The document discusses various types of optical aberrations that can occur in the eye. It describes monochromatic aberrations, which are caused by the geometry of the lens, and chromatic aberrations, which are caused by dispersion and the variation of the lens refractive index with wavelength. It also discusses how wavefront aberrometry can be used to measure aberrations by analyzing the distortion of reflected light to generate a map of the optical system of the eye. Common higher-order aberrations measured include coma, spherical aberration, and trefoil.
Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.
I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..
Hope u all like it and may help you in learning better. :)
Detailed instumentaion and use of manual Lensometer and just a outline of automated lensometer.
I have used the picture of manual lensometer with out the parts describtion because i have explained orally by showing the picture..
Hope u all like it and may help you in learning better. :)
Ophthalmic Prisms: Prismatic Effects and DecentrationRabindraAdhikary
Ophthalmic Prisms: Prismatic Effects and Decentration
here we discuss about the ophthalmic prisms, the prismatic effects as caused by the decentration( moving the optical center away from the visual axis)
what is Duochrome Test, Why do we take Red and Green color only,
What is the Principal of Duochrome Test, Why Hyperopic Pt sees green better than red and vice versa
Ophthalmic Prisms: Prismatic Effects and DecentrationRabindraAdhikary
Ophthalmic Prisms: Prismatic Effects and Decentration
here we discuss about the ophthalmic prisms, the prismatic effects as caused by the decentration( moving the optical center away from the visual axis)
what is Duochrome Test, Why do we take Red and Green color only,
What is the Principal of Duochrome Test, Why Hyperopic Pt sees green better than red and vice versa
Optical Aberration is the phenomenon of Image Distortion due to Optics Imperfection.
For comments please contact me at solo.hermelin@gmail.com.
For more presentations visit my website at http://www.solohermelin.com.
This presentation is in the Optics Folder. Since some of the Figures were not downloaded I recommend to see the presentation on my website.
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optical aberration is very important for optometrist .
eyeball is not optically perfect it shows some optical flaws which reduce resolution of the focused image they are called aberration.
Aberration in optics refers to a defect in a lens such that light is not focused to a point, but is spread out over some region of space, and hence an image formed by a lens with aberration is blurred or distorted.
In this term paper most of the types of lens aberrations have been discussed and also have discussed about the use of this knowledge. The aberrations covered in this presentation are:-
Monochromatic Aberrations--Spherical Aberration, Coma, Field Curvature, Distortion, Astigmatism. Chromatic Aberrations - Longitudinal Chromatic Aberrations and Transverse Chromatic Aberrations.
Optical aberration is an imperfection in the image formation of an optical system
Abberation can cause difficulty seeing at night, glare, halos, blurring, starburst patterns or double vision (diplopia).
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Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
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These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
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i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
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Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
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1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
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3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
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1. Define an electrocardiogram (ECG) and electrocardiography
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3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
2. Optical aberration is an imperfection in the
image formation of an optical system.
Aberrations fall into two classes:
monochromatic and
chromatic.
3. Monochromatic aberrations are caused by the
geometry of the lens and occur both when
light is reflected and when it is refracted. They
appear even when using monochromatic light,
hence the name.
Chromatic aberrations are caused by
dispersion, the variation of a lens's refractive
index with wavelength. They do not appear
when monochromatic light is used.
4. One needs to keep in mind these important
points: unlike the standard eye model, an
actual eye is:
An active optical system, with adjustable
components and aberrations varying in time,
It is not strictly centered system,
It is not a rotationally symmetrical system, and
Final perception is the subject of neural
processing.
5. Aberrations can be defined as the difference in
optical path length (OPL) between any ray
passing through a point in the pupillary plane
and the chief ray passing through the pupil
center.
This is called the optical path difference
(OPD) and would be for a perfect optical
system.
6. Wavefront aberrometer shines a perfectly
shaped wave of light into the eye and captures
reflections distorted based on the eye’s surface
contours.
Thus, it generates a map of the optical system
of the eye, which can be used to prescribe a
solution, correcting the patient’s specific
vision problem.
7. Another way of characterizing the wavefront is to
measure the actual slope of light rays exiting the
pupil plane at different points in the plane and
compare these to the ideal; the direction of
propagation of light rays will be perpendicular to
the wavefront.
This is the basic principle behind the Hartman-
Shack devices commonly used to measure the
wavefront.
Wavefronts exiting the pupil plane are allowed to
interact with a microlenslet array.
8. If the wavefront is a perfect flat sheet, it will form a
perfect lattice of point images corresponding to the
optical axis of each lenslet.
If the wavefront is aberrated, the local slope of the
wavefront will be different for each lenslet and result in
a displaced spot on the grid as compared to the ideal.
