[Primary open angle glaucoma and sleep apnea syndrome: A review of the literature]

The relationship between glaucoma and Obstructive Sleep Apnea Syndrome (OSAS) has long been discussed, with conflicting study findings. OSAS appears in the most recent studies to be more of an aggravating factor than an independent risk factor for glaucoma. Patients with OSAS may develop a more rapid progression of primary open-angle glaucoma (POAG). OSAS may damage the optic nerve not only by increasing the intraocular pressure (IOP) but also by altering the blood supply to the optic nerve as shown by more recent work with OCT-Angiography. Although the systemic benefits of Continuous Positive Airway Pressure (CPAP) have been demonstrated, few studies have evaluated its effect on the optic nerve. CPAP might act on glaucomatous neuropathy by improving the blood supply to the optic nerve. The study of this mechanism of action might provide new insights into the relationship between OSAS and glaucoma.

[Biomechanics of the lamina cribrosa: A determining factor in glaucomatous neuropathy. A review of the literature]

Glaucoma is a chronic optic neuropathy characterized by progressive sclero-laminar remodeling. The main factor at the origin of these deformations is the intraocular pressure (IOP), the effect of which varies according to the biomechanical properties of the individual lamina cribrosa (LC). In this environment, the LC represents a malleable zone of weakness within a rigid corneoscleral shell. It is a dynamic structure whose movements play a key role in the pathogenesis of glaucoma: displacing it posteriorly, in addition to contributing to the characteristic appearance of glaucomatous cupping, would increase constriction on the nerve fibers and the laminar capillaries. Often incorrectly considered permanent in adults, these deformations have a certain degree of reversibility, which is currently better characterized thanks to progress in imaging techniques. The occurrence of anterior displacement and laminar thickening following a reduction in IOP could thus constitute a good prognostic factor by reducing mechanical stress on this region. These changes would tend to reduce laminar pore tortuosity and shear forces, which are probably key mechanisms of axonal loss in glaucoma.

Optic nerve sheath fenestration: Current status in France and comparison of 6 different surgical approaches

PURPOSE

Optic nerve sheath fenestration (ONSF) is a surgical procedure commonly performed in the Anglo-Saxon countries for the treatment of medically refractory idiopathic intracranial hypertension (IIH). We chose to compare 6 different trans-orbital surgical approaches to ONSF. We also desired to determine the number of optic nerve decompression procedures performed in France in 2019 and 2020.

METHODS

Four fresh frozen orbits were dissected at the University of Nice anatomy laboratory. We performed the following surgical approaches: (i) eyelid crease, (ii) lid-split, (iii) medial transconjunctival with medial rectus disinsertion, (iv) medial transconjunctival without rectus disinsertion, (v) lateral transconjunctival and (vi) lateral orbitotomy. For each surgical approach, we measured the distance between the incision and the optic nerve dura mater. We also extracted data from the French National PMSI (Programme de Médicalisation des Systèmes d' Information) database from January 2019 through December 2020 to determine the annual number of optic nerve decompression procedures.

RESULTS

The lid crease and medial transconjunctival approaches provided the shortest distance to the optic nerve (average 21mm and 24mm, respectively) and the lowest levels of difficulty compared to the other surgical routes. A total of 23 and 45 optic nerve decompressions were performed in France in 2019 and 2020, respectively. Among them, only 2 and 7 procedures, respectively, were performed through a trans-orbital approach.

CONCLUSION

Upper lid crease incision and medial transconjunctival approaches are the most direct and easiest surgical routes when performing an ONSF. We found that ONSF was rarely performed in France. We strongly recommend close cooperation between ophthalmologists, neurologists, neurosurgeons and interventional radiologists.

Pattern of oculomotor and visual function in children with hydrocephalus

PURPOSE

To investigate the ocular motility disturbances, optic nerve changes, and refractive errors in children with or without surgically treated hydrocephalus.

METHODS

This retrospective study included 63 subjects diagnosed with hydrocephalus between 2007 and 2019 at the Baskent University Hospital. Full orthoptic and ophthalmic examination and brain magnetic resonance imaging were performed in all subjects.

