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not include the information from fluorescein angiography one can infer that the information regarding macular ischemia is not critical in providing prognostic information for patients.73
Upregulation of vascular endothelial growth factor resulting from retinal ischemia74 correlates with development of iris neovascularization.75 The detection of iris neovascularization in darkly pigmented irides can be challenging and iris fluorescein angiography76 is therefore more sensitive than clinical examination in detecting abnormal iris vessels.77 However, iris angiography is not widely utilized in clinical practice perhaps because of the lack of information as to the added value of this test above ophthalmoscopy, color fundus photography, and retinal fluorescein angiography.
neovascularization from the peripheral retina growing along the anterior hyaloid to the posterior lens surface. Hypotony occurs from traction detachment of the ciliary body. The prognosis is poor if untreated and guarded if treated. In the setting of associated vitreous hemorrhage diagnosis of AHFVP depends on a high clinical suspicion. Ultrasonography to establish the extent and location of associated fibrovascular membranes is helpful.80 High-frequency ultrasound biomicroscopy (UBM) provides greater resolution at the level of the pars plana81 and may therefore be preferable to B-scan ultrasonography in demonstrating earlier fibrovascular proliferations at the sclerotomy sites.82
6.7 Ultrasonography
In diabetic eyes ophthalmic ultrasound is a diagnostic tool with current utility primarily in eyes with opaque ocular media and vitreous hemorrhage.78 Probe placement on the globe provides better resolution and is therefore preferable to placement on the lids. In diabetic eyes with vitreous hemorrhage precluding fundus examination ultrasonography is important in determining the presence or absence of retinal detachment, the location of the hemorrhage (vitreous, loculated between the vitreous and the retina, or subretinal), and the nature of associated traction. Traction retinal detachments are more commonly found along the vascular arcades and peripapillary retina. Knowledge of the extent of traction retinal detachment in addition to whether or not the macula is attached is helpful in planning surgical intervention and advising patients about the prognosis with surgery. Blood on the posterior cortical vitreous face can resemble a retinal detachment on ultrasound examination. The higher reflectivity exhibited with retinal tissue on A-scan ultrasonography in conjunction with the lack of attachment of the posterior cortical vitreous to the optic nerve seen with dynamic B-scan ultrasonography can be helpful in differentiating these two entities.
Anterior hyaloidal fibrovascular proliferation (AHFVP) is a severe complication following diabetic vitrectomy79 which manifests with florid
6.8 Multifocal ERG
Multifocal ERG allows simultaneous electrophysiologic testing of multiple small areas of the retina. Abnormal second-order wave forms can be detected prior to the development of clinical diabetic retinopathy implying a deficit in the inner retina. In comparison, patients with clinical diabetic retinopathy have abnormalities of both first-order and second-order wave forms implying a deficit in both the inner and outer retina. 83 A delay in multifocal ERG implicit times may correlate with the chance of diabetic retinopathy onset.84 The clinical benefit of being able to predict which areas of the retina may develop changes of nonproliferative diabetic retinopathy (in the absence of finding clinically significant macular edema) has not been demonstrated.
6.9 Miscellaneous Modalities
Fluorescein does not leak from normal retinal vasculature. A breakdown of the blood retinal barrier can be measured by vitreous fluorophotometry and quantified by an instrument called the Retinal Leakage Analyzer.85 Fine matrix mapping is a modified Humphrey field analyzer which assesses photopic and scotopic retinal function. These techniques may be useful as research tools but have not gained acceptance by clinicians in management of diabetic retinopathy.
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6.10 Summary of Key Points
Clinical examination (and not OCT) should determine the presence of clinically significant macular edema.
OCT is helpful in determining the response of clinically significant macular edema to therapy.
OCT morphology may alter prognosis (cystic changes indicative of chronicity and poorer response to therapy) or alter therapy (vitreomacular traction needing surgery).
Stereoscopic color fundus photography is more sensitive than clinical examination in diagnosing diabetic retinopathy.
Fluorescein angiography is indicated to help direct laser therapy of clinically significant macular edema but current clinical practice suggests benefit from laser therapy applied without fluorescein angiogram guidance.
Determination of ischemia by fluorescein angiography is poorly reproducible.
6.11 Future Directions
Determining whether the increased resolution and sampling strategy of spectral domain OCT provide additional benefit over Stratus OCT.
Determination of the public health role of teleophthalmology in managing diabetic patients.
6.12 Practice Exercises
Exercise 1 – Hemorrhages vs. microaneurysms The ETDRS laser protocol directed focal treat-
ment to all microaneurysms between 500 and 3,000 mm from the foveola.
# Microaneurysms on fundus |
# Microaneurysms on |
photo |
FA |
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Fig. 6.9
This 54-year-old male has a 24-year history of type 1 diabetes mellitus. He complains of micropsia OS. His visual acuity OS is 20/25. Slit lamp biomicroscopy reveals clinically significant macular edema. Please identify and count on the color fundus photograph microaneurysms where focal laser would be applied (Fig. 6.9).
Microaneurysms are typically identified/confirmed in the transit phase of the fluorescein angiogram. Please identify and count on the fluorescein angiogram the microaneurysms where focal laser would be applied (Fig. 6.10).
Fig. 6.10
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Fig. 6.11 |
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Does the fluorescein angiogram change therapy? |
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Does the OCT change the pattern of laser? |
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(Fig. 6.11) |
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Exercise 2 – Identify ‘‘focal’’ leakage |
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The ETDRS defined ‘‘focal’’ leakage as leakage |
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arising from microaneurysms. |
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Does this angiogram (Figs. 6.10 and 6.12) reveal |
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any leakage that is not ‘‘focal?’’ i.e., is there |
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any region where grid laser would be applied? |
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Exercise 3 – The ETDRS defined areas of leakage |
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which were not attributable to microaneurysms as |
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‘‘diffuse.’’ The ETDRS laser protocol directed grid |
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laser to these areas of ‘‘diffuse leakage’’ in addition |
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to areas of capillary nonperfusion. This patient with |
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type 1 diabetes mellitus has clinically significant |
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macular edema (Figs. 6.13, 6.14, and 6.15). |
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Please identify the areas of capillary nonperfu- |
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sion where grid laser treatment would be applied. |
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Please identify the areas of leakage not attributable |
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to microaneurysms (‘‘diffuse’’ leakage) where grid |
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laser treatment would be applied. |
Fig. 6.12 |
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Fig. 6.13
Fig. 6.14
Fig. 6.15
K. Wong
Exercise 4 – This patient with type 1 diabetes mellitus has clinically significant macular edema. Please identify the areas of capillary nonperfusion where grid laser treatment would be applied. Please identify the areas of leakage not attributable to microaneurysms (‘‘diffuse’’ leakage) where grid laser treatment would be applied (Figs. 6.16 and 6.17).
Fig. 6.16
Fig. 6.17
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