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ISLAMIC MEDICAL EDUCATION RESOURCES 04

0011-VISION (BASAR)

Lecture to 2nd year students on 24th November 2000-11-24 by Professor Omar Hasan Kasule, Sr.

A. CONCEPTS

QUR'ANIC TERMINOLOGY

Sight: The Qur'an uses four terms for vision: nadhar, ru'uyat, basar, and basiirat. These terms are used in the nominative, verb, and adjective forms.  They are also used interchangeably; the exact meaning can be worked out from the context. The term nadhar is used in the following verses: (p. 519-520:  2:50, 2:69, 2:259-260, 3:134, 6:99, 7:107, 7:198, 8:6, 9:127, 10:43, 15:16, 18:19, 20:97, 26:33, 30:50-51, 33:19, 37:88, 42:45, 47:20, 51:44, 56:84). The term ru'uyat is used in the following verses: (p. 517-519 2:73, 2:128, 3:13, 3:134, 3:152, 4:61, 5:31, 5:83, 6:25, 6:68, 6:75-78, 7:27, 7:143, 7:145, 8:44, 8:48, 9:127, 10:46, 10:88, 10:97, 11:70, 12:28, 12:31, 12:35, 13:12, 13:40, 16:14, 17:1, 18:17, 19:26, 20:10, 20:23, 20:56, 20:92, 21:36-37, 22:5, 23:93, 23:95, 24:43, 24:41, 26:61, 26:201, 27:10, 27:20, 27:40, 27:44, 27:88, 27:93, 28:6, 28:31, 30:24, 30:48, 30:50-51, 31:11, 31:31, 33:22, 34:27, 35:12, 35:40, 37:14, 39:21, 40:13, 40:77, 40:81, 40:84-85, 41:39, 41:53, 42:45, 43:48, 46:4, 46:24-25, 47:30, 48:29, 52:44, 53:12-13, 53:18, 53:40, 54:2, 57:20, 59:21, 63:4-5, 62:11, 68:26, 79:20, 81:23, 83:32, 90:7, 110:2. The term basar has been used in the following verses: (p. 378 6:46, 6:50, 7:47, 10:31, 11:24, 13:16, 16:78, 17:36, 20:96, 21:3, 22:46, 23:78, 24:30-31, 24:37, 27:54, 28:11, 32:12, 32:27, 40:58, 41:20, 41:22, 43:51, 46:26, 52:15, 67:3-4, 67:23, 76:2. The term basirat refers to insight, guidance with a moral or ethical connotation and was mentioned in the following verses  (p. 198 6:104, 12:108, 20:96, 22:46, 75:14).

 

Reading: The term reading, qira'at, deserves mention is discussion of sight. Humans have to see in order to read. If human knowledge and thought are limited to concrete images only, they cannot contribute to development of a sophisticated civilization. Animal societies like ants are well organized based on instinct; they cannot be creative in solving new problems. Human society would not be far above the ant society if humans were limited to concrete intelligence. The ability to read enables humans to communicate more complex abstract ideas and concepts leading to a complex civilization. It is therefore not surprising that the Qur'an, the basis of Islamic civilization and culture, started with verses on reading (96:1-5). This heralded a new civilization in which writing and reading were to play a major role. It is a paradox that the close of the 20th century CE is witnessing a return to the simpler civilization in which the image and not the concepts is what matters. The audio-visual culture uses imagery for entertainment and is less concerned with knowledge and thought. It is therefore responsible for introducing a new form of illiteracy among the youth. The commercial advertisers like this new approach because it fits easily with a hedonistic life and the consumer culture.

 

LOOKING and SEEING

A distinction must be made between looking and seeing. The former is the attempt to see whereas the latter is internalizing and understanding the image looked at. Sight involves not only the physical optical processes but also intellectual processing. Looking is a physical process involving eye muscles and the optical pathway that results in the projection of an image onto the visual cortex. Sight involves the process of perception, understanding and appreciating the image based on the physical image and previous knowledge. We learn from the Qur'an that a moral dimension is also involved in sight since different people can get different perceptions of the same visual reality depending on their moral insight. It is possible to look without seeing. It is possible to see without perception. In most normal situations looking precedes sight. The exception is in situations of visual perceptions during dream, ru'uyat manamiyat (p 516 8:43, 12:4-6, 12:36, 12:43-44, 12:100, 21:5, 37:102, 37:105, 48:27, 52:32).  Dreaming is a review of images stored in the brain rather than a new visual experience. Dreaming can also be human imagination can form vivid images in the mind that are not due to any visual process.

