Sharir is the study of human body from its structural as well as functional point of view. In Ayurveda, sharir has been explained in depth by Sushrutacharya as compared to others. Since Sushrut Samhita is dedicated to surgical part, the sharir which is explained is mostly clinically as well as surgically significant . Along with general surgery, some special surgical procedures related to Shalakya tantra are also explored by Sushrutacharya and hence accordingly , Sharir of specific parts is described.

Netra sharir is one of the most significant explained in Sushruta Samhita which is applicable in surgical procedures of various deformities of netra. One important surgery which is elaborated by Sushrutacharya is Linganash shastrakarma i.e. Cataract surgery and to carry out this surgery, Daivakruta chidra is an important structure, but is not described in detail.

In the present study, there is an attempt made to elaborate sharir of Netra with special emphasis on Daivakruta chidra. For this research, the literature has been collected from the Ayurvedic classic texts with the commentaries, as well as modern science text books have been referred for understanding of the concept along with its comparison and correlation with modern science.

Review of literature :

Netra Sharir explained in various texts in ancient era:

While narrating the importance of Netra, it is said that, Netra is an vital organ for indriya janya gyana (sensory knowledge) which is necessary for pratyaksha gyana (direct perception). We acquire clear knowledge with the help of indriya ( five sensory organs) and out of the five indriya, most  important among which is the netra.¹(Source Title, 1992)

Netra is included in the bahirmukha srotasa (external apertures) which are used as a route for drug administration .²(Source Title, 1992)

Netra Utpatti  (Embryological Development of the Eye):

Absence of light has been mentioned as the cause of lack of knowledge and hence Acharya has mentioned surya (Sun) as the God of netra^.3 (Source Title, 1992)^.

According to Ayurveda, all body parts are made up of Panchmahabhuta i.e. Akash, Vayu, Teja, Jala and Pruthvi. Netra is a Teja mahabhuta dominant organ. There is a dominance of teja mahabhuta, but other four mahabhuta also contribute in the formation of eyeball in a developing embryo.⁴(Source Title, 1992) Mamsa-muscle, fascia are from prithvi mahabhuta, Rakta – blood vessels are from teja mahabhuta, Krishna bhaga- cornea/iris is from vayu mahabhuta, Shweta bhaga- sclera is from aapa mahabhuta, Ashrumarga- lacrimal apparatus is from aakasha mahabhuta and the entire eye ball is appeared to be a bubble of water.⁵ (Source Title, 1992)All the indriyas become definite during the third month. Charaka and Kashyap has accepted the same that the genesis of all sense organs including eyes and organogenesis occurs in third month of intrauterine life. According to Janaka of Videha, the seat of senses is first formed. Punarvasu Atreya concluded that all the five sense organs are developed simultaneously.⁶(Chakrapanidatta, 2009)

Shape of eye ball:

Sushruta described two shapes of eyeball, one is suvrutta (perfectly spherical) and another is gostanakar (like nipples of Cow)⁷. (Source Title, 1992)These can be correlated as follows :

1) Suvrutta = exactly spherical.

2) Gosatanakar = eye ball with optic nerve which is  covered by Tenon’s capsule.⁸(Source Title, 2004)

Measurements of Eyeball-

Acharya Sushruta has given the term Nayana budbuda for an eye ball.

Sushruta has mentioned the dimension of eyeball in terms of angula wherein one angula is equal to the central part of the patient’s own thumb. Two angula is the antero-posterior diameter of the eyeball while vertical and horizontal diameter is two and half angula. Shape of the eyeball resembles with the teat of a cow and it arises from all the bhutas (akasha, vayu, agni, jala, prathivi) with their attributes. In modern perspective, dimension of an adult eyeball is as follows: anteroposterior diameter is 24mm, horizontal diameter is 23.5mm, vertical diameter is 23mm, circumference is 75mm, volume is 6.5ml and weight is 7gm .⁹(Khurana, 2015-08-31)

Eye colour  -

In fetal life, teja is responsible for vision and if this teja doesn’t reach the drushti bhag (visual apparatus), the child is congenitally blind (amblyopia). Color of the eye relies upon whether tejo dhatu combines with rakta, pitta, kapha or vayu. When tejo dhatu goes to the visual part with the rakta, the child may develop raktaksha (red eyes); if it goes with pitta, then pingaksha (yellow eyes); if with kapha then shuklaksha (white eyes); and if with vata then the eyes of the progeny would be vikrutaksha (deformed eye).¹⁰(Sthana, n.d.)

