Understanding structure and function in glaucoma

OBJECTIVE: Glaucomatous optic neuropathy (GON), defined as definitive damage to the optic-nerve head (ONH) and retinal-nerve-fiber layer (RNFL), involves structural changes in the ONH and RNFL and functional losses in the central visual field. Due to the unique anatomic distribution of the nerve fibers as they enter the ONH, there are specific changes in the ONH correlated with specific findings in the visual-field characteristic of GON. The evaluation of these changes is discussed. METHODS: There are qualitative and quantitative methods in the structural examination of the ONH and RNFL, and quantitative techniques in the functional assessment of the central visual field. They are correlated to one another their strengths and limitations are discussed. RESULTS: Clinical evaluation of the ONH and RNFL consists of five basic rules: (1) identify the limits of the optic disc and determine its size, (2) identify the s of the neuroretinal rim, (3) examine the RNFL, (4) examine the region for parapapillary atrophy, and (5) look for retinal and optic-disc hemorrhages. These steps are simple to use and comprise a portion of the comprehensive eye evaluation. Without proper documentation of the changes in glaucoma progression may be missed. Computer-based digital-imaging technology exemplified by the HRT II, GDx, OCT, provides fast, reproducible, objective measurements of the ONH and RNFL, allowing for more precise diagnosis and monitoring of glaucoma. These changes have good correlation to functional assessments exemplified by the standard automated perimetry (SAP) and the selective perimetry (FDT, SWAP). Typical glaucomatous visu field defects include nasal step, paracentral scotoma, and arcuate defects which follow the RNFL pattern. Progression of these defects is monitored over time and needs to be differentiated from long-term fluctuation. CONCLUSION: The clinician should perform both structural and functional assessments to diagnose and monitor glaucoma. Both examinations provide complimentary information and each has its own place in the clinical care of glaucoma patients. The newer imaging devices and selective perimetry augment the diagnostic armamentarium of the clinician and should, therefore, be used appropriately.

What is the optimal surgical management?

OBJECTIVE: Since cataract and glaucoma often coexist, and there is no agreement as to their optimal management, a review of the surgical strategies for coexisting I cataract and glaucoma is necessary. The latest evidence-based findings from various studies are presented. METHODS: A literature search of the latest full articles (up to September 2006) was conducted on the surgical management of coexisting cataract and glaucoma. The results of the 2001 Johns Hopkins milestone study were also included for analysis and comparison. RESULTS: Evidence is strong that trabeculectomy is associated with increased risk of postoperative cataract. Though cataract surgery alone may be appropriate for some glaucoma patients, combined cataract and glaucoma surgery lower long-term intraocular pressure (IOP) more than cataract extraction alone. Use of intraoperative mitomycin-C is beneficial in combined surgery. Limbu and fornix-based conjunctival flaps are equally effective for lowering IOP combined surgery. Trabeculectomy alone lowers long-term IOP more tha combined extracapsular cataract extraction (ECCE) and trabeculectomy. Evidence is weak that combined surgery with phacoemulsification rather than ECCE results in lower long-term IOP, as does two-site compared to single-site combined surgery. CONCLUSION: The literature does not point to an optimal strategy for controlling in patients with coexisting cataract and glaucoma needing surgery. There is a continued need for high-quality studies of longer duration and more information on the optic nerve and visual field.

YAG laser rate for posterior capsular opacification (PCO) using varied IOL materials

This study aims to determine the average span of time for Nd:YAG Capsulotomy for posterior capsular opacification after phacoemulsification using four (4) different posterior chamber intraocular lens (IOL) materials (acrylic, polymethylmethacrylate, silicone and hydrogel). This is a retrospective, cohort study wherein data from the charts of 46 patients of a single surgeon were tabulated. All the patients underwent a standardized and an uncomplicated phacoemulsification for senile cataracts with posterior chamber IOL insertion. There were a total of 50 IOLs in this study, 8 acrylic, 16 polymethylmethacrylate (PMMA), 24 silicone and 2 hydrogel. The average duration before Nd: YAG capsulotomy was necessary for each IOL material were: acrylic 11.91 months, PMMA 14.50 months, silicone 18.25 months and hydrogel 8.125 months. This study revealed that each of the four (4) different IOL materials had no influence on the span of time before the necessity for Nd: YAG capsulotomy. (Author)

Cup to disc ratio and optic disc size in screening for glaucoma

PURPOSE:To determine the cup and disc areas using computer-aided imaging. METHODOLOGY:Case-control study using the computer-aided imaging as a screening test in a given population. RESULTS:There is a wide variability in cup and disc areas among glaucoma suspects and normal. CONCLUSION:C:D alone has a poor predictive value for diagnosing glaucoma.Optic disc size with C:D is just as sensitive and specific in screening for glaucoma.Cup and disc areas are positively correlated for normal and glaucoma suspects.