 

PHYSICAL SIGHT and MORAL SIGHT

Seeing can be physical, basar hissi, or moral, basar ma'nawi. The Qur'an always makes it clear what type of sight is intended from the context of the verses. Physical seeing was described in the following verses (p 195-6 6:46, 6:50, 7:47, 10:31, 11:24, 16:78, 17:36, 20:96, 21:3, 22:46, 23:78, 24:30-31, 24:37, 27:54, 28:11, 32:12, 32:27, 40:58, 41:20, 41:22, 43:51, 46:26, 52:15, 67:3-4, 67:23, 76:2). Moral sight was described in the following verses (p. 197-8 3:13, 6:104, 6:110, 7:179, 7:195, 7:201, 10:43, 11:20, 16:108, 18:26, 19:38, 20:125, 28:72, 29:38, 33:10, 37:179, 38:63, 45:23, 50:8, 51:21, 54:7, 59:2, 68:5, 68:43, 70:11, 70:44). Moral insight is perception that is superior to physical sight. It seems that moral sight helps the physical one. A person who is rightly guided may see and internalize physical phenomena that others look at without registering. Rightly guided or believing persons will see signs of Allah in physical phenomena around them whereas the unbelievers will pass by without noticing.

 

SIGHT on EARTH and SIGHT IN THE HEREAFTER

Human sight on earth is physical but is limited to some physical realities. Humans cannot see the angels, malaika, or the jinn. Allah cannot be seen on earth (p 521 2:55, 4:153, 7:143, 25:21). He is however omnipresent and sees everybody and everything (p 524 2:144, 9:94, 9:105, 20:46, 26:218, 70:7, 96:14). Sight in the hereafter, ru'uyat ukhrawiyyat, according to the Qur'an will be physical (p 519-520 2:165-167, 6:94, 10:54, 14:49, 16:85-86,18:47, 18:53, 18:49, 19:75, 20:107, 22:2, 2:12, 25:12, 28:64, 34:33, 37:55, 38:62, 39:58, 39:60, 39:75, 41:29, 42:44-45, 45:28, 46:35, 57:12, 67:27, 72:24, 76:13, 76:19-20, 79:46, 83:23, 83:35, 99:6-8, 102:6). The believers will see Allah in the hereafter (p 521 75:22-23, KS 97). The unbelievers will not be allowed to see Allah (p 520-521 3:77, 68:42-43, 83:15). The Prophet Muhammad (PBUH) on his night journey to heaven was in the presence of His Lord. Interpretations differ on whether he saw Him (KS 97) or did not see Him (KS 97). The Prophet Musa (PBUH) requested to see Allah on earth at Mount Sinai and was overwhelmed by the experience (7:143).

 

FUNCTIONS OF SIGHT

Sight is the most important sensory input. It enables humans look for food, identify enemies, avoid obstacles on the way, and carry out the multitude of activities of daily living (ADL). The eye is the window to the world bringing aesthetic pleasure and beauty to the human. It is a communication channel. There is beauty in the environment that the eye brings to humans. This beauty is one of the signs of Allah. In several verses Allah calls upon humans to use their sense of vision and their intellectual insight to see the signs of Allah in the universe. There is a diversity of shapes, colors, and movements that all testify to the power and majesty of the creator. The human body itself is a work of beauty whose marvels medical science in unraveling every day.

