VISIT 4 Flashcards
what is aphakia?
no crystalline lens. possibly due to congenital cataract extraction or trauma or lens subluxation - marfans syndrome
rx for an aphakic child and corneal radius
o Average corneal radius of curvatures in a new born = 6.9mm (this flattens rapidly in first 6/12)
aphakic child has a spectacle rx of around +15.00 to +45.00DS in first years of life
aphakic child correction options
Aphakic spectacle wear
o Advantages
No risk of infection
Can be well tolerated
o Disadvantages
More challenging in unilateral cases
Expensive and specs can break easily
Cosmetic issues – lenticular lenses used
Heavy
Cause peripheral distortion
Aphakic CLs
o Advantages
No issues with weight
Easier for parents once inserted
Good cosmetically
o Disadvantages
Risk of infection if cleaning regimes are not followed
Initially more of a challenge for parents – need to learn I&R
what to prescribe for rx for aphakic children
o Aphakic children cannot accommodate
Infants tend to prefer looking at objects close to them
o Over correct by +2.00DS with CLs or specs until child is mobile
o Over correct by +1.00DS in toddlers
o Preschool kids, correct for distance with CLs and give bifocals with +3.00 add for near work
Some aphakic kids manage without a bifocal for near if in glasses due to the magnification effect, so assess each individual
contact lens choice for aphakic children
Initial choice would be a silicone hydrogel
Increased modulus, better stabilisation, reduced risk of corneal hypoxia
Can get 3/12 replacement and in powers up to +45.00DS (Ultravision CLPL) (45DS needed for 1month old)
Fitted the same as any other type of SCL – harder to assess in child
UV filer for cls
Scleral lenses are another option
Probably would not fit an RGP due to the possibility of the child rubbing the lens out of their eye (maybe for older pxs)
Scleral lens will not get dislodged – but may be harder to insert
High anisometropia / ametropia cls options
Ideal form of correction & may give better VA / reduce issue of aniseikonia as no magnification / minification effect
SCLs
o Use SiHy with a high Dk/t due to thick lens and use a large lens for stability.
o Ensure strict replacement schedule, particularly if EW.
o Mark ennovy for specialist lenses – weekly/monthly/3 monthly custom lenses
RGPs
o Large diameter for stability
o High plus RGPs have a centre of gravity which is further forward, so need to check fit in something close to px’s actual Rx, as just using a standard +3.00 fitting set will not give an accurate representation of how the high plus lens will sit
what is keratoconus
Non-inflammatory progressive ectasia of the cornea causing an irregular thinned corneal appearance; due to collagen disorder
Late teens/early twenties; bilateral but often asymmetric
risk factors, signs, presentation and tx of keratoconus
Risk factors: eye rubbing, atopy, higher incidence in Asians, familial link, systemic disorders
Presentation: blurred vision, frequent rx changes (myopia/astigmatism), glare
Signs: scissor reflex on ret, oil droplet reflex on ophthalmoscopy, Munson’s sign (cornea protruding forward), mod-high degrees of myopia/astigmatism, low CCT, irregular mires/topography, striae in posterior stroma, hydrops,
Tx; corneal cross-linking done as soon as possible (routine referral) – UV light to strengthen bonds between collagen fibres of cornea
Early stages keratoconus tx options
Early stages may be able to correct with softs e.g. kerasoft
o Front surface aspheric/aspheric toric
o Large back optic diameter to allow full drapage
o Adjustable periphery fits any corneal shape
RGPS also for early stages
Choose initial base curve midway between
average and steep K readings to obtain minimal apical touch and clearance.
