Menoufia Medical Journal

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 31  |  Issue : 1  |  Page : 273--277

Evaluation of visual field sensitivity and optical coherence tomography in pseudoglaucomatous optic neuropathy


Moustafa K Nassar, Moataz F Elsawy, Khalid M Esmail Al-Azzony 
 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Menoufia, Egypt

Correspondence Address:
Khalid M Esmail Al-Azzony
Department of Ophthalmology, Faculty of Medicine, Menoufia University, Shebin Elkom
Egypt

Abstract

Objective The aim of the study was to evaluate the protocol of optical coherence tomography (OCT) and visual field (VF) sensitivity testing in the diagnosis of pseudoglaucomatous optic neuropathy and avoid misdiagnosis with glaucoma. Background Pseudoglaucoma is defined as false or deceptive glaucoma with or without ocular damage. Multiple entities can produce 'pseudoglaucomatous optic disc' and care should be taken to differentiate it from glaucomatous eyes that, for the present, do not reveal symptoms of glaucoma.Patients who have pseudoglaucomatous optic disc cupping should be invitigated well. Patients and methods This study was conducted on 39 eyes (of 24 patients) to assess the protocol of OCT and VF sensitivity testing in the diagnosis of pseudoglaucomatous optic neuropathy. Results In this study the average age was significantly lower in patients with pseudoglaucomatous cupping (24 years). Best-corrected visual acuity (BCVA) did not significantly decrease in patients after pseudoglaucomatous optic neuropathy. Patients with nonglaucomatous optic nerve cupping had better VF mean deviation and pattern standard deviation. Eyes with pseudoglaucomatous optic nerve cupping had a lower mean retinal nerve fiber layer (RNFL) in both the nasal and temporal quadrants. Conclusion VF sensitivity and OCT appear to be of value in the evaluation of pseudoglaucomatous optic disc cupping. The pattern of RNFL loss varied on the basis of etiology and appeared more diffuse in nonglaucomatous optic nerve cupping. The nasal and temporal RNFL thicknesses were lower in patients with nonglaucomatous optic nerve cupping compared with the reported results in glaucoma patients. The pattern of VF defect varied depending on etiology and the VF mean deviation and pattern standard deviation were better compared with the results reported in glaucoma patients.



How to cite this article:
Nassar MK, Elsawy MF, Esmail Al-Azzony KM. Evaluation of visual field sensitivity and optical coherence tomography in pseudoglaucomatous optic neuropathy.Menoufia Med J 2018;31:273-277


How to cite this URL:
Nassar MK, Elsawy MF, Esmail Al-Azzony KM. Evaluation of visual field sensitivity and optical coherence tomography in pseudoglaucomatous optic neuropathy. Menoufia Med J [serial online] 2018 [cited 2020 Mar 28 ];31:273-277
Available from: http://www.mmj.eg.net/text.asp?2018/31/1/273/234232


Full Text



 Introduction



When diagnosing glaucoma or monitoring its progression, doctors rely on the appearance of the disc, measures of retinal nerve fiber layer (RNFL) thickness, and visual fields (VFs). However, other disorders of the optic nerve can also produce VF findings, nerve fiber layer loss, and disc appearance that mimic glaucoma. Unfortunately, a misdiagnosis can have serious consequences, not just for the patient's vision but for the patient's overall health and well-being [1].

Pseudoglaucoma is defined as false or deceptive glaucoma with or without ocular damage. Multiple entities can produce 'pseudoglaucomatous optic disc' and care should be taken to differentiate it from glaucomatous eyes that, for the present, do not reveal symptoms of glaucoma [2].

A number of clinical conditions may mimic glaucomatous optic neuropathy and these must be considered and excluded. They include the following:

A physiological or congenital large optic cupCongenital anomalies of the optic nerve, such as congenital pits, colobomas, morning glory syndrome, and the tilted optic discA pale, cupped nerve can sometimes result from diseases such as ischemic optic neuropathy, optic neuritis, toxic optic neuropathy, shock optic neuropathy, compressive lesions, Leber's hereditary optic neuropathy, and dominant optic atrophy [3].A VF test is an eye examination that can detect dysfunction in central and peripheral vision, which may be caused by various medical conditions such as glaucoma, stroke, brain tumors, or other neurological deficits. Optical coherence tomography (OCT) may have the potential to help in decision making (glaucomatous vs. nonglaucomatous cupping) when VF is not definitive with progressive cupping and normal intraocular pressure (IOP) [4].

