Roy D Brod, MD
Patients with diabetes are at increased risk of developing disease in both the anterior and the posterior segments. Evaluation of the anterior segment consists of 4 tests: measurement of intraocular pressure, inspection of the iris, gonioscopy, and assessment of lens status.
Patients with diabetes may develop open-angle glaucoma or neovascular glaucoma. Iris examination is best conducted prior to dilation, as dilation may obscure iris neovascularization. Iris neovascularization may begin at the pupillary margin. A highly magnified view of the iris is especially important in eyes with pre-existing proliferative disease, retinal ischemia, or elevated intraocular pressure. Furthermore, neovascularization may be present in the angle even if absent from the iris. The presence of a reddish tinge in the angle may indicate neovascularization. A Goldmann 3-mirror or Zeiss 4-mirror lens is recommended for gonioscopy.
Patients with diabetes are also at increased risk of developing cataract. If retinopathy is present concomitantly with cataract, the status of the lens (eg, phakia, cataract severity, pseudophakia) may affect treatment timing for retinopathy. For example, diabetic macular edema (DME) should be treated before cataract surgery. Rapid progression of diabetic retinopathy (DR) has been noted after cataract surgery. Preoperative administration of a vascular endothelial growth factor (VEGF) inhibitor under the guidance of a retina specialist may reduce the risk of postoperative DR progression.
Posterior segment examination should include examination of the vitreous as well as the retina. The presence of any cells in the vitreous should be noted, as should the condition of the cortical vitreous. Paradoxically, a posterior vitreous detachment (PVD) is a good sign: if present, there will be no posterior segment proliferative disease (PDR). This association is so strong that treatments to induce PVD are sometimes used to treat PDR. Vitrectomy induces PVD surgically; the investigational drug plasmin can be used to induce PVD pharmacologically.
Slit-lamp biomicroscopy with a 60-, 78-, or 90-diopter contact lens is the gold standard for detecting subtle retinal thickening on fundus examination. The fundus should be inspected for nonproliferative DR (NPDR), DME, neovascularization on the disc or elsewhere, preretinal or vitreous hemorrhage, and vitreoretinal traction.
The initial comprehensive eye exam should be conducted 0-5 years from diagnosis in patients with type 1 diabetes, and at diagnosis in patients with type 2 diabetes. Thereafter, repeat exams should be conducted according to the following schedule:
Patient status Repeat exam interval
No retinopathy Yearly
Mild NPDR 6-12 months
Moderate NPDR 3-6 months
Severe NPDR 2-3 months
Non–high-risk PDR 1-2 months
Pregnant Ideally, prior to pregnancy and each trimester;
otherwise at onset of pregnancy and each trimester
Patients with non–high-risk PDR should be carefully instructed to identify and report the development of floaters. Patients with pre-existing diabetes who become pregnant are at risk for progression of DR: 26% of women with no retinopathy develop DR while pregnant, 77.5% of those with any degree of DR experience progression of retinopathy while pregnant. DME that develops during pregnancy may resolve spontaneously postpartum.
Documenting retinal status with fundus photography is recommended. Standard 7-field dilated stereo fundus photography is labor intensive, but computerized nonmydriatic fundus photography is less so.
Although a number of new diagnostic instruments have become clinically available in the last 10 years, fluorescein angiography (FA) is still necessary to determine where treatable lesions are located. FA should be used whenever clinical significant DME (CSME) is present, whenever there is an unexplained visual loss (to assess for ischemia), and to detect subtle neovascularization in the presence of preretinal or vitreous hemorrhage. FA should be avoided in pregnant patients unless absolutely necessary (eg, imminent threat to vision).
Optical coherence tomography (OCT) permits quantitative measurement of DME and detection of subtle macular traction. Its role is complementary to FA and the clinical exam; OCT does not replace either of the other 2 studies. However, OCT does replace the older retinal thickness analyzer (RTA). Although RTA provides qualitative and quantitative data about retinal thickness, it provides much less data than OCT. Furthermore, RTA does not permit visualization of subretinal fluid as OCT does.
Patient education should be emphasized in the management of DR. Patients should understand the importance of compliance with medical treatment, and the need for routine eye exams even if they are asymptomatic. They should also be instructed to report new visual symptoms immediately, including flashes, floaters, distortion, scotomas, and peripheral field loss. Most of all, patients need to be taught that blindness can be prevented.
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