During the Upanishada period, ocular anatomy was depicted in philosophical manner. In Brihad Aranyaka Upanishada, defferent structures of eyeball were said to have evolved from different Gods .¹¹(Madhukar & Nivrutti, 2018)

Muscles related to eyeball:

There are two peshis (muscles) which cover the eyeball. The surgeon must take an oblique incision over these muscles.¹²(Source Title, 1992)

Asthi related to eyeball:

While describing types of asthi (i.e. bone), Sushruta mentioned tarunasthi (cartilage) which is related with akshikosha (orbit).¹³(Source Title, 1992)

Parts of netra:

Sushruta has described that eyeball is made up of five mandals, six sandhis and six patalas.¹⁴(Source Title, 1992)

1) Mandal –means rounded or spherical in shape. The parts which appears to be circular or rounded are described as mandal.^15,16 (Source Title, 1997)(Source Title, 1992)

2) Sandhi- means joint. Sushruta has classified sandhi into two types. Those which can be counted and are between the bones and another type of joints are countless as these are the joints between peshi (muscles), snayu (tendons) and sira (vessels)¹⁷.(Source Title, 1992)

 Latter type of junctions are present in netra and are described as sandhi. Joints between five mandalas forms six sandhis as follows:

i. Kaninaka sandhi – inner canthus

ii. Apanga sandhi – outer canthus.

iii. Pakshma-vartma gata sandhi – junction where eye lashes are attached to the eyelids.

iv. Vartma–shweta gata sandhi – fornix- where palpebral conjunctiva meats bulbar conjunctiva.

v. Shweta- krishna gata sandhi – sclero – corneal junction.

vi. Krishna – drushti gata sandhi – pupilary margins.¹⁸(Source Title, 1992)

Netragata patal:

In Sushruta samhita, there is a very crisp description about patala. He described six patalas related to netra, out of which two patalas are bahya¹⁹ (Source Title, 1992)(i.e., externally situated), and remaining four patalas are abhyantara (i.e. internally situated).

These are as follows:

i) Urdhwa vartma – upper eyelid

ii) Adho vartma – lower eyelid these are bahya patalas.

iii) Tejojalashrit patal

iv) Pishitashrit patal

v) Medoshrit patal

vi) Asthyashrit patal

Sushruta has not described the shape, position, colours etc of patalas but he has given the symptoms of the diseases caused by affecting these patalas. By reviewing and comparing these symptoms with modern concepts of eye diseases, we can have some conclusions about these abhyantara patalas.

Concept of drishti

As Timira is one among the Drishti gata roga, it is quite necessary to know more about drishti.

Definition of Drishti (area of sight/vision)-

The drishti is of the size of a cotyledon of the lentil, composed of the finest parts of panchmahabhutas, gleaming like a glow-worm or a spark which is covered by the external coat of the eye and appears like a hole.²⁰(Sushrut, 2016)

The concept of Drishti by Acharya Sushruta is a bit different and all the description of Drishti given by him points to the pupil i.e.

Sira (Veins, Arteries and Nerves)-

Acharya Dalhana describes sira as plural word and it  can be considered as the orbit having a single ophthalmic artery but two ophthalmic veins. Sira (Veins): Acharya Susruta has described both the eyes have 38 siras.²¹(Dalhan, 2009)  vata is carried in eight sira, pitta, rakta and kapha are carried in ten sira each. Acharya vagbhatta has explained total number of 56 siras present in the both eyes. Among them two siras each are responsible for lid movement (nimesha-unmesha) and six siras should not be opened during sira vyadha.

Dhamani (Arteries): The two  dhamanis helps in visual perception and two are for the flow of tears.²²(Dalhan, 2009)

Kandara (tendons and ligaments) of the Eyeball: it can be considered as trochlea of superior oblique and suspensory ligament of eyeball.

Snyau, Peshi: There is a Prithu snayu in the eyes. Two peshi are situated in both eyes and which are circular (Mandala) in shape.

Meda and Sleshma Bandana (Orbital fat) of  Eyeball: The Meda and Sleshma Bandana can be considered as orbital fat of both eyelids.

 Marma (Vulnerable Area): three marma are described in relation to eye i.e. Apanga, Aavarta and Shringataka. The two apanga marma are situated on the outer side of the orbit, below the lateral end the of the eye-brows. The injury of apanga and avarta marma them cause blindness or diminished vision. The apanga marma and avarta marma is a type of shira marma and half angula in size. The Avarta marma is above the lateral end of the eyebrows. The Sringataka marma is the merging of vessels providing nutrition to sense organs like nose, ear, eye and tongue. It is a sira marma and four angula in size and injury to this can also results in immediate death.²³(Sthana, n.d.)

