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[Evaluation of some vision components after implantation of bifocal and monocular intraocular lenses].
Short and long distance vision as well as vision in twilight conditions and dazzle sensitivity in 2 groups of 30 persons have been compared. In one group Corneal-Dual bifocal intraocular lenses and in the other group monocular lenses were implanted. In the former group 0.75 or nearer vision acuity was obtained without any additional correction, while in the latter group obtention of such vision required additional correction to +/- +2 4.0 D sph. Vision in twilight conditions and dazzle sensitivity were similar in both groups, though clearly lower than normal. The study also presents indications and contraindications for implantation of bifocal lenses.
Differences in the accommodation stimulus response curves of adult myopes and emmetropes.
While the accommodation system has been implicated in myopia development, the nature of this relationship remains obscure. This study investigated the differences in accommodation stimulus response curves between adult myopes and emmetropes. Myopic subjects were classified according to age of onset and stability of their myopia. Accommodation stimulus response curves were measured using three different methods: (i) real targets presented at viewing distances of 4 m to 0.25 m, (ii) a target at 4 m viewed through negative lenses of increasing power, and (iii) a target at 0.25 m viewed through positive lenses of decreasing power. A Canon Autoref R-1 measured the accommodation responses at 5 levels of demand (increasing from 0 D to 4 D in 1 D steps). We found significant differences between the three methods used to stimulate an accommodation response in all subject groups, for example, accommodation lags at high accommodative demands were greatest for the negative lens series and least for the positive lens series. In addition, while differences between early-onset myopes, late-onset myopes and emmetropes were not observed, we did observe differences when myopic subjects were reclassified according to whether their myopia was progressing or stable. A reduced accommodation response to negative lens-induced accommodative demand was found in progressing myopes but not in stable myopes. These results provide further evidence for the link between myopia progression and inaccurate accommodation. The data also suggest that adult myopes with stable refractive errors show accommodation responses similar to that of emmetropes.
Recovery of spatial vision during dark adaptation in normal subjects.
We show, how sensitivity to sinusoidally-modulated gratings changes throughout the course of dark adaptation. The luminance required to resolve the bars of a variety of sinusoidal gratings of (0.6-14 c.p.d.) presented in the parafovea, was determined for 30 min following a full bleach. Data obtained for low and intermediate spatial frequencies (0.6 and 3.5 c.p.d.) was qualitatively similar to the classical dark adaptation function, showing discrete cone and rod phases. Threshold to a 14 c.p.d. grating fell initially, then after approximately 10 min, rose by between 0.40 and 1.17 log units. This effect was not apparent for the 8.3 c.p.d. grating, despite the fact that both spatial frequencies must have been detected by cones. The phenomenon has been attributed to rod-suppression of cone-mediated vision.
The infant patient.
The infant patient presents a challenge to the optometrist who must structure an examination within the infant's limited capabilities and then manage a rapidly developing visual system. The present paper provides an overview of infant visual development and the visually guided behaviours expected during normal development. Techniques for assessing vision in infant are reviewed and a recommendation is given for the optometric examination of infants. Some important urgencies, emergencies and causes of visual impairment are highlighted.
Accommodative responses to anisoaccommodative targets.
Young subjects (mean age 25.2 +/- 2.3 years) viewed with symmetric convergence two fusible targets situated at different distances (i.e. anisoaccommodative targets). The fused target was a Maltese cross which subtended 3 degrees at the eye: the right and left arms of the cross were seen by both eyes and each of the other arms was seen by only one eye. The vergences of the anisoaccommodative targets differed by either 3.00 or 0.50 D. Accommodation of each eye was measured by a Canon R1 auto-refractor. There was no evidence of systematic anisoaccommodation. When presented with anisoaccommodative targets, the accommodation of both eyes tended towards a level which was more appropriate to the farther target, i.e. that which required less accommodative effort. Implications of the findings for optometry are briefly discussed.
Accommodation to perceived depth in stereotests.
