1|Page
ROUB EXAM AND STUDY GUIDE LATEST 2026 TEST
BANK| COMPLETE 250 ACTUAL EXAM QUESTIONS
AND CORRECT VERIFIED ANSWERS/ ALREADY
GRADED A+ (BRAND NEW!!)
How is corneal compression determined? - ANSWER - AC depth and/or
distance between initial spike and anterior lens spike
What is more likely to occur during contact method biometry? -
ANSWER - Corneal depression
What are three advantages of A-scan immersion technique? - ANSWER
- Proper sound beam alignment, no corneal compression, corneal and
crystalline lens thickness measured
What generally causes short axial length measurements? - ANSWER -
An air bubble in the water of the probe
What is the correction factor for the normal cornea when measuring
axial length? - ANSWER - 0.04 mm
A long measurement is generally caused by what issue? - ANSWER -
Air bubbles in the fluid bath (immersion)
pg. 1
,2|Page
What is the axial length measurement of an eye containing silicone oil as
compared to a normal eye? - ANSWER - The eye with the silicone oil
will measure longer than the normal eye
What biometry technique is best for patients with blepharospasms and
fixation difficulties? - ANSWER - Immersion
What is the cause of most measurement errors? - ANSWER - Improper
instrument settings and/or improper examination techniques
How are final measurements determined? - ANSWER - By taking the
average of the longest readings from the scans of the highest quality
How is a dense cataract indicated on the ultrasound? - ANSWER - Extra
echoes between the anterior and posterior lens
What is the cause of the sound beam directed to the optic disc producing
an incorrect measurement? - ANSWER - An axial length A-scan where
there is one tall echo from the back of the eye with no other echoes
behind it
What ocular abnormality would cause an indistinct retinal spike? -
ANSWER - Intraocular lesion, posterior staphyloma
pg. 2
,3|Page
What should be asked when taking a history prior to an axial eye length
measurement? - ANSWER - Past surgeries, diabetes, AMD, myopia,
hyperopia, amblyopia
In immersion, how do you know you have correct alignment? -
ANSWER - Double peaked corneal spike
In immersion, What spikes are seen on a phakic eye? - ANSWER -
Initial spike, anterior/posterior, cornea, lens surface, retina, sclera,
orbital fat
Approximately how many millimeters in an average cornea? - ANSWER
- 0.5 mm
What is the most accurate mode to use on immersion? - ANSWER -
Manual
What does the presence of a scleral echo confirm? - ANSWER - You are
aligned on the retina and not on the optic disc
If the retinal spike is separated from the scleral spike, what does this
indicate? - ANSWER - Possible retinal detachment
How should you position a patient with silicone oil in their eye? -
ANSWER - In a supine position
pg. 3
, 4|Page
When performing keratometry, what is done first? - ANSWER - Focus
the eyepiece
Initial keratometry measurements of the cornea are done in millimeters
then converted to what measurement? - ANSWER - Diopters
What amount of refractive power does the cornea supply to the eye? -
ANSWER - two-thirds
What comprises the steepness of the cornea? - ANSWER - Corneal
diameter and axial length
Smaller and steeper corneas are related to what type of eyes? -
ANSWER - Shorter
Larger and flatter corneas are related to what type of eyes? - ANSWER -
Longer
Should a keratometry reading be taken before or after an A-scan? -
ANSWER - Before
How many diopters of error may be caused if the keratometer is
improperly calibrated? - ANSWER - 1D
pg. 4
ROUB EXAM AND STUDY GUIDE LATEST 2026 TEST
BANK| COMPLETE 250 ACTUAL EXAM QUESTIONS
AND CORRECT VERIFIED ANSWERS/ ALREADY
GRADED A+ (BRAND NEW!!)
How is corneal compression determined? - ANSWER - AC depth and/or
distance between initial spike and anterior lens spike
What is more likely to occur during contact method biometry? -
ANSWER - Corneal depression
What are three advantages of A-scan immersion technique? - ANSWER
- Proper sound beam alignment, no corneal compression, corneal and
crystalline lens thickness measured
What generally causes short axial length measurements? - ANSWER -
An air bubble in the water of the probe
What is the correction factor for the normal cornea when measuring
axial length? - ANSWER - 0.04 mm
A long measurement is generally caused by what issue? - ANSWER -
Air bubbles in the fluid bath (immersion)
pg. 1
,2|Page
What is the axial length measurement of an eye containing silicone oil as
compared to a normal eye? - ANSWER - The eye with the silicone oil
will measure longer than the normal eye
What biometry technique is best for patients with blepharospasms and
fixation difficulties? - ANSWER - Immersion
What is the cause of most measurement errors? - ANSWER - Improper
instrument settings and/or improper examination techniques
How are final measurements determined? - ANSWER - By taking the
average of the longest readings from the scans of the highest quality
How is a dense cataract indicated on the ultrasound? - ANSWER - Extra
echoes between the anterior and posterior lens
What is the cause of the sound beam directed to the optic disc producing
an incorrect measurement? - ANSWER - An axial length A-scan where
there is one tall echo from the back of the eye with no other echoes
behind it
What ocular abnormality would cause an indistinct retinal spike? -
ANSWER - Intraocular lesion, posterior staphyloma
pg. 2
,3|Page
What should be asked when taking a history prior to an axial eye length
measurement? - ANSWER - Past surgeries, diabetes, AMD, myopia,
hyperopia, amblyopia
In immersion, how do you know you have correct alignment? -
ANSWER - Double peaked corneal spike
In immersion, What spikes are seen on a phakic eye? - ANSWER -
Initial spike, anterior/posterior, cornea, lens surface, retina, sclera,
orbital fat
Approximately how many millimeters in an average cornea? - ANSWER
- 0.5 mm
What is the most accurate mode to use on immersion? - ANSWER -
Manual
What does the presence of a scleral echo confirm? - ANSWER - You are
aligned on the retina and not on the optic disc
If the retinal spike is separated from the scleral spike, what does this
indicate? - ANSWER - Possible retinal detachment
How should you position a patient with silicone oil in their eye? -
ANSWER - In a supine position
pg. 3
, 4|Page
When performing keratometry, what is done first? - ANSWER - Focus
the eyepiece
Initial keratometry measurements of the cornea are done in millimeters
then converted to what measurement? - ANSWER - Diopters
What amount of refractive power does the cornea supply to the eye? -
ANSWER - two-thirds
What comprises the steepness of the cornea? - ANSWER - Corneal
diameter and axial length
Smaller and steeper corneas are related to what type of eyes? -
ANSWER - Shorter
Larger and flatter corneas are related to what type of eyes? - ANSWER -
Longer
Should a keratometry reading be taken before or after an A-scan? -
ANSWER - Before
How many diopters of error may be caused if the keratometer is
improperly calibrated? - ANSWER - 1D
pg. 4
