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PubMed1977

Astigmatism among institutionalized and noninstitutionalized mentally retarded.

Astigmatism was measured retinoscopically for 709 subjects residing in an institution for the mentally retarded and for 56 noninstitutionalized mentally retarded subjects at a community training center. About 60% of the subjects were between 15 and 45 years old. Compared to an intellectually normal sample of young men, astigmatism in the mentally retarded was greater in frequency and degree. For subjects with greater degrees of mental retardation, the prevalence of high astigmastism was significantly greater for whites than for nonwhites. There was no difference in astigmatism between institutionalized retardates and those living in a community setting, a finding that implies that the institutional environment was not the cause of the astigmatic differences between retarded and normal subjects.

Adolescent↗
PubMed1980

The effect of cognitive demand on accommodation.

An optometer (infared recording retinoscope) was used to monitor the accommodation of subjects (N = 40, ages 20 to 30 years) to determine whether an increase in cognitive demand would result in an increase in the level of their accommodation. When the subjects in the experimental group (N = 20) changed from reading 2-digit numbers at 40 cm to adding the numbers, with no change in the visual stimulus, the average level of accommodation increased in 75% of the subjects--the mean level of accommodation increased 0.28 D (P < 0.01). Subjects in the control group (N = 20) showed no significant change in accommodation. The increase in accommodation is attributed to an increase in cognitive damand.

Accommodation, Ocular↗
PubMed1990

Screening infant vision with paraxial photorefraction.

Early screening for refractive errors is highly desirable. Techniques for doing this must be usable with noninstructable subjects (infants), noninvasive, and relatively easy to use. Photorefraction has been used to examine infants' refractive status. However, unless cycloplegia is used, the results can be difficult to evaluate, inasmuch as the subject's plane of focus is not known. This paper describes a photorefraction system that is being used for routine screening of young infants, without cycloplegia and without using highly skilled personnel. The major innovation is the systematic presentation of attractive targets at distances that present a range of demands to accommodation. Changes in the fundal reflections, seen in the photographs taken as the infant views the different targets, can be interpreted unequivocally to identify severe myopia and hyperopia, anisometropia, heterotropia, and anisocoria. The results can also be quantified and are compared with retinoscopic refractions.

Clinical Protocols↗
PubMed1990

Visual acuity and contrast sensitivity of the S cone pathway: preliminary measures with letter charts.

Letter charts were used to measure visual acuity and peak contrast sensitivity of the short wavelength sensitive (S cone)-pathway. The accommodative response was monitored retinoscopically. The mean visual acuity (0.92 logMAR) and spatial contrast threshold (8.7%) were comparable to values reported elsewhere, and variability was relatively low. Both S-pathway acuity and contrast sensitivity were selectively reduced in one patient with central serous retinopathy and in another with retinitis pigmentosa. These simple spatial tests offer an additional index of S-pathway integrity which will be useful for detection and evaluation of ocular disease.

Accommodation, Ocular↗
PubMed1994

Comparison of cycloplegic and noncycloplegic retinoscopy in Chinese pre-school children.

Twenty-seven Hong Kong Chinese children, aged 3 to 5 1/2 years, were recruited in this study to evaluate the relation between refractive error as measured retinoscopically before and after cycloplegia using cyclopentolate 1%. The noncycloplegic spherical refractive error of these children ranged from -0.75 to +2.50 D and approximately 98% of the Hong Kong pre-school children have a manifest spherical error within this range. The cycloplegic refractive error can be approximated by multiplying the spherical component of the manifest error by 1.45 and adding +0.39 D to the product, while keeping the astigmatic power and axis unchanged. Cyclopentolate 1% requires more time to produce mydriasis and cycloplegia in eyes with heavily pigmented irides; however, its final effect on refractive error is apparently independent of iris pigmentation and depends on the amount of spherical refractive error present.

Accommodation, Ocular↗
PubMed1999

Afocal magnification does not influence chick eye development.

