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2. Pinhole occluder - Wikipedia

   en.wikipedia.org/wiki/Pinhole_occluder

   A pinhole occluder is an opaque disk with one or more small holes through it, used by ophthalmologists, orthoptists and optometrists to test visual acuity. The occluder is a simple way to focus light, as in a pinhole camera, temporarily removing the effects of refractive errors such as myopia. Because light passes only through the center of the ...

3. List of screw and bolt types - Wikipedia

   en.wikipedia.org/wiki/List_of_screw_and_bolt_types

   A bolt that is threaded all the way to the head. An ASME B18.2.1 compliant set/tap bolt has the same tolerances as an ASME B18.2.1 compliant hex cap screw. set screw: grub screw: A set screw is generally a headless screw but can be any screw used to fix a rotating part to a shaft, such as a line shaft or countershaft. The set screw is driven ...

4. Set screw - Wikipedia

   en.wikipedia.org/wiki/Set_screw

   In American English, a set screw is a screw that is used to secure an object, by pressure and/or friction, within or against another object, such as fixing a pulley or gear to a shaft. [ 1 ] [ 2 ] A set screw is normally used without a nut (which distinguishes it from a bolt ), being screwed instead in a threaded hole drilled in only one of the ...

5. List of screw drives - Wikipedia

   en.wikipedia.org/wiki/List_of_screw_drives

   Tamper-resistant versions with a pin in the recess are available. Metric sizes of the hex socket are defined by ISO 4762 (socket head cap screws), ISO 4026 (socket set screws with flat point), ISO 4027 (socket set screws with cone point), ISO 4028 (socket set screws with dog point), and ISO 4029 (socket set screws with cup point).

6. Robertson screw - Wikipedia

   en.wikipedia.org/wiki/Robertson_screw

   [3]: 85–86 They also allow the use of angled screwdrivers and trim-head screws. The socket-headed Robertson screws are self-centering and reduce cam out. They also stop a power tool when set, and can be more easily removed if painted over, or old and rusty. [3]: 85–86 In industry, they speed up production and reduce product damage.

7. Subjective refraction - Wikipedia

   en.wikipedia.org/wiki/Subjective_refraction

   An occluder is placed over the eye that is not being tested (e.g.: over the left eye, to test the right eye's vision). A pinhole occluder is then placed before the patient's eye, and their vision is then tested again (each eye separately) to determine if the patient's poor visual acuity is a result of optical irregularities, or pathological issues.