What is the ideal technique for performing a torch‑light (pen‑light) examination of the eye?

Ideal Torch (Penlight) Examination Technique for the Eye

Use a bright penlight in a darkened room with the patient fixating on a distant target to systematically assess pupillary function, external structures, and detect anterior segment pathology. 1, 2

Essential Equipment and Environment

• Bright penlight or torch is the fundamental tool for bedside ocular examination 3, 1
• Darkened room is critical for optimal pupillary assessment and detection of size differences 1, 2
• Patient should fix gaze on a distant target to eliminate near reflex and accommodative pupillary constriction 1, 2

Systematic Examination Sequence

1. External Inspection

• Assess eyelid position, character, and lashes using direct illumination 3
• Evaluate globe position and pertinent facial features 3
• Look for conjunctival hyperemia which may indicate acute pathology 3

2. Pupillary Assessment (Critical Component)

Size and Symmetry:

• Observe pupils in dim light conditions first to detect anisocoria 1, 2
• Anisocoria >1mm is clinically significant and warrants investigation 2
• Note that older adults may have 2-3mm pupils even in dim lighting (normal age-related miosis) 2

Swinging-Light Test for RAPD:

• Shine the bright penlight directly into the right eye for less than 5 seconds and observe pupillary constriction 1, 4
• Alternate the light between eyes, observing both direct and consensual responses 4
• Normal response: pupillary constriction or no change when light is directed at either eye 2
• Abnormal response: pupillary dilation when light shines on the affected eye indicates a relative afferent pupillary defect (RAPD) 1, 2, 4
• RAPD ≥0.3 log units should prompt investigation for optic nerve or retinal pathology 1, 2, 4

3. Red Reflex Examination (Brückner Test)

• Direct the penlight through the pupil from approximately arm's length to elicit the red reflex 2
• Symmetric red reflex bilaterally is normal 2
• White pupillary reflex (leukocoria) indicates serious pathology including possible retinoblastoma 2
• Lens or media opacities block or diminish the red reflection 2

4. Anterior Segment Inspection

• Use oblique illumination with the penlight to assess corneal clarity 3
• Look for corneal edema (microcystic or stromal) which appears with acute angle closure 3
• Assess anterior chamber depth by shining light from the temporal side—shallow chambers cast an iris shadow 3
• Examine for iris abnormalities including atrophy, irregular pupil shape, or mid-dilated pupil 3

5. Photophobia Testing

• The penlight test for photophobia has 60% positive predictive value and 90% negative predictive value for serious eye pathology 5
• Positive photophobia (patient discomfort with penlight) suggests uveitis or keratitis rather than simple conjunctivitis 5

Critical Clinical Caveats

Confounding Factors:

• Sedation, opioid analgesics, and neuromuscular blockade significantly impair pupillary assessment 1, 2
• Do not confuse anisocoria (difference in pupil size) with RAPD (difference in pupillary response)—these represent entirely different pathophysiologic processes 1, 2, 4

Special Populations:

• Pediatric examination is challenging due to frequent fixation shifts, focusing changes, and physiologic pupillary oscillations (hipus) 1, 2, 4
• Use developmentally appropriate targets to engage children's attention during examination 2

Technique Pitfalls:

• Avoid passing the light beam through the pupil during gonioscopic assessment as this induces pupillary constriction and widens the angle artificially 3
• Use a short (approximately 1mm) bright beam for angle assessment 3
• Never delay referral for abnormal findings—leukocoria, absent red reflex, or significant RAPD require urgent ophthalmologic evaluation 2