The Bruckner test does both jobs at once. You hold a direct ophthalmoscope back from the child and light up both eyes at the same time. You then compare the two red glows that come back out of the pupils. Anything that blocks the line of sight, such as a cloudy lens, makes that glow look dim or dark. An eye that is turned gives a glow that looks brighter than its partner. So one look screens for both problems.
The other choices judge alignment only. The Hirschberg test shines a penlight and watches where the corneal light reflex falls in each pupil. When both reflexes sit centered in the pupils, the eyes are straight. A reflex pushed toward the ear means that eye is turned in. A reflex pushed toward the nose means that eye is turned out. Every 1 mm of shift stands for about 7 degrees of turn, or 15 prism diopters. The Krimsky test adds prisms to push the off-center reflex back to the pupil center, and the prism amount is the size of the turn. Cover tests use an occluder and watch for refixation. None of these say a thing about a cloudy lens.
Think of the Bruckner test as a two-for-one screening tool. Match the two red glows for brightness, then match them for color. Knowing which alignment test does what is a core part of the COA ocular motility content area.
Incorrect Answers
- A. Hirschberg uses a penlight and reads the corneal light reflex. It screens alignment only and tells you nothing about clouding in the line of sight.
- B. Krimsky is Hirschberg plus prisms. Its job is to measure the size of a turn, not to look for a cloudy lens.
- D. The cover-uncover test uses an occluder to break fixation. It sorts a tropia from a phoria but never looks through the pupil.
- E. The Maddox rod is an accessory lens inside the phoropter. It depends on what the patient reports seeing, and it shows nothing about a clouded media.
Testing Pearls
- The Bruckner test compares both red glows at once with a direct ophthalmoscope.
- Hirschberg: centered corneal reflexes in both pupils mean the eyes are straight.
- A reflex shifted toward the ear means an in-turned eye; shifted toward the nose means an out-turned eye.
- On Hirschberg, 1 mm of shift is about 7 degrees or 15 prism diopters.
- Light reflex tests can be fooled by odd-shaped pupils, so cover testing is used whenever possible.
References
- American Academy of Ophthalmology. Ophthalmic Medical Assisting: An Independent Study Course. Chapter 9, Ocular Motility.
- 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 22, Care of Ophthalmic Lenses and Instruments.
