R. Ritch

Intraocular Pressure Reduction in Normal-tension Glaucoma Patients

BACKGROUND In a collaborative study, patients with untreated normal-tension glaucoma were randomly assigned to a marked intraocular pressure reduction group or to a no therapy group. It was anticipated that medical therapy and laser trabeculoplasty would generally not achieve adequate pressure lowering and that fistulizing surgery would be required. This hypothesis was examined using current observations in the study. METHODS Patients randomized to the therapy group had a pressure reduction of at least 30% from their last prerandomization level. This was achieved within 6 months by means of fistulizing surgery or with pilocarpine and/or laser trabeculoplasty. Beta-blockers and adrenergic agonists were excluded from both eyes. RESULTS Of 30 patients with documented stable 30% pressure reduction, 17 (57%) achieved this with topical medication and/or laser trabeculoplasty: 8 with pilocarpine alone, 2 with laser trabeculoplasty alone, and 7 with laser trabeculoplasty after initial topical medication. The remaining 13 (43%) patients required a single fistulizing procedure. There was no statistically significant difference between the mean follow-up time for the nonfistulized group (533.8 +/- 437.6 days) and for the fistulized group (502.7 +/- 344.7 days). Both treatment groups had similar baseline profiles. CONCLUSION Marked pressure reduction can be achieved and maintained on a long-term basis by means other than fistulizing surgery in a large proportion of patients with untreated normal-tension glaucoma.

Factors affecting image acquisition during scanning laser polarimetry.

BACKGROUND AND OBJECTIVE To illustrate artifacts that may be encountered during measurement of the peripapillary retinal nerve fiber layer (RNFL) using scanning laser polarimetry (SLP). PATIENTS AND METHODS A total of 426 patients with a variety of ocular diagnoses underwent RNFL measurements using SLP from June 1996 to April 1997. Scanning was performed by two operators whose reproducibility of measurements had been previously validated. Images were selected to illustrate clinical features that adversely affected measurement of the thickness of the RNFL. RESULTS Image acquisition was difficult in eyes with corneal grafts or edema, keratic precipitates, anterior uveitis, posterior subcapsular cataract, vitreous opacity, peripapillary atrophy, posterior staphyloma, and high axial myopia. These scans resulted in poor clinical correlation with visual field tests and optic nerve examination, poor reproducibility of images, and unreadable images. CONCLUSION Anterior and posterior segment pathologies, particularly those localized to the cornea and lens, may produce spurious RNFL measurements and should be carefully considered prior to clinical decision making.

Effect of a tight necktie on intraocular pressure

Aim: To evaluate the effect of a tight necktie on intraocular pressure (IOP) measurement using Goldmann applanation tonometry. Methods: 40 eyes of 20 normal subjects and 20 open angle glaucoma patients (all male) were enrolled. IOP was measured with an open shirt collar, 3 minutes after placing a tight necktie, and 3 minutes after loosening it. All measurements were made by the same examiner. Results: Mean IOP in normal subjects increased by 2.6 (SD 3.9) mm Hg (p=0.008, paired t test; range −3 to +14 mm Hg) and in glaucoma patients by 1.0 (1.8) mm Hg (p=0.02, paired t test; range −2 to +4.5 mm Hg). In normal subjects, IOP in 12 eyes was increased by ⩾2 mm Hg and in seven eyes by ⩾4 mm Hg. In glaucoma patients, IOP in six eyes was increased by ⩾2 mm Hg and in two eyes by ⩾4 mm Hg. Conclusion: A tight necktie increases IOP in both normal subjects and glaucoma patients and could affect the diagnosis and management of glaucoma.

Detection of glaucoma using operator-dependent versus operator-independent classification in the Heidelberg retinal tomograph-III

Objective: To compare the abilities of a new Glaucoma Probability Scoring (GPS) system and Moorfields regression analysis (MRA) to differentiate between glaucomatous and normal eyes using Heidelberg retinal tomograph (HRT)-III software and race-specific databases. Methods: In this prospective study, one eye (refractive error ⩽5 D) each of consecutive normal patients and those with glaucoma was enrolled. All patients underwent a full eye examination, standard achromatic perimetry (Swedish Interactive Threshold Algorithm-standard automated perimetry (SITA-SAP), program 24-2) and confocal scanning laser ophthalmoscopy (HRT-II) within 1 month. Normal patients had two normal visual fields in both eyes (pattern standard deviation (PSD) >5% and Glaucoma Hemifield Test within 97% normal limits) and a normal clinical examination. Glaucoma was defined on the basis of SITA-SAP visual field loss (PSD<5% or Glaucoma Hemifield Test outside normal limits) on two consecutive visual fields. HRT-II examinations were exported to the HRT-III software (V.3.0), which uses an enlarged race-specific database, consisting of 733 eyes of white people and 215 eyes of black people. Race-adjusted MRA for the most abnormal sector (operator-dependent contour line placement) was compared with the global race-adjusted GPS (operator independent). MRA sectors outside the 99.9% confidence interval limits (outside normal limits) and GPS ⩾0.64 were considered abnormal. Results: 136 normal patients (72 black and 64 white patients) and 84 patients with glaucoma (52 black and 32 white patients) were enrolled (mean age 50.4 (SD 14.4) years). The average visual field mean deviation was −0.4 (SD 1.1) db for the normal group and −7.3 (SD 6.7) db for the glaucoma group (p<0.001). Mean GPS values were 0.21 (SD 0.23) and 0.73 (SD 0.27) for normal and glaucomatous eyes, respectively (p<0.001). Sensitivity and specificity values were 77.1% and 90.3% for GPS, and 71.4% and 91.9% for MRA, respectively. Conclusions: In this cohort, GPS software sensitivity and specificity values are similar to those of MRA, which requires placement of an operator-dependent contour line. The development of software to detect glaucoma without a contour line is critical to improving the potential use of HRT as a tool for glaucoma detection and screening.

