Retinal Ganglion Cell Layer Analysis by Optical Coherence Tomography in Toxic and Nutritional Optic Neuropathy

Maculopapillary Bundle Degeneration in Optic Neuropathies

PURPOSE OF REVIEW

Degeneration of the maculopapillary bundle (MPB) is a prominent feature in a spectrum of optic neuropathies. MPB-selective degeneration is seen in specific conditions, such as nutritional and toxic optic neuropathies, Leber hereditary optic neuropathy (LHON), and dominant optic atrophy (DOA). Despite their distinct etiologies and clinical presentations, which encompass variations in age of incidence and monocular or binocular onset, these disorders share a core molecular mechanism: compromised mitochondrial homeostasis. This disruption is characterized by dysfunctions in mitochondrial metabolism, biogenesis, and protein synthesis. This article provides a comprehensive understanding of the MPB's role in optic neuropathies, emphasizing the importance of mitochondrial mechanisms in the pathogenesis of these conditions.

RECENT FINDINGS

Optical coherence tomography studies have characterized the retinal nerve fiber layer changes accompanying mitochondrial-affiliated optic neuropathies. Selective thinning of the temporal optic nerve head is preceded by thickening in early stages of these disorders which correlates with reductions in macular ganglion cell layer thinning and vascular atrophy. A recently proposed mechanism underpinning the selective atrophy of the MPB involves the positive feedback of reactive oxygen species generation as a common consequence of mitochondrial dysfunction. Additionally, new research has revealed that the MPB can undergo degeneration in the early stages of glaucoma, challenging the historically held belief that this area was not involved in this common optic neuropathy. A variety of anatomical risk factors influence the propensity of glaucomatous MPB degeneration, and cases present distinct patterns of ganglion cell degeneration that are distinct from those observed in mitochondria-associated diseases. This review synthesizes clinical and molecular research on primary MPB disorders, highlighting the commonalities and differences in their pathogenesis.

KEY POINTS (BOX)

1. Temporal degeneration of optic nerve fibers accompanied by cecocentral scotoma is a hallmark of maculopapillary bundle (MPB) degeneration. 2. Mechanisms of MPB degeneration commonly implicate mitochondrial dysfunction. 3. Recent research challenges the traditional belief that the MPB is uninvolved in glaucoma by showing degeneration in the early stages of this common optic neuropathy, yet with features distinct from other MPB-selective neuropathies. 4. Reactive oxygen species generation is a mechanism linking mitochondrial mechanisms of MPB-selective optic neuropathies, but in-vivo and in-vitro studies are needed to validate this hypothesis.

Recent advances in the use of optical coherence tomography in neuro-ophthalmology: A review

Optical coherence tomography (OCT) is an in vivo imaging modality that provides non-invasive, high resolution and fast cross-sectional images of the optic nerve head, retina and choroid. OCT angiography (OCTA) is an emerging tool. It is a non-invasive, dye-free imaging approach of visualising the microvasculature of the retina and choroid by employing motion contrast imaging for blood flow detection and is gradually receiving attention for its potential roles in various neuro-ophthalmic and retinal conditions. We will review the clinical utility of the OCT in the management of various common neuro-ophthalmic and neurological disorders. We also review some of the OCTA research findings in these conditions. Finally, we will discuss the limitations of OCT as well as introduce other emerging technologies.

One-year follow up of a tobacco alcohol optic neuropathy case with atypical course: Conventional assessment and Laser speckle flowgraphy

PURPOSE

To describe the unexpected one-year course of a probable Tobacco Alcohol Optic Neuropathy (TAON) and the unprecedented Laser Speckle Flowgraphy (LSFG) assessment.

CASE REPORT

A 49-year-old Caucasian man with no family history of visual impairment referred because of unilateral and painless visual acuity (VA) decrease in the right eye (RE). Also, color vision and visual evoked potentials were unilaterally altered. Optical coherence tomography (OCT), instead, revealed bilateral thinning of the macular ganglion cell inner plexiform layer. Funduscopy, intraocular pressure, pupillary shape/reactivity and ocular motility were normal. Blood testing revealed macrocytic/normochromic anemia and low levels of vitamin B2 and folic acid. The patient admitted heavy tobacco and alcohol intake for many years. After an initial compliance to the prescribed regimen, the patient quitted the vitamin intake and resumed his smoking and drinking habits. After a 13-month follow up the VA further reduced in the RE; the fellow eye preserved normal visual function despite the bilateral and progressive alterations of the OCT assessment. Both eyes underwent LSFG examination. All the conventional nets evaluated by the instrument (i.e., Mean Tissue, Mean All and Mean Vascular perfusion) were lower in the RE.

