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At least 289 records · Page 16Linked to original sources

PubMed1999

[Clinical application of a new method for the objective estimation of minimum visual acuity].

PURPOSE: Recently, a new method for the objective estimation of the minimum visual acuity (OEM) by means of suppression of the optokinetic nystagmus has been presented (Klin Monatsbl Augenheilkd 1998;212:196-202). This study reports on the clinical use of this method. METHODS: In 120 individuals referred to our clinic either to procure an ophthalmological expert opinion or for differential diagnosis of an unclear visual impairment, an OEM was performed. The result of the OEM was compared to the clinical findings (history, biomicroscopy of anterior and posterior segments, objective refractometry, pupillary responses, binocular alignment, motility, binocular vision, colour vision, applanation tonometry, electrophysiology, fluorescein angiography, neurologic, radiologic, psychiatric findings, reproducibility of visual acuity and visual field statements under different conditions, comparison of subjective and objective visual field data, statistical prove of false visual acuity and visual field statements) which were critically interpreted concerning the credibility of the subject's statements. RESULTS: As a result of the clinical examinations, the stated visual acuity of 62 individuals was credible. In one of these individuals, the OEM pointed to a slightly (1dB) better visual acuity. The statements of 7 individuals could not be categorized clinically. The OEM pointed to a better acuity in 3 cases. The stated vision of the remaining 51 individuals was not credible. In 38 of these cases, the OEM pointed to a better acuity, or false statements could be proven by the OEM. CONCLUSION: A significant rate (75%) of the individuals whose statements were not credible was detected by the computer-aided, nystagmographic method of OEM. The method allows an estimation of the actual minimum visual acuity and yields evidence of false statements concerning the detection acuity.

Biofeedback, Psychology↗

PubMed1995

[Sensitivity of refraction measurement with the infrared videorefractometer VRB 200].

AIM OF THE STUDY: This study investigates the sensitivity of a computerised videorefractor (VRB 200) for refractive errors, especially amblyopiogenic, in babies and infants. PATIENTS AND METHODS: Videopictures from 312 eyes of 156 babies and infants were taken, evaluated and compared with the current measurements (skiaskopy or refractometry) of the university eye hospital Erlangen-Nürnberg. RESULTS: 255 (81.7%) of 312 eyes were evaluable. The VRB 200 achieves a sensitivity of 96.1% in hyperopic eyes (219 of 228 eyes) and 94.7% in myopic eyes respectively (18 of 19 eyes). Of 8 emmetropic eyes 6 were recognized correctly negative. Astigmatism could be estimated coarsely quantitatively in power and qualitativ in the axis with a sensitivity of 80% (92 of 115 eyes) and a specificity of 86% (121 of 140). Anisometropia over 2 dpt was recognized in 5 of 6 patients. A general statement concerning the specificity is not possible with this study, because it is not a mass screening procedure. CONCLUSION: This videorefractor is able to recognize semi-quantitatively ambylopiogenic refractive errors with high sensitivity.

Amblyopia↗

PubMed1994

[How accurate is video refraction measurement in infants in comparison with skiascopy? How much do the values change within a half a year?].

