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PubMed1994

Inhibition of aceclidine-stimulated outflow facility, accommodation and miosis in rhesus monkeys by muscarinic receptor subtype antagonists.

Aceclidine can dissociate accommodative and outflow facility responses in monkeys and humans. We sought to determine if different muscarinic receptor subtypes control outflow facility, accommodative and pupillary responses to aceclidine in the living rhesus monkey eye, as a possible basis for this separation. Each eye was cannulated with one branched and one unbranched needle. Baseline measurements (of outflow facility by two-level constant pressure perfusion; refraction by Hartinger coincidence refractometry and pupil diameter by vernier calipers) were recorded after anterior chamber exchange with (one eye) or without (opposite eye), muscarinic receptor subtype antagonist (pirenzepine, AF-DX 116 or 4-DAMP). The eyes were then exchanged a second time with these solutions plus added aceclidine. The response to aceclidine (the differences from baseline) in the presence or absence of antagonist were compared. The M3 muscarinic receptor subtype antagonist 4-DAMP was the most potent inhibitor of all three responses to aceclidine. The dissociation of accommodative, outflow facility and miotic responses to aceclidine in rhesus monkeys does not appear to be due to differences in the muscarinic receptor subtypes that can currently be distinguished pharmacologically.

Accommodation, Ocular↗

PubMed1984

A-band mass exceeds mass of its filament components by 30-45%.

We have measured filament lattice spacing in fibrils using X-ray diffraction, and find that STEM-determined mass/length values reported for myofilaments should give 13% w/v as the filament protein concentration in the lattice of the AO-band (filament overlap zone) of both insect flight muscle (IFM) and vertebrate skeletal muscle ( VSkM ). This is well below the actual mass concentration of AO-bands as measured by immersion refractometry of detergent-washed rigor myofibrils under the phase microscope. This technique identifies an immersion fluid of suitable refractive index (RI) for matching out all image contrast between background and the selected cross-band. We used RI fluids in which the effective RI matching component is a large-particle solute (Percoll or hemocyanin) excluded by the filament lattice. The measured RI indicates that protein concentration in AO-bands is 16-17% in Lethocerus and other IFM fibrils including CAF-digested fibrils, and is 18-19% in rabbit VSkM fibrils. On IFM fibrils we also measured absolute buoyant density in Percoll as greater than or equal to 1.042; this supports the value for mass concentration as determined by RI. The mass discrepancy between fibrils and filaments does not seem to arise from faults in the methods used. We therefore accept the STEM-determined mass/length values for thick filaments which indicate 4 myosins/crown in IFM and 3 in VSkM , and we believe there is considerable extra nonfilament material (concentration: 30-50 mg/ml) between the filaments in fibrils. In stretched VSkM , it is the H-bands, not the I-bands, which have an excess over filament mass content. The extra mass has not been identified.

Animals↗

PubMed1979

Lamellar keratoplasty in keratoconus.

The authors present the results of 11 keratoplasties in cases of keratoconus, comparing the visual acuity and the ocular refraction before and after the operation (ophtalmometry, objective and subjective refractometry). The statistical data indicate a meaningful flattening of the corneal curvature (12.84 dpt average) and a mean reduction of the myopia for 8.227 dpt. In fact, the basic regular astigmatism of the cornea had not been altered. The mean visual acuity was 0.68 (with an improvement of 0.495). No further damage of acuity had been observed. After 10 to 69 months a medical checkup revealed transparent grafts in five cases; four presented small maculae; one, thin folds of Descemet's membrane. Based on the authors' experience and on the literature, the paper recommends lamellar keratoplasty in cases of keratoconus, the surgeon must choose the appropriate moment in the course of the development of this disease.

Adult↗

PubMed1985

High performance liquid chromatographic separation of diacylglycerol acetates to quantitate disaturated species of lung phosphatidylcholine.

