Showing papers on "Optic Disk Drusen published in 2018"

Peripapillary Hyperreflective Ovoid Mass-Like Structures: Is It Optic Disc Drusen or Not?

Abstract: W e read with great interest the recent recommendations for diagnosing optic disc drusen (ODD) put forth by Malmqvist et al (1). As suggested by the authors, we agree that establishing guidelines for the diagnosis of ODD using spectral domain optical coherence tomography (SD-OCT) through the enhanced depth imaging (EDI) technique is very important. The suggested Optic Disc Drusen Studies (ODDS) Consortium diagnostic recommendations posit that ODD always have a hyporeflective core, and that the peripapillary hyperreflective ovoid mass-like structure (PHOMS), which are often regarded as buried ODD, should not be diagnosed as ODD. Although we mostly agree with the consensus of the consortium, we would like to raise the following question: If PHOMS is not diagnosed as ODD, then what does it represent? ODD with signal-poor cores on B-scan SD-OCT images are often visible on funduscopy (2,3). We thought they would show high attenuation with acoustic shadowing on B-scan ultrasonography and show a fundus autofluorescence given that these findings are likely related to calcification (4). We believe it would be more appropriate if the consortium decides to restrict the meaning of ODD to only include the calcified mass within the optic nerve head. Then, how could pseudopapilledema be explained? As the authors have stated, ODD were always detected above the lamina cribrosa. Considering the transparency of the retina, the nonvisualization of the signals in patients with pseudopapilledema could be understood in two ways. First, ODD could be buried deep (beneath the lamina cribrosa) obscuring full visualization. Second, it could be that ODD have insufficient signals for detection. In the former case, it is highly unlikely that large ODD can pass through the small pores of the lamina cribrosa. Therefore, most of the pseudopapilledema cases in the past should have been classified as PHOMS, acellular deposits without enough signals of calcification. Hence, if we were to exclude PHOMS from ODD, it becomes difficult diagnosing such cases that are not either normal or ODD. At this point, we want to stress that PHOMS should be regarded as a separate diagnostic entity if the current definition of ODD, based on EDI SD-OCT, is adopted. In addition, it should be noted that PHOMS is more important clinically than ODD since the differentiation of PHOMS from optic disc edema is more difficult than that of ODD. Although, the authors did not mention it as a limitation of their report, only patients 18 years and older were studied. Because presumed PHOMS cases (pseudopapilledema or buried ODD) would be more frequent in young subjects (2,5,6), this inclusion criteria might lead to selection bias: ODD with signalpoor cores in elderly people would have been selectively included. Recently, Traber et al (3) reported that PHOMS on SD-OCT images corresponded to the granulation tissue in the histologic section of ODD. This granulation tissue also was observed around the calcium flecks of ODD in a histologic study (4). Therefore, PHOMS may form during evolution to ODD. If PHOMS are herniated nerve fibers as the authors speculated, then a connection between the PHOMS and axons should be present. This would require neuronal marker staining or electron microscopic evidence because PHOMS may consist of non-neural glial cells mixed with extracellular matrix. We believe that the previous histologic study results favor a mixture of various cells and extracellular material over the herniated nerve fibers as the origin of PHOMS (4,7). The relationship between PHOMS and ODD remains unclear. We speculate that PHOMS could turn into ODD through cystic degeneration (hyporeflectance core) and calcification (hyperreflectance dots) in elderly patients. Our reasoning is two-fold. First, in all cases of ODD, PHOMS existed around ODD. In other words, ODD appeared within PHOMS (2,8). Second, we previously reported a case of PHOMS having a fundus autofluorescence (9), although the ODDS consortium asserted that PHOMS do not autofluoresce (1). Our case may represent a transition status between PHOMS and ODD. Proof of this would require a long-term, longitudinal study. In conclusion, we assert that if ODD are defined according to the current guidelines, then PHOMS should be regarded as a different diagnostic entity. Many alleged cases of buried ODD and pseudopapilledema may belong to this entity. PHOMS should be evaluated with great caution and it may be that PHOMS is a transitional structure leading to formation of ODD (9).

Retrobulbar axonal degeneration due to optic disc drusen.

Abstract: 1 week in a patient with allergic orbital inflammation. In our patient, hyaluronidase allergy had resulted in an orbital compartment syndrome and subsequent blindness in his left eye. Systemic inflammatory responses are extremely uncommon in hyaluronidase allergy. To the best of our knowledge, elevation of inflammatory markers in hyaluronidase allergy has not been previously described. For this reason, the absence of fever with normal inflammatory markers are potential features that distinguish allergic inflammation from orbital cellulitis. Although systemic responses have been described in rare cases of anaphylactic reactions to hyaluronidase, blood investigations in those cases were normal. In our patient, fever and leucocytosis were present on both presentations. Hyaluronidase allergy has been proposed to be a type I or type IV hypersensitivity reaction, or a combination of both. Evaluation can be performed by a combination of intradermal (delayed reaction) and skin prick (immediate reaction) testing. The sensitivity and specificity of these tests are generally high, although these values for hyaluronidase allergy are yet to be determined. There is no current evidence to support allergy testing pre-operatively. However, it may be warranted to perform such tests in patients who present with acute orbital inflammation following hyaluronidase exposure. In our patient, knowledge of hyaluronidase allergy may have prevented his second sightthreatening presentation by utilizing an alternative eye anaesthesia. In summary, it is pertinent to be aware of the potential vision-threatening complications associated with hyaluronidase allergy. Although extremely rare, systemic inflammation can be present in allergic reactions to hyaluronidase. Allergy testing is suggested in cases of suspected hyaluronidase allergy as well as atypical presentations of orbital inflammation.