A comparison between microperimetry and standard achromatic perimetry of the central visual field in eyes with glaucomatous paracentral visual-field defects

Background and aims: The aim was to correlate retinal sensitivity as determined by scanning laser ophthalmoscope microperimetry (SLO-MP) in glaucomatous eyes with paracentral visual field (VF) defects detected by standard automated perimetry (SAP). Methods: Twenty eyes with glaucomatous optic neuropathy and an SAP VF defect involving the central 16 test points (at least one point with p<1% in the 24–2 VF) were enrolled. Eyes with diseases other than glaucoma were excluded. All patients underwent SLO-MP and SAP of the central 10°. Results from each eye were divided into four quadrants for analysis. Normal and abnormal quadrants by SAP were compared with the corresponding normal and abnormal quadrants by SLO-MP. Regression analysis was used to correlate the mean threshold values (dB) of SLO-MP and SAP in each quadrant. Macular optical coherence tomography (OCT) was performed when there was a disagreement between functional tests. Results: The mean age and VF mean deviation were 60.8 (13.4) years and −7.3 (6.1) dB, respectively. There was a significant correlation between SLO-MP and SAP results in all quadrants (r2⩾0.68, p<0.001). All abnormal SAP quadrants had a corresponding abnormal SLO-MP quadrant. However, 21% of the normal SAP quadrants had an abnormal corresponding microperimetry result; a corresponding significant reduction in total macular thickness measured by OCT was present in 75% of these quadrants. Conclusions: Macular sensitivity evaluated by SLO-MP correlates significantly with SAP paracentral VF defects. SLO-MP detected retinal sensitivity reduction in areas of OCT structural damage with normal SAP and suggests that subtle paracentral functional deficits may be present in many more eyes with established glaucoma than generally assumed.

Diagnosis of traumatic cyclodialysis by ultrasound biomicroscopy.

BACKGROUND AND OBJECTIVE To evaluate the ability of high-frequency ultrasound biomicroscopy to diagnose traumatic cyclodialyses not evident on clinical examination. PATIENTS AND METHODS Six eyes to six patients with posttraumatic hypotony and/or shallow anterior chamber and suspected cyclodialysis clefts were examined with slit-lamp biomicroscopy, gonioscopy, B-scan ultrasonography, and ultrasound biomicroscopy. Ultrasound biomicroscopy provided high resolution of cross-sectional images of the anterior chamber angle, posterior chamber, and anterior uveal tissue. RESULTS Ultrasound biomicroscopy confirmed the disinsertion of the ciliary body from the scleral spur and associated ciliary body detachment in all eyes. Gonioscopy failed to demonstrate a cyclodialysis cleft in five eyes because of hyphema (two eyes) and abnormal iris architecture (related to trauma) precluding visualization of the angle recess (three eyes). Using information from ultrasound biomicroscopy imagining, one patient underwent a ciliary body reattachment procedure and repair of the cyclodialysis cleft. CONCLUSION Ultrasound biomicroscopy is a noninvasive method that can accurately diagnose the presence of traumatic cyclodialyses and can aid in surgical management. It is particularly useful in the presence of hazy media, hypotony, and/or abnormal anterior segment anatomy.

Ciliary body enlargement and cyst formation in uveitis.

BACKGROUND: Acute anterior uveitis has diverse causes and systemic associations. Inflammation is predominantly localised to the iris and pars plicata. Little is known about the in vivo effects of uveitis on ciliary body anatomy. METHODS: Bilateral, high frequency, high resolution, ultrasound biomicroscopy was performed on consecutive patients with unilateral anterior uveitis to evaluate ciliary body anatomy. Imaging was repeated when possible during the clinical course. The cross sectional area of the anterior ciliary body was measured using image processing and analysis software. Measurements from the uveitic eyes were compared with the fellow eyes and the effect of treatment was evaluated. RESULTS: Fourteen patients were enrolled. Ultrasound biomicroscopy demonstrated a larger ciliary body cross sectional area in the uveitic eyes compared with the fellow, clinically uninvolved eyes (2.45 (SD 0.48) mm2 versus 1.55 (SD 0.15) mm2, (p = 0.0000; paired t test)). A ciliochoroidal effusion was present in one uveitic eye. Epithelial cysts were imaged bilaterally in four uveitic patients (29%) and unilaterally in unaffected eyes of two uveitic patients. Ciliary body cross sectional area decreased following steroid therapy (p = 0.0001; paired t test). New cysts were noted in three uveitic eyes during the follow up period and in none of the fellow, unaffected eyes. CONCLUSION: Ultrasound biomicroscopy offers a new approach to the evaluation of anterior uveitis. The response to treatment can be evaluated objectively and therapeutic efficacy can be more easily assessed. It has the potential to help elucidate the pathophysiology and anatomical changes of this heterogeneous group of disorders.

