OTM II MIDTERM

all the concepts for the midterm

Clinical uses for retinoscopy

objective measurement of refractive error, screening ocular disease, specialty retinoscopy

What are the 2 types of retinoscopy

static retinoscopy, dynamic retinoscopy

What type of test is retinoscopy?

objective method

How does retinoscopy work?

analyzes the optics of the patients eyes to determine the correction that the patient needs for their refractive error

How can the objective retinsocopy measurements of refractive error be used?

starting point for subjective refraction, used to prescribe where subjective refraction can’t be performed

How can retinoscopy be used to screen for ocular disease

keratoconus, media opacities

static retinoscopy: where does the eye focus and what does it determine

eye fixated at distance, **determines the refractive status**

dynamic retinoscopy: where does the eye focus and what does it determine

near with eye fixating, **determines accommodative function**

During retinoscopy what are we observing when we shine the streak of light back and forth?

red reflex within the pupil

What is the red reflex? What does it represent?

light reflected from the ELM, tells examiner where the patient’s far point is

What type of beams can the retinoscope produce? Which sleeve position is for each?

1. **d**ivergent ray - sleeve **d**own
2. convergent ray - sleep up

What does moving the sleeve of the retinoscope move?

the condensing lens up and down

What structures does the streak of light pass through during retinoscopy?

cornea, aqueous humor, crystalline lens, vitreous humor

What is the near triad?

1. accommodation
2. miosis
3. convergence

The ciliary muscle __ making the lens more __, and focal length is __

1. contracts
2. convex
3. shortened

What is the goal of retinoscopy when moving our streak of light?

neutrality

When you find neutrality in retinoscopy, what does that represent?

the patient’s far point is at infinity, the correct refractive error has been found!

What does with motion mean in retinoscopy? What lens would you use?

image is BEHIND retina

What does against motion mean in retinoscopy? What lens would you use?

image in FRONT retina, minus lens

What is the set up for retinoscopy?

* examiner wearing habitual RX
* pt NOT wearing habitual RX
* head must be positioned straight ahead

What is the target for retinoscopy?

Distance 20/400 letter with Red/Green screen (helps accommodation)

What is the lighting for retinoscopy?

dim room illumination

How do you explain retinoscopy to a patient? What do you instruct them to do?

* I am going to be getting an estimate of your glasses Rx by shining a light into your eyes
* Please look straight ahead at the big “E”, I am going to be shining a light across your eye a number of times. Please look at the “E” the entire time, dont look at me or my light, and please let me know if I ever get in your way

What 4 meridians do you need to AT LEAST test doing retinoscopy?

90 deg, 135 deg, 180 deg, 45 deg

What does a curved red reflex mean in retinoscopy?

very high astigmatism, corneal opacities, keratoconus

What does scissor reflex mean in retinoscopy?

corneal aberrations: very high cyl, corneal opacities, keratoconus

Is the degree of astigmatism related to a patient’s sphere power?

No

increased power of spherical & cylinder are increasingly associated with what?

ocular pathologies

about how many RXs are spherical?

\~ 1/3

What is WTR astigmatism

axis 180 (plus or minus 30)

What is ATR astigmatism

axis 90 (plus or minus 30)

simple astigmatism

one focal point on the retina, one off the retina

compound astimagtism

both focal points are **off** the retina

What type of astigmatism is this?

* compound hyperopic astigmatism
* both points are **behind retina**

What type of astigmatism is this?

* simple hyperopic astigmatism
* one point is **on** the retina, one point is **behind retina**

What type of astigmatism is this?

* mixed astigmatism
* focal points straddling the retina

What type of astigmatism is this?

* simple myopic astigmatism
* one **in** **front** of retina, one **on** **retina**

What type of astigmatism is this?

* compound myopic astigmatism
* both focal points are **in front** of retina

What type of test is retinoscopy? What type of test is refraction?

* objective
* subjective

What is the goal of subjective refraction?

improve patient’s vision to ***best*** ***corrected***

What are some reasons that patient’s will not be able to see 20/20?

* retinal disease
* media opacity
* amblyopia (refractive/strabismic)
* neurological issues

What objective and subjective findings should we take into account when creating the final prescription?

* patient visual complaints
* patient daily visual demands
* habitual rx
* visual acuity measurements

What are some examples of patients who we should not perform manifest refraction?

* very young kids
* non-verbal patients
* intellectual disabilities
* malingering patients

What are some myopic symptoms that you will hear before doing a refraction?

* blurred distance
* holding objects closer to see
* needing to squint
* pushes glasses back to the face

What are some hyperopic symptoms that you will hear before doing a refraction?

* adults = trouble reading
* younger = intermittent blur, esp when fatigued
* children/teens - may avoid up close work
* pull glasses down nose

What are some astigmatic symptoms that you will hear before doing a refraction?

* complaints present at both distance and near
* head tilting if oblique axis
* squinting
* ghosting/doubling of images
* higher astigmatism = poorer acuity

Reduced vision at **EITHER** distance or near

refractive error is **LIKELY** the culprit

Reduced vision at **BOTH** distance and near

refractive error **POSSIBLY** the culprit

For simple myopia, how much does each line of decreased VA equal?

around -0.25 DS

For compound myopia, how much does each line of decreased VA equal?

around -0.25 spherical equivalent

Uncorrected ATR astigmatism has __ impact on acuity that WTR astigmatism of the same amount

greater

What type of astigmatism has the highest impact on acuity?

oblique

Low amounts of astigmatism have __ impact on acuity

little

What two things does the estimation of refractive error for astigmats depend on?

1. amount of cyl
2. orientation of cyl

When you push a lens closer to the eye, what happens to the power?

more **minus** power (less plus)

What happens to the power when you move a lens away from the eye?

more **plus** power (less minus)

What is the JND for a patient?

