Clinicians agree, patients should be referred for retinal consult at first sign of macular edema

Issue: December 1999

When CSME develops

Joseph Sowka, OD, FAAO: I prefer to monitor and manage patients with nonproliferative diabetic retinopathy (NPDR) until clinically significant macular edema (CSME) develops. CSME is defined as 1) retinal edema at or within one-third disc diameter (DD) of the macula, 2) hard exudates associated with adjacent retinal edema within one-third DD of the macula or 3) an area of retinal edema of 1 DD within 1 DD of the macula. It is well known that laser photocoagulation of clinically significant macular edema is expected to decrease the incidence and severity of vision loss. Laser photocoagulation of any other form of retinal edema only risks complications with no benefit to the patient.

In many cases, CSME is perceptible with a contact or noncontact fundus lens and biomicroscope as areas of retinal thickening. The presence of hard exudates is a very good indication of where to look for this retinal edema. Should this retinal thickening/edema be observed in proximity to the macula as defined above, then a retinal consult for fluorescein angiography and laser photocoagulation is in order. If you suspect CSME, but cannot definitively diagnose with ophthalmoscopy alone, a fluorescein angiogram should be performed. The retinal edema will readily show up as areas of hyperfluorescence. Should these areas of hyperfluorescence impinge on the macula as mentioned above, then referral is indicated. If you cannot perform fluorescein angiography yourself and you suspect CSME, then consultation is necessary.

It must be remembered that CSME can exist in the face of 20/20 vision. Thus, you should not let good visual acuity prevent you from obtaining a retinal consult when you suspect CSME.

Hard exudates within the foveal avascular zone carry a rather poor prognosis and represent significant leakage of the perifoveal capillaries. In this instance, I would recommend both a fluorescein angiogram as well as a retinal consult.

When CSME develops

William L. Jones, OD: Patients with NPDR usually require a referral to a retinologist when there are signs of CSME. The Early Treatment Diabetic Retinopathy Study addressed this need for treatment and found that focal laser treatment for CSME reduced the rate of moderate visual loss by approximately 50%.

Diabetic macular edema (DME) is discovered by the clinician with the use of a biomicroscope and a precorneal or fundus contact lens or by stereoscopic fundus photography. This diagnosis is often made by clinical observation and not with results of visual acuities or fluorescein angiography. The presence of CSME is established by the discovery of retinal edema in the center of the macula; hard exudates within 500 µm of the center of the macula with associated retinal edema; or retinal thickening that is greater than 1 DD in size with any part within 1 DD of the center of the macula.

Almost every patient with CSME will receive treatment. However, patients with CSME who have 20/20 vision and no symptoms can be considered to have a relative indication for laser treatment, and, under certain circumstances, these patients can be safely observed (Jay S. Duker, “At Issue: laser surgery for diabetic retinopathy,” Ocular Surgery News, Oct. 1, 1999, page 50). If observation is chosen in such cases, fundus photography should be performed and the patient should be given Amsler grid self-monitoring. Patients with DME that is not yet significant may also be considered for treatment if cataract surgery is going to be performed. This is due to the possible exacerbation of the retinopathy following the surgery. Treatment consists of focal or grid laser.

Another reason to consider referral to a retinologist is the presence of high-risk diabetic retinopathy findings for developing PDR: venous beading and intraretinal microangiopathy.

Lastly, if a diabetic’s visual acuity is decreasing and there is no obvious intraocular reason to account for it, then referral would be advisable for further examination and possible fluorescein angiography.

When CSME develops

Leo P. Semes, OD: Duration of the diagnosis of diabetes is directly proportional to the risk for diabetic retinopathy. All diabetic patients need a dilated fundus evaluation on an annual or more frequent interval depending on retinal status. Given these two premises, a comprehensive medical history and a thorough stereoscopic fundus evaluation are the two minimally necessary steps to assess diabetic retinopathy. NPDR consists of microaneurysms, intraretinal hemorrhages, exudates, cotton-wool spots, intraretinal microvascular abnormalities or venous abnormalities that may be accompanied by macular edema. Risk of the patient developing proliferative diabetic retinopathy (PDR) or CSME constitutes grounds for referral.

The American Optometric Association’s Clinical Practice Guidelines base management decisions on accepted classification schemes. Therefore, in mild NPDR, annual observation is indicated. Moderate NPDR carries up to a 27% risk of progressing into PDR in 1 year. Evaluation at 6 to 12 months is indicated. When macular edema accompanies either of these stages, however, referral for fluorescein angiography is indicated. Fluorescein angiography is performed to determine the feasibility of treatment, not as a baseline measure. It is the retinal specialist’s decision to apply for or defer treatment.

Venous beading is the greatest risk factor for progression to PDR in either moderate or severe stages of NPDR. In any stage of NPDR, the presence of CSME indicates the need for retinal consultation. CSME is the greatest risk factor for diabetic retinopathy to result in vision loss.

In summary, when a threat to vision or a risk of progression to PDR is significant as evidenced by snapshot observation of CSME, venous beading or escalation to a more severe stage of NPDR, consultation with a retinal specialist is warranted.

For Your Information:

Joseph Sowka, OD, FAAO is an associate professor and the chief of primary care optometry at The Eye Institute at the Nova Southeastern University College of Optometry. He may be reached at 3200 S. University Dr., Ft. Lauderdale, FL 33328; (954) 262-1472; fax: (954) 262-1818; e-mail: jsowka@hpd.nova.edu.

William L. Jones, OD, is a member of the Editorial Board of Primary Care Optometry News and may be reached at 1828 Conestoga, SE, Albuquerque, NM 87123; (505) 293-7347; e-mail: Wm_Jones@msn.com.

Leo P. Semes, OD, is an associate professor in the department of optometry and is director of continuing education at the University of Alabama at Birmingham. Dr. Semes also is a member of the Editorial Board of Primary Care Optometry News. He may be reached at 1716 University Blvd., Birmingham, AL 35294-0010; (205) 934-6773; fax: (205) 934-6758; e-mail: Lsemes@Icare.opt.uab.edu.