Daivakruta chidra:

            Sushrutacharya has mentioned about surgical interventions of eye in ancient era. The anatomy of eye explained in classical texts is useful in understanding the surgical procedures adopted by Sushrutacharya. While Daivakruta Chhidra is not mentioned in the process of  describing the Netra Sharir, the exact location is not mentioned. However, its importance in Cataract surgery is mentioned.²⁴(Acharya, n.d.)

              The Marma sthanani is quoted by Sushrutacharya, which needs to be protected during surgical procedures.²⁵(Acharya, n.d.) Apart from this, some points such as Daivakruta chhidrani are mentioned, which should be used as site of incision during operative procedures of eye and ear.

About the Daivakruta chhidra in relation to eye, it is said that while doing Linganash Shastra Karma, the surgeon leaving two parts of white circle from the black one towards the outer canthus , should open his eyes properly, free from vascular network and then with a barley tipped rod like instrument held firmly in hand with middle, index and thumb fingers should puncture the natural hole like point with effort and confidence, not below, above or in sides^. The left eye has to be punctured with right hand and vice versa. when punctured accurately, a drop of fluid comes out along with  some typical sound. This is the only reference of Daivakruta chidra present in Netra by Sushrutacharya.²⁴(Acharya, n.d.)

 As mentioned before as well, while doing Linganash Shastra Karma, the surgeon leaves half parts of angul of white circle from the black one towards the one fourth of outer canthus, while opening his eyes properly  free from vascular network and then with a tipped rod like instrument held firmly in hand with middle, index and thumb fingers should puncture the natural hole like point (not much behind or above) with effort and confidence.²⁶(Vaghbhatta, 2016)

On the basis of above references of Daivakruta chidra and its application in surgical intervention, this site can be compared with sclero-corneal junction. But the same needs to be studied while making an attempt for clinical research on cataract surgery performed in today’s era.

Discussion :

Netra Sharir mentioned in Ayurveda texts can be correlated with modern anatomy of eyeball, with a very  few exceptions. Though this information is very vague while comparing to the current knowledge of eye, we must understand that Maharshi Sushruta has never explained only anatomical view of situations but also described each and every subpart of eyeball in utmost detail. In Ayurvedic classics, all the anatomical structures are described with its physiological aspects. He first ever described the anatomy of eye in relation to their shape, size of various anatomical components while elaborating seventy-six different kinds of eye diseases and their treatment in uttara tantra. While Netra execute both physiological functions of roopagrahana and buddhigrahana as it is the seat of Alochaka pitta, with its predominance of tejo mahabhuta ,there is always a threat of kapha to eye.

The shape of netra is like suvrittam which means spherical from all sides and gostanakara means shaped like that teat of the cow (oval shape). Acharya Sushruta described the anatomical parts of the eye consists of mandals are five in number and sandhi and patala are six in number. Sandhi is the junction between two Mandalas and are 6 in number. Acharya sushruta has described the importance of patala in netra sharir. The first patala is the seat of tejas and jala and it can be taken as cornea and aqueous humour; the second patala is the seat of mamsa and it can be taken as iris and ciliary body. The third patala is the seat of medo and it can be taken as vitreous humour, it is a jelly like structure which resembles medas. The fourth patala is the seat of asthi and it can be taken as lens and retina, as it is the seat for linganasha.

These are the parts where doshas get localized and lead to various types of netra rogas. When doshas invade gradually deeper in the patala, it causes timira, Kacha and Linganasa. Netra also consists of Akshi bandhana, sira, pesi, dhamani, marma, snayu and other accessory parts. Thus, whole of patala ,Mandala, Sandhi, Akshi bandhana, sira, pesi, dhamani, marma and snayu completes the netra sharira. It can be said that Patala were described by Acharyas in order to show the severity of the diseases when they involve deeper tissues and no single structure can be correlated with specific Patala accurately. Patala can be taken as different structures in different contexts.

Based on the physiological anatomy of eyeball, he further mentioned different forms of treatment, do’s and don'ts to restore eye health. In eye surgery, Sushruta mentioned ‘the God created hole’ (daivakruta chhidra) which is bloodless and an easy approach towards lens . There is a need of further clinical and surgical research in the field of Ayurvedic netrasharir to explore the concept of Sushruta mentioned.

Conclusion :

Netra Sharir explained by Sushrutacharya is surgically important.

Daivakruta Chidra mentioned in Linganash shastrakarma is considered as important structure while performing various ocular interventions in today’s time.