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ARTICLES
Year : 1971  |  Volume : 19  |  Issue : 4  |  Page : 163-168

Ocular changes following cataract extraction : Effect on facility of outflow


Aligarh Muslim University Institute of Ophthalmology and Jawaharlal Nehru Medical. College, Aligarh, India

Correspondence Address:
K Nath
Aligarh Muslim University Institute of Ophthalmology and Jawaharlal Nehru Medical. College, Aligarh
India
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Source of Support: None, Conflict of Interest: None


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How to cite this article:
Nath K, Vaid R L. Ocular changes following cataract extraction : Effect on facility of outflow. Indian J Ophthalmol 1971;19:163-8

How to cite this URL:
Nath K, Vaid R L. Ocular changes following cataract extraction : Effect on facility of outflow. Indian J Ophthalmol [serial online] 1971 [cited 2020 May 28];19:163-8. Available from: http://www.ijo.in/text.asp?1971/19/4/163/35007

Table 1

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Table 1

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The aqueous humour leaves the eye mainly through the outflow channels situated in and about the angle of the anterior chamber. In cataract extraction the surgical incision of the conjunctiva and sclerocornea is liable to damage the outflow channels and affect the darinage of aqueous humour. Decrease in the facility of outflow after cataract extractions was re­ported by Miller, Kesky & Becker and Lee & Trotter [2] The present study was undertaken in order to assess the effect of uncompli­cated cataract extractions on the facility of outflow.


  Material and Method Top


33 cases of uncomplicated senile cataract, were selected after screening them for any other as­sociated ocular disease. Cases with preoperative applanation tension of above 20 mm. of Hg. and those with operative and post operative complications were excluded. Local instillations known to alter the tonographic values were not used prior to tonography. In each case the topo­graphy was performed by Sch­warzer's recording tonography ap­paratus. Facility of outflow was graphically determined from Friedenwald's nomogram (1955) and the outflow value (Po/c) cal­culated. Just before the tono­graphy, the initial intraocular pressure was recorded by Gold­mann's applanation tonometer.

Preoperatively, the slit lamp and gonioscopic examinations were carried out. Similar surgical technique with a large conjuncti­val flap and a limbal section with keratome and scissors, with minor variations, was followed in each case.

Tonometry, tonography, slit lamp and gonioscopic examina­tions were repeated 6-12 weeks after the cataract extraction and results were compared.


  Results Top


Preoperatively, the facility of outflow varied from 0.15 to 0.70 ul/mm./Hg/mt. the average value being 0.395 ul./mm./Hg./mt. Post­operatively, it varied from 0.12 to 0.77 ul./mm./Hg./mt. with 0.345 ul./mm./Hg /mt. as the group variations were found to occur within the group. The post-opera­tive value of facility of outflow was higher in 10 (30.3%), un­changed in 4 (12.3%) and decrease ­average. Thus the average value of facility of outflow decreased post-operatively. Three types of ed in the remaining 19 cases (57.4 %). In one case the facility of out­flow was markedly decreased (0.12 ul./mm./Hg./mt.) with Po/c' value above 100(133) although the in­traocular tension was normal. On gonioscopy, extensive goniosyne­chiae and pigment dispersion was seen.

Out of 33 cases, extracapsular cataract extraction was done in 12 cases while in the remaining 21 the lens was removed intra­capsulary. Complete iridectomy was done in all cases while amongst the rest a peripheral button-hole iridectomy was per­formed.

There was a greater decrease in the facility of outflow, after extracapsular extraction as compared to intracapsular extractions [Table - 1].

Within the extracapsular group, the facility of outflow was marke­dly lowered (0.22 ul/Hg./mt) in those cases where a substantial amount of cortical matter was left behind than those where cor­tical matter and capsular rema­nants were minimal. (0.32 ul/mm. Hg./mt.).

The decrease in the facility of outflow was more marked in those cases where a complete iridectomy was done (0.22) ul/mm. Hg./mt. as compared to those where peri­pheral iridectomy was done (0.39 ul/mm. Hg./mt.).