The question of whether the eye may accommodate to the stimulus provided by apparent depth in stereograms is considered theoretically in relation to the magnitudes of the disparities and viewing distances found in typical clinical stereotests. It is concluded that, for the relevant range of disparities (< or = 2000 arc sec), any shift in accommodation is likely to be small (< or = 0.15 D). An experimental study with two different clinical stereotests (Lang, TNO) confirms this prediction.
Computerized dynamic visual acuity test in the assessment of vestibular deficits.
OBJECTIVE: The study was designed to measure dynamic visual acuity (DVA) during head movement as an assessment of the functional impact of vestibular deficits. STUDY DESIGN: The study design was a prospective, clinical study. SETTING: The study was performed in a tertiary, ambulatory referral center. PATIENTS: Forty-two normal subjects, 29 patients with unilateral vestibular loss, and 26 patients with bilateral vestibular hypofunction who were 19-87 years of age were examined. INTERVENTION: Diagnostic intervention was performed. MAIN OUTCOME MEASURE: Main outcome measures included the reliability, sensitivity, and specificity of a computerized test that measures visual acuity during head movement in normal subjects and in patients with vestibular deficits. RESULTS: The computerized DVA test was reliable in both normal subjects (intraclass correlation coefficient [ICC] r=0.87) and in patients with vestibular deficits (ICC r=0.83). The sensitivity of the DVA test was 94.5% and the specificity was 95.2%. The positive predictive value (individuals who test positive on the DVA test who will have a vestibular deficit) was 96.3%. The negative predictive value (individuals who test negative on the DVA test who will not have a vestibular deficit) was 93%. CONCLUSIONS: The computerized DVA test is reliable and is able to distinguish among normal subjects and patients with vestibular deficits.
[Development of visual functions in children from birth to 6 years of age].
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[Neuro-psychological development of vision in children older than 6 years of age].
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The value of electro-oculography for the diagnosis of tapeto-retinal degenerations.
The particular value of the EOG for diagnosis and prognosis has been demonstrated with the findings and case histories of seven patients. We have shown (1) that the EOG in connection with the ERG has contributed decisively to the differentiation of numerous types of tapeto-retinal dystrophies; (2) that the EOG is, as a rule, very valuable in distinguishing between tapeto-retinal dystrophies and flourishing or healed chorioretinitis, and (3) the different values of the other examination methods (visual field, colour vision tests, dark adaptation, angiography) in comparison with the electrophysiological methods. We have used the same methods as were used in previous examinations.
Clinical analysis of colour vision deficiencies with The City University test.
The City University colour vision test (CUCVT) was used for the examination of 158 subjects suffering from congenital colour vision defects (36 protanopes, 122 deutanopes) and its results were compared with that of an anomaloscope and of the panel D-15. 23% of the subjects classified as protanopes and 98% of the subjects classified as deuteranopes by means of the anomaloscope were also classified as such by means of the CUCVT, while 93% of the subjects classified as protanomalous and 90% of the subjects classified as deuteranomalous by means of the anomaloscope gave normal answers at the CUCVT. The results of the CUCVT were almost the same as with panel D-15 except protanopia. The colour spots of each plate of the CUCVT were plotted on a CIE chromaticity diagram and the results of this study are also reported.
Projected color slides as a method for mass screening test for color vision deficiency (a preliminary study).
This article compared the efficiency of the mass screening test with projected color slides in detecting color-blindness with the authentic classic method of Ishihara. The study was conducted in a randomly selected lecture room with 104 students aged between 19-25 years (median 21). Using Ishihara projected slides, performed mass screening test. Re-testing was done individually with printed Ishihara plates. Six male and one female with color-blindness were detected. The frequency of color-blindness was 13.6% among males, with a total incidence of 6.7%. The results of two testing methods were compared statistically. Sensitivities and specificities of both tests were 100%. Using projected slides of Ishihara plates instead of the authentic method is an effective and timesaving method for detecting color-blindness. This method can be suggested as a mass-screening test and might be beneficial in detecting color-blindness in large populations such as students, soldiers, and so on.
