Axonal loss from acute optic neuropathy documented by scanning laser polarimetry

One year monitoring of retinal morphologic and functional changes in traumatic optic neuropathy patients

BACKGROUND

To analyze the morphologic and functional change in traumatic optic neuropathy (TON) divided by the mechanism of optic nerve injury.

METHODS

A retrospective analysis of 58 patients who were diagnosed as monocular TON from February 2015 to August 2021 was conducted at in CHA Bundang Medical Center in Seongnam, South Korea. The patients visited the clinic of the department of ophthalmology for more than 6 months and at least 4 times during this period.

RESULTS

44 patients were classified as blunt TON patients, and 14 patients were surgical TON patients. The visual acuity showed significant decrease in traumatic eyes at the first visit after injury compared to fellow eyes and maintained the injured status during the 1-year follow-up period in blunt TON. In surgical TON, the visual acuity slightly improved during 1 month follow-up period. RNFL thickness tended to be decreased at 1 month after first visit blunt TON patients, which was earlier than surgical TON patients. GCIPL thickness showed earlier decreased than RNFL thickness in both blunt and surgical TON patients.

CONCLUSIONS

In both blunt and surgical TON eyes, there was a notable thinning in both RNFL and GCIPL, with particularly remarkable reduction in GCIPL in early phase. Therefore, analyzing each retinal layer thickness using OCT in conjunction with assessing visual function would be necessary. This combined approach is not only crucial for understanding clinical courses of each TON, but also predicting the morphological and functional deteriorations in TON.

Afferent Visual Manifestations of Traumatic Brain Injury

Traumatic brain injury (TBI) causes structural and functional damage to the central nervous system including the visual pathway. Defects in the afferent visual pathways affect visual function and in severe cases cause complete visual loss. Visual dysfunction is detectable by structural and functional ophthalmic examinations that are routine in the eye clinic, including examination of the pupillary light reflex and optical coherence tomography (OCT). Assessment of pupillary light reflex is a non-invasive assessment combining afferent and efferent visual function. While a assessment using a flashlight is relatively insensitive, automated pupillometry has 95% specificity and 78.1% sensitivity in detecting TBI-related visual and cerebral dysfunction with an area under the curve of 0.69-0.78. OCT may also serve as a noninvasive biomarker of TBI severity, demonstrating changes in the retinal ganglion cell layer and nerve fiber layer throughout the range of TBI severity even in the absence of visual symptoms. This review discusses the impact of TBI on visual structure and function.

Different follow-up OCT analyses of traumatic optic neuropathy. A case report

Purpose

Optical coherence tomography (OCT) is established as a promising technology for assessing the optic nerve atrophy progression after trauma. However, reports on the effectiveness and sensitivity of ganglion cell layer (GCL) and Bruch's membrane opening-minimum rim width (BMO-MRW) for studying this damage course over time are still lacking.

Observations

A 53-year-old man with severe optic nerve trauma had repeated OCT scans of the retinal nerve fiber layer (RNFL), GCL and BMO-MRW during 12 months after the injury. There was gradual damage in all measurements. Interestingly, BMO-MRW was the first analysis affected whilst GCL showed the greatest damage over time.

Conclusions

Our outcomes suggest that OCT might be able to assess axonal loss after traumatic optic neuropathy. BMO-MRW measurement might be more sensitive than other analyses in the first two weeks after trauma and GCL might better monitor belated damage. Thus, it might be possible to combine all these sets of measurements to increase diagnostic sensitivity an specificity.

Nerve fiber layer thickness in eyes treated with red versus green laser in proliferative diabetic retinopathy: short-term results

PURPOSE

To evaluate changes of retinal nerve fiber layer (RNFL) thickness after panretinal photocoagulation (PRP) in red versus green laser-treated eyes.

PROCEDURE

This is a prospective, randomized, fellow-eye controlled clinical trial conducted on 60 eyes of 30 patients (mean age 52.3 ± 7.8 years; 57% male) with early- to high-risk proliferative diabetic retinopathy type II diabetes who received standard red or green laser treatment. Scanning laser polarimetry (GDx) was performed to evaluate RNFL thickness at baseline and at week 6.