A high-performance liquid chromatographic (HPLC) separation of diacylglycerol acetates to quantitate disaturated species of lung phosphatidylcholine (PC) was studied. The diacylglycerol acetates were applied on a reversed phase column, eluted by an isocratic solvent, acetonitrile/isopropanol/water (35:15:1, v/v/v) at a flow rate of 1 ml/min, and detected by differential refractometry (RI). This isocratic HPLC method was useful to separate disaturated species from the others of lung PC. The quantitative analysis of the molecular species separated by HPLC was studied by RI detection. Chromatograms obtained by RI detection and radioactivity determination of diacylglycerol [3H]acetates prepared by [3H]acetic anhydride were almost identical. The RI detector responded in the same degree for different authentic standards of diacylglycerol acetates. The detection limit with RI detection was about 30 nmoles. Molecular species of PCs from human lung and carcinoma tissues were analyzed by this HPLC method. The contents of disaturated species were very similar to those reported previously. These results indicate that RI detection is very useful in the nmole range for the quantitative analysis among the molecular species containing disaturated species.

Acetates↗

PubMed2005

Optimizing integrated optical chips for label-free (bio-)chemical sensing.

Label-free sensing is an important method for many (bio-)chemical applications in fields such as biotechnology, medicine, pharma, ecology and food quality control. The broad range of applications includes liquid refractive index sensing, molecule detection, and the detection of particles or cells. Integrated optics based on the use of waveguide modes offers a great potential and flexibility to tailor the sensor properties to these applications. In this paper, the results of a numerical study are presented, showing that this flexibility is founded on the many degrees of freedom that can be used for the integrated optical chip design, in contrast to other technologies such as those based on surface plasmon resonance, for which the materials' properties limit the range of choices. The applications that are explicitly considered and discussed include (1) bulk refractometry, (2) thin-layer sensing, for example biosensors monitoring molecular adsorption processes occurring within some 10 nm of the chip's surface, (3) thick-layer sensing with processes involving molecules or ions to be monitored within a sensing matrix extending to some 100 nm from the chip's surface, for example hydrogel-based layers and chemo-optically sensitive membranes, and (4) particle sensing with particles or, for example, biological cells to be monitored within probe volumes extending to some 1,000 nm from the chip's surface. The peculiarities for the different types of applications will be discussed, and suitable modeling methods presented. Finally, the application-specific design guidelines supplied will enable the optimization of various types of integrated optical sensors, including interferometers and grating-based sensors.

Biosensing Techniques↗

PubMed2005

Changes of the accommodative amplitude and the anterior chamber depth after implantation of an accommodative intraocular lens.

BACKGROUND: Modern cataract surgery is interested in recovery of the accommodative power. This investigation aimed at determining pseudophakic accommodation in subjects implanted with the accommodative Human Optics 1 CU intraocular lens after drug-induced ciliary muscle stimulation by measuring the objective refraction and the changes in anterior chamber depth in comparison with a PMMA intraocular lens with rigid haptics. METHODS: The studied sample involved 30 eyes of 30 patients undergoing cataract surgery due to age-related cataract. Patients were between 50 and 77 years of age (67.71 +/- 8.0). No randomization was performed. The 1 CU accommodative intraocular lens and the PMMA intraocular lens were implanted in 15 eyes of patients with an expected visual acuity of at least 0.7. Objective refraction under pilocarpine-stimulated ciliary muscle contraction was determined with a Hartinger coincidence refractometer. The anterior chamber depth was measured with Jäger's Haag-Streit slit-lamp attachment. The accommodative amplitude and the anterior chamber flattening were calculated from the measured values. RESULTS: Twelve weeks after surgery the average accommodative amplitude in eyes with a 1 CU intraocular lens calculated from the refractive change under drug-induced stimulation was 0.48 +/- 0.36 D (with a maximum of 1.25 D). The measured change of anterior chamber depth under drug-induced stimulation was 0.3 +/- 0.32 mm (at a maximum of 0.9 mm). In the reference group with PMMA lenses, the mean accommodative amplitude derived from the refractive changes under drug-induced stimulation was 0.34 +/- 0.27 D (at a maximum of 0.85 D). The measured change in anterior chamber depth under drug-induced stimulation was 0.18 +/- 0.09 mm (at a maximum of 0.31 mm). No statistically significant differences were found between the two groups of lenses concerning change in anterior chamber depth and accommodative amplitude. CONCLUSIONS: This investigations indicate a mean anterior 1 CU shift of only 0.32 mm and a maximum of 0.9 mm. The accommodative amplitudes measured with the Hartinger coincidence refractometer (mean value 0.47 D) correspond to these values. Similar conclusions may be drawn from existing investigative results of the reference group, which are on the same order of magnitude as those of the 1 CU group. Objective accommodation measurements are needed to evaluate commercially available accommodative intraocular lenses in a scientifically satisfactory manner. Objectively measurable parameters include changes of the anterior chamber depth as well as refraction, as determined for instance by coincidence refractometry and streak retinoscopy. Future studies should also consider the IOL properties, astigmatism, and pupillary diameter. This is the only way to identify pseudoaccommodation and a decisive factor for further development of accommodative artificial lenses.

