A 65-YEAR-OLD white male patient presented with a chief complaint of a “constant gray spot” in his vision OD for one week. He denied any symptoms of pain or flashes of light. His medical history was positive for hypertension and hypercholesterolemia, for which he confessed poor compliance with his prescribed medications, amlodipine/benazepril (Lotrel, Novartis) and atorvastatin calcium (Lipitor, Pfizer). The patient’s in-office blood pressure was 180/130mmHg.
His BCVA was 20/25 OU. Pupils, ocular motilities and anterior segment evaluation were unremarkable. Amsler grid and confrontation VF revealed a mild central scotoma OD. Dilated examination showed normal macula and peripheral retina OU, with arteriovenous nicking, indicative of early hypertensive retinopathy OU. There was a small, flat choroidal nevus inferior nasal to the macula OS. Interestingly, OCT showed a superior perifoveal retinal thinning, which was more noticeable enface, seen as nerve fiber layer thickening OD. Retinal consultation confirmed a macular micro-infarct OD, more likely a macular retinal artery occlusion, and MRI of the brain revealed an isolated, small cerebral infarct.
Through the past decade, advances in technology have greatly improved our ability to detect early pathology and to manage retinal disease. Still, subtle retinal changes (as in the case above) or those that coexist with other significant disease, such as diabetic retinopathy, can pose diagnostic challenges, making it essential to view the problem in new ways. As timely detection is crucial to preserve vision, we must be judicious about using the latest technologies to enable us to do so.
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Here, we discuss the devices that can aid you in both the diagnosis and management of retinal disease patients, and we divulge this patient’s diagnosis and how he is doing today.
THE SLIT LAMP
The initial examination of the retina begins with inspection. The vitreous should be carefully scrutinized for pigment cells in patients complaining of flashes and/or floaters from a posterior vitreous detachment, retinal tear or detachment. Those who have diabetes, inflammatory disease or uveitis may have vitreal cells, opacities and hemorrhage.
Using advanced condensing lenses can provide large fields of view or more magnification of the retina. The three-mirror condensing lens, in particular, is excellent for assessing the presence of retinal breaks or tears and macular pathologies, such as cystoid macular edema and central serous chorioretinopathy. Slightly tilting the lens or moving the slit lamp’s illumination arm one click temporal may aid in evaluating the depth of retinal pathology, such as a subtle epiretinal membrane, among other surface disorders. The red-free filter is also beneficial for differentiating deeper lesions of the choroid, such as a choroidal nevus or melanoma.
If a macular hole is suspected, perform the slit beam, or Watzke-Allen test. Specifically, use a fundus lens, and place a narrow high-intense (bright) vertical slit beam aligned over the central fovea. Next, instruct the patient to look at the center of the beam, and identify whether a break in the beam exists, which is indicative of a full thickness macular hole. If the line runs continuous top to bottom, there is no full thickness macular defect.
Fundus cameras are excellent tools for documentation, serial comparison of structural changes and the monitoring of disease progression through time. High-quality fundus images can capture subtle defects, such as exudate or early arteriovenous changes (as in our patient), which can be missed during the clinical evaluation.
The red-free filter here can highlight retinal vascular changes, such as microaneurysms. Fundus cameras also have value as educational tools for patients when discussing their diagnosis — knowledge that may ultimately lead to better patient compliance to prescribed medications and follow-up appointments. In addition, these devices give you findings in digital form to share with colleagues and other health providers when co-managing patients.
Widefield retinal imaging allows for a large field of view, even through an undilated pupil, enabling the evaluation of the peripheral retina, which can aid in detecting diseases, such as sickle cell retinopathy. That said, you should not replace a dilated fundus examination with this camera when advised as the standard of care or based on patient symptoms (i.e. flashing lights or floaters) because it does not allow stereopsis or depth of field in certain retinal conditions, such as retinoschisis.
FUNDUS AUTOFLUORESCENCE (FAF)
FAF enables you to evaluate the presence of retinal pigment epithelium (RPE) loss or active disease, such as AMD, affecting the integrity of the RPE. Hypo-autofluorescence is observed with RPE damage or atrophy, while hyper-autofluorescence, from accumulation of lipofuscin, reveal areas of photoreceptor damage.
