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PubMed1995

Age-related standards for ordinal data: modelling the changes in visual acuity from 2 to 9 years of age.

The visual acuities of 1140 children between the ages of 2 and 9 years were measured using the Sonksen-Silver Acuity System (SSAS) from a distance of 3 metres. Ordered logistic regression was used to construct smoothly changing age-related reference ranges for the proportions of children at different ages expected to have acuities in each of three ordinal categories. Exponential functions of age fitted the data better than polynomials. The resulting reference ranges can be used to derive the ages at which a given percentage of children achieve each of the acuity cut-offs. However, since it is unlikely that all children will be available for testing at the exact appropriate age, two possible alternatives are introduced and discussed. First, a new ordinal category that would result in a chosen outcome at a pre-selected age is calculated. Secondly, because it may be more feasible to use the current SSAS system whilst varying the distance of measurement, age-related standards showing the distances required to give constant pass-rates with the usual letter-sizes are also presented.

Age Factors↗

PubMed1982

Visual acuity of infants with ocular diseases.

We tested the visual acuities of 110 infants with ocular disorders by a preferential-looking technique that provides fast, accurate measurements for preverbal children. The results were used to confirm initial clinical evaluations and to prescribe and monitor treatment. The test was particularly helpful in assessing the effects of occlusion therapy. The child sat on a parent's lap 50 cm away from a black partition containing two circular screens. A grating was projected on one screen and a homogeneous field was projected on the other. A hidden observer watched the infant's eye and head movements to determine which screen was preferred.

Age Factors↗

PubMed1994

Variation of the visual acuity--luminance function with background colour.

The relationship between visual acuity (VA) and background colour is a question that still creates a certain amount of confusion even today, although most authors agree that colour background does not basically affect VA, or at best, values that are only slightly better are obtained with monochromatic yellow light. The object of this paper is to try to clarify if, when the axial chromatic aberration (ACA) has been compensated for, certain differences due exclusively to colour persist or not. In order for this, the VA-luminance functions with red, green, blue and white backgrounds have been measured for two emmetropic observers, before and after compensating for the ACA. The results show that after the compensation, the curve corresponding to red is above the one corresponding to blue, with the one corresponding to green in between. The achromatic function (white background) practically overlaps with the green one. This behaviour is consistent with that shown recently for contrast sensitivity functions (CSFs). However, the asymptotic values are identical for the three colours, and so, it is understandable that no significant differences are normally found when only a standard measurement of VA is taken using the typical illumination from an optotype projector.

Adult↗

PubMed1991

[Effect of faulty refraction and artificial media opacities on visual acuity perimetry].

For resolution perimetry according to Frisén, 50 test locations in the central visual field are examined. Compared with conventional perimetry the test time is rather short: 5-10 min per eye. For routine application of this new perimetric technique it is important to know to what extent the threshold values are affected by refractive defocus or media opacities. To answer this, 20 eyes of 20 normal subjects were tested both with a refractive defocus (0, +1, +3, +6, +9 and +12 dpt sph) and with artificial media opacities, using occluders according to Bangerter to reduce visual acuity to average values of 0.61, 0.27, 0.14 and 0.07. The results of the present study show that even a slight refractive defocus or a slight artificial media opacity induces a marked increase in threshold values. Mean Ring score MR and defocus are quadratically correlated (MR2/defocus: r = 0.9973, p less than 0.001), and MR is linearly correlated with the Reduced Luminance Factor 1(15) (MR/1(15): r = 0.9978, p less than 0.001). Clinical evaluation of the test results of the ring perimeter thus has to take into account the influence of refractive defocus and media opacities.

Adult↗

PubMed1995

[Measurement of the visual acuity to networks with the Teller's cards: efficient detection of amblyopia in infants and young children?].

The reliability of measurement of visual acuity by Teller's card was studied in young children under 18 months (3 to 42.5 months) to detect amblyopia. Repeated tests with Teller's cards were performed in children (two exams at least) divided into several pathologies. Visual acuity changed over time (in 2000 exams). Results were compared with those given by drawing tests (Pigassou) at two years and a half. Middle amblyopia occurred in 44%, low amblyopia in 40% and high amblyopia in 16%, as the results by Teller's cards were considered as normal. These results were found in 54% among the 2000 Teller's studied. Teller's test was thus shown to be unreliable to detect middle or low amblyopia. Objective réfraction is required.