BACKGROUND: Isotropic photorefraction (Atkinson et al., 1981) is a method used to screen the refraction in infants. The aim of this study is to analyze its limitations as a measuring instrument. MATERIALS AND METHODS: 215 children aged between 5 and 12 months were examined in cycloplegia. The results were subsequently compared (1) to the results of streak retinoscopy also performed at the same time and (2) to photorefraction performed a second time, 6 months later (with 145 children). RESULTS: Spherical refraction: The mean spherical values differed by 0.70 dpt through photorefraction methods, compared to retinoscopy. The standard deviation (SD) was 0.67 dpt. The values of the photorefraction differed therefore in 95% of the children within a range of 2.7 dpt (or +/- 2 SD). Compared to the second photorefractive measurement 6 months later, the average refraction showed a small myopic shift (-0.45 dpt). Astigmatism: The errors of measurement were more pronounced here. Extreme differences of up to 9 dpt were found in single cases. The mean difference, compared to retinoscopy, was 0.73 dpt. The standard deviation (SD) was 0.90 dpt. In 95% of the children, the values of photo-refraction differed therefore by a range of 3.6 dpt (or +/- 2 SD). Compared to the second photorefractive measurement 6 months later, the average refraction showed a mean change of 0.73 dpt. CONCLUSIONS: Our photorefractive measurements showed errors in the range of 1-2 dpt for the spherical refraction, and in the range of 2-3 dpt for astigmatism. In 5% of the children examined, even greater aberrations were found. As long as the aim of photorefraction is restricted to disclosing high refractive errors, this method is judged suitable for the refractive screening of infants. For more precise refraction, and for the prescription of spectacles, we believe that is should be supplemented by a second examination technique, such as retinoscopy or automated refractometry.

Astigmatism↗

PubMed1991

[Eliminating reflection of intraocular lenses].

Reflections on the refractive surfaces of intraocular lenses can be a nuisance when performing retinoscopy or refractometry. Some patients with IOLs also see reflections which disturb their vision. This article examines the conditions for coating IOLs. It also explains why conventional coating methods cannot be used for IOLs.

Humans↗

PubMed1980

[Liindner's method of cylinder retinoscopy without theory].

Brief description of Lindner's cylinder retinoscopy for practical application: The main criteria of this accurate method for checking refraction are the direction, shape, speed and brightness of the retinoscopic phenomena moving in the pupil of the examined eye. To determine astigmatism the use of plus cylinders is recommended. Difficulties may be due to the optical aberration at the periphery of a wide pupil, to a scissors phenomenon, and to optical irregularities of the senile lens, corneal opacities etc. In many cases retinoscopy can be performed well without using mydriatics and cycloplegics, respectively. Children must not be overstrained. Generally, final subjective checking is crucial for the prescription of corrective glasses. Mastery of Lindner's cylinder retinoscopy enables the eye specialist to keep refractometry with simple aids, as an essential part of the ophthalmological diagnosis, in his own hands, against the increasing claim of optometrists and opticians.

Adult↗

PubMed2004

Domains formed within the N-terminal region of the quorum-sensing activator TraR are required for transcriptional activation and direct interaction with RpoA from agrobacterium.

TraR, a quorum-sensing activator, induces transcription from its binding site, the tra-box, located upstream of Ti plasmid target promoters. TraR activated expression of a lacZ reporter in Escherichia coli only when RpoAAt from Agrobacterium tumefaciens was co-expressed. As assessed by gel retardation assays RpoAAt, but not RpoAEc, formed a ternary complex with TraR and a tra-box probe in vitro. TraR formed similar ternary complexes with alphaCTDAt but not with NTDAt, the C- and N-terminal segments of RpoAAt. As measured by surface plasmon resonance refractometry, TraR interacted directly with RpoAAt with an affinity about five times greater than that observed for its interaction with RpoAEc. The activator interacted with alphaCTDAt with kinetics and affinities similar to those of the full-sized -subunit. Positive control (PC) mutations at Asp-10 and Gly-123 of TraR did not affect DNA binding but greatly decreased the TraR-RpoAAt interaction. These two residues combine to form two patches on the activator, one of which may be involved in interaction with RpoA. When co-expressed, mutants of TraR with substitutions at Asp-10 complementing mutants with substitutions at Gly-123 for gene activation in an allele-specific manner. Co-expression studies with TraR and its PC mutants, and also with complementary PC alleles of TraR, coupled with three-dimensional structure are consistent with a hypothesis that both Asp-10/Gly-123 patches are required for activator function.

Agrobacterium tumefaciens↗

PubMed1997

Compensation for spectacle lenses involves changes in proteoglycan synthesis in both the sclera and choroid.