In defocus-induced ametropia experiments, retinal blur circles are a likely source of information as to the magnitude but not the sign of the defocus. However, magnification (and minification) produced by the lenses may be a cue. In this study, 1-day-old broiler chicks (N = 13) were treated monocularly for 7 days with special goggles containing approximately afocal iseikonic lenses which were designed to produce 10% retinal image magnification. This is a little less than the magnification produced by +10 D defocusing lenses used to produce about 10 D of hyperopia in earlier work. Intraocular dimensions of both eyes were measured by A-scan ultrasonography on the first and last day. Refractive states of both eyes were measured daily with a retinoscope and trial lenses. After the birds were sacrificed, the eyes were enucleated, weighed, and measured with calipers. Before the treatment there was no difference in the refractive state or dimensions of the right and left eyes. After 1 week of goggle wear there was still no significant difference between the eyes in spite of the magnification produced by the goggles. These data suggest that factors other than magnification are responsible for the ability of the eye to respond to the sign of defocus.

Accommodation, Ocular↗
PubMed1989

Eccentric photorefraction: improving the predictive value and yield in detection of refractive errors.

Eccentric photorefraction (EPR) is a simple photographic technique for detecting amblyopiogenic conditions. Previous EPR studies to detect refractive errors (RE) have demonstrated high sensitivity but poor predictive value. We have established new criteria for detecting RE involving quantifying retinoscopic reflex crescent widths, thereby achieving 67% predictive value with 100% sensitivity for detecting RE greater than or equal to +3.5 D in a clinical study of 69 children. Optical analysis of EPR shows that anticrescent width (light crescent-free portion of the pupil) is independent of pupil diameter. Quantifying anticrescent widths in the above clinical trial increased the predictive value to 85%. Schematic eye and human eye EPR studies verify the theoretical prediction that similar ability to detect refractive errors is maintained when the working distance and eccentricity (distance of light source from lens edge) are reduced. These improvements in EPR reduce its cost and improve its yield; both are essential for its introduction as an acceptable community screening tool.

Adolescent↗
PubMed2005

Accuracy of intraoperative retinoscopy in corneal power and axial length estimation using a high plus soft contact lens.

AIM: To assess the accuracy of intraoperative retinoscopy with high plus soft contact lens (CL) in estimating corneal power and the axial length compared with standard keratometry and biometry measurement. METHODS: Intraoperative retinoscopy was performed in 30 eyes prior to the implantation of an intraocular lens (IOL). A +10 D disposable soft contact lens was applied on the cornea to minimize retinoscopic error. Corneal power was derived from refraction using biometric axial length while the axial length was derived using keratometric measurement. Refraction derived corneal powers and axial lengths from 26 eyes within +/-1.00 D of the target postoperative refraction were compared with preoperative standard keratometry and biometry measurements. RESULTS: In the 26 eyes, the mean difference between the corneal powers derived from refraction and keratometry was 0.35 D (S.D.=1.678). The 95% limits of agreement were -3.006 to +3.706. The mean difference between the axial lengths derived from refraction and biometry was 0.15 mm (S.D.=0.721). The 95% limits of agreement were -1.292 to 1.542. CONCLUSION: Intraoperative retinoscopy with a high plus soft contact lens after phacoemulsification is useful but not accurate in estimating corneal power or axial length of the eye. It should be used cautiously in IOL power calculation as a substitute for standard keratometry or biometry machines when either of these is not available or in error.

Aged↗
PubMed1979

Ultrasonic measurements of the eye in the newborn infant.

The right eyes of 28 newborn infants have been examined retinoscopically, and the anterior chamber depth, the lens thickness and the length of the virteous were measured by ultrasound. In 15 of the infants keratometry was performed using the Javal-Schiötz keratometer. The total axial length of the eye was found to be longer the heavier the weight of the baby, whereas the lens thickness showed no correlation to the total axial length or to the weight of the baby. In only 1/3 of the babies was the corneal astigmatism less than 0.5 D. A significant correlation (P less than 0.01) was found between the total axial length of the eye and the length of the corneal radius.

Anterior Chamber↗
PubMed1983

The use of isotropic photorefraction for vision screening in infants.

Isotropic photorefraction is a technique which makes possible the rapid, economic, large scale screening of infants and young children for refractive errors. The relative size of blur circles reflected from the fundus in 3 flash photographs with different camera settings allows the size and direction of refractive errors to be estimated. The method has been validated against retinoscopic measures on a large group of infants. Findings of a high incidence of astigmatism in the first year are confirmed. Detection of hypermetropia in early infancy by this screening procedure may allow preventive treatment for accommodative strabismus.

