Patient History, Vision Assessment, and Diagnostic Testing
Domain 3 tests systematic history taking, accurate visual acuity, and the auxiliary tests that guide diagnosis. The exam emphasizes patient instructions, correct testing distance, documentation of method, and interpretation of screening results.
History and red flags
- Record the chief complaint in the patient's words, then expand the history of present illness: onset, duration, severity, location, quality, aggravating and relieving factors, and associated symptoms.
- Obtain ocular history, medications including over-the-counter and herbal products, allergies, family history, and social history such as smoking and diabetes.
- Urgent red flags include sudden vision loss, severe pain, chemical injury, trauma, flashes and floaters, and a curtain over the visual field. Escalate these rather than continuing routine testing.
Vision assessment
- Distance acuity uses a Snellen or ETDRS chart at 20 feet or 6 meters. Ensure correct calibration, proper occlusion, no squinting, and adequate illumination.
- Near acuity is tested at about 14 inches or 40 cm with a near card; record the card and add if used.
- Pediatric acuity may use Allen figures, HOTV, Lea symbols, Tumbling E, or preferential looking, depending on age and cooperation.
- Pinhole testing reduces the blur circle. Improvement indicates uncorrected refractive error; no improvement suggests media, retinal, or optic nerve pathology.
- Other screening includes color vision, stereoacuity, contrast sensitivity, Amsler grid, pupils, extraocular movements, and confrontation fields.
Diagnostic testing
- Visual fields require clear instructions, patch placement, fixation monitoring, and review of fixation losses and false-positive or false-negative rates.
- Ancillary tests include tonometry, pachymetry, biometry, topography, OCT, fundus photography, and fluorescein angiography. Each has preparation, contraindication, and documentation requirements.
Worked example
A patient reads 20/80 in the right eye without correction and 20/25 with a pinhole. The pinhole improvement points to an uncorrected refractive error because the small aperture blocks peripheral rays and sharpens the retinal image. Proceed to refraction. If acuity had remained 20/80 with the pinhole, further evaluation for cataract, macular disease, or optic neuropathy would be indicated. Document both values and the pinhole method.
Traps that cost marks
- Recording acuity without noting pinhole, correction, or test distance.
- Confusing 20/20 at 20 feet with 6/6 at 6 meters.
- Ignoring unreliable field indices or patient fatigue.
- Treating confrontation fields as equivalent to formal perimetry.