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   Table of Contents      
ARTICLES
Year : 1983  |  Volume : 31  |  Issue : 7  |  Page : 1001-1004

Refractive keratoplasty


Eye Research Centre, 13, Cathedral Road, Madras, India

Correspondence Address:
T Agarwal
Eye Research Centre, 13, Cathedral Road, Madras
India
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Source of Support: None, Conflict of Interest: None


PMID: 6399900

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How to cite this article:
Agarwal T, Agarwal J, Rao M S, Prakash R S, Sunita. Refractive keratoplasty. Indian J Ophthalmol 1983;31, Suppl S1:1001-4

How to cite this URL:
Agarwal T, Agarwal J, Rao M S, Prakash R S, Sunita. Refractive keratoplasty. Indian J Ophthalmol [serial online] 1983 [cited 2020 May 24];31, Suppl S1:1001-4. Available from: http://www.ijo.in/text.asp?1983/31/7/1001/29729


  Refractive keratoplasty Top


Refraction forms the bulk of work of eye surgeons. In the past it was rather difficult to provide binocular vision in anisometropic eyes. The problem was gradually and par­tially solved by the introduction of various types of contact lenses and later on by intra ocular implants. Any how, these two solutions created certain problems for the patients and surgeons. Refractive Keratoplasty - solves many problems both in respect of visual functions and cosmetic considerations. This wonderful blessing could reach us through the fertile imagination and creative genius of Dr. Jose I. Barraquer of Bogota who laboured hard for 30 years.

Obtaining good visual rehabilitation after cataract operation is often a problem in cer­tain patients. Many elderly aphakic patients are unable to compromise with changes introduced in the quality of retinal image with conventional glasses producing curvatural and chromatic aberrations. These problems, though reduced by contact lenses, pose incon­venience in many cases. At the cataract age, a person becomes a creature of fixed habits. He just cannot tolerate something sticking on the eye in the shape of acontact lens. In Indian environmental conditions, it is rather difficult to use contact lenses in a hygenic way. No doubt, many cases using contact lenses come with scratches, conjunctivitis and even cor­neal ulcers.

It need not be stressed that these problems are multiplied in mono-ocular aphakics. Apart from these draw backs of conventional glasses, even contact lenses are a social taboo for cosmetic considerations specially in the fair sex. Intra ocular implants despite meticulous care have contain unavoidable disadvantages. Too much dispersion of uveal pigment causes its deposition on implants specially in coloured people leading to reduced vision. However benign the implant may be it is a foreign body and is exposed to physical stress, rarely dislocation leads to intractib.le iridocyclitis, secondary glaucoma and its multiple sequelae.

Refractive Keratoplasty extends the boon specially to young persons suffering from traumatic and rarely congenital mono-ocular cataracts. In a nutshell refactive keratoplasty offers the maximum possible benefits in res­toration of function and binocularity, and visual rehabilitation. It is ideal cosmetically and leaves so little for poor and uneducated people to take care of their eyes, themselves.


  Keratophakia and keratomileusis Top


The word keratomileusis came from two greek roots which mean cornea and chisell­ing. Consequently it means carved cornea or nodelled cornea.

The word keratophakia comes from the Greek roots meaning cornea and lens.

Knowledge of optics, mathematics, bio­physics and Cryo biology besides specialised micro surgery are necessary to undertake ref­ractive keratoplasty.


  Basis of refractive keratoplasty Top


The keratophakia is based upon high refeactive corneal powere which permits variations in order to correct strong clinical ametropias and the "Law of thickness" according to which, tissue must be added to the optical centre of the cornea, to correct hyperopia and to its periphery to correct myopia.

If cerneal tissue is added to the centre of the cornea, by means of a small lamellar graft, using a donor disc the regenerative and heal­ing process levels the dges of the bed and graft, but the curvature in teh centre remians accentuated.

Before undertaking the surgery, the corneal thickness the depth of the anterior chamber the thickness of the crystalline lens at rest, and the distance from the posterior surface of the lens to the retina have to be determined, ultrasonically. The optical calculations also require the establishment of the mean value of the refractive index for every component of the eye. These are programmed in the com­puter. The Apple computer is the most ideal one but even a T. I Computer can be used.

To avoid omitting any step of operation, a check list is recorded on a magetic tape, star­ted by the operator with a foot pedal before every step.

During the last one year, 27 cases of this sur­gery "Refractive Keratoplasty" were done.

The young ones too having reaped the fruits of this labouring procedure. 2 cases were bet­ween 10-20 years of age. Among 30-40 years were 3 cases, 41-50 years were 8 cases, 51-60 years 6 cases and above 61 years 8 cases.

