Opt. Gla Flashcards
Micro-organisms most commonly achieve resistance to penicillin by employing which mechanism?
Alteration of ribosomes
Secretion of biofilms
Alteration of epitopes
Secreting beta-lactamase
Secreting beta-lactamase
The molecular structure of penicillin contains a beta-lactam ring. Some microorganisms secrete beta-lactamase, an enzyme that cleaves the beta-lactam ring, thereby destroying the penicillin molecule and its effectiveness. All other mechanisms noted above may be used by other bacteria, but they are not effective against achieving resistance to penicillin.
Which of the following regarding deoxyribonucleic acid (DNA) is FALSE?
Complementary base pairs include AU and GC
It is composed of polymers of nucleotides linked via phosphodiester bonds
It is helical in shape with a hydrophobic core
DNA is double-stranded
Deoxyribonucleic acid (DNA) contains genetic information necessary for proper function and development of living organisms. It consists of polymers of nucleotides which are linked via phosphodiester bonds. DNA is double-stranded and contains the complementary base AT and CG, which are linked in an antiparallel fashion. GC bonds are stronger than AT bonds as they contain more hydrogen bonds (3 vs. 2 respectively). Therefore, DNA with a higher CG content is considered more stable. The DNA strands are wound in a right-handed tightly coiled helix. The nucleobases are centered towards the core, causing the center of the helix to be hydrophobic.
On binocular indirect ophthalmoscopy of your 43 year-old patient, you see what appears to be a small U-shaped retinal tear in the far periphery at the 12 o’clock position of the left eye. You decide to use your 3-mirror Goldmann lens to obtain another view of the retina. Which 2 of the following modifications can be made in order to allow for the furthest possible peripheral view? (Select 2)
Tilt the Goldmann lens down
Have the patient look up
Tilt the Goldmann lens up
Have the patient look down
Correct answer Tilt the Goldmann lens down
Correct answer Have the patient look up
There are some cases where a more peripheral view of the retina is desired than that which can be achieved with the patient in primary gaze and the Goldmann lens held in the upright position. In these situations, certain modifications can be made such as tilting the Goldmann lens or having the patient move their eyes. The lens should be tilted in the opposite direction of the location of the lesion, and the patient should be instructed to look in the actual direction of the area being viewed.
For example, in the above question, the suspected lesion is at the 12 o’clock position. To obtain a more peripheral view, the lens should be tilted down, and the patient should be asked to look up.
What is generally different about the anterior chamber of hyperopic patients when comparing them to myopic patients?
Deeper anterior chambers
Shallower anterior chambers
Wider anterior chambers
There is no difference in anterior chamber depth between the two
Shallower anterior chambers
On average, hyperopic patients tend to have shallower anterior chambers when compared to emmetropes. In contrast, myopes usually possess deeper anterior chambers. It is for this reason that the depth of the anterior chamber must be measured prior to dilation. If the chamber is very shallow there is a chance that the angle may close with mydriasis, impeding the drainage of aqueous and causing a potentially damaging spike in intraocular pressure.
If atoms and molecules of light contain electrons with the same frequency as that of the medium in which they enter, the medium will __________ the energy of the light wave and convert it to __________ energy.
reflect, potential
absorb, thermal
transmit, potential
transmit, thermal
reflect, kinetic
absorb, kinetic
absorb, thermal
When atoms and molecules of light contain electrons with the same frequency as that of the medium in which they enter, the medium will absorb the energy and convert it to thermal (heat) energy. The light will not be able to continue to pass as light itself.
If frequencies of light waves do not match the frequency of the particles in a medium (or object), upon interaction, the electrons will vibrate for a brief period of time and then the energy is re-emitted as a light wave.
If the medium is transparent, the light is transmitted.
If the medium is opaque, the light is reflected.
What type of kinetics is displayed by the majority of topical ophthalmic drops?
Third-order kinetics
Zero-order kinetics
Second-order kinetics
First-order kinetics
First-order kinetics
The majority of topical ophthalmic drugs display a first-order rate of elimination. A zero-order rate of elimination will result in a drug being eliminated at a constant rate. A zero-order process is independent of the concentration of the drug; therefore, increasing the amount of the drug will not result in a faster rate of drug elimination. In comparison, a first-order rate of elimination is largely dependent on the concentration of the drug. Increasing the amount or dose of the substance will result in a quicker rate of drug elimination. Second-order and third-order rates of elimination do not exist in pharmacokinetics.
Recent studies have demonstrated the implication of which type of cell damage in the early stages of glaucoma?
Beta cells
Parvo cells
Horizontal cells
Magno cells
Rod cells
Magno cells
With their larger diameter, magno cells may be at risk and can be damaged before smaller neurons such as parvo cells. Recent data suggests that if we can detect damage to magno cells earlier, we may be able to greatly limit damage caused by glaucoma. Due to the ability of magno cells to respond to high temporal frequencies as well as the fact that the cells respond nonlinearly, the integrity of this pathway is able to be tested via a technique that is based upon frequency doubling. Research has demonstrated deficient frequency doubling in people displaying early stages of primary open angle glaucoma.