The displacement in location from the actual spot
versus the ideal represents a measure of the shape of
the wavefront.
9. Wavefront maps are commonly displayed as
2-dimensional maps.
The color green indicates minimal wavefront
distortion from the ideal.
While blue is characteristic of myopic
wavefronts and red is characteristic of
hyperopic wavefront errors.
10. Once the wavefront image is captured, it can be
analyzed.
One method of wavefront analysis and classification
is to consider each wavefront map to be the weighted
sum of fundamental shapes.
Zernike and Fourier transforms are polynomial
equations that have been adapted for this purpose.
Zernike polynomials have proven especially useful
since they contain radial components and the shape
of the wavefront follows that of the pupil, which is
circular.
11.
12. Following the above division of the Zernike
expansion adopted in ophthalmology,
monochromatic eye aberrations are addressed as:
(1) lower-order aberrations, with the Zernike radial
order n<3, and
(2) higher-order aberrations, with n≥3.
13. The important optical aberrations that affect
vision are:
2nd Order optical aberrations – currently
measured in all eye exams providing sphere,
cylinder and axis corrections
3rd and 4th Order optical aberrations – high
order aberrations currently not measured in
today’s eye exams but can account for up to
20% of the eye’s refractive error.
14. 5th and 6th Order optical aberrations –also high
order aberrations not currently measured in
today’s eye exam.
These aberrations are of less significance
clinically, however they manifest in reduced
vision for a small percentage of eyes.
15. The lower-order aberrations are
Piston
Tilt
Defocus
Astigmatism
The 2nd order aberrations, defocus and
primary astigmatism - are the most significant
contributors to the overall magnitude of eye
aberrations
Lower-order aberrations
16. Remaining lower-order forms, piston and tilt,
or distortion, are usually ignored.
The former being not an aberration with a
single imaging pupil, and
The latter being not a point-image quality
aberration).
17.
18. Higher order aberrations are measured with
wavefront aberrometers and expressed in
terms that describe the shape and severity of
the deviated light rays as they pass through the
eye's optical system and strike the retina.
Coma, spherical aberration, and trefoil are the
most common higher order aberrations .
19. Coma causes light to be smeared like the tail of a
comet in the night sky.
Double vision is a common symptom of coma.
Trefoil causes a point of light to smear in three
directions, like a Mercedes-Benz symbol.
Spherical aberration is characterized by halos,
starbursts, ghost images, and loss of contrast
sensitivity (inability to see fine detail) in low light.
20. Starbursts – Patterns of Small Lights Around
Light Sources
Haloes – Circles of Light Around Light Sources
Ghosting – A Faint Duplicate of Each Object
Similar to Double Vision
Glare – Intensification of Light Sources.
It's quite common for a patient to have an increase
in all of these aberrations, resulting in distorted
night vision when the pupil opens and allows light
to enter through a larger area of the irregular
corneal surface.
21.
22. A comet-like tail or directional flare appearing in the
retinal image, when a point source is viewed.
Because the eye is a somewhat nonaxial imaging
device, and because the cornea and lens are not
perfectly centered with respect to the pupil, coma
generally is present in all human eyes.
A large amount of coma (0.3 μm of coma alone) may
point to known corneal diseases, such as
keratoconus.
23. Fortunately, spherical aberration is
relatively easy to understand.
For a normal photopic eye, spherical
aberration may vary from
approximately 0.25 D to almost 2 D.
Light rays entering the central area of
a lens are bent less and come to a
sharp focus at the focal point of a lens
system.
However, peripheral light rays tend to
be bent more by the edge of a given
lens system so that in a plus lens, the
light rays are focused in front of the
normal focal point of the lens and
secondary images are created.
24. This is why many lens systems
incorporate an aspheric grind, so
that the periphery of the lens
system gradually tapers and
refracts or bends light to a lesser
degree than if this optical
adaptation was not included.
The variation in index of
refraction of the crystalline lens
(higher index in the nucleus, lower
index in the cortex) is responsible
for neutralization of a good part of
the spherical aberration caused by
the human cornea.
25. Because the index of refraction of the ocular
components of the eye varies with
wavelength, colored objects located at the
same distance from the eye are imaged at
different distances with respect to the retina.
This phenomenon is called axial chromatic
aberration. In the human eye the magnitude of
chromatic aberration is approximately 3 D.
26. However, significant colored fringes around
objects generally are not seen because of the
preferential spectral sensitivity of human
photoreceptors.
Studies have shown that humans are many
times more sensitive to yellow–green light
with a central wavelength at 560 nm than to
red or blue light.