Apical clearing – normal RGP fit
Apical bearing – optic zone of the lens touches the apex of the cone resulting in good vision
3 point touch RGP
3 point touch fitting technique: apical bearing & two other points of mid peripheral touch 180 degrees apart
distributes the weight for keratoconus, this is a technique used and tear film files the gaps, Rose K is a type of 3 point touch lens
piggy back CL
2 lenses on the one eye i.e. RGP is placed onto a SCL (silicone hydrogel)
Indications are irregular corneas where RGPs are not possible in keratoconus, post-graph and post-LASIK ectasia
Used to improve comfort and when RGP is unstable and pops out
hybrid cl
Rigid centre and soft skirt in the periphery
Indicated when RGP intolerance or inability to obtain an optimal RGP fitting, poor lens centring and reduced wearing time with RGPs
Lenses are fitted with no or minimal touch in the central cornea
Should see 0.25mm movement on blink
scleral cls keratonconus- when?
when cannot get optimal fit with RGP
mainly used on eyes where conventional soft lenses don’t work. Irregular astigmatism caused by:
Keratoconus, Pellucid marginal degeneration, post corneal trauma, post keratoplasty, post refractive surgery,
Exposure/Protective.
Full scleral (18-24mm), Mini scleral (15-18mm), Corneoscleral (13-15mm)
Rose K RGPs
smaller BOZDs to better fit the cone curvature
mini scleral cls
- Full scleral (18-24mm),
- Mini scleral (15-18mm),
Mini sclerals are designed to vault the cornea entirely
o No contact with the cornea means: you can fit irregular cornea, protect corneal surface, minimise scarring.
o Therefore, fitted by sag/depth rather than curvature
o The lens should clear the entire cornea and limbus. The full bearing and touch of the lens should be on the
sclera.
o Lenses are fitted from fitting set, initial lenses calculated based on topography and OCT or can be chosen
based on tables according to condition.
mini scleral cls - insertion, assessment, removal
- Insertion – Lens holder filled with saline solution, look down holding both lids and place lens directly on eye
- Assessment – Fitting characterised by 3 zones: central clearance, limbal clearance and scleral landing
- Removal – Massage in an inferior bubble, Scissor technique.
- Care Regime – Soft lens solutions (Not GP), non preserved saline, alcohol based
cleaner.
mini scleral lenses central clearance, limbal clearance and scleral landing
Central Clearance Zone ʹ lens needs to be clear by 300-400 microns, cannot just use NaFl staining, first check if iris and pupil is visible (if pupil and iris visible there is inadequate clearance). Compare thickness of lens (350microns) to thickness of tear lens there should be a 1:1 ratio cannot compare to cornea as in KC the cornea is thinner at the apex. Need to ensure clearance over entire cornea. Clearance needed at time of fit due to settling of lens into conjunctiva (sinks by approx. 100-150microns)
Limbal Clearance Zone ʹ Looking to see if the NaFl bleeds out from the centre to the conjunctiva (observe in white
light). Limbal clearance is essential to maintain corneal health. Inadequate clearance will lead to staining and
discomfort. If limbal touch increase limbal angle. Arc of limbal touch commonly seen in PP, if arc less than 180
degrees get the Px to look in all direction to see if it disappears. If it disappears lens is OK.
Scleral Landing Zone ʹ Sclera is supporting the entire weight on the lens, its landing needs to be smooth and not impinging any vessel trace vessels to check for this. If vessels blanch then mostly like being impinged
types of fitting for scleral lenses
Lens too Deep/Steep – central bubbles and pooling, scleral impingment
o Lens too Shallow/Flat – stand off edge, central corneal compression
o Peripheral standoff – pooling on edge and increased lens awareness, lids catching lens.
o Limbal clearance – once peripheral curve and sag is set – adjust limbal clearance by altering central curve only
– flatten gives greater clearance without changing the sag. Limbal touch causes adherence, staining, poor
comfort and lack of tear exchange. Excessive clearance may cause central staining and bubbles in limbal area.
o Fitting KC a lens which vaults the cornea and no heavy contact apex or at limbus. Sub optimal acuity may opt
for flatter fit but increased possibility of scarring (mini sclerals better)
Corneosclerals
aim to distribute weight and pressure evenly across the cornea and sclera, much closer fit. (thin
NaFl central, MP and limbal clearance and scleral landing). Lens marked with BC and sag (normal Px fit flattest k ,
KC Px 3 steepest BC)
fenestration
small hole which help lens settle easier, allows easier removal of lens (forms bubble
post surgical cls
Be aware of abnormal corneal shape, may require topography.