Amblyopia↗

PubMed2004

Corneal refractive therapy, uncorrected visual acuity, and "E" values: personal experiences.

PURPOSE: The author describes selected aspects of his clinical experience in fitting and prescribing orthokeratology lenses to temporarily reduce or eliminate myopia. The precision of videokeratography (VK) data in determining corneal sagittal depth is examined. Treatment outcomes are analyzed after overnight wear of two proprietary corneal remodeling systems. Two case reports describing off-label treatments are presented. METHODS: A retrospective analysis was performed of the baseline VK data of 25 consecutive candidates (50 eyes) for corneal remodeling, captured with a Keratron topographer. Sixteen consecutive patients fitted with Paragon corneal refractive therapy (CRT) lenses were compared against an age- and sex-matched group of patients fitted with the Mountford BE lens for 1-day, 1-week, and 1-month uncorrected visual acuity. RESULTS: The mean +/- SD of the apical radius ("Ro") and corneal eccentricity ("E") values was 0.03 +/- 0.01 mm and 0.03 +/- 0.01 degrees , respectively, indicating a spread of 24 microm in the sagittal elevation data. Mean target myopia and 1-day uncorrected visual acuity were -1.71 +/- 0.71 diopters and 20/20 +/- 20/0.86, respectively, for the Paragon CRT lenses and -2.30 +/- 0.89 diopters and 20/31 +/- 20/20.6, respectively, for the Mountford BE lenses. CONCLUSIONS: The Paragon CRT and the Mountford BE lenses delivered impressive reductions in uncorrected visual acuity after the first night of overnight wear. The Paragon CRT lens had the advantage of not requiring a previous overnight lens trial before commencing the treatment program.

Adolescent↗

PubMedDate not supplied

Visual acuity deficits following neonatal lead exposure: cholinergic interactions.

Clinical reports describe long-term alterations in the spatial resolution properties of the visual system following developmental lead (Pb) exposure. To determine if the spatial resolution limit, visual acuity, of the adult rat was altered following low-level, neonatal Pb exposure psychophysical studies were conducted. To examine possible mechanisms of action (and an additional stressor) the effects of scopolamine were studied in the psychophysical procedure. [3H]-QNB binding was analyzed in retina, superior colliculus, lateral geniculate nucleus and visual cortex. Neonatal hooded rats were exposed to Pb (days 0-21) via the milk of dams drinking 0.2% Pb acetate. Visual acuity was 1.8 cycles/degree in controls compared to 1.3 cycles/degree in the Pb group. Scopolamine caused dose-dependent decreases in spatial resolution with decreases at higher spatial frequencies being greater in the Pb group. Positive controls revealed the effects to be centrally mediated. A decrease in the [3H]-QNB binding was found only in the visual cortex. The results suggest that long-term effects of developmental Pb exposure may be directly on the visual cortex.

Animals↗

PubMed2005

Visual acuity and contrast sensitivity comparison between Tecnis and AcrySof SA60AT intraocular lenses: A multicenter randomized study.

PURPOSE: To evaluate best corrected visual acuity (BCVA) and photopic and mesopic contrast sensitivity in pseudophakic patients implanted either with the aspheric intraocular lens (IOL) designed to correct for corneal spherical aberration or with a conventional IOL. SETTING: Three surgical centers participated this prospective randomized masked comparative study. METHODS: Thirty eyes of 30 patients after aspheric lens implantation (Pfizer/Pharmacia Tecnis Z9000) were compared with 30 eyes of 30 age-matched patients after conventional lens implantation (Alcon AcrySof SA60AT). Two to three months after surgery, best spectacle corrected distance visual acuity was measured using the Early Treatment Diabetic Retinopathy Study chart. Contrast sensitivity was measured by sinusoidal grating charts for distance at photopic (85 cd/m(2)) and mesopic (6 cd/m(2)) luminance level with optical correction in place. Tested spatial frequencies were 1.5, 3, 6, 12, and 18 cycles per degree (cpd). RESULTS: The mean BCVA was -0.053 +/- 0.044 logMAR in eyes with the aspheric Tecnis IOL and 0.006 +/- 0.059 logMAR in eyes with the conventional AcrySof IOL (P=.0001). Eyes with the aspheric IOL showed better contrast sensitivity at spatial frequencies of 3 cpd (P<.05) and 6, 12, and 18 cpd (P<.01) in photopic and in mesopic conditions. Peak improvement occurred at 18 cpd and was 36% (0.29 log units) in photopic and 54% (0.27 log units) in mesopic conditions. CONCLUSIONS: The aspheric Tecnis IOL yielded better BCVA and better distance contrast sensitivity than the conventional IOL. The differences were clinically significant for higher spatial frequencies. The results give some suggestions for further studies.

