NON ORGANIC VISUAL DISORDERS

Volume 2 Issue 12 December, 2012

Consultation Liaison Psychiatry Focus: Ophthalmology

Symptoms of visual disturbances for which there is no identifiable organic basis are Non Organic Visual Disorders. They are not uncommon and constitute 5% of general ophthalmic practice. It’s a diagnosis after a thorough clinical examination and investigations to ensure that a treatable disease is not missed. Physicians tend to get angry as they feel they are being manipulated, this should be avoided. Patients are more likely to co‐operate in providing history and response to tests if they perceive the physician as interested in their wellbeing. Information regarding litigation or disability gain should be enquired. It’s useful to differentiate the malingerer from the patient with a functional disorder i.e, a manifestation of a psychiatric disorder so that such patients may have a psychiatric referral. In psychiatry, it could be a complaint in schizophrenia or more commonly dissociative disorder, the essential feature of the dissociative disorders is a disruption in the usually integrated functions of consciousness, memory, identity, or perception of the environment. A malingerer is aware that their symptoms do not exist. While a Dissociative (older term ‘hysterical’) patient believes that their symptoms are real. Malingerers are often anxious, hostile and uncooperative while dissociative patients tend to be cooperative and unconcerned about their symptoms. It is often impossible to distinguish between the two. Sometimes a functional visual loss may co‐exist with an organic cause (functional overlay) and so they must be followed up. The main symptom may be unilateral or bilateral loss of acuity or visual field loss. Non organic visual loss can occur in children as well. Patients with non organic visual loss tend to attribute the symptoms to an injury or illness. A complete examination should include best corrected visual acuity, pupil size and reaction, colour vision, visual fields, ocular motility, slit lamp biomicroscopy , tonometry and dilated fundoscopy. No shortcuts are allowed for this category of patients and the findings should be meticulously recorded. Common organic disorders that may be mislabelled as non‐organic visual loss are early keratoconus, early posterior sub‐capsular cataract, Cone Rod dystrophy, early Stargadts disease, retinitis pigmentosa sine pigmento, paraneoplastic retionopathy, optic neuropathy without disc changes and bilateral occipital infarcts. It is rare for organic disorders to produce large disparity in visual acuity between the two eyes without detectable evidence. Tests for monocular functional visual loss include fogging (either with plus spherical or cylinder technique), Magic drops (by reinforcing that the improvement is temporary), Duochrome test, Polaroid glasses , Prism tests, Stereoacuity testing, Optokinetic nystagmus, near distance disparity, afferent pupillary defect, Visual evoked potential ( poor responses do not prove organic lesion as the response may be suppressed by inattention or defocusing). Tests for binocular loss are patients Navigating ability, Bottom up acuity, Finger touch test, Signature test, Mirror test, Shock test, Optokinetic nystagmus, Visual evoked potential. Patients presenting with field loss can be tested with tangent screen at 1 and 3 meters and Goldmann perimetry for spiralling of isopter. In medicolegal cases, clinician has to give accurate report. In other cases referral to psychiatry & assurance that the problem will improve, will suffice.