Inside your eye exam: eye drops for vision testing

• Accommodation is the eye’s ability to adjust its natural lens so it can focus on objects at different distances, especially up close

• Accommodation dysfunction can affect children's visual comfort and learning.

• Cycloplegia (use of special eye drops) relaxes the eye’s accommodation, providing a more accurate prescription measure and helping to rule out vision problems.

Accommodation is the eye’s ability to adjust its natural lens so it can focus on objects at different distances.

• When looking at an object up close (like a book or a screen), a small muscle in the eye called the ciliary muscle contracts. 
• When the ciliary muscle contracts, it causes the lens inside the eye to change its shape. 
• The lens becomes thicker and more rounded, causing objects up close to be brought into focus inside the eye. 
• This adjustment process is known as accommodation.

• When looking at an object at a far distance (like a tree several metres away), the eye tends not to accommodate. 
• For viewing at longer distances, accommodation is generally not necessary to achieve clear vision, so long as distance vision lenses with the correct prescription are worn. 
• In this relaxed state, the ciliary muscle loosens, and the lens inside the eye remains thin.

Symptoms of accommodative problems can sometimes be mistaken for learning difficulties. Common symptoms may include:

• More frequent headaches than usual
• Difficulty in focussing during near work
• Blurred vision
• Double vision

A group of eye conditions collectively known as accommodative dysfunctions, can lead to challenges in focusing, eye strain, and discomfort. The types of accommodation problems include^1,2

• Insufficiency of accommodation – when the focusing ability is consistently lower than what is expected for the child’s age.
• Infacility of accommodation – when the eyes have trouble quickly shifting focus between near and far objects.
• Fatigue of accommodation – when the eye muscles cannot maintain focus on close work for long, causing blur after reading or writing.
• Spasm of accommodation – when the eye muscles contract inappropriately, leading to constant or intermittent focusing problems.
• Excess of accommodation – when the eye unable to relax accommodation

Accommodation problems can often be treated. Depending on the case, accommodation dysfunction can be managed with glasses or contact lenses or in combination with vision therapy. 

If you suspect your child may have difficulty focusing, schedule an appointment with your optometrist for a comprehensive eye examination.

Push up test: This test measures the strength of the eye’s focusing ability. In this test, a Royal Air Force (RAF) ruler or Prince ruler will be used. The optometrist will ask the child to maintain focus on a near object as it is gradually brought closer to the eyes.

Dynamic retinoscopy : This is to test how accurately the eyes can accommodate. You will see the optometrist will use a retinoscope to shine light into the eye while your child views a near point (close vision) target.

Accommodative facility test : This test check the eye’s ability to quickly switch focus between near and far objects. The optometrist will put a lens flipper in front of the eyes while the child focuses on making letters or words clear for reading.

Positive and Negative Relative Accommodation (PRA & NRA): PRA and NRA test the amount of accommodation required to focus an object at a specific distance. The optometrist will place a series of lenses in front of the child's eyes to see how strongly the eyes can focus, and how well they can relax their focus.

AC/A ratio : The eye’s focusing systems and eye alignment work closely together for near and far viewing. This test helps the optometrist understand the relationship between focusing and eye alignment. The optometrist will calculate AC/A ratio using a formula.

Cycloplegia involves using eye drops which result in a temporary paralysis of the eye's ciliary (focussing) muscle, leading to a loss of accommodation and dilation of the pupil.³

Optometrists routinely use cycloplegia (eye exam testing drops) in order to be able to measure the eye’s prescription more accurately, especially in the initial assessment of school-aged children. 

Cycloplegic examination is also often used to help diagnose a number of vision problems, including:

• Eye turns (strabismus)
• Difficulties with accommodation and focussing
• Pseudomyopia (shortsightedness due to overactive accommodation)
• Poor or reduced vision (amblyopia)

Firstly, the optometrist will prepare and apply the eye drops for cycloplegia. Afterwards, you may be advised to wait a period of time, to allow the eye drops to settle in before eye testing begins.

During the eye exam and the remainder of the day, your child will experience temporary changes to vision, including:

• Difficulty focussing on near objects, because the eye drops relax accommodation
• Light sensitivity, because the eye drops also enlarge the eye’s pupils

The effects of cycloplegia usually begin 25 minutes after the eye drops are applied, and the majority of vision changes will start to fade about 6 hours afterwards.⁴ It is recommended to bring a pair of sunglasses to wear afterwards, for children and adults. For adults undergoing cycloplegia, it is advised to arrange suitable transportation after the appointment, avoiding driving until vision recovers.