinal specialists developed a system to classify and stage diseases of the vitreomacular interface. This classification is largely based on OCT appearance and supports systematic diagnosis and management that is predictive of therapeutic outcomes.

The following definitions can be helpful to primary care optometric physicians in the assessment, monitoring, and referral of patients:

Vitreomacular adhesion (VMA) – is an OCT finding in an asymptomatic patient with no clinical findings showing parafoveal PVD with attachment near or at the fovea. No abnormal foveal architectural findings are present, and no treatment is needed. VMA does not usually progress to macular traction or distortion.

Vitreomacular traction (VMT) – is when the posterior hyaloid of the vitreous is adherent to the macula with macular distortion. An exam may show some distortion of the fovea, retinal striae or coexisting ERM. The patient usually reports loss of vision or visual distortion but in mild cases can be asymptomatic. Both VMA and VMT can be further categorized as focal or broad depending on the level of involvement.

Full-thickness macular holes and lamellar macular holes (FTMH and LMH)

  • OCT of macular holes appears as full-thickness foveal tears. Primary FTMH occur due to vitreomacular traction, while secondary FTMH happens due to epiretinal membranes and can be associated with conditions such as high myopia, retinal vascular disease, or cystoid macular edema. Clinically these patients present with decreased acuity and possible visual distortion. The hole appears as a red circle with a possible fluid cuff surrounding, and may contain yellow deposits at the center of the hole. Vitrectomy surgery is often recommended.
  • A lamellar hole is formed with separation of the inner retinal layers, leaving the photoreceptors intact. These can occur due to traction or ERM formation, retinal vascular disease or high myopia. These often do not progress. However, some can go on to cause FTMH. Patients typically have mild symptoms of decreased vision or distorted vision. Surgery is not typically recommended.

Epiretinal membrane (ERM) – is a condition where a thin, transparent layer forms on the surface of the retina. Clinically, this can range from looking like a mild reflective sheen on the retina to having a thicker, contracted or striated appearance. Primary ERM has a reported occurrence of 5 to 19% and usually occurs in patients over 50 years of age with a history of PVD. Patients may be asymptomatic, but with membrane progression they report decreased vision and metamorphopsia. They are usually monitored. But with significant acuity reduction, a vitrectomy and ERM peel is considered.

VITREOMACULAR DISEASE AND CATARACTS

Patients with VMT are usually best served by a retinal consultation before cataract surgery. Some with minimal retinal changes and significant cataracts might have their cataracts removed first. But most moderate to severe cases should be monitored or treated by a retinal specialist before cataract surgery.

ERM and cataracts are commonly seen together as both conditions occur in the same age range. Both can cause reduction in vision. It is important to identify which condition is contributing the most to symptoms to determine which surgery is appropriate. For those with minimal changes to macular architecture, cataract surgery usually improves functional vision to acceptable levels. Patients who have more advanced ERMs may benefit from retina surgery. After cataract surgery, patients should be monitored for progression of ERM.

A large study compared the final visual acuity and incidence of cystoid macular edema (CME) in two groups of patients who had cataract surgery—those with coexisting primary ERM formation, and those without ERM formation.

The rate of CME was 8.6% in the ERM group compared to 1.7% in the non-ERM group. The ERM group improved an average of 3 Snellen lines with presenting acuity of worse than 20/40. A much smaller improvement was noted in the group presenting with 20/40 or better acuity. The average onset of CME was 39 days. This large study suggests cataract surgery in patients with ERM increases the risk of CME and lowers the visual acuity outcome—but is still an appropriate option with careful patient selection. Patients considering cataract surgery need to be warned of the increased risk and educated about the potential for reduced vision.

COMANAGING VITREOMACULAR DISORDERS AND CATARACTS

OCT imaging of the macula should be considered when:

  • Visual acuity loss does not seem to match the level of cataract formation
  • Foveal changes are found on biomicroscopy
  • The patient reports visual distortion or central scotoma

Patients with visually significant OCT findings should have a retinal consultation before cataract referral. If possible, include the OCT image and retinal correspondence with your referral.

If you do not have OCT, our offices offer diagnostic services to community OD practices. This includes OCT with or without interpretation, which can be done before our cataract consultation. We can also perform OCT during our cataract consultation, but it’s best to avoid that on the same day as surgery. And patients should be informed that a retinal consultation may be needed before cataract surgery.

Cataract patients we treat with coexisting interface disorders will use a topical steroid and non-steroidal anti-inflammatory drop and should be monitored carefully for post-operative CME.

We believe the best care for patients with significant traction or ERM formation is a retinal consultation and clearance for cataract surgery if at all possible.

QUESTIONS

If you have questions, feel free to contact any of our optometric physicians. We’re always happy to help.
 

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