viva Flashcards
what precautions would you normally take before dilating a px prior to indirect ophthalmoscopy
H&S previous allergic reactions, 4D drug test drug dose date disposal, Does patient have any condition that could be aggravated by the mydriatic e.g. phenylephrine 10% should not be given to patients with severe cardiac disease, can cause systemic vasoconstriction
Does px report sxs of angle closure- severe unilateral eye pain, h/a, halos, nausea, vomiting
if px has used pilocarpine for treatment of glaucoma (commonly used for acute angle closure so dont), iris- clip IOL, translated crystalline lens or IOL, , marfans syndrome pxs could have a misalined crystalline lens.- look at iris colour - darker irides may need increased dose
For phenylepherine noted that patients on trycyclic antidepressants and MOA inhibitors could be at risk of a rise in blood pressure if drug instilled, and take care with patients with systemic hypertension
First check the va+ pupil reflexes, near muscle balance and accom once installed cant assess these
Measure openness of anterior chamber depth, van herricks, grade 2 or less,measure IOP
Check tonometry before so you can compare w after instillation- rise of more than 5 monitored
Consent- Discuss tasks px should avoid until drugs worn off eg driving, info what to do upon reaction- inform px’s of prodomal symptoms = haloes, ocular pain in dim lighting as acute closed angle glaucoma most likely when drug is wearing off = gap between iris and lens is smallest.
Advise them how long effects will last, unable to drive or cycle. photophobia
what would you do after assessing eyes of px you have dilated
Mesaure iop again- A rise of more than 5mmHg should be monitored until it returns to normal
Consider referral if difference over 5, monitor, high iop may indicate closed angle glaucoma
Measure openness of anterior chamber angle using van herricks, measure VA see if it has changed
Give px written material info about drug+ tell them signs and symptoms of adverse reactions to drug
what px should do if reaction, inform them of sxs- haloes, h/a, nausea, vomiting, severe unilat pain
ask px to wear sunglasses to reduce photophobia until effects have worn off, not to drive or operate heavy machinery, advise px they may experience blurry vision for couple of hours mydriasis lasts 8-10 hours but cyclooplegic effects last 2-4 hours.
apart from pxs with extremely narrow angles who else would you not dilate and why
Px using pilocarpine for treatment of glaucoma as causes miosis so cancels out dilation and its used to lower iops and dilating the pupils may temporarily increase iop
iris clip IOL- could rip iris and displace IOL and block angle=secondary glaucoma
translated crystalline lens/IOL or IOL that has moved eg mardans syndrome- could dislodge the lens
previous allergic reaction
pxs who have to operate heavy machinery or drive soon after dilation
somebody with genetic disorder eg marfans sydnrome who have ectopia lentis= displacement of lens which may move again causing blocked angle
for phenylephrine- not to use if px on tricyclic antidepressants, MAO inhibitors, hypertension as sympathomimetic could cause an increase in blood pressure as causes vasoconstriction.
Pxs with increased IOP- could cause angle closure
what could you use to dilate a px prior to examining them w indirect ophthalmoscopy
Tropicamide 0.5 percent to 1 percent depending on colour of iris, 1 percent with darker iris as pigment absorbs drug= (anti muscarinic that blocks receptors preventing contraction of sphincter muscle unopposed dilation. better as more rapid onset 20 mins and effects last less long.
Phenylephrine hydrochloride 2.5 or 10 percent, avoid 10 percent with young and elderly= sympathomimetic- dilates pupil by stimulating radial muscles of iris dilator pupillae to contract. acts directly on adrenoreceptors = slower onset, use both synergistically for maximal dilation
Cyclopentolate hydrochloride- anti muscarinic, not usually used just for dilation alone- relaxes accom
Atropine- muscarinic, blocks action of acetylcholine at muscarinic receptors- causes dilator muscles of iris to contract leading to dilation
Combination of drugs- tropicamide and phenylephrine- use lower concentrations
which drug gives maximal dilation
tropicamide or a combination of tropicamide with phenylephrine hcl
0.5 percent or 1.0 percent tropicamide in conjunction with 2.5 percent phenylephrine.
can also use topical anaesthetic to increase uptake of mydriasis.
what could you do to speed up the dilation process
use a combination of tropicamide with phenylephrine hcl
turn off or dim the room lights which cause pupils to dilate naturally and speed up dilation process
press firmly on lacrimal sac just medial to inner canthus to mimimise systemic absorption.