Astigmatism↗
PubMed1991

Prandial presbyopia: the muffin man.

Transient blurring of near vision can be due to a variety of causes. We report the case of a 35-year-old man with a 10-year history of blurring of near vision that begins 30 to 45 seconds after he starts to eat and that lasts until 10 to 15 minutes after he stops eating. Magnetic resonance imaging and computed tomography of the brain and orbits did not reveal any abnormality, and stimulation of individual cranial nerves did not result in a loss of near vision. Retinoscopic refraction revealed the loss of 1.5 dioptres of accommodative power in each eye one minute after he began to eat. To the best of our knowledge such blurring of vision at near, immediately after initiating a meal, has not been previously reported. The neuroanatomy of the accommodation and of the gustatory pathways are discussed, as they may relate to this patient's visual complaint.

Accommodation, Ocular↗
PubMed2003

Refractive changes induced by form deprivation in the mouse eye.

PURPOSE: Form-deprivation myopia has been induced in many different animal species. Underlying mechanisms are not well understood to date. In the current study the possibility of inducing refractive errors by form deprivation in the mouse (C57 BL/6) was investigated. METHODS: Thirty animals underwent a 13- to 20-day monocular form-deprivation period by suture of the left eyelid before or after natural eye opening. A subsequent survival period was allowed in a group of animals. Retinoscopic refraction was performed at lid reopening and after the subsequent survival period, when applicable. Animals were killed and the eyes enucleated. The axial length of the eyes was measured in histochemically processed horizontal eye sections. A group of 30 age-matched normal control mice was also studied. RESULTS: Deprived eyes showed significant development of myopia compared with the contralateral fellow eye after transitory hypermetropia, regardless of whether they were deprived before or after natural eye opening. The refractive difference between form-deprived and corresponding fellow eyes was significantly correlated with the difference in axial length, which indicates that myopia is mainly axial. The differences exceeded those between eyes of age-matched normal control mice. CONCLUSIONS: Form-deprivation myopia can be induced in the mouse. This model may be useful to investigate underlying mechanisms of myopia in mammals, because of easier handling and availability of genetically manipulated strains.

Animals↗
PubMed1995

Severe hypertension with lone bilateral papilloedema: a variant of malignant hypertension.

Patients with severe hypertension with retinoscopic bilateral papilloedema only are not classically regarded as having malignant hypertension (MHT). We have encountered 23 such patients between 1965-1993, whilst over a similar period we have seen 315 patients who fulfilled the conventional criteria for MHT with bilateral retinal haemorrhages, exudates with or without papilloedema. We hypothesised that patients with "lone" papilloedema and severe hypertension were suffering from a disease which was identical in aetiology and outcome to conventional MHT. There were no significant differences in age, mean blood pressure, proteinuria or renal function at presentation, ethnic composition, smoking status and followup blood pressure control between the papilloedema group and those presenting with conventional MHT. Clinical features at presentation in the papilloedema only group included strokes in 4, visual disturbance in 2, headaches in 3 and heart failure in 1 patient. Many patients however had no complications at presentation. After a mean followup of 59.8 months, of the "lone" papilloedema group, 7 patients (30.4%) were still alive, 1 patient was on renal dialysis therapy, 13 were dead (56.5%) and 2 (8.7%) were lost to followup. The commonest causes of death were stroke in 4 patients, renal failure in 4 and heart disease in 2. This was a similar pattern of mortality to those patients with "conventional" MHT. Lifetable analyses showed a median survival of 35.9 months for the papilloedema group which was significantly worse than the 108.7 months for the conventional MHT group (Lee-Desu statistic 4.04, p = 0.045). We suggest that patients with high blood pressure and lone bilateral papilloedema may comprise a hitherto unrecognised subgroup of patients with MHT. Once intracerebral pathology has been excluded, these patients need to be treated as aggressively as those with MHT.

Adult↗
PubMedDate not supplied

Cycloplegic refraction after echothiophate iodide.

