Abstract:- Eyeglasses are used to treat eyesight issues. Glasses can be useful if patient has problems seeing clearly, either close or at a distance. They enhance patient’s ability to see items clearly and precisely from any distance. The majority of vision issues have to do with how light focuses on the retina. The retina is located close to the optic nerve in the back of the eye. The retina receives light from the lens of the eye and transforms it into signals before sending them to the brain. The visuals we perceive are produced by this process. Eyeglasses help focus the light appropriately on the retina. Patient may need glasses for problems such as:
Nearsightedness (myopia): Patient see close objects clearly, but objects farther away look blurry.
Farsightedness (hyperopia): Objects in the distance look clear, while things close by look blurry.
Astigmatism: A problem with the shape of cornea causes blurry or distorted vision.
Presbyopia: patient eyes begin to lose the ability to focus on nearby objects (an age-related condition).
Typically, glasses are worn to correct eyesight, such as with reading glasses and nearsightedness glasses. So it is important to know about the history of eye glasses and also role of ancient India for inventing glasses.
Keyword:- Upa netra, Eye glasses, Presbyopia, Refractive Error.
Introduction:- A sort of vision issue that makes it challenging to see clearly is refractive error1. They take place when patient eye's shape prevents light from properly focusing on retina.
HYPERMETROPIA(LONG-SIGHTEDNESS)2:-It is the refractive error, in which the incident parallel rays of light are brought to a focus posterior to the light-sensitive layer of the retina, when the accommodation is at rest.
Etiology3
1) Axial hypermetropia is by far the most common.In fact, all the newborns are almost invariably hypermetropic (approx 2.5D). This is due to shortness of the globe and is physiological.
2) It may also occur pathologically, when retina is displaced forward [retinal detachment, central serous retinopathy (CSR), orbital tumors, retinal tumor etc.]
3) In microphthalmos or nanophthalmos (where the axial length is less than 20.0 mm), there is high hypermetropia.
4) Curvature hypermetropia as in cornea plana, following a corneal injury, lens plana, etc.
5) Index hypermetropia due to increase in refractive index of the lens-cortex in old age.
6) Removal of the lens (aphakia).
MYOPIA (SHORT-SIGHTEDNESS)
It is that dioptric condition of the eye in which, incident parallel rays come to a focus anterior to the light sensitive part of the retina, when accommodation is at rest4.
Etiology5
1) Axial myopia: When the axial length is more.
2) Curvature myopia: When the curvature of the cornea or lens is more, e.g. kerato-conus, keratoglobus or megalocornea, and lenticonus.
3)Index myopia: Nuclear sclerosis and in diabetes (as the index of nucleus is more).
4) Forward displacement of the lens.
ASTIGMATISM6
It is the type of refractive error, in which the incident parallel rays do not come to a point focus upon the retina, due to refraction varies in different meridians of the eye.
Etiology7
1)Curvature astigmatism
• Corneal
• Lenticular: As in lenticonus.
2) Diseases of the cornea
Pterygium
Keratoconus
Marginal degeneration
Corneal scar
3)Index astigmatism: In early cataract, due to inequalities of refractive index in different sectors
4) Subluxation of the crystalline lens
5) Decentration or tilting of the IOL.
Presbyopia: patient eyes begin to lose the ability to focus on nearby objects (an age-related condition).
healthcare provider will figure out the best lens for patient based on the vision problem patient have. Lenses can treat:
Nearsightedness: A concave lens (curves inward).8
Farsightedness: A convex lens (curves outward).9
Astigmatism: A cylinder-shaped lens.10
Presbyopia: Bifocal or multifocal lenses.11
History of glasses in world :- J. William Rosenthal, MD, has documented in his scholarly book, "Spectacles and Other Vision Aids." That Italy is where the first spectacles were created. Name of the inventor is unknown . The original design for spectacles included a frame to hold the right and left spectacle cell had a rivet [swivel motion] attached to a small strut to hold the two lenses together. A space was made between them to slide over the nose. The lenses were probably made of clear quartz [pebble quartz] or beryl [sea green stone of beryllium aluminum silicate] and due to their curved surface, they demonstrated some ability to magnify an object of regard.
