Скачать или смотреть Lecture-22: Sheard's Criteria: Prescribing Prism for Exophoria | Optometry Exams | AIIMS RRB DHA MOH

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Master Sheard's Criterion for prescribing prism! This is the most widely used rule for prescribing prism in cases of Exophoria. In this video, we calculate the exact amount of prism needed for a patient with High Exophoria and Low Positive Fusional Vergence (PFV).

The Rule:
Sheard's Criterion states that the Compensating Fusional Vergence (Reserve) should be at least twice the Phoria (Demand) to be comfortable.
• Formula: Prism = 2/3 Phoria – 1/3 Compensating Vergence.
• For Exophoria: The compensating vergence is PFV (Base Out ranges).

We use the Blur point (or Break if Blur is not seen).
• Direction: Exophoria is corrected with Base In (BI) prism.

In this Video:
• Phoria = 9 Exophoria.
• Reserve (PFV Blur) = 6 Prism
• Calculation: 6 - 2
• Answer: 4 Prism Base In.

👇 Homework Question:
If a patient has 12 prisms of exophoria for near and their near PFV and NFV Blur/Break/Recovery values are 12/14/10 and 10/16/12, what is the prism required according to Sheard's Criteria?

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