use anaesthetic before inserting dilation drops as this can reduce lacrimation and thus reduce drug washout and also this can increase mydriasis. = increases corneal permeability.
use a higher conc of drug
what are the 4ds with regard to safe use of ophthalmic drugs
drug (name of drug), dose (conc), date (expiry), disposal (toxic waste bins)
name the typical instruments used to examine the central 45 degrees of the retina
direct ophthalmoscope
indirect ophthalmoscope
welch allen or keeler wide angle or head mounted BIO
monocular indirect
opthalmoscopy with +20D lens
slit lamp bio with +20D lens
fundus contact lens
What are the advantages of direct ophthalmoscopy compared to indirect ophthalmoscopy?
Px does not need to be dilated
- Not as bright light source, therefore more px compliance
- More portable, does not require condensing lenses
- Less expensive
- Direct has higher mag, produces erect and upright image
- Easy to use
good for kids
indirect is inverted and alterally reversed
indirect requires additional lenses making it harder to achieve a clear image
Because the examiner’s eye is positioned relatively close to the patient’s eye, direct ophthalmoscopy provides a higher magnification view of the fundus. The close proximity allows for a more detailed examination of small structures in the retina.
What are the disadvantages of direct ophthalmoscopy compared to indirect ophthalmoscopy?
Direct gives us a decreased field of view indirect more
- Indirect does allow us to control the magnification by altering the power of the condensing lens and the power of the eye pieces.
- Ametropia has an effect on the size or quality of the image seen while using direct ophthalmoscope. Myopes = experience greater magnification and therefore less field of view. Hyperopes = experience less magnification and more field of view.
- Indirect can by pass media opacities due to the greater intensity of light while direct cannot. Poor image quality if px has lens or media opacities with direct.
- Indirect has a greater working distance than direct. Therefore patient comfort is more
- Direct ophthalmoscopy does not give stereoscopic view of fundus while binocular indirect does
astigmatism decreases quality of image in direct
working distance w direct is very close
Compare and contrast the 78D and 90D hand held slit-lamp indirect (Volk)
Higher the power the lower the mag and the greater the fov.
90D lens has a lower mag 0.75x than the 78D which has a mag of 0.93X.
90D has a greater fov though it has 94 degrees compared to the 78D’s 84 degrees.
78D provides a greater wd of 8.0mm whereas 90D is 6.0mm so 78D is more comfortable for the px.
the 78D is bigger 31mm and 90D is smaller 21.5mm. 90D is best for smaller pupils and 78D is best for general diagnostic lenses.
78D= higher mag, smaller fov can be held bit farther away. 90D lower mag but larger fov.
Name some of the more common hand held slit-lamp indirect (Volk) lenses available, and any specific advantages they have
+60D lens: better for examination of disc and macula and has greatest magnification.
+66D high definition view of disc and macula
- +78D lens: best for general diagnostic view.
- +90D lens: best for smaller pupils.
- Superfield NC is approx. +90D, good all rounded lens, mag is 0.71 , FOV 120 degrees, wd 6 to 6.5 mm and lens size is 26 mm.
- +81 aspheric lens view similar to the 78D lens in one way and a view similar to the +90 lens the other way
Name any attachments or accessories for Volk lenses, and their purpose
Yellow retina protector glass: minimizes risk of phototoxic retinal damage due to prolonged exposure to the focused beam. Also provides patient comfort.
- Lens holder/mount: provides stability and easier fundus observations to a novice user.
- Lid adapter: helps to keep the lids apart during observation and also keeps the lens at the correct wd
What are the advantages of hand-held slit-lamp ophthalmoscopy compared to direct ophthalmoscopy?
- stereoscopic view as examiner uses both eyes - easier to assess elevated areas
- large field of view
- can alter magnification by changing condensing lens used and less effected by the type of ametropia, astigmatism or lens or vitreous opacities.
- increased working distance
mechanical stability - less affected by presence of lens or vitreous opacities
additional lenses can be used providing a variety of diff views of fundus w all own advantages
contact lens fits are available w slit lamp, large mag and fov
What are the disadvantages of hand-held slit-lamp ophthalmoscopy compared to direct ophthalmoscopy?
