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Microphthalmia (Greek: μικρός, mikros, 'small', ὀφθαλμός, ophthalmos, 'eye'), also referred as microphthalmos, is a developmental disorder of the eye in which one (unilateral microphthalmia) or both (bilateral microphthalmia) eyes are abnormally small and have anatomic malformations.
Several studies have found a broad range of incidence of PVD, from 20% of autopsy cases to 57% in a more elderly population of patients (average age was 83.4 years). [4] People with myopia (nearsightedness) greater than 6 diopters are at higher risk of PVD at all ages. Posterior vitreous detachment does not directly threaten vision.
The idea that myopia was caused by the eye strain involved in reading or doing other work close to the eyes was a consistent theme for several centuries. [99] In Taiwan, faced with a staggering rise in the number of young military recruits needing glasses, the schools were told to give students' eyes a 10-minute break after every half-hour of ...
[22] [23] The upper end of the range is given in terms of normal visual performance as 10 8 cd/m 2 (100,000,000 or one hundred million candelas per square meter). [24] Dilation and constriction of the pupil. The eye includes a lens similar to lenses found in optical
Between these extremes is the pupil diameter that is generally best for visual acuity in normal, healthy eyes; this tends to be around 3 or 4 mm. If the optics of the eye were otherwise perfect, theoretically, acuity would be limited by pupil diffraction, which would be a diffraction-limited acuity of 0.4 minutes of arc (minarc) or 6/2.6 acuity.
It is used to detect and evaluate symptoms of various retinal vascular diseases and eye diseases. In patients with headaches , the finding of swollen optic discs ( papilledema ) on ophthalmoscopy is a key sign indicating raised intracranial pressure , which may be due to conditions such as hydrocephalus , benign intracranial hypertension ...
The normal range is 12–21 mm. Upper normal limit for people of African origin is a little higher, about 23–24 mm. [3] A difference greater than 2 mm between the eyes is significant. In children and teenagers mean exophthalmometric measurements increase with age: Less than 4 years old (13.2 mm), 5–8 years old (14.4 mm), 9–12 years old ...
The largest letter on an eye chart often represents an acuity of 6/60 (20/200), the value that is considered "legally blind" in the US. Many individuals with high myopia cannot read the large E without glasses, but can read the 6/6 (20/20) line or 6/4.5 (20/15) line with glasses.