The pupil in congenital third nerve misdirection syndrome

Analysis of Retinal Nerve Fibre Thickening in Progressive and Non-progressive Non-arteritic Anterior Ischaemic Optic Neuropathy Using Optical Coherence Tomography

The study aims to investigate the longitudinal changes in the circumpapillary retinal nerve fibre layer thickness (cpRNFLT) in progressive and non-progressive non-arteritic anterior ischaemic optic neuropathy (NAION). This retrospective observational case series study analysed 17 eyes with NAION. Patients sustaining any additional visual loss (additional decrease in visual acuity (VA) ≥0.2 logMAR) within two months after initial onset of symptoms were classified as having progressive NAION. Of the 17 eyes with NAION, 13 (76.5%) were diagnosed as non-progressive and 4 (23.5%) were diagnosed as progressive. Compared with control eyes, eyes with non-progressive NAION showed greater cpRNFLT in all four optic disc quadrants at the initial visit (temporal and superior: P < .001; nasal and inferior: P = .002). In contrast, compared with control eyes, eyes with progressive NAION showed greater cpRNFLT in the superior and nasal quadrants (P = .004 and 0.028, respectively), but not in the temporal and inferior quadrants. During progression, eyes with progressive NAION showed a significant increase in cpRNFLT in the inferior quadrants; furthermore, there was significant increase in cpRNFLT in the nasal sector before visual loss developed after the initial visit. Progressive NAION showed development of the disc swelling from the superior to inferior portion of optic disc via the nasal swelling, suggesting that swollen axons in one ischaemic part may lead to secondary vascular infarction in another part of the optic disc. This enlargement could constitute the earliest sign of progressive NAION.

Unraveling the Enigma of Nonarteritic Anterior Ischemic Optic Neuropathy

Non-arteritic anterior ischemic optic neuropathy (NAON) is the second most common optic neuropathy in adults. Despite extensive study, the etiology of NAION is not definitively known. The best evidence suggests that NAION is caused by an infarction in the region of the optic nerve head (ONH), which is perfused by paraoptic short posterior ciliary arteries (sPCAs) and their branches. To examine the gaps in knowledge that defies our understanding of NAION, a historical review was performed both of anatomical investigations of the ONH and its relevant blood vessels and the evolution of clinical understanding of NAION. Notably, almost all of the in vitro vascular research was performed prior our current understanding of NAION, which has largely precluded a hypothesis-based laboratory approach to study the etiological conundrum of NAION. More recent investigative techniques, like fluorescein angiography, have provided valuable insight into vascular physiology, but such light-based techniques have not been able to image blood vessels located within or behind the dense connective tissue of the sclera and laminar cribrosa, sites that are likely culpable in NAION. The lingering gaps in knowledge clarify investigative paths that might be taken to uncover the pathogenesis of NAION and possibly glaucoma, the most common optic neuropathy for which evidence of a vascular pathology also exists.

Thrombophilic risk factors in the pathogenesis of non-arteritic anterior ischemic optic neuropathy patients

BACKGROUND

Non-arteritic anterior ischemic optic neuropathy (N-AION) is caused by acute ischemic infarction of the optic nerve head, supplied by the posterior ciliary arteries. Thrombophilia is the tendency/predisposition to vascular thromboses of arteries and veins, and the existence of thrombophilic risk factors leads to blood hypercoagulability and potentially increased risk for thromboses.

OBJECTIVES

To investigate whether there is an association between N-AION and a wide spectrum of thrombophilic risk factors.

PATIENTS AND METHODS

Seventy-seven consecutive cases of confirmed N-AION and 60 age- and sex-matched consecutive controls constituted the study group. Fibrinogen levels, deficiency of proteins C, S, ATIII, lupus anticoagulant, activated protein C resistance, factor V Leiden, factor V H1299R, factor II G20210A, MTHFR C677T, MTHFR A1298C, GPIIIa A1/A2, and ACE I/D polymorphisms were analysed.

RESULTS

Statistical analysis of the plasma proteins in our study demonstrated that the only significant difference was the one concerning protein S levels. In particular, the mean value for N-AION patients was 78.8% +/- 21.2, and for the control group the mean value was 88% +/- 21.2 (p = 0.013). Despite the above-mentioned result, there was not any statistical difference between the two subgroups regarding actual protein S deficiency, as 9/77 (11.7%) patients and 4/60 (6.7%) controls had protein S levels below 60% (p = 0.32). In our study sample, homozygosity for MTHFR C677T polymorphism in the study group as a whole, and the presence of at least one A2 allele of GPIIIa in the subgroup of male patients as compared to healthy male controls, proved to be the most significant thrombophilic risk factors, with odds ratios of 16.78 (95% C.I 0.96-294.42, p = 0.054) and 4.6 (95% C.I 1.52-13.88, p = 0.007) respectively.

CONCLUSION

Screening for these polymorphisms would probably constitute a valuable procedure in N-AION patients, as they may have an important contribution to the pathogenesis of the disease.

Coagulation abnormalities in ischaemic optic neuropathy

The aetiology of non-arteritic ischaemic optic neuropathy (ION) is multifactorial with local anatomical and systemic haemodynamic abnormalities both playing a role. A careful search for treatable vascular disease risk factors is required to allow rational therapy, to optimise the visual prognosis and to allow new insights into pathogenesis. We describe 7 cases in which there was an associated thrombophilic (prothrombotic) state; 4 had deficiencies of the physiological anticoagulants proteins C and S and antithrombin III and 2 had anti-phospholipid antibody (lupus anticoagulant) syndromes. A further patient had reduced levels of the physiological fibrinolytic agent tissue plasminogen activator (t-PA). In 5 patients other risk factors for small vessel occlusive disease were also present, and 4 had recurrent episodes of ION in the same eye. The visual prognosis in these patients may be improved by anticoagulation with warfarin.

Structural factors in the pathogenesis of ischemic optic neuropathy

Some patients with nonarteritic ischemic optic neuropathy have no signs or symptoms of systemic vascular disease; therefore, nonvascular factors may play a role in the pathogenesis of this syndrome. We observed that the average cup-disk ratio of the unaffected optic disks in a group of patients with ischemic optic neuropathy was significantly (P = .005) smaller than the average ratio in a group of age-matched controls (0.36 +/- 0.19 vs 0.21 +/- 0.16). Fourteen of 30 patients but only two of 29 controls had cup-disk ratios equal to or less than 0.1. Mechanical factors, such as constriction of axons as they traverse the scleral canal, may contribute to the pathogenesis of ischemic optic neuropathy.