Grayscale and Proportion-Corrected Optical Coherence Tomography Images

BACKGROUND AND OBJECTIVE The commercially available optical coherence tomography (OCT) scanner displays images in a pre-set window regardless of the projected scan length on the retinal surface. The aim of this study was to demonstrate the true dimensions of proportion-corrected OCT images and the additional information present in grayscale images. MATERIALS AND METHODS OCT raw data were exported to an IBM-compatible PC and processed to show grayscale and proportion-corrected images using an automated software of our own design. RESULTS Eyes with cystoid macular edema and retinal pigment detachment were analyzed. Grayscale images showed a finer gradation of signal reflectance. Scan lengths of 2, 4, 6, and 8 mm on the retinal surface showed different qualitative appearances using proportion-corrected software from the printed or on-screen images. CONCLUSIONS Grayscale OCT images can be used to demonstrate additional information not present in false-color images. The disparity between the standard OCT image format and proportion-corrected images emphasizes the need for quantitative rather than qualitative evaluation of retinal dimensions and internal reflectance.

The effects of glaucoma on the latency of the multifocal visual evoked potential

Aims: To determine the effect of glaucomatous damage on the latency of the multifocal visual evoked potential (mfVEP). Methods: Monocular mfVEPs were recorded from a glaucoma group (n = 50) defined by a glaucomatous disc and an abnormal visual field and a control group (n = 47). 25 patients were characterised as normal tension glaucoma (NTG) and 25 as high tension glaucoma (HTG). Monocular and interocular latency analyses of the more affected eye were obtained using custom software. Results: On interocular analysis, both the HTG and NTG groups showed a statistically significant increase in mean mfVEP latency with average relative latencies and percentage of points with significant delays of 1.7 ms and 10.3% (HTG) and 1.3 ms and 8.2% (NTG) compared to −0.3 ms and 2.7% (controls). On monocular analysis, only the HTG group showed a significant increase in latency with measures of 5.7 ms and 14.6% (HTG) compared to 3.2 ms and 10.6% (NTG) and 2.1 ms and 9.6% (controls). Using the 95th percentile of a normative group as the cut off, the sensitivity ranged from 20% to 38% and the specificity from 87% to 100% with the interocular analysis providing the best discrimination, Conclusion: Although up to 40% of patients showed delays in the mfVEP latency, these delays were modest, on average a few milliseconds. These results differ markedly from those of a recent conventional VEP study, which reported 100% sensitivity, 100% specificity, and an average delay that exceeded 25 ms.

Factors associated with topographic changes of the optic nerve head induced by acute intraocular pressure reduction in glaucoma patients.

PurposeTo investigate factors associated with changes in optic nerve head (ONH) topography after acute intraocular pressure (IOP) reduction in patients with primary open-angle glaucoma (POAG).MethodsUntreated POAG patients (IOP >21 mm Hg) were prospectively enrolled. Systemic and ocular information were collected, including central corneal thickness (CCT) and corneal hysteresis (CH). All patients underwent confocal scanning laser ophthalmoscopy and tonometry (Goldmann) before and 1 h after pharmacological IOP reduction. The mean of three measurements was considered for analysis. Changes in each ONH topographic parameter were assessed (one eye was randomly selected), and those that changed significantly were correlated with patients systemic and ocular characteristics.ResultsA total of 42 patients were included (mean age, 66.7±11.8 years). After a mean IOP reduction of 47.3±11.9%, significant changes were observed in cup area and volume, and in rim area and volume (P<0.01), but not in mean cup depth (P=0.80). Multiple regression analysis (controlling for baseline IOP and magnitude of IOP reduction) showed that CH (r2=0.17, P<0.01) and diabetes diagnosis (r2⩾0.21, P<0.01) were negatively correlated with the magnitude of changes in ONH parameters, whereas the cup-to-disc ratio was positively correlated (r2=0.30, P<0.01). Age, race, disc area, and CCT were not significant (P⩾0.12). Including all significant factors in a multivariable model, only the presence of diabetes remained significantly associated with all ONH parameters evaluated (P<0.01).ConclusionsDifferent systemic and ocular factors, such as diabetes, CH, and the relative size of the cup, seem to be associated with the magnitude of changes in ONH topography after acute IOP reduction in POAG patients. These associations partially explain the ONH changes observed in these patients and suggest that other factors are possibly implicated in an individual susceptibility to IOP.