Subjective Refraction Overview and Pre-presentation Flashcards Preview

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why prescribe? 4

1. improve VA
2. improve binocular function
3. prevent ambylopia
4. improve general function


what are the goals of refraction? (4)

1. clear vision
2. comfortable vision
3. rapid adaptaion
4. do no harm


what are the 4 phases of refraction divided into?

1. pre-presenation
2. starting points
3. refinement
4. end points


what is the most important tool of refraction?

clinical reasoning....
too bad its hte most useless class lol


what gives us hints as to the pts refractive error?

1. age
2. externals
3. case history
4. entrance tests: VA, CT
5. other tests: amp of acc, bruckner, direct ophthalmoscopy, keratometry


when does tearing occur?
when do headaches (HA) occur?
when does dist blur occur?

-hyperopia, astig
-myopia, hyperopia, astig, presby
-myopia, astig, sometimes if high hyp in adults w/ reduced acc


what happens if the pt says that tilting the gl makes things clearer?

change the cyl


the pt says "pulling the gl away from my face makes things clearer" what do yo udo

increase the plus


for CT, eso may be assiociated w / what? exo may be associate w/ what?

-eso w/ uncorrected hyperopia or an over-minused pt
-exo (esp at near) w/ uncorrected or undercorrected myopia


what might low amp be ass w/?


-can also be ass w/ primary anomalies of the acc system


what does bruckner test provide info on?

ref error
-hyp or myop?
media opacity

-abt all 3 types of amblyopia


when you have a clear view of the pts fundus (blur=0) w/ a direct oscope, the lens in the oscope head has neutralized the sum of 4 things:

1. pts ametropia (discrepancy)
2. pts acc
3. your ametropia (discrep)
4. your acc


what do you need to consider to predict VA

distance VA
near VA
pts age and epidomiology


for eggers chart, what can you predict refractive error for most accurately?

myopia and astig
-more difficult for hyperope bc of acc


for eggers chart, what do you predict the D to drop?
spherical component:
-from 20/20-20/50 =?
-20/70 = ?
20/100 =?

0.25D per line
1.25 D
1.50 D


for eggers chart, what do you predict the D to drop?
cylindrical component:

0.50D cyl per line

-values in minus cyl, apply to power but say nothing about axis


how does static retinoscopy asses the eye? what is it useful for?

asses the eye as if it is a passive optical device. it is useful for predicting the rx that will give clear vision


how does static retinoscopy asses sphere, cyl, power, cyl axis?

objective assessment


what can the quality of the static recinoscopy reflex give?

some info about corneal/integrity/shape and opacities along visual axis


how can static retinoscopy monitor accomodation?

can monitor acc indirectly by observing pupil size-measure when pupil at its largest to avoid over minusing


why can some argue that retinoscopy is the most important step in the exam process?

the essence of the exam process is to determine if decreased vision or visual function is due to ref error or bad eye/bad brain. you can't do that if you don't know if there is sig ref error


when can you prescribe based on static in pt?

that cannot give reliable subjective responses


for what type of pts is autorefraction reasonably accurate

esp for pt w/ limited acc or under cycoplegia (esp for cyl power and axis)


what does autorefraction do esp to young pts?

may over minus.
difficult to use in young pt or others who cant sit in device


what is keratometry not used for? what is it used for instead?

not generally used as starting point in a 'routine' refraction
-used to guide contact lens fitting
-used occ as an adjunct test when there is reason to do so (high cyl, irreg cyl, poor VA or refraction endpoint, scissor reflex on ret, diagnostic value, monitor for progression)


what is toricity

difference in corneal curvature in different meridians


when do k's help predict the cyl in the Rx-java's rule

if cornea has > 1.0D of 'toricity'