Aged↗

PubMed1990

Visual acuity measured with clinical Maxwellian-view systems: effects of beam entry location.

Maxwellian-view projection systems are used clinically to evaluate visual acuity in cataract patients because they allow the clinician to direct a beam of light around any localized opacity. However, theory predicts that, as the beam is displaced from the visual axis, acuity will suffer with those instruments using white light due to the effects of ocular chromatic aberration. Using three commercially available Maxwellian-view instruments, we examined the decline of visual acuity with beam decentration in the clear pupil of normal subjects. With all three instruments (Lotmar interferometer, Randwal interferometer, and the Potential Acuity Meter) acuity fell by a factor of 3 for beams placed near the edge of a dilated pupil. Control experiments with monochromatic light indicated that lateral chromatic aberration was the primary cause of acuity loss with the two interferometers, but other off-axis aberrations also contributed to the acuity loss with the Potential Acuity Meter. A detailed analysis of the beam in the pupil plane indicates that the beam's complex structure may be altered if the beam strikes the iris or an opacity in the ocular media. These findings indicate that potential acuity may be significantly underestimated with polychromatic Maxwellian-view systems.

Equipment Design↗

PubMed2000

[Long-term results of combined glaucoma and cataract surgery. Intraocular pressure and visual acuity follow-up].

BACKGROUND: The aim of this investigation was to ascertain the long-term results of intraocular pressure and visual acuity after combined glaucoma and cataract surgery. PATIENTS AND METHODS: Between 1994 and 1997, 65 eyes underwent Pham's sclerectomy and at the same time 65 eyes underwent Elliot's trephination with scleral flap. Both procedures were combined with phacoemulsification and implantation of a posterior chamber lens. The mean follow-up was 21.9 +/- 11.0 months. RESULTS: The IOP of eyes that underwent Pham's sclerectomy decreased from 21.4 +/- 3.3 mmHg to 14.9 +/- 2.7 mmHg and of eyes that underwent Elliot's trephination from 24.6 +/- 7.3 mmHg to 15.8 +/- 2.6 mmHg. Thirty percent of the eyes with Pham's sclerectomy and 25% with Elliot's trephination required an additional medication. In both procedures the overall visual acuity increased by three lines. CONCLUSIONS: These results of combined glaucoma and cataract surgery confirm their efficiency. From the economical aspect, combined glaucoma and cataract surgery has gained increasing significance.

Aged↗

PubMed2000

Perception of Purkinje vessel shadows and foveal granular pattern as a measure of potential visual acuity.

PURPOSE: To compare perception of 2 entoptic phenomena, the Purkinje vessel shadows and the foveal granular pattern, as measures of retinal visual acuity using a transscleral illumination technique that bypasses the anterior segment. SETTING: Retinal Vascular Center and General Eye Clinic, Wilmer Ophthalmological Institute, Johns Hopkins Hospital, Baltimore, Maryland, USA. METHODS: Both eyes of 85 patients with clear ocular media, many with retinal disease, were tested for perception of these entoptic phenomena. Also, retinal visual acuity was measured with a Potential Acuity Meter through the current refractive correction. RESULTS: Of 114 eyes with retinal acuity of 20/40 or better, 99% perceived the Purkinje vessel shadows and 86% perceived the foveal granular pattern. Of 45 eyes with retinal acuity of 20/80 or worse, 73% perceived the Purkinje vessel shadows and 4% perceived the foveal granular pattern. CONCLUSION: Perception of the Purkinje vessel shadows does not distinguish between good and poor retinal acuity, whereas nonperception of the vessel shadows strongly suggests poor acuity. Perception of the foveal granular pattern, on the other hand, provides a positive indication of good retinal acuity and will likely prove to be predictive of good vision after removal of significant media opacity.