CONCLUSIONS

Based on patient's behavior, visual deficiencies and laboratory findings, we assumed that the patient suffered from TAON. Also after one year, however, a deep discrepancy between the strictly unilateral, progressive VA impairment and the bilateral, symmetrical OCT alterations persisted. The LSFG data clearly indicate that the perfusion of the two eyes differed, especially referring to tissular vascularization in the optic nerve head area of the RE.

AN EYE FOR AN EYE, A TOOTH FOR A TOOTH

A 77-year-old man presented with the complaint of a painless decrease in vision in both eyes for one year. He underwent bilateral cataract surgery without improvement. Neuroimaging and genetic testing for mitochondrial disease was negative. Examination was consistent with a diagnosis of toxic-nutritional optic neuropathy. On further questioning the patient admitted chronic ingestion of mouthwash 3 times daily in the past 18 months after completion of dental work. After discontinuation of mouthwash ingestion, visual acuity and fields improved. This case shows how chronic ingestion of mouthwash can lead to a bilateral toxic optic neuropathy even in the absence of other risk factors.

Analysis of Peripapillary Vessel Density in Ethambutol-induced Optic Neuropathy Using Optical Coherence Tomography Angiography

Purpose: To investigate the changes in peripapillary and macular vessel density in ethambutol-induced optic neuropathy using optical coherence tomography angiography (OCTA).Methods: The medical records of patients diagnosed with ethambutol-induced optic neuropathy were analyzed retrospectively. Patient age, sex, daily dose (mg/day/kg), treatment duration, best-corrected visual acuity (logMAR), color vision (Ishihara color plate tests), and mean deviation of visual field test were evaluated in non-pathological individuals with age and sex controlled as the normal control group. Peripapillary retinal nerve fiber layer (RNFL) thickness, macular ganglion cell/inner plexiform layer (GC/IPL) thickness, radial peripapillary capillary (RPC) density, and macular superficial capillary plexus (SCP) density were also compared between the patient and control groups.Results: The study included 22 patient eyes and 31 control group eyes. Comparing the OCTA results between the groups, there were no significant differences in peripapillary RNFL thickness, but the temporal RPC density was significantly (p = 0.025) lower in the patient group (48.00 ± 8.23%) than in controls (52.39 ± 5.58%). For macular structures, the mean GC/IPL thickness and whole SCP density were lower in the patients (p = 0.001 and p = 0.008, respectively). In the patients, the changes in peripapillary RNFL thickness and RPC density were significantly positively correlated (r = 0.811, p < 0.001), as were the mean macular GC/IPL thickness and whole SCP density (r = 0.445, p = 0.037).Conclusions: Patients with ethambutol-induced optic neuropathy had significantly lower temporal RPC and macular SCP densities. Ethambutol toxicity may affect not only axonal degeneration but also peripapillary and macular vascular function.

Vitamins are Indeed Vital Amines: A Discussion of 3 Deficiencies With Neurologic Manifestations

Optimal functioning of the human nervous system depends on a constant supply of nutrients, vitamins, and minerals. In the developed world, nutritional deficiencies are relatively rare and infrequently present with neurologic manifestations. These neurologic disorders can be mistaken for inflammatory and/or autoimmune phenomena. This manuscript describes 2 pediatric cases with neurologic signs/symptoms arising from vitamin deficiencies-(1) optic neuropathy and (2) Wernicke encephalopathy associated with a Guillain-Barre-like pattern of weakness. The 2 cases and the subsequent discussion of vitamin A, B1, and B12 deficiencies underscore the value of taking a thorough dietary history and emphasize risk factors for these 3 nutritional deficiencies.

