Causes of Unstable Vision Despite Corrective Lenses

Q: Causes of Unstable Vision Despite Corrective Lenses

Hello Shinna： Amblyopia can lead to unstable vision. <br>The phenomenon of crowding in amblyopia is similar to the situation you described. <br>The letter C is likely more difficult than the letter E; the letter E has two openings and only four orientations, while the letter C ha

Unstable vision

Hello, Doctor.
If the prescription for my glasses is adequate and there are no changes in the fundus, I would like to ask what could be causing the instability in my corrected vision.
During the first and second grades of elementary school, my vision was measured at 0.4 during school screenings (using a projection method).
In the third and fourth grades, I could see 0.5 to 0.6, but during ophthalmology exams (using a row-by-row vision chart), I could only see 0.4.
In the fifth and sixth grades, both school and ophthalmology exams showed 0.4.
I remember that seeing clearly at 0.4 was quite difficult and straining (the charts used were the E-shaped vision charts).

In junior high school, the school vision tests used a machine where my forehead rested against it to view the vision chart, and the results varied between 0.1, 0.2, 0.3, and 0.4 (using a C-shaped vision chart).
The ophthalmology exam still showed 0.4, but it felt very straining.
In high school, the school vision tests were similar to junior high, also using a C-shaped vision chart, and most of my results were around 0.1 (sometimes even 0.1 was very straining), occasionally 0.2, and rarely 0.3.
In the ophthalmology clinic, both E-shaped and hospital C-shaped tests showed 0.3, but I don't understand why I cannot see 0.4 clearly (other tests showed no significant changes).

The vision chart in the ophthalmology clinic is a full row, so seeing 0.3 feels very straining, requiring prolonged judgment, and my eyes have to work very hard, with only a vague ability to recognize the letters (this seems like the crowding phenomenon associated with amblyopia?).
The hospital tests project one letter at a time, and seeing 0.3 seems slightly less straining.
Could you please clarify if there is a difference between the E and C vision charts? Thank you for your response.

Shinna, 10~19 year old female. Ask Date: 2022/04/13

Dr. Gao Pilin reply Ophthalmology

Hello Shinna: Amblyopia can lead to unstable vision.
The phenomenon of crowding in amblyopia is similar to the situation you described.
The letter C is likely more difficult than the letter E; the letter E has two openings and only four orientations, while the letter C has eight orientations, making it harder to guess due to its shape.

Reply Date: 2022/04/13

More Info

Understanding the causes of unstable vision despite having corrective lenses can be a complex issue, as it involves various factors related to eye health, the quality of the lenses, and individual visual processing. Based on your description, it seems that you have experienced fluctuating vision quality over the years, despite having corrective lenses that are deemed appropriate for your refractive error. Here are some potential reasons that could contribute to this phenomenon:
1. Refractive Errors: While you mentioned that your glasses have the correct prescription, it’s essential to ensure that the prescription is up-to-date. Changes in your vision can occur over time, and even slight variations in refractive errors can lead to significant differences in visual clarity. Regular eye exams are crucial to monitor any changes in your vision.

2. Visual Acuity and Contrast Sensitivity: Visual acuity is just one aspect of vision. Contrast sensitivity, which refers to the ability to distinguish objects from their background, can also affect how clearly you see. If your contrast sensitivity is low, you may find it challenging to see clearly even with the correct prescription. This can be particularly noticeable in low-light conditions or when viewing objects with subtle differences in color or brightness.

3. Astigmatism: If you have uncorrected or improperly corrected astigmatism, it can lead to blurred or distorted vision. Astigmatism occurs when the cornea is irregularly shaped, causing light to focus on multiple points in the eye. If your lenses do not adequately address this issue, you may experience unstable vision.

4. Eye Health Conditions: Conditions such as cataracts, macular degeneration, or other retinal issues can affect vision quality. Even if your eye exam shows no significant changes, subtle changes in the eye's internal structures can impact how you perceive visual information. Regular monitoring through comprehensive eye exams, including retinal imaging, can help detect any underlying issues.

5. Visual Processing Issues: Sometimes, the problem may not lie within the eye itself but rather in how the brain processes visual information. Conditions such as convergence insufficiency or other binocular vision disorders can lead to difficulties in maintaining clear vision, especially when focusing on near objects.

6. Lens Quality and Type: The type and quality of the lenses you are using can also play a significant role in visual clarity. High-index lenses, anti-reflective coatings, and aspheric designs can enhance visual performance. If your lenses are scratched, dirty, or of lower quality, they may not provide the clarity you need.

7. Environmental Factors: Lighting conditions, glare, and screen time can also affect how well you see. Prolonged exposure to screens can lead to digital eye strain, which may cause temporary fluctuations in vision clarity. Ensuring proper lighting and taking regular breaks can help mitigate these effects.

8. Psychological Factors: Anxiety and stress can also impact visual perception. If you are overly focused on your vision or anxious about your eye health, it may exacerbate your perception of visual instability. Addressing these psychological factors through relaxation techniques or counseling may help improve your overall visual experience.

Regarding your question about the differences between E and C vision charts, it is important to note that different charts can yield varying results due to their design and the way they test visual acuity. The E chart (often used for children or those who cannot read) and the C chart (which may be used in clinical settings) can present letters or symbols differently, potentially affecting how individuals perceive their visual acuity. The way the letters are arranged and the spacing can influence how easily someone can identify them, especially if they have difficulty with crowding phenomena, which is common in amblyopia (lazy eye).

In conclusion, if you continue to experience unstable vision despite having the correct prescription, it is advisable to consult with an eye care professional for a comprehensive evaluation. They can assess not only your refractive error but also other factors that may be contributing to your visual difficulties. Regular eye exams and open communication with your eye care provider are essential for maintaining optimal eye health and vision clarity.

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