Rarebit Perimetry Research Articles

A New Visual Field Test in Empty Sella Syndrome: Rarebit Perimetry

Several visual field defects can be seen in empty sella syndrome (ESS). In this study, the authors aimed to evaluate the visual field defects in patients with ESS by rarebit perimetry and to compare the results with Humphrey perimetry. Left eyes of 13 patients with ESS and left eyes of 15 age-matched normal subjects were included in the study. Visual field testing was performed by Humphrey Visual Field Analyzer II (Fastpack 30-2 strategy) and rarebit perimetry (regular test). Statistical analysis was performed by independent-samples t-test, Mann-Whitney U test, receiver operating characteristic (ROC) curves, and Pearson correlation test. Humphrey perimetry mean deviation was -3.67 dB in control group and -6.06 dB in patients with ESS (p=0.12). Mean hit rate calculated by rarebit test was 91.8% in control group and 75.9% in cases with ESS (p=0.005). Area under ROC curve was 0.756 for Humphrey visual field test and 0.827 for rarebit hit rate (p=0.59). There was a significant correlation between rarebit hit rate and Humphrey visual field test mean deviation (r=0.755, p<0.001). Rarebit perimetry correlates significantly with Humphrey perimeter in detecting visual field defects related with ESS and has a higher sensitivity and specificity.

Rarebit Perimetry and Frequency Doubling Technology in Patients with Ocular Hypertension

To test the capability of rarebit perimetry (RP), a recent non-conventional perimetric technique, in detecting early functional damage in subjects with ocular hypertension (OHT) and to compare RP findings with those obtained by frequency-doubling technology (FDT) perimetry. Thirty patients with OHT were matched with 30 healthy subjects. All were tested with RP and FDT. Frequency-doubling technology mean deviation (MD) and pattern standard deviation (PSD), as well as RP mean hit rate (MHR), of the two groups were analyzed. The agreement between the two techniques was tested by Kappa analysis. In the OHT group the mean (SD) FDT MD was 0.5 (2.1), the mean (SD) FDT PSD was 4.2 (1.6), and the mean (SD) RP MHR was 81.4 (6.7). In the control group, corresponding values were mean (SD) FDT MD 1.1 (1.4), mean (SD) FDT PSD 3.0 (0.3), mean (SD) RP MHR 96.2 (2.0). The differences between the two groups were not significant for the studied indexes. Eleven (36.6%) out of the 30 OHT eyes had abnormal RP results; 12 (40.0%) eyes had abnormal FDT results. Five (16.6%) eyes had abnormal RP and FDT findings. Only 1 eye (3.3%) in the control group had abnormal RP results and 3 eyes (10.0%) had abnormal FDT results. RP and FDT showed a moderate agreement (Kappa=0.43; 95% CI: 0.42 to 0.51). RP and FDT showed VF defects not shown in standard automated perimetry in the OHT group. This may be indicative of an increased risk in developing glaucoma, even if a gold standard for detecting subtle defects is not currently available. RP has the additional advantage of not requiring any expensive device to be used. The poor agreement between these techniques in identifying eyes with early damage warrants further investigations. Large longitudinal studies are needed before defining the role of RP in early glaucoma diagnosis.

Rarebit Perimetry in Normal Subjects: Test–Retest Variability, Learning Effect, Normative Range, Influence of Optical Defocus, and Cataract Extraction

To study normative ranges, learning effect (LE), test-retest variability (TRV), and influence of blur and cataract in normal subjects by using rarebit perimetry (RBP). Seventy-five normal subjects underwent visual field (VF) testing with standard automated perimetry (SAP) and RBP. LE and TRV for RBP were assessed in repeated examinations conducted on four different days. LE was evaluated by comparing results from the first with those of the other three sessions. TRV was studied by calculating differences between retest for each combination of single tests. The blur effect was evaluated by repeated tests with spherical lenses added to the optimum refractive correction (+/-1.00 to +/-6.00 D). The cataract effect was studied in 23 subjects who underwent RBP 1 week before and 1 month after cataract surgery. Mean hit rate (MHR) and mean miss rate (MMR) were analyzed for single areas and test duration. The mean MHR was 91% +/- 5.7% (range, 78%-99%); the mean MMR ranged from 4.0% to 13.8%. MHR significantly decreased with age (mean, 0.21%/year). Mean test time was 268 +/- 34.1 seconds. No significant LE was observed. TRV was significantly higher in the central VF zone and in elderly subjects. MHR increased with refractive blur and significantly decreased after cataract surgery. Effects of blur and cataract extraction were significantly higher in the central VF zone, especially in elderly subjects. RBP is a rapid and easily accessible VF test. RBP testing did not show a significant LE; however, inter- and intrasubject variability were consistent. Blur and media opacities may give false-positive results in RBP, especially in the central VF, and should be considered.