PURPOSE: It has been demonstrated that chick eye growth compensates for defocus imposed by spectacle lenses: the eye elongates in response to hyperopic defocus imposed by negative lenses and slows its elongation in response to myopic defocus imposed by positive lenses. We ask whether the synthesis of scleral extracellular matrix, specifically glycosaminoglycans, changes in parallel with the changes in ocular elongation. In addition, there is a choroidal component to compensation for spectacle lenses; the choroid thickens in response to myopic defocus and thins in response to hyperopic defocus. We ask whether choroidal glycosaminoglycan synthesis changes in parallel with changes in choroidal thickness. METHODS: Chicks wore either a +15 diopter (D) or -15 D spectacle lens over one eye, or they wore one lens of each power over each eye for 5 days. At the end of this period, we measured refractive errors and ocular dimensions by refractometry and A-scan ultrasonography, respectively. Pieces of the scleras and choroids from these eyes were put into culture and the synthesis of glycosaminoglycans was assessed by measuring the incorporation of radioactive inorganic sulfur. RESULTS: We here report that the compensatory modulation of the length of the eye involves changes in the synthesis of glycosaminoglycans in the sclera, with synthesis increasing in eyes wearing -15 D spectacles lenses and decreasing in eyes wearing +15 D lenses. In addition, changes in the synthesis of glycosaminoglycans in the choroid are correlated with changes in choroidal thickness: eyes wearing +15 D lenses develop thicker choroids and these choroids synthesize more glycosaminoglycans than choroids from eyes wearing -15 D lenses. CONCLUSIONS: Changes in scleral glycosaminoglycan synthesis accompany lens-induced changes in the length of the eye. Furthermore, changes in the thickness of the choroid are also associated with changes in the synthesis of glycosaminoglycans. These results are consistent with the regulation of the growth of the eye being bidirectional, and with the retina being able to sense the sign of defocus.

Adaptation, Physiological↗

PubMed2003

Variability of retinal steepness at the posterior pole in children 7-15 years of age.

PURPOSE: Considerable evidence suggests that both axial and peripheral refraction play important roles in eye growth control. The large variability in peripheral refraction seen in adults and children indicates that the peripheral retina is exposed to a wide range of refractive errors. The current lack of appropriate measurement techniques has hampered the determination of whether variability in peripheral refraction between individuals can be correlated with variability in retinal steepness. An Optical Low Coherence Reflectometer (OLCR) was developed to determine retinal steepness. METHODS: Retinal steepness was assessed in right eyes of 63 children 7-15 years of age by measuring eye length (EL) and spherical equivalent refraction (SER) axially and at 15 degrees temporally, nasally, inferiorly and superiorly with OLCR and Binocular Auto-Refractometry, respectively, during cycloplegia. At each peripheral location, relative peripheral EL and SER (i.e., the difference between peripheral and axial readings) were compared between myopic, emmetropic and hyperopic eyes, and the correlation between relative peripheral EL and SER was analyzed. RESULTS: Although the standard deviations were large, significant differences in relative peripheral EL and SER between refractive groups as well as a significant correlation between relative peripheral EL and SER were observed at several of the assessed locations. CONCLUSIONS. The results strongly suggest that peripheral refraction is correlated with retinal steepness and that previously observed variability in peripheral refraction chiefly reflects variability in retinal steepness. If peripheral refraction represents a determining parameter in the control of eye growth, the precise measurement of retinal steepness could be used not only to improve estimates of myopic progression, but also to identify children who are at high risk of developing myopia. It may lead to specialized clinical/optical treatments, e.g. the correction of not only axial but also peripheral refractive errors, which are more effective than current treatments in individuals who are at risk of myopia development or progression.

Adolescent↗

PubMed2006

Local patterns of image degradation differentially affect refraction and eye shape in chick.