Corneal grafts tend to be slightly nasal, and so the CL will be centred slightly nasally.
Abnormal NaFl patterns.
May fit large diameter bandage CL on leaking bleb following trabeculectomy.
Post LASIK cls
May fit normal CL, try it & see - more likely to be successful if pre-LASIK Rx was fairly low. If Rx was more than -10.00DS then >100um of stroma was removed, and a reverse geometry lens may be required (as standard RGP will give central pooling).
other conditions that may require cosmetic cls
Aniridia:
* No iris – need a soft cosmetic lens to give the appearance of one
Phthisis bulbi:
* Shrunken and non-functional eye
* Soft cosmetic lens
Iris trauma
* Soft cosmetic lens
* Fit as you normally would any other SCL
Corneal trauma and sight loss
* Scleral, soft cosmetic and silicone SCL (bandage lens)
Post-LASIK surgery
* Scleral SCL, reverse geometry RGP ( for irregular cornea shapes, in this steeper edges and flatter centrally), RGP or SCL
how does ortho K work
works by a larger RGP lens (TD around 11mm) redistributing the epithelium due to the compression of wearing the lens overnight (at least 6 hours of wear)
* Will use topography to map out the cornea and get all the relevant measurements
* Base curve is flatter than the px’s cornea – central touch
coopervision misight scls
o Designed for myopia progression
o Work like concentric ringed multifocals – low levels of add e.g. +1.00 to prevent axial elongation
o Fit the exact same way as any other SCL
o May take some time to adapt to mild blur
o Again not 100% effective in slowing down the rate of myopia progression
Signs of ON dysfunction
Reduced VA (both distance and near)
* Severely Impaired colour vision
* RAPD
* VF Defect
* Impaired Contrast Sensitivity
what to do when px unsure about cataract referral
Explain that the visual outcome will not be worse if referral is delayed
Give an information leaflet for them to digest at their leisure & discuss with family
UV protection & smoking
Ensure px is aware they can return before recall if symptoms worsen; give name incase they decide they would like referred or have any questions
cataract explanation
Cataract explanation: cataracts are formed when the clear lens inside your eye becomes cloudy or misty. It’s a gradual process which generally happens as we get older. It is generally a natural part of the ageing process and anyone who lives a long life will go onto develop cataracts. Cataracts develop very slowly and will cause your vision to worsen over time. When this happens, we can send you to the hospital for a simple procedure to remove to cloudy lens and replace it with a new clear lens. The surgery is generally very successful and is a quick day procedure under local anaesthetic.
positioning tolerances
1mm PDs
1mm heights
2 degrees tilt from horizontal
Positioning of segments/fitting heights
Horizontal & vertical within 1mm
Tilt – no more than 2 degrees from horizontal
tolerance for 2.50DC
tolerance for 0.25DC
2
16
why do high plus have less FoV
The static FoV provided by a positive spectacle lens is less than the apparent FoV implied by the empty spectacle frame
This means hyperopes suffer from a decrease in FoV
There will be an area around the edge of a lens from which no light can enter the eye – a ring scotoma
Retinal image size myope vs hyperope cls and glasses
- When changing form specs to CLs, the retinal image size is larger in myopia but smaller in hypermetropia
spectacle magnification equation
SM= correct retinal image size/ uncorrected retinal image size
or
SM= power factor X Shape factor
Reasons for Fitting RGP
- Aphakia
- Cornea with high DC
- Keratoconus
- Post-Graft Surgery
- Better vision with high rx
- More durable - up to 1 yr wear
Health:
* High o2 permeability
* Doesn’t dry out tear film due to 0% water content
* Resistant to protein deposits
Flat fit - what over refraction will it have?
will have a negative tear film then it would have a plus over refraction
RGP ; TD measurement based on what
approx. 2mm smaller than HVID measurement
Fluro-Silicone Acrylates
– Fluorine monomer added to SA, lower surface charge so better
wetting and less deposits – although attracts lipids and mucus.
