(IGR: 12-1) | International Glaucoma Review #

Top-ten Australian and New Zealand Glaucoma Interest Group Meeting
Australian and New Zealand Glaucoma Interest Group Meeting

Rates of progressive functional loss as measured by standard automated perimetry (SAP) were significantly associated with rates of structural loss in glaucoma, as measured by retinal nerve fiber layer thickness with scanning laser polarimentry. The association varied according to the level of disease severity. Due to the logarithmic scaling of visual field data, rates of SAP loss tended to be deceptively low in early stages of the disease, whereas for moderate and advanced cases, rates of SAP loss tended to be greater than those of RNFL loss.(Felipe Medeiros, La Jolla, USA)

The complex cycle of cell activation and apoptosis which regulates the permeability of bleb capsules around Molteno implants can be subdivided into two processes: 1) an inflammatory fibroproliferative; 2) an apoptotic fibrodegenerative process, which actively inhibits the fibroproliferative process. Techniques which suppress the fibroproliferative process include the use of oral anti-inflammatory agents, temporary occlusion of the drainage tube of an implant by a vicryl ligature and the use of appropriate hypotensive agents during the early postoperative period. Techniques which increase the apoptotic fibroproliferative process include modifications of the plate of the Molteno3 implant to concentrate the initial drainage of aqueous into a small area and the injection of bevacizumab (Avastin) into the vitreous cavity where it forms a depot from which Avastin drains into the bleb cavity where it blocks new vessel formation.Tony Molteno (Dunedin, New Zealand)

Greater loss in function, delayed recovery and increase oxidative stress in response to short-term IOP elevation were reported in two mouse models with mild mitochondrial dysfunction, one due to a faulty mtDNA replication enzyme, the other due to 'mismatching' of nuclear and mtDNA genomes, compared to age and sex matched controls. Mitochondrial reserve is an important factor in RGC susceptibility to oxidative stress induced by IOP elevation. (Jonathan Crowston, Melbourne, Australia)

The initial site of injury to the retinal ganglion cell axon in glaucomatous optic neuropathy is believed to occur at the lamina cribrosa. Evidence is accumulating that astrocytic responses in the optic nerve head may underlie the cellular changes that lead to axonal damage. In the human optic nerve head, astrocytes are extensively coupled via gap junctions. These intercellular channels may allow the passage of apoptotic factors between cells and have been implicated as a mediator of neuronal degeneration in the central nervous system. Using immunohistochemical techniques, a marked increase in connexin43 immunoreactivity was detected in the lamina cribrosa of glaucomatous eyes compared to age-matched donors. Connexin43 may represent a potential target for neuroprotective therapies. (Nathan Kerr, Auckland/Melbourne, New Zealand/Australia)

A modified, semi-automated technique of sequential peripheral laser iridotomy (LI) and peripheral iridoplasty using 532-nm frequency-doubled Nd:YAG Pattern Scan Laser proved convenient, effective and safe in Asian eyes with thick, dark irides. Twenty eight (28) eyes were treated with LI using the 2x2 array of photocoagulation pattern mode that stretched the iris prior to perforation with the single spot pattern and subsequent enlargement with 1064-nm Nd-YAG. Seventeen (17) eyes received iridoplasty using the single arc of three spots from the glaucoma pattern mode applied on the outer third of the iris circumference. Mild inflammation (+1 to +2 cells) was noted on first day post laser lasting for one week. No other complications were observed. (Paul Chew, Singapore)

Microglia are the immunocompetent cells of the CNS. In a rat laser model of experimental glaucomatous optic neuropathy increased microglial activity is a prominent component of the pathology in the anterior visual pathway. This is an early marker of disease and strongly correlates with axonal injury. (Bob Casson, Adelaide, Australia)

GONE is an online testing and teaching system for optic disc examination. It has now been running for two years and over 1,000 people have registered. Presented were the disc images that experts had the lowest levels of agreement on. It is interesting to see those features that produce problems amongst experts. Further work will clarify what features of the discs cause the most problems. (Michael Coote, Melbourne, Australia)

In a systematic review of thirty-seven papers describing heritability for an ophthalmic trait relating to glaucoma, the highest reported heritability for an ophthalmic trait is 0.95 for central corneal thickness, indicating that observed variation in this parameter is largely governed by genetic factors. Over 60% of the studies employed a twin study design and a similar percentage utilized variance components methods and structural equation modelling (SEM) to derive their heritability values. Many of the estimates are in the moderate to high range, but to date the majority of genetic variants accounting for these findings have not been uncovered, hence much work remains to be undertaken to fully elucidate their molecular etiology. (David Mackey, Perth, Australia)

The software of the New Visual Field Index was most accurate when the predicted VFI was > 90% or the slope of the linear regression was > -1.5. Laser trabeculoplasty did not significantly influence the results, contrary to that seen with trabeculectomy, which resulted in a higher observed VFI than that predicted. (Renee Talbot, Sydney/Vancouver, Australia/Canada)

Measuring IOP using Goldmann applanation tonometry [GAT] can be influenced by central corneal thickness [CCT]. IOP measurements from Pascal Dynamic Contour Tonometer [PDCT] were used as reference. Adjusting GAT IOP for CCT, using four different formulae, increased the risk of making errors of clinically significant magnitude more than using unadjusted GAT IOP value. CCT may be useful in population analyses, CCT-based correction formulae should not be applied to individuals. (Sarena Park, Wellington, New Zealand)