Cataract↗

PubMed1988

Refractive error and preferential looking visual acuity in infants 12-24 months of age: year 2 of a longitudinal study.

This paper presents data from year 2 of a study assessing changes in visual acuity and refractive error in normal, healthy infants between birth and 24 months of age. Visual acuity and refractive error measurements were taken at 2-month intervals on 18 infants, 12-24 months of age. The acuity card preferential looking procedure and Mohindra's near retinoscopy were used for acuity and refractive error measurement. Response to the Stereo Fly was also observed. Mean acuity improved from 6.4 cycles per degree (cpd) (20/93) at 12 months to 20.5 cpd (20/29) at 24 months (SD = 0.5 octave). Refractive error remained in low hyperopia (X = 0.4D, SD = 0.5D). Amount and frequency of astigmatism showed little change. Response to the Stereo Fly improved from 0% at 12 months to 87% at 24 months. The acuity card procedure was easily accomplished, but more difficult with these children at 12-24 months of age than when previously tested between 0-12 months of age.

Analysis of Variance↗

PubMed1992

Low contrast visual acuity changes in human immuno-deficiency virus (HIV) infection.

A pilot study of low contrast visual acuity testing using Regan Charts has been undertaken in 34 patients seropositive for Human Immuno-Deficiency Virus and 20 normal control subjects. Low contrast visual acuities of the HIV (+) patients both with and without HIV retinopathy were found to be significantly lower than the age-matched controls (p < 0.01). This finding is probably attributable to pathology related to HIV in the visual pathways/Central Nervous System. Lowest contrast Chart (Chart C) was found to be a useful diagnostic tool for HIV retinopathy and presumed neuropathy.

Adult↗

PubMed1997

Visual function abnormalities and prognosis in eyes with age-related geographic atrophy of the macula and good visual acuity.

PURPOSE: Geographic atrophy (GA) may cause significant compromise of visual function, even when there still is good visual acuity (VA), because of parafoveal scotomas and foveal function abnormalities antedating visible atrophy. This study evaluates the visual function abnormalities at baseline and the 2-year worsening of VA and reading rate for eyes with GA compared with a group of eyes with drusen only. METHODS: Seventy-four eyes with GA and VA greater than or equal to 20/50 from a prospective natural history study of GA were included, as were 13 eyes with only drusen. Baseline visual function testing and 2-year VA and maximum reading rate are reported. RESULTS: The worsening of VA in decreased luminance and foveal dark-adapted sensitivity showed severe abnormalities for the GA group. Contrast sensitivity was significantly reduced for the eyes with GA. Half the eyes with GA, but none of the drusen eyes, had maximum reading rates below 100 words per minute. A scanning laser ophthalmoscope (SLO) measure of the scotoma near fixation combined with a measure of residual foveal function accounted for 54% of the variability in maximum reading rate in the eyes with GA. Of 40 eyes with GA observed for 2 years, half lost greater than or equal to 3 lines of VA and one quarter lost greater than or equal to 6 lines. The nine eyes with drusen with follow-up had no significant change in VA. Low foveal dark-adapted sensitivity, SLO measures of the scotoma within 1 degree of fixation, and low maximum reading rate were statistically significant risk factors for doubling of the visual angle. Significant reduction in maximum reading rates at 2 years was present for the eyes with GA. CONCLUSIONS: The eyes with GA with good VA have profound decreases in visual function, particularly in dim lighting and in reading. Half the eyes with GA had doubling in visual angle at 2 years after the baseline examination, whereas the drusen eyes remained essentially unchanged. Impaired visual function at baseline was predictive of an adverse outcome for the eyes with GA.

Aged↗

PubMed1996

Morning-to-evening change in refraction, corneal curvature, and visual acuity 11 years after radial keratotomy in the prospective evaluation of radial keratotomy study. The PERK Study Group.

