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Topic: Crystalline lens

	The Crystalline Lens
		The crystalline lens is composed of 4 layers, from the surface to the center:
		This adjustment in lens shape, to focus at various distances, is referred to as “accommodation” or the “accommodative process” and is associated with a concurrent constriction (decrease in size) of the pupil.
		This normal condition is known as “presbyopia,” and it is due both to a lessening of flexibility of the crystalline lens and to a generalized weakening of the ciliary muscle which causes the lens to accommodate (change focus).
	www.tedmontgomery.com /the_eye/lens.html (3032 words)

	Lens
		The crystalline lens is a biconvex cellular optical organ which is suspended from the ciliary body by zonules.
		Subluxation of the lens (movement of the lens behind the iris plane) is common, which may cause secondary glaucoma.
		From increased accumulation of sorbitol, fructose, and glucose in the lens.
	www.nova.edu /~kimreed/LENS.html (1702 words)

	Agarwal's Eye Hospital - Books (Site not responding. Last check: 2007-11-07)
		The adult crystalline lens measures approximately 9.6 ±0.4 mm in diameter with an approximate anterior-posterior diameter of 4.2 ±0.5 mm.
		The thickness of the lens decreases from the normal 4.5 mm to practically zero, whereas the equatorial circumference of the lens extends laterally, increasing from the normal diameter of 9.5 mm to a new diameter of approximately 10.5 mm.
		The crystalline lens is a unique transparent, biconvex intraocular structure that lies in the anterior segment of the eye, suspended radially at its equator by the zonular fibers and ciliary body between the iris and the vitreous body.
	www.dragarwal.com /book-excerpt.html (7302 words)

	Vision In Focus
		Astigmatism — A common form of visual impairment in which part of an image is blurred, due to an irregularity in the curvature of the front surface of the eye, the cornea.
		Crystalline lens — A transparent, colorless body located in the front third of the eyeball, behind the iris, that helps bring rays of light to a focus on the retina.
		Presbyopia — The natural crystalline lens of the eye loses its ability to “accommodate,” meaning its ability to switch from seeing objects at a distance (one focal point) to seeing near objects (second focal point).
	www.visioninfocus.com /030.asp (850 words)

	Dental Plan from AmeriPlan® - Vision Terms
		Aphakic Lens: Eyeglass lens that are prescribed for those who have had the crystalline lens of the eye removed during cataract surgery or those born without a crystalline lens.
		To correct astigmatism with eyeglass lenses, the lens must be ground with two different curvatures, a sphere and a cylinder, so that it exactly cancels the distortion produced by the cornea or lens.
		The power in the upper portion of the lens is for viewing distant objects, whereas the power in the lower portion of the lens is for viewing close objects.
	www.idealdentalplan.com /visionterms.htm (4439 words)

	SurfWax: News, Reviews and Articles On Crystalline Lens
		The medical term is presbyopia, a hardening of the crystalline lens, and it's becoming more common as a nation of aging baby boomers start squinting their way through dinner menus.
		Cataract surgery is the removal of the clouded natural lens and replacement of it with an artificial crystalline lens.
		Curable cataracts, lack of crystalline lens, ametropia and preventable corneal opacity, some eyeball diseases and pathological changes of yellow spots are currently the major eye diseases and factors that lead to blindness among the people in Tibet, according to the survey...
	news.surfwax.com /anatomy/files/Crystalline_lens_anatomy.html (392 words)

	Clear Crystalline lens Replacement - Visions Eye and laser Clinic
		Due to the improvement in crystalline lens replacement techniques, this option is becoming increasingly popular among the international ophthalmological community.
		In the case of cataract, the diseased crystalline lens is replaced through the same technique.
		Once the lens has been placed in the eye, the patient will find that they still have to wear glasses for reading, as the lens can only focus at one distance, and is not able to change its shape like the human lens.
	www.lasik.co.za /RefractiveSurgery/SurgicalOptions/ClearCrystalline.htm (1205 words)

	eMedicine - Presbyopia: Cause and Treatment : Article by Ronald Schachar, MD, PhD (Site not responding. Last check: 2007-11-07)
		Helmholtz attributes the universal linear decrease in the amplitude of accommodation with age to hardening of the crystalline lens.
		Since the crystalline lens is denser than water and vitreous, when the anterior and posterior zonules are relaxed, the crystalline lens equator can only move toward the temporal sclera by an active generated force (eg, by the pull of the equatorial zonules).
		The crystalline lens remains stable because the anterior zonules maintain the same position on the anterior crystalline lens surface even though the crystalline lens equator is enlarging with increasing age.
	www.emedicine.com /oph/topic723.htm (4666 words)