 Patients and Methods



This study was conducted on 39 eyes (of 24 patients) to assess the protocol of OCT and VF sensitivity testing in the diagnosis of pseudoglaucomatous optic neuropathy.

Inclusion criteria

Patients of either sex, of any age, with optic nerve cupping were included in this study.

Exclusion criteria

Patients with high intraocular pressure, glaucomatous optic neuropathy, unreliable VF test result, and retinal pathology (i.e., diabetic retinopathy, central retinal vein occlusion) were excluded from the study.

Methods

All patients underwent examination under a Snellen visual acuity chart, evaluation of refraction errors with an auto-refractometer, BCVA, slit lamb examination, pupil examination, tonometry, dilated fundus examination, colored fundus photography (Fundus camera TOPCON TRC.50DX), Humphrey visual field examination (Essebaan, The Netherlands), and OCT (TOPCON).

The recorded data were used to evaluate the protocol of OCT and VF sensitivity for the diagnosis of pseudoglaucomatous optic neuropathy.

 Results



Sociodemographic data

There were 13 (54.2%) male and 11 (45.8%) female patients. The average age was significantly lower in patients with nonglaucomatous cupping (24 years) [Table 1].{Table 1}

Etiological and numerical data

There were 24 cases of non glaucomatous optic neuropathy: two (8.3%) with dominant optic neuropathy OU, two (8.3%) with nonarteritic anterior ischemic optic neuropathy NA-AIN OU, two (8.3%) with optic neuritis OS, one (4.2%) with optic neuritis OD, three (12.5%) with compressive optic neuropathy OU, nine (37.5%) with macrodisc (physiological cupping) OU, one (4.2%) with tilted disc OD, one (4.2%) with papillorenal syndrome OU, one (4.2%) with morning glory syndrome OD, one (4.2%) with nutritional optic neuropathy OD, and one (4.2%) with optic disc pit OD [Table 2].{Table 2}

Clinical and functional data

The BCVA of the study group was not significantly decreased in nonglaucomatous optic neuropathy cases [OD: 0.60 (0.05–1), OS: 0.80 (0.05–1)]. Patients with nonglaucomatous optic nerve cupping had better VF mean deviation (MD) and pattern standard deviation (PSD) compared with patients with glaucomatous optic nerve cupping. The VF MD (db) was −3.28 (−23.01 to −25.34) (OD), −4.18(−14.01 to **−1.44) (OS). The VF PSD (db) was 2.75 (1.26–14.23) (OD), 2.27 (1.10–14.17) (OS) [Table 3].{Table 3}

Structural data

Eyes with nonglaucomatous optic nerve cupping had a lower mean RNFL in both the nasal and temporal quadrants. The nasal RNFL thickness (μm) was 74.91 ± 21.53 (OD) and 74.47 ± 19.94 (OS). The temporal RNFL thickness (μm) was 57.09 ± 21.23 (OD) and 60.15 ± 16.80 (OS). The average RNFL thickness (μm) was 87.59 ± 24.18 (OD) and 88.84 ± 21.52 (OS) [Table 4].{Table 4}

Morphological data

In the optic nerve topography maps, eyes with optic nerve cupping had increased cup-to-disc area ratio. The disc area (mm 2) was 2.36 ± 0.77 OD optic disc (OD) and 2.36 ± 0.74 OS optic size (OS), the cup area (mm 2) was 1.04 ± 0.66 (OD) and 1.08 ± 0.60 (OS), the rim area (mm 2) was 1.38 ± 0.39 (OD) and 1.29 ± 0.40 (OS), and the cup-to-disc area ratio was 0.43 ± 0.18 (OD) and 0.49 ± 0.14 (OS) in nonglaucomatous and glaucomatous optic nerve cupping, respectively [Table 5].{Table 5}

 Discussion



When diagnosing glaucoma or monitoring its progression, doctors rely on the appearance of the disc, measures of RNFL thickness, and VFs. However, other disorders of the optic nerve can also produce VF findings, nerve fiber layer loss, and disc appearance that can mimic glaucoma [5].

