GP multifocals

what are the designs of simultaneous GP MF lenses (2)

• concentric or aspheric

• concentric - mainly CD

• aspheric - front or back surfaces - can be CD/CN

what are the advantages of simultaneous lenses (8)

◦Minimal gaze dependence - px can read in every POG not only when looking down

◦PPL effect - allows for intermediate vision - comfy for computer users

◦Comfort equal to single vision GP CLs

◦3-4 mm pupils or greater are more suitable

◦Early to mid-presbyopes (adds 1.00 to 2.50 D)

◦Normal stereopsis

◦No image jump - no line in the lens

Easier to fit than alternating GP CL designs

what are the disadvantages of simultaneous lenses (7)

◦Difficult to achieve high adds (>2.50 D) - depending on e value of the eye

◦Top up spectacles or modified monovision may be needed for these px therefore

◦Compromised VA with some contrast loss

◦Can be difficult to attain required centration

◦BS aspherics - majority of designs limited to this

◦spectacle blur in higher adds - can be induced

◦not available in back-surface toric designs

explain troubleshooting of a low riding position simultaneous CL (4)

• Avoid steep fit - increase lens diameter

• change edge design by adding a –ve carrier on high-plus CLs

• Thickness control - ↓ bulk - to increase lid attachment

• Avoid high WTR astigmatism (>2.50DCyl)

explain troubleshooting of a high riding position simultaneous CL (5)

• Ensure fit not too flat

• Avoid excessive lid attachment - optimise thickness

• ↓ lens diameter (TD) - if narrow palpebral  aperture

• Avoid WTR >2.50 D

• Consider  different lens design or prism ballast - to maintain centration of lens

explain troubleshooting of a laterally decenterd simultaneous CL (2)

◦Avoid moderate ATR astig (>1.50 DCyl)

◦­ increase lens diameter - TD

explain what to do in the case of a px having good centration but poor distance vision (4)

◦Over-refract & give minimum extra minus

◦↓ add in dominant eye

◦Change lens in dominant eye to single vision (enhanced monovision)

◦­increase zone over which add functions (concentric designs/or by width) - only if patient has large pupils (>5 mm)

explain what to do in the case of a px having good centration but poor near vision (3)

•­Increase the add in dominant eye

•Over-refract &, if required add is >1.75 in total, work onto front surface of CL on non-dominant eye

•↓ zone over which add functions (concentric designs) - only if patient has small pupils (<3 mm)

what are the 2 designs of translating GP lenses (3)

• long line segment - tangent streak - achieved by truncation and prism ballast

• triangle shaped segment - presbylite - NO truncation, achieved by prism ballast

• both are available with toric BS

what are the advantages of translating GP bifocal lenses (4)

◦Excellent VA distance & near - as segments specific for distance/near

◦Normal stereopsis

◦Good contrast

◦Custom CLs offer: wide parameter range / choice of materials / high adds available

what are the disadvantages of translating GP bifocal lenses (3)

◦Stabilisation necessary (prism ballast/truncated) - so reading portion is in line with where it needs to be

◦Require to be ‘very’ mobile on eye - not very comfortable

◦Bifocal (unless made into trifocal) - gaze-dependent (can’t read in every POG) and intermediate vision poor/lacking

when fitting translating GP CLs what are we looking for (5)

• Inferior centration / rapid post-blink recovery - Prism Ballast / thin upper edge

• Segment line - on inferior pupil margin – covering 20% max

• Small pupils best to avoid flare

• Minimum 2 mm translation - lower lid support - truncation where required - avoid truncation if possible due to comfort – irregular edge of lens interferes with comfort on lower lid

• Keep prism as low as possible - for binocular vision and comfort – due to thickness in inferior lid margin

explain how we assess the rotation of translating GP lenses (3)

• If marks rotate inwards (nasal) - if < 30 ^o – OK – as when we read eyes come together nasally

• if ≥ 30 ^o – Compensate

• Rotate temporal compensate - be wary of making very large compensations

how do we assess the fit of the segment on the eye (5)

• via ophthalmoscopy - see red reflex - ask patient to blink

• Check speed of return if < 1 sec, perfect / if > 1 sec, improve fit

• improve fit by - making BC steeper / flatter – depending if too much movement/too tight - if too tight FLATTEN BC / if too much movement - STEEPEN BC - flattening is inc BC and steepening is decreasing BC

• if segment Position < 1/3 mm in pupil sector - proceed to over-refraction

• if segment Position > 1/3 mm in pupil sector - ↓ lens diameter

how do we decide which px are better suited to simultaneous lenses (4)

◦Patients that require near vision in the straight ahead gaze

◦Can accommodate any reading position - doing a lot of lateral reading - not always looking down

◦Early to moderate presbyopes

◦Intermediate task demands - computer work, playing a musical instrument, sewing machine etc.

how do we decide which px are better suited to translating lenses (7)

◦Read in normal position (slightly inferior)

◦Require excellent distance vision

◦Patent with higher adds

◦Larger pupils and very small pupils - translating can bi sect any pupil size whereas in simultaneous it is pupil dependent - cannot fit v. large/small - would miss out on some portion of reading addition

◦Lower lid within 1mm of the limbus - ectropion, entropion

◦Fair sized palpebral aperture

-require a sclera that is flatter than cornea - or lens would not be able to translate