11: options other than glasses

spectacles

most commonly prescribed

single vision

bifocal - near at bottom, distance at the top

trifocal - distance at top, intermediate and near at bottom

varifocal/progressive - distance, intermediate and near, smooth transition bewteen int and near, but can get distortion around edges

degressive/office/occupation - intermediate and reading only

what ways lenses can be adjusted by

tinted - darker at top, lighter at bottom

polarised - removes reflections

mirrored - mirror surface where people cant see your eyes

transitions - reactive to light, slowly gets darker from clear to dark when exposed to UV. work better when cold

prism - bends light all in one direction

advantages of specs

cheaper

reusable

customisable and fashionable

can include therapeutic treatment

minimally invasive/ risk of infection

potential for AR or VR technology and digital tools

disadvantages of specs

cant fit all faces

custom specs are expensive

can be broken

not subtle, can cause sensitivity

can get lost

types of contact lenses

soft contact lenses

rigid permeable contact lenses

miscellaneous speciality contact lenses

soft contact lenses

low oxygen transmission

thin flexible lenses made from hydrogel and silicone hydrogel

mainly contains water, allows oxygen to pass through to the eye

advantages of soft contact lenses

discreet- no specs needed

versatile

reusable

customisable

can fit faces that specs may be difficult for

disadvantages of contact lenses

cant fit all eyes

some people cant wear them

requires certain amount of dexterity

can be expensive

risk of infections and side effects

contact lens optics

no back vertex distance

no change in retinal image size with a contact lenses, with specs the images will either be magnified ( hyperopia) or minified ( myopia)

contact lens optics- accom

accom and convergence does not change with contact lenses as no BVP

rigid contact lenses

small, unbendable, and sit on the cornea and let oxygen through

mostly made from fluorosillicone acrylates and oxygen permeable

cover the entire cornea

advantages of RGPs

good vision

less risk of infection

used to give vision for diseases like keratoconus

much cheaper over time

disadvantages of RGPs

require adaptation to initial discomfort

not as simple to fit

can cause a ptosis over long term use

complex contact lenses

used for those with complicated eye conditions or vision problems

hybrid - rigid centre, soft outer skirt and used for keratoconus, high astigmatism and px who cant tolerate RGPs

piggyback - wearing 2 CLs on the same eye and a RGP is placed on top of the soft contact lens : keratoconus, irregular cornea

orthokeratology - specially designed rigid lenses worn overnight to temporarily reshape cornea

sclera/corneaoscleral lenses - large RGP lenses that rest partly on the cornea and partly on the sclera. creates tear filled space over conea and helps smooth out irregular corneal surfaces

refractive surgery options

radial keratotomy- cutting through the cornea until it becomes flat

LASEK

LASIK

clear lens extraction/replacement

can correct myopia, hyperopia, astigmatism and presbyopia

laser surgery- LASEK

laser epithelium keraromileusis

creates a flap of the cornea using 205 alcohol solution for 30 seconds to soften cornea and dissolve adhesion of hemidesmosomes to bowmans membrane

epikeratome is then used to push the flap created to the side

anterior corneal stroma is then abalated by the required amount where needed and then replaced back into stroma

bandage CL used to keep flap in place until readhered

used more when cornea is thin and there is less tissue to use

disadvantges of LASEK

more pain and photophobia

smaller area of vision as limited by size of epithlial flap

distorted vision and sometimes haze initially- depends on the state of healing, but also size of flap, if too small you may get edge of disortion

Rx stabilised after 3 months

can have some regression

laser surgery- LASIK

corneal flap is cut now instead, slightly deeper to allow middle stromal shaping

cut either with a microkeratome or femtosecond laser

topical anasthetic needed

lid speculum holds lids open and suction ring put on cornea. IOP can rise above 50mmHg

reshape underneath and then reposition flap

imporvements include wavefront guided laser surgery to remove higher order aberrations and imporve visual quaility

timeline of LASIK

fast recovery- sometimes within a few hours

grittiness and watery vision in day 1

2 days flap subsides

1 month to get less glare and haloes around lights

some refractive shift still may occur in first 6 months

Rx stabilised in few months with reduction of scar until only visible on slit lamp or with fluorescein

post op complications of laser surgery

infections

over or under correction likely

5% may need retreatment

irregular astig and persistent haloes

reduced constrast sensitivity

dry eye sensations- up to 6 months

stromal haze

diffuse lamellar kerititis

myopic regression- cutting too much of cornea can cause keratoconus

refractive surgery- IOLs

either clear lens extraction for high myopes or essentially an early cataract operation with adjustment to the presciption to correct refractive error

case:

40 year old myope

large prescription: -20D in each eye, stable for the last 5 years

specs causing facial irritation, and px wants change

what alternative refractive corrections are there?

how could you explain the pros and cons of the different options

too high of a prescription for laser surgery

IOLs: better option due to age and how high the prescription is

pros are that is is not permanent so px can change mind,

case 2:

20 year old hyperope

shy, and come in for routine sight test and wants to be an uber driver

refraction: +10.00/-2.00 × 180 Rx in both eyes

px unhappy with their glasses

what options does px have and what is most recommended

are there any requirements in relation to their work aspiration?

no surgery as high prescription

RGPs more better, can do soft contact lenses