Nonglaucomatous optic neuropathies have been reported to cause cupping of the optic nerve. Symptoms that mimic those found in glaucoma cases are arteritic anterior ischemic optic neuropathy, nonarteritic anterior ischemic optic neuropathy (NA-AION) [6], posterior ischemic optic neuropathy [7], intracranial tumors [8], optic neuritis [9], methanol toxicity [10], shock optic neuropathy [11], post-traumatic optic neuropathy, and congenital and hereditary optic neuropathies [12].

Clinically, symptoms such as optic nerve head (ONH) pallor can be useful in distinguishing glaucomatous from nonglaucomatous optic nerve cupping. However, the identification of optic nerve pallor is often variable and dependent upon clinical experience. In practice, the differentiation of glaucomatous from nonglaucomatous cupping can be difficult even for experienced observers.

Cupping of the ONH is a classic sign of glaucoma; however, nonglaucomatous optic neuropathies can cause contour changes of the ONH as well. Currently, ONH pallor, color vision, IOP, and visual acuity are used to aid the evaluation of nonglaucomatous optic nerve cupping. There still remain clinical situations in which nonglaucomatous cupping cannot be reliably excluded without neuroimaging, indicating a need for further methods to assist in the clinical evaluation of such patients.

This study applied VF testing and OCT imaging to evaluate nonglaucomatous optic nerve cupping.

VF testing is crucial for the diagnosis and monitoring of optic neuropathies. Certain VF defects are associated with, but not specific to, various optic neuropathies and have been the basis of important research. Identification of VF defects indicative of optic nerve disease is historically based on kinetic perimetry, particularly Goldmann and tangent screen perimetry. It is necessary for clinicians to gain experience for each VF testing technique, as well as bearing in mind that VF defects are not pathognomonic [13].

OCT is an imaging modality that employs near-infrared light to create cross-sectional images of the retina and optic nerve, thereby allowing analysis of the ONH, macula, and RNFL. It is a noninvasive and rapidly obtained imaging test. OCT has been studied widely to evaluate macular and RNFL changes in glaucoma [14].

OCT has been shown to have good reproducibility of RNFL thickness measures, suggesting that it may be a useful clinical tool to monitor glaucomatous disease progression. More recently OCT has been applied to evaluate eye diseases associated with neuro-ophthalmic conditions such as multiple sclerosis, optic neuritis, NA-AION, band atrophy, and traumatic optic neuropathy. Furthermore, specific to NA-AION and optic neuritis, recent studies have shown that OCT can be used to track RNFL loss over time and can be correlated with visual dysfunction.

Quigley reported that nasal and temporal RNFL thicknesses were lower in patients with nonglaucomatous optic nerve cupping compared with that in patients with glaucomatous cupping, and the RNFL loss in nonglaucomatous optic nerve cupping is not typically in the superior and inferior quadrants, as reported in glaucoma.

Quigley and Green [15] reported that the pattern of RNFL loss in glaucoma tends to be greater in the superior and inferior quadrants, whereas RNFL loss in nonglaucomatous optic neuropathy was more varied, depending on the etiology. Our present study found similar results in that it showed that the pattern of RNFL loss in nonglaucomatous optic neuropathy varied depending on etiology as in compressive optic neuropathy. The nasal and temporal RNFL thicknesses were lower in patients with nonglaucomatous optic nerve cupping compared with the reported results in glaucoma, such as in patients with optic neuritis and NA-AION. Gupta made similar observations. Cases with physiological cupping showed normal RNFL thickness in all quadrants.

Lu et al. [16] recently showed that the best parameters to detect glaucoma using OCT are a below-normal inferior quadrant, superior quadrant, or overall mean RNFL thickness. The findings of Gupta suggest that overall mean RNFL loss occurs in optic nerve damage due to any cause and is not necessarily specific for glaucoma etiology. This observation is similar to that found in this study.

