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Static Retinoscopy
Procedures 1 Spring 2010
| Question | Answer |
|---|---|
| What is a complimentary objective procedure to static retinoscopy? | Keratometry |
| What is an alternate objective procedure to static retinoscopy? | Autorefraction |
| What does static retinoscopy estimate? | The refractive error CORRECTION |
| What is the difference between static retinoscopy and dynamic retinoscopy? | Static is done with patient accommodation at rest. Dynamic is done with patient accommodation active |
| With which patients is static retinoscopy particularly useful? | infants, unreliable & uncooperative patients (poor subjctve repsonders) |
| What is a secondary feature of static retinoscopy? | It allows for the detection of corneal aberrations & opacities of ocular media. |
| Why does static retinoscopy qualify as an "art" | Docs must subjectively interpret the reflex to arrive at objective measurements |
| What do the power of the lenses needed to produce a neutral reflex represent? | The refractive error correction (NOT the error itself) |
| What type of motion is observed in static retinoscopy when examining a myope? Where is this patient's farpoint? | In a myope, rays leaving the eye are converging. The examiner will see against motion as the farpoint is behind you at some real distance closer than infinity |
| What type of motion is observed in static retinoscopy when examining a hyperope? (assume you are using a working lens) Where is this patient's farpoint? | In hyperopia, light rays leaving the eye are diverging. the examiner will see with motion as the farpoint is in front of you at some virtual location |
| Assuming you are using a working lens, what type of motion is observed in static retinoscopy when examining an emmetrope? where is this patient's farpoint? | In an emmy, light rays leaving the eye are plano. The examniner will see neutrality as the farpoint is on the plane of the scope (when using the working lens) |
| In regards to eye power and axial length, what would cause a patient to be myopic? | 1.too much plus power 2.too long of axial length in both cases, image is in vitreous & retina is conjugate to some real pt other than infinity. |
| In regards to eye power and axial length, what would cause a patient to be hyperopic? | 1.not enough + power 2.short axial length in both cases, image pt is behind retina & the retina is conjugate to some virtual pt. |
| Refractive error increases as the distance of the farpoint from infinity _________ | increases. This can be deceptive in that a hyperope who's image is very close to the back of the fovea actually has a greater refractive error than one whose farpoint is farther back in virtual space. |
| How do the farpoints of spherical eyes differ from those of astigmatic eyes? | Astigmats have two farpoints, while spherical eyes only have one. |
| For practical purposes, what distance qualifies for optical infinity? | any point beyond 6m |
| What is the standard working distance for static retinoscopy? what is the margin of error at this distance? | 1.66.7cm 2.for ever 5cm of error, measurements will be .12 off |
| What working lens would be used for the standard working distance? For a distance of 100cm? | 1. Working lens for standard would be +1.5D 2. Working lens for 100cm would be +1D |
| What are three characteristics observable while moving your streak during static ret that can help you determine neutrality? | 1.speed 2.width 3.brightness |
| What can be said of the speed of the reflex observed during static retinoscopy in regards to location of the farpoint? | 1.slower farther from farpoint (large refrctv errors) 2.faster as fp gets closer 3.reflx flashes when at neuralty 4.speed is more diffclt to analyze when evlting against motion |
| What can be said of the brightness of the reflex observed during static retinoscopy in regards to location of the farpoint? | 1.dullest when you're far from fp 2.brighter closer you get to fp 3.brightest when you are conjugate to fp 4.with motion brighter compared to against at equal distance |
| What can be said of the width of the reflex observed during static retinoscopy in regards to location of the farpoint? | 1.NARROWEST when far from fp 2.thicker as you approach fp 3.fills pupil when conjugate to fp (neutrality) 4.full pupil easier to interpt coming from with motion side |
| Describe the thickness, brightness and width of a reflex in which the far point is a great distance away from the examiner. | A reflex will be slow, dim and narrow when the far point is far away |
| Describe the thickness, brightness and width of a reflex in which the far point is close to the examiner. | A reflex will be bright, wide, and fast when the far point is near the examiner |
| Describe the appearance of a neutral reflex | 1.it has no apparent movement & appears to flash on/off in both mirror positions 2.is brightest & widest & fills the pupil completely |
