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 3.3 females:1 male Occurs 7.8/100,000 population1 Bilateral in 12–13% in 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 and 3) Typically, the features at the centre of the patient’s visual image (e.g 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 and 4), and the patient will have a central scotoma and the nose will be missing (Figure 6.1) 101 Macular disorders Figure 6.1 Colour image of a macular hole WATZKE–ALLEN TEST The phenomena of distortion and loss of vision are exploited in the Watzke-Allen test.3 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: separated but functioning foveal receptors • Gap centrally3: loss of function of the receptors4 It is the process of vitreous detachment that creates the macular hole The separation of the vitreous is often visible on OCT of the macula A prefoveal operculum may be visible in the early stages and is not thought to be primarily retinal tissue.5,6 GRADING The Gass grading system is still used to describe macular holes because it provides a guide to surgical success and visual outcome The grading system devised by Gass relates to ophthalmoscopy and not to OCT findings • Grade 1: The hole commences as a foveal intraretinal cyst7 (1A) or a ring of cysts (1B), seen as a central yellow spot or ring of spots,8–10 at which point, the patient may be asymptomatic or have mild blur or distortion (Figures 6.2 through 6.9) • Grade 2: A small crescentic or round hole less than 400 μm • Grade 3: A large round hole of more than 400 μm diameter (Figures 6.10 and 6.11) • Grade 4: A hole with an associated PVD (Figure 6.12) 102 Figure 6.2 Early vitreoretinal separation 18/09/2014, OD IR and OCT 30° [HR] ART(7) Q: 29 200 µm 11/19 200 µm Idiopathic macular hole 103 104 200 µm Figure 6.3 Separation progresses and produces some traction on the fovea 06/02/2015, OD IR and OCT 30° [HR] ART(10) Q: 30 200 µm 10/19 Macular disorders 200 µm Figure 6.4 Eventually, a grade macular hole has appeared 03/03/2015, OD IR and OCT 30° [HR] ART(10) Q: 29 200 µm 10/19 Idiopathic macular hole 105 106 200 µm Figure 6.5 Grade macular hole, which spontaneously improves after separation of the vitreous IR and OCT 30° ART [HS] ART(9) Q: 26 22/12/2014, OD 200 µm 13/25 Macular disorders 200 µm Figure 6.6 After separation of the vitreous from the fovea, the retina recovers to a better configuration 04/11/2015, OD IR and OCT 30° ART [HS] ART(60) Q: 35 200 µm Idiopathic macular hole 107 108 200 µm Figure 6.7 Grade macular hole with the vitreous attached to the inner retina and a cyst in the fovea 18/09/2014, OS IR and OCT 30° ART [HR] ART(9) Q: 18 200 µm 10/19 Macular disorders 200 µm Figure 6.8 Cyst is converting into a full-thickness macular hole 06/02/2015, OS IR and OCT 30° ART [HR] ART(9) Q: 30 200 µm 10/19 Idiopathic macular hole 109 110 200 µm Figure 6.9 Hole has progressed into a full-thickness hole of grade size (