A cycloplegic refraction test is an eye evaluation to determine a patient's total refractive aberration or error by momentarily relaxing the eye focusing muscles. A refractive aberration is an optical defect that prevents light from being correctly focused on the back of the eye, resulting in a visual error such as shortsightedness, farsightedness, blurred or distorted vision. The test helps to determine the cause of the eye anomaly without the patient interfering with the eye focus. It is an invaluable procedure in the assessment of patients with ocular deviation or reduced vision.
The eyes get their refracting power from the cornea and the lens, which jointly work to bend incoming beams of light and the accommodative ability of the eye. The eye's accommodative ability is its focusing power. The eye changes the path of light by making the ciliary muscle, which is the focusing muscle, alter the shape of the lens. The doctor uses cycloplegic medication in the form of eye drops during the examination to temporarily relax the focusing muscle. This allows the doctor to measure the objective or static refractive error of the eye without the patient influencing the results.
The cycloplegic medication is useful in patients with a large amplitude of accommodation. Therefore, cycloplegic refraction has limited use in adults because the magnitude of accommodation slowly decreases with age. The test is most suitable for children and young adults up to 20 years of age. Patients in this age bracket should have routine cycloplegic exams, especially those with inwards deviation (esodeviation).
Also Known As
The cycloplegic refraction test can be conducted at the doctor's office, eye clinic, or hospital by:
- An optometrist
- An ophthalmologist
Cycloplegic refraction is taken as the gold standard for evaluating refractive aberrations in children and adolescents. It is the cornerstone of the eye tests on young children. The test is often done on children because they have a sizable accommodative ability. Younger children also tend to focus on near objects and may not control their focusing when they have to look at distant targets during an examination. Generally, children tend to be over-accommodating in manifest and auto-refractions. It causes their refractive error to seem more shortsighted (myopic). Therefore, a cycloplegic exam is necessary to ascertain the precise refraction and prescription.
A cycloplegic exam is not a component of a standard eye exam. The specialist may order it in exceptional cases. The test also dilates the pupils and prepares the patient for an ophthalmoscopic exam. Children need a thorough ophthalmoscopic examination to check for abnormalities in the inner eye and opacities in the visual media. Cycloplegic refraction may also be helpful for patients who have undergone standard eye exams and are experiencing difficulties with the prescribed lenses.
Other groups of patients that may benefit from cycloplegic refraction include:
Older children and young adults
The exam can verify the diagnosis of ciliary spasm or accommodative spasm. It is an intermittent or constant, involuntary increased ciliary contraction. It may be due to the seizure of high ciliary tonus or the near reflex. It may also be caused by secondary factors like convergence insufficiency or farsightedness (hyperopia). Patients with low hyperopia can appear as myopic during a routine eye exam. The disorder, also known as pseudo myopia, can be detected by cycloplegic evaluation.
Presbyopia is a disorder in which the patient starts to have difficulties focusing on close objects. It is common in people around the age of 40 to 45. It is the reason why many people above 40 years of age wear a bifocal or use reading glasses. However, in patients with pre-presbyopia, the symptoms may develop much earlier. They may be unable to focus correctly at night or to change their focus quickly from near to far distance objects. Cycloplegic refraction offers the doctor the best way to isolate the problem.
Handicapped or mentally disabled
The test may be necessary for handicapped or mentally disabled patients because they are unresponsive to subjective refraction. It also might be useful in objectively evaluating suspected hysterics or malingerers.
Cycloplegic refraction is now an invaluable preoperative test to accurately measure the refractive error in a patient who wants to undergo laser vision correction (LASIK) surgery or any other refractive surgery. The test is done to ensure that the patient's accommodation will not influence the results. The eye surgeon will need to know in precise terms how much of the patient's refraction error to correct.
Preparation & Expectation
It is critical for the patient to tell the doctor if they are suffering from glaucoma or a family member has the condition.
The doctor should also know if the patient is allergic to any medication and about any medications they are taking, including prescription drugs, OTC medicines and dietary supplements.
The patient will have to remove their glasses or contact lenses before the exam. The patient may also experience increased sensitivity to light for many hours after the test. Therefore, they should come with protective sunglasses and someone to drive them home after the examination.
The evaluation requires the use of cycloplegic eye drops. The doctor will apply the medication on the patient’s eyes at the beginning of the exam. The eye drops may sting a bit and make the patient’s vision blurred for a while. The patient will sit or stand, looking at a distance target with both eyes open. The doctor will examine the cylindrical/ spherical error in the patient's right eye first and then repeat the process on the other eye.
Usually, a reasonably low threshold is kept for children who have a significant refractive error in early childhood or a strong family history of amblyopia.
Abnormal results may reveal:
Hyperopia- the inability to see close objects
Myopia- the inability to focus on distant objects
Strabismus- a condition in which the eyes are misaligned
Astigmatism- a vision disorder that causes blurred vision
Amblyopia- a disorder in which the brain ignores information from one (or both) eye(s)
Pre-presbyopia- an abnormality where a patient under 40 begins having challenges with focusing on up-close objects
Risks & Complications
Cycloplegic medication may have several side effects, including:
- Blurring of vision
- Acute angle-closure glaucoma attack in patients with very narrow angles