Understanding Your Eye Prescription: Scuba Divers / Snorkelers

Understanding Your Eye Prescription: Scuba Divers / Snorkelers

When it comes to deciphering your eye prescription, it’s essential to grasp the key elements that define your vision needs. Primarily, eye prescriptions consist of values for Sphere (Sph), Cylinder (Cyl), and Axis.

  • Sphere (Sph): This indicates the degree of nearsightedness (-) or farsightedness (+). A negative value suggests nearsightedness, while a positive value signifies farsightedness.
  • Cylinder (Cyl): If present, this denotes the amount of astigmatism in your eyes. Astigmatism arises when the cornea or lens is not perfectly spherical, leading to distorted vision. A higher Cylinder value implies more significant astigmatism.
  • Axis: Associated with the Cylinder value, the axis pinpoints the orientation of the astigmatism, measured in degrees.

Determining Nearsightedness or Farsightedness:

  1. Nearsightedness (Myopia): If your Sphere (Sph) value is negative, you’re likely nearsighted. The higher the negative value, the stronger your nearsighted prescription.
  2. Farsightedness (Hyperopia): A positive Sphere (Sph) value indicates farsightedness. Similar to nearsightedness, a higher positive value implies a stronger farsighted prescription.


Reading a scuba snorkeling mask prescription


Understanding Astigmatism:

Astigmatism is revealed by the Cylinder (Cyl) and Axis values:

  1. Cylinder (Cyl): A non-zero value indicates astigmatism. The higher the value, the more significant the astigmatism.
  2. Axis: Specifies the orientation of the astigmatism. It’s measured in degrees, ranging from 0 to 180.

Scuba Mask Prescription eye chart exam

Additional Considerations:

  • Reading Add (Add): For individuals with presbyopia (age-related difficulty focusing on close objects), an additional reading add value is specified.
  • Prism and Base: For those with eye alignment issues, Prism and Base values may be included.

Incorporating this understanding, you can interpret your eye prescription and gain insights into your vision needs. Regular eye check-ups and consultations with eye care professionals are crucial for accurate prescriptions and maintaining optimal eye health.