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Lecture to 2nd year medical students by Prof Omar Hasan Kasule, Sr. at the Kulliyah of Medicine, International Islamic University, Kuantan, Malaysia on 25th September 1999.
OUTLINE
1.0 CONCEPTS
A. Qur'anic terminology
B. Looking and seeing
C. Physical sight and moral sight
D. Sight on earth and sight in the hereafter
E. Functions of sight
2.0 ANATOMICAL AND PHYSIOLOGICAL ASPECTS
A. Anatomy of the eye
B. Physics of vision
C. The visual process
D. Color vision
E. Extraneous light
3.0 LIMITATIONS AND DECEPTION OF THE EYE
A. Limitation of human vision
B. Deception of human vision
C. Perception of speed
D. Size discrimination
E. Vision under different amounts of light
4.0 THE EYE AS A SEAT OF EMOTIONAL EXPRESSION
A. Sadness
B. Crying
C. Pleasure
D. Beauty
E. Communication
5.0 PATHOLOGY
A. Accommodation
B. Blindness
C. Local Diseases
D. Systemic Diseases
E. The Evil Eye
1.0 CONCEPTS
A. QUR'ANIC TERMINOLOGY
The Qur'an uses three 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).
The term reading, qira'at, deserves mention is discussion of sight. If human sight is limited to concrete images only, it can not contribute to development of a sophisticated civilization. Animal societies like ants are well organized based on instinct; they can not 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 and its use of imagery for entertainment and less information and thinking is introducing a new form of illiteracy. The commercial advertisers like this new approach because it fits easily with a hedonistic life and the consumer culture.
B. 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 is 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 sight is preceded by looking except 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.
C. 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.
D. SIGHT on EARTH and SIGHT IN THE HEREAFTER
Human sight on earth is physical but is limited to some physical realities. Humans can not see the angels, malaika, or the jinn. Allah can not 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 erarth and was overwhelmed by the experience (7:143).
E. 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. 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.
2.0 ANATOMICAL AND PHYSIOLOGICAL ASPECTS
A. ANATOMY OF THE EYE
The eye: The Qur'an has described the eye, 'ayn, 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: The retina is embryologically part of the brain. Each retina has 60 million rods and 3.5 million cones. Cones detect clour (photopic vision) whereas rods detect only shades of gray (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: 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: Pupillary light reflexes enable control of the amount of light entering the eye. Too much light will overwhlem 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: Orbits provide solid protection for the eyes. The eyeball is cushioned by retrobulbar connective tissue.
Acqeous humour 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 intre-ocular pressure. In normal circumstances there is an equilibrium between secretion and resorption oc acqeous humor.
Tears: tears are protective. Secretion of lacrymal fluid .. ml/day is balanced by evaporation and drainage through the lacrymal duct. Excessive tears are secreted as an emotional reflex and also on irritation. Lacrymal fluid washes away foreign bodies. It has lysozymes and secretory IgA that protect from bacterial infection.
B. 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).
Types of light: 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).
Sources of light: The 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 moon light, nur al qamar (p 966 10:5, 25:61, 71:16). The light of the stars guides travelers (p 1199 6:97, 16:16; p. 1283 6:97, 27:63).
Darkness, dhalam, is either relative or absolute. 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).
C. 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.
Visual process: 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 re-inverted.
Motion: The concept of flicker vision used in cinematography also applies in human vision to enable seeing moving images.
Binocular vision: 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 can not 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 eye-balls to ensure binocular vision.
Light and dark adaptation: 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).
D. COLOR VISION
Human ability to see and discriminate various colors adds to the esthetic 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.
E. EXTRANEOUS LIGHT
The melanin in the iris makes it opaque and gives color to the eyes. The black-brown color 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 eye ball.
3.0 LIMITATIONS AND DECEPTION OF THE EYE
A. 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 can not see well in the dark (2:17). They can not see Allah despite His omnipresence (6:103).
B. 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.
C. PERCEPTION OF SPEED
Humans can not visually appreciate very slow or very rapid movements. The earth revolves around the sun as well as rotates on its own axis. Humans can not 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.
D. SIZE DISCRIMINATION
The discrimination of human vision is limited. Small objects can not be seen. Very large objects can not be appreciated if there is no background against which to compare. For example a human is lost in the middle of an empty desert or in the middle of the ocean.
E. VISION UNDER DIFFERENT AMOUNTS OF LIGHT
Sight in darkness or in very bright light is difficult. Humans unlike nocturnal animals can nor see well in the dark. They are also virtually blinded by very strong light such as occurs in lighting.
4.0 THE EYE AS A SEAT OF EMOTIONAL EXPRESSION
A. 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).
B. CRYING
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), crying when reciting Qur'an (KS 121: Ibn Majah K5 B.176), crying 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), and crying for fear of Allah (5:83, KS 122: Bukhari K24 B16; Bukhari K81 B24; Bukhari K86 B19) 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).
C. 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).
D. BEAUTY
The Qur'an has described beauty in heaven as beauty of the eyes (p. 282 37:48, 38:25, 55:56).
E. 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.
5.0 PATHOLOGY
A. ACCOMMODATION
As part of aging 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. Hypermetropia 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.
B. BLINDNESS
Blindness can be congenital, akmah (p 851 3:49, 5:110) present at birth or acquired after birth, 'ama. 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.
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).
Color blindness is an inherited condition that affects males but is transmitted through the mothers.
C. 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).
DISCUSSION
- Explain in your words the differences between the three terms: looking, seeing, and perception
- What is the relation between moral vision and physical vision
- What is the difference between sight on earth, ru'uyat al dunia, and sight in the hereafter, ru'uyat al akhirat
- List all the functions of the vision function that you know
- How does the area of the visual cortex compare with others areas of the cortex
- Are accommodation problems a disease or are a normal process of aging?
- What are the common causes of blindness in your community?
- What are the preventable causes of congenital blindness
- Explain the several ways in which the eye is also an organ of emotional expression
- What is the relation between tears and ibadat and khushuu