PURPOSE: To evaluate visual blur as a mechanism for modulating eye shape. METHODS: Chicks wore a unilateral full goggle or one of several goggles modified with apertures. After 2 weeks, eyes were measured with refractometry, ultrasound, and calipers, and three retinal regions were assayed for dopamine and DOPAC (3,4-dihydroxyphenylacetic acid). RESULTS: Goggled eyes were diffusely enlarged or enlarged predominantly along the axial dimension, depending on the goggle. Myopia developed under goggle types inducing primarily axial growth and under some of the goggles inducing diffuse eye expansion. Enlarged eyes remained emmetropic beneath other goggles that caused diffuse eye expansion. Reductions in retinal dopamine and DOPAC were proportional to the eye growth and refraction effects. CONCLUSIONS: Localized image degradation can cause myopia with predominantly axial expansion, myopia with more diffuse vitreous chamber expansion, or eye expansion without myopia. Robust expansion of the equatorial diameter alone was not observed. The associated alterations in retinal dopamine metabolism are consistent with a hypothesized role of dopaminergic amacrine cells in the visual regulation of eye growth. Besides refraction and overall size, visual blur can affect eye shape; but the goggle responses do not correspond to a simple summation of blur signals across the retina. Therefore, other mechanisms seemingly are needed to account for the full range of refractions and ocular shapes seen in chicks and, by analogy, in humans.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2006

Anterior segment growth and peripheral neural pathways in chick.

PURPOSE: To learn if peripheral nerve pathways are necessary for corneal expansion and anterior segment growth under a 12-hr light:dark cycle or for the inhibition of corneal expansion under constant light rearing. METHODS: Recently hatched White Leghorn chicks under anesthesia received unilateral ciliary ganglionectomy (CGx), cranial cervical ganglionectomy (Sx), or section of the ophthalmic nerve (TGx), along with sham-operated and/or never-operated control cohorts. Chicks were reared postoperatively under either a 12-hr light:dark cycle or under constant light. After 2 weeks and with the chicks under anesthesia, corneal radii of curvature and diameters were obtained with a photokeratoscope, refractometry and A-scan ultrasonography were performed, and the axial and equatorial dimensions of enucleated eyes were measured with digital calipers. Corneal areas were calculated from corneal curvatures and diameters. RESULTS: Despite the rich peripheral innervation to the eye, the selective denervations performed here exerted remarkably limited effects on corneal expansion and anterior segment development in chicks reared under either lighting condition. Ophthalmic nerve section did reverse in large part the inhibition of equatorial expansion of the vitreous chamber occurring under constant light rearing. CONCLUSIONS: The ciliary, sympathetic, or ophthalmic peripheral nerve pathways to the eye are not required either for corneal expansion and anterior segment development under a 12-hr light:dark cycle or for the inhibition of corneal expansion under constant light rearing. The ocular sensory innervation may be a means for regulating vitreous cavity shape.

Animals↗

PubMed2005

Floral nectar production and nectary anatomy and ultrastructure of Echinacea purpurea (Asteraceae).

BACKGROUND AND AIMS: In spite of the impressive species diversity in the Asteraceae and their widespread appeal to many generalist pollinators, floral-nectary ultrastructure in the family has rarely been investigated. To redress this, a study using Echinacea purpurea, a plant of horticultural and nutraceutical value, was undertaken. Nectar secretion of disc florets was compared with floral nectary ultrastructure taking into account nectar's potential impact upon the reproductive success of this outcrossing species. METHODS: Micropipette collections of nectar in conjunction with refractometry were used to determine the volume and nectar-sugar quantities of disc florets throughout their phenology, from commencement of its production to cessation of secretion. Light, scanning-electron and transmission-electron microscopy were utilized to examine morphology, anatomy and ultrastructure of nectaries of the disc florets. KEY RESULTS: Florets were protandrous with nectar being secreted from anthesis until the third day of the pistillate phase. Nectar production per floret peaked on the first day of stigma receptivity, making the two innermost whorls of open florets most attractive to foraging visitors. Modified stomata were situated along the apical rim of the collar-like nectary, which surrounds the style base and sits on top of the inferior ovary. The floral nectary was supplied by phloem only, and both sieve elements and companion cells were found adjacent to the epidermis; the latter participated in the origin of some of the precursor cells that yielded these specialized cells of phloem. Companion cells possessed wall ingrowths (transfer cells). Lobed nuclei were a key feature of secretory parenchyma cells. CONCLUSIONS: The abundance of mitochondria suggests an eccrine mechanism of secretion, although dictyosomal vesicles may contribute to a granulocrine process. Phloem sap evidently is the main contributor of nectar carbohydrates. From the sieve elements and companion cells, an apoplastic route via intercellular spaces and cell walls, leading to the pores of modified stomata, is available. A symplastic pathway, via plasmodesmata connecting sieve elements to companion, parenchyma and epidermal cells, is also feasible. Uncollected nectar was reabsorbed, and the direct innervation of the nectary by sieve tubes potentially serves a second important route for nectar-sugar reclamation. Microchannels in the outer cuticle may facilitate both secretion and reabsorption.

