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ANZGC meeting by Anne Brooks
Anne Brooks
We were privileged to hear three papers which were the product of Tony Molteno's unrivalled experience with glaucoma implants. His first paper entitled "Neovascular glaucoma - long term results" gave the long-term results of a prospective study of 92 patients (107 eyes) with neovascular glaucoma drained by a Molteno implant between 1978 and 1998. The main conclusion was that neovascular glaucoma is the end result of widespread, vascular disease which has ocular, regional and general metabolic components, all of which must be considered and treated in order to obtain and maintain good long-term visual results.
Tony Molteno's second paper entitled "Combined cataract extraction and draining implants - long-term results" gave the results of prospective study of 56 consecutive cases of primary glaucoma with cataract treated by a combined operation of cataract extraction with insertion of a Molteno implant between 1986 and 1998. The main conclusion was that this technique, which separates the onset of drainage from the cataract extraction by approximately four weeks, confers very significant advantages of avoidance of postoperative complications and control of IOP.
In his third paper entitled "Clinical control of bleb fibrosis after drain implants" a prospective study of 500 consecutive operations for the insertion of Molteno implants was analyzed to provide information on the factors which influences bleb function. The main conclusions were that the most important factors are the age of the patients and the severity of the glaucoma, and that bleb function can be modulated by a surgical technique of performing the bleb combined with perioperative control of IOP. Long-term function is amenable to pharmacological manipulation.
Our guest lecturer, Don Mickler from Los Angeles, spoke first on trabeculectomy complications and management. He described a technique of tight wound closure and laser suture lysis or removable suture to titrate (control) IOP postoperatively. Using a sharply outlined trapezoidal flap (3 × 2 mm) and minimal cautery, only two 10-0 nylon sutures usually sufficed for 'tight' wound closure. It is easier and probably less dangerous, to deal with transient postoperative high IOP than to risk hypotony. Interventions to lower IOP and maintain a bleb postoperatively may include mechanical wound distortion (burping the wound), ocular massage, paracentesis, restarting medication, and eventually (six to ten days postoperatively) suture release or suture lysis. Frequent follow-up is necessary. By his definition, 40-50% trabeculectomies are complicated during the first six weeks. He further discussed preoperative and intraoperative issues, postoperative and surgical problems.
Don Minckler next gave a paper complementing Tony Moteno's papers entitled "Update on aqueous shunts (drainage devices)" which provided a current perception on pathophysiology, clinical indications and applications, advantages and disadvantages of various design, as well as complications unique to glaucoma drainage devices.
Don Minckler finally spoke on "Ophthalmology - The Journal, How it works and where its going". This discussion provided a brief summary of Ophthalmology's history, how the editorial office currently functions with regard to peer review, the publication process, and dealing with what is anticipated in the coming years with regard to electronic publication. An update on modification of the structured abstract and application of a new study design scheme was presented. Trends in the study designs utilized and in the geographic origins of published articles during the previous decade were summarised.
In the section on Surgery, Justin Mors spoke on "Beta radiation as an adjunct to low risk trabeculectomy". He concluded that, in a prospective randomised trial of 65 eyes of low risk patients, there was no significant difference in outcome with or without application of a single intraoperative dose of 750 rads of intraoperative beta radiation.
Mark Walland spoke on the mechanisms of the lowering of IOP in cyclophotocoagulation and concluded, from a histological examination of three eyes with mid-term failure of IOP control following diode laser, that mechanisms other than ciliary epithelial regeneration, such as a reversal of increased uvoscleral outflow following laser treatment, may be significant in mid-term failure of IOP control following 'cycloablation'.
Adrian Farinelli reviewed phacoemulsification with trabeculectomy and IOL with either 5-FU or mitomycin and reported that mitomycin appeared to be more effective at reducing IOP, at least in the short-term with no additional complications.
In the section of psychophysical and detection of glaucoma, Richard Cooper described a new flashing red light emitting diode (LED) incorporated in a standard pen for confrontation visual field screening. This was easily taught to naive subjects both from Central Africa and Australia. Clinically significant field loss was accurately detected by this device.