RESULTS

The mean age of patients was 68.4±27.6 months, and the mean follow-up time was 21.3±5.2 months. Twenty-one (51.2%) patients had esotropia (ET), and 14 (34.1%) had exotropia (XT). Of the patients with ET, 9 (14.2%) had a sixth nerve palsy. Four patients (6.3%) had a fourth nerve palsy, and 1 had a superior rectus palsy. Eleven patients had manifest, and 2 latent, nystagmus. Thirteen (20.6%) patients had optic disc abnormalities. The mean BCVA was 0.4±0.2 (0.05-1.0) in the right eye and 0.5±0.2 (0.1-1.0) in the left eye. Of the 19 (30.1%) patients who had a significant refractive error, 9 (47.3%) had hyperopia. Thirty-six (57.1%) patients had ventriculoperitoneal shunt surgery, and 11 (30.5%) of them had shunt revision due to occlusion. Ocular motility disorders were found to be significantly more common in patients who underwent single shunt surgery and shunt revision than those who had no surgical procedure (P=0.041and P=0.032, respectively).

CONCLUSION

The evaluation of ocular motility disorders and visual dysfunction in hydrocephalic children can be a source of valuable information when diagnosing and following the disease.

Papilledema secondary to vestibular schwannoma: An atypical case without intracranial hypertension

In most cases, vestibular schwannomas with papilledema are associated with intracranial hypertension secondary to hydrocephalus (obstructive or communicating). We describe the atypical case of a 39-years-old man who presented with bilateral papilledema revealing a vestibular schwannoma, but without hydrocephalus and with normal intracranial pressure. Ophtalmologic signs were completely resolved after tumor removal. The pathophysiological mechanism generally described to explain bilateral papilledema in such cases is tumor-induced hyperproteinorachia. However, in the absence of hydrocephalus or intracranial hypertension, this case raises the question of the mechanisms involved in the visual impairment related to vestibular schwannoma.

Electrophysiological reactions to intraoperative irritation of the optic nerve. Case report and review of possible mechanisms

BACKGROUND

Intraoperative control of optic nerve function conservation during neurosurgical operations currently relies mainly on visual evoked potential monitoring. Unfortunately, this detects peril only when the visual pathways are already compromised, sometimes irreversibly. In contrast, electrophysiological stimulation mapping of the nerves can be a fully preventive measure. However, direct sensory nerve mapping requires the patient to be awake during surgery, which is unfeasible for surgeries targeting the optic nerve area. Another possible approach to sensory nerve mapping involves unconditioned electrophysiological responses evoked by sensory nerve stimulation. The key point for this approach is the possibility of obtaining such responses for a particular sensory nerve under surgical anesthesia.

CASE REPORT

A 52-year-old woman presented with meningioma in the area of right optic nerve and chiasm. She underwent microsurgical removal of the tumor through the transciliary supraorbital approach. During surgery, electrodes at the inferior margin of the right orbit repeatedly recorded electrophysiological reactions following contacts and displacements of the right optic nerve by the surgical instruments.

CONCLUSIONS

The observed reactions suggest that either the unconditioned blink reflex or antidromic electroretinographic response to optic nerve irritation was conserved under total intravenous anesthesia. This observation might be of value for development of intraoperative optic nerve mapping. This in turn could increase patient safety by identifying the exact optic nerve location before any negative impact on it.

[Impact of prematurity on the optic nerve]

INTRODUCTION

Thanks to the progress made in the past few years in pediatric intensive care as well as the increased survival of preterm infants, the consequences of premature birth are increasingly well documented. With regard to ophthalmologic complications, retinopathy of prematurity is well described, but the optic nerve may also be affected. The goal of this study is to compare the optic nerves of preterm infants as a function of their gestational period with a control group of the same age.

MATERIALS AND METHODS

We conducted a case-control study pairing a full-term infant with each preterm infant. Inclusion criteria were: any child from 5- to 10-years-old, separated into three sub-groups according to their degree of prematurity. Variables were: cup/disc ratio, ocular biometry, intraocular pressure and RNFL thickness.

