Comparison of the Standard Pseudoisochromatic Plates to the Ishihara color vision test

The Standard Pseudoisochromatic Plates (SPP) color vision test was compared to the Ishihara color vision test with respect to screening validity, digit confusion errors, and individual plate efficiency. Results from 315 1st and 3rd grade males confirmed previous reports that the SPP is an effective screening test. Moreover, the SPP test was superior to the Ishihara test with respect to digit confusion errors. Color normal children made about 5 to 7 times as many errors on the Ishihara test as on the SPP. Screening inefficiency values of individual plates of both tests were calculated. A high inefficiency value of a SPP plate was usually caused by its inability to detect color defective subjects.     

Comparison of Ishihara and Hardy-Rand-Rittler Pseudoisochromatic Plates in Non-Arteritic Anterior Ischaemic Optic Neuropathy

Pseudoisochromatic plates, such as Ishihara and Hardy-Rand-Rittler (HRR) tests, are designed as screening tools to test colour vision defects. The tests are often designed to detect congenital red-green colour blindness and their measurement properties for acquired optic neuropathies are not known. The aim of this study is to determine the sensitivity and specificity of Ishihara and HRR pseudoisochromatic plates in detecting dyschromatopsia in patients with unilateral non-arteritic anterior ischaemic optic neuropathy. Nineteen such patients were tested using Ishihara and the HRR plates in the affected and the unaffected (control) eye. The results were correlated to that on an anomaloscope (Oculus HMC Anomaloskop MR^®). Mild deuteranomaly was the dyschromatopsia detected by an anomaloscope in the affected eye of the patients. The sensitivity and specificity of the Ishihara test in the affected eyes are 75% and 40%, respectively. The sensitivity and specificity of the HRR test in eyes affected with non-arteritic anterior ischaemic optic neuropathy are 100% and 20%, respectively. It is concluded that the anomaloscope that was considered the “gold standard” has several limitations and may not detect all acquired dyschromatopia. On the other hand, whilst it is correct that pseudoisochromatic plates are screening tests and the results must be correlated with other optic nerve functions, the HRR test has a higher sensitivity and specificity than Ishihara colour plates in detecting dyschromatopsia in non-arteritic anterior ischaemic optic neuropathy eyes.     

Pseudoisochromatic plate design--Macbeth or tungsten illumination?

Three sets of pseudoisochromatic plates were evaluated by photometry and colorimetry. The luminance contrast between the figure and background was measured and compared with a contrast detection threshold. The chromaticity coordinates of the figure and background were evaluated on the basis of how closely they approached a dichromatic line of confusion. The separation of the coordinates of the figure and background are a measure of the severity of the defect for which the plate tests. The plates were evaluated under both Macbeth (C) and tungsten (A) illuminants; two sets of plates were found to be better designed for tungsten illumination.     

Technical Note: The effect of refractive blur on colour vision evaluated using the Cambridge Colour Test, the Ishihara Pseudoisochromatic Plates and the Farnsworth Munsell 100 Hue Test

The results of a prospective study examining the effect of refractive blur on colour vision performance in normal subjects measured with three different colour vision tests are reported. The Farnsworth Munsell 100 Hue (FM100) and Cambridge Colour Test (CCT) results were significantly affected at +6 D of spherical refractive blur, whereas those from the Ishihara Pseudoisochromatic Plate (IPP) test were not. In a clinical setting, correction of refractive error up to 3 D for colour vision testing with these tests may not be required. Poor colour vision should not be attributed solely to refractive causes of poor visual acuity (Snellen equivalent: >6/36). Fastest test times were achieved using IPP, followed by CCT.     

Phakic intraocular lenses: part 2: results and complications

The second part of a review of phakic intraocular lenses (pIOLs) addresses results and complications with current pIOL models. Phakic IOLs demonstrate reversibility, high optical quality, potential gain in visual acuity in myopic patients due to retinal magnification; correction is not limited by corneal thickness or topography. With proper anatomical conditions, pIOLs also show good results in hyperopic patients. Toric pIOL designs enable spherocylindrical correction. Complications are rare and primarily related to pIOL position and type. The main complications of angle-supported anterior chamber pIOLs are glare and halos, pupil ovalization, and corneal endothelial cell loss; of iris-fixated anterior chamber pIOLs, chronic subclinical inflammation, corneal endothelial cell loss, and dislocation or pupillary block glaucoma; and of posterior chamber pIOLs, anterior subcapsular cataract formation, pigment dispersion, and luxation or pupillary block glaucoma. No causative relationship between pIOL implantation (of any pIOL type) and retinal detachment has been established.