Phentermine is a prescription medication used for short-term weight loss. It functions as a stimulant by influencing brain chemicals to reduce appetite. While used for weight management, phentermine can cause various side effects, including vision changes. This article explores why phentermine can lead to blurry vision and other visual disturbances.
How Phentermine Affects Vision
Phentermine is a sympathomimetic amine, mimicking the “fight-or-flight” response. It increases neurotransmitters like norepinephrine. The exact mechanism by which phentermine causes blurry vision is complex but related to its stimulating effects on the eyes.
Phentermine can affect vision by causing pupil dilation, a condition known as mydriasis. When pupils widen, more light enters the eye, making it challenging to focus clearly, especially in bright conditions. This contributes to blurriness.
Beyond pupil dilation, phentermine can also influence the eye’s internal structures responsible for focusing. The medication may lead to ciliochoroidal effusion and ciliary edema. This involves a buildup of fluid and swelling in the ciliary body, a part of the eye that controls the shape of the lens.
Swelling or fluid accumulation in the ciliary body can cause the lens-iris diaphragm to shift forward. This displacement can result in a change in the eye’s refractive power, leading to an acute myopic shift, or sudden nearsightedness. When the eye’s natural focusing mechanism is disrupted, objects at various distances may appear blurry.
Other Visual Disturbances
While blurry vision is a notable concern, individuals taking phentermine might experience other visual changes. Dry eyes are a common side effect. This can occur due to effects on tear production or increased evaporation, leading to discomfort and sometimes affecting visual clarity.
Increased sensitivity to light, known as photophobia, is another visual disturbance. This symptom is often related to the dilated pupils, allowing excessive light to enter the eye and create discomfort. Additionally, some individuals may notice general alterations in their vision, which can affect motor skills and overall visual perception.
Managing Blurry Vision
If you experience blurry vision while taking phentermine, consider practical steps. Ensuring adequate hydration is important, as phentermine causes dry mouth, and dehydration can worsen side effects. It is also advisable to avoid activities that demand sharp vision, such as driving or operating heavy machinery, until you understand how the medication affects your visual clarity.
Resting your eyes periodically and ensuring proper lighting can help alleviate strain. If the blurry vision is mild or intermittent, these measures might offer relief. Never adjust your phentermine dosage or discontinue the medication without first consulting your healthcare provider.
When to Seek Professional Advice
Promptly report any visual changes to your healthcare provider. Consult your doctor immediately if you experience a decrease in vision, persistent blurry vision, or changes in your near or distance vision. Any pain around the eyes should also be reported without delay.
Certain symptoms warrant immediate medical attention, including sudden vision loss, tunnel vision, severe eye pain or swelling, or seeing halos around lights. If you have glaucoma, your doctor will likely not prescribe phentermine, as it can increase eye pressure and potentially cause permanent vision damage.