Accommodation, Ocular↗

PubMed2006

Long-term refractive and visual outcome after penetrating keratoplasty only versus the triple procedure in Fuchs' dystrophy.

BACKGROUND: Long-term refractive and visual outcome after penetrating keratoplasty (PK) only and the triple procedure in eyes with Fuchs' endothelial dystrophy were assessed and compared. DESIGN: Retrospective, non-randomized, cross-sectional, clinical, single-centre study. METHODS: Ninety-two eyes of 87 patients were divided into two groups. Group 1 consisted of 28 eyes (mean age 62+/-13 years) that had undergone PK only and group 2 consisted of 64 eyes (mean age 69+/-10 years) that had undergone the triple procedure. Inclusion criteria were: (1) Fuchs' dystrophy, (2) central nonmechanical trephination, (3) double-running suturing technique and (4) availability of 'two-sutures-out' findings. In all eyes, a central trephination was performed (donor trephination from the epithelial side) using the 193-nm excimer laser along metal masks with eight 'orientation teeth/notches'. A double-running 10-0 nylon suture was applied in all eyes. Subjective refractometry (trial glasses), standard keratometry (Zeiss) and corneal topography analysis (TMS-1, Tomey) were performed in all eyes with 'two-sutures-in', 'one-suture-out', and 'two-sutures-out'. Main outcome measures included refractive cylinder, keratometric and topographic net astigmatism, keratometric and topographic central power, best-corrected visual acuity (BCVA), spherical equivalent (SE) of manifest refraction, surface regularity index (SRI), surface asymmetry index (SAI), and regularity of keratometry mires. RESULTS: The results were compared between the two groups (i.e. group 1 vs group 2) at various stages (i.e. 'two-sutures-in', 'one-suture-out', 'two-sutures-out'). Refractive cylinder in dioptres [D] was 2.5/2.0/2.5 vs 2.0/1.5/3.0, keratometric astigmatism [D] was 3.5/2.6/3.0 vs 3.5/3.1/3.5 and topographic astigmatism [D] was 3.9/4.1/4.9 vs 4.2/5.0/5.1. Keratometric central power [D] was 41.7/42.4/43.8 vs 41.5/41.9/43.3 and topographic central power [D] was 42.3/43.6/43.7 vs 42.6/41.8/44.3. BCVA was 0.5/0.6/0.6 vs 0.5/0.5/0.5. SE [D] was 0.0 /0.0/-0.5 vs -0.5/-0.5/-1.1. SRI was 1.5/1.1/1.0 vs 1.4/1.4/1.2 and SAI was 1.0/0.8/1.0 vs 1.3/1.2/1.0. The proportion of 'regular' and 'mildly irregular' keratometry mires was 44% / 69% / 68% vs 29% / 46% / 66%. The differences between the two groups did not reach statistical significance at any of the stages. CONCLUSIONS: Refractive and visual outcome after the triple procedure did not differ significantly from that after PK only. Therefore, we recommend the triple procedure in elderly patients with Fuchs' dystrophy and cataract to avoid delayed visual rehabilitation and a second surgical procedure.

Adult↗

PubMed2000

Correlation among refractive, keratometric and topographic astigmatism after myopic photorefractive keratectomy.

