Alberto Colotto

PATTERN ELECTRORETINOGRAM IN TREATED OCULAR HYPERTENSION: A CROSS-SECTIONAL STUDY AFTER TIMOLOL MALEATE THERAPY

To investigate pattern electroretinogram changes in treated ocular hypertension, we evaluated pattern electroretinogram recordings of 48 hypertensive eyes following an 8-month timolol maleate therapy. During treatment, 27 of 48 eyes had normalized intraocular pressures (15-18 mm Hg), while 21 retained elevated values (21-25 mm Hg). Twenty-eight eyes with untreated hypertension (22-25 mm Hg) lasting at least 8 months, as well as 32 untreated, normotensive eyes served as controls. When compared to untreated normotensive controls, timolol-treated eyes with either elevated or normalized intraocular pressures showed reductions in the mean electroretinographic amplitudes. However, these amplitude reductions were substantially greater in treated eyes with elevated pressures as compared to those with normalized ones. Untreated hypertensive controls showed pattern electroretinogram reductions, with respect to normal values, that were comparable to those of treated hypertensive eyes, but larger than those of treated normotensive ones. These results indicate that, in treated ocular hypertension, pattern electroretinogram losses tend to be associated with moderately increased intraocular pressures in the range of 21-25 mm Hg. Electroretinographic abnormalities may be, at least in part, prevented only by lowering intraocular pressure into a normal range.

Optic nerve diameters and perimetric thresholds in idiopathic intracranial hypertension.

AIMS/BACKGROUND--Idiopathic intracranial hypertension (IIH) is a central nervous disorder characterised by abnormally increased cerebrospinal fluid (CSF) pressure leading to optic nerve compression. An indirect estimate of increased CSF pressure can be obtained by the ultrasonographic determination of optic nerve sheaths diameters. Computerised static perimetry is regarded as the method of choice for monitoring the course of the optic neuropathy in IIH. The aims were to compare the echographic optic nerve diameters (ONDs) and the perimetric thresholds of patients with IIH with those of age-matched controls, and to examine the correlation between these two variables in individual patients with papilloedema. METHODS--Standardised A-scan echography of the mid orbital optic nerve transverse diameters and automated threshold perimetry (Humphrey 30-2) were performed in 20 patients with IIH with variable degree of papilloedema (according to the Frisén scheme) and no concomitant ocular diseases. Echographic and perimetric results were compared with those obtained from 20 age-matched controls. RESULTS--When compared with controls, patients with IIH showed a significant increase in mean ONDs and significantly reduced mean perimetric sensitivities. In individual patients with papilloedema, the transverse ONDs correlated negatively with Humphrey mean deviation values and positively with pattern standard deviation values. CONCLUSION--These results indicate that OND changes in IIH are associated with perimetric threshold losses, and suggest that IIH functional deficits may be related to the degree of distension of optic nerve sheaths as a result of an increased CSF pressure.

Subfoveal choroidal blood flow and central retinal function in early glaucoma

Purpose:  To assess subfoveal choroidal blood flow (ChBF) in patients with early manifest glaucoma (EMG) and to compare blood flow with functional measures of central retinal integrity, standard automated perimetry (SAP) and pattern electroretinogram (PERG).

Posterior pole retinal thickness in ocular hypertension and glaucoma: early changes detected by hemispheric asymmetries.

