Fovea Test Research Articles

Macular structure and function and the development of retinopathy in diabetes

Background: The aim of this study was to evaluate the relationship between structural and functional changes identified with the Rarebit fovea test (RFT) in diabetic patients over two years. In addition, we evaluated whether the RFT changes at baseline can predict vascular changes detectable by conventional screening methods four to six years later.Methods: Forty‐two patients with diabetes and 42 age‐matched healthy subjects underwent an initial examination. Two years later, 25 of the diabetic patients and 20 of the controls were re‐examined in the same way. Four to six years later, 40 of the diabetic patients underwent a standard screening examination including fundus photography. After two years, all subjects were examined with the RFT and visual acuity (VA) was assessed. In addition, optical coherence tomography (OCT) and fundus photography were performed on the diabetic patients. At a screening examination of the diabetic patients after four to six years, fundus photographs were reviewed.Results: After two years, a marked difference in RFT results was observed between the 20 normal subjects and the 25 patients with diabetes. Results from other tests (VA and central retinal thickness, as measured with OCT) were unchanged compared with the initial examinations. Fundus photography four to six years later of 40 of the 42 diabetic patients showed an increased incidence of retinopathy unrelated to the RFT findings at baseline.Conclusions: The findings in the current study indicate that the RFT might detect macular dysfunction in diabetic eyes without microvascular changes. This dysfunction increased during a two‐year period and presumably reflects neural impairment in diabetes mellitus but did not predict development of retinopathy during the four to six year period.

Rarebit fovea test in children: reference data for children aged six to 10-years

Introduction: The most common way to examine vision is to measure visual acuity using letter charts. The Rarebit fovea test was developed for detection of small defects of foveal function at a stage before they cause abnormal visual acuity. In a recent study, the RFT was well tolerated in a smaller group of children between seven and nine years of age; however, the number of subjects in that study was small for the determination of reference values, and therefore the aim of the present study was to establish reference values for a larger group of children aged between six and 10-years and to evaluate the learning effect after repeated tests.Methods: Rarebit fovea test data were collected from a group of 108 subjects aged between six and 10-years as part of a screening program at a compulsory school in Stockholm, Sweden. All subjects had good visual acuity and minor refractive errors. They underwent two Rarebit fovea test examinations on one occasion.Results: Rarebit fovea test results ranged from a median mean hit rate of 94.0 to 97.5 per cent for pre‐school and third‐year children, respectively. For the entire group of children the median mean hit rate was 96 per cent (range 57 to 100). The third‐year children performed significantly better than the pre‐school (p < 0.01) and first‐year children (p < 0.05). A significant improvement from the first to second test run was noticed in all groups.Conclusion: The Rarebit fovea test proved to be well tolerated among children in a group of six to 10-year olds and more than 90 per cent of children were considered to give reliable results close to what is normal for adults. It would be interesting to further investigate the potential of the Rarebit fovea test for evaluation of foveal function in children.

Normal values for the Rarebit Fovea Test in children

Abstract Purpose Visual acuity (VA) testing using optotypes is insensitive for detecting subtle defects in the visual function. The Rarebit Fovea Test (RFT) was therefore developed for detection of small defects of the foveal function (Frisén, 2002) at a stage before these defects affect VA. The RFT has been found to be well tolerated by children between 7 and 9 years of age. However, for determination of reference values the number of subjects in previous studies has been to small. The aim of the present study was to establish normal values for children between 6 and 10 years of age, and to evaluate the learning effect after repeated tests. Methods RFT was conducted in a group of 181 subjects between 6‐10 years as part of a screening programme at a compulsory school, in Stockholm, Sweden Results Normal values ranged from median MHR (Mean Hit Rate) 94.0 to 97.5% between pre‐school children and 3rd year children. For the entire group of children the median MHR was 96% (range 57‐100). The 3rd year children performed significantly better than pre‐school children (p&lt;0.01) and 1st year children (p&lt;0.05). An improvement from first to second test was noticed in all groups. There was a very weak but significant correlation between MHR and age (p&lt;0.0001; R2=0.17) and between MHR and VA (p= 0.0093; R2=0.063). Conclusion The RFT proved to be well tolerated among children in an age group between 6‐10 years and more than 90% of the children were considered to give reliable results close to what is normal for adults. Therefore the Rarebit Fovea Test proved to be useful for evaluation of the foveal function in children.

