Long-term visual pathway alterations after elemental mercury poisoning: report of a series of 29 cases.

BACKGROUND: There are few clinical data on retinal involvement after acute exposure to high concentrations mercury and the available reports are based on a small number of patients suffering chronic exposure. The purpose of this paper is to report findings in workers acutely exposed to very high concentrations of mercury vapor with the aim of providing data on a possible direct retinal involvement. METHODS: Twenty-nine patients and 16 controls were evaluated in a comparative case series. Mercury levels in blood and urine samples, visual acuity (VA), contrast sensitivity (CS), visual field (VF), color discrimination and optical coherence tomography (OCT) were recorded. The pattern reversal visual-evoked potentials (PRVEP), full-field and multifocal electroretinography (ffERG/mfERG), pattern electroretinography (PERG), systemic symptoms, presence of erethism, and electromyography (EMG) were also gathered. A descriptive analysis was performed. The correlations between variables also were studied. In addition, electrophysiological data from those patients with deeper VF defects (group 1) were compared with a normal control group. RESULTS: Twenty-six workers exhibited symptoms of erethism. The EMG showed sensorimotor polyneuropathy and multiple mononeuropathy. The VA was slightly affected in 48.27% (n = 14) of subjects. Loss of CS in at least one of four spatial frequencies and color vision alterations occurred in 96.5% (n = 28) and 44.8% (n = 13), respectively. VF alterations were identified in 72.4% (n = 21) patients. No morphologic changes were seen in the OCT scans. Latencies over 100 milliseconds and reduced amplitudes of P100 were found in the PRVEP (p < 0.05). The reduced amplitude of the b wave at the ffERG, of the P50 at the PERG and of the P1 wave at the mfERG results (p < 0.05) suggested that the outer retina was involved. Significant negative correlations among blood mercury levels, VA, and ffERG were observed. CONCLUSIONS: In this case series, showed that acute exposure to mercury vapor had a hazardous effect on the visual system. Although neurologic and visual pathway involvement was clearly demonstrated, the differences found compared to control support the existence of a direct functional retinal damage and participation in impaired vision in mercury poisoning.

Development of a new algorithm based on FDT Matrix perimetry and SD-OCT to improve early glaucoma detection in primary care.

PURPOSE: The purpose of this study was to develop an objective algorithm to discriminate the earliest stages of glaucoma using frequency doubling technology (FDT) Matrix perimetry and spectral domain-optical coherence tomography (OCT) technology to improve primary care detection. MATERIALS AND METHODS: Three hundred six eyes (mean age 58.67±15.12) from 161 patients were included and classified in the following three groups: 101 nonglaucoma (GI-NG), 100 glaucoma suspect (GII-SG), and 105 open-angle glaucoma (GIII-OAG). All participants underwent a visual field exploration using the Humphrey Matrix visual field instrument and retinal nerve fiber layer evaluation using the Topcon 3D OCT-2000. Pattern deviation plot was divided into 19 areas and five aggrupation or quadrants and ranked with a value between 0 and 4 according to its likelihood of normality, and differences among three groups were analyzed. Principal component analysis (PCA) was also used to extract the most notable features of FDT and OCT, and a logistic regression analysis was applied to obtain the classification rules. RESULTS: Only area numbers 7 and 12 and the central zone of FDT Matrix showed statistical differences (P<0.05) between GI-NG and GII-SG. The classification rules were estimated by the four PCA obtained from FDT Matrix and 3D OCT-2000 in a separate and combined use. Area under the receiver operating characteristic curve was 78.88% with FDT-PCA, 82.09% with OCT-PCA, and 94.27% with combined use of FDT and OCT-PCA to discriminate GI-NG and GII-SG. CONCLUSION: The predictive rules based on FDT-PCA or OCT-PCA provide a high sensitivity and specificity to detect the earliest stages of glaucoma and even better in combined use. These predictive rules may help the future development of software for FDT Matrix perimetry and 3D OCT-2000, which will greatly improve their diagnostic ability, making them useful in daily practice in a primary care setting.

Refractive stabilization and corneal swelling after cataract surgery.

PURPOSE: To determine the earliest time after cataract surgery when corneal swelling and automated refraction are stabilized sufficiently to allow reliable refractive prescription. METHODS: This was a prospective, nonrandomized, case series study of 124 consecutive eyes undergoing uneventful cataract surgery. Automated refraction and central corneal thickness (CCT) measurements were made at baseline before cataract surgery and on follow-up visits 1 day and weekly for 4 weeks afterward. Corneal swelling was determined as the percentage change in CCT after surgery. To determine the validity of automated refraction, it was compared with subjective refraction at the final visit. RESULTS: Corneal swelling decreased between the first postsurgical day and the first week and again between postsurgical weeks 1 and 2 (p < 0.01 each). Although thinning continued through the fourth postsurgical week, the changes were not significant. Both spherical and cylindrical refraction were stable 1 week after surgery, with the greatest change between the first postsurgical day and 1 week (p < 0.01). In replicate measurements of automated spherical refraction taken on the last visit, the intraclass correlation coefficient was 0.93. For automated cylindrical refraction, it was 0.81. CONCLUSIONS: Automated refraction is highly repeatable and can be used to monitor postsurgical refractive changes. Whereas corneal swelling becomes stable 2 weeks after cataract surgery, automated refraction becomes stable after 1 week and can be used to accurately prescribe corrective lenses at that time.

Repeatability and agreement of ARK-30 autorefraction after cataract surgery.

BACKGROUND: To evaluate the intra-test variability of ARK-30 handheld autorefractor and the agreement with subjective refraction and retinoscopy after uneventful cataract surgery. DESIGN: Prospective and non-randomized study that included 6 visits by patients undergoing uneventful cataract surgery at IOBA (Instituto de Oftalmobiología Aplicada) Eye Institute (University of Valladolid). PARTICIPANTS: The mean age of the 79 patients was 66.5years (range 23-90years). For the 124 eyes, the mean spherical equivalent of the sample at baseline visit was -3.59±6.28D (range -21.00D to +4.44D). METHODS: Automated refraction was performed on follow-up visits 1day and weekly for 4weeks. Retinoscopy and subjective refraction were conducted at the Week 4 follow up. MAIN OUTCOME MEASURES: Automated refraction. RESULTS: Sphere, cylinder and mean spherical equivalent, J(0) and J(45) coefficient variabilities were low in all visits. Standard deviations and the limits of agreement were smallest for the last visit. Subjective refraction sphere and cylinder values were more positive than autorefraction by 0.12±0.53D (P=0.031) and 0.23±0.42D (P<0.001), respectively. Comparison between autorefraction and retinoscopy showed a similar trend with the sphere and cylinder differences, 0.32±0.77D and 0.38±0.43D (P<0.05), respectively. CONCLUSIONS: The ARK-30 is sufficiently accurate and repeatable for automated refraction after uneventful cataract surgery. This instrument may be useful for monitoring refractive outcome in these patients.