CLM - Non-Surgical Management of Myopia III - Week 9 Flashcards
List two topical, muscarinic (M) receptor antagonists and their selectivity.
Atropine (non-selective)
Pirenzepine (more selective for M1 receptors)
Briefly describe a possible direct effect and three indirect effects of muscarinic receptor antagonism for their mechanism of action. Is it well understood?
Direct effect
-muscarinic receptors in the posterior eye
Indirect effect
-reduced accommodation (unlikely)
-alternations in neurotransmitter release
-changes to patterns of -systemic growth hormone release
Mechanisms are not well understood
Describe the direct effect of atropine on muscarinic receptors (and the consequences of this) and on the sclera.
Atropine boosts the release of dopamine by amacrine cells
Also acts on scleral fibroblasts, possibly interfering with scleral remodelling
What are two major findings of the ATOM study on the use of atropine for myopia progression?
1% topical atropine reduced myopia progression by 77% over two years compared to controls and untreated eyes
No serious adverse events reported from using atropine
Consider atropine treatment for myopia control. What do studies suggest if the use of atropine is stopped?
Post-treatment, atropine treated eyes showed more rapid myopia progression
List short-term ocular side effects of 1% atropine for myopia progression and its implication if applicable.
Photophobia (mydriasis)
Blurred vision (cycloplegia)
-potential effects on learning ability and sporting activities
Headaches/brow aches
List two possible long term ocular side effects of atropine for myopia progression.
Not fully known
Increased risk of UV related retinal damage
Cataracts (UV related)
What is atropine for myopia progression typically prescribed with and why?
Photochromatic PALs due to its mydriatic and cycloplegic effects
Describe the ATOM2 study and its two major findings and a flaw.
Investigated the use of 0.01% atropine for myopia progression in place of 1%
Found negligible effects on pupil size and accommodation
It is limited by a lack of a true placebo/control group
What was the major finding in comparing lower doses of atropine with higher doses for myopia control?
0.01% eyedrops were more effective in slowing myopia progression with less visual side effects compared to higher doses
Compare the rebound of myopia progression when treated with high or low doses of atropine.
Greater rebound with higher doses of atropine
Is the effect of atropine on myopia progression dose-dependent?
Yes, the lower the dose, the less effect it has
What is the maximum dose of atropine without clinical signs or symptoms?
0.02%
Does 0.01% atropine significantly attenuate axial length change?
No
What has been proposed as the optimal dose of atropine for myopia progression control? (LAMP study)
0.05%
List three possible risk factors for progression and greater rebound effects. What do these risk factors suggest about the appropriate dosage of atropine for individuals at risk?
Younger age
Higher baseline myopia
Faster progression
It has been proposed that at risk children may benefit from higher dose atropine during the first year, tapered to a lower dose as maintenance therapy
Is there a difference in the efficacy of atropine in asians vs caucasians?
No
Can atropine be safely stopped, while avoiding rebound effects? In which population is this more significant? How does the dose of atropine fit in? Given all this, what is the recommendation on how long treatment should last?
It is more significant in younger children, with less rebound occuring with 0.01% atropine
Recommended to continue treatment until at least 12 years of age
Consider the recommended length of treatment with atropine for myopia progressiion control. What consideration needs to be given for this kind of length of time?
The lack of long term safety data (>5 years)
Is there evidence atropine can be used for myopia prevention?
Regular topical administration of 0.025% atropine eyedrops can prevent myopia onset and myopic shift in premyopic schooldhildren for a 1 year period
Define off-label use. Is it illegal?
The practice of prescribing a drug for a purpose other than that for which it is approved
It is legal
Does ambient light exposure influence eye growth?
Yes
Below what period of time spent outdoors per day is a risk factor for myopia development?
<2h per day
Does outdoor activity have a definitive protective effect on myopia progression?
Yes
Can time outdoors potentially offset parental history of myopia or not?
Yes
Compare the effect of age on the protective effect time outdoors has on myopia progression.
Stronger effect in children aged 6 compared with 12
Is the protective effect of time outdoors on myopia progression related to physical activity and/or UV exposure? Explain.
Not related to physical activity or UV exposure but may be related to specific wavelengths of visible light
What is the current major hypothesis on the mechanisms of the protective effect of time outdoors on myopia progression?
Protective effect via light-stimulated release of dopamine, which inhibits axial elongation.
Is outdoor time effective in slowing progression in eyes that are already myopic?
No
Is there an association between near work and myopia? Explain the mechanisms if applicable.
Associations between time spent reading and myopia have not been consistently observed and is less compelling compared with outdoor activity
Originally thought to be accommodative effort, also thought that accommodative lag creates retinal defocus
What concerning near work is thought to be associated with higher risk of myopia progression (2)?
Short working distance
Lack of 10 minute breaks after 30 mins
What period of time is required for outdoor activity to have a protective effect for myopia progression?
2, preferably 3
