Visual loss and blurred optic discs

Case Description A healthy 29-year-old woman presented with unilateral subacute vision loss with associated pain on movement of the left eye (LE) over the previous 3 days. On clinical examination, the best-corrected visual acuity (BCVA) was 1.0 in the right eye (RE) and 0.8 in the LE. Biomicroscopy was unremarkable, and the intraocular pressure was normal bilaterally. Ishihara’s test was normal, but the patient reported a slight difference in saturation between the eyes. Relative afferent pupillary defect (RAPD) 2+ was present in the LE. Fundoscopy showed blurred optic discs in both eyes [Fig. 1a and b]. Standard automated perimetry (SAP) Humphrey 24-2 showed a subtle superior scotoma in the RE and a dense central, nasal, and temporal superior scotoma in the LE [Fig. 1c and d]. Optical coherence tomography (OCT) B-scan showed rounded, hyporeflective structures with hyper-reflective margins bilaterally [Fig. 1e and f], and peripapillary retinal nerve fiber layer (pRNFL) measurement showed nasal superior thinning in both eyes [Fig. 1g and h].Figure 1: (a and b) Fundus photography showing blurred optic discs in both eyes. (c) SAP (Humphrey 24-2) of the RE showing subtle superior scotoma. (d) SAP (Humphrey 24-2) of the LE revealing dense central, nasal, and temporal superior scotoma. (e and f) SS-OCT B-scan through the optic disc showing rounded, hyporeflective structures with hyper-reflective margins (optic disc drusen—red and yellow arrows: right and left eye, respectively). (g and h) pRNFL measurement with sectoral nasal superior thinning and mGCL measurement within normal limits in both eyesWhat Would You Do Next? Observation Brain and orbital magnetic resonance imaging (MRI) scans Repeat visual field in 3 months Ocular ultrasound. Diagnosis Optic neuritis in an optic disc with drusen. Correct Answer B. Brain and orbital MRI scans. Discussion At first glance, the patient presented with blurred optic discs; therefore, it was necessary to differentiate true disc edema from pseudo edema. This distinction can be made by carefully observing the optic disc microvasculature as in true disc edema, these vessels appear obscured and associated with hemorrhages.[1] In this case, optic disc microvasculature was clearly visible, leading to the diagnosis of pseudo edema. Because one of the main causes of pseudo edema is optic disc drusen (ODD), especially buried ODD that is not clearly visible on clinical examination, an optical coherence tomography (SS-OCT) B-scan was performed and revealed rounded, hyporeflective structures with hyper-reflective margins bilaterally, confirming ODD.[2] If diagnosis remains unclear, other exams can be helpful, such as B-scan ultrasonography, fundus autofluorescence, and computed tomography.[3,4] ODDs are acellular mucoprotein deposits that are often calcified, and pathophysiology may involve slowing of axoplasmic flow due to injury of the blood supply of the optic disc.[5,6] ODDs almost never cause the deterioration of visual acuity alone.[7] Subacute vision loss and pain with eye movement, which is associated with the severe central visual field defect (VFD) in the patient, are not consistent with ODD. It is believed that VFD due to ODD is caused by the compression and compromise of axons and blood supply, but these VFDs are typically peripheral.[1] Furthermore, the OCT showed a superior pRNFL defects in both eyes. Given this finding, it is important to know whether ODD or another optic neuropathy is responsible for this alteration. ODD is associated with decreased pRNFL, mainly adjacent to ODD.[7,8] However, note that the superior pRNFL defect was present in both eyes, whereas the patient complained of visual loss only in her LE, leading us to attribute this pRNFL defect to ODD. The clinical findings of unilateral subacute visual loss, pain with eye movement, RAPD, profound central VFD, and color vision loss in a young woman suggested optic neuritis (ON). It is worth noting that in acute ON, the pRNFL is typically within normal limits and takes about 4 weeks to show signs of neuroaxonal loss, confirming that the superior pRNFL defect was caused by the ODD and not by the ON.[2,9] As the most cases of demyelinating ON are retrobulbar and thus do not present optic disc edema, the brain and orbital MRI scans were requested and showed left intraorbital anterior optic nerve enlargement with high signal intensity, indicating ON [Fig. 2a] without evidence of white matter abnormalities in brain areas.[10] The patient received intravenous pulse therapy with methylprednisolone, with marked improvement in visual acuity and visual field [Fig. 2d and e].Figure 2: (a) Orbital MRI scan showing left intraorbital optic nerve enlargement with high signal intensity, indicating optic neuritis (red arrow) (right eye b, left eye c). Top (first evaluation): pRNFL measurement with sectoral nasal superior thinning, and mGCL measurement within normal limits in both eyes. Bottom (after 4 weeks): pRNFL and mGCL unchanged in the RE, and slight worsening of superior nasal thinning of pRNFL and notable diffuse thinning of mGCL in the LE. Note the significant decrease of mGCL, indicating the real neuroaxonal loss secondary to optic neuritis in the LE (right eye d, left eye e). SAP (Humphrey 24-2) after pulse therapy. Note the marked improvement in the visual field of the LEAs expected, 4 weeks later, OCT showed worsening of superior nasal thinning of pRNFL and notable diffuse thinning of mGCL, indicating the real neuroaxonal loss secondary to ON in the LE [Fig. 2c], and RE remained stable [Fig. 2b]. This case report highlights the importance of correlating clinical features with the findings on physical examination and ancillary exams, always considering whether the findings can explain the patient’s complaints. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.