	Glossary of Vision Terms (Site not responding. Last check: 2007-11-07)
		Accommodation : the involuntary act of the eyes' crystalline lens to help focus on objects nearby; aging of the crystalline lens causes a reduced accommodative ability called "presbyopia"; loss of near vision as we age.
		The aging of the lens is likely due to the free radical damage caused by ultraviolet light.
		Crystalline lens : natural lens found inside the eye, responsible for viewing something nearby ("accommodation" above); place where cataracts form; its failure is responsible for the condition called presbyopia.
	www.slmseniors.com /library/glossary.htm (524 words)

	Handbook of Ocular Disease Management - Crystalline Lens Subluxation
		Anytime the crystalline lens displaces, there is always the possibility that the lens can come into apposition with the back surface of the iris (or the front surface of the iris during complete lens dislocation into the anterior chamber).
		If the lens has already spontaneously dislocated into the anterior chamber, or where the patient was dilated with subsequent anterior dislocation, follow this protocol: Recline the patient (who can be dilated, if the dislocation happened spontaneously), then carefully manipulate the head until the lens falls back into place in the fossa.
		The mere fact that a lens is subluxed is not sufficient reason to surgically extract the lens.
	www.revoptom.com /handbook/oct02_sec4_1.htm (910 words)

	Glossary of contact lens, contacts and contact lenses related words and phrases.
		Aqueous - the liquid contained in the anterior chamber of the eye; it is produced by the ciliary body behind the iris, and flows through the pupil into the anterior chamber before draining away at the anterior chamber angle, around the periphery of the iris at its junction with the cornea.
		Cataract - a clouding of the crystalline lens of the eye or its surrounding transparent membrane, obstructing the passage of light and causing a reduction in vision.
		Crystalline lens - the natural lens of the eye, a transparent structure suspended behind the iris; focuses light rays on the retina and changes shape to change the focus of the eye for different distances.
	www.wwwcops.com /glossary.htm (2898 words)

	Gordon Binder Weiss Vision Institute - Clear Lens Exchange
		RLE removes the focusing lens in the eye, the crystalline lens, and replaces it with an artificial lens of a different power.
		In modern cataract surgery, the clouded crystalline lens or cataract is removed through a very small incision and replaced with an artificial lens implant.
		During the procedure a small lens is placed in front of the natural lens in your eye thus allowing the natural tens in your eye to focus on distance and near while the implant lens takes care of any refractive error (nearsightedness, farsightedness and astigmatism).
	www.gbwvision.com /pages/clearlens.html (933 words)

	eMedicine - Myopia, Phakic IOL : Article by Arun Verma, MD (Site not responding. Last check: 2007-11-07)
		In all phakic IOLs, increased crystalline lens size with increasing age and cataract formation leading to a decrease in the depth of the anterior chamber and crowding in the posterior chamber tend to exaggerate the pathologic processes.
		An iris claw lens is attached to the peripheral anterior surface of the iris by pushing a fold of the iris into the 2 claws of the lens.
		The haptic of the lens in the periphery is 0.18 mm.
	www.emedicine.com /oph/topic668.htm (10060 words)

	AllRefer.com - lens, in optics (Physics) - Encyclopedia
		lens, device for forming an image of an object by the refraction of light.
		In its simplest form it is a disk of transparent substance, commonly glass, with its two surfaces curved or with one surface plane and the other curved.
		The lens of the eye is known as a crystalline lens.
	reference.allrefer.com /encyclopedia/L/lens.html (174 words)

	Intraocular Lens Surgery (Site not responding. Last check: 2007-11-07)
		The intraocular lens surgery is currently the ideal technique for the correction of severe cases of myopia or hyperopia.
		Formerly, the surgery of the crystalline lens was made under general anaesthesia requiring a stay at the hospital.
		The crystalline lens is removed and replaced with a plastic lens with the appropriate power calculated depending on the state of vision of the patient.
	www.cvgregoire.com /eng/lens.html (291 words)

	Review of Ophthalmology
		Implantation of the Verisyse phakic lens, which is clipped to the front of the iris, has triggered iris pigment dispersion in some eyes.
		This is a key to avoiding crystalline lens contact with the IOL, and making sure the IOL doesn't push the iris too far forward, causing aqueous outflow problems.
		"I'm talking about lens width and vault, the clearance between the lens and the endothelium, and what I call the crystalline lens rise--the distance between the anterior pole of the crystalline lens and a hypothetical line connecting the 3 and 9 o'clock angle recesses at the iris root," he says.
	www.revophth.com /index.asp?page=1_668.htm (1084 words)

