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   Table of Contents      
ARTICLES
Year : 1971  |  Volume : 19  |  Issue : 1  |  Page : 7-13

Changes of refraction after cataract surgery


Department of Ophthalmology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India

Correspondence Address:
P A Lamba
Department of Ophthalmology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry
India
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Source of Support: None, Conflict of Interest: None


PMID: 15744957

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How to cite this article:
Lamba P A, Sood N N. Changes of refraction after cataract surgery. Indian J Ophthalmol 1971;19:7-13

How to cite this URL:
Lamba P A, Sood N N. Changes of refraction after cataract surgery. Indian J Ophthalmol [serial online] 1971 [cited 2020 Sep 29];19:7-13. Available from: http://www.ijo.in/text.asp?1971/19/1/7/35004

Table 4

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Table 4

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Table 3

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Table 3

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Table 2

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Table 2

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Table 1

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Table 1

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The obligation of the cataract surgeon towards his patient does not end just with a perfect sur­gical result. Early rehabilitation and prescription of glasses may be the answer to the adjustment in aphakia. In this country. due to socio-economic factors, early pres­cription of glasses to aphakics poses a special problem especial­ly for the one eyed individual, a mature cataract in both eyes, or the only earning member of the family who has to undergo the surgical lens extraction.

Cataract incisions and their closures have been widely studied with an attempt to reduce overall astimatism, [4],[5],[6],[10] but there has been a paucity of studies regard­ing the astigmatic changes result­ing from these techniques. Beas­ley [1] , Elenius and Karo [3] studied the post-operative changes in the refractive power of the cornea us­ing a keratometer at varying periods. There are many factors which seem to influence the amount of astigmatism produced and these will be discussed on this paper. The study was designed to consider the changes in refraction at varying periods after cataract extraction with an attempt to cor­relate the findings so that accu­rate predictions relative to refrac­tion changes may be male.


  Methods and Material Top


An evaluation of 100 cataract extractions (intra-capsular) per­formed during early 1969 at the Department of Ophthalmology, JIPMER Hospital is attempted. To avoid personal factors the opera­tions performed by either of us are included. Either of the follow­ing techniques was used for inci­sion and wound closure.

1. A 3 mm. conjunctival flap is reflected over the limbos. The flap is dissected into the cornea which is split for 1 to 2 mm. with a Took's knife. Haemostasis is ob­tained by heat cautery. A limbal gutter is prepared by incising partially through the thickness of the cornea using the tip of a Bard Parker knife without entering the anterior chamber. Using Men­doza's technique [8] as a basis, one preplaced corneoscleral 6-0 silk suture is placed through the cut edges (entering the cornea near the base of conjunctival corneal flap) and across the gutter. The suture is pulled up to form a loop and a perpendicular ab extern incision is made into anterior chamber between the arms of the loop at the 12 o'clock position. The limbal wound is enlarged tempo­rally and nasally using Castroviejo's corneal scissors, holding the scissors at right angles to the cornea to produce a perpendicular incision.

2. The classical limbal incision using Von Graefe's cataract knife and enlarged with scissors. The corneal incision was not made by either of us.

The number of sutures used varied from one to three corneo­scleral sutures supplemented by conjunctival sutures. In 16 cases, only one corneoscleral suture was introduced while in 54 cases two or more sutures were applied. Peripheral, complete or no iridec­omy was Anna in this series.

Post-operatively all these patients were regularly examined and refracted at weekly intervals starting from 8th day to 4~ days. At each follow up visit, the re­fraction was done and the retino­scopic findings were noted down correct to 0.5 diopter. A record was also kept of the maximal visual acuity with glasses at the time of the visit The changes in the dioptrie power, the degree, and axis of astigmatism have been studied in relation to type of sec­tion, number of corneoscleral su­tures and changes due to prolapse of vitreous.

Changes in Axis

An analysis of the axis of post­operative astigmatism at varying periods after surgery is shown in [Table - 1]. On the 8th day, 77 per­cent of eyes had astigmatism against the rule (greater curva­ture horizontal) while 18 per cent had astigmatism with-the-rule (greater curvature vertical). Only five eyes were seen to be without astigmatism. With the passage of time (48 days after operation) 27 per cent eyes were seen to be with no astigmatism and the individuals showing astigmatism with-the-­rule and against-the-rule showed a decline. Only 6 eyes had astig­matism with-the-rule and in con­trast 67 per cent had astigmatism against-the-rule. This change is believed to be due to the healing of limbal wound and contraction of the scar.

