tailieunhanh - Ebook Vitreoretinal disorders in primary care: Part 2

Part 2 book “Vitreoretinal disorders in primary care” has contents: Macular disorders, diabetic retinopathy, trauma, complications of anterior segment surgery, uveitis and allied disorders, miscellaneous conditions. | 6 Macular disorders INTRODUCTION The macula is a common site of symptomatic retinal pathology requiring vitreoretinal intervention. PVD is implicated in the production of the most common vitreoretinal macular disorders. IDIOPATHIC MACULAR HOLE CLINICAL FEATURES INTRODUCTION Age-related macular hole is a tangential dehiscence of the neuroretinal layer of the retina at the fovea: • • • • Occurs in middle-aged or elderly patients Occurs in females:1 male Occurs population1 Bilateral in 12–13% in 2 years after presentation in one eye2 Patients’ symptoms consist of blurred vision or distortion. In the early stages (grade 1), the patient sees a small central grey patch in their central vision, and because the receptors are not yet displaced, distortion of the image is usually absent. Distortion becomes a feature as the fovea splits apart and the photoreceptors are moved outwards onto the rim of the hole (grades 2 and 3). Typically, the features at the centre of the patient’s visual image (. the nose of a face) are reduced in size (micropsia). The brain receives fewer signals than it should in the centre of the macula because the receptors are spread apart on the rim of the macular hole. The patient’s visual system interprets this as a falsely small image centrally, hence the reduction in the size of the nose when the patient looks at a face. Eventually, over time the receptors at the edge of the hole will stop functioning (grades 3 and 4), and the patient will have a central scotoma and the nose will be missing (Figure ). 101 Macular disorders Figure   Colour image of a macular hole. WATZKE–ALLEN TEST The phenomena of distortion and loss of vision are exploited in the Watzke-Allen To perform this test, shine a thin line of light vertically via the slit lamp biomicroscope across the macular hole. Ask the patient to describe the line of light. There are three possibilities: • Straight: an intact fovea • Narrowing centrally: .