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Colorblindness Glasses

Colorblindness Glasses

Colorblindness Glasses A person with red-green color blindness (more accurately called color vision deficiency) experiences the world differently because their red and green photopigments have more overlap than normal. By overlap, we mean spectral overlap, which is related to how the photopigments absorb light. Lets take a moment to understand how that happens: The photopigments are the light-absorbing molecules found in the ... Read More »

Kestenbaum’s rule (Strength of reading plus lens)

Kestenbaum’s rule (Strength of reading plus lens)

Kestenbaum’s rule (Strength of reading plus lens) Kestenbaum’s rule: used to estimate strength of plus lens required to read newspaper print without accommodation Add power = reciprocal of best distance acuity Reciprocal of add power = working distance (in meters)Example: 20/80 vision; add = 80/20 = +4.00 D; working distance = 1/4 (0.25 m) Source: Review of Ophthalmolgy Book Ophthalmology ... Read More »

iExaminer for Fundus Exams

iExaminer for Fundus Exams

iExaminer for Fundus Exams The iExaminer from Intuitive Medical Technologies in Shreveport, Louisiana is a simple iPhone 4 attachment for the popular Welch Allyn PanOptic ophthalmoscope that lets you do fundus exams and share videos and images right from the iPhone. The iExaminer app also walks users through a full eye exam including visual acuity, pupils, ocular motility, visual fields, intraocular pressure ... Read More »

Femto Lasik Adventages and Procedure Notes With Videos

Femto Lasik

Femto Lasik is a two step procedure involving two lasers. First, the surgeon creates a small flap in the cornea to prepare the eye for the next step, the vision correction. The traditional LASIK method of laser vision correction requires a mechanical blade to make the flap. However, in FEMTOLASIK method we create the flap using the FEMTO LDV™ femtosecond laser. ... Read More »

Entoptic Phenomenon Notes

The blue field entoptic phenomenon or Scheerer's phenomenon

Entoptic Phenomenon Definition: are visual effects whose source is within the eye itself. (Occasionally, these are called entopic phenomena, which is probably a typographical mistake.) ENTO=WITH IN , OPTIC= EYE, ENTOPTIC=WITH IN THE EYE In Helmholtz’s words; “Under suitable conditions light falling on the eye may render visible certain objects within the eye itself. These perceptions are called entoptical.” Entoptic images have a physical basis ... Read More »

Retinoscope and Retinoscopy Notes


Retinoscope  Definition: A retinoscope is an instrument used to objectively determine the refractive power of the eye. It works by allowing the examiner to project a beam of light into the eye and then observe the light as it is reflected back out of the eye.  The emerging light will change as it passes through the optical components of th eye, ... Read More »

Focimeter (Lensmeter) Notes


Focimeter Definition: An ophthalmic instrument. It is mainly used by optometrists and opticiansto verify the correct prescription in a pair of eyeglasses, to properly orient and mark uncut lenses, and to confirm the correct mounting of lenses in spectacle frames. Lensmeters can also verify the power of contact lenses, if a special lens support is used. Focimeter Components: A simple lensmeter cross sectional view. 1 – Adjustable eyepiece 2 – ... Read More »

Synoptophore Notes


Synoptophore Definition: This is an Ophthalmic Instrument, used for diagnosing imbalance of eye muscles and treating them by orthoptic methods. Synoptophore Uses: All the standard measurements and treatments are possible on this instrument including assessment of the angle alpha, the objective angle, abnormal retina correspondence, cyclophoria, hyperphoria and horizontal vertical vergences. Synoptophore Components: An automatic flashing unit allows each eye ... Read More »

Haidinger’s brush Notes

Haidinger's brush

Haidinger’s brush appears on computer screens and blank areas of sky, and it’s caused by the way our eyes respond to polarized light. The apparition looks like two fuzzy bowties, a blue one and a yellow one, overlapping each other at 90 degrees. The rendering above simulates the effect, but it actually appears smaller, about the size of your thumb extended ... Read More »

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