| Is neutrality a single point? | No, neutrality occurs within a zone. |
| What two factors affect the dimensions of the neutrality zone? | 1.Pupil size; increasing zone with increasing pupil size 2.working distance; zone increases with increasing working distance |
| What are the two ways to bracket for neutrality? | 1.Optically bracket using lenses (plus should induce against, minus should induce with) 2.working distance( moving back should induce against, moving forward should induce with) |
| What are two good reasons to not use a working lens | 1.it increases reflections 2.it dulls the reflex 3.working lenses are for pansies |
| Define the gross retinoscopy finding | the result of the lens power needed to find neutrality scoping from your working distance |
| Define the net retinoscopy finding | the gross ret finding with the working distance mathematically accounted for |
| What type of retinoscopy finding is a true estimate of the objective refractive error correction? | The NET ret finding |
| What type of retinoscopy finding is a true estimate to the objective refractive error? | Trick question, NO ret finding estimate the error. NET ret estimates refractive error correction. |
| What is symmetric astigmatism? | when the sum of the minus cylinder axes is equal to or close to 180. (Generally if one eye is WTR, the other will also be WTR. OR; if one eye is ATR, other will also be ATR) |
| Which three phenomena can help refine the axis of astigmatism when the streak is rotated (not moved)? | 1.break(streak&reflex are not parlel) 2.width(narrowest&widest at the two princpl meridns) 3.birghtness(brightest when strk is on meridian) |
| Which phenomenon can help to refine the axis of astigmatism when the streak is moving? | Skew is observed while moving on either side of the correct meridian & is not present when moving the streak on the correct meridian. |
| What process of retinoscopy is aided by enhancing the streak? | Enhancing the streak aids in locating the principle meridians. NOT in trying to evaluate the type of motion. |
| When is enhancing the streak most useful? | Enhancing the streak is most useful for large cyls (grtr than 1D). |
| What does enhancing the streak do? | Adjusts the mirror of the retscope away from plano toward CONCAVE position. it makes the light brightest and most narrow. It makes evaluating the location of the principal meridian easier. |
| What must you always do prior to neutralizing a reflex | 1. you cannot accurately determine cyl power using incorrect princpl merids 2.you must first find the princpl merids by evaluating break, width, brightness and skew. |
| When astigmatism is present, which reflex is first neuralized? | Most with or least against. |
| Describe the orientation of the cylinder axis in relation to that of the retinoscope streak when you are done neutralizing your first meridian | Your streak assess the pwr of the merid that is sweeps. When using cyls, the axis must e set appropriately to put power in the meridian being scoped. Your streak and cylinder axis must always have the same orientation. |
| Define interpupillary distance | The distance b/t the centers of the pupils of the two eyes |
| Why is PD measured? | 1.to know the proper placement of the phoropter in front of the patient's eyes 2.at the end of the exam to specify the position of the optical centers of opthalmic lenses if prescribed. |
| What must be done to the PD measurement if it is taken via the traditional method? | 1mm must be SUBTRACTED |
| What is a more accurate method of PD measurement? Why is it more accurate? | 1.measur dstance b/t 2 corneal rflxes using a penlght and PD ruler 2. more accurate b/c patient does not look through exact center of pupil, but rather 0.5mm nasally |
| What will be the approximate difference b/t near and far PD measurments? | 4mm |
| Why is a distance fixation target used in static ret? | 1.to relax & stabilize accomdtn for patient 2.small target is not usfeul since the working distance lenses ensure a +1.5D fog for a working distance of 66.7cm |
| Why is a bichromed target used in static ret? | 1.bichrome filter reduces the amount of scattered light, thereby reducing the amount of reflection 2.allows patient with VA less than 20/400 to at least visualize a colored target |
| How long should static ret ideally take? | 2 to 3 minutes maximum *Ha ha ha |
| What are six possible sources of inaccurate ret findings | 1.incrct wrking distnce 2.scoping off axis 3.failr of patnt to fixate on target 4.failr to prprly neutrlz merids 5.failr to idntfy merids 6.failr to recgnize scissors motion |
| For which aspects of refractive correction is ret most and least accurate? | 1.most for cyl axis 2.next most for cyl pwr 3.least accrt for sphere pwr |
| For which aspects of refractive correction is subjective refraction most and least accurate? | 1.most accurate for sphere 2.next most for cyl power 3.least accrt for cyl axis |
Created by:
mm_coady