In addition, FAF is useful in differentiating active and inactive retinal disease, such as CMV retinitis, central serous chorioretinopathy or other posterior/retinal inflammatory conditions, by showing hyperFAF at the border of the lesions.
AUTOMATED VF TESTING
Visual field perimetry can enable you to detect central, paracentral or peripheral visual defects observed in retinal disease. Further, automated VF testing can help you identify the size and depth of the defects, allowing for the early detection and intervention of retinal conditions, such as a macular retinal artery occlusion, as in the aforementioned patient.
The central 10-2 visual field enables the assessment of macular function and, thus, is a standard screening for retinal toxicity associated with hydroxychloroquine (Plaquenil, Covis Pharmaceuticals, Inc.) As retinal toxicity may develop outside the central 10° of the parafoveal region in Asian patients, these patients should be screened with a 24-2 as opposed to the standard 10-2 VF.
SD-OCT has greatly improved the ability of practitioners to detect early retinal pathology, such as a choroidal neovascular membrane in AMD. This, in turn, has facilitated early intervention and better visual outcomes following intravitreal treatment with anti-VEGF compounds. OCT is the standard for vitreoretinal interface disorders, like vitreomacular traction or adhesion, and uncovering subtle pathologies, such as macular retinal artery occlusion observed in the case presented above.
The newest device, OCT angiography (OCTA) is a non-invasive diagnostic test that allows the assessment of retinal and choroidal blood vessels. Specifically, the individual retinal layers can be viewed, enabling you to pinpoint the precise size and localization of lesions, visualize both the retinal and choroidal vasculature pattern and view structural and blood flow information. This is particularly beneficial when dealing with diseases, such as AMD, that affect a specific retinal sub-layer. In addition, enhanced-depth imaging (EDI) provides improved visualization of the choroid, which allows for the assessment of choroidal changes in maculopathies, such as central serous chorioretinopathy, vitelliform disease, age-related choroidal atrophy and polypoidal choroidal vasculopathies. OCTA differs from fluorescein angiography in that it uses motion detection vs. intravenous fluorescein dye.
Macular Pigment Optical Density (MPOD) (not covered) is a measurement of the macular pigments, lutein and zeaxanthin, which help protect the photoreceptors from oxidative stress caused by absorption damage of ultraviolet and blue light. Low MPOD values have been associated with potential progression of AMD. Serial macular pigment optical density measurements can enable you to monitor the effects of dietary changes and supplementation.
A/B ultrasound provides high-resolution diagnostic imaging that enables the assessment of retinal pathology (i.e. retinal detachments, tumors), especially in cases of dense cataract or vitreous hemorrhage when visualization of the retina may be obscured.
Multifocal electroretinography (mfERG) allows for the detailed assessment of retinal health and function (i.e. inherited retinal disease and detects early hydroxychloroquine toxicity).
As dark adaptation function is weakened over time in retinal conditions, such as retinitis pigmentosa and inherited retinal dystrophies, this device measures dark adaptation time.
The device has also been found to aid in the identification of early functional loss in AMD patients and those at risk of AMD, yet who have no clinical signs. Demonstrating prolonged dark adaptation time may be a risk factor for AMD, becoming relevant in patient education and management with supplements.
The aforementioned patient’s retinal findings pointed to retinal artery occlusion localized to the macula OD. Also, the MRI result, early hypertensive retinopathy and severely elevated blood pressure all pointed to the patient’s stroke risk. As a result, he was instructed on compliance with medication use and co-managed with his primary care physician.
At his three-week follow-up visit, his blood pressure was lowered, his vision was stable, but his symptoms of a constant gray spot, VF defect and OCT findings persisted, as expected with a retinal artery occlusion. He continues to be monitored with six-month follow-ups.
Optometry is on the forefront of diagnosing retinal disease. As a result, optometrists need to be prepared to provide a timely diagnosis, management, referral to tertiary care providers and, most importantly, patient education on the associated ocular findings and systemic risk factors. Embracing technology allows for much faster diagnosis, more accurate management and delivery of state-of-the-art primary eye care to our patients. OM