Visual electrophysiology in the assessment of toxicity and deficiency states affecting the visual system

Visual disturbance or visual failure due to toxicity of an ingested substance or a severe nutritional deficiency can present significant challenges for diagnosis and management, for instance, where an adverse reaction to a prescribed medicine is suspected. Objective assessment of visual function is important, particularly where structural changes in the retina or optic nerve have not yet occurred, as there may be a window of opportunity to mitigate or reverse visual loss. This paper reviews a number of clinical presentations where visual electrophysiological assessment has an important role in early diagnosis or management alongside clinical assessment and ocular imaging modalities. We highlight the importance of vitamin A deficiency as an easily detected marker for severe combined micronutrient deficiency.

Analysis of structural injury patterns in peripapillary retinal nerve fibre layer and retinal ganglion cell layer in ethambutol-induced optic neuropathy

BACKGROUND

We investigated structural injury patterns in the peripapillary retinal nerve fibre layer (p-RNFL) and ganglion cell inner plexiform layer (GCIPL) caused by ethambutol treatment.

METHODS

Sixty-four patients undergoing ethambutol treatment at Zhejiang Chinese Medicine and Western Medicine Integrated Hospital were recruited. Fourteen (14) exhibited visual dysfunction (abnormal group), and the remaining 50 had no visual dysfunction (subclinical group). The thickness of the p-RNFL, total macular retina layer and GCIPL were measured using Cirrus-HD Optical coherence tomography (Cirrus-HD OCT, Cirrus high-definition optical coherence tomography), and compared with 60 healthy, age-matched controls.

RESULTS

The p-RNFL thickness was similar in both subclinical and control groups. When compared with the control group, p-RNFL thickness in the abnormal group was significantly increased in the inferior and superior quadrants (GEE, P = 0.040, P = 0.010 respectively). In contrast with the subclinical group, p-RNFL thickness in the inferior quadrant was increased in the abnormal group (GEE, P = 0.047). The GCIPL thickness in the inferonasal and inferior sectors was significantly deceased in the subclinical group when compared with controls (GEE, P = 0.028, P = 0.047, respectively). The average and minimum value of GCIPL thickness, and thickness in the superonasal, inferior, inferotemporal, superotemporal and superior sectors were significantly decreased in the abnormal group when compared with controls (GEE, P = 0.016, P = 0.001, P = 0.028, P = 0.010, P = 0.012, P = 0.015, P = 0.010, respectively). The cube average macular thickness (CAMT) in the abnormal group was significantly thinner than controls (GEE, P = 0.027).

CONCLUSIONS

GCIPL measurements using Cirrus-HD OCT detected retinal ganglion cell layer loss following ethambutol treatment, before visual dysfunction occurred.

Ambient Air Pollution Associations with Retinal Morphology in the UK Biobank

Purpose

Because air pollution has been linked to glaucoma and AMD, we characterized the relationship between pollution and retinal structure.

Methods

We examined data from 51,710 UK Biobank participants aged 40 to 69 years old. Ambient air pollution measures included particulates and nitrogen oxides. SD-OCT imaging measured seven retinal layers: retinal nerve fiber layer, ganglion cell–inner plexiform layer, inner nuclear layer, outer plexiform layer + outer nuclear layer, photoreceptor inner segments, photoreceptor outer segments, and RPE. Multivariable regression was used to evaluate associations between pollutants (per interquartile range increase) and retinal thickness, adjusting for age, sex, race, Townsend deprivation index, body mass index, smoking status, and refractive error.

Results

Participants exposed to greater particulate matter with an aerodynamic diameter of <2.5 µm (PM_2.5) and higher nitrogen oxides were more likely to have thicker retinal nerve fiber layer (β = 0.28 µm; 95% CI, 0.22–0.34; P = 3.3 × 10⁻²⁰ and β = 0.09 µm; 95% CI, 0.04–0.14; P = 2.4 × 10⁻⁴, respectively), and thinner ganglion cell–inner plexiform layer, inner nuclear layer, and outer plexiform layer + outer nuclear layer thicknesses (P < 0.001). Participants resident in areas of higher levels of PM_2.5 absorbance were more likely to have thinner retinal nerve fiber layer, inner nuclear layer, and outer plexiform layer + outer nuclear layers (β = –0.16 [95% CI, –0.22 to –0.10; P = 5.7 × 10⁻⁸]; β = –0.09 [95% CI, –0.12 to –0.06; P = 2.2 × 10⁻¹²]; and β = –0.12 [95% CI, –0.19 to –0.05; P = 8.3 × 10⁻⁴], respectively).

