Intraocular pressure and central visual field of normal tension glaucoma

Border tissue morphology is associated with the pattern of visual field progression in open-angle glaucoma

The etiology of open-angle glaucoma (OAG) is yet unclear. This study investigated possible risk factors, such as the morphology of the border tissue that affect the pattern of visual field (VF) progression in eyes with OAG. 166 eyes of 166 OAG patients with an externally oblique border tissue (EOBT) at least in one direction were included. EOBT was obtained by analyzing enhanced depth imaging spectral-domain optical coherence tomography images. A pointwise linear regression was used to determine VF progression by measuring the deterioration rate of each point in the VF. The odds ratio of VF progression for each risk factor was estimated using logistic regression analysis. Seventy (42.2%) eyes showed VF deterioration. In multivariate analysis, longer follow-up period, higher baseline intraocular pressure (IOP), lower mean ocular perfusion pressure (MOPP), and smaller angular location of the longest EOBT were associated with VF progression (all p values were below 0.05). In the multivariate analysis, the location of the longest EOBT was significantly associated with inferior (p = 0.002) and central (p = 0.017) VF progression. In conclusion, VF progression pattern in OAG eyes is associated with the location of the longest EOBT as well as other known risk factors.

Effects of ocular and systemic factors on the progression of glaucomatous visual field damage in various sectors

BACKGROUND/AIM

To investigate the effects of ocular and systemic risk factors for glaucomatous progression in different sectors of the visual field (VF).

METHOD

409 eyes from 268 patients with 10 reliable VFs from the Japanese Archive of Multicentral Databases in Glaucoma (JAMDIG) were investigated. VFs were divided into six sectors (mean total deviation (mTD)_s20+, mTD_s10-20 and mTD_s0-10, >20°, 10-20° and <10° in the superior hemifield, respectively; and mTD_i20+, mTD_i10-20 and mTD_i0-10, >20°, 10-20° and <10° in the inferior hemifield, respectively). The relationship between sectorial progression rate and eight variables (age, mTD at baseline VF, average intraocular pressure (IOP), SD of IOP, systemic hypertension, migraine, family history of glaucoma and smoking status) was investigated.

RESULT

The mTD progression rate was -0.21 dB/year. Older age was related to progression of mTD_s20+, mTD_s10-20, mTD_i20+ and mTD_i10-20. Mean IOP was not related to progression in any VF sector; however, a larger SD of IOP was related to progression of mTD_s20+, mTD_i0-10, mTD_i10-20 and mTD_i20+. Smoking status was related to progression in all inferior VF sectors (mTD_i0-10, mTD_i10-20 and mTD_i20+).

CONCLUSIONS

Smoking status is related to glaucomatous VF progression in all sectors of the inferior hemifield.

Mitochondrial optic neuropathies - disease mechanisms and therapeutic strategies

Leber hereditary optic neuropathy (LHON) and autosomal-dominant optic atrophy (DOA) are the two most common inherited optic neuropathies in the general population. Both disorders share striking pathological similarities, marked by the selective loss of retinal ganglion cells (RGCs) and the early involvement of the papillomacular bundle. Three mitochondrial DNA (mtDNA) point mutations; m.3460G>A, m.11778G>A, and m.14484T>C account for over 90% of LHON cases, and in DOA, the majority of affected families harbour mutations in the OPA1 gene, which codes for a mitochondrial inner membrane protein. Optic nerve degeneration in LHON and DOA is therefore due to disturbed mitochondrial function and a predominantly complex I respiratory chain defect has been identified using both in vitro and in vivo biochemical assays. However, the trigger for RGC loss is much more complex than a simple bioenergetic crisis and other important disease mechanisms have emerged relating to mitochondrial network dynamics, mtDNA maintenance, axonal transport, and the involvement of the cytoskeleton in maintaining a differential mitochondrial gradient at sites such as the lamina cribosa. The downstream consequences of these mitochondrial disturbances are likely to be influenced by the local cellular milieu. The vulnerability of RGCs in LHON and DOA could derive not only from tissue-specific, genetically-determined biological factors, but also from an increased susceptibility to exogenous influences such as light exposure, smoking, and pharmacological agents with putative mitochondrial toxic effects. Our concept of inherited mitochondrial optic neuropathies has evolved over the past decade, with the observation that patients with LHON and DOA can manifest a much broader phenotypic spectrum than pure optic nerve involvement. Interestingly, these phenotypes are sometimes clinically indistinguishable from other neurodegenerative disorders such as Charcot-Marie-Tooth disease, hereditary spastic paraplegia, and multiple sclerosis, where mitochondrial dysfunction is also thought to be an important pathophysiological player. A number of vertebrate and invertebrate disease models has recently been established to circumvent the lack of human tissues, and these have already provided considerable insight by allowing direct RGC experimentation. The ultimate goal is to translate these research advances into clinical practice and new treatment strategies are currently being investigated to improve the visual prognosis for patients with mitochondrial optic neuropathies.

Comparison of visual field progression in patients with normal pressure glaucoma between eyes with and without visual field loss that threatens fixation

AIM

To compare the frequency and site of visual field progression and changes in visual acuity in patients with normal pressure glaucoma (NPG) with and without pre-existing visual field loss.

METHOD

Patients with normal tension glaucoma were selected who had at least 10 visual fields over 5 or more years of follow up and no other condition that might influence the visual field or visual acuity. Alternate left and right eyes were selected from patients in random order. These eyes were then subdivided according to visual field defect threatening fixation, visual field defect not threatening fixation, and no visual field defect (fellow eyes). Eyes were defined as showing a threat to fixation according to the presence of a visual field defect involving one of more of four paracentral visual field locations. Pointwise linear regression analysis was applied to each visual field series using PROGRESSOR software. Progression of visual field loss was defined as the appearance of a regression slope 1 dB per year or more with a significance of p<0.01, which remained consistent with the addition of two of three successive visual fields to the series. The number of patients showing progression and the number where progression occurred in one of the four paracentral visual field locations was noted. The number of eyes losing two or more lines of Snellen visual acuity over the follow up period was also noted.

RESULTS

174 eyes of 174 patients were selected. 106 eyes had visual field loss threatening fixation, 46 eyes had visual field loss that did not threaten fixation, and 22 were fellow eyes with normal visual fields. The median follow up was 7.2 years. Eight eyes (36.4%) in the "normal visual fields" group, 31 eyes (67.4%) in the "visual field loss away from fixation" group, and 87 eyes (82.1%) in the "threat to fixation" group showed progression in any part of the visual field. Two eyes (9.1%) in the "normal visual fields" group, nine eyes (19.6%) in the "visual field loss away from fixation" group, and 45 eyes (42.5%) in the "threat to fixation" group showed progression at "threat to fixation". The Cox proportional hazards regression model showed an increased risk of progression at any part of the visual field for female sex and a decreased risk for eyes with normal visual fields. For progression at threat to fixation this model showed an increased risk with pre-existing threat to fixation. Eyes from older patients and those that went on to have progressive visual field loss at fixation were more likely to lose two lines of Snellen visual acuity over the follow up period.

CONCLUSION

Since 20-30% of previously field damaged eyes and over 60% without prior field loss fail to demonstrate progressive visual field damage over a long follow up it is recommended that normal pressure glaucoma patients be monitored for progression and that potentially harmful therapy be withheld until progression is demonstrated. Although the presence of visual field loss that threatens fixation does not constitute an increased risk of visual field progression it does indicate an increased risk of further loss of visual field close to fixation which is in turn associated with loss of central acuity. In the light of this finding, patients with visual field loss that threatens fixation should be managed more aggressively.