Changes in Spherical Refraction :

(Less Corneal Curvature)

[Table - 2] shows the changes of -refraction in the post-operative period as seen along the lesser corneal curvature. 83 per cent of the individuals showed refraction between +10.5 to +13.0 diopters at the 48th post-operative day. The mean values of spherical re­fraction [Table - 4] on the 8th and 48th post-operative day had been +11.06 and +11.59 diopters. This change (0.53 D increase) has been gradual as illustrated. The final mean spherical power observed was +11.59 diopters with a stan­dard deviation of + 1.05.

Changes in Astigmatism:

(Difference between greater and lesser corneal curvature).

[Table - 3] reveals that at the examination on 48th post-opera­tive day, 27 per cent of individuals were seen to be without any diffe­rence between greater and lesser corneal curvatures. 70 per cent of the individuals in the series exhi­bited a residual astigmatic error of +1.0 D or less. Maximal astig­matism (+ 5.5 diopter or above) was observed only in 7 per cent cases on 8th post-operative day and 5 per cent on the 16th post­operative day. Maximal astigma­tism recorded after 48th post-ope­rative day was 4 diopters observ­ed in one case only. Mean values of astigmatism showed a progres­sive decrease with the passage of time in the post-operative period. It becomes almost stationary at 40th post-operative day signifying the firm closure of the wound.

An important fact which was observed and well documented in [Table - 4] is that with the passage of time the dioptric power along the lesser curvature of the cor­nea tended to increase while it was opposite along the greater curvature. The net result of the change was a decrease in the degree of astigmatism. The mean manifested astigmatism at the 48th post-operative day was +0.93 diopter with a standard deviation of ± 0.85. It showed a change of 1.49 diopters compared to the mean astigmatic value at the 8th post-operative day.


  Discussion Top


Comprehensive cataract man­agement rests atop a tripod of interrelated objectives; good sur­gery, adequate correction of apha­kia, and timely visual rehabilita­tion. The first objective has been adequately achieved through the recent advances in incision and wound closure using an operating microscope. The latter two objec­tives are receiving an increasing attention by ophthalmologists.

The incision for cataract ex­traction causes a corneal distor­tion that gradually reduces as the healing occurs. Duke Elder [2] in his encyclopaedic work observed an astigmatism of 8-10 diopters on 20th post-operative day, decreas­ing to an average of 2-3 diopters on 40th day. The post-operative keratometric readings are valuable for the estimation of astig­matism since it is entirely corneal. The limitations of the use of this instrument are evident from the following facts.

(a) The use of keratometer is of considerable scientific value but it saves the time only at the cost of accuracy (Duke Elder).

(b) Since the nodal point of an aphakic eye has moved for­ward the optical effect of the corneal curvature is never so strong as is indicated by direct measurement with oph­thalmometer. Beasley [1] also observed that the kerato­metric measurements err on the low side when small amounts of astigmatism are present but err on the high side as the astigmatism in­creases.

Various workers have reported a decline in the post-operative astigmatism by the use of multi­ple sutures (Taylor [11] , Scheiel [10] ). Hilding [5] observed that average astigmatism following the use of two sutures was +1.9 diopters but when 4 sutures were used it was reduced to 1.6 diopters. Nirankari and Khanna [9] . observed a high degree of corneal astigmatism (with an average of 7.242 D) on the 10th post-operative day, while in our series the mean value for the degree of astigmatism on 8th post-operative day with limbal section was 2.42 D (S.D. + 1.56 D). Beasley [1] in his series placed the section anterior to the Schwalbe's line and used 3 pre­placed corneoscleral sutures. He recorded the average manifest astigmatism of 2.01 diopters (.3 diopters less than measured with keratometer) 46 days after cata­ract surgery. Elenius and Karo [3] studied the changes in the refrac­tive power of cornea in 62 apha­kic eyes using 5 corneo-scleral unremoved for one month and observed on an average astig­matism of 3.1 diopters at 3rd post­operative month. The average astigmatism seen at the end of 48 days in our series was 0.93 diopter (S.D. - 0.85 D) against-the-rule.