Carbohydrates↗

PubMed2002

Changes of posterior corneal astigmatism and tilt after myopic laser in situ keratomileusis.

PURPOSE: The purpose of this study was to assess the changes of posterior corneal astigmatism and tilt after laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness. METHODS: This prospective nonrandomized (self-controlled) comparative trial included 57 eyes from 14 females and 15 males, whose mean age (+/- standard deviation [SD]) at the time of surgery was 33 +/- 9 years (range, 19-53), with a spherical equivalent (SEQ) of -1.00 to -15.50 (mean, -5.07 +/- 2.81) diopters (D). All LASIK procedures were accomplished with the Keratom II Coherent-Schwind excimer laser and the Moria Model One microkeratome (150-microm head). Subjective refractometry, Orbscan slit-scanning corneal topography analysis, and pachymetry were performed before and 3 months after LASIK for myopia (n= 35; -1.00 to -15.50 D [mean, -4.75 +/- 3.07]) or myopic astigmatism (n= 22; sphere, 0.00 to -9.75 D [mean, -4.75 +/- 2.36]; cylinder, -0.75 to -3.50 D [-1.68 +/- 0.86]). Intended ablation depth ranged from 12 to 108 (mean, 48 +/- 22) microm. Topographic raw data were decomposed into a set of Zernike polynomials as published in detail previously, and parameters for detection of asymmetric mechanical deformation of the cornea were derived. Posterior corneal astigmatism and tilt before and after LASIK were compared, and changes in these variables were correlated with the SEQ change (DeltaSEQ) and the residual corneal bed thickness (RBT). RESULTS: The RBT after LASIK ranged from 186 to 373 (mean, 280 +/- 42) microm. Overall, astigmatism (0.19 +/- 0.07 D/0.22 +/- 0.13 D; p= 0.80) and tilt (3.58 +/- 0.35 degrees /3.65 +/- 0.48 degrees; p= 0.61) did not change significantly by 3 months after LASIK. In eyes with RBT < or =250 microm, the average change in astigmatism (0.05 +/- 0.11 versus 0.01 +/- 0.13 D; p= 0.46) and tilt (0.21 +/- 0.45 degrees versus 0.04 +/- 0.55 degrees; p= 0.30) was not greater than in eyes with RBT > 250 microm. Change in astigmatism (p= 0.19) and tilt (p= 0.56) did not correlate with the RBT during LASIK. CONCLUSIONS: Zernike decomposition of topographic height data discloses that no significant asymmetric mechanical deformation of the posterior corneal curvature occurs after myopic LASIK. Further studies with long-term follow-up are needed to clarify whether this symmetry of the posterior corneal surface can indeed be preserved over time after LASIK if the RBT is < 250 microm.

Adult↗

PubMed2004

Oculometric characteristics of extreme hypermetropia in two faroese families.