To evaluate retinal thickness at the posterior pole of the fundus in ocular hypertension (OHT) and open-angle glaucoma (OAG), and to correlate morphometric findings with visual sensitivity as determined by automated perimetry. Methods:One randomly selected eye from 41 patients with clinical diagnosis of OHT (n = 25) or early to moderate OAG (n = 16) and 16 age-matched normal controls was examined. Retinal thickness was measured by Retinal Thickness Analyzer (RTA), acquiring 5 pre-defined scans covering the central 20° of the fundus. RTA average thickness and thickness profile data, including hemispheric asymmetries calculated as relative (superior/inferior and nasal/temporal) or absolute (vertical and horizontal, ie, independent of which hemisphere was thinner) parameters, were calculated. For each eye, white-on-white Humphrey 30-2 visual field results were analyzed, in addition to standard global indices, by quantifying perimetric sensitivities for regions of the posterior pole corresponding to those sampled by the RTA. Results:On average, central retinal thickness was reduced (P < 0.05) in OAG compared with OHT or normal control eyes. Vertical hemispheric absolute thickness asymmetry was increased (P ≤ 0.01) in OAG eyes compared with the other groups. Horizontal hemispheric absolute thickness asymmetry was increased (P < 0.01) in both OHT and OAG eyes, compared with control eyes. At least one of the RTA parameters was altered in 13 of 25 OHT (52%) and 12 of 16 OAG eyes (75%), most frequently involving thickness asymmetries. In OAG, but not OHT eyes, superior/inferior asymmetry was positively (r = 0.69, P < 0.01) correlated with the corresponding asymmetry in perimetric sensitivity. Conclusions:The RTA can reveal increased hemispheric thickness asymmetries in both OHT and OAG eyes. In OAG eyes thickness asymmetries are associated with corresponding perimetric asymmetries. The findings in OHT eyes suggest that localized anatomic and functional damage to inner retina may not develop in parallel early in the disease process.

Morpho-functional follow-up of the optic nerve in treated ocular hypertension: disc morphometry and steady-state pattern electroretinogram.

Purpose: To examine longitudinally optic disc structure and inner retinal function in treated ocular hypertension (OHT). Materials and Methods: A morphometric (Heidelberg Retina Tomograph, HRT) and functional (steady-state pattern electroretinogram, PERG) evaluation of 27 OHT patients treated with topical beta-blockers and/or prostaglandin analogues and prospectively followed over a 24 ± 6 month period. Results: Compared with baseline, mean final PERG amplitude tended to increase (p < 0.01), while HRT was stable. Individual PERG amplitude increase was large (≥ 100%) in some patients (5/27), and unexplained by clinical parameters at baseline. Conclusions: In treated OHT, functional responses may improve while disc structure remains stable. The findings suggest that OHT-associated inner retinal dysfunction is at least in part reversible with therapeutic intraocular pressure control.

Hyperemic responses of the optic nerve head blood flow to chromatic equiluminant flicker are reduced by ocular hypertension and early glaucoma

Abstract. We evaluated in ocular hypertension (OHT) and early glaucoma (EOAG) patients the optic nerve head (ONH) blood flow response (RFonh) to chromatic equiluminant flicker. This stimulus generates neural activity dominated by the parvo-cellular system. Eleven EOAG, 20 OHT patients, and 8 age-matched control subjects were examined. The blood flow (Fonh) at the neuroretinal rim was continuously monitored by laser Doppler flowmetry before, during, and after a 60-s exposure to a 4 Hz, red-green equiluminant flicker stimulus (30 deg field). RFonh was expressed as percentage Fonh-change during the last 20 s of flicker relative to baseline Fonh. Responses were collected at a number of temporal sites. The highest RFonh value was used for subsequent analysis. As compared to controls, both OHT and EOAG patients showed a decrease (p<0.01) in mean RFonh. We conclude that RFonh elicited by chromatic equiluminant flicker is abnormally reduced in OHT and EOAG patients indicating an impairment of the parvo-cellular-mediated vasoactivity. This decrease of vascular response may occur independently of neural activity loss early in the disease process.

Pattern Electroretinogram Detects Localized Glaucoma Defects

Purpose We evaluated the clinical ability of pattern electroretinogram (PERG) to detect functional losses in the affected hemifield of open-angle glaucoma patients with localized perimetric defects. Methods Hemifield (horizontally-defined) steady-state PERGs (h-PERGs) were recorded in response to 1.7 c/deg alternating gratings from 32 eyes of 29 glaucomatous patients with a perimetric, focal one-hemifield defect, 10 eyes of 10 glaucomatous patients with a diffuse perimetric defect, and 18 eyes of 18 age-matched normal subjects. Standard automated perimetry (SAP) and spectral-domain optical coherence tomography (SD-OCT) for retinal nerve fiber layer (RNFL) thickness also were performed. h-PERG amplitudes and ratios, calculated corresponding hemifield perimetric deviations, as well as hemiretina RNFL thicknesses were analyzed. Results h-PERG amplitudes, perimetric deviations, and RNFL thicknesses showed losses (P < 0.001) when comparing affected with unaffected hemifields of localized glaucomatous eyes. No differences were found in h-PERG amplitudes between hemifields of normal or diffuse glaucomatous eyes. h-PERG amplitude ratios (affected/unaffected hemifield) in localized glaucoma were lower (P < 0.001) than the ratios from normal or diffuse glaucomatous eyes. The areas under the receiver operating characteristic curves for h-PERG amplitude ratios, comparing localized-defect glaucomatous eyes with normal or diffuse glaucomatous eyes, were 0.93 and 0.91, respectively. Conclusions h-PERG assessment showed good diagnostic accuracy to confirm localized glaucomatous defects detected perimetrically. This test may be particularly useful in cognitively impaired patients or young/nonverbal patients unable to provide reliable visual fields. Translational Relevance h-PERG provides a sensitive objective measure to confirm focal losses detected with SAP and/or RNFL thickness analysis.

