The sensitivity and specificity of scanning laser polarimetry in the detection of glaucoma in a clinical setting.

OBJECTIVE: A study was conducted to determine the sensitivity and specificity of masked experts in classifying results obtained from normal eyes, glaucomatous eyes, and eyes suspicious for glaucoma using the Nerve Fiber Analyzer GDx (Laser Diagnostic Technologies, San Diego, CA), a scanning polarimeter. DESIGN: Retrospective consecutive case series. METHODS: Consecutive subjects seen in a glaucoma clinic were imaged with the GDX: The masked printouts were distributed to nine experienced users of the machine, who were asked to classify the scan from each eye as normal, suspicious for glaucoma, or consistent with glaucoma. No specific guidelines for interpretation were used. The interpretations were compared with the known diagnoses obtained from review of the subjects' medical records. The number of correct diagnoses, false-positive answers (specificity), and false-negative answers (sensitivity) were noted for each observer and averaged for all nine. Interobserver agreement was calculated by use of the kappa statistic. MAIN OUTCOME MEASURES: False-positive and false-negative responses from reviewers' assessments compared with known diagnoses from chart review. RESULTS: A total of 104 eyes was included: 29 normal eyes, 33 eyes from glaucoma suspects, and 42 eyes with glaucoma. Interobserver agreement was moderate for normals (kappa = 0.42, P = 0.00) and glaucoma (kappa = 0.48, P = 0.00), but slight for glaucoma suspects (kappa = 0.09, P = 0.00). Overall, the average sensitivity was 74% and the specificity was 74%. If only considering whether or not the scan represented glaucoma (i.e., reviewer assessment of "suspect" meant "not glaucoma"), the average sensitivity was 86% and the specificity 83%. If only considering whether a scan was normal or not (i.e., reviewer assessment of "suspect" meant "abnormal"), the sensitivity was 83% and the specificity 86%. Eliminating glaucoma suspects (but allowing the assessment of "suspect") increased overall sensitivity to 80% and specificity to 79%. With suspects eliminated, sensitivity was 80% and specificity 91% for determination of glaucoma, and sensitivity was 93% and specificity 79% for determination of abnormality. CONCLUSIONS: Scanning laser polarimetry may have good sensitivity and specificity for separating normal from abnormal eyes, but it is not as good for classifying unknown subjects when glaucoma suspects are included. Evaluation of new parameters and continued clinical experience may help develop guidelines for interpretation and/or specific indicators for glaucomatous damage to increase the sensitivity and specificity.

Differentiating patients with glaucoma from glaucoma suspects and normal subjects by nerve fiber layer assessment with scanning laser polarimetry.

PURPOSE: A study was conducted to determine normative data for nerve fiber layer measurements as obtained by scanning laser polarimetry with the Laser Diagnostic Technologies Nerve Fiber Analyzer II, identify factors affecting the measurements, and identify parameters capable of differentiating normal subjects from patients with glaucoma and patients suspected of having glaucoma because of ocular hypertension or because of a large cup-to-disc ratio (GS-disc). DESIGN: A case series. PARTICIPANTS: Four hundred normal subjects, 35 patients with ocular hypertension, 42 patients with glaucoma, and 17 glaucoma suspects based on optic disc appearance participated. METHODS: Nerve fiber layer thickness assessments were determined in normal subjects (with normal-appearing optic nerves and normal visual fields). The results were compared to measurements from samples of age-matched patients with ocular hypertension (with normal visual fields), patients suspected of having glaucoma based on enlarged cup-to-disc ratios, and patients with open-angle glaucoma who had visual field loss. RESULTS: The majority of the parameters derived from the measurements showed no significant relationship to age, although some parameters tended to decrease with increasing age. Multiple parameters showed statistically significant differences between normal subjects and patients with glaucoma. In particular, the intraellipse sector variability, an indirect measure of the shape of the nerve fiber layer in an ellipse surrounding the nerve head, showed statistically significant differences between normal subjects and patients with glaucoma as well as between glaucoma suspects and normal subjects. Similar results were seen with the superior maxima, the average thickness assessment value of the 1500 thickest points in the superior bundle. CONCLUSIONS: Assessments of nerve fiber layer thickness as determined by scanning laser polarimetry can differentiate patients with glaucoma from normal subjects and may identify otherwise undetected damage in glaucoma suspects.

Fascia lata patch graft in glaucoma tube surgery.

PURPOSE: To determine if using human cadaveric fascia lata grafts to cover glaucoma implant tubes is safe and effective. METHODS: All patients who underwent glaucoma implant surgery at the Doheny Eye Institute between July 1993 and September 1993 received a fascia lata patch graft to cover the subconjunctival portion of the tube. These patients were followed prospectively for clinical signs of conjunctival breakdown, graft melt, tube erosion, graft-related inflammation, infection, and graft-related complications. RESULTS: Twenty-two eyes of 21 patients were followed for a mean of 19 months. All eyes tolerated the fascia lata grafts well without clinical evidence of graft-related conjunctival, scleral, or intraocular inflammation. No tube erosion or melting of the graft was observed in the study group. CONCLUSION: Preserved donor fascia lata was well tolerated as a grafting material in glaucoma implant surgery. No clinical signs of graft rejection, foreign body reaction, tube erosion, or graft melt were observed in the study group during the follow-up period.