Foveal function in children treated for amblyopia

This study aimed to evaluate foveal function, using three different methods, in children treated for monocular amblyopia. A sample of 24 otherwise healthy children with treated amblyopia and an age-matched control group of 25 healthy children were examined for best corrected visual acuity (BCVA) using a standard decimal (KM) chart and the computerized TriVA method at 50% and 10% contrasts. Foveal function was also measured with the rarebit fovea test (RFT), which is included in the rarebit perimetry program package. This test uses very small and bright dots against a dark background. The result is expressed as mean hit rate (MHR). Amblyopic eyes showed significantly lower BCVA when evaluated with the KM chart and with the TriVA test at different contrast levels, compared with both fellow eyes and control eyes. No statistically significant difference between amblyopic and fellow eyes was found when foveal function was evaluated with the RFT (median MHRs 91.5% and 94.5%, respectively), although results for both amblyopic and fellow eyes were statistically lower than those of the control group (median MHR 97%) (p = 0.001 and p = 0.046, respectively). This might indicate that the RFT provides different information about foveal function than conventional VA tests. The findings in the current study accord with those of other studies reporting abnormalities in the fellow eyes of previously treated amblyopic patients. These findings may reflect a general disturbance in the visual system rather than a monocular adaptation to refractive error or ocular motor disturbance.

A compact rarebit test for macular diseases

BackgroundRarebit testing implies probing for gaps in the neuro-retinal receptive field matrix, using bright microdots on a dark background. Previous reports have found rarebit testing useful for the detection of...

Rarebit perimetry and fovea test before and after cataract surgery

To evaluate the effect of cataract on rarebit perimetry and the fovea test. Twenty-five consecutive patients scheduled for cataract surgery (mean age 63.0 +/- 7.9 years) were examined prior to and after cataract surgery with a complete ophthalmological examination. In addition, the rarebit perimetry (RBP) and the rarebit fovea test (RFT) were performed. Best-corrected visual acuity [BCVA, expressed in minimum angle of resolution (MAR)], RBP and RFT mean hit rate (MHR) improved significantly after cataract surgery. The relative pre-postsurgery difference was larger in the RFT [2.1 standard deviations (SDs)] compared to in BCVA (0.78 SDs). Seven patients had good BCVA (< or = 1.25) and RBP (83-99%) but low RFT (0-66%) before surgery. One patient with low preoperative BCVA (2.5) had a normal RFT (94%). Cataract influenced both the RFT and RBP test, albeit the former more than the latter. The influence of cataract on RFT results, even when visual acuity is decreased only moderately, has to be taken into account when evaluating foveal function in patients with cataract. The larger relative change in RFT compared to BCVA values is thought to indicate that RFT is more sensitive for the effect of cataract. Therefore, RFT appears to be a sensitive test for visual disturbance and can presumably provide additional information at the preoperative evaluation of the patient.

Fixation stability during Rarebit Fovea Test

Background: Unstable fixation has been reported to be a common cause of unreliable results in perimetry. The Rarebit Fovea Test (RFT) is a computerised foveal function test that evaluates the 4 × 3° central visual field, using very small test stimuli. To minimise the test time, no fixation control is used. Instead, stable fixation is facilitated by the use of a dynamic fixation target. The aim of the current study was to evaluate fixation stability during a RFT examination by continuous recording of the eye movements.Method: Twelve healthy subjects were enrolled in the study together with two amblyopic subjects. A three‐dimensional eye tracker was used to measure eye movements during two test sessions. All subjects went through one session of fixation measurement with stimulus presentation and one session without stimulus presentation. Both sessions lasted approximately 90 seconds.Results: Mean hit rate (MHR) in the whole group was 89.7 per cent. Five out of 14 subjects had abnormal RFT results. There was no significant difference in fixation stability either between the test sessions with and without stimulus presentations (p = 0.79) or between the subjects with abnormal (n = 5) and normal (n = 11) MHR, (p = 0.55).Conclusion: Fixation seems stable during RFT testing, thus the test design and fixation target used in the RFT could be considered adequate, at least in subjects with normal or near normal visual function. Further studies are needed to evaluate how different visual abnormalities will affect fixation stability during RFT testing.