Hyperacuity test to evaluate vision through dense cataracts; research preliminary to a clinical study. III. Data on normal subjects obtained with and without a pseudo-nuclear cataract 6/60 (20/200) at the Aravind Eye Hospital, Madurai, India.
Using a recently discussed three-point Vernier alignment test, data were obtained on normal subjects with and without a pseudo-nuclear cataract 6/60 (20/200) at the Aravind Eye Hospital, Madurai, India. This experiment is a critical control exercise. The pseudo-cataract caused measurably and predictably reduced Vernier alignment thresholds, there were no meaningful differences between eyes, and necessary modifications in protocol for a later clinical study were defined.
Hyperacuity test to evaluate vision through dense cataracts; research preliminary to a clinical study. IV. Data on patients with macular degeneration and minimal media disorders obtained with and without a pseudo-nuclear cataract 6/60 (20/200) at the Aravind Eye Hospital, Madurai, India.
Using a recently discussed three-point Vernier alignment test, data were obtained on patients with macular dysfunctions with and without a pseudo-nuclear cataract 6/60 (20/200) at the Aravind (Free) Eye Hospital, Madurai, India. The pseudo-cataract caused measurably and predictably reduced Vernier alignment thresholds, and necessary modifications deemed to be necessary in the protocol for later study are defined.
Hyperacuity test to evaluate vision through dense cataracts; research preliminary to a clinical study. II. Initial trials of the India instrument and HASP protocol at Aravind Eye Hospital, Madurai, India.
BACKGROUND. Our purpose is to develop a clinical test capable of assessing vision through dense cataracts (and other advanced media opacities) before surgery. Because such anomalies are endemic in the developing world, it was desirable to conduct a clinical study of a prototype India instrument and HyperAcuity Study Protocol (HASP) in such a setting. This investigation, preliminary to a planned clinical study, was conducted at the Aravind (Free) Eye Hospital, Madurai, India. EXPERIMENTAL. The preliminary HASP protocol, developed in Berkeley, was adapted to existing clinical practices in Madurai. Included was a new test of visual acuity, the Gap "VA" test, developed as part of the revised protocol. The rational for this test, methods used, and sample data are presented. A Vernier alignment test (one of the hyperacuities) is used to assess vision through dense ocular media disorders. The task of the patient is to align vertically three high luminance, discrete visual stimuli. The revised HASP protocol and adapted India instrument were tested upon patients with advanced cataracts. The cataract grading system used in these studies (provided by Drs. N. V. Projna and G. Rohini) is defined. Patients were tested before and shortly after surgery. This investigation allowed us to refine the test protocol and instrument design preparatory for a clinical study of HASP. A much simpler/cheaper version of the India instrument will be used in the planned clinical study. Additional experiments are scheduled in order to address issues which require resolution before initiation of next-stage testing. In part, in these papers, we seek to help others understand some problems encountered when conducting research in a developing world environment, even a very good one!
Use of a group screening test for colour vision defects.
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The development and assessment of a self-perceived quality of vision questionnaire to test pseudophakic patients.
PURPOSE: To develop and test a questionnaire to assess quality of vision in pseudophakic patients. METHODS: The problems with existing health measurement scales and the need for a new questionnaire are first discussed. Development of the new questionnaire from concept to completion is presented and all stages discussed. The questionnaire is then tested for internal consistency, reliability and validity. RESULTS: The Cronbach Alpha for internal consistency was 0.92. British Standards Institution repeatability coefficient was satisfactory at 6.6. Discriminant construct validity testing by extreme groups demonstrated excellent discrimination between patients with functionally significant posterior capsule opacification (PCO) and no significant PCO (Mann-Whitney U test, p = 0.001). CONCLUSION: The questionnaire is validated as a robust, stable measure of pseudophakic visual symptoms with a high degree of clinical utility. It should be invaluable for the many studies that compare outcomes from different forms of modern cataract surgery with implantation of different intraocular lenses.