BACKGROUND: Photorefrative keratectomy can be used to flatten the curvature of the anterior cornea and reduce the myopic refraction of the eye. This leads to unphysiological topographical changes of the cornea and may alter the conditions for examinations of corneal surface topography. The purpose of this study was to check for mutual agreement of three different methods of assessment of astigmatism before and after myopic photorefractive keratectomy (PRK). PATIENTS AND METHODS: Forty-seven eyes of 28 patients (age 32.7+/-6.6 years) following PRK using an 193-nm excimer laser were included in this study. 37 eyes were treated for pure myopia (-4.9+/-2.4 D) and 10 eyes for myopic astigmatism (sphere -2.0 to -7.0 D, cylinder -1.0 to -3.0 D). Preoperatively and at 18 months postoperatively, subjective refractometry, keratometry and topography analysis were performed. The axes of topographic and keratometric cylinder were standardized periodically (180 degrees) with respect to the refractive cylinder axis. RESULTS: Pre- and postoperatively, the absolute astigmatism values correlated highly significantly between all three methods (P< or =0.001). The mean refractive cylinder was 0.65+/-0.61 D preoperatively and 0.46+/-0.41 D postoperatively (P=0.2). The mean keratometric astigmatism was 1.14+/-0.64 D before and 0.94+/-0.50 D after PRK treatment (P=0.2). Among the three methods, the mean topographic astigmatism was the highest (P<0.001) preoperatively (1.31+/-0.56 D) and postoperatively (1.21+/-0.52 D) (P=0.3). In eyes treated for pure myopia, no difference between pre- and postoperative refractive, keratometric and topographic astigmatism was detected (P>0.5). The axes of both topographic and keratometric astigmatism correlated highly significantly with the refractive cylinder axis (R> or =30.9, P<0.0001). CONCLUSION: Up to 2 years after myopic PRK, the difference between refractive and keratometric astigmatism does not differ from the preoperative value, indicating an even corneal surface. The absolute astigmatism values and the cylinder axis correlated well between subjective and objective methods of astigmatism assessment. Thus, objective measurements may be helpful in determining the cylinder component of best spectacle correction after PRK. However, topographic analysis overestimates astigmatism values systematically before and after PRK.

Adult↗

PubMed1998

Sensitivity of the MTI photoscreener for amblyogenic factors in infancy and early childhood.

BACKGROUND: Screening for amblyogenic factors in infancy by pediatricians is unsatisfactory, as they hardly ever detect ametropia or microstrabismus. As photoscreening seems to be a helpful method to detect even small squint angles and refractive errors, we tested the MTI photoscreener for its sensitivity with respect to amblyogenic factors. PATIENTS AND METHODS: One hundred and twelve children aged 6-48 months were first examined with the MTI photoscreener. Then each child underwent complete medical examination by an ophthalmologist and an orthoptist. The examination included the Hirschberg test (corneal reflex evaluation), the Brückner test (fundus red reflex), and, where possible, the Lang stereotest, the cover test and visual acuity assessment, as well as a motility test, biomicroscopy, ophthalmoscopy in mydriasis and refractometry in cycloplegia. Exclusion criteria were any organic pathological results, manifest strabismus, ametropia > or = 2 D and astigmatism > or = 1 D. An orthoptist, a pediatrician and two ophthalmologists independently evaluated the Polaroid pictures according to the criteria given in the handbook of the MTI photoscreener. RESULTS: For 10 children the evaluation with the MTI photoscreener was not possible despite the fact that photographs were retaken several times. Thirteen photographs showing obvious pathologic findings despite their poor quality were included. Eighty-three of the remaining 102 children failed the eye examination according to the above-mentioned criteria. The mean sensitivity of the MTI photoscreener was determined to be 82.8%. The ability to correctly identify the absence of any amblyogenic factors (specificity) was 61.8%. CONCLUSIONS: Sensitivity was high when compared to the usually low detection rate during pediatric examinations. Due to the low specificity, effectiveness was poor. Therefore an ophthalmological examination should be included in the preventive screening during infancy and early childhood.

Amblyopia↗

PubMedDate not supplied

Near reflex substituting for acquired horizontal gaze palsy: a case report.

BACKGROUND: Some patients with acquired horizontal gaze palsy overcome the adduction palsy by utilizing convergence. This substitution phenomenon is very rare. We report a patient with horizontal gaze palsy who was able to use convergence to compensate for the lack of adduction in the left eye. CASE: The patient was a 31-year-old woman with an arteriovenous malformation in the fourth ventricle. She suffered right gaze palsy and right abducens palsy after tumor surgery and radiation therapy. OBSERVATIONS: Three years after the vascular accident, she was found to be able to adduct the left eye, in association with the adduction of the right eye. At the same time, constriction of both pupils and globe retraction of the left eye were observed. When she shifted the gaze direction of her left eye from left to right, an 11 and 8 diopter increase of myopia in the right and left eyes, respectively, was confirmed by objective refractometry. CONCLUSIONS: The existence of convergence substituting for adduction in this patient with horizontal gaze palsy was confirmed by refraction change in addition to pupillary change.

Abducens Nerve↗

PubMed2005

Solid lipid nanoparticles (SLN) and oil-loaded SLN studied by spectrofluorometry and Raman spectroscopy.