Among these were 17 males and 10 females The break up of different operations was a is follows;

Keratomileusis with ... 24 cataract extraction

Keratomileusis (Myopia) ... 2

Keratophakia ... 1

Visual acuity has been recorded 3 months after the operation and that is the reason visual acutiy of 16 cases could not be recorded.

visual acutiy not recorded ... 16 cases

6/12 or better ... 5 cases

6/18 to 6/60 ... 6 cases less than

6/60 ... nil.


  Keratophakia Top


This is the term used for that type of opera­tion where a donor cornea is used to make a corneal disc and after grinding it to the required powere is sutured in between the two layers of the recipient cornea. Hence ker­atophakia is an operation for aphakia of more than 12 to 14 dioptres.

A disc of 0.4 mm thickness and 6.0 to 6.50 mm in diameter is cut from the donor eye by the use of a microkeratome. To achieve the required size and thickness of the graft an intra ocular pressure of 50 to 65 mm Hg is required, which is obtained by the use of a pneumatic fixation ring of the required size. The intra ocular pressure can be checked by the pre-surgical applanation tonometer and the diameter of the disc by the applanation ring. To make the disc clearly visible, it is placed in a soultion of 8% Glycerine, 4% Dimethyl Suplphoxide and 1% Fulorescein. This is disc is forzen at -30° C by coz snow to make it hard. This hard disc can be ground on the Cryo Lathe as per the readings given by the computer. It is achieved by thinning the periphery, and making the centre more con­vex. This is done on the epithelial side of the cornea. The same disc is defrosted and sutured between the two layers of the recipient cornea.


  Indication of keratophaka Top


1) Very high hypermetropia-unilateral or bilateral hypermetropia of over 5 dioptre s.

2) Aphakia

a) Monocular aphakia in congenital and traumatic cataract.

b) Bilateral aphakia

c) in cases of unmanagable rehabilita­tion of aphakic patients mostly in cases of mono ocular aphakia.

3) Very high myopia.


  Contra indiactions Top


1) Corneal diseases

2) Very thin corneas as in keratoconus

3) Corneas with irregular thickness

4) Flat corneas with myopia and steep cor­neas with hypermetropia.


  Keratomileusis Top


Is that type of operation which is performed with the patient's own cornea or autograft. It can be done in myopia, hypermetropia and aphakia of not very high dioptric power. Here no donor material is required and the patient's own cornea is chiselled to the required power.

In tnis operation a disc of 0.4 mm thickness and 7 to 8 mm in dianeter is cut with a mic­rokeratome from the anterior surface of patient's cornea. To achieve the required size and thickness of this autograft on intra ocular pressure of 65 mm of Hg. is required, which can be obtained by the use of a pneumatic fixation ring of the required size. The intro ocular pressure can be checked by the pre-surgical applanation tonometer and the diameter of the disc by the applanation ring. This autograft from the patients own cornea is stained in a soulution of Glycerine, Dimethyl Sulphoxide and Fluorescein and frozen in the cryo Lathe itself by liquid Car­bondoxide. After the disc is frozen, this disc is cut from the stromal side of the cornea as per the readings given by the computer. This cut­ting is done by the Cryo Lathe. After the grind­ing is over, the disc is defrosted in 10% Glycerine solution and sutured back on the cornea with 10/0 monofilament nylon. The power in this is achieved, in myopia, by thin­ning out the central portion of the disc and in cases of aphakia, by thinning out the edges..


  Indication of keratomileusis Top


1) Bad contact lens tolerance.

2) Anisometropia.

3) Myopia above 6 D.

4) Hypermetropia above 6 D.

5) Post operative diplopia after squint surgery.

6) Aphakia of less than 12 D.


  Contra indications Top


1) Corneal diseases.

2) Very thin corneas as in keratoconus.

3) Corneas with irregular thickness.

4) Flat corneas with myopia and steep cor­neas with hypermetropia.


  Operative complications Top


1) An irregular section : this can be produced as a result of

a) Low intra ocular pressure.

b) Variations of intra ocular pressure during Keratectomy.

c) Quick withdrawing.

d) Poor adhesion by pneumatic ring.

i) Incorrect sized pneumatic ring is used

ii) Obstruction of suction tube.

2) In complete section

a) loss of suction.

b) Hasty removal of microkeratome. c) Blunt blade.


  Post operative complication Top


1) The corneal tissue displacement as a result of indequate suturing wound, hamper the success of the operation.

2) Foreign bodies in the interface should be avoided by the use of a biomicroscopical control with a slitlamp.

3) Peripheral corneal opacities as a result of fluid at the interface and poor coaptation could- also be produced.

4) Epithelization.

5) Corneal button vascularisation may occur but no case has yet been reported.

6) General infection as occurs in any operation.

7) The power may sometimes not be correc­ted adequately. In such cases corrective glasses can be given.




 

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  In this article
Refractive kerat...
Keratophakia and...
Basis of refract...
Keratophakia
Indication of ke...
Contra indiactions
Keratomileusis
Indication of ke...
Contra indications
Operative compli...
Post operative c...

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