Retinoscopy under cycloplegia using cyclopentolate (Cyclogyl) hydrochloride was performed on 18 patients (36 eyes) with partial or complete accommodative esodeviation, during and after treatment with echothiophate (Phospholine) iodide. Measurements were clinically comparable on both occasions, regardless of concentration of echothiophate, duration of administration, or interval from discontinuance until refraction. It appears to be unnecessary to discontinue echothiophate iodide in order to obtain reliable cycloplegic retinoscopic measurements.

Accommodation, Ocular↗
PubMedDate not supplied

Near retinoscopy in accommodative esotropia.

We tested whether near retinoscopy, a noncycloplegic retinoscopic technique, was applicable to the optic correction of patients with accommodative esodeviations. We performed a study in 17 patients with accommodative esotropia to compare the refractive values obtained by near retinoscopy and by cycloplegia, as measured by two examiners. The interobserver variability was the same for the two techniques for the refractive values of the horizontal and vertical meridia and spherical equivalent. For the astigmatism, there was greater variability for near retinoscopy. The correlation between the two methods was good, but the variability of the differences was high. We recommend that near retinoscopy should be employed only as a noninvasive method for screening refractive errors in children.

Accommodation, Ocular↗
PubMedDate not supplied

Videokeratography, keratometry, and refraction after penetrating keratoplasty.

PURPOSE: To identify the correlation between videokeratography, autorefractometry, autokeratometry, and keratometry measurements and the subjective manifest refraction and spectacle-corrected visual acuity after penetrating keratoplasty. METHODS: We studied 100 eyes from 100 patients that had undergone penetrating keratoplasty. All eyes were examined by videokeratography (EyeSys 2000) (axial, tangential, and refractive power maps), autorefractometry, autokeratometry, and keratometry. Measurements were made at an an average of 19 +/- 9 months after surgery. Postoperative refractive astigmatism, spherical equivalent refraction, and spectacle-corrected visual acuity were studied by regression analysis. RESULTS: Both the total topographic cylinder measured by the refractive power map and topographic cylinder measured by the axial power map showed the strongest correlation with the manifest refractive cylinder (rs = +0.89, P < .001). The axis of astigmatism determined by keratometry and autokeratometry showed the strongest correlation with the subjective manifest refraction axis (rs = +0.87, P < .001). The total topographic cylinder showed the strongest correlation with the spectacle-corrected visual acuity (rs = +0.38, P = .001); however the topographic indices of predicted corneal acuity, corneal acuity, corneal uniformity index, asphericity, and refractive power symmetry did not correlate with spectacle-corrected visual acuity. CONCLUSION: Measurement of astigmatism after penetrating keratoplasty can be made more accurate by using videokeratographic measurements to supplement retinoscopic and manifest refraction. Other useful methods for predicting the axis of refractive astigmatism include keratometry, autokeratometry, and autorefractometry. In this study, indices designed to measure corneal surface irregularity failed to predict visual acuity after penetrating keratoplasty.

Astigmatism↗
PubMedDate not supplied

Slit skiascopic-guided ablation using the Nidek laser.

PURPOSE: To present the approach of using a scanning slit refractometer (the ARK 10000) in conjunction with a corneal topography system to guide customized corneal ablation. This diagnostic system is coupled with the Nidek EC-5000 system which combines scanning slit and a scanning small area ablation (1.0 mm) to perform a customized ablation. METHODS: The ARK 10000 diagnostic system which contains a scanning slit refractometer is described. Information generated from the ARK 10000 wavefront sensor and corneal topography system can be coupled to the new Nidek EC-5000 excimer laser system, which combines the larger area of scanning slit ablation with the small area (1.0 mm) ablation. RESULTS: The Nidek ARK 10000 diagnostic system captures wavefront information using a retinoscopic system which is converted into a refractive power map. This is different from other autorefraction systems in that it has four sensors at different diameters of the cornea and captures 1440 points in 0.4 seconds. This map is used in conjunction with corneal topography-captured simultaneously. This information is then combined to perform a customized ablation using the new Nidek EC-5000 system. CONCLUSIONS: The ARK 10000 diagnostic system represents a different approach to customized ablation in that it combines a corneal topography system with a wavefront system and a larger treatment area of the traditional scanning slit ablation with a new small area ablation treatment for greater efficiency.

Accommodation, Ocular↗