Susceptible to scratching and lens flexure
RGP equation when bigger cyls
BOZR = flat K – (flat k-steep k / 3)
pupil diameter RGPS
BOZD = area with Rx (periphery of lens is for stabilisation)
BOZD must be > pupil size in scotopic (dim light) to ensure pupil is smaller than BOZD in all lighting conditions
If pupil > BOZD = issue with flare / haloes around lights
High myopes may need larger BOZDs to avoid flare
over refraction - then what to do to the BOZR
0.25DS over Rx = 0.05 BOZR change
what do you do also when there has been an increase in the diameter
Increase in diameter by 0.5 = flatten BC by 0.05
o Increased diameter = increased sag
o Because cornea is aspheric, increasing diameter = steepening lens, therefore you need to flatten it to keep Rx same
bozd meaning
BOZD
The size of the optic on the back surface of the lens. It’s used to prevent flare from unwanted reflections.
retrobulbar neuritis
Demyelination may be caused by MS or be idiopathic, usually, age range 20-50 years,
75% patient’s female
Symptoms
Subacute monocular (usually) vision loss; typically progresses over less than 7 days
Some patients experience tiny white or coloured flashes/sparkles (phosphenes)
Pain on eye movement
Frontal H/A and tenderness of globe may be present
Signs
VA 6/18-6/60, rarely worse
Impaired colour vision / red desaturation
RAPD if unilateral
VF defect; central scotoma
Disc appearance normal or swollen, pale optic nerve & veins
management of optic neuritis
Urgent referral to HES – CMGs + GGC
Confirm diagnosis – MRI/CT
High dose IV steroids (prednisolone) within first week of symptoms onset = better prognosis
Systemic investigation to determine if underlying MS
classification of optic neuritis
Retrobulbar neuritis – normal appearance of the OD, at least initially
o Most common type in adults
o Frequently associated with MS
o Other causes: tuberculosis, syphilis, viral infections
Papillitis – disc hyperaemia/oedema, occasionally PP flame-shaped haemorrhages
o Most associated with diabetes
Neuroretinitis – papillitis and a macular scar
o 66% caused by cat scratch
PVD occur due to what?
PVDs occur due the contraction and constriction of the vitreous typically due to liquification of the vitreous gel and collagen fibre matrix with time, but can also happen as a result of trauma.
amidarone
used for hypertension
develop corneal microdeposit in a whorl like pattern within the corneal epithelium (Vortex Keratopathy) - increased glare and haloes.
if optic neuritis or aion - refer
Deposits are reversible with withdrawl.
can get anterior sub capsular opacities
Vigabatrin
treats epilepsy
1/3 of Px suffer a visual field defect with onset from 1
month to several years.
The defect is an asymptomatic pre-dominantly nasal concentric peripheral field loss sparing the macula and temporal area. Defect persist after
withdrawal of medication. Colour vision, contrast sensitivity and VA can be affected
Corticosteroids
Corticosteroids affect the crystalline lens when used over prolonged periods.
Steroid cause the formation of posterior sub-capsular cataracts.
These opacities typically bilateral and irreversible.
Px tend to report photophobia, reading problems and
difficulty with glare.
Steroid have the potential in susceptible individual to raise IOP and cause glaucomatous damage. Optic disc oedema is a rare
Hydroxychloroquine
is used to rheumatoid arthritis
Hydroxychloroquine is safer and rarely associated with toxicity.
Patient at risk of toxicity are those on treatment for five years or longer. Corneal deposits (vortex keratopathy) as
early as 3 weeks.
Chloroquine an induce in 1-2% of Px retinal and macular changes.
