Pinhole visual acuity assessment is an important form of preoperative examination performed in cases with higher-order refractive error that helps to apprise the surgeon and the patient of the best possible vision that can be achieved after intraocular surgery.
The pinhole helps to filter the stray light from the periphery of the cornea in cases with higher-order corneal irregular astigmatism. Pinhole effect blocks distorted and unfocused light rays emanating from the peripheral cornea and isolates more focused central and paracentral rays through the central aperture, thereby enhancing the visual acuity and its image quality. The pinhole effect can be achieved with surgical pupilloplasty that reduces the circle of confusion on the retina and results in a sharper image.
Secondly, when the pupil is narrowed down, the entire light spectrum enters the eye through the small central pinhole pupil. According to the Stiles-Crawford effect, light that enters near the center of the pupil produces a greater photoreceptor response as compared with the light that enters through the edges of the peripheral pupillary margin. Therefore, with pinhole effect, the patient sees the object clearly and well illuminated due to greater photoreceptor sensitivity.
The video demonstrates the clinical advantage and application of performing a pinhole pupilloplasty. Amar Agarwal, MS, FRCS, FRCOphth, has graciously contributed the video to this blog wherein surgical pupilloplasty is performed with single-pass four-throw technique.