Conclusions

Greater exposure to PM_2.5, PM_2.5 absorbance, and nitrogen oxides were all associated with apparently adverse retinal structural features.

Nutritional Optic Neuropathies: State of the Art and Emerging Evidences

Nutritional optic neuropathy is a cause of bilateral, symmetrical, and progressive visual impairment with loss of central visual acuity and contrast sensitivity, dyschromatopsia, and a central or centrocecal scotoma. The clinical features are not pathognomonic, since hereditary and toxic forms share similar signs and symptoms. It is becoming increasingly common due to the widespread of bariatric surgery and strict vegetarian or vegan diets, so even the scientific interest has recently increased. In particular, recent studies have focused on possible pathogenetic mechanisms, and on novel diagnostic and therapeutic strategies in order to prevent the onset, make a prompt diagnosis and an accurate nutritional supplementation, and to avoid irreversible optic nerve atrophy. Nowadays, there is clear evidence of the role of cobalamin, folic acid, thiamine, and copper, whereas further studies are needed to define the role of niacin, riboflavin, and pyridoxine. This review aims to summarize the etiology, diagnosis, and treatment of nutritional optic neuropathy, and it is addressed not only to ophthalmologists, but to all physicians who could come in contact with a patient with a possible nutritional optic neuropathy, being a fundamental multidisciplinary approach.

Different damage patterns of retinal nerve fiber layer and ganglion cell-inner plexiform layer between early glaucoma and non-glaucomatous optic neuropathy

AIM

To compare the damage pattern of the peripapillary retinal nerve fiber layer (pRNFL) and the macular ganglion cell-inner plexiform layer (mGCIPL) between early glaucomatous and non-glaucomatous optic neuropathy (EGON and NGON).

METHODS

It is a cross-sectional study. Thirty-eight healthy controls, 74 EGONs and 70 NGONs with comparable average pRNFL loss were included. The NGON group included 23 eyes of optic neuritis (ON), 13 eyes of hereditary optic neuropathy (HON), 19 eyes of toxic optic neuropathy (TON) and 15 eyes of compressive neuropathy (CON). The sectoral pRNFL and mGCIPL thickness obtained by high definition optical coherence tomography were analyzed.

RESULTS

Compared to normal controls, the pRNFL thickness in all quadrants showed a decrease in both EGON and NGON group (P<0.001), but the average pRNFL thickness of EGON group was not different to that of NGON group (P=0.94). The inferior and superior pRNFL was thinner in EGON group compared to NGON group (P<0.001). The temporal pRNFL was thinner in NGON group compared to EGON group (P<0.001). No statistically significant difference was found in nasal pRNFL between EGON and NGON. While the nasal pRNFL was thinner in CON than other three types of NGON (P=0.01), no statistically significant difference was found in other three quadrantal pRNFL among the four types of NGON (P>0.05). The mGCIPL of EGON and NGON group were thinner than control group (P<0.001). In EGON group the severest sites of mGCIPL reduction was located at inferotemporal and inferior sectors. While, compared to EGON group, the average mGCIPL of NGON group were significantly thinner, especially in superonasal and inferonasal sectors (P<0.001).

CONCLUSION

The damage pattern of pRNFL and mGCIPL caused by glaucoma is distinct from other NGON such as ON, TON, HON and CON, and this characteristic damage pattern is helpful in differentiating early glaucoma from other NGON.

Retinal structural changes in patients receiving tamoxifen therapy by spectral-domain optical coherence tomography

