Following are selected questions and answers from courses tutored in the second semester of the 2007/2008 (1428/1429H) session
OPTO 272 - Visual Science II
MCQ Examples
Which of the following is the probable origin of the vertebrate ERG?
A. Rods and cones B. Horizontal cells C. Muller cells D. Bipolar cells
A single dim flash, 2.5 units lower than the standard bright flash generated under no background
light after at least half an hour of dark adaptation, will assess which of the following?
A. Cone Response
B. Maximum dark-adapted response
C. Maximum light-adapted response
D. Rod Response
In the retinal ganglion cell receptive field, the maximum response is obtained when the stimulus
spot of light:
A. Fills the outer and inner circles
B. Fills only the outer circle
C. Fills only the inner circle
D. None of the aforementioned options
A lesion of the pituitary gland will most likely cause which of the following visual field defects?
A. Right homonymous hemianopia B. Left homonymous hemianopia
C. Bitemporal hemianopia D. Left homonymous superior quadrantanopia
As a result of the loss of one of the one of the functions of the RPE, an albino will have all of the
following conditions except:
A. Nystagmus B. Photophobia C. Reduced VA D. Aniseikonia
Short Essay Examples
In a normal subject, the measured Just Noticeable Difference (JND), varies with the state of light
adaptation of the subject. Discuss this phenomenon.
Very early experiments found that if the JND of a subject was measured at different levels of light adaptation, it would vary accordingly.
At high light adaptation levels, the measured JND would be at its highest, gradually reducing as the ambient light is dimmed (and subsequently adapted to by the eye), until, in a completely dark-adapted state the JND would reach its absolute minimum (absolute light threshold), a figure that is about 1/10,000 of its initial value.
The reason for this decrease in JND is an increase in the subject’s sensitivity to light, and is a manifestation of the fact that the eye is much more sensitive to contrast than it is to brightness alone.
Explain the term ‘Critical Fusion Frequency’.
The sensation of ‘flicker’ is invoked when intermittent light stimuli are presented to the eye.
As the frequency of presentation increases, a point called the critical fusion frequency is reached at which the sensation of flicker disappears and is replaced by a
sensation of continuous stimulation.
OPTO 364 - Clinical Methods IV
MCQ Examples
All of the following can cause neovascularlization of the anterior chamber angle Except:
A. Eales disease B. Diabetic retinopathy C. Uveaitis D. Glaucoma
The scale of the Schiotz tonometer measures most accurately when the reading is between X and
Y units. What are X and Y?
A. 3 and 13 units B. 4 and 14 units C. 5 and 15 units D. 6 and 16 units
The uncorrected vision for OD is 20/80, and for OS is 20/60. You need to carry out a binocular
subjective refraction for OS. Which of the following statements is correct?
A. Fog OS and OD to 20/100 and then refract OS
B. Do not fog either eye, just refract OS
C. Fog OD to 20/100, then refract OS
D. None of the preceding options
A rare condition in which a jerky-type Nystagmus is manifest in both eyes of a patient, when
either eye is occluded, is called:
A. Amaurotic Nystagmus B. Cerebral Nystagmus
C. Latent Nystagmus D. Ataxic Nystagmus
One of the following features is ONLY associated with Angle-Closure glaucoma.
A. Haloes around lights B. Unexplained headaches
C. Family History of glaucoma D. None of the preceding options
Short Essay Examples
Discuss the effect of astigmatism on IOP measurement and how to overcome this effect.
Regular corneal astigmatism causes the mires in applanation tonometry to be elliptical rather
than circular.
The error in the readings will be about 1 mmHg for every 4D of corneal astigmatism (with- or against-the-rule). With the mires in the normal horizontal position, with-the-rule astigmatism is underestimated and against-the-rule astigmatism is overestimated but there is no need to bother for astigmatism less than 5D or if the astigmatism is oblique.
Measuring IOP with the mires horizontal and then vertical and averaging the readings reduces the error. Ideally, measuring IOP in the meridian approximately 430 away from the flattest meridian reduces the error to the barest minimum.
Compare and contrast direct non-contact fundus biomicroscopy and direct contact fundus
biomicroscopy. Give one example of each technique.
Direct Contact Fundus Biomicroscopy |
Direct non-contact Biomicroscopy |
|
|
|
|
1) Contact lenses with up to 4 mirrors
inclined at different angles, are used. |
A high minus non-contact lens (-55 to –59) is used to neutralize the ocular power and see the fundus |
|
2) The mirrors here afford a better
peripheral view, and even allow
gonioscopy |
Field of view is restricted by the pupil. |
|
Example: Goldmann 3-mirror lens. |
Example: Hruby lens. |
OPTO 493 - Orthoptics
MCQ Examples
The Bagolini glass test is used to detect all of the following EXCEPT:
A. Eccentric Fixation B. Anomalous retinal correspondence
C. Amblyopia D. Suppression
Suppression may develop to overcome or avoid all of the following symptoms Except:
A. Amblyopia B. Binocular diplopia C. Confusion D. Incompatible images
A pseudostrabismus may result from all of the following except:
A. Heterochromia Irides B. Palpebral fissure asymmetry C. Iritis D. Epicanthus
The active cortical inhibition of unwanted stimuli, is called:
A. Amblyopia B. Hypophoria C. Strabismus D. Suppression
Conjugate movement of both eyes, originating in the frontal lobe, and generating speeds of up to
4000/sec are called:
A. Saccadic movements B. Vergence movements
C. Smooth pursuit movements D. None of the preceding options
Short Essay Examples
Differentiate between binocular vision and binocular single vision
In binocular vision, there is simultaneous perception of two images - one from each eye. There is no fusion of these images into a single image. In its more manifest form, the patient easily reports diplopia when 'seeing' with both eyes.
In binocular single vision, there is simultaneous use of both eyes to give a single mental image of the object of regard. We can say that binocular single vision is an advanced form of binocular vision. Normal binocular single vision is bifoveal and there is no manifest deviation.
Differentiate between Normal and Abnormal retinal correspondence
When a person with normal binocular vision looks at an object, the image of that object falls on
both foveae. In this case both foveas receive information from the same object and the brain
fuses both uniocular images into one. The foveas are said to be related (conjugate or corresponding). Based on the fovea-fovea correspondence, the completion of normal retina to retina conjugation takes place so that (for example) a point 3mm nasal from the left fovea corresponds exactly with another point which is approximately 3mm temporal from the right fovea. Eventually all point on the left retina have exact corresponding points on the right retina. This is Normal Retinal Correspondence (NRC).
In abnormal retinal correspondence what happens is that the initial NRC relationship between both retinas is lost (for example due to a blunt trauma that comprises the function of the lateral rectus of one eye leading to esotropia). In esotropia, one eye is turned so that both foveas no longer perceive the same objects. The ‘errant’ is quickly suppressed in most cases and the brain locates the point on the ‘errant’ eye which perceives the same object as the good eye. Depending on whether this extrafoveal point lies within a well-defined locus of points (Panum’s fusional area) surrounding the ‘errant’ fovea (a relationship may be formed between the good fovea and any of the points within this locus – the opposite would true if the ‘good’ fovea was the ‘errant’ fovea). If the extrafoveal point lies within Panum’s area, then the old fovea-to-fovea relationship is cancelled and a new relationship is made between the ‘good’ fovea and the extrafoveal point on the ‘errant’ eye. This relationship redefinition takes place for all the other retinal points so that eventually the left retina is now related to the right retina in a different, less precise manner than previously. This new retina-retina relationship is what is referred to as Abnormal Retinal Correspondence (ARC).