RESULTS

Only 22 patients (44 eyes) could perform reliable GDx tests. At week 6 after PRP, the RNFL thickness increased by an average of 3.35 ± 9.18 µm (p = 0.02) and 2.08 ± 4.75 µm (p = 0.04) in the red and green laser groups, respectively. There was no significant correlation between changes in RNFL thickness and the number of laser burns, age, HbA1c or blood pressure. The difference in the change of the RNFL thickness between the red and green laser groups was not significant (p = 0.8).

CONCLUSION

Though RNFL thickness was increased significantly 6 weeks after PRP with red and green laser in comparison to baseline, there was no significant difference in RNFL thickness between red and green laser groups.

Evaluation of retinal nerve fiber layer and ganglion cell complex thickness after ocular blunt trauma

PURPOSE

To evaluate circumpapillary retinal nerve fiber layer (cpRNFL) and ganglion cell complex (GCC) after ocular blunt trauma.

METHODS

Best-corrected visual acuity (BCVA), cpRNFL and GCC were evaluated by RTVue-100 OCT in all consecutive patients with previous monocular blunt trauma seen between January 2012 and December 2012.

RESULTS

Twenty-two patients (11 females, 11 males, mean age 43.9 ± 14.2 years) were included in the study. Patients were seen after a mean of 8.42 ± 13.3 (range, 0.08-55.3) years from ocular blunt trauma. BCVA was normal in 11 cases and was less than 0.4 LogMAR in all cases. In 9/22 patients (40.9%), cpRNFL and GCC were reduced, whereas in one case an isolated reduction of GCC with normal cpRNFL was present. In patients with reduction of cpRNFL and GCC, mean BCVA was 0.17 ± 0.17 LogMAR. In 6/9 patients (66.6%) with cpRNFL and GCC reduction, BCVA was ≤ 0.1 LogMAR.

CONCLUSION

cpRNFL and GCC reduction may be present after ocular blunt trauma and may be associated with preserved visual acuity.

Scanning laser polarimetry, but not optical coherence tomography predicts permanent visual field loss in acute nonarteritic anterior ischemic optic neuropathy

PURPOSE

Scanning laser polarimetry (SLP) reveals abnormal retardance of birefringence in locations of the edematous peripapillary retinal nerve fiber layer (RNFL), which appear thickened by optical coherence tomography (OCT), in nonarteritic anterior ischemic optic neuropathy (NAION). We hypothesize initial sector SLP RNFL abnormalities will correlate with long-term regional visual field loss due to ischemic injury.

METHODS

We prospectively performed automated perimetry, SLP, and high definition OCT (HD-OCT) of the RNFL in 25 eyes with acute NAION. We grouped visual field threshold and RNFL values into Garway-Heath inferior/superior disc sectors and corresponding superior/inferior field regions. We compared sector SLP RNFL thickness with corresponding visual field values at presentation and at >3 months.

RESULTS

At presentation, 12 eyes had superior sector SLP reduction, 11 of which had inferior field loss. Six eyes, all with superior field loss, had inferior sector SLP reduction. No eyes had reduced OCT-derived RNFL acutely. Eyes with abnormal field regions had corresponding SLP sectors thinner (P = 0.003) than for sectors with normal field regions. During the acute phase, the SLP-derived sector correlated with presentation (r = 0.59, P = 0.02) and with >3-month after presentation (r = 0.44, P = 0.02) corresponding superior and inferior field thresholds.

CONCLUSIONS

Abnormal RNFL birefringence occurs in sectors corresponding to regional visual field loss during acute NAION when OCT-derived RNFL shows thickening. Since the visual field deficits show no significant recovery, SLP can be an early marker for axonal injury, which may be used to assess recovery potential at RNFL locations with respect to new treatments for acute NAION.

Interpretation of RNFLT values in multiple sclerosis-associated acute optic neuritis using high-resolution SD-OCT device

PURPOSE

Optical coherence tomography (OCT) has emerged as the technique of choice in measuring the retinal nerve fibre layer (RNFL) quantitatively. It is suggested that RNFL reduction may correlate with lesion burden and diffuse axonal degeneration in the whole CNS of patients with multiple sclerosis (MS). However, RNFL changes because of optic neuritis (ON) must be taken into account.

