Varilux Lenses

Liberty

• Soft design
• Cheapest - not much of a jump up from bifs

Comfort

• Wider field without head movements
• Soft periphery
• Lens design changes w/increasing add power

Comfort Advans

• Has rear surface design so comfort design is maintained whatever the prescription (high cyl)

Ellipse

• Very wide distance vision area (140 degrees)
  
• Short progression length
• Good for small frames

Ellipse Advans

• Digitally surfaced for 145 degrees DV
• Near zone aligned so that it matches wearer's natural convergence

Physio

• Prettay good
• Lens reduces Coma so increased sharpness in DV
• Bigger area of clear DV compared to latest varis
• Greater visual and postural comfort
• Fitting height 17mm

Physio Short

• Better for smaller frames 155 degrees
• Minimum height 14mm

Physio f-360 degrees

• Personalised version for better near and intermediate (increased intermed width)

Ipseo

• bestest
• Personalised depending on wearer's head/eye movement ratio

CL Aftercare

Pre-Advice

• Come in wearing lenses
• Daily wear px come in PM so effects of daily lens wear can be seen, extended wear AM so effects of overnight wear can be seen
• Bring in solutions/case

Initial Discussion

• RFV, any problems? comfort & vision ok?
• Recent lens wearing history - max wearing time, how many days/week, how many hours in today?
• Probs handling lenses? Solution/care system ok?
• Any other eye problems?

Vision w/CLs

• Snellen/logMAR acuity monoc/binoc
• Ret w/trial frame, assess quality of reflex (this may indicate lens lifting off central or peripheral cornea
• Duochrome useful

Assessment of Fit (Soft)

• Comfort
• Vision
• Corneal Coverage
• Centration
• Movement on blink
• Lag on upgaze
• Push-up
• K Mires
• Any conj compression/buckling of lens edge

Assessment of Fit (RGP)

• White light - lens position wrt lids, primary & tertiary gaze, lens centration
• Blue light - flu patterns

Also look for

• lens/eye interactions eg lens edge near 3&9 o'clock staining
• Blinking pattern
• Head position (may indicate loose lens)
• Eye movements
• Palp Ap size - can reduce w/RGP, increase w/soft lens

Keratometry over lens

• Can assess fit, front surface wettability

Inspect Lenses

• Knick/tears
• Edge or body defects
• Deposits - protein, mucus, calcium, Fungi, Jelly Bumps, Rust Rings
• Do wettability/TBUT

Lenses Out

Get px to do it if poss. This allows you to see how they do it, whether they wash hands etc. If it's the first aftercare you should ask them to clean the lenses too to see how they're doing it. Correct any errors. Generally assess compliance.

Slit Lamp

White Light

• Perioc skin, eyebrows, upper and lower lids and lashes
• Bulbar conj
• Tear film
• Cornea
• Inf/sup palp conj

Blue w/Flu

• Corneal/conj staining
• TBUT
• Evert eyelids and examine papillae formation on tarsus

Also examine lenses off eye for damage/deposits. Do any necessary supplementary tests. Rose Bengal, ophthalmoscopy if not done for a while etc

Taking Action

• Same lenses w/different params - shift in Rx/alteration of fit
• New lenses of same general type - higher Dk/t
• New lens type - hydrogel to Si-H to improve physiology, RGP to soft to improve comfort
• Change lens wear modality - extended wear to daily wear
• Change replacement freq - monthly to daily?

Taking Action: Care Systems

• Completely change regimen - multipurpose to hydrogen peroxide
• Change version - 2 step to 1 step
• Alter protocol - add extra saline rinse?
• Change to avoid particular preservative
• Eliminate need for solutions - dailies

Final discussion with patient

• Reassurance concerning symptoms - eyes often feel dry at end of day
• Explain why lenses are being changed - more myopic
• Explain why solns being changed - different preservative to avoid red eyes
• Answer any other questions raised - px has heard about extended wear
• Recommended date of next visit - 6 mths?
  

Contact Lenses: Fit Assessment

RGP

• Let lens settle for a few minutes
• Can check centration, TD and movement under white light first - want good centration, staying within limbus, slow and smooth drop on blink, TD should allow ~1mm each side
• Then check flu pattern w/blue light - areas of dark blue = touch and brighter green = clearance with thicker tear film

Alignment Fit

• Even thickness of tears
• Good edge
• Hint of apical clearance
• Centres well
• Drops slowly & smoothly
• Stays within limbus in all dirs of gaze

Steep Fit

• Central pooling suggesting BOZR is less than k reading
• Inadequate edge
• Centres well
• Comfort often fine
• Drops slowly
• +ve liquid lens
• Could see bubble if very steep

