Unit 5 CLS

Question 1

Lid Parallel Conjunctival Folds (LIPCOF)

Answer 1

Arises due to mechanical forces between lower lid and conjunctiva

Refit with lower content CL (as px will experience dryness) and lubricants
* Change lens type from SiHy to Hydrogel to aid with mechanical force (Hydrogels are
thinner, lower modulus) or reduce wear time

Question 2

when do you give a toric cls generally

Answer 2

> 0.75DC

when <0.75 = correct with sphere + half cyl

Question 3

prism ballast

Answer 3

o 1-1.5 prism BD – lens stabilised by lid force acting on prism induced thickness
o Increased thickness = possible discomfort on lower lid & reduced Dk/t
o E.g., Umere & bio infinity

Question 4

dynamic stabilisation

Answer 4

o Superior and inferior thin zones, interaction between both lids for stability
o Thin lens design (high comfort & no reduced Dk/t)
o E.g., acuvue oasys

Question 5

toric BVD calculations

Answer 5

 Feq = F / (1 – dF) where F = spectacle lens power, and d = BVD in metres (e.g. 0.012m)

Question 6

Simultaneous design (most MFs)

Answer 6

 Look through D & N rx at the same time
 Visual system learns to select the appropriate rx through the lens, depending on the object distance
 Concentric
o Can be centre near or centre distance
o Distance or near power is in the centre surrounded by concentric rings of N & D powers
 Aspheric
o Distance or near power is in centre, with a gradual transition to other powers as you move away from the centre (similar to varis)
o 1 day moist multifocal has an aspheric centre near design. The optical design varies to account for pupil size variation according to age and refractive error

Question 7

Segmented/translating multifocal

Answer 7

 Like bifocal/trifocal specs
 D power is in the centre & upper zones
 N power is in the lower portion of the lens
 Bottom lens edge is flattened to keep lens from rotating
 Visible line
 Px switches between rx’s by looking up & down as in bifs

Question 8

advantages of multifocals and disadvantages

Answer 8

 Compromised vision (any presbyopic CL is) – 6/7.5, N8
 No daily toric option
 15-day adjustment period
 Px may experience aberrations/flare if pupil size is larger than optic zone

Question 9

monovision

Answer 9

 1 eye is corrected for distance & the other for near
 Visual system alternates central suppression when alternating between distance & near targets
 Causes slight reduction in DVA & non-significant reduction in NVA
 Establish ocular dominance using +2.00 test
o Px looks 1 line above worst VA
o +2.00 is shown to RE then LE & px is asked which is more comfortable
o Dominant eye = eye not covered by +2.00
o If px can’t tell difference – reduce the blur (i.e., +1.00 instead)
 Dominant eye = distance correction as would normally prescribe for CLs (considering BVD / cyl)
 Non-dominant eye = near correction (distance correction would prescribe for this eye which incorporates px’s near add)

Question 10

what do different types of deposits look like on the lens

Answer 10

Protein
 Uneven haze on lens surface
 Very common with high water, ionic lenses (softs)
 Protein remover tablets

Lipid
 High water, non-ionic lenses (softs)
 New lens, change material, increase surfactant cleaning

Fungal growth
 Poor hygiene