Lecture 6: Prescribing for different refractive states DISTANCE Flashcards
What is the risk of you always prescribe the final refractive endpoint?
*Px will be dissatisfied with new specs e.g., non-tols, bounces
*Average spectacle dissatisfaction rate for UK optometry practices in 1-3%
What is the decision making when prescribing based on?
*Prescribers experience
*Patients age (the older they are, the less they can adapt)
*Assessment of px ability to adapt to change
*The prescription currently worn
*Binocular status
*The needs/requirements/occupation
What should you do before prescribing?
What is the best practice for changing the rx?
*Demonstrate to the patient the difference in acuity between previous and new prescriptions (Rx), and hence show the patient the improvement in VA with the new Rx
*Ideally by holding lenses over the top of existing glasses – but this only works well for spherical changes
* Ideally outside the examination room
changing Rx if there is a two-line improvement in VA.
When should you not change rx?
When can you consider a partial increase/change?
- Don’t change an Rx if px is happy wit current glasses
*Consider partial increase in plus power when significantly increasing hyperopic prescription
*Consider partial change when significantly altering cyl power/axis
*Make any large changes (1.00DS or greater) in stages especially in elderly
What are the different categories of refractive error when prescribing for the distance?
1.Hypermetropia
-non-presbyopes
-presbyopes
2.Myopia
-myopes in general
-myopic presbyopes
- Astigmatism
What should you consider when prescribing in non-presbyope hypermetropic patients?
*If px is asymptomatic: don’t prescribe glasses for distance use
*Young px has large amplitude of accommodation
*Distance correction may be appropriate for near vision use as these patients approach presbyopia.
When may you not need to prescribe for hypermetropic presbyopes?
-px is asymptomatic
-px meets legal driving standard
What must you do before altering rx for distance?
consider consequences for near vison
When should you prescribe a cyl?
*Most optometrists disregard 0.25 DC when prescribing unless:
-cylinder is already worn in current rx
-px notices a subjective improvement in VA with 0.25 cylinder (many px wont)
What can happen when a px is prescribed a low/moderate cyl for the first time?
What advice should you give them?
*Correction will give clear retinal image, but the brain is not used to interpreting this sharp image
*Patient will complain of distortion e.g., straight edges appear curved
*Patient must be counselled all the time in refraction (advised at time of refraction)
*Advice: when you first put them on things will look clear but distorted. If bothering you, take them off and have a rest. Don’t drive until you are confident with glasses.
What are the options for prescribing a high cyl for the first time?
- full rx given.
- partial correction (mean sphere equivalent)
- no correction (best option if elderly)
When can you justify changing the cyl axis?
noticeable improvement in VA
-always record VA achieved with modified rx
What must you not do when prescribing in younger px?
How can you avoid it?
-dont over-plus for distance
-prescribe for infinity +0.25 less binocularly than max plus consistent with best VA
-leave patient binocularly just green on duochrome
What must you not do when prescribing in older patients?
What can cause this?
How can you avoid this?
-over-minus
lens opacities effect duochrome
-green wavelengths are scattered more than red so there is red bias
-prescribing for inifnity max plus consistent with best VA
-leave px clearer on the green prior to crossed cyl
