what is the role of dispensing optician?
.they give advice on frames and lenses and measurements relating to dispensing spectacles
.they can also sepcialise in low vision and contact lenses
what must a dispensing optician have?
ABDO qualification plus a registration with GOC
what are the different types of lenses?
.single vision
.bifocal- 2 prescription in one lens
.trifocal-3 prescription in one lens
.progressive power lenses e.g.VARI FOCAL which is no lines on lens
.occupational lenses- type of varifocal e.g for computer
what are the types of RX?
Rx is either spherical - correct ametropia (myopia and hypermetropia)
Rx could also be cylindrical - correct astigmatism( includes power of cylinder and axis)
Rx could also be used to correct both
what are three types of vision prescriptions?
.DV - distance
.IV - intermediate e.g mid range of site e.g artist or music notes
.NV- near- tablet and books
how is a prescription usually written?
sph/cyl X axis
what is the axis used to correct?
the axis is used to correct astigmatism
how does transposition work?
.add SPH+CYL to obtain new sph
.change sign of CYL
.add 90 to original axis
what is the transposition of -1.25/-2.50 x 40 ?
-3.75/+2.50 x 130
what are the combination of bifocal prescription?
. DV and NV
. DV and IV
.IV and NV
what is the advantage of bifocal?
allows you to see both reading and distance at same time.
what is the disadvantage of bifocal?
.change is prescription from distance to reading can cause blur
. stiff neck
how does trifocal work?
contains all three distances
.DV , IV , NV
how does progressive power lens or varifocals work?
.contains all three distances
.distance vision is in the upper hemisphere of lens
.there is a small stabilised zone for near vision at the lower edge of lens
.connecting these two areas is a narrow channel with a gradually increasing plus power called progression zone
by lens changing the power has elements of distortion
what is the disadvantage of varifocals?
blur/stiff neck
what is asthenopia?
eye pain or ocular fatigue
what are some types asthenopia ?
.sore eyes
.tired eyes
.eyes pull
.visual discomfort
what are some issues that arise during visual display terminals? e.g. looking at computer
. blink rate reduces
.eyes tend to get dry
.reduced eyelid coverage
how should a workstation setup look like?
.adjustable blinds
.screen at 90 degs to window
.screen below eye level
.concealed lighting
what are some types of lens coating?
. hard coat . MAR . tints . UV . photochromic . polarised
what is hard coat?
abrasion resistant coat
what is the advantages of hard coat?
. reduces scratches
what is the disadvantage of hard coat?
. cost
.doesn’t stop all scratches
what is MAR coat?
.anti reflection coat
.reduces reflection thus better vision
what are the advantages of MAR coat?
. can help eyestrain and fatigue by reducing unwanted glare/reflection
. good for night driving
. cosmetically better
what are the disadvantages of MAR coat?
. can look dirtier and smudgier
what are the advantages of tints?
. reduces squinting in bright light
what are the disadvantages of tints?
. can reduce VA
. can change the colour of things
what is the advantage of blue light?
. may improve visual comfort
good for computer use
what are the disadvantages of blue light?
. can look dirty
. can look quite blue on lens
.can make lenses look yellow
.shorter wave length more damage to the eye
what is the function of UV coat?
blocks UV light
what are the advantages of UV ?
. protection from un wanted UV radiation
.reduce risk of cataract
. helps prevent UV damage to skin around the eye
what are the disadvantages of UV?
can make lens look yellow
what is a photochromic light?
. a lens that adapts from light to dark and vice versa
what is the advantage of photochromic light?
. gives patient one pair of glasses
what is the disadvantage of photochromic light?
. don’t work in cars
. slow to change back
what is the advantage of polarised light?
.can reduce unwanted glare/reflection on wet surfaces
what are the disadvantages of polarised light?
.changes the way light is reflected off pavements so makes image look unusual
. can stop you seeing digital screens if light is polarised in a certain way
what is inter-pupillary distance?
. distance between the centre of the pupils
how to measure inter-pupillary distance?
- make sure your eyes are on the same level as patient
- make sure the ruler is held steady on patients forehead
- close right eye and direct patient to look into your open left eye
- zero the ruler at centre of pupil or edge of pupil or edge of iris
- read PD off the scale of the ruler
what is average male PD?
64
what is average female PD?
62
how to measure monocular pupillary distance?
.measure left eye to middle of nose and then middle of nose to right eye
when to measure mono PD?
. when one eye is closer to nose than the other
. high index lens- too high prescription so you have to thin the lens
.progressive lenses- varifocal lenses
. aspheric lenses- coating that comes with lenses
What do we write out for the order for single vision lenses for intermediate prescription?
IV= Dv Rx +IV add to spherical part
-axis and cyl stay the same
Healthy eye with plenty of accomodation?
Dv, Iv and Nv is clear
HCL?
Bottom of rim to centre of pupil (measure)
What do we write out for the order for single vision lenses for near/reading prescription?
NV= Dv Rx + NV add to spherical partt