 

 

B. ANATOMICAL AND PHYSIOLOGICAL ASPECTS

ANATOMY OF THE EYE

The eye, ayn, was described by the Qur’an as the organ of vision (p 281-2 3:13, 7:116, 7:179, 7:19, 8:44, 11:31, 14:43, 15:88, 18:28, 20:131, 21:61, 27:40, 33:19, 36:66, 42:45, 54:37, 61:8). Each structure of the eye has important roles to play. The retina is embryo logically part of the brain. Each retina has 60 million rods and 3.5 million cones. Cones detect colour (photopic vision) whereas rods detect only shades of grey (scotopic vision). Rods act in night vision. Night hunters like owls, bats, rats, cats have only rods. The retina has the highest rate of glycolysis and oxygen consumption in the body. The cornea is the point of first contact of light with the eye. It reflects away some of the light. It also provides protection from mechanical damage and infection for the inner eye structures. The Pupils are the openings in the eyes that regulate the amount of light entering. Pupillary light reflexes enable control of the amount of light entering the eye.  Too much light will overwhelm the system and vision will not be clear. In dim light the pupils must be opened more widely to allow enough light in for adequate vision. The dilator pupillae and constrictor pupillae muscles control the diameter of the pupil and hence the amount of light entering. Orbits provide solid protection for the eyes. The eyeball is cushioned by retro bulbar connective tissue. Aqueous humor cushions the delicate eye structures. Its turnover is 6% of its volume daily. Secretion is increased by increase in capillary blood pressure. It is decreased by osmotic pressure gradient; the level of glucose is high in cases of high intra-ocular pressure. In normal circumstances there is equilibrium between secretion and resorption of aqueous humor. Tears are protective. Secretion of lachrymal fluid .. ml/day is balanced by evaporation and drainage through the lachrymal duct. Excessive tears are secreted as an emotional reflex and also on irritation. Lachrymal fluid washes away foreign bodies. It has lysozymes and secretory IgA that protect from bacterial infection. Riot police use lachrymators because of their irritant effect.

 

PHYSICS OF VISION

Light is the basis for vision. The Qur'an makes it very clear that there is no sight without light. Light is involved in the visual process and is a condition for sight (p 196 2:17, 2:20, 10:67, 17:12, 27:86, 35:19-20, 40:61). The Qur'an has described light using the terms nur, dhaw'u, and barq. Light, nur, guides those who walk in the dark (p 1273 2:20, 6:122, 57:27). Sight in the dark is not possible in the absence of light (p 1272 2:17). Light, described as dhaw'u, lights the dark leading to clarity (p. 735 2:17, 2:20, 10:5, 21:48, 21:48, 24:35, 28:71, 74:34, 79:29, 80:38, 81:18, 91:1, 91:3, 92:2, 97:5, 100:3). Lightning, barq, is a sudden burst of light energy (p. 189 2:19-20, 13:12, 30:24, 75:7). Lightning was described as both a source of light and also a cause of temporary blindness when too much sudden light overwhelms the visual system (p. 189 24:34). The Qur'an has described sources of light as the sun, shams, the moon, qamar, and the stars, nujuum. Sources of light have also been described as lamps, misbah and siraaj. The sky is decorated with lamps described as misbah (p 1124 41:12, 67:5) and siraaj (p 571 25:61, 71:16, 78:13). The sun is the major source of light energy (p 644-645 10:5, 71:16, 78:13, 91:1, 6:78, 10:5, 17:78, 18:90, 20:130, 25:45, 50:39, 71:16, 78:13). The sun's light reflected off the moon reaches the earth as moonlight, nur al qamar (p 966 10:5, 25:61, 71:16). The light of the stars guides travellers (p 1199 6:97, 16:16; p. 1283 6:97, 27:63). Darkness, dhalam, is either relative or absolute lack of light. Darkness is used in the Qur'an either physically or morally. The following verses describe darkness as a physical phenomenon (p. 756 2:17, 2:19-20, 6:1, 6:59, 6:63, 6:97, 10:27, 13:16, 21:87, 24:40, 27:63, 35:20, 36:37, 39:6, 79:29). The following verses describe darkness as a moral phenomenon (p. 757 2:257, 5:1, 6:39, 6:122, 13:16, 14:1, 14:5, 33:43, 57:9, 65:11).

