An RAPD usually comes with decreased vision in the affected eye. An RAPD means the light signal from one eye is weaker than the signal from the other. That signal travels along the retina and the optic nerve. Those same structures carry the picture you see. So when the pupil signal is weak on the right, the right eye's sight is normally weaker too. The drop in vision may show up as dimmer brightness, a missing patch of side vision, or blurrier letters on the chart.
The reason sits in the anatomy. The retina is nerve tissue. Its inner layer of cells feeds directly into the optic nerve. Damage anywhere along that path hurts both the pupil reflex and the picture. Optic neuritis, an inflamed optic nerve, can cause sudden loss of sight. Anterior ischemic optic neuropathy, a loss of blood supply to the nerve, can cause sudden severe loss. A large retinal detachment causes painless loss of vision. All three can give an RAPD, and all three take vision down with them.
Pair the two findings in your mind. When a pupil test is abnormal, check the vision in that eye, and when one eye sees much worse, look hard for an RAPD. Report both to the ophthalmologist before you dilate. Linking pupil findings to vision is a core part of the COA pupil assessment content area.
Incorrect Answers
- B. Flashing lights point to a retinal tear or a vitreous detachment. Most causes of an RAPD, such as optic neuritis, cause no flashes at all.
- C. Redness is a surface finding of the conjunctiva, the clear skin over the white of the eye. The pupil pathway lies much deeper.
- D. Pain is not the rule here. A retinal detachment is painless, yet it can still produce a clear RAPD.
Testing Pearls
- An RAPD signals optic nerve or significant retinal damage.
- Expect reduced vision, dimmer brightness, or a field defect in that eye.
- Optic neuritis can cause sudden but reversible vision loss.
- Retinal detachment causes painless vision loss and can also produce an RAPD.
- Always test pupils before dilating drops and report an RAPD to the doctor.
References
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 8, Comprehensive Medical Eye Examination.
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 3, Abnormalities of the Eye.