Intracameral tissue plasminogen activator after glaucoma surgery. Indications, effectiveness, and complications.

PURPOSE: To describe the authors' clinical experience with intracameral tissue plasminogen activator (tPA) after glaucoma surgery. METHODS: Retrospective review of medical records of all patients who received intracameral tPA after glaucoma surgery at the Doheny Eye Institute from November 4, 1992, to June 14, 1994. There were 20 tPA administrations (18 eyes of 17 patients) in doses ranging from 6 to 25 microgram. Indication for tPA administration was decreased bleb function secondary to blood/fibrin clot in aqueous outflow pathway. RESULTS: Tissue plasminogen activator was given after trabeculectomy (5 drug administrations) and combined cataract extraction/trabeculectomy procedures (9 drug administrations), with increased filtration in 12 (86%). There were five (36%) instances of hyphema and three (21%) of hypotony. All hyphemas occurred after doses of 25 microgram. Final IOP of 18 mmHg or lower and 6 mmHg or higher was achieved in 11 (92%) of 12 patients after a mean follow-up interval of 4.2+/-4.7 months. The six remaining tPA irrigations were done in five patients after glaucoma drainage implant surgery (n=4) or surgical/needle revision of a filtering bleb (n=2). CONCLUSIONS: Aqueous outflow obstruction from blood/fibrin clot after glaucoma surgery may be treated effectively with intracameral tPA in doses of 6 to 25 microgram. The authors recommend using a dose of less than or equal to 6 to 12.5 microgram to minimize risk of hyphema.

Discourse comprehension of synthetic speech across three augmentative and alternative communication (AAC) output methods.

The purpose of this investigation was to determine the relative effects of three different Augmentative and Alternative Communication (AAC) speech output methods (word, sentence, mixed words and letters) on a listener's ability to summarize paragraph-length texts. Based on previous work on the discourse processing of synthetic speech, a monotonic trend in a listener's ability to accurately summarize texts produced by different output methods was hypothesized (word > sentence > mixed). Thirty able-bodied adults were individually tested over a 2-day period, listening to four texts produced by a DECtalk speech synthesizer at a speech presentation rate of 7.5 wpm. Using a discourse summarization taxonomy developed by Higginbotham, Lundy, and Scally (1993), the experimental hypothesis was confirmed. Word-method listeners produced significantly more accurate renditions of the original texts than sentence-method listeners, who, in turn, did better than mixed-method listeners. Statistically significant differences also were found for the topic familiarity of the texts. The role of the above variables on AAC device comprehension and technology design is discussed.

Pars plana Baerveldt tube insertion with vitrectomy in glaucomas associated with pseudophakia and aphakia.

PURPOSE: We reviewed the course of intraocular pressure, visual acuity, and complications in patients with shallow anterior chambers or vitreous prolapse who underwent insertion of glaucoma drainage tubes through the pars plana (after a complete posterior vitrectomy). METHODS: Thirteen patients (13 eyes) with uncontrolled glaucoma associated with shallow anterior chamber or vitreous prolapse and aphakia or pseudophakia underwent pars plana Baerveldt tube insertion after vitrectomy. RESULTS: In 11 eyes the intraocular pressure was less than or equal to 15 mm Hg at a minimum follow-up of one year; the other two eyes underwent additional glaucoma surgery. Two of the 11 eyes with controlled intraocular pressure had limitation of ocular motility postoperatively. No retinal complications had occurred in any of the 13 eyes. CONCLUSION: This technique of combined pars plana vitrectomy and pars plana insertion of a Baerveldt tube provides intraocular pressure control in eyes with shallow anterior chamber or vitreous prolapse and glaucoma associated with pseudophakia or aphakia.

Tissue plasminogen activator and glaucoma drainage implants.

PURPOSE: The tube lumen of a glaucoma drainage implant is prone to occlusion by a blood or fibrin clot due to its small caliber, relatively low flow rate, and the plasmoid nature of the aqueous humor passing through it in the early postoperative period. The use of tissue plasminogen activator in the management of drainage tube obstruction is described herein. METHODS: Two cases of drainage tube obstruction in patients with neovascular glaucoma treated with an intracameral injection of tissue plasminogen activator are reported. RESULTS: Resolution of tube obstruction following tissue plasminogen activator administration with spontaneous lowering of the intraocular pressure and bleb formation was achieved in both cases. Differentiation of tube obstruction from other causes of elevated intraocular pressure following installation of glaucoma drainage devices is discussed. CONCLUSION: The intracameral injection of tissue plasminogen activator may relieve drainage tube obstruction secondary to a blood or fibrin clot, even in the absence of any visible clot covering the proximal tube ostium or within the anterior chamber portion of the tube. This approach should be considered, in selected cases, prior to more invasive surgical revision.