PURPOSE: Recently, colloidal dispersions made of mixtures from solid and liquid lipids have been described to overcome the poor drug loading capacity of solid lipid nanoparticles (SLN). It has been proposed that these nanostructured lipid carriers (NLC) are composed of oily droplets, which are embedded in a solid lipid matrix. High loading capacities and controlled release characteristics have been claimed. It is the objective of the present paper to investigate these new NLC particles in more detail to obtain insights into their structure. METHODS: Colloidal lipid dispersions were produced by high-pressure homogenization. Particle sizes were estimated by laser diffraction and photon correlation spectroscopy. The hydrophobic fluorescent marker nile red (NR) was used as model drug, and by fluorometric spectroscopy, the molecular environment (polarity) was elucidated because of solvatochromism of NR. The packaging of the lipid nanoparticles was investigated by Raman spectroscopy and by densimetry. The light propagation in lipid nanodispersions was examined by refractometry to obtain further insights into the nanostructural compositions of the carriers. RESULTS: Fluorometric spectroscopy clearly demonstrates that NLC nanoparticles offer two nanocompartments of different polarity to accommodate NR. Nevertheless, in both compartments, NR experiences less protection from the outer water phase than in a nanoemulsion. In conventional SLN, lipid crystallization leads to the expulsion of the lipophilic NR from the solid lipid. Measurements performed by densimetry and Raman spectroscopy confirm the idea of intact glyceryl behenate lattices in spite of oil loading. The lipid crystals are not disturbed in their structure as it could be suggested in case of oil incorporation. Refractometric data reveal the idea of light protection because of incorporation of sensitive drug molecules in NLC. CONCLUSION: Neither SLN nor NLC lipid nanoparticles did show any advantage with respect to incorporation rate compared to conventional nanoemulsions. The experimental data let us conclude that NLC lipid nanoparticles are not spherical solid lipid particles with embedded liquid droplets, but they are rather solid platelets with oil present between the solid platelet and the surfactant layer.

Colloids↗

PubMed1983

Chromatographic analysis of sugars in physiological fluids by postcolumn reaction with cuprammonium: a new and highly sensitive method.

A new highly sensitive method of high-performance liquid chromatographic analysis has been used to separate mono-, di-, and oligosaccharides present in jejunal aspirates from experimentally perfused animals. The sugars in the column eluant are detected at 280 to 310 nm after reaction with cuprammonium. No reaction coil is required between the column and uv detector because the reaction is virtually instantaneous. This technique is more sensitive than differential refractometry, so that it is possible to detect 2.5 nmol (450 ng) of glucose routinely, compared to a minimum detection limit of 100 nmol (18 micrograms) using a commercial refractive index detector. Using a suitable postcolumn pump, the technique is not sensitive to changes in solvent composition, as with gradient elution, and is applicable to analysis of other cis-cis glycols.

Ammonia↗

PubMed1980

Further characterization and N-terminal sequence of cobra venom phospholipase A2.

N-terminal amino acid sequence data on cobra venom phospholipase A2 (Naja naja naja) demonstrate the absence of histidine at positions 10 and 20, in contrast to most other Naja enzymes. The presence of three tryptophans was demonstrated by p-toluenesulfonic acid hydrolysis, and the location of two of these at positions 18 and 19 parallels other Naja phospholipase A2 sequences. Based on the amino acid composition of the enzyme, the theoretical E278 0.1% should be 2.2, which is consistent with dry weight determinations, refractometry and amino acid analysis. Unusually high reactivity of the enzyme toward the protein assay of Lowry et al. gives an erroneously low E278 0.1% value of 1.45 when compared to bovine serum serum albumin as a protein standard. Using an E278 0.1% of 2.2, this enzyme is inactivated by the active site reagent p-bromophenacyl bromide with a stoichiometry of 1 mol reagent per mol enzyme. Chromatography on Affi-Gel Blue provides further purification of this phospholipase A2.

Acetophenones↗

PubMed1989

Functional morphology of accommodation in the raccoon.