Purpose: To evaluate choroidal thickness, ganglion cell complex (GCC) and photoreceptor outer segment (PROS) length were measured in patients with breast cancer undergoing tamoxifen therapy, using spectral-domain optical coherence tomography (SD-OCT); results were compared with those for normal eyes.Materials and methods: Forty-four patients with breast cancer, undergoing tamoxifen therapy, and 41 healthy controls were included in this prospective, comparative study. All participants underwent a complete ophthalmologic evaluation and SD-OCT. Subfoveal, nasal (nasal distance to fovea 500, 1000, 1500 μm), and temporal (temporal distance to fovea 500, 1000, 1500 μm) choroidal thickness measurements were performed using the enhanced depth imaging mode of SD-OCT. Using an Early Treatment Diagnostic Retinopathy Study (ETDRS) circle at the macular level, the automated retinal segmentation software was applied to determine the thickness of the GCC. PROS length was determined manually, as the distance from the inner surface of the ellipsoid zone to the inner surface of retina pigment epithelium.Results: The mean choroidal thickness was statistically greater in the tamoxifen group than controls in all quadrants (p < 0.001 for all quadrants). Of all tamoxifen users (44 eyes of 44 patients), 33 eyes (75%) had uncomplicated pachychoroid (UCP). Pachychoroid pigment epitheliopathy (PPE) was detected in five tamoxifen-group patients (11.3%). Patients with PPE in one eye had UCP in the fellow eye. Central serous chorioretinopathy findings were observed in one patient. Tamoxifen users had statistically lower GCC thickness in all inner rings of the ETDRS inlay and in the nasal outer ring only (p = 0.027, 0.002, 0.002, 0.001, and 0.030, respectively). No statistically significant difference in mean subfoveal PROS length was found between the groups.Conclusions: SD-OCT provides valuable information for identifying structural changes and evaluating ocular findings in patients receiving tamoxifen therapy. Increased choroidal thickness, PPE and thinning GCC were detected in tamoxifen users. These OCT findings may be an early indicator of retinal toxicity for patients undergoing tamoxifen therapy in the follow-up period.

Clinical significance of ectopic inner foveal layers in patients with idiopathic epiretinal membranes

BACKGROUND/OBJECTIVES

To evaluate the relationship between the presence of ectopic inner foveal layers (EIFL), choroidal thickness, and visual acuity (VA) in patients with epiretinal membranes (ERM) staged by spectral-domain optical coherence tomography (SD-OCT).

SUBJECTS/METHODS

A total of 242 eyes of 121 patients with unilateral idiopathic ERM were prospectively evaluated. ERM stages were defined based on the SD-OCT staging system as stage 1: negligible morphological or anatomical disruption, retinal layers, and foveal pit are identified; stage 2: characteristic stretching of the outer nuclear layer, absence of foveal depression, retinal layers are identified; stage 3: continuous EIFL crossing the central foveal area, absence of foveal depression, retinal layers are identified; and stage 4: anatomical disruption of the fovea, continuous EIFL crossing the entire foveal area, retinal layers are distorted.

RESULTS

Of 121 eyes with ERM, 23.1% had stage 1, 26.5% had stage 2, 39.7% had stage 3, and 10.7% had stage 4 disease. VA was better in eyes with stage 1 or 2 ERM than stage 3 or 4 ERM (p < 0.001). VA in logMAR was positively correlated with central foveal thickness (r = 0.557, p < 0.001) and EIFL thickness (r = 0.526, p < 0.001), but not with an outer nuclear layer thickness (r = 0.233, p = 0.123). In multivariate analysis, the presence of EIFL was an independent predictor of VA in eyes with ERM (p < 0.001). The presence and stage of ERM did not have a significant effect on choroidal thickness (p > 0.05).

CONCLUSIONS

The SD-OCT staging system according to the presence of EIFL is effective for grading retinal damage and visual loss in eyes with ERM.

Ocular tuberculosis: Position paper on diagnosis and treatment management

Delay in diagnosis or treatment of ocular tuberculosis can result in loss of vision. However, due to the fact that early diagnosis is rarely achieved, there are still a broad variety of diagnostic and treatment approaches. Our aim was to reach a consensus on the management of diagnosis and treatment of ocular tuberculosis.

METHODS

Critical appraisal of the literature and expert opinion on diagnosis and treatment of ocular tuberculosis.

RESULTS AND CONCLUSION

The currently recommended method for ocular TB diagnosis is screening for tuberculosis in any uveitis of unknown etiology, recurrent or not responding to conventional therapy; in ocular findings highly suggestive of ocular TB and before immunosuppression (particularly biologic agents). TB screening in these cases includes tuberculosis skin testing and interferon gamma testing, along with complete medical history, ophthalmologic evaluation and chest imaging. Positively screened patients should be treated for active tuberculosis with 4 drugs (isoniazid, rifampicin, pyrazinamide and ethambutol) for 6-9 months. Patients should be reviewed at the end of the initiation phase (two months) and at the end of the overall treatment (6-9 months).