A screening test for visual disorders based on Rarebit perimetry

Abstract Purpose To evaluate the clinical usefulness of a newly developed screening program, the VisuBit™ Quick test, based on the Rarebit perimetric technique (Frisén 2002). Methods Twenty‐one subjects (32 eyes), 6 males and 15 females, median age 47 years (27‐67), were examined using the VisuBit Quick and Full test, both including the Fovea test (4x3°visual field) and the Field test (30x20° visual field). Two subjects had amblyopia in one eye, one of these had normal visual acuity in the other eye and one had a history of central serous retinopathy in one eye, 2 subjects had a history of optic neuritis in both eyes and 2 had glaucoma in both eyes. All other eyes were healthy and had normal visual acuity. Results The correlation coefficients between number of unperceived stimuli in the Quick and the Full test were 0.95 in the Fovea and in the 0.86 Field test. In the Quick Field test more than 4 unperceived stimuli predicted a subnormal result (MHR &lt; 90%; Martin &amp; Wanger 2004) in the Full Test. In the Fovea Test more than 2 unperceived stimuli predicted a subnormal results (MHR &lt; 97%; Nilsson et al 2007). The positive and negative predictive values for the Quick Fovea test were 0.95 and 0.77, respectively. Corresponding values for the Quick Field test were 0.95 and 0.85. Conclusion The findings in this pilotstudy indicate that this implementation of the Rarebit perimetric technique may be useful for rapid screening for visual disorders.

Macular abnormalities and the Rarebit Fovea Test

Abstract Purpose: To describe Rarebit Fovea Test (RFT) findings in healthy subjects with normal best corrected visual acuity (BCVA) and macular abnormalities, observed in fundus photographs Methods: Forty‐two healthy subjects, mean age 40 years (SD 10), were recruited as controls in a previous study. Selection criteria were BCVA ≥ 1.0, refractive error within +/‐ 6 D, no ophthalmic or systemic disease. Reported here are RFT and fundus photography findings, and retinal thickness measurement values using optical coherence tomography (Stratus OCT, Carl Zeiss Meditec Int.). Results: Fifteen of the 42 subjects had visible macular changes in the fundus photographs; 10 had drusen and 5 pigment epithelium defects. Mean RFT mean hit rate (MHR) was 99+/‐2%. Two subjects had MHR 91% and 96%, respectively, i.e. below the pre‐defined limit for normality (97%). The subject with a MHR of 91% had drusen, the one with 96% had normal fundus. OCT values were within normal limits in all subjects (center zone mean 212.41 μm, SD 19.35, range 166‐257, inner perifoveal zone mean 238.99 SD 13.34, range 258.3‐308.5 and outer perifoveal zone 241.53 SD 11.54, range 218‐267.8). In the subject with RFT MHR 91% corresponding values were 228 μm, 288.5μm and 249.3 μm and in the subject with RFT MHT 96% 211μm, 279.8μm and 231.8μm, respectively, well inside the normal range. Conclusions: The Rarebit Fovea Test may be useful for discriminating between age‐related macular changes with and without detrimental effects on visual function.

The influence of pupil size, accommodation and higher order aberrations on the retinal image of a Rarebit Fovea Test‐stimulus

Abstract Purpose: To study the influence of pupil size, accommodation and higher order aberrations on the retinal image of the small test stimulus (&lt;0.5´) used in the Rarebit Fovea Test (RFT). Methods: Eleven subjects aged between 22‐36 years participated. All subjects had a corrected visual acuity of 6/6 or better and a refractive error within ± 6 diopters. A PowerRefractorTM measured pupil size and accommodation continuously in all subjects during performance of the RFT. Aberrations were measured with a Zywave aberrometer and Matlab software was used for analysis. Results: Mean variation in accommodation was 0.4D (range 0.22‐0.61D) and mean pupil size was 6.1 mm (range 5.0‐7.8 mm). The aberrations induced a smearing of the retinal image to ~3.5x the stimulus size. When the variation in accommodation was added the total smearing of the retinal image increased to ~4x the stimulus size. Conclusions: The minimum retinal image size of a RFT stimulus is given by aberration and defocus rather than the actual size of the object (stimulus).

Fixation stability during the Rarebit Fovea Test

Abstract Purpose: To evaluate the fixation stability in normal subjects during the Rarebit Fovea Test (RFT). The RFT is a computerized test designed to evaluate the integrity of the central retinal detector matrix. Methods: 11 healthy subjects with visual acuity ≥ 1.0, were examined, using the standard RFT setup, i.e. stimulus presentation on a 17 inch computer screen at a viewing distance of 2 m. The test principle is to briefly present one or two very small (&lt; 0.5’) and bright dots in the central 4x3º visual field. The subject responds by clicking the computer mouse once or twice. The test time is approximately 90 sec and audio‐stimulation is given each time the fixation target is rotated in order to enhance central fixation. Fixation stability was measured during the RFT test using the PowerRefractor™ (Purkinje image eye‐tracking).One eye in each subject was tested. All measurement data were analyzed using SPSS and Matlab. Results: All subjects had normal RFT test results, i.e. close to 100% of the presented dots were perceived. 97% of the testing time fixation was maintained within 1.38° and 100% of the time within 2.76°. Conclusions: Normal subjects appear to maintain stable fixation during the RFT. Further studies of patients with minor macular changes are underway.