Optic Nerve Diameters and Perimetric Thresholds in Idiopathic Intracranial Hypertension

AIMS/BACKGROUND Idiopathic intracranial hypertension (IIH) is a central nervous disorder characterised by abnormally increased cerebrospinal fluid (CSF) pressure leading to optic nerve compression. An indirect estimate of increased CSF pressure can be obtained by the ultrasonographic determination of optic nerve sheaths diameters. Computerised static perimetry is regarded as the method of choice for monitoring the course of the optic neuropathy in IIH. The aims were to compare the echographic optic nerve diameters (ONDs) and the perimetric thresholds of patients with IIH with those of age-matched controls, and to examine the correlation between these two variables in individual patients with papilloedema. METHODS Standardised A-scan echography of the mid orbital optic nerve transverse diameters and automated threshold perimetry (Humphrey 30-2) were performed in 20 patients with IIH with variable degree of papilloedema (according to the Frisén scheme) and no concomitant ocular diseases. Echographic and perimetric results were compared with those obtained from 20 age-matched controls. RESULTS When compared with controls, patients with IIH showed a significant increase in mean ONDs and significantly reduced mean perimetric sensitivities. In individual patients with papilloedema, the transverse ONDs correlated negatively with Humphrey mean deviation values and positively with pattern standard deviation values. CONCLUSION These results indicate that OND changes in IIH are associated with perimetric threshold losses, and suggest that IIH functional deficits may be related to the degree of distension of optic nerve sheaths as a result of an increased CSF pressure.

Pattern electroretinogram and chronic ocular hypertension

SummaryPattern-reversal electroretinograms to sinusoidal gratings of variable spatial frequency (0.6–4.8 cycles/degree) have been recorded in 28 normal subjects and 23 patients with ocular hypertension or early glaucoma who were previously treated with timolol maleate during a 12–24 months clinical follow-up. A multivariate analysis of variance showed that pattern electroetinogram amplitude was significantly reduced in patients as compared to control. This reduction was evident only in the low-medium spatial frequency range and was more marked (and progressive) in eyes with abnormal intraocular pressure (22–30 mmHg) as compared to eyes with normal intraocular pressure (14–21 mmHg) during the follow-up period. These results suggest that the pattern electroretinogram may detect the progression of neurosensory deficits associated with ocular hypertension in eyes with inadequate response to medical treatment.ZusammenfassungVon 28 Normalpersonen und 23 Patienten mit okulärer Hypertension oder Glaucoma chronicum simplex mit Timolol Maleat-Behandlung wurden Musterumkehr-Elektroretinogramme (sinusförmige Modulation, Raumfrequenzen zw. 0,6 – 4,8 Zyklen/Grad) nach einer 12- und 24monatigen klinischen Nachkontrollzeit abgeleitet. Die Ableitungen der Patienten zeigten gegenüber Normalpersonen in der Varianzanalyse eine signifikante Amplitudenreduktion für Muster mit niedrigen und mittleren Raumfrequenzen. Innerhalb der Patientengruppe war die Amplitudenverminderung bei Patienten mit erhöhtem Augeninnendruck (22 – 30 mmHg) im Gegensatz zu solchen mit normalem Augeninnendruck (14 – 21 mmHg) besonders ausgeprägt. Gemäß dieser Ergebnisse könnten zunehmende neurosensorische Ausfälle durch okuläre Hypertension und unzureichendem Ansprechen auf die Medikation mittels dem Muster-Elektroretinogramm aufgezeigt werden.