Week 3 - Exam prep Flashcards
What factor(s) influence(s) the amount of light scattered in the phenomenon of scattering of light?
A) Refractive index inhomogeneities
B) Intensity of the incoming light
C) Size, shape, and refractive index of the scattering source
D) All of the above
All of the above
Firstly, it occurs due to refractive index inhomogeneities on a microscopic scale. Secondly, the amount of light scattered is indeed proportional to the intensity of the incoming light. Lastly, the angular distribution of scattered light depends on various characteristics of the scattering source, including its size, shape, refractive index, and spatial distribution. Therefore, all the given factors (refractive index inhomogeneities, intensity of incoming light, and characteristics of the scattering source) collectively influence the amount of light scattered.
Which statement(s) accurately describe(s) the wavelength dependence in the scattering of light?
A) Rayleigh scattering is stronger for shorter wavelengths, following an inverse proportionality to the fourth power of the wavelength.
B) Scattering by particles smaller than one-tenth of the wavelength of the incident light primarily occurs in Rayleigh scattering.
C) Mie scattering exhibits stronger scattering compared to Rayleigh scattering but is not wavelength dependent.
D) Both A and C
A and C are correct
Rayleigh scattering is characterized by stronger scattering for shorter wavelengths, following an inverse proportionality to the fourth power of the wavelength. This phenomenon is particularly notable in scattering by particles smaller than one-tenth of the wavelength of the incident light, such as atmospheric gases. On the other hand, Mie scattering, which occurs with larger particles, exhibits stronger scattering compared to Rayleigh scattering, but it is not dependent on the wavelength of the incident light. Therefore, statements A and C accurately describe the wavelength dependence in the scattering of light.
Is Rayleigh Scattering dependent on wavelength?
Yes
1/wavelength ^4
How is Mie scattering different with large and small particles?
What is the relationship of particle size and light scattering in forward direction?
how scatter reduced visual performance
Which statement best describes the vitreoretinal attachment?
A) The posterior vitreous cortex attaches mechanically to the retinal nerve fiber layer (RNFL).
B) The internal limiting membrane (ILM) of the retina, derived from Müller cells, serves as a site for attachment with the vitreous.
C) The vitreous attachment is primarily mediated by type I collagen.
D) Membrana limitans interna (MLI) acts as a physical barrier preventing vitreous adherence to the retina.
B) The internal limiting membrane (ILM) of the retina, derived from Mullers Cells, serves as a site for attachment with the posterior vitreous cortex
The vitreoretinal attachment involves the posterior vitreous cortex attaching to the internal limiting membrane (ILM) of the retina. The ILM is a basement membrane derived from the end feet of Müller cells and is approximately 1-3 µm thick. It consists of various components including type IV collagen, laminin, fibronectin, and type I collagen. The Membrana limitans interna (MLI) serves as a biochemical glue, adhering the vitreous to the ILM without mechanical attachment. Therefore, option B accurately describes the vitreoretinal attachment.
MTF: How much of the object properties are preserved in the image
A: Normal Human eye
B: Patients with multiple sclerosis → mid to low spatial frequencies
C: Patients with cataracts → overall spatial frequencies
D: Mild refractive error or mild amblyopia → high spatial frequencies
E: In a perfect lens system → All spatial frequencies pass evenly
If the bright bar of a sine-wave grating has a luminance of 90 foot-lamberts, and the
dark bar has a luminance of 30 foot-lamberts, the grating Michelson contrast is:
a. 0.25
b. 0.50
c. 0.75
d. 1.00
B. 0.50
All of the sine-wave gratings listed below have equally low contrast. Which frequency is
most visible?
a. 10 cycles/degree
b. 20 cycles/degree
c. 30 cycles/degree
d. 40 cycles/degree
A. 10 cycles/degree
In the context of sine-wave gratings, the frequency that is most visible tends to be the one that is lower. When all gratings have equally low contrast, the lower frequency tends to be more visible due to the higher sensitivity of the visual system to lower spatial frequencies. Therefore, option a, with 10 cycles/degree, is most likely to be the most visible among the given options.
Prior adaptation to a sine-wave grating of 10 cpd will result in a subsequent reduction of
sensitivity at:
a. 5 cycles/degree
b. 10 cycles/degree
c. 20 cycles/degree
d. all spatial frequencies
B. 10 cycles/degree
Adaptation to a specific spatial frequency can result in reduced sensitivity to that frequency and its harmonics. In this case, adaptation to a sine-wave grating of 10 cycles per degree (cpd) would lead to reduced sensitivity at the same spatial frequency, i.e., 10 cycles/degree. Therefore, the correct answer is option b.
What test assess contrast sensitivity in various spatial frequencies?
a. Melbourne Edge Test
b. Mars (Lighthouse) Test
c. Functional Acuity Contrast Test
d. Pelli-Robson Test
C. Functional Acuity Contrast Test
The Functional Acuity Contrast Test (FACT) is designed to assess contrast sensitivity across various spatial frequencies. It measures the ability to discriminate between light and dark areas of varying spatial frequencies, providing information about the visual system’s performance in different frequency bands. Therefore, option c, the Functional Acuity Contrast Test, is the correct answer.
Which of the following acuities is most related to a threshold measured in static perimetry?
a. minimum detectable
b. recognition
c. resolution
d. vernier
Minimum detectable
At a distance of 20m, a patient has a Contrast Sensitivity Function (CSF) that peaks at 4 cycles/degree. When measured at 6m, this patient’s CSF is expected to peak at:
a. 2 cycles/degree
b. 4 cycles/degree
c. 6 cycles/degree
d. 8 cycles/degree
B. 4 cycles/degree
When measuring contrast sensitivity function (CSF), the spatial frequency peak remains constant regardless of viewing distance, as long as the visual angle remains the same. Since spatial frequency is inversely proportional to viewing distance, halving the viewing distance would double the spatial frequency. Therefore, if the CSF peaks at 4 cycles/degree at 40 ft, it would also peak at 4 cycles/degree when measured at 20 ft. Hence, the correct answer is option b.
Difference between Hydrophobic and Hydrophilic IOL
Hydrophobic:
Higher glistening
Lower PCO
Hydrophilic
Higher PCO
Possible risk of opacification with RD gas