Dilation is required, which causes near vision blur, discomfort and increases sensitivity to light and time consuming. Direct does not require dilation.
- The slit lamp uses a brighter light source, which increases discomfort and photophobia.
- Additional lenses increase reflections, making is more difficult to achieve a clear retinal image and no additional lenses are required for the direct method.
- Inverted and laterally reversed image - has to be interpreted
- More expensive.
- Not portable.
- Not good for people with spinal problems
What advantages does head-mounted BIO have over other indirect techniques?
- portable
- stereoscopic view
- can be used on all patients and on px’s lying down
- provides largest field of view of central and peripheral retina
greater working distance
can be used on all pxs unlike slit lamp methods eg kids or paralysed etc
What disadvantages does head-mounted BIO have over other indirect techniques?
difficult technique to do
hard for hijabis
- small magnification
- very small movement can distort image
bright light required= px discomfort
dilation is also needed
requires additional lenses, inverted and laterally reversed image compared to monocular indirect
can get diplopia due to bad setup
What is a scleral indenter, what is it used for, and which ophthalmoscopic technique would usually accompany its use?
- A scleral indenter is a thimble type instrument used to indent the sclera. It applies pressure to the sclera to view the far peripheral retina.
- This allows extreme peripheral views (i.e. ora serrata) and confirmation of holes/tears in the peripheral retina in especially px who are high myopes.
- Best used with head-mount indirect ophthalmoscopy. One hand is used to hold condensing lens, the other hand holds the scleral indenter. While the illumination source is mounted on the head
Useful for pxs with high myopia- more likely to suffer from tears in retina
Ora serrata is the strongest point of attachment but area where tears are most likely to occur
When would you examine the peripheral retina under dilation?`
If possible signs in retinal detachment and diabetic retinopathy
- In high myopes as there is a greater risk of retinal detachment.
- Flashes and floaters
- Traumatic eye or head injury suffered by the px
- Suspected tumour in periphery (locate size, type and location)
- Monitoring fundus changes in px who have glaucoma
optic disc changes so eg raised ONH with papilloedema, disc drusen etc
What optic disc features would you assess during ophthalmoscopy?
C:D ratio, colour and contour cup
- Disc margins, well defined?
- Neural retinal rim (NRR), whether ISNT rule applies
- Disc anomalies
- Peripapillary anomalies - area surrounding ONH
- depth of cup, deeper in myopes
Presence of any normal variations- scleral, myopic crescent, pigment cresent
What retinal vessel features would you assess during ophthalmoscopy?
- A/V ratio- relative thickness of arteries vs veins, normal is 2:3
- nipping -underlying vein appears pinched by arterial passing over- sign of high bp
crossing of blood vessels - tortuosity
Narrowings
dilated blood vessels
Also the broadening of arteriolar light reflex- sign of arteriosclerosis (change in appearance of these arterioles if more light reflecting off them may be due to thickening or hardening
What macula features would you assess during ophthalmoscopy?
- Foveal reflex (present or not- mainly in young px’s)
- Void of blood vessels.
- Healthy pigmentation.
- Raised or depressed areas
-drusen present-yellow deposits of lipids between bruch’s membrane & RPE- often associated with amd
see if there is a flat appearance
Look for abnormalities eg- Haemorrhages or drusen present, oedema, raised or depressed areas, exudates, abnormal pigmentation.
A 50 yr old, -8.00D myope attends your practice complaining of recent onset flashes of light, and a number of small black dots in her vision. What techniques would you perform, and what would you expect to find
High myope (-8D) is more likely to have retinal detachment.
Flashes are a sign of retinal detachment or tear.
Black dots are floaters and a sign of retinal detachment.
Diagnosis is that person is suffering from retinal detachment. Px at risk of retinal detachment and urgency is increased, could also e a pvd as px is older so also looking for weiss ring and shafers sign which would confirm rd. check va to give indication whether macula is intactc or not, perform tonometry low IOP= suspicion. Assess visual fields, anterior slit lamp assessent measure anterior chamber van herricks dilate look for shafers sign. View of peripheral fundus to check for retinal tears, holes, detachments or vitreous synersesis. Or- Head-mounted indirect ophthalmoscope would be used get a wider field of view in order to locate the detachment. If not present, then use a scleral indenter to see the extreme periphery for possible retinal detachment at the ora serrata. Expect to find rd or posterior vitreous detachment.