Inner-Retinal Irregularity Index Predicts Postoperative Visual Prognosis in Idiopathic Epiretinal Membrane

PURPOSE

To investigate the correlation between the inner-retinal irregularity index and visual outcomes before and after idiopathic epiretinal membrane (ERM) surgery.

DESIGN

Retrospective cohort study.

METHODS

We analyzed 66 eyes of 66 patients with idiopathic ERM. Ophthalmic examinations included best-corrected visual acuity (BCVA) measurements, metamorphopsia assessment, and spectral-domain optical coherence tomography before surgery and 1, 3, and 6 months post-surgery. Correlations between the inner-retinal irregularity index, defined as the length ratio between the inner plexiform layer and retinal pigment epithelium, and visual outcomes before and after ERM surgery were evaluated and compared with the correlation between the central foveal thickness, ganglion cell-inner plexiform layer (GC-IPL) thickness, interdigitation zone defect, and visual outcomes.

RESULTS

Inner-retinal irregularity index and central foveal thickness were significantly correlated with BCVA and metamorphopsia at each follow-up examination (all P < .05). The interdigitation zone defect correlated with BCVA at 3 and 6 months post-surgery (P < .001 and P < .015, respectively). However, GC-IPL thickness was not correlated with visual outcomes at any follow-up examination. The preoperative interdigitation zone defect was correlated with 6-month BCVA (P = .035) and the preoperative inner-retinal irregularity index was significantly correlated with the 6-month BCVA and marginally correlated with the 6-month metamorphopsia (P = .018 and P = .097, respectively).

CONCLUSION

The inner-retinal irregularity index was significantly correlated with visual outcomes before and after ERM surgery. This index can be used as a new surrogate marker for inner-retinal damage and a predictive prognostic marker in ERM.

Elvitegravir/cobicistat-associated toxic optical neuropathy in an HIV-infected patient: a call for caution?

Ocular toxicity may not only be caused by medication overdoses and drug-drug interactions, but also by chronic administration of medications at recommended doses. We describe a case of an HIV-infected patient who experienced significant and sustained bilateral visual loss 2 months after starting treatment with elvitegravir/cobicistat/tenofovir/emtricitabine. Given the absence of any evidence of tenofovir- or emtricitabine-induced optical neuropathy after several years of clinical use, the antiretroviral therapy was promptly changed to tenofovir/emtricitabine plus atazanavir/ritonavir, which led to a progressive improvement in visual acuity. However, visual evoked potentials never returned to normal amplitudes. This is the first report of toxic optical neuropathy associated with the use of elvitegravir/cobicistat. It is imperative to recognize any signs of possible eye toxicity as rapidly as possible, and refer affected patients to an ophthalmologist promptly because early detection and the withdrawal of the offending agent are crucial in reversing this adverse ocular event.

Macular Ganglion Cell Layer and Peripapillary Retinal Nerve Fibre Layer Thickness in Patients with Unilateral Posterior Cerebral Artery Ischaemic Lesion: An Optical Coherence Tomography Study

The purpose of this study is to evaluate the macular ganglion cell layer (GCL) and peripapillary retinal nerve fibre layer (RNFL) thickness in patients with unilateral posterior cerebral artery (PCA) ischaemic lesions using spectral-domain optical coherence tomography (SD-OCT). A prospective, case-control study of patients with unilateral PCA lesion was conducted in the neuro-ophthalmology clinic of Centro Hospitalar Lisboa Central. Macular and peripapillary SD-OCT scans were performed in both eyes of each patient. Twelve patients with PCA lesions (stroke group) and 12 healthy normal controls were included in this study. Peripapillary RNFL comparison between both eyes of the same subject in the stroke group found a thinning in the superior-temporal (p = 0.008) and inferior-temporal (p = 0.023) sectors of the ipsilateral eye and nasal sector (p = 0.003) of the contralateral eye. Macular GCL thickness comparison showed a reduction temporally in the ipsilateral eye (p = 0.004) and nasally in the contralateral eye (p = 0.002). Peripapillary RNFL thickness was significantly reduced in both eyes of patients with PCA compared with controls, affecting all sectors in the contralateral eye and predominantly temporal sectors in the ipsilateral eye. A statistically significant decrease in macular GCL thickness was found in both hemiretinas of both eyes of stroke patients when compared with controls (p < 0.05). This study shows that TRD may play a role in the physiopathology of lesions of the posterior visual pathway.