Premaculopathy: consists of early functional and structural changes prior to visible fundus signs – High res OCT/ FAF to assessment macula pigment density. Early maculopathy: VA 6/9-6/12 and subtle macular disturbance.
Progression of maculopathy: moderate to severe reduction in VA (6/36-6/60) bulls eye macular lesion – island of pigment surrounded by depigmented area of RPE atrophy
Tamoxifen
used to treat breast cancer or prophylactically in strong FH.
Tamoxifen is associated with bilateral superficial maculopathy (yellow/white crystal like
opacities surrounding macula. Crystalline deposits
It affects VA with associated CMO. Reversible if detected
early enough.
Mild to moderate tritanomalous CV defect and central scotomas within Amsler chart area.
Corneal deposits (vortex keratopathy).
what causes floppy iris syndrome
Tamsulosin
Sertraline / Amitriptyline
are anti-depressants
associated mydriasis
and thus blurred vision in particular difficulties with near vision.
dry eye
reporting adverse reactions
the yellow cards at the rear of the BNF or by downloading the Yellow Card from the MHRA website or submitting a report online.
A yellow card report should be completed
independently or if preferred in consultation with patient medical prescriber when its suspected than an OAR may
be related to a drug or combination of drugs.
Inform Px GP of course of action. Practitioners should be deterred even if it seems to be an isolated case or some details requested by the yellow card are not known.
yellow card scheme
Covers systemic adverse reactions to ocular medicines and ocular reactions to systemic medication
Online form filled about by members of the public of healthcare professionals
Particularly important for new drugs – marked by black triangle
The Medical Devices Reporting Form
Covers adverse incidents mainly relating to CLs and care products, including CL comfort drops
Prostaglandin analogues
lengthening of eyelashes, iris hyperpigmentation, redness and irritation, CMO, anterior uveitis (rare)
beta blockers
hyperaemia, irritation, dry eye and other systemic side effects
miotic pupil
Pilocarpine
ciliary muscle spasm, miotic pupils, VF constriction, brow ache, heart block and increased risk of retinal detachment
blood thinners - warfarin and apixaban
Subconjunctival, vitreous or retinal haemorrhages
loratadine
Dry eye
Reduced accommodation
Mydriasis
Alendronic acid
for Osteoporosis
Eye inflammation – scleritis and keratitis
Rarely optic neuritis
Diazepam
Lorazepam
for anxiety
Intermittent blurring
Photophobia
Mydriasis
maddox Rod
Objective: to quantify the distance phoria method:
1. SVD rx in trial frame
2. Place MR in front of RE
3. Grooves placed horizontally (measures horizontal phoria) = appear as a vertical
streak to the patient.
4. Dim room lights and switch on chart spotlight.
5. Px sees a spot light and a vertical red line.
o If only sees one target = suppression.
6. Is the vertical red line to the right, left or straight through the spot?
Þ With SOP the vertical red line appears R of spot (uncrossed images). Add
Base OUT prism until alignment.
Þ With XOP the vertical red line appears L of spot (crossed images). Add
Base IN prism until alignment.
Repeat with MR grooves vertical (measures vertical phoria) = horizontal streak to the
patient.
1. Is the horizontal red line above, below or straight through the spot?
2. With L/R the horizontal red line appears above spot.
3. Add Base DOWN prism to LE (or BU to RE) until alignment.
4. With R/L the horizontal red line appears below spot.
5. Add Base UP prism to LE (or BD to RE) until alignment.
maddox wing
Objective: quantifies the near phoria Method:
1. Habitual reading rx and near PD
2. Room lights on and use angle-poise lamp to shine close to towards the Maddox
wing targets (arrows, numbers)
3. Look through the horizontal eye slits.
4. Can you see the red and white arrows and numbers?
* If only sees one target = suppression
5. To measure horizontal phoria’s, check which number the white arrow points to
Þ SOP = odd numbers,
Þ XOP = even numbers
6. To measure vertical phoria’s, check which number the red arrow points to
Þ R/L = odd numbers,
Þ L/R = even numbers
Fixation disparity - horizontally - what to do?
