What is Oculus Uterque (OU)?
OU or Oculus Uterque is the Latin term that translates to “both eyes”. If you have blurry vision, your eye doctor (ophthalmologist or optometrist) might prescribe eyeglasses to help make your vision clear. An eyeglasses prescription usually has three important medical abbreviations: OU (Oculus Uterque), OD (Oculus Dexter), and OS (Oculus Sinister). In Latin, the term oculus translates to eye, and the term uterque translates to both. Hence, Oculas Uterque translates to both eyes.
Key Points
- OU or Oculus Uterque is the Latin term that translates to “both eyes”.
- OU is used in a glasses prescription when both eyes have identical lens powers.
- The OU column isn’t always present on a glasses prescription. It is omitted if both eyes have different lens powers.
Understanding Oculus Uterque
OU is the acronym for Oculus Uterque, used widely by ophthalmologists and optometrists. Most notably, OU is a term written in the glasses prescription indicating the prescription for both eyes. The OU value in a spectacle prescription is the amount of lens power. Measured in diopters, it indicates the correction for nearsightedness or farsightedness.
OU is written in prescriptions when the glasses prescription is the same number in both the left and right eye. When OU is used, it indicates that the power of nearsightedness or farsightedness is identical in both eyes.
How To Read an Eyeglass Prescription
Often, your left and right eye will have different prescription strengths. In that case, you won’t even see OU on your prescription. Let’s take a closer look at the other terms and abbreviations you may find on your glasses prescription.
Sphere (SPH)
The glasses prescription may be a spherical measurement, abbreviated as SPH (Sphere). If the prescription only has a SPH number, and no CYL number, it indicates that the prescription does not have astigmatism. When there’s a spherical cornea, the eye has a round shape and the corneal power is the same throughout the entire cornea.
With a spherical cornea only one prescription power, the SPH power, is needed to correct the refractive error. A spherical cornea bends light the same way throughout the eye. If both a SPH and CYL value is present in the prescription, the eye has astigmatism. The SPH power is the lens power required to correct the vision. The sphere value may be plus (+) indicating farsightedness, or minus (-) indicating nearsightedness.
It’s helpful to understand your glasses prescription in the case that you want to know whether it is weak or strong, and when ordering glasses online. A high amount of nearsightedness can be sight-threatening.
Nearsightedness
High nearsightedness is defined as -6.00 D or more. With high nearsightedness, the eye’s tissues become thin and stretched out as the eye grows. The thin ocular tissues are more prone to tearing or breaking. Individuals with a high nearsighted prescription should monitor for sudden visual changes that can indicate a retinal tear — such as flashes of light, a sudden increase in floaters, or a curtain covering the vision. If these symptoms occur, your eye doctor should evaluate the health of the retina as soon as possible, ideally on the same day.
Farsightedness
A high amount of farsightedness also can cause problems, especially for children. High farsightedness is defined as +5.00 D or more. Children with high farsightedness are more likely to have strabismus, also known as lazy eye or an eye turn. High farsightedness causes eye strain and headaches.
If children with high farsightedness are not given glasses during their visual developmental period, before 8 years old, it is possible that the child may have permanently decreased vision (amblyopia). High farsightedness may deter children from doing near work such as reading and homework, which can negatively affect school performance. Sometimes children are incorrectly diagnosed as having special needs or learning disabilities when they truly only need a pair of glasses.
Cylinder (CYL)
If the glasses prescription has a numerical value under the CYL column, it indicates that the eye has astigmatism. The cylindrical value describes the amount of astigmatism. Astigmatism means that the cornea, the clear outer layer of the eye, is not perfectly round, and instead is more oval-shaped.
An oval-shaped cornea bends light differently in different areas of the eye, and it cannot focus to a single point. Astigmatism is a benign refractive condition, similar to nearsightedness and farsightedness. It’s easily corrected with a glasses prescription.
In rare cases, a high amount of astigmatism may pose a threat to vision. High astigmatism is defined as 3.00 diopters of cylinder or greater. A high amount of astigmatism may be associated with keratoconus, a corneal disease that causes progressive thinning and bulging of the cornea. However, astigmatism is usually not a cause for concern for the majority of the population.
Axis
The axis is defined as the direction of the astigmatism on a scale of 001 to 180 degrees, and follows the “x” on the prescription. This is the direction that light needs to enter the eye in order to be properly focused. The axis of astigmatism may change depending on whether the eye doctor prescribing glasses uses minus cylinder or plus cylinder.
ADD
The ADD power of the glasses prescription is the amount of reading power that is added to the distance prescription, to aid in near tasks like reading. The ADD power is only indicated for progressive lenses, bifocals, or powerboost lenses which all have both a distance and reading power within the same lens.
ADD powers are typically used for patients who have trouble focusing up close, such as patients 40 years or older, or young patients with abnormal eye postures (esophoria or esotropia). The ADD power is the amount of power added to the distance prescription to make the near vision clear. An ADD power is required for up-close activities such as reading, writing, or knitting.
A typical ADD power ranges from +0.50 to +2.75. Younger people will require a lower ADD power. The ADD power linearly increases with age. For example, a 45 year old person may require an ADD power of +1.50. A 60 year old typically requires an ADD power of +2.50. The ADD power stabilizes around the age of sixty and does not increase much afterwards.
Prism
In rare cases, the glasses prescription has a numerical value for PRISM. Most patients do not have prisms in their glasses and this amount is left blank.
Prism is a lens treatment that bends light to correct eye alignment. Prism may be prescribed for people who have strabismus (lazy eye), double vision, or poor binocular vision. It changes the direction of light entering the eyes, so that the image viewed through the glasses is moved in space.
Prism looks the same as a nearsighted or farsighted lens, and it does not change the lens appearance from the outside. If prism is present, the prescription will also indicate the amount and direction of prism.
The amount of prism varies based on the amount of eye misalignment. A small eye misalignment may require 1.00 D of prism in each eye, whereas large eye misalignments require 3.00 D or more per eye. The prism direction may be BI (base in), BO (base out), BU (base up), or BD (base down). For example, the prism value may be written as “2.00 BI”, indicating both the amount (2.00) and the direction (base in).
Oculus Uterque and Your Prescription
Oculus Uterque (OU) is a term that refers to “both eyes”. You’ll find a value for OU on your glasses prescription if both of your eyes require the same lens magnification. Oculus Uterque (OU) is omitted however if your eyes require different strength lenses.