METHODS

Twenty-three patients with acute ON (46 eyes) associated with clinical definite MS (23 ON eyes, 23 fellow eyes) and 23 sex- and age-matched healthy controls were studied. Retinal nerve fibre layer thickness (RNFLT) was measured at baseline, using a high-resolution spectral domain OCT (SD-OCT) applying circular, peripapillary OCT scans with a novel eye-tracking mechanism.

RESULTS

The internal OCT software was able to identify RNFL atrophy in three out of five of the acute ON eyes and one out of four of the fellow eyes with previous ON episodes. Retinal nerve fibre layer thickness of two ON (8.7%) and five fellow eyes (21.7%) was overestimated, thus located within the 95% and 5% confidence interval of the company standard values (not marked pathologic). In contrast, our comparison with age- and sex-matched controls revealed RNFL atrophy suggestive of prior, clinically silent RNFL loss in ON and fellow eyes (30.4%).

CONCLUSION

Retinal nerve fibre layer thickness measurements at a single time-point seem to have a limited role in detecting prior clinically silent optic nerve injury. Our data suggest that affected eyes should be compared with the fellow eyes and a sufficient number of age- and sex-matched controls to allow the detection of even subtle RNFL changes at baseline. The role of OCT for disease monitoring of MS must be evaluated in detail, as ON is often the initial symptom of MS.

Scanning laser polarimetry reveals status of RNFL integrity in eyes with optic nerve head swelling by OCT

PURPOSE

Optical coherence tomography (OCT) shows retinal nerve fiber layer (RNFL) thickening in optic nerve head (ONH) swelling, but does not provide information on acute axonal disruption. It was hypothesized that scanning laser polarimetry (SLP) compared with OCT might reveal the status of axon integrity and visual prognosis in acute RNFL swelling.

METHODS

Threshold perimetry, OCT, and SLP were used to prospectively study eyes with papilledema (24), optic neuritis (14), nonarteritic anterior ischemic optic neuropathy (NAION) (21), and ONH swelling (average RNFL value by OCT was above the 95th percentile of controls at presentation). Regional RNFL was judged reduced if the quadrant measurement was below the fifth percentile of controls.

RESULTS

At presentation, average RNFL by OCT was similar for eyes with papilledema and NAION (P = 0.97), and reduced for optic neuritis. Average RNFL by SLP was slightly increased for papilledema and optic neuritis, and reduced for NAION (P = 0.02) eyes. The RNFL by SLP was reduced in at least one quadrant in 1 eye with papilledema, 1 eye with optic neuritis, and in 13 eyes with NAION. In NAION eyes, quadrants with reduced SLP had corresponding visual field loss that did not recover. By one month, eyes with NAION showed RNFL thinning by OCT (7/17 eyes) and by SLP (14/16 eyes) in contrast to optic neuritis (by OCT, 0/12, P = 0.006; and by SLP, 1/12, P = 0.0004).

CONCLUSIONS

OCT and SLP revealed different aspects of RNFL changes associated with ONH swelling. OCT revealed thickening due to edema. SLP revealed a decrease in retardance in eyes with axonal injury associated with visual field loss, which is unlikely to recover.

Diagnosing glaucoma progression: current practice and promising technologies

PURPOSE OF REVIEW

An update on recent work is provided that has broadened our understanding of the evaluation of visual function and structure, and their use in evaluating glaucoma progression.

RECENT FINDINGS

The challenge of determining visual-field progression and the implications of long-term fluctuation are reviewed and data to support the magnitude of the fluctuation are cited. The use of confirmatory testing can limit the over diagnosis of glaucoma progression. Focusing visual-field testing on the locations of present scotomas or using frequency doubling technology may provide new approaches to assessing visual function. New standardized techniques to interpret visual fields, including neural networks, unsupervised machine learning and pointwise linear regression, may provide more quantitative means for visual-field interpretation. These techniques, along with structural evaluation of the optic nerve and nerve fiber layer, are essential in glaucoma management. Optic-nerve-head photography is still a mainstay in evaluating glaucoma progression, although many technologies including scanning laser tomography, scanning laser polarimetry and optical coherence tomography offer more quantitative means to follow structural change. These modalities, in different ways, show promise in providing additional information regarding the stability of glaucoma.