Rarebit Fovea Test and OCT findings in diabetes

Abstract Purpose: To evaluate foveal structure and function using optical coherence tomography (OCT)and the Rarebit Fovea Test (RFT) in diabetic patients without known maculopathy orretinopathy. Methods: Forty‐two patients with diabetes mellitus (DM) were selected from the screeningrecords at St Erik Eye Hospital. Inclusion criteria were no previously known macular or otherretinal changes and best corrected visual acuity ≥ 1.0. These patients and 42 healthy controlswere examined with the recently developed RFT and retinal thickness was measuredusing OCT. Lens thickness and light scatter was evaluated by Scheimpflug photography. Results: Significantly more DM subjects (12/42) had a subnormal RFT result compared to thecontrols (2/42) (p = 0.007). The retina in the inner OCT zone was significantly (p&lt;0.05)thinner in DM patients with subnormal RFT compared with the controls. No difference between groups were observed in lens thickness or light scatter. Conclusions: Macular changes, not detected by comventional screening methods, could be demonstrated using both structural and functional tests in a subgroup of patients with DM. Prospective studies are underway to evaluate the prognostic implications.

Early detection of macular changes in patients with diabetes using Rarebit Fovea Test and optical coherence tomography

Aim:To evaluate central retinal thickness and foveal function using optical coherence tomography (OCT) and the Rarebit Fovea Test (RFT) in patients with diabetes without previously known retinopathy or maculopathy.Method:Forty-two patients...

Perception of very small visual stimuli in the fovea: normative data for the Rarebit Foveal Test

Background: Conventional visual tests are not sensitive enough to detect low degree neural damage, as 6/6 (1.0) visual acuity can be upheld with less than two‐thirds of the normal number of optic nerve axons. The aim of the current study was to evaluate the physiologic properties of a new computerised test, the Rarebit Fovea Test (RFT), using very small stimuli, by quantifying the effect of age and binocular summation in relation to stimulus luminance.Methods: The RFT relies on the perception of very small (less than 0.5 minutes of arc) bright stimuli. Two different experiments were performed.1 Thirty‐five subjects (age 19 to 63 years) were tested with five different stimulus luminances, 158, 64, 53, 41 and 33-cd/m2.2 Nineteen subjects (age 19 to 63 years) were tested using binocular stimulation to define the binocular summation.Results: Significantly reduced median hit rates were observed at luminances of 53-cd/m2 or below. Age and mean hit rate correlated negatively at all luminance levels below 158-cd/m2. The mean hit rate from binocular stimulation, compared to the highest value from monocular stimulation in the same subject, was increased by a factor of 1.54 ± 0.45 (SD). No age effect was found regarding binocular summation.Conclusions: The results in the current study indicate that RFT can identify some of the well‐known features of the visual system, that is, the effects of age and binocular summation, provided that the stimulus luminance is adequately selected.

Microdot test of foveal function. A comparison with visual acuity at high and low contrast

To define normal values across age from novel computerized tests of foveal vision and to compare the findings with visual acuity (VA) at high and low contrast. Sixty-one healthy volunteers, aged 22-87, with subjectively normal vision participated in the study. The right eye from each subject was tested with Snellen letter VA at high contrast, at 10% contrast using the Tri-VA test and with the Rarebit Microdot Fovea Test (RMFT), in addition to biomicroscopy and fundus examination. The median letter VA was 0.77 minimum angle of resolution (MAR; range 0.63-1.54) with a significant decline in letter VA with increasing age (r = 0.7, p < 0.001). The median Tri-VA resolution threshold at 10% contrast was 1.8 MAR (range 0.9-4.1) and a significant age effect (r = 0.7) was observed, most pronounced above 65 years. The median RMFT hit rate was 100% (range 97-100) in the age group below 65 years and 87.5% (range 34-98) in subjects older than 65 years. The study shows a decline in foveal function with age with all three methods, reflecting the loss of neural detectors with increasing age. The hit rate to microdot stimuli appears to be a sensitive measure, which can be used for fine-graded evaluation of foveal function.