RESULTS

Thirty-seven preterm infants and 37 controls were included in the study. The mean age at the time of inclusion was 7.05 years for the preterm group and 7.19 years for the control group. No significant difference was observed in axial length or spherical equivalent (P=0.31 and P=0.98, respectively). No significant difference was observed in pachymetry or intraocular pressure (P=0.28 and P=0.22, respectively). We observed a significant increase of 0.1 in the cup/disc ratio of the preterm group compared to the control group (P<0.05). The preterm group cup/disc ratio was 0.36 versus 0.27 for the control group. No significant difference was observed in the 7 quadrants of RNFL between the two groups. However, when comparing infants born before 28 weeks gestation with the control group, we observed a mean decrease of 14.5 microns in the superior temporal sector (P=0.04), a 9 micron decrease in the global thickness G (P=0.03) and a 12.7 micron decrease in the nasal sector (P=0.01).

CONCLUSIONS

In the case of the studied children (aged 5 to 10), the reduced RNFL fiber thickness is a phenomenon dependent essentially on the stage of prematurity. It would be useful to follow these preterm populations over the long term and to compare them to a matched control group to be able to obtain functional results.

Multimodal imaging in optic nerve melanocytoma: Optical coherence tomography angiography and other findings

PURPOSE

To evaluate optical coherence tomography (OCT), fundus autofluorescence (FAF) imaging and optical coherence tomography angiography (OCTA) as diagnostic tools in optic disc melanocytoma (ODM) and study the differences in peripapillary and macular vascular density in eyes with ODM using OCTA.

METHODS

Patients with ODM were enrolled in this case series. Each patient underwent evaluation of best-corrected visual acuity, slit-lamp biomicroscopy, fundus examination, fundus photography, standard visual field testing, spectral domain OCT, ultrasound B-scan examination, FAF, fluorescein angiography and OCTA.

RESULTS

Eight patients (three males and five females) with ODM (9 eyes) were enrolled. The largest ODM presented a nodular appearance with a hyper-reflective tumor surface and a posterior optical shadow on OCT. FAF images showed hypoautofluorescence of the tumor with well-defined outlines. Analysis of optic nerve vascular area showed decreased values in the radial peripapillary capillary plexus (3 of 5) and the outer retinal plexus (4 of 5) in the eyes with ODM. In contrast, the ODM eyes had a higher macular vascular area in the deep capillary plexus in 4 of 6 patients.

CONCLUSIONS

ODM may be associated with changes in peripapillary and macular perfusion, with an increase in peripapillary vascularization being a possible risk factor for growth. OCTA might be a helpful objective method in the analysis of changes in flow in patients with ODM.

[Congenital abnormalities of the optic disc]

Congenital abnormalities of the optic disc are not uncommon in clinical practice and should be recognized. Size abnormalities of the optic disc include optic disc aplasia, hypoplasia, megalopapilla, and optic disc cupping in prematurity. Among congenital excavations of the optic disc head, morning glory disc anomaly and optic disc pit can be complicated by serous retinal detachment; the papillorenal disc is an association of bilateral optic disc cupping and renal hypoplasia which should be ruled out; optic disc coloboma is caused by an abnormal closure of the embryonic fissure and can be complicated by choroidal neovascularization and retinal detachment. Other abnormalities that will be discussed are congenital tilted disc syndrome, duplicity of the optic disc head, congenital pigmentation of the optic disc head and myelinated retinal nerve fibers. All of these abnormalities can be associated with syndromes and neurological diseases, as well as other potentially blinding ophthalmological defects which can be secondarily complicated by amblyopia, strabismus and nystagmus. Thus, they should be recognized in order to plan for appropriate follow-up.

Gene therapy for mitochondrial diseases: Leber Hereditary Optic Neuropathy as the first candidate for a clinical trial

Mitochondrial disorders cannot be ignored anymore in most medical disciplines; indeed their minimum estimated prevalence is superior to 1 in 5000 births. Despite the progress made in the last 25 years on the identification of gene mutations causing mitochondrial pathologies, only slow progress was made towards their effective treatments. Ocular involvement is a frequent feature in mitochondrial diseases and corresponds to severe and irreversible visual handicap due to retinal neuron loss and optic atrophy. Interestingly, three clinical trials for Leber Congenital Amaurosis due to RPE65 mutations are ongoing since 2007. Overall, the feasibility and safety of ocular Adeno-Associated Virus delivery in adult and younger patients and consistent visual function improvements have been demonstrated. The success of gene-replacement therapy for RPE65 opens the way for the development of similar approaches for a broad range of eye disorders, including those with mitochondrial etiology such as Leber Hereditary Optic Neuropathy (LHON).