How robust is the optic chiasm? Perimetric and neuro-imaging correlations

Analysis of form and function relationships with tumour-mediated dislocations and deformations of the optic chiasm. Results of magnetic resonance tomography and two forms of quantitative, computerized perimetry were contrasted in 31 patients with pituitary adenomata impinging on the chiasm, prior to treatment. Perimetric abnormalities ranged from none to modest. High-pass Resolution Perimetry (HRP) produced abnormal results in 10 cases and RareBit perimetry (RBP) in 15 cases. Overall, field defects and qualitative stages of deformation and dislocation of the chiasm were well correlated. Among quantitative indices, the best correlations were obtained by a measure of the cranio-caudal position of the chiasm. On average, an elevation of the chiasm by 6 mm will be associated with abnormal visual fields in 50% of the cases. An additional elevation of 5 mm will raise the incidence of field defects to 90%.

Rarebit Perimetry and Optic Disk Topography in Pediatric Glaucoma

To determine the relationship between visual field and optic nerve topography findings in a cohort of children with pediatric glaucoma and an age-matched and sex-matched control Fifteen children, aged 6 to 15 years, with pediatric glaucoma in at least one eye and 15 age-matched and sex-matched healthy children were examined with best-corrected visual acuity and perimetry. When possible, scanning laser topography of the optic disk (ie, Heidelberg retinal tomography) was performed. Of 27 eyes in 15 children with pediatric glaucoma examined with Goldmann perimetry, 15 eyes (55%) had a normal visual field. Of 24 eyes examined with Rarebit perimetry, 8 eyes (33%) showed normal results and 16 eyes (67%) showed an abnormally low hit rate (ie, the fraction of seen targets vs presented targets). Nine of the 15 eyes showing normal Goldmann visual fields had a subnormal Rarebit hit rate. All children in the control group had normal Rarebit visual fields. Heidelberg retinal tomography could be performed in all healthy children and in 22 eyes of 13 children with pediatric glaucoma. The concordance between the Heidelberg retinal tomography classification (ie, normal or glaucoma) and the Rarebit results was high (Cohen's kappa = 0.79). A statistically significant correlation (r = 0.66, P = .006) between Rarebit hit rate and Heidelberg retinal tomography glaucoma index was found in the glaucoma group. Rarebit perimetry detected glaucomatous damage in various types of pediatric glaucoma, and can be assumed to be of value in both diagnosis and follow-up. In 13 children with glaucoma, Heidelberg retinal tomography could be performed. The results conformed well to Rarebit findings.

Rarebit and frequency‐doubling technology perimetry in children and young adults

To describe the outcome of visual field examinations performed with rarebit (RB) and frequency-doubling technology perimetry (FDT) in children and young adults. Twenty-one children (aged 6.5-12 years) and 30 teenagers and young adults (aged 14-20 years), participated in the study. Reliable RB examinations were carried out in 76% of the younger group and 90% of the older group. Corresponding values for FDT were 57% and 90-95%, respectively. The RB results were very similar to those previously obtained in adult subjects, while some subjects showed borderline values in FDT, depending on the criteria used. The RB perimetry was preferred by 88% of the examined subjects. Rarebit perimetry seems useful for visual field examination in children aged 7 years and over, if age-corrected normative data are established; this test was also preferred by the tested subjects. No adaptation or special instructions were needed and the children found it rather amusing.

Visual function in young adults following intrauterine growth retardation.

Intrauterine growth retardation (IUGR) resulting in infants born small for gestational age is a known risk factor for neurologic deficits and may predispose to poor cognitive development later in life. We recently found an association between IUGR and a reduced neuroretinal rim area at 18 years of age. We evaluated the possible association between IUGR and visual function. We studied 26 subjects who had been born small for gestational age and 20 subjects whose birth weights were appropriate for gestational age (controls) using letter acuity thresholds, color vision testing, full-threshold frequency doubling technology perimetry, and rarebit perimetry at 18 years of age. gestational age had a rarebit hit rate below the normal range as compared with none of the controls (P = .006). These 8 subjects had a significantly smaller rim-disc ratio compared with the subjects who were small for gestational age who had a normal rarebit hit rate (P = .047). The frequency doubling technology indices did not differ significantly between the control group and the group that was small for gestational age, nor did the visual acuity, refraction, and color vision test results. These data indicate that IUGR is associated with an increased rate of impaired visual function, which can be detected by using rarebit perimetry but not frequency doubling technology perimetry, visual acuity, or color vision tests.

Vigabatrin-associated loss of vision: rarebit perimetry illuminates the dose-damage relationship.

The utility of vigabatrin in the treatment of epilepsy is partially offset by its retinal toxicity. The relationship between dosage and damage is obscure. This may be due to perimetric shortcomings. The new technique of rarebit ('microdot') perimetry might be more informative. Twelve patients who had been treated with vigabatrin for various durations were examined by manual, kinetic perimetry and by rarebit perimetry. Rarebit results differed significantly between patients and normal controls and rarebit deficits were directly proportional to cumulated vigabatrin doses (correlation coefficients were - 0.92 in the nasal field and - 0.82 in the temporal field). Manual perimetry results were less clearly related to dosage (r = - 0.54 and r = - 0.73, respectively). Rarebit perimetry indicates that each treated subject will develop visual loss and that visual loss will be proportional to the accumulated dose. Conventional perimetry is less well suited to detecting and quantifying vigabatrin-associated visual loss.