Cycloplegia – Examination under cycloplegia and atropine
An eye exam using cycloplegic eye drops (Atropine® or Skiacol®) relaxes accommodative spasms, which are abnormal focusing mechanisms. These spasms cause discomfort such as blurred vision and headaches. They can also lead to errors in eyeglass prescriptions. An ophthalmologist may diagnose myopia falsely because you have experienced spasms, meaning you have strained your eyes during the eye exam. With cycloplegia, the pupils will be dilated and vision slightly blurred to relieve accommodation. Standard vision measurements will then be taken more accurately. This exam is performed on children, adults suffering from asthenopia (eye strain), when there is doubt about the prescription, or as a precaution before refractive surgery.
What is accommodation?
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Accommodation is the mechanism that allows the view of an object to be focused, depending on its distance: it is the phenomenon that allows a clear vision of an object to be maintained when brought closer, in the manner of a camera's "focus".
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It involves the lens and the ciliary muscle. The ability to accommodate is greatest at birth and gradually decreases with age. This explains why, from a certain age, near vision becomes increasingly difficult, to the point that the patient is forced to hold objects further away to see them clearly: this is presbyopia.
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Conversely, young patients who have a high capacity for accommodation and many activities involving near or very near vision (smartphones) excessively use this mechanism, which leads to accommodative spasms, which can result in visual fatigue.
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During a standard eye exam, the results can be biased by the fact that the patient accommodates more or less: in the case of significant accommodation by the patient, myopic patients risk being overcorrected, and hyperopic patients undercorrected or worse, corrected with myopic glasses!
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Since accommodation is an automatic, permanent phenomenon that cannot be voluntarily controlled, standard vision testing, when properly performed, uses methods aimed at minimizing the patient's accommodation contribution in order to obtain a reliable result that is consistent with the patient's complaint.
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It is when the result appears unreliable or when the situation requires an exact measurement of the correction, that the ophthalmologist decides to perform the examination under cycloplegic eye drops.
Why perform an examination while using cycloplegic eye drops?
Most of the time, the classic visual examination (without cycloplegia), although biased by accommodation, does not pose a problem if it is deemed reliable, consistent with the patient's complaint and improves the patient's quality of vision without creating discomfort.
However, some situations absolutely require eliminating the uncertainty associated with accommodation, in order to obtain a result that leaves no room for doubt:
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Children of pre-verbal age (under 3 years): as visual acuity measurement is impossible, the ophthalmologist can only rely on the automatic correction measurement, which therefore needs to be as accurate as possible.
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Children over 3 years old and adolescents who have never worn corrective lenses have a very strong ability to accommodate, which cannot be controlled by standard vision testing techniques. Ophthalmologists therefore need to reduce the risk of measurement error, which is significant because standard examinations are very unreliable in these cases.
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The standard measurement result does not correspond to the symptoms reported by the patient, possibly because the result is skewed by accommodation. The ophthalmologist therefore needs to determine whether the issue is related to optical correction or eye strain.
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Myopic patients who experience headaches or a very high prescription risk being habitually overcorrected. The ophthalmologist needs to ensure that the patient's prescription is not incorrectly increased.
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People with farsightedness who experience headaches despite wearing glasses, or who have difficulty adapting to their glasses, generally have their strong accommodative power responsible for their symptoms. The ophthalmologist needs to know the exact prescription in order to best tailor the glasses prescription.
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Patients with strabismus : since strabismus is aggravated by accommodation, an optical correction must be prescribed that allows the patient to completely eliminate accommodation, therefore measuring it under Atropine®. The ophthalmologist aims to prescribe the full correction.
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Patients with amblyopia: In amblyopia, the eye needs to receive the best possible image quality to develop optimal vision. The correction under Atropine® must also be measured. In this case as well, the ophthalmologist aims to prescribe the full correction.
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Patients who experience recurrent chalazia : a correlation has been shown between the occurrence of recurrent chalazia and undiagnosed or undercorrected hyperopia, or overcorrected myopia. In these three cases, patients do not complain of poor vision, but sometimes of eye strain due to accommodative spasm. The ophthalmologist then seeks to determine the optimal optical correction to reduce eye strain, which will have the indirect effect of reducing the frequency of chalazia occurrence.
