Toric

Question 1

what are the different types of astigmatism

Answer 1

1) regular the 2 principle meridians 90 deg from each other

irregular- 2 principle merit not 90 deg from each other

Question 2

WTR astig

Answer 2

1) wtr refractive error is greater in the vertical meridian

flattest along horizontal meridian

refractive cyl axis 0-30 deg 150-180 deg

Question 3

ATR ast

Answer 3

ate refractive error greater in horizontal meridian
flattest along vertical meridian

refractive cyl axis is 60-120 deg

Question 4

oblique astigmate

Answer 4

2 principle meridians are more than 30 deg from horizontal or vertical

Question 5

residual astigmatism

Answer 5

RA= OA-CA

when spherical RGP placed on cornea
it will correct the corneal astigmatism, but not lenticular astigmatism.

this lenticular astigmatism known as RA

Question 6

Induced astigmatism

Answer 6

IA created hen a topic back surface is placed on a toric cornea.

characterised by the differing refractive indices of the contact lens and the tear film beneath.

Question 7

correcting CA

Answer 7

<0.75DC - spherical soft /gp
>0.75<2.50DC - soft topic , GP (toric periphery, back surface topic , front surface topic

> 2.50dc - back surface topic/bitoric

Question 8

what is the prism ballast design

Answer 8

thicker profile towards the base BD prism- tends to move less vertically

+ve
good stabilisation

-ve
better for oblique axis & weaker lid tension but less comfort due to thickness & less O2

INCREASED THIICKNESS IN THE CENTRE AND INFERIOR EDGE OF LENS - REDUCES OXYGEN TRANSMISIBILITY TOWARDS BOTTOM PART OF LENS
check for novas at bottom of lens

upper lid exerts pressure on the thinner lens edge causing the thicker edge to drop down and move away from the upper lid with each blink

prism balast in one eye and not the other can create vertical prism

Question 9

how does the prism ballast lens work

Answer 9

Works on the watermelon seed principle - thin part of the lens goes under the upper lid which squeezes the thicker part of the lens toward the lower lid (the squeeze pressure imparted by the upper lid impels the thickest part of the lens away)

Question 10

what is peri balast

Answer 10

lid hold onto the thinnest part of the lens
pushing the ticker part down with each blink

results in decreased centre thickness which helps improve the optical quality of the lens

bas at the bottom part of the lies

Question 11

what is dynamic stabilisation

Answer 11

1) lens thin at the top and bottom - thicker in the middle
the thinner superior and inferior edges interact with the upper and lower lid and stabilise during the blink

+ve 0 thickness can be minimised improving comfort and o2 transmissibility
different options with this design

markings at either 6 or 12
or 3+9

Question 12

what is the goal of stabilisation

Answer 12

minimise the lens rotation of the eye in order to provide the stable correction of the astigmatism and minimise visual blur

Question 13

why use toric rgp

Answer 13

to improve physical fitting
to improve physiological status
to improve vision

Question 14

what are the 3 types of toric reps

Answer 14

back surface
front surface
bitoric

Question 15

BACK SURFACE TORIC

Answer 15

back surface of the lens would align with the flattest and steepest corneal radii

when- Conner is regular and if the CA is >2.50ds

why back surface stabilised lens and to centre better

Question 16

front surface toric

Answer 16

corrects lenticular astigmatism
if the corneal shape doesn’t require a back surface toric lens and if the astigmatism IR >0.75dx

why front toric lenses compensated an OR for wearers with astigmatism

Question 17

bitoric

Answer 17

astigmatism >3.00dc or if differnec in corneal and spectacle astigmatism

Question 18

Linarial toric/coopervision myday

Answer 18

features:
stenfilcon A / 54%/sihy
UV blocker
Dk/t (at -3.00D)
Thickness 0.10mm (at -3.00D)
Base curve 8.6mm
Diameter 14.5
peribalast

Cylinder power -0.75, -1.25, -1.75, -2.25DC
Axis Axes 10˚ to 180˚ (10˚ steps)

advantages
The largest number of prescription range for any daily toric
Offers around-the-clock axes across all cylinder powers and a core range from +8.00 to -10.00DS‡

Uniform horizontal ISO thickness for improved stability
contact lens has a consistent thickness across its horizontal plane, adhering to international standards

ensures stability on the eye, ensuring it maintains its correct orientation= better/more reliable vision correction

Question 19

Umere toric

Answer 19

coopervision clariti 1 day
prism ballast

somofilcon A / 56%
UV blocker
Oxygen transmissibility 57 Dk/t (at -3.00D)
Thickness 0.105mm (@ -3.00DS)
8/6/14.3

-0.75, -1.25, -1.75DC -2.25DC
Smooth, gentle lid/lens interaction leading to a consistently stable fit
Back surface aspheric peripheral zones to optimise lens stability
High oxygen transmissibility
Naturally wettable. Excellent rotational stability and orientation 2
Sustained high water content for excellent all-day comfort

UV blocking †
Easy to handle. 5

Question 20

what are names of reusable topics and what lens design do they use

Answer 20

opt eyes toric/opteyes toric XR- bioinfity
+ uvicia- periballast

acuvue oasis astigmatism- dynamic

proclear prism ballast

Question 21

fitting adaptation laars gaas