PURPOSE: To describe and analyze the oculometric features of small eyes with high hypermetropia in two Faroese families, with emphasis on refractive components. METHODS: Members of the two families (N=40; age, 1 to 77 years), including 15 cases of extreme hypermetropia (+7.5 to +19.25 D), had an ophthalmic evaluation including refractometry, keratometry, and axial ocular measurements using A-scan ultrasound. Eye-wall thickness was assessed using B-scan. Nonparametric statistics were used, mainly the Mann-Whitney U test. RESULTS: In the two families, there were six and nine probands, respectively, with hypermetropia more than +7 D and short eyes as defined by axial eye lengths <21 mm. The median corrected visual acuity was 0.4 (range, 0.2 to 0.9). Gross fundus abnormalities were not observed. All 15 had a short posterior segment with a thick eye wall and a relatively thick lens. Furthermore, steep and rather small corneas were present. In one of the families, 70% of the affected had a corneal curvature radius of < or =7.0 mm. Five probands from family 2 were labeled as possibly affected because of hypermetropia and borderline axial length findings (21 to 22 mm). The remaining 20 subjects had visual acuity and oculometric findings within physiologic limits. CONCLUSIONS: The axial measurement features in our series of highly hypermetropic eyes mainly presented as an extension downward from the hypermetropic bottom line of the normal distribution. The axial shortness of the eyes was primarily the result of a short posterior eye segment ("posterior microphthalmos"). A steep cornea was a feature in most small eyes in our series, particularly in one family branch.

Adolescent↗

PubMed1989

A simple field test for assessing salt balance in heat-stressed miners.

A simple colorimetric test for urinary chloride (Fantus test) corrected for urine specific gravity (measured by refractometry) enabled 24-hour urinary sodium excretion rates to be predicted accurately from a single spot sample of urine. In 29 acclimatized miners working in an environment in excess of 40 degrees C, salt-conserving mechanisms, involving renin and aldosterone, were not active until the urinary sodium excretion rate fell below 50 mmol/24 h. A predicted sodium excretion rate greater than 50 mmol/24 h indicates that dietary sodium supplementation is not necessary.

Adult↗

PubMed2000

Laser-hole boring into overdense plasmas measured with soft X-Ray laser probing

A laser self-focused channel formation into overdense plasmas was observed using a soft x-ray laser probe system with a grid image refractometry (GIR) technique. 1.053 &mgr;m laser light with a 100 ps pulse duration was focused onto a preformed plasma at an intensity of 2x10(17) W/cm (2). Cross sections of the channel were obtained which show a 30 &mgr;m diameter in overdense plasmas. The channel width in the overdense region was kept narrow as a result of self-focusing. Conically diverging density ridges were also observed along the channel, indicating a Mach cone created by a shock wave due to the supersonic propagation of the channel front.

Journal Article↗

PubMed2004

Consideration of the posterior corneal curvature for assessment of corneal power after myopic LASIK.

