Week 4 - exam prep Flashcards
Which of the following statements about the fovea is FALSE?
a) It is the center of the macula
b) It contains rod photoreceptors
c) It has maximum cone packing
d) The center of the fovea contains the foveal pit
B) It contains rod photoreceptors
: The fovea is the center of the macula and has maximum cone packing, making it essential for high acuity vision. However, it lacks rod photoreceptors, which are primarily found in the peripheral retina. The center of the fovea is characterized by the presence of the foveal pit, and Henle’s layer consists of axons of cones in the fovea coursing horizontally.
Which of the following retinal layers contains the cell bodies of rods and cones?
a) Retinal pigment epithelium
b) Outer Nuclear Layer
c) Inner Plexiform Layer
d) Ganglion cell layer
Outer Nuclear Layer
The Outer Nuclear Layer (ONL) contains the cell bodies of rods and cones, which are the photoreceptor cells responsible for capturing light stimuli.
The Inner Nuclear Layer (INL) contains the cell bodies of other retinal neurons such as horizontal, bipolar, and amacrine cells, involved in processing visual signals.
Which retinal layer plays an important role in photopigment regeneration and forms a barrier to prevent light scatter?
a) Outer Plexiform Layer
b) Inner Plexiform Layer
c) Retinal pigment epithelium
d) Retinal nerve fiber layer
Retinal pigment epithelium
The retinal pigment epithelium (RPE) plays a crucial role in photopigment regeneration and forms a barrier to prevent light scatter. It contains melanin, which helps absorb excess light and maintain the health and function of the photoreceptor cells.
Which retinal layer contains the junctions formed by the apical processes of Müller cells and photoreceptor cells?
a) Inner Nuclear Layer
b) Outer Plexiform Layer
c) Outer Nuclear Layer
d) Retinal pigment epithelium
Outer Plexiform Layer
The junctions formed by the apical processes of Müller cells and photoreceptor cells are found in the Outer Plexiform Layer (OPL) of the retina. These junctions facilitate communication between the photoreceptor cells (rods and cones) and the horizontal and bipolar cells, which are involved in the initial processing of visual signals.
Which pathway involves horizontal and amacrine cells providing local feedback to optimize the through pathway?
a) Through pathway
b) Lateral pathway
c) Horizontal pathway
d) Amacrine pathway
B) Lateral pathway
The lateral pathway involves horizontal and amacrine cells providing local feedback to optimize the through pathway, which consists of the sequential transmission of visual signals from photoreceptors to bipolar cells and then to ganglion cells. Horizontal and amacrine cells modulate the signals transmitted through the through pathway, enhancing visual processing and adaptation to different lighting conditions.
Which type of photoreceptor cells exhibit a higher convergence ratio, leading to better night vision?
a) Rods
b) Cones
c) Both rods and cones
d) Neither rods nor cones
Rods
Rods exhibit a higher convergence ratio compared to cones, with an average of approximately 120 rods converging to one ganglion cell. This higher convergence ratio in rods enhances their sensitivity to low light conditions, facilitating better night vision. In contrast, cones have a lower convergence ratio, with an average of about 6 cones converging to one ganglion cell, which contributes to better visual acuity in well-lit conditions.
Which statement accurately describes a function of the Retinal Pigment Epithelium (RPE)?
a) The RPE acts as a layer of pigmented cells, focusing energy exerted by the lens onto the retina.
b) The RPE transports iron, water, and metabolic end products from the blood to the subretinal space.
c) The RPE takes up nutrients from the choroid and delivers them to the photoreceptors, including recycling molecules important to the visual cycle.
d) The RPE stabilizes the high composition in the subretinal space using voltage-gated ion conductors.
C) The RPE takes up nutrients from the choroid and delivers them to the photoreceptors including recycling molecules important to the visual cycle.
Which artery supplies the inner retina and is the first branch of the ophthalmic artery?
a) Central retinal artery
b) Posterior ciliary artery
c) Lacrimal artery
d) Supraorbital artery
A) Central retinal artery
The central retinal artery is the first branch of the ophthalmic artery and supplies the inner retina with oxygenated blood. It pierces the dura approximately 1 cm from the globe and enters the optic nerve, where it gives off many collateral branches serving the optic nerve fibers prior to reaching the optic nerve head (ONH). The central retinal artery exits the optic nerve and is visible when viewing the fundus. The distribution of its branches includes temporal arcades that encircle the macula and nasal arcades that run radially.
Where is the highest oxygen content found in the retina?
a) Inner retina
b) Outer retina
c) Retinal Pigment Epithelium (RPE)
d) Fovea
C) Retinal Pigment Epithelium
Which of the following functions is NOT attributed to Nicotinamide adenine dinucleotide phosphate (NADPH) in the retina?
a) Forms reduced glutathione, an antioxidant.
b) Converts all-trans retinal to all-trans retinol.
c) Facilitates fatty acid synthesis, maintaining cell membrane integrity.
d) Inhibits nitric oxide synthesis, acting as a vasoconstrictor.
D) Inhibits nitric oxide synthesis, acting as a vasoconstrictor
What is the Dk (oxygen permeability) of CL governed by?
It is governed by EWC (effective water content) of the lens, which is the ability to pass water through the polymer.
What is Dk/t and what are some factors affecting it?
Relates to oxygen transmissibility.
It is dependent on:
- Dk value
- reduced thickness of CL –> increased Dk/t
- BVP and design
- minimum thickness – affects EWC
Which category of contact lens oxygen transmissibility (Dk/t) would likely result in corneal oxygen levels significantly higher than normal closed-eye conditions?
a) Low (Dk/t < 12)
b) Moderate (Dk/t = 12-25)
c) High (Dk/t = 26-50)
d) Super (Dk/t = 51-80)
D) Super
While lenses in the “High” category (Dk/t = 26-50) also increase corneal oxygen levels significantly, lenses in the “Super” category provide even greater oxygen transmission. Additionally, in the “Super” category, the effect of lens design on oxygen transmission is reduced compared to lower categories. Thus, lenses in the “Super” category are particularly effective at maintaining high corneal oxygen levels while minimizing the impact of lens design
How does SiH Lens transmit oxygen?
Oxygen is transmitted to the eye via silicone component rather than the WC
Which statement accurately describes the characteristics of third-generation silicone hydrogel contact lenses?
a) They are primarily composed of TRIS structures and plasma surface treated.
b) They utilize a modified Tanaka monomer and have a lower modulus compared to first-generation lenses.
c) They incorporate wetting agents in the lens coating to enhance surface wettability.
d) They do not follow the traditional water-Dk relationship and do not contain coating or wetting agents.
They do not follow the traditional water-Dk relationship and do not contain coating or wetting agents.
Field of view diminishes with increasing plus power. What happens with increasing minus lens?
The field of view increases.