 

THE VISUAL PROCESS

Visual pathway: The eye is structured such that there is no particle in the path of light. Metabolic processes are adapted for this; the retina gets ATP from anerobic glycolysis. The lens is mostly water and protein and needs little metabolism. The visual process starts with entry of the light into the eyes and image projection on the retina. The optical principles that apply in the physical world, (reflection, refraction, and energy conversion) apply in the same way in the eye. The cornea reflects away some of the incident light rays. The eye has 3 refractory surfaces: anterior surface of the cornea, the anterior surface of the lens, and the posterior surface of the lens. The ciliary muscles are involved in accommodation of the lens. Refracted rays of light converge on the retinal surface where they form an inverted image. The image is transmitted by the optical nerve to the visual part of the cerebral cortex. The process of visual transduction involves photochemical, biochemical, and electrical events. The cerebral cortex is able to reinterpret the image as reinverted. The concept of flicker vision used in cinematography also applies in human vision to enable seeing moving images. Binocular vision is a gift from Allah to humans. The human eye is unique in having a well-developed binocular vision. The visual field is the projection of the external world that is visible by the eye. Other animals may have a wider angle of vision but they cannot get the richness of all they can see because of limited cerebral processing of visual information. Binocular vision is important for judging distance by detecting differences in the images from both eyes. There is fusion of images from both retinas enabling 3-dimensional observation. Eye muscles ensure co-ordination of movements of the two eyeballs to ensure binocular vision. Light and dark adaptation are another gift to humans. The eye has both light and dark adaptation. This enables humans to make smooth transitions from light to darkness and vice versa. Humans are adapted for both day and night living unlike some animals that can only function in the day (diurnal) or the night (nocturnal).

 

COLOR VISION

Human ability to see and discriminate various colors adds to the aesthetic enjoyment of the environment. Normal vision is trichromatic ie the retina can see the 3 primary colors (red, green, blue) which are fused in the cortex to produce all the other colors.

 

EXTRANEOUS LIGHT

The melanin in the iris makes it opaque and gives color to the eyes. The black-brown colour is due to melanin pigmentation. Blue eye color is due to absorption of all wavelengths so that only blue is reflected back. Albinos have no melanin and their eyes are not colored as normal persons. Melanin in the choroid absorbs light and prevents stimulation of the retina by light reflected within the eye. The black retinal surface prevents reflection of light rays within the eyeball.

 

C. LIMITATIONS AND DECEPTION OF THE EYE

LIMITATION OF HUMAN VISION

Human vision is limited: p 197 2:7, 2:17, 6:103, 15:15, 36:9, 36:66, 45:23, 47:23, 53:17, 56:85, 69:38-39). Humans unlike other animals cannot see well in the dark (2:17). They cannot see Allah despite His omnipresence (6:103). 

 

DECEPTION OF HUMAN VISION

Human vision can be deceived for example it can see a mirage, sarab,  where no water exists(24:39, 78:20). Professional magicians can play 'visual tricks' that deceive unsuspecting humans (7:116). The modern cinematography industry relies on optical tricks and special effects to create visions that look very real to the untrained eye.

 

PERCEPTION OF SPEED

Humans cannot visually appreciate very slow or very rapid movements. The earth revolves around the sun as well as rotates on its own axis. Humans cannot see this because it occurs so slowly. Parents living continuously with their young children may not notice the rapid change in body size because it occurs relatively slowly; the occasional visitor will see the change immediately.

 

SIZE DISCRIMINATION

The discrimination of human vision is limited. Small objects cannot be seen. Very large objects cannot be appreciated if there is no background against which to compare. For example a human is easily lost in the middle of an empty desert or in the middle of the ocean.

 

VISION UNDER DIFFERENT AMOUNTS OF LIGHT

Sight in darkness or in very bright light is difficult. Humans unlike nocturnal animals cannot see well in the dark. They are also virtually blinded by very strong light such as occurs in lighting.

 

D. THE EYE AS A SEAT OF EMOTIONAL EXPRESSION

SADNESS

Sadness is a normal human emotional state (p 332-333 2:139, 9:92, 3:153, 33:51, 12:84, 20:40, 28:13, 15:88, 58:10, 9:92). The eye is often the first indicator of sadness by tearing (p 430 5:83, 9:92).