If RE sees bottom marker and LE sees top marker:
o If top marker (LE) is to LHS and bottom marker (RE) is to RHS =
uncrossed à SOP deviation so use Base OUT.
o If top marker (LE) is to RHS and bottom marker (RE) is to LHS = crossed
XOP deviation so use Base IN.
Perceived image moves towards apex of the prism
Fixation disparity - vertically- what to do?
- Check each eye to see which strip they can see
- In this example LE sees line at right side, RE sees line at left side
- If line on RHS is higher à Correct with Base UP LE
- If line on RHS is lower à Correct with Base DOWN LE
- If only one marker is deviated, place prism in the affected eye
when to use cat stereograms
XOP conditions increase the positive relative convergence ʹ this is done by carrying out a near stereogram where the px fixates on a target in front of the stereogram while attempting to fuse the stereogram.
o SOP conditions increase the negative relative convergence ʹ this is done by carrying out a distance
stereogram where the px fixates on a target in distance while attempting to fuse stereogram at near.
modifying rx for phorias
Myopia and SOP ʹ least possible minus for clear distance vision
o Myopia and XOP ʹ Most minus but minimum over correction
o Hyperopia and SOP ʹ Max plus Rx without causing blur
o Hyperopia and XOP ʹ Consider partial correction
o Full Rx can be used in coordination of prism
Esophoric Conditions
o Divergence Weakness ʹ Most often due to uncorrected hyperopia, symptoms associated with distance vision unless the hyperopia is high, associated with prolonged use of the eyes and will be less or absent in the morning.
o If persists after refractive correction try physiological exercises, Prism if other treatments fail
o Convergence Excess ʹ Due to accommodative effort, uncorrected hyperopia, latent hyperopia, spasm of accommodation, psuedomyopia, close working distance
o Normal AC/A is 4:1 when over 6 will result in convergence excess, incipient presbyopia
o Symptoms ʹ Frontal headache, ocular fatigue, distance focus problem after near work
o Unreliable refraction results indicate latent hyperopia as does lower subjective vs retinoscopy
Management – Eye exercises – development of PRA – use negative sphere while patient maintain clear SV, relieving prism not appropriate unless AC/A ratio is low.
convergence weakness
o Hypertonicity of abductors, uncorrected myopia may build false AC relationship
o Symptoms ʹ Less marked in XOP (associated with suppression), Frontal headache with prolonged use of eyes, ocular fatigue, sometimes intermittent diplopia particular for near vision
o Management ʹ Improve poor working conditions, adequate illumination and contrast, general health, medication
o Full myopic or absolute hyperopic correction will assist in compensation
o In hyperopic cases, full Rx may make symptoms worse – partial correction, Full Rx with prisms or exercises, partial Rx with prisms or exercises, Full Rx with negative add
o Eye exercises – develop convergent fusional reserves, develop appreciation of physiological diplopia, treat any suppression
o Relieving Prism – Simple and effective, aligning prism or CT prism, subjective improvement in near vision, worse when prism removed.
o Referral – degree of XOP has to be larger than expected due to accuracy of surgery
divergence weakness XOP
o Divergence Excess ʹ Large degree of exophoria at distance which may break into a divergent strabismus, near vision XOP is at least 7pd and is compensated
o Symptoms ʹ intermittent diplopia – family may notice divergence of one eye in bright lights, poor healthy,alcohol
o Management ʹ Over minus for distance – bifocal to prevent over convergence at near, short term solution white convergent fusional reserves being built up
negative fusional reserves for which phoria
Esophoria = negative fusional reserves should be measured = BI prism
when would a balance lens be given
o Been given previously
o Cosmetically unacceptable
o Very large difference in Rx = aniseikonia = diplopia
sphere plus half cyl
when can bifocals be used as management for BV
o Convergence excess SOT = additional plus @ near
o Convergence insufficiency = additional minus @ near
o Divergence excess XOP = minus @ distance