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Patients eligible for refractive surgery : the ophthalmologist seeks to determine the exact correction, as the surgery aims to provide a permanent correction that cannot be changed over time.
What is cycloplegia?
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Cycloplegia is the procedure which consists of slowing down the patient's accommodation mechanism using eye drops, in order to measure their optical correction, without it being "distorted" by accommodation or visual fatigue.
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Cycloplegic eye drops temporarily paralyze the ciliary muscle, preventing the eye from focusing on its own while the ophthalmologist or orthoptist measures the optical correction. This makes the result more reliable.
What are the effects of cycloplegic eye drops?
Eye drops
There are two eye drops that can induce cycloplegia:
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Skiacol® (Cyclopentolate): after instillation of 3 drops within 10 to 15 minutes, it allows cycloplegia to be achieved in 45 to 90 minutes.
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Atropine®: prescribed at a dosage of 2 drops per day, for 3 to 5 days, it allows for a stronger cycloplegia.
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Skiacol® (Cyclopentolate) is the more widely used of the two, as it is quicker to implement and induces a shorter period of blurred vision (12 to 36 hours).
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The cycloplegia obtained with Skiacol® is less powerful than with Atropine®, but sufficient for the majority of indications.
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Skiacol® is contraindicated in children under 1 year of age and in patients with a history of seizures or epilepsy. If breastfeeding, it is best to suspend breastfeeding for 48 hours or postpone instilling the eye drops. If pregnant, it is advisable to apply pressure to the tear duct for 1 minute after instilling the eye drops, then wipe away any excess that spills onto the cheek to limit the absorption of the product into the bloodstream.
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Atropine® is available in 3 dosages depending on the patient's age: 0.3% for 0 to 2 years, 0.5% for 2 to 12 years, and 1% for those over 12 years. The induced blurred vision can last 2 to 7 days after the last instillation.
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Atropine® is the preferred product for children under 1 year old or for patients with strabismus or amblyopia, as the strongest possible cycloplegic effect is required in these cases. For this same reason, Atropine® is used as an alternative to Skiacol® when the latter's effect is insufficient, which can occur particularly in patients with dark pupils (African or Asian patients).
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The same precautions should be taken in case of pregnancy or breastfeeding as with Skiacol®.
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In addition to their cycloplegic effect, Skiacol® and Atropine® dilate the pupil, which can also allow for a fundus examination. While not the primary purpose of cycloplegic eye drops, this examination is nevertheless useful in cases of strabismus, amblyopia, or for pre-operative assessments for refractive surgery.
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Pupil dilation leads to sensitivity to light, for which it is recommended to wear sunglasses to reduce discomfort.
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The blurred vision resulting from the instillation of cycloplegic eye drops varies in severity depending on each patient's prescription: a farsighted patient will experience more difficulty with near vision than with distance vision, while a nearsighted patient will experience the opposite. However, wearing regular glasses will partially correct distance vision, enough for the patient to move around fairly easily, even outdoors.
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On the other hand, driving a car is too dangerous and therefore prohibited, due to blurred vision, the risk of glare and drowsiness that can be induced.
In practice
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The need for an examination under cycloplegia is determined either after a standard eye exam or routinely for strabismus or as part of a pre-operative assessment. In both cases, two eye exams are always performed: one before and one after instilling the eye drops.
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Most often, this cycloplegic examination is the subject of a later consultation, for reasons of practice organization (avoiding congestion of waiting rooms and delay for subsequent patients) or of the patient, who is not prepared to have blurred vision for the rest of the day.
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During this second consultation, the patient has previously instilled their eye drops, and arrives at the office ready to undergo the examination.
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After the examination, the ophthalmologist explains his findings to the patient and recommends appropriate treatment.
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Depending on the product used, the patient's discomfort lasts for a longer or shorter time, but since he was warned beforehand, he made arrangements accordingly.
Conclusion
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Performing an eye examination under cycloplegic eye drops is not a routine systematic examination, but results from medical reasoning by the ophthalmologist to arrive at an accurate diagnosis.
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It is essential to avoid correction errors, correct accommodative strabismus, or perform refractive surgery.
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It is prescribed by the ophthalmologist when the benefit to the patient is deemed to outweigh the inherent inconveniences (blurred vision, 2nd consultation).