Flat Fit

• Central touch and wide edge
• Discomfort
• Centres poorly and moves too much
• Drops quickly and in arc shape on push-up
• -ve liquid lens

Strategies

• Lid Attachment - common now that GP lenses are bigger. Has good comfort. The edge of the lens is in contact with the lid during blinking and in the primary position
• Lid attachment is the natural fit w/minus lenses and gives good tear exchange and comfort. It's more difficult with a plus lens (a -ve carrier is an option). Beware of corneal exposure and moulding
• Interpalpebral was more common when more people were using the smaller PMMA lenses. The centration is good and there's less flare. This strategy is useful if the patient has an irregular peripheral cornea as it only fits the regular central part.
• Alignment fit is used for modern lenses - multicurves, aspherics
• Apical clearance gives better centration if using a small lens.

Overrefraction

• A steep lens results in a positive tear lens so the minus power of the lens itself needs to increase
• A flat lens results in a negative tear lens so the plus power of the lens itself needs to increase

Edge Clearance

• This is the gap between the cornea and the lens edge
• Poor EC = stagnant tears, binding, staining, discomfort, hard to remove
• Good EC = easy removal of lens, good tear exchange, improves lens movement

Soft Lenses

• Can first check comfort and vision - is vision same as best spec Rx?
• If the lens blurs straight after blinking and then clears = flat fit
• If vision starts off clear and then blurs this suggests the lens is too steep
• Can do this subjectively or with keratometer
• Assess coverage (lens 1mm over each side ideally)
• Centration - if bit off to one side but all of cornea is still covered = acceptable. If cornea not covered can either fit a larger TD or smaller BOZR
• Good blink induced movement is 0.2-0.5mm upwards lens recovery straight after blink
• Excess blink induced movement is >0.5mm upwards recovery following blink - fit larger TD or smaller BOZR
• Inadequate = <0.2mm>
• Lag on upgaze - similar params to blink induced movement
• Push-up Test - lens should move w/slight resistance when pushed through lids
• If lens is totally free then larger TD or smaller BOZR
• If movement is sluggish then smaller TD or larger BOZR

Using K Mires

• STEEP - Mires immediately clear post-blink due to lid compression of lens, then mires blur as lens distorts
• FLAT - Mires are blurred immediately post-blink due to prismatic effect of lens movement, then mires clear and lens stabilises

Effect of TD/BOZR on Sag

• Greater BOZR = less sag, flatter fit, looser lens
• Greater TD = more sag, steeper fit, tighter lens

Misc

• Thinner lenses move less than thicker lenses
• Spun cast lenses move less than lathe cut/molded
  

LVA - Acuity Charts

Snellen

Advantages

• Well known, commonly used standard
• Very sensitive to blur and ref. error
• Good size, easy to move closer to px
• Has O and H for x-cyl

Disadvantages

• Unequal numbers of letters on each line - crowding not constant
• No relationship betw line size and number of letters
• Poor control of contour interaction
• Designed to measure normal acuity
• Scale intervals change at non-standard distances

Snellen @ Reduced Distance

• 6m letter @ 6m has MAR of 1'
• Px will be able to see a letter half the size when half the distance away

Bailey-Lovie LogMAR Chart

Adv

• Size/letter spacing equivalent throughout chart (5/row)
• 1.25x progression (0.1 log) each line
• All letters equally legible
• Constant crowding for all VA levels - easy to use at different test distances
• Final score takes into account all letter that have been read successfully (see later)

Disad

• not used as routine measure of VA
• Scoring/conversion not as easy
• No O for x-cyl
• Bit big and therefore hard to illuminate

Scoring

• The size diff between 2 lines on a logMAR chart is 0.1 log unit so 10 to the 0.1 = 1.25 so the size diff is equal to factor 1.25. 3 lines = approx doubling in VA
  
• Log score decreases with improving VA
• Each line = 0.1 log units and each letter is therefore 0.02
• Doesn't use viewing dist as part of notation. What you do is add 0.3 to the VA score every time the viewing distance is halved.

EG Px reads 0.8 line and 2 letters on line below so logMAR VA = 0.76
then Px reads 0.5 line and 2 letter on line below so logMAR = 0.5-0.04+0.3 = 0.76

• Reducing viewing dist by 1.25 requires a correction factor of 0.1
• so 6.0m to 4.8m = 0.1, 6.0m to 3.84m = 0.2 etc

Other charts include sheridan gardener, glasgow acuity and Kay's pics.