The raccoon (Procyon lotor) is a small carnivore which eats in the upright position, using hand- and finger-like front paws and digits to wash, hold and examine its food at close range. These anatomic and behavioral characteristics prompted structural and functional studies of the accommodative capability of this species. By light and electron microscopy, we observed a prominent ciliary smooth muscle and zonular apparatus. When stimulated by carbachol or pilocarpine, the muscle and zonular apparatus exhibited a shift from longitudinal to reticular or circular orientation of some ciliary muscle bundles, anterior movement of the muscle as a whole, and more oblique crossing of the zonular fiber bundles in the zonular plexus. Maximum carbachol-induced accommodative amplitude measured by coincidence refractometry ranged from 3 to 19 diopters in these 1 to 9 yr old animals, with no definite age-accommodation relationship. A-scan ultrasonographic biometry showed that during accommodation the lens thickened very little, if at all, but moved anteriorly, while the apparent cornea to retina distance increased slightly. The raccoon thus exhibits the greatest accommodative capability of any non-primate terrestrial mammal so far studied.

Accommodation, Ocular↗

PubMed1977

Characterization of functionally distinct lymphoid and myeloid cells from human blood and bone marrow. I. Separation by a buoyant density gradient technique.

A buoyant density gradient procedure for mammalian cell separation is described. Gradients of Ficoll and Hypaque in balanced salt solution were used in a zonal rotor to separate distinct leukocyte populations from human peripheral blood and bone marrow. This method possesses the advantages of uniform osmolarity, density determination by refractometry, ease of preparation of gradient solutions, large sample capacity, and low viscosity with consequent ease of sterilization. Granulocyte-monocyte colony-forming units (CFU-C) from blood and bone marrow banded as a homogeneous peak with a density of 1.056 g cm-3 on steep gradients. Recovery of CFU-C was 36% with a 7- to 9-fold enrichment on shallow gradients. Both fractionated and unfractionated peripheral blood cells were stimulated by phytohemagglutinin (PHA), Concanavalin A (Con A), and allogeneic lymphocytes. In contrast, cells from unfractionated bone marrow and cells from the light density fraction of marrow were inhibited by Con A and responded variably to PHA.

Blood Cells↗

PubMed1982

Chromatic dispersion of the ocular media.

Measurements of chromatic dispersion of aqueous and vitreous humors, cornea and lens of the eye are sparse and incomplete. The wavelength variation in refractive index of the ocular media of cow, pig, frog (Rana pipiens), chicken, rock bass (Ambloplites rupestris), albino rat and cat as well as human lenses was determined by means of Abbe and Pulfrich refractometry. While the humors are somewhat less dispersive than water, the cornea is more dispersive at short wavelengths. In general, the lens is significantly more dispersive than water with dispersion increasing asymptotically at the blue end of the spectrum. The exaggerated dispersion taking place at short wavelengths should be taken into account in calculations of chromatic aberration.

Adolescent↗

PubMed1983

Longitudinal chromatic aberration of the vertebrate eye.

A recent study involving Abbe and Pulfrich refractometry analyses the dispersion of the human lens and the ocular media of a number of vertebrates. In general, the lens and, to a lesser extent, the cornea, are more dispersive than expected at wavelengths below 500 nm. The dispersion findings of this study were used in conjunction with reduced eye parameters of a number of vertebrates to calculate the longitudinal chromatic aberration of rock bass, frog, chicken, rat, cat, pig, cow, and human eyes. The calculated chromatic aberration of the human eye is greater than values reported earlier, because of the exaggerated dispersion of the lens at short wavelengths. While the values calculated for the additional species studies may be larger in some instances than expected, presumably due to lens dispersion as well, chromatic aberration is not large enough to account for the hyperopia found by retinoscopic study of small eyes.

Animals↗

PubMed1985

A schematic eye for the mouse, and comparisons with the rat.

The thicknesses and spheric and aspheric curvatures of the optic components were measured from cross-sections of frozen eyes of C57B1/6J mice. The equivalent refractive index of the crystalline lens was obtained from its back-vertex power in albumin. Refractive indices of the cornea, aqueous and vitreous humors were obtained by refractometry or interferometry at four wavelengths across the visible spectrum. The measurements parallel earlier ones on the hooded rat. The eyes of the mouse and rat differ mainly in size, by a linear scale factor of 1.9-2.0, and only slightly in refractive index. Thus refraction, chromatic aberration, and retinal illumination are easily compared in the two species. An analysis of the contribution of each optical surface to refraction may facilitate extrapolation to other strains of mice. Chromatic aberration is discussed with respect to depth of field and the retinoscopy artefact.

Animals↗