PURPOSE: Previous reports demonstrate morning-to-evening changes in ophthalmic measurements at 3 months, 1 year, and 4 years after radial keratotomy. The authors determine whether diurnal change in refractive error persists 11 years after radial keratotomy surgery in the Prospective Evaluation of Radial Keratotomy (PERK) study. METHODS: Seventy-one patients were examined in the morning and evening a mean of 11.1 +/- 0.6 years (range, 10-12.7 years) after undergoing radial keratotomy under a standardized protocol using a diamond blade. RESULTS: Between the morning and evening examinations, the mean change in the spherical equivalent of refraction was a 0.31 +/- 0.58-diopter (D) increase in minus power in first eyes. Thirty-six (51%) eyes had an increase in minus power of the manifest refraction of 0.50 to 1.62 D; 22 (31%) had a change in refractive cylinder power of 0.50 to 1.25 D; 9 (13%) had a decrease in uncorrected visual acuity of two to seven Snellen lines; and 25 (35%) showed central corneal steepening measured by keratometry of 0.50 to 1.94 D. Two (3%) eyes lost two lines of spectacle-corrected visual acuity, whereas one (1%) eye gained two lines. In patients whose both eyes underwent surgery, a high degree of symmetry was observed in morning-to-evening refractive change. CONCLUSION: In some patients after radial keratotomy, morning-to-evening change of refraction and visual acuity persists for at least 11 years, although in most patients the magnitude of this change is small. Thus, diurnal fluctuation may be a permanent sequela of radial keratotomy in some individuals.

Circadian Rhythm↗

PubMed2000

Visual acuity disturbances in chronic renal failure.

Patients affected by chronic renal failure often complain of blurred vision when submitted to hemodialysis. Refraction, visual acuity and lens transparency have been evaluated in 36 eyes of 18 patients who underwent hemodialysis, before and after the treatment. Student's t test did not prove any statistically significant difference between the considered parameters. However, a change in refraction was noted in 64% of the eyes, always in hyperopic mean. Corrective glasses had to be changed to ensure the same visual acuity as before the hemodialytic treatment. Particular care must be taken in lens prescription in those patients who could undergo dialysis for chronic renal failure.

Contrast Sensitivity↗

PubMed2006

Improved contrast sensitivity and visual acuity after wavefront-guided laser in situ keratomileusis: in-depth statistical analysis.

PURPOSE: To evaluate changes in contrast sensitivity and visual acuity following wavefront-guided laser in situ keratomileusis (LASIK) procedures with the Visx CustomVue system. SETTING: Six clinical sites that participated in an Investigational Device Exemption clinical study. METHODS: Two hundred seventy-four myopic astigmatic eyes (spherical equivalent range -0.63 to -6.00 diopters) completed 6 months of follow-up examinations. Wavefront-guided procedures using the WaveScan aberrometer and Star S4 excimer laser system with variable spot scanning were performed at 6 clinical locations. Visual acuity and contrast sensitivity under photopic, mesopic, and mesopic-with-glare lighting conditions were tested preoperatively and over a 6-month follow-up period. This study was a retrospective analysis of contrast sensitivity data with controls for the effects of retinal magnification, mesopic pupil size, and the influence of prior soft contact lens wear on visual outcome. RESULTS: Patients experienced statistically significant improvements in contrast sensitivity at all spatial frequencies and under all lighting conditions (P<.05, Student t test). Contrast sensitivity under mesopic conditions with glare improved in 40% of patients. There was more improvement at higher (12 cycles per degree [cpd], 18 cpd) than lower (3 cpd) spatial frequencies. No correlation was found between mesopic pupil size and contrast sensitivity. Results stratified by spectacle or soft contact lens wear were similar. Soft contact lens wearers had slightly higher disability glare scores than spectacle wearers. CONCLUSIONS: A significant number of patients experienced improved corneal optical quality after wavefront-guided LASIK. The contrast sensitivity in most patients was unchanged. Contrast sensitivity improved in a significant number of patients. There was no correlation between mesopic pupil size and mesopic or mesopic-with-glare contrast performance. Spectacle wearers improved more than soft contact lens wearers.

Adult↗

PubMed1995

Fixation disparity and near visual acuity.

Twenty patients having associated heterophoria values of 2 delta and greater, as recorded with a Mallett unit, had their near monocular and binocular visual acuities measured. In the latter case, measurements were taken both with the associated heterophoria corrected by prisms and without prism correction. Bradford Near Vision charts, specially designed to measure visual acuity at near in seconds of arc, were used in the acuity measurement. The improvement of binocular acuity compared with monocular acuity was less than would occur in normal subjects without associated heterophorias. When the associated heterophorias were corrected with prisms the improvement in binocular over monocular acuity was similar to that found in normal subjects, with zero associated heterophoria readings.

Adolescent↗