Stuart Graham presented a paper on objective perimetry in glaucoma using the multi-channel multi-focal pattern VEP (visual evoked potentials). He concluded that this technique demonstrated better correspondence with this topography of the visual field than single channel recording, particularly due to improved detection along the horizontal - an important factor for its application to glaucoma. This represented a significant step towards the development of objective perimetry.
John Grigg also spoke on the multifocal VEP and the detection of early glaucomatous defects. He also reported work with the nerve fiber analyzer, suggesting that both tests are capable of detecting glaucomatous change at an earlier stage.
Vaegan compared psychophysical and electrophysiological measures of magnocellular specific deficits to the same stimulus, and concluded that electrophysiology is a better clinical index of magnocellular function than psychophysics. Psychophysics seemed to be foveally dominated, while electrophysiology reflected a wider area.
James Stewart reported preliminary results with the frequency doubling technology (PDT) perimetry as a community screening device for glaucoma, and concluded that it was well suited to this purpose.
Julian Rait compared Fastpac visual field testing and the frequency doubled illusion for glaucoma screening in the general population, as part of the Melbourne Visual Impairment Project.
In the session on medical therapy, Paul Chew reported the results on of a randomized double-masked study comparing latanoprost with timolot in patients with chronic angle-closure glaucoma (CACG). It demonstrated that latanoprost 0.005% once daily was significantly more effective than timolol in reducing IOP in patients with CACG. Latanoprost was well tolerated with few adverse effects and is the therapeutic choice as for the medical treatment of primary chronic angle-closure glaucoma.
Anne Brooks reported on clinical experience with Xalatan and confirmed its potent ocular hypotensive effect both on monotherapy and as 'add-on medication'. Reactions or side-effects to its use were encountered, but relatively infrequently.
Ivan Goldberg reported on brimonidine 0.2% versus betaxolol 0.25%, as measured by the clinical success rate and quality of life effects in patients with glaucoma. Brimomidine 0.2% bd achieved a higher overall clinical success rate than did betaxolol suspension 0.25% as a first-line therapy in patients with glaucoma or ocular hypertension.
Julian Rait spoke on strategies for neuroprotection in primary open-angle glaucoma. Neurones die through a process of apoptosis. Initial injury in glaucoma can lead to continuing loss of retinal ganglion cells and progressive visual field loss, despite conventional therapy. Strategies for neuroprotection have been proposed to protect retinal ganglion cells that escaped initial injury. The potential application of agents including betaxolol, brimonidine, memantine and segiline, for the therapy of glaucomatous optic neuropathy were discussed.
Jamie Craig gave a paper entitled "Glaucoma pedigrees with the GLC1A Gln368STOP mutation from the glaucoma inheritance in Tasmania (GIST)". He concluded that this mutation is associated with primary open-angle glaucoma of variable age of onset in the population studied. Other factors, as yet uncharacterized, may be involved in the expression of the POAG phenotype in GLLn368STOP pedigrees.
Paul Mitchell reported on the incidence of family history on the prevalence of glaucoma and ocular hypertension in the Blue Mountains eye study. He concluded that taking a positive family history of glaucoma remains useful, but will almost certainly underestimate genetic influence and is confounded by many biases.
Paul Mitchell also reported on the relationship between vascular hypertension, other cardiovascular diseases and glaucoma in the Blue Mountains eye study. He concluded that hypertension appeared to be a risk factor for glaucoma, with a high population attributable risk (22.6%), due to its relatively high prevalence.
In the miscellaneous glaucoma session, David Mackey presented a paper on vigabatrin (Sabril, an anti-epileptic medication, a selective inhibitor of GABA transaminase) associated visual field less resembling low-tension glaucoma. The field loss seemed to be related to current drug usage and arrested once weaned from vigabatrin.
Alan Kosmin reported on human retinal development. He concluded that the final developmental ganglion cell number is largely reached by the normal delivery date.
Representatives of the pharmaceutical companies made scientific presentations in their field of interest.
There were panel sessions on the management of challenging cases and of difficult cases, with lively discussion.