What is a Hruby lens? How does it differ from other lenses used for the same purpose?
non contact lens mounted on slit lamp for evaluating retina
It is a -55D plano concave lens (concave side towards patient)
- Used in conjunction with the slit lamp to provide to an erect and stereoscopic and virtual image- all other lenses provide an indirect method of viewing fundus this is a direct method
- Smaller FOV than a volk lens
- Technique is harder to master, difficult to obtain an image of the retina in the presence of media opacities, high px cooperation is needed with this technique.
affecred by media opacities, poor px fixation and has problems with glare
During direct ophthalmoscope, how do you determine if a media opacity is anterior, posterior, or at the plane of the pupil?
Have patient look slightly up or down…
-Anterior location: Patient looks up and opacity moves in the same direction as your opthalmoscope. Opacity is on cornea or anterior chamber. Opacity is closer to the light source than the pupil (closer in ret it goes with so same direction)
-Posterior location: Patient looks up and opacity moves the opposite direction to your movements with the opthalmoscope. within the red-reflex. Opacity is on posterior crystalline lens or vitreous. opacity is located behind pupil relative to light source so shadow moves in opp direction. (back w ret it gives u against)
-Plane location: Patient looks up and opacity remains stationary- If the opacity doesn’t seem to move much or at all when you move the ophthalmoscope, it may be at the plane of the pupil. This means the opacity is located at the same level as the pupil, so it do
Describe Van Herick’s grading system
van herricks grading system involves comparing the ratio of the corneal thickness to the openness of the angle. Assesses anterior chamber angle width. The grading system consists of numerical values from 0-4 which corresponds to a closed angle to a very open angle respectively. Qualitative form of measurement as you get a value. Grades angle between cornea and the iris.
Grade 4: the ratio of aqueous to cornea is 1: 1 OPEN
Grade 3: the ratio of aqueous to cornea is 1: 0.5 OPEN
Grade 2: the ratio of aqueous to cornea is 1: 0.25 NARROW (should be viewed by gonioscopy)
Grade 1: the ratio of aqueous to cornea is smaller than 1: <0.25 VERY NARROW (likely to close)
closed ratio= 0 angle: closed
What are the common ways of assessing anterior chamber depth?
5 points
Van Herick’s technique using slit lamp = compare thickness of anterior chamber to thickness of cornea. Gold standard. Subjective. Doesnt allow direct viewing
- Smith method using the slit lamp = horizontal beam and alter width until two just touch- numerical value quantative can actually compare the numbers.
- Penlight (pen torch) method = more shadow means more closed angle. nice open angle should see no shadow. qualitative, not the gold standard.
- Ultrasound using A-scan method = see peak for anterior cornea and posterior lens. not commonly performed.
- Gonioscopy = use goniolens/contact lens, need anaesthetics. need trained.
What is the pen-torch shadow or eclipse technique? How is it performed?
Does not allow direct viewing
Pen-torch shadow is a simple, gross technique.
- Shine pen-torch temporal to patient’s eye (viewing the shadow and its size).
- Larger shadow = smaller angle = closed anterior chamber angle = bad.
- Smaller shadow = larger angle = open anterior chamber angle = good.
What is Smith’s method? What is it used for? How is it performed?
7 points
It is a slit lamp procedure to estimate the depth of the anterior chamber = quantitive
- Use: This technique may elicit the first clinical sign of narrow angle or acute angle closure glaucoma in the symptomatic patient who presents acutely - can get actual measurement of anterior chamber depth. Doesnt allow direct viewing. less than 2mm is at risk of occlusion
- Illumination placed 60° temporally, observation straight ahead.
- View through right eyepiece for right eye (visa versa).
- Slit beam is 1-2 mm thick and horizontally positioned and focused on the cornea.
- Adjust slit beam so the two slits are just touching.
- Read measurement and multiply by 1.4 constant to get Anterior chamber depth (mm).
less than 2mm is at risk of occlusion
What is Gonioscopy? What equipment is required? Briefly describe how is it performed?
This is a technique that allows for accurate evaluation of the anterior chamber angle and detailed inspection of the structures within the anterior segment of the eye.
