Optical Coherence TomographyStudy of peripapillary Nerve Fiber layer ThicknessinThyroid Associated Ophthalmopathy

Abstract

Background Thyroid Associated Ophthalmopathy (TAO) or Graves Opthalmopathy (GO) is a very common autoimmune disorder of the thyroid gland which activates the gland function and result in hyperthyroidism. Some patients with graves disease(GD) develop localized manifestations including GO and dermopathy. Dysthyroid optic neuropathy (DON) is impairment of optic nerve function due to GO, the most serious complication of GO which occurs in about 4–8% of patients, it occurs due to ischemia and inflammation of the optic nerve, also compression of the optic nerve due to enlargement of extraocular muscles at the apex of orbit. Objective To assess peripapillary retinal nerve fiber layer (pRNFL) thickness in GD and to correlate it with the severity of the disease. Patients and Methods This study was conducted on 40 eyes of 21 recently diagnosed GO patients (two patients were single eyed) recruited from Endocrinology clinic and examined at Ophthalmology clinic, Ain Shams University Hospital in the period from March 2018 to September 2018. Complete ophthalmologic examination, proptosis assessment of direction and degree, Visual Field (VF) examination, clinical activity score (CAS), severity score assessment and Optical Coherence Tomography (OCT) were performed to all patients . Results In the whole group of patients; the mean average pRNFL was 109.53 um ± 12.33 SD (range: 86 – 140), median MD was -4.53 (range:-0.66 to-18.95) and -8.04 ± -2.15 SD, mean PSD was 5.55 ± 3.8 SD (range: 1.11 to 12.73). Normal average pRNFL thickness (according to normative data base included in the OCT program) was found in 15 eyes (37.5%) and those had abnormal increase in thickness was 12 eyes (30%). Abnormal decrease in thickness was detected in 13 eyes (32.5%). Conclusion PRNFL thickness abnormalities were detected in 25 eyes (62%) of recently diagnosed GO patients. This might be associated with localized visual field defects. Regular follow up of intra ocular pressure (IOP), serial VF examinations, are required to decide further management of those patients, as OCT results were correlated with degree of eye protrusion and the severity of the disease (CAS and severity score).