  Discussion Top


Grant [1] compared the facility of outflow in the normal phakic with the aphakic eyes and concluded that the facility of outflow is not significantly affected by the re­moval of the lens. In his study, the observations were not made in the same eyes. Our findings, Millar et al [3] and Lee and Trotter [2] which are in agreement with show that the facility of outflow is decreased. This decrease was not found to be statistically signi­ficant as the calculated T value (0.75) was lesser than the tabulat­ed T value (1.96) at 5% level of significance at 32° of freedom. In those cases where there is a marked decrease, it may be due to the marked inhibition of aque­ous formation and is likely to in­crease with the recovery in rate of aqueous formation'. The de­crease in the facility of outflow, if due to extensive goniosynechiae with heavy pigment dispersion, is not likely to increase with the re­covery in the rate of aqueous for­mation. On the other hand, as the aqueous outflow is impaired, the normalization of the rate of aque­ous formation results in the rise of intraocular pressure and apha­kic glaucoma. Such cases of glau­coma, can be detected in early stages by tonographic and gonio­scopic studies alone.

The facility of outflow was found increased in 10 cases. The gonioscopic studies in 6 of these revealed an incarceration of iris tissue in the incision scar while in the remaining 4 cases no cause could be found. Thus the incarce­rated iris tissue, working as a track for aqueous drainage re­sults in increase in the facility of outflow. Similar conclusions were drawn by Lee and Trotter [2] .

Decrease in the facility of out­flow, observed after extracapsular cataract extraction is statistically significant as the calculated T value (5.1) was higher than the tabulated T value (1. 79) at 5% level of significance at 11° of free­dom. This decrease is due to bloc­kage of the outflow channels by the capsular remnants and corti­cal matter. Facility of outflow also decreased but to a lesser extent in cases where extracapsural extrac­tion was performed and the corti­cal matter was almost completely removed at the time of operation. From these observations it appears that the chances of development of aphakic glaucoma are more after extracapsular extraction than after intracapsular and de­pends upon the amount of the cor­tical matter left behind.

Irrespective of the mode of cataract extraction, the decrease in the facility of outflow was more marked in cases with complete iridectomies than those with the peripheral type. No specific reason can be given to account for this but it appears that trauma to the iris. which is greater in complete iridectomy might result in marked suppression of aqueous formation causing a secondary decrease in the facility of outflow. This point shall be discussed in another paper dealing with the effect of cataract extraction on intraocular pressure and rate of aqueous for­mation.

One case who was normal pre­operatively, developed aphakic glaucoma after cataract extrac­tion. Gonioscopic examination in this case revealed extensive goni­osynechia with heavy pigmenta­tion in the angle of anterior cham­ber. In this case intraocular pres­sure was within normal limits but facility of outflow was impaired with high Po/c value (133). It be­comes clear from these observa­tions that tonography and gonio­scopy, when performed after cata­ract extraction, are of great help in the assessment of the eye from point of view of glaucoma. Miller et al [3] have reported that these goniosynechiae, if detected early, can be broken by miotics, thus decreasing the incidence of apha­kic glaucoma.


  Summary Top


Pre and post-operative tono­graphic studies were performed to assess the effect of uncomplicated cataract extraction on the outflow channels.

The facility of outflow as a group average decreased post­operatively but within the group it was unchanged in a few cases while it was increased in others. The increase in facility of outflow was due to incarceration of iris tissue in incision scar while de­crease was probably due to inhi­bition of aqueous formation.

The decrease was more marked after extracapsular cataract ex­traction than after intracapsular extraction and was due to the cortical matter and capsular re­mnants.

 
  References Top

1.
GRANT W. M.: Clinical measure­ments in aqueous outflow. A.M.A. Arch. Ophthal., 46, 113-131 (1951).   Back to cited text no. 1
    
2.
LEE P. F. and TROTTER R. R.: Tonographic and gonioscopic stu­dies before and after cataract ex­traction. A.M.A. Arch. Ophthal., 58, 407-416 (1957).  Back to cited text no. 2
    
3.
MILLER J. E., KESKY G. R. and BECKER B.: Cataract extraction and aqueous outflow. A.M.A. Arch. Ophthal., 58, 401-406 (1957) .  Back to cited text no. 3
    



 
 
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