|Year : 1971 | Volume
| Issue : 4 | Page : 163-168
Ocular changes following cataract extraction : Effect on facility of outflow
K Nath, RL Vaid
Aligarh Muslim University Institute of Ophthalmology and Jawaharlal Nehru Medical. College, Aligarh, India
Aligarh Muslim University Institute of Ophthalmology and Jawaharlal Nehru Medical. College, Aligarh
Source of Support: None, Conflict of Interest: None
|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
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  The present study was undertaken in order to assess the effect of uncomplicated cataract extractions on the facility of outflow.
| Material and Method|| |
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|| |
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|| |
Grant  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  and Lee and Trotter  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  .
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  have reported that these goniosynechiae, if detected early, can be broken by miotics, thus decreasing the incidence of aphakic glaucoma.
| Summary|| |
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|| |
GRANT W. M.: Clinical measurements in aqueous outflow. A.M.A. Arch. Ophthal., 46, 113-131 (1951).
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).
MILLER J. E., KESKY G. R. and BECKER B.: Cataract extraction and aqueous outflow. A.M.A. Arch. Ophthal., 58, 401-406 (1957) .
[Table - 1]