 

LACRIMATION

The Qur'an has described the shedding of tears (p. 203 9:82, 12:16, 17:109, 19:58, 44:29, 53:43, 53:60). Tears are also an expression of emotions. They may be emotions of sadness, fear, or remembrance of Allah. The Prophet shed tears when his son Ibrahim died (KS 186: Bukhari K23 B.33 & B.44 & B.45; Bukhari K.83 B.9; Bukhari K.97 B.25; Muslim K11 H.11 & H.12; Abu Daud K13 B.41 & B.44; Tirmidhi K.11 B.18; Nisai K.27 B.55 & B.59 & B63-65; Ibn Majah K.6 B.48 & B.53; Darimi K12 B.11; Muwatta K29 H.101 & H.105). Crying in salat (KS 121: Abu Daud K.2 B.156; Nisai K.13 B.18). Tearing occurs when reciting the Qur’an (KS 121: Ibn Majah K5 B.176). Tearing when remembering Allah when alone ie no other humans around (KS 122: Tirmidhi K20 B.8 &B26 &, Tirmidhi K34 B8; Nisai K25 B8; Ibn Majah K37 B19). Tearing for fear of Allah (5:83, KS 122: Bukhari K24 B16; Bukhari K81 B24; Bukhari K86 B19). All of the above are signs of consciousness of Allah, taqwah. It is also possible to pretend to cry, al tabaaki (KS 121: Ibn Majah K2 B173, Ibn Majah K27 B19).

 

PLEASURE

Eyes are also described as the seat of pleasure and happiness, qurrat 'ayn (p.281 20:40, 28:13; p. 281 19:26; p. 282 33:51). Happiness and pleasure are obvious in the eyes and are difficult to hide. The eyes as they look can be a source of pleasure, Laddhat al 'ayn (p 1040 43:71).

 

BEAUTY

The Qur'an has described beauty in heaven as beauty of the eyes (p. 282 37:48, 38:25, 55:56).

 

COMMUNICATION

Eyes can be used to show agreement/disagreement, anger, anxiety, depression, welcome and even communicate secret messages. A trained observer can tell a lot about a person's disposition by looking at the eyes.

 

E. PATHOLOGY

ACCOMODATION

As part of ageing the eye loses its ability to accommodate. Sometimes this occurs quite early in life. Emmetropia is normal refraction. Myopia is short sight due to too much refraction. Hypemetropia is long-sight due to weak refraction. Astigmatism arises when here is inequality in the curvature of the lens.  Presbyopia is progressive loss of accommodation due to decreasing elasticity of the lens. Refractory errors can be corrected by use of appropriate lenses.

 

BLINDNESS

The Qur'an has discussed blindness in both its physical and moral perspectives (p 851 2:17-18, 2:171, 5:71, 6:50, 6:104, 7:64, 10:43, 11:24, 11:28, 12:84, 13:16, 17:72, 17:9, 20:102, 20:124-125, 22:46, 24:61, 25:73, 27:66, 27:81, 28:66, 30:53, 35:19, 36:66, 40:58, 41:17, 41:44, 43:40, 47:23, 48:17, 54:37, 80:2). Blindness from the moral perspective is an internal blindness, 'amy al quluub (p 851 2:171, 5:71, 7:64, 10:43, 11:24, 13:16, 17:72, 17:9, 20:102, 20:124-125, 22:46, 25:73, 27:66, 27:71, 28:66, 30:53, 35:19, 40:58, 41:17, 41:44, 43:40, 47:23). Physical blindness of the eyes is the external blindness, amy al absaar (24:61, 48:17, 80:2). Physical sight is not much use in the presence of moral blindness that prevents correct perception of the visual impulses. Moral blindness is clearly worse than physical blindness.

 

Physical blindness can be congenital, akmah (p 851 3:49, 5:110) present at birth or acquired after birth, 'ama. Loss of sight is a great human tragedy. Loss of visual stimulation from the environment is a cause of depression. The eyes are referred to by the Prophet as the 2 dear ones and who loses sight and is patient will get great reward (KS 405: Tirmidhi K34 B58; Darimi K20 B76).

 

THE EVIL EYE

The prophet taught that the evil eye is true (KS 275: Bukhari K76 B36; Muslim K39 H41,42,59; Abu Daud K27 B15; Tirmidhi K26 B17-19; Ibn Majah K31 B32; Muwatta K50 H1-3; Ahmad V1 p. 274, 294; Ahmad V2 p.222, 289, 319, 420, 439, 487; Ahmad V4 p67; Ahmad V5 p70, p379). The prophet ordered that it be cured by ruqyat (MB #1973: Bukhari 7:628; MB #1974: Bukhari 7:635).

 

Professor Omar Hasan Kasule, Sr. November 2000