SUMMARY

Identifying the functional visual component as well as structural changes is essential in evaluating glaucoma progression. New techniques of testing and evaluating visual fields, the optic-nerve head, and the retinal nerve fiber layer offer exciting opportunities to more accurately identify glaucoma progression, and are likely to become more central as imaging devices and software support develop further.

Nerve fibre layer analysis with GDx with a variable corneal compensator in patients with multiple sclerosis

PURPOSE

To evaluate the ability of GDx with variable corneal compensator (VCC) compared to visual-evoked potentials (VEPs) and standard automated perimetry (SAP) in the detection of early optic nerve damage in patients with multiple sclerosis (MS).

METHODS

46 eyes of 23 MS patients were included. Ten of them had a history of acute retrobulbar optic neuritis. A control group of 20 normal subjects was also included. All subjects underwent a complete ophthalmological examination and testing with SAP, GDx VCC and VEPs.

RESULTS

19 eyes (41.3%) were abnormal with GDx VCC compared to 38 eyes (82.6%) with SAP and 31 (64.4%) with VEPs. In the optic neuritis group, 9 eyes (69.2%) had optic nerve pallor; SAP was abnormal in 8 of these eyes (61.5%) while VEPs and GDx VCC were abnormal in 6 eyes (46.1%). 2/20 eyes (10.0%) in the control group gave a false-positive abnormal result with SAP. GDx VCC and VEP were normal for all the eyes in the control group.

CONCLUSIONS

GDx VCC is less able to detect early defects in MS patients compared to the currently used standard techniques of SAP and VEPs.

Advances in Imaging of the Optic Disc and Retinal Nerve Fiber Layer

In the past decade, three technologies for imaging the optic disc and retinal nerve fiber layer have become commercially available: 1) confocal scanning laser tomography with the Heidelberg retinal tomograph; 2) confocal scanning laser polarimetry with the GDx VCC; and 3) optical coherence tomography with the Stratus OCT. Each uses different principles of physics. Understanding the merits and limitations of each of these technologies requires familiarity with the principles of operation of each device. This knowledge should be considered a prerequisite for the appropriate clinical utilization of these devices and for accurate interpretation of their results.

Quantitative analysis of axonal loss in band atrophy of the optic nerve using scanning laser polarimetry

AIMS

To measure axonal loss in patients with band atrophy from optic chiasm compression using scanning laser polarimetry (GDx, Laser Diagnostic Technologies, Inc, San Diego, CA, USA) and to evaluate the ability of this instrument to identify this pattern of retinal nerve fibre layer (RNFL) loss.

METHODS

19 eyes from 17 consecutive patients with band atrophy of the optic nerve and permanent temporal hemianopia due to chiasmal compression, and 19 eyes from an age and sex matched control group of 17 healthy individuals were prospectively studied. All patients were submitted to an ophthalmic examination including Goldmann perimetry and evaluation of the RNFL using scanning laser polarimetry. Mean RNFL thickness around the optic disc were compared between the two groups. The diagnostic performance of the deviation from normal analysis provided by the GDx software was also assessed.

RESULTS

The peripapillary RNFL thickness (mean (SD)) of eyes with band atrophy was 47.9 (7.63) micro m, 37.1 (8.48) micro m, 57.0 (9.31) micro m, and 37.2 (8.86) micro m in the superior, temporal, inferior, and nasal regions, respectively. The total average was 43.7 (12.0) micro m. In the control group, the corresponding values were 71.1 (12.2) micro m, 40.4 (10.9) micro m, 85.4 (14.0) micro m, and 49.8 (10.1) micro m. The total average measured 67.9 (11.2) micro m. The measurements from eyes with optic atrophy were significantly different from those in the control group in all regions but the temporal. The deviation from normal analysis provided by the GDx software failed to identify the majority of abnormalities in the temporal and nasal regions of patients with band atrophy.

CONCLUSIONS

Scanning laser polarimetry was able to identify axonal loss in the superior, inferior, and nasal regions, but failed to detect it in the temporal region of the optic disc, despite the fact that this area was clearly altered in eyes with band atrophy. This examination also showed poor sensitivity to detect axonal loss in the nasal region when GDx software analysis was used. The results of this study emphasise that RNFL evaluation using scanning laser polarimetry should be interpreted with caution in the study of eye diseases that lead to axonal loss predominantly in the nasal and temporal areas of the optic disc.