The preliminary testing protocol is the standardized sequence of tests and measurements a CPO performs before the optometrist or ophthalmologist sees the patient. This data gives the physician a comprehensive baseline from which to conduct the examination, and it alerts staff to findings that may change the urgency or direction of the visit.
1. Case History
The case history is the foundation of the visit. A thorough history includes:
- Chief complaint: The primary reason for the visit in the patient's own words.
- History of present illness (HPI): Duration, onset, character, aggravating/relieving factors, associated symptoms, and prior treatment.
- Ocular history: Previous eye conditions, surgeries, injuries, contact lens use, and prior glasses.
- Medical history: Systemic conditions that affect the eye (diabetes, hypertension, autoimmune diseases).
- Medications: Systemic and topical eye medications, including any blood thinners, steroids, or antimalarials (hydroxychloroquine monitoring).
- Family history: Glaucoma, AMD, retinal detachment, strabismus, and other hereditary conditions.
- Allergies: Drug and environmental allergies, noting the type of reaction.
2. Visual Acuity
Visual acuity (VA) is measured for distance (typically 20 feet or 6 meters) and near, with the patient's current correction if any:
- Test each eye separately, right eye first by convention, then both eyes together.
- Standard notation: 20/20 (normal), 20/200 (legal blindness threshold), etc.
- If the patient cannot read the largest line, test at closer distances (e.g., 10/200) or use counting fingers (CF), hand motion (HM), light perception (LP), or no light perception (NLP) notation.
- Pinhole VA is measured when regular VA is reduced; improvement with pinhole suggests a refractive cause.
3. Color Vision Testing
Color vision testing detects color deficiencies, which can be congenital (most commonly red-green deficiency in males) or acquired (from optic nerve or macular disease).
- Ishihara plates: The most commonly used screening test. Patients identify numbers hidden within colored dot patterns. Pseudoisochromatic plates screen for red-green deficiency.
- Hardy-Rand-Rittler (HRR) plates: Screen for both red-green and blue-yellow deficiencies.
Acquired color deficiency from optic nerve disease typically affects blue-yellow discrimination, while congenital defects typically affect red-green. Hydroxychloroquine toxicity monitoring often includes color vision testing.
4. Confrontation Visual Fields
Confrontation visual fields are a quick bedside screen for gross visual field defects. The examiner sits facing the patient and presents fingers or a target in different quadrants of the peripheral visual field, asking the patient when they see the stimulus. Confrontation fields can detect large defects (hemianopias, altitudinal defects) but miss subtle losses that automated perimetry would detect.
5. Cover Test
The cover test assesses ocular alignment:
- Cover-uncover test: Cover one eye and observe the uncovered eye for movement. If the uncovered eye moves to pick up fixation, a tropia (constant misalignment) is present. Repeat for the other eye.
- Alternating cover test: Alternately cover each eye and observe the eye being uncovered for refixation movement. Detects both tropias and phorias (latent misalignment that is only apparent when fusion is interrupted).
6. Pupil Assessment
Pupil assessment includes:
- Direct and consensual response: Light in one eye should cause that eye to constrict (direct) and the other eye to constrict (consensual).
- Swinging flashlight test (RAPD): Alternately shine a light in each eye to detect an afferent pupillary defect, which indicates optic nerve or significant retinal dysfunction on the side that dilates when illuminated.
- Accommodation response: Pupils should constrict when focused on a near target.
Key Takeaways
- The case history establishes the chief complaint, ocular and medical history, medications, family history, and allergies before the exam.
- VA is tested each eye separately (right first), with and without correction; sc means without correction, cc means with correction.
- The cover-uncover test detects tropias; the alternating cover test detects both tropias and phorias.
- A RAPD on the swinging flashlight test indicates optic nerve or significant retinal dysfunction on the affected side.
- Preliminary testing data frames the physician's examination and alerts staff to findings that require urgent escalation.