Gonioscopy allows direct viewing
Equipment required are slit lamp, goniolens (Goldmann 3 mirror), viscous coupling solution (fills gap btnw lens and cornea), and ocular lubricant e.g. viscotears for relief for dry eye and anaesthetic eg proxymetacaine/ benoxinate.
Procedure:
1. Add anesthetic drops to both eyes. (2 drops of benoxinate 0.4% and if allergic to this then use proxymetacaine 0.5%)
2. Align slit lamp in coaxial position.
Start at 10x magnification and increase when needed. Use low or medium light intensity.
3. Dim room lights.
4. Slit beam should be parallel piped (1-3 mm) and short so it doesn’t shine into and constrict pupil.
5. Place gonioscope square on patient’s eye (more comfortable for patient).
6. View superior and inferior sides with vertical slit beam.
7. View nasal and temporal sides with horizontal slit beam.
8. If Corneal-type lens then remove by releasing from contact with cornea. No pressure required.
9. If Scleral-type lens then tell patient to look at nose and blink. Do not pull lens off the eye.
10. Afterwards, examine corneal surface for any epithelial damage. staining
grading system = Kolker and Hetherington - 0= closed and 4=open but better to say which structures can be seen.
corneal type lens- These lenses are smaller and designed to rest directly on the cornea, the clear outer layer of the eye. Since corneal lenses rest directly on the cornea, a viscous coupling solution may be used to facilitate their insertion and improve comfort. This solution helps to lubricate the lens and the ocular surface, making it easier to place the lens on the eye.
Scleral lenses are larger and vault over the cornea, resting on the sclera, the white outer layer of the eye. They do not directly touch the cornea but instead create a fluid-filled vault between the lens and the cornea. Similarly, a viscous coupling solution may also be used for scleral lenses to facilitate insertion and improve comfort. However, since scleral lenses do not directly touch the cornea, the use of the solution may vary depending on individual preferences
A 60 yr old, +8D hyperopic lady attends your practice. She is complaining of pain around her eyes, blurred vision, haloes around lights and feeling nauseous. What test would you conduct, and what would you expect to find? 5 points
Hyperopes are at an increased risk of chronic glaucoma. These symptoms are very closely related to patient who suffers from closed angle glaucoma.
check the va (decrease in va likely)
-Check anterior chamber angle using Van Herrick’s. use slit lamp anterior examination.
provides clear 2d images used to grade anterior chamber angle to evaluate risk of glaucoma or acute angle closure. if narrow angle found px must be referred as sign of closed angle glaucoma. If suffering from glaucoma expect to find grade 2 or less.
or can do goniscopy/ smiths method.
- Check IOP with Tonometer: Goldmann is most accurate IOP above 21mmHg can indicate closed angle glaucoma or if difference of 5mmHg between both eyes, then we should be concerned
- Check ONH with Ophthalmoscopy: = increased cupping and an abnormal neuro-retinal rim (ex. not well-defined or decreased in size) plus increased CD ratio. for glaucoma. a fundoscopic examination can help rule out any concurrent posterior segment pathology, especially if there are additional visual disturbances or if the symptoms persist despite treatment.
- Check Visual field: can also be used to indicate any arcuate or nasal step scotomas which are again a sign of the presence of glaucoma.
What are the symptoms of a closed angle?
6 points
- Haloes
- Eye pain and pain within orbit
- Headaches
- Nausea
- Blurred vision
- red eye
decreased va
photophobia
pain in dim light conditions
Look at these mires. Describe what they show and what you would change to get the correct reading.
Image 1 = mires far apart
This shows that the mires are not aligned and there is not enough applanation induced on the eye. Therefore, one would increase the contact pressure to align the mires
- Image 2 = This shows that the mires are aligned and the IOP reading is accurate. No other actions need to be taken. perfect inner corners
- Image 3 - This shows that the mires are not aligned and that there is an increase of applanation induced on the eye. A decrease in pressure is required to bring the mires into alignment.
Outline the difference in the mechanism for the way in which the Pulsair and American Optical NCT measure pressure
both non contact
Pulsair applies air pressure to the eye and measures the point at which the cornea flattens. This method results in a decrease in corneal curvature until it is flattened.
It employs a transducer to measure the air pressure required to flatten the cornea.
AO NCT also applies air pressure to the eye but measures the time taken for applanation (the moment when the cornea’s curvature is neutralized).
It indirectly measures pressure by recording the time taken to achieve applanation.
