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Proper eye drop instillation is both a clinical skill for paraoptometric staff and a critical patient education topic. Even the most effective ophthalmic medication fails if it is instilled incorrectly—missing the eye, touching the tip and contaminating the bottle, or being washed away before absorption. The CPO and CPOA exams test your knowledge of correct technique, patient instruction, and medication safety principles.
Many patients—especially glaucoma patients—use multiple drops. The order and timing of instillation matters:
Free CPO and CPOA exam prep on Opterio—including drop instillation and clinical skills.
Medication categories, classes, and purposes used in optometric practice.
Dilation drops—indications, technique, and safety.
Systemic medications affecting the eye and vice versa.
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The correct technique: (1) Wash and dry hands. (2) Tilt the head back or lie flat. (3) Using the non-dominant hand, gently pull the lower lid downward to create a pocket (the conjunctival cul-de-sac). (4) Looking up or away from the bottle, hold the bottle tip 1–2 cm above the eye—do not touch the tip to the eye, lashes, or lid (contamination risk). (5) Squeeze one drop into the pocket. (6) Close the eye gently for 1–2 minutes. (7) Apply nasolacrimal occlusion (press the inner corner) to reduce systemic absorption. (8) Blot excess with a clean tissue without rubbing.
The conjunctival cul-de-sac can hold approximately 30 microliters (µL) of fluid. A standard eye drop is approximately 30–50 µL. When a second drop is instilled immediately after the first, the conjunctival pocket overflows, washing the first drop out. Additionally, some drops can interact with others if mixed together. The recommended interval between different drops is at least 5 minutes—allowing the first drop to be absorbed before instilling the next. If multiple drops are required at the same time of day, educate patients to sequence them with 5-minute intervals.
Ophthalmic ointments are thicker and require a slightly different technique: (1) Wash and dry hands. (2) Pull the lower lid down to form a pocket. (3) Squeeze a small ribbon of ointment (approximately 1 cm / ¼ inch) along the inside of the lower lid, from the inner to the outer canthus. (4) Release the lid and close the eye gently. (5) Roll the eye briefly to distribute the ointment. Ointments cause significant blurring for 20–30 minutes after instillation and are usually prescribed for nighttime use. Warn patients not to drive after instilling ointments.
Bottle contamination occurs when the dropper tip touches the eye, lashes, lid margin, or any surface. This introduces bacteria directly into the bottle, which then contaminates every subsequent dose. Once a bottle is contaminated, it can cause or worsen eye infections. Prevention: (1) Hold the bottle tip 1–2 cm above the eye, never touching. (2) Never share eye drops between patients or between individuals. (3) Discard bottles after the prescribed treatment course or after the expiration date. (4) Follow manufacturer guidance on discard time after opening (typically 28–30 days for multi-dose bottles). Paraoptometrics administer drops in the office should use single-use vials when possible.
General guidance for missed doses: if the patient remembers the same day, instill the dose as soon as possible unless it is near the time of the next scheduled dose. If it is nearly time for the next dose, skip the missed dose and continue with the regular schedule—never double up. Specific guidance varies by medication type (e.g., for chronic glaucoma drops, the doctor may give specific instructions). Paraoptometrics should reinforce this education and ensure patients know to call the office with questions about missed doses rather than guessing.
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