Subjective Refraction Overview and Pre-presentation Flashcards
why prescribe? 4
- improve VA
- improve binocular function
- prevent ambylopia
- improve general function
what are the goals of refraction? (4)
- clear vision
- comfortable vision
- rapid adaptaion
- do no harm
what are the 4 phases of refraction divided into?
- pre-presenation
- starting points
- refinement
- 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?
- age
- externals
- case history
- entrance tests: VA, CT
- 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/?
hyperopia
-can also be ass w/ primary anomalies of the acc system
what does bruckner test provide info on?
ref error -hyp or myop? -astig? -aniso? strabismus 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:
- pts ametropia (discrepancy)
- pts acc
- your ametropia (discrep)
- 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 =?
- 25D per line
- 25 D
- 50 D
for eggers chart, what do you predict the D to drop? cylindrical component: 20/20-20/50=? 20/70=? 20/100=?
- 50D cyl per line
- 50D
- 00D
-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