PURPOSE: To evaluate the effect of a separate measurement of the anterior and posterior corneal surface to calculate the total refractive power of the cornea after myopic laser in situ keratomileusis (LASIK). METHODS: A total of 39 eyes of 21 patients (aged 33 +/- 9 years) were included in this prospective, non-randomized, comparative study. These involved 19 myopic corrections (- 3.5 +/- 1.6 dioptres) and 23 refractive corrections of myopic astigmatism (sphere: - 3.7 +/- 1.6 D, cylinder: - 1.2 +/- 0.4 D). All procedures were accomplished with the Keratom II). Coherent-Schwind excimer laser and the Moria Model One) microkeratome (150 micro m head) at the Medical Education Centre, La Trinidad, Caracas, Venezuela. Subjective refractometry, Bausch & Lomb) keratometry and Orbscan) slit-scanning corneal topography analysis were performed before and 3 months after LASIK. Corneal power was assessed directly using keratometry (K1) and Orbscan videokeratography (T1). Corneal power was calculated using the preoperative keratometric (K2, 'gold standard', clinical history method) or topographic power (T2, clinical history method) and spherical equivalent change. A composite value was derived from the Orbscan anterior and posterior surface power and central pachymetry (T3). RESULTS: Three months postoperatively, corneal power ranged in a descending order from T1 (42.33 +/- 1.78 D), K1 (40.82 +/- 2.20 D), K2 (40.42 +/- 2.36 D), T2 (40.03 +/- 2.51 D) to T3 (38.78 +/- 2.23 D). On average, T1 exceeded the gold standard by 1.9 D and the gold standard exceeded T3 by 1.6 D. K2, T1, T2 and T3 correlated significantly with K1 (r = 0.975, p < 0.001; r = 0.909, p < 0.001; r = 0.963, p < 0.001; r = 0.853, p < 0.001, respectively). The differences T1-K2 (r = - 0.699, p < 0.001) and T3-K2 (r = - 0.499, p = 0.001) correlated highly inversely and K1-K2 correlated borderline inversely (r = - 0.325, p = 0.043) with the intended refractive correction. CONCLUSION: After myopic LASIK, refractive corneal power is overestimated by direct keratometric and especially videokeratoscopic measurements. The higher the intended refractive correction, the greater is this error. A separate measurement of both refractive surfaces of the cornea tends to underestimate but may enhance accuracy of the total refractive corneal power if the history of the patient is unknown.

Adult↗

PubMed2004

The influence of age, sex, race, refractive error and optic disc parameters on the sensitivity and specificity of scanning laser polarimetry.

PURPOSE: To evaluate the influence of age, sex, race, refractive error and optic disc topography on the sensitivity and specificity of scanning laser polarimetry (SLP) in the diagnosis of glaucoma. METHODS: A total of 88 normal individuals and 95 glaucoma patients were included in this study. Glaucoma was defined on the basis of both optic nerve damage and visual field defects. Scanning laser polarimetry, optic disc topography, automated perimetry and refractometry were performed in all subjects. The sensitivity and specificity of SLP were assessed applying a previously calculated cut-off to a previously described linear discriminant function (LDF). RESULTS: The sensitivity and specificity of SLP in the study population were 82% and 83%, respectively. Sensitivity and specificity were not affected by age, sex, race, average disc diameter or disc area. The sensitivity of SLP tended to be higher in myopes (93%) than in emmetropes (80%) and hyperopes (71%) (p = 0.08). Sensitivities were higher in individuals with cup areas > 0.96 mm(2) (89%), rim areas < or = 1.36 mm(2) (92%), and cup area/disc area ratios > 0.45 (89%) (p < 0.05). Stepwise logistic regression analysis indicated that the presence of a cup area > 0.96 mm(2) and a rim area < 1.36 mm(2) significantly increased the sensitivity of the LDF, whereas a cup area/disc area ratio < or = 0.45 significantly increased the specificity of the LDF. CONCLUSION: The sensitivity and specificity of SLP may be influenced by refractive error and optic disc parameters that are affected by glaucomatous damage (cup area, rim area and cup area/disc area ratio). These parameters must be considered in studies evaluating the sensitivity and specificity of optic nerve/retinal nerve fibre layer imaging technologies.

Age Factors↗

PubMed1993

On the Stiles-Crawford effect and ocular imagery.

To study the modifying effect on spherical aberration of the retinal directional sensitivity (the Stiles-Crawford effect), ocular imagery was simulated by computer ray-tracing in a phakic and a pseudophakic model eye. The Stiles-Crawford effect was found to reduce the distance between the paraxial focus and the effective least blur focus. The modifying effect on spherical aberration was found to be insignificant for pupil sizes below 4 mm, and to increase in magnitude above this size. For an 8 mm pupil, the effective focus was found to move 0.3 mm and 0.2 mm toward the paraxial focus for the phakic and the pseudophakic eye, respectively. This corresponded to a shift of 1.0 D and 0.6 D in the spectacle plane, respectively. The modifying effect of the retinal directional sensitivity should be taken into account in the theory of ocular refraction and in objective keratometry and refractometry.

Cataract↗