Just noticeable difference, how much difference a patient needs to appreciate which lens it better

How can you estimate the JND for a patient?

divide the snellen denominator by 100

\
ie: 20/200

200/100 = 2.00D, JCC needed +/- 1.00D

What is the set up when performing a monocular subjective refraction?

* patient is not wearing habitual RX
* head must be positioned straight ahead
* forehead touching the forehead rest
* both eyes are **OPEN**
* correct PD

What is the target when performing a monocular subjective refraction?

Distance VA chart

What is the lighting for a monocular subjective refraction?

dim room lighting, stand lamp behind patient so they are not blinded

What are the steps of a monocular subjective refraction?

1. gross sphere power determination
2. cylinder axis refinement
3. cylinder power refinement


1. cylinder power search
4. sphere power refinement

What does fogging a patient mean and do?

it means to add plus, which relaxes the patients accommodation

When doing cyl axis refinement, how much do we move the axis when we are chasing the red dot? How much do we move backwards by when we hit reversal of the red dot?

low cyls (

What is the region between the horizontal and vertical focal lines in an astigmatic system?

interval of sturm

When images are in planes other than the horizontal and vertical focal lines, what do they form?

blur ellipses

Circle of least confusion

the closes thing to a point image on the retina for a point object in space

What is the dioptric midpoint between the horizontal and vertical focal lines?

Circle of least confusion

If a WTR eye is fogged sufficiently, where is the interval of sturm located?

forward, both focal lines will be located in front of the retina

Where does the unfog process place the CLC? What happens if we add -0.25D?

1. OLM of retina
2. moves the CLC closer to the macula

If shown this image, what lines would appear sharper for a WTR patient?

vertical

If shown this image, what lines would appear sharper for an ATR patient?

horizontal

For cylinder power, what happens when the white dot is chosen?

\-0.25D is SUBTRACTED from the cyl in the phoropter

For cylinder power, what happens when the red dot is chosen?

\-0.25D is ADDED to the cyl in the phoropter

Why do we do binocular balance?

* sometimes able to relax accommodation in one eye more than other
* pt may accept more PLUS in the binocular settings compared to monocular
* esp hyperopic patients
* need for this test decreases as patients age and become presbyopic

When do we perform binocular balance?

only perform when there is one line or less of BVA difference between the eyes

What techniques are there for performing binocular balance?

* prism dissociation
* alternate occlusion
* humphriss immediate contrast

What is the procedure for prism dissociation?

* have patient close eyes or sit back
* isolate a line at least 2 lines better than BVA
* partially fog patients vision by +0.50DS OU
* put 3BU and 3BD
* explain to pt that they will see 2 lines on top of each other
* make sure patient can read both sets of lines

How does the duochrome test work?

It utilizes difference in refraction or different wavelengths of light

\
the rays from the green filter are refracted to a greater extent, the rays from the red filter are refracted less

What is the goal of the monocular bichrome test?

To balance the red/green light so they are of equal distance from the retina

What is the procedure of the monocular duochrome test?

* choose isolated line of letters 20/30+
* Fog by +0.50D
* Occlude OS, ask the pt which is clearer (should report RED)
* decrease power by -0.25DS until pt reports equal or GREEN

How is binocular duochrome different than monocular duochrome?

prism is added to the test

Presbyopia

the slow, normal, naturally occurring age-related, irreversible reduction in maximal accommodation

When is presbyopia first generally reported?

between 40 and 45 years old

When is the peak onset of presbyopia

42-44 years

When MAY the peak onset of presbyopia occur

38-48 years

what are the 2 theories of presbyopia?

1. Donders-duane-fincham
2. Helmholtz-hess-gullstrand

Donders-duane-fincham

* muscle based theory
* ciliary muscle and none to the lens/lens capsule

Helmholtz-Hess-Gullstrand

* lens based theory
* lens capsule/lens and none to the ciliary muscle

3 biological factors causing presbyopia

1. elasticity of the lens capsule decreases
2. elasticity of the lens substance increases


1. lens sizes/volume increases progressively with age

other factors that cause presbyopia

* anterior shift of the equatorial fibers occurs because of increased lens growth
* equatorial zonular fibers decrease in number becoming less dense
* reduction of inward and forward movement of the entire ciliary muscle and ciliary muscle ring

Accommodation

* the process by means of which the optical system of the eye caries its focal length in response to visual stimuli

What are the steps of accommodation physiologically?

1. ciliary muscle contracts
2. pulls the ciliary muscle forward and inward
3. stretches the choroid and posterior zonules
4. the anterior zonular tension decreases and relax
5. lens capsule and lens become more spherical and overall power of the lens increases

Development of accommodation

* amplitude and accuracy of accommodation increases rapidly during the first 3 months of life
* accommodative responses are almost adult-like at 6 months
* amplitude of accommodation starts to decrease during school years

Amplitude of accommodation

the maximal accommodative level, or closest near focusing response, that can be produced with maximal voluntary effort in the fully corrected eye

Patient be able to accommodate _ times the accommodative demand to function without symptoms

2 times

ie: needs +2.50D to see, so needs +5.00D

Ways to *determine* __**tentative**__ ADD:

1. age-expected normals
2. plus build up
3. amplitude of accommodation equation
4. fused cross cylinder

Ways to *refine* tentative ADD

1. NRA/NPA
2. Range of clarity
3. individual patient demands

Ways to *finalize* tentative ADD

1. tentative near VA’s with the ADD
2. trial frame

Amplitude of accommodation equation

Tentative ADD = working distance (D) - 1/2 Amplitude (D)

\
ie: tentative ADD = 2.50D - 1/2(3.00D) = +1.00D