LVA "Routine"

Do current DVA/NVA with aid and specs, noting type of chart and distance used, light level, any head turn, record mon/bin VA. Worst eye first is good to keep morale up. Subjective refraction should use large steps/big x-cyl/reduced testing distance if required (px should be able to see 4 lines)

For distance

• Identify the px's visual task and estimate the required VA for it
• Measure best corrected VA and estimate mag required
• Calculate mag
• Dist generally for younger px, really need to be motivated
• Often not req as main problem is at near

For near

• Identify vis.task and estimate VA required
• Measure BCVA at 25cm with +4.00DS and then estimate mag
• If central field defect suspected check w/amsler - ecc. fix?
• Try predicted mag with simple magnifiers - higher add/hand/stand and use good illumination
• Modify mag if required, prescribe w/full instructions

Other stuff

• Binocularity - cover test
• Contrast sensitivity if req
• Fields, ophth, fundus photo, IOP

Advice/Follow-up

• Ideally 2-4 wks, may need to change LVAs
  

LVA Assessment - Intro

LVA is more of a problem solving exercise than the normal exam - not one unique outcome for px (ie 6/6). The main questions to ask is

What does the px want to do and is it going to be possible (expectations could be high or low)

• Many px may want a better pair of specs but this isn't possible, may be distressed/disillusioned
• Px must agree with what you want them to do - ie be happy with it

Speed has to be adjusted to fit the patient - an elderly px is going to need more time for subjective for example. Also avoid unnecessary tests. Initially general observation of the px can reveal a lot - bothered by light, physical infirmities, eccentric viewing, guided?

LV-centric equipment includes suitable test charts, real world items, 1.00D cross cyl, large aperture lenses, LVAs.

H&S is very important

• Pxs wants and needs (may not be the same thing)
• Questionnaire is useful for learning how they get on with specific tasks (how's watching tv? Do you sit close to it? etc)
• Specifics qs for distance, near, occupation, mobility, everyday tasks, hobbies, interests, different lighting conditions, onset of impairment, difference between eyes, believed caused, person who referred, ophthal - current and past treatment, when due back there, previous LV assessment, LVAs, live alone, hopes & expectations, registered etc etc etc

Psychological Aspects

Motivation is very important - they ain't going to get anywhere otherwise - the patient must be ready and willing to accept help.

Loss of vision can be assessed using a similar model to the one used w/bereavement

1. Denial/Shock - can't be happening
2. Grief - can't do anything now
3. Anger - it's not fair
4. Depression/Apathy - why bother
5. Acceptance - it's going to be ok

Px really needs to be at stage 5 before we can proceed. There's also a self-efficacy model which works best w/gradual vision loss. It's argued that early skill-orientated intervention can prevent loss of competence and foster a sense of personal control essential to successful rehabilitation.

Low Vision - UK Registration Process

Forms

• Scotland - BP 1, NI - A655, England/Wales - BD 8
• New forms introduced in England, should spread to all UK soon - LVI, RVI, CVI

The Letter of Visual Impairment (LVI) Form is given to the patient by the optom. This is the self-referral form geared towards the general public. It is supplied by social services and can allow access to social services if required. The patient contacts the council him/herself.

The Referral of VIP (RVI) form is issued by the local ophthalmology department by people like ophthalmic nurses, optoms, DOs, junior docs, orthoptists. Again this applies for access to social services.

The Certificate of VP (CVI) form is completed by a consultant ophthalmologist. It certifies the px as blind and again grants access to social services as well as passes the info on to the census office. NB Access to help is not dependent on registration. The thing is some people don't like to be 'certified blind' because of the social stigma but would still benefit from the help.

The registration process begins with the BP1 or CVI being sent to social services, the GP and the census office for research. Then a social worker goes out to visit the patient to discuss if they wish to be registered and see if they need a community care assessment in which they are assessed to determine their quality of life wrt everyday tasks/items in their house. The patient then can receive the benefits. NB if it's a kid they are registered blind at the age of four unless there's obviously no sight from the beginning of life.

Benefits of being registered

• Px can access central govt services - need to be registered for these
• Can also access local authority services, although some are available without registration. The services include the community care assessment, large button telephone, reading light, home help, meals on wheels etc
• Some services provided by voluntary organisations may be charged for if the patient isn't registered
• You also get financial help - 50% off your TV license if you're blind (not partially sighted!) and free BT directory enquiries.
• Transport is free in some areas and you can claim a disabled badge
• RNIB do talking books among other stuff
• DLA for people under 65 and attendance allowance for people over 65

Being registered is helpful for people in general - statistics both nationally and for each local area help to determine funding and resource allocation. The estimate is that up to 50% of px who are eligible aren't registered. The main disadvantage is the loss of self-esteem and hope.

The problems with the whole registration thing

• Optom/Opthal may not even tell px about it
• Usually done by ophthal as 'last resort'
• Poor comms betw professionals involved
• Long waiting times
• Not enough social workers & they may not be trained in dealing with LV patients