	Presbyopia Near Vision Reading Glasses Surgery Contact Lens Implants
		Presbyopia is a loss of flexibility of the crystalline lens of your eye that causes a gradual progressive decrease in focusing ability.
		The necessary near vision testing involves the presentation of various lens combinations and measuring the effect on the clarity of your near vision as increasing and decreasing size print is moved closer and further away.
		In these cases it is obvious that in order to achieve clear vision, the crystalline lens must be removed-and to achieve concurrent far and near vision, it is most beneficial to replace the natural lens with a presbyopia correcting multifocal intraocular lens or accommodative intraocular lens.
	www.seewithlasik.com /docs/presbyopia/presbyopia.php (1824 words)

	crystalline lens (Site not responding. Last check: 2007-11-07)
		...of cumulative injury to the crystalline lens of the eye.
		The clear front portion of the eye (cornea) and the eye's natural crystalline lens also bend light rays to achieve focus.
		Similar in function to a camera lens, the eyeÂ’s crystalline lens is located directly behind the colored portion of the eye.
	www.eyesightworks.com /crystallinelens (537 words)

	USAEyes.org - Lenticular Astigmatism and LASIK, IntraLASIK, PRK, LASEK, Epi-LASIK, RLE, P-IOL, CK, etc
		Lenticular astigmatism means that the natural crystalline lens of the eye is not perfectly symmetrical front and back, but the crystalline lens is misshaped similar to the back of the spoon example.
		It is currently impossible to correct lenticular astigmatism at the crystalline lens without removing the lens and replacing it with a new plastic or silicone intraocular lens (IOL).
		If the patient has lenticular astigmatism and the lenticular astigmatism is corrected at the cornea, then when the crystalline lens is replaced with an IOL for RLE or cataract surgery, the corneal correction that includes the correction for the lenticular astigmatism becomes an "overcorrection" at the cornea.
	www.usaeyes.org /faq/subjects/lenticular_astigmatism.htm (615 words)

	Overview
		Next, the light passes through the crystalline lens, which is located immediately behind the iris and the pupil.
		This is due to a lessening of flexibility of the crystalline lens, as well as to a weakening of the ciliary muscles which control lens focusing, both attributable to the aging process.
		Among the most important components of the human eye are the cornea, conjunctiva, iris, crystalline lens, vitreous humor, retina, macula, optic nerve, and extraocular muscles.
	www.tedmontgomery.com /the_eye/overview.html (839 words)

	Beverly Hills Vision Correction Surgery
		Nearsightedness occurs because the cornea and the crystalline lens together have too much focusing power for the length of the eye.
		If the cornea and the crystalline lens had less combined focusing power, or if the eye were shorter, then the light rays would be focused precisely onto the retina.
		If the cornea and the crystalline lens had more combined focusing power, or if the eye were longer, then the light rays would be focused precisely onto the retina.
	www.castervision.com /visionproblems.htm (485 words)

	How the natural human crystalline lens filters blue light
		During the natural aging process, the human crystalline lens gradually becomes yellow.
		Because of the patented yellow chromophore used on the AcrySof
		Natural IOL, it approximates the light transmission of a healthy adult human crystalline lens unlike foldable UV-absorbing IOLs that do not closely match the light-transmission spectrum of the human crystalline lens.
	www.cataractsurgery.com /us/professional/natural/humanlens.asp (163 words)

	Intacs (Site not responding. Last check: 2007-11-07)
		In some patients with high levels of nearsightedness or farsightedness, the natural crystalline lens is replaced with an IOL prior to the development of a cataract.
		In Phakic IOL surgery, an intraocular lens is inserted into the eye without removal of the natural crystalline lens.
		The advantage of retaining the natural lens in intraocular lens surgery is to maintain the ability to accommodate (focus on objects at different distances).
	www.uvcenters.com /refractive/intraocular.html (728 words)

	Journal of Vision - Presbyopia and aging in the crystalline lens, by Glasser (Site not responding. Last check: 2007-11-07)
		However, there are significant age changes in the crystalline lens that contribute to the progression of presbyopia.
		The human crystalline lens gradually loses the ability to undergo accommodative changes with mechanical stretching and fails to undergo accommodative changes in focal length after 60 years of age.
		Together, this data shows that although age changes occur in the accommodative structures outside of the lens, the age changes that occur in the primate lens contribute significantly to the progression of presbyopia.
	www.journalofvision.org /3/12/22 (281 words)

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