The relationship of iridectomy to the amount of post-operative astigmatism has been widely debated. In this series, we have observed that the post-operative astigmatism was relatively higher (average 0.6 diopters) when com­plete iridectomy was done as com­pared to the cases with or with­out peripheral iridectomy. The experience of Sloane was similar. No satisfactory explanation can be given for this phenomenon, how­ever it is postulated that the for­ward movement of the vitreous close to the wound may have some role to play in wound heal­ing. Out of 9 cases showing high grade astigmatism (more than 2.5 diopters) on 48th post-operative day, 5 cases were seen to be asso­ciated with varying degree of vitreous loss. The present obser­vations reveal that the dioptric power of lesser curvature of cor­nea (horizontal axis) rises while the vertical dioptric power de­creases in the post-operative period due to the flattening of the corneal curvature. We believe that the condition of suture astigmatism (Floyd [4] ) does not exist and that the post-operative changes in astigmatism are pro­bably due to healing of the wound and contraction of scar resulting in flattening of the cornea in the vertical meridian. A similar view was also expressed by Nirankari

No appreciable difference in astigmatism was observed in cases with one or two conrneoscleral sutures when they were supple­mented with a conjunctival flap. The conjunctival flap sutured firmly to the posterior lip of the conjunctiva and Tenon's flap gave an excellent secondary support to `the limbal wound These sutures are less likely to leak and they produce no suture tract for possi­ble epithelialization. We are of the opinion that the number of stitches put is not of much im­portance so long as accurate and exact approximation is achieved. The technique of incision and wound closure followed in the present series ensured an align­ment of suture, good opposition of the perpendicular limbal inci­sion and fulfilled all the criteria of evaluation described by McLean [7] .

From the present study it has been observed that the spherical refraction and the astigmatism showed a progressive rise and decline respectively till 40th post­operative day after which the curve became horizontal (illustrated [Figure - 1]). The linear graph represented settling down of re­fraction to its permanent stage by the 40th post-operative day and the accurate prescription of glas­ses may be given to the patient.


  Summary Top


With the objective that an aphakic should be able to go back to his job or cease to be a burden to the members of his family for daily routine of life, this study 'was undertaken in 100 recently operated cases of cataract. The study analysed the changes of re­fraction at varying periods after cataract surgery and an attempt was made to correlate the findings so that an accurate prediction re­lative to refractive changes may be made. The changes observed were a gradual increase in the spherical refraction (less corneal curvature) and a decrease in the astigmatism (difference between greater and lesser corneal curva­tures) till 40th post-operative day. The refractive power of the eye settled down to a permanent stage by the 40th day. The mean value of spherical refraction has been + 11.5 diopters (S.D. ± 1.05) with cylindrical correction of + 0.93 diopter (S.D. ± 0.85) against-the­-rule.


  Acknowledgment Top


We are indebted to Dr. K. N. Shukla, Professor of Ophthalmo­logy, for his valuable guidance. We acknowledge our thanks to Mr. Rangasamy, Statistician, JIPMER Hospital for help in pre­paring the statistical tables.

 
  References Top

1.
BEASLEY, H.: Keratometric changes after cataract surgery. Tr. Amer. Ophth. Soc. 65 : 168 (1967).  Back to cited text no. 1
    
2.
DUKE-ELDER, S.: The practice of refraction. The C. V. Mosby Coy. London Ed. 1954, p. 107.  Back to cited text no. 2
    
3.
ELENIUS, V. AND KARO, T.: Changes in refractive power of cornea after cataract surgery. E & E.N.T. Monthly 47 : 66, (1968).  Back to cited text no. 3
    
4.
FLOYD, G.: Changes of Corneal curvature following cataract ex­traction. Amer. J. Ophth. 34 : 1525, (1951).  Back to cited text no. 4
    
5.
HILDING, A. C.: The experimental approach to cataract surgery. Amer. J. Ophth. 53 : 606, (1962).  Back to cited text no. 5
    
6.
KUWAHARA, S.: Changes of Cor­neal Curvature after cataract sur­gery and its effects on visual acuity. Acta. Soc. Ophth. (Japan) 37 : 883, (1933).  Back to cited text no. 6
    
7.
McLEAN, J. M.: A new corneos­cleral suture. Arch. Ophth. 23 : 554, (1940).  Back to cited text no. 7
    
8.
MENDOZA, de S.: On suturing o f the cornea (In French) Bull. Soc. Ophth. Paris. 1 : 105 (1888).  Back to cited text no. 8
    
9.
NIRANKARI, M. S. and KHANNA, K. K.: Sutures in Cataract Surgery. Orient. A. Ophth. 6 : 8, (1968).  Back to cited text no. 9
    
10.
SCHEIE, H. G.: Incision and closure in Cataract extraction. A. M. A. Arch. Ophth. 61 : 431, (1959).  Back to cited text no. 10
    
11.
TAYLOR, D. M.: Optimum Wound closure in Cataract Surgery. Amer. J. Ophth. 48 : 660, (1959).  Back to cited text no. 11
    


    Figures

  [Figure - 1]
 
 
    Tables

  [Table - 1], [Table - 2], [Table - 3], [Table - 4]



 

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