History of glasses in India:-
Upa Netra :-
Etymology
दृष्टिदोषदूरीकरणार्थे उपयुक्तमुपकरणम् उपनेत्रम् अस्ति12
Reference of upa netra in different ancient text
1) In Netra Prakashika book written by Nandikeshvara clearly described about presbyopia. There author clearly described that “the pitta dosha supports our body for the first fourty years. The same pitta will reach the light (jyoti) of both the eyes and main maximum illumination (mahaprakasha) to provide clear of the distant objects. But the vision reduces for near objects (presbyopia?). For the improvement of near vision, he will be in need of upanetra (spectacles?) This is declared as paityakopa by Lord Mahadeva13
2) Adi Sankaracharya (509 – 477 BCE) has used the term "Upanetra," Sankara wrote in the 81st verse of "Aparokshanubhuti" (Direct Experience), "Just as all very small objects appear to be large when viewed through lenses, so does one, etc."This indicates that either lenses or magnifying glasses were used in India to magnify objects or letters. The context of upanetra in the above text makes it clear that some sort of magnifying lens or spectacles were used suggests that some lens were used to help eyes view better and bigger14.
3) In Sanskrit, spectacles known as Upalocanagolaka (circular spectacles) or Upanetra were worn by middle-class people in addition to the upper classes15.
4) A poem in Gujarati called "Casimasabda-Satarthi-Svadh-yaya" that was written in about 1576 CE by the Jain poet Somavimalasuri of Ahemdabad contains a mention of the spectacles.The term used in this sentence, chasima or chasma, is comparable to the Persian word chashm, which means an eye16.
5) It is clear that spectacles were invented in India, most likely by the Kannada-speaking Hindus, according to Devanarayan's account (between 1344 and 1353 CE), Vyasaraya's use of spectacles (1520 CE), the indigenous production of spectacle lenses in South India, the different terms used for spectacles in North and South Indian languages, and other historical facts17.
6) Therefore, it is most likely that the Arabs brought Hindu mathemetics and the ophthalmological writings of the ancient Indian surgeon Susrutha, who conducted the first cataract surgery, to Europe18.
7) Without any visual aids, ancient Indians used to cut diamonds into tiny pieces. Before South Africa made the discovery of diamonds in 1886 CE, India was the sole known supplier of the gemstone19.
8) According to a Vedic text called Satapatha Brahmana, Takshasila University educated students from nearby nations like Russia, China, Greece, Thailand, and others how to create glass20.
9) In India, pinhole glasses were first utilised thousands of years ago21.
Principle of pin hole glasses :-
Each pinhole permits only a narrow beam of light to reach the eye. The light passes only through the centre of the lens of the eye.
So any defects of the eye lens will not take effect while the light is targeted in that way.
Conclusion:- In spite of such facts, the glory of ancient India is dismissed as fiction by some. Destruction of idols and temples, burning of innumerable books in the form of Palmyra leaves, destruction of Gurukuls (ancient residential schools) and banning study of Sanskrit language through which the culture of India has been preserved has made us today aliens to our own culture and adopt some non-native cultures.
Ancient sages disseminated knowledge only to the deserving disciples as knowledge is power and power in the hands of the undeserving will harm society. Being spiritual persons they were not after name or fame. For the benefit of common people they disseminated their knowledge through Itihasas, Poetic Dramas and Poetry. Poetry which is metrical has rhythm which does not allow any omissions or alterations. Thus interpolations are prevented and purity of original text is protected. History was not written separately but it was incorporated in the form of a story in poetry. The Ramayana and The Mahabharata are called Itihasas. The word ‘itihasa’ means ‘this happened’. But the modern western educated mind sees History as a separate subject from Literature. But in the Indian context Literature had been an expression of all knowledge including History. History is interwoven in almost all the classics of ancient Indian literature. Without understanding this we started believing in western scientists who discovered some of the things in recent years to be the discoverers of things. Now some who are interested in clearing the ground are studying available Sanskrit texts and are bringing facts to light. This may take quite some time but ultimately truth has to and will prevail.
Reference:-
1) samar k basak , Essential of ophthalmology, 6th edition, jaypee publication, page-12
2) samar k basak , Essential of ophthalmology, 6th edition, jaypee publication, page-67
3) samar k basak , Essential of ophthalmology, 6th edition, jaypee publication, page-69
4) samar k basak , Essential of ophthalmology, 6th edition, jaypee publication, page-74
5) samar k basak , Essential of ophthalmology, 6th edition, jaypee publication, page-67
6) samar k basak , Essential of ophthalmology, 6th edition, jaypee publication, page- 70
7) samar k basak , Essential of ophthalmology, 6th edition, jaypee publication, page-75
8) samar k basak , Essential of ophthalmology, 6th edition, jaypee publication, page-84
10) Dr.uday Shankar, Netra Parikashika, 1st edition, Chaukhambha visvabharati publication, page-107