It is known that RNFL thickness decreases with age [17]. In the study by Parikh et al. [17], the age of the patients was significantly lower among those with nonglaucomatous optic nerve cupping, which was also the group with lower RNFL thickness in the nasal and temporal quadrants, suggesting that age variance was not a factor for these findings. This is similar to the results of our study, in which we found that the age of the patients was significantly lower in those with nonglaucomatous optic nerve cupping, which was also the group with lower RNFL thickness in the nasal and temporal quadrants, suggesting that age variance was not likely the reason for these findings.

In the study by Parikh et al. [17], eyes with nonglaucomatous optic nerve cupping had higher rim area compared with the reported results in glaucomatous optic nerve cupping. Our study also revealed high rim area in nonglaucomatous optic nerve cupping. The disc, rim, cup areas, and cup-to-disc area ratio are higher in physiological cupping than in pathological nonglaucomatous cupping.

Gupta et al. showed that the pattern of VF defect varied depending on etiology. Altitudinal defects are more common in ischemic optic neuropathies, and central or cecocentral defects frequently accompany toxic/nutritional and hereditary optic neuropathies. A central or paracentral scotoma is common in optic neuritis. A hemianopic defect respecting the vertical midline indicates a lesion at or posterior to the chiasm. A junctional scotoma, defined as ipsilateral central field defect and contralateral superotemporal field defect, indicates a compressive lesion at the junction of the optic nerve and the chiasm. Vertically aligned defects should raise the suspicion of pseudoglaucomatous optic disc.

In this study we found that the pattern of VF defect varied depending on etiology: inferior altitudinal defect in NA-AION, paracentral scotoma in optic neuritis, cecocentral defects in dominant optic neuropathy, left homonyomus hemianopia with starting right inferior quadrant ichemianopia in suprachiasmal lesion and right nasal contraction of the central field, and left enlarged blind spot in retrocerebellar arachnoid cyst. In physiological cupping the VF was normal.

Gupta et al. reported that patients with nonglaucomatous optic nerve cupping had better VF MD and PSD compared with the reported results in patients with glaucomatous optic nerve cupping. Our study showed the same results.

DeLeón-Ortega et al. showed that Humphrey visual field testing may not accurately reflect the visual function [18]. They correlated RNFL with the VF in patients with NA-AION, and found that RNFL loss extends beyond the region corresponding to the VF defect. Similarly, Noval et al. [19] showed that in patients with optic neuritis, OCT detected axonal loss before the detection of a VF defect, and also correlated the degree of mean RNFL thinning with visual acuity. They showed that RNFL loss may extend beyond the region corresponding to the VF defect as in NA-AION and may detect axonal loss before the detection of a VF defect as in optic neuritis.

Visual field testing is an integral component of neuro-ophthalmic examination and is critical for the diagnosis of optic neuropathy. The VF defects in optic neuropathies can take several patterns, and vertically aligned defects should raise the suspicion of pseudoglaucomatous optic disc, which requires neuroimaging.

OCT may have the potential to complement clinical decision making when there is a question of glaucomatous versus nonglaucomatous optic nerve cupping specifically when VF testing and clinical examination (the presence of optic nerve pallor) are not definitive, or in the setting of progressive cupping despite adequate intraocular pressure control.

 Conclusion



One's perception of increased cupping being associated with glaucoma should be changed. Special attention should be given to pseudoglaucomatous optic disc cupping, which may produce a zone of confusion and is considered a diagnostic dilemma for glaucoma specialists because of optic disc appearance without an elevated IOP.

VF testing and OCT appear to be of value in the evaluation of pseudoglaucomatous optic disc cupping. The pattern of RNFL loss varied depending on etiology and appears more diffuse in nonglaucomatous optic nerve cupping. The nasal and temporal RNFL thicknesses were lower in patients with nonglaucomatous optic nerve cupping compared with the reported results in glaucoma. The pattern of VF defect varied depending on etiology, and VF MD and PSD were better compared with the results reported in glaucoma cases.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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