|Year : 2016 | Volume
| Issue : 3 | Page : 186-188
Effects of cataract surgery on ocular hypertension
Reshma Ramakrishnan, Saurabh Shrivastava, Swetha Narayanam, Brijesha Dudhat, Nitesh Bhalla
Department of Ophthalmology, MGM Institute of Health Sciences, Navi Mumbai, Maharashtra, India
|Date of Web Publication||2-May-2017|
Dr. Saurabh Shrivastava
Department of Ophthalmology, MGM Medical College, Navi Mumbai - 410 210, Maharashtra
Source of Support: None, Conflict of Interest: None
Purpose: The aim of the study was to analyze the effect of cataract surgery on ocular hypertension and to evaluate if type of surgery changes the postoperative intraocular pressure (IOP) outcome.
Materials and Methods: A prospective longitudinal study of sixty patients out of which forty of them underwent phacoemulsification and twenty underwent manual small incision cataract surgery over a period of 2 years from December 2014 to October 2016. Data were entered in Microsoft Excel and analyzed using Strata version 13. We calculated the means and standard deviations for the linear variables and proportions for the categorical variables. The means between two groups were compared using the unpaired t-test (for different groups). The proportions were compared using Chi-square test or Fisher's exact test (for low expected cell counts). We used Mann–Whitney test for comparing the distribution of the variables and Wilcoxon matched-pairs signed-ranks test for equality of matched pairs.
Conclusion: In our study, 22.7% fall is noted by the end of 3 months. Pressure-to-depth (IOP/anterior chamber depth) ratio is a valuable prognostic indicator in ocular hypertensives as well to predict postoperative IOP outcome. The type of surgery did not effect the reduction in IOP postsurgery by the end of 3 months.
Keywords: Cataract surgery, intraocular pressure, ocular hypertension
|How to cite this article:|
Ramakrishnan R, Shrivastava S, Narayanam S, Dudhat B, Bhalla N. Effects of cataract surgery on ocular hypertension. Kerala J Ophthalmol 2016;28:186-8
|How to cite this URL:|
Ramakrishnan R, Shrivastava S, Narayanam S, Dudhat B, Bhalla N. Effects of cataract surgery on ocular hypertension. Kerala J Ophthalmol [serial online] 2016 [cited 2021 May 6];28:186-8. Available from: http://www.kjophthal.com/text.asp?2016/28/3/186/205420
| Introduction|| |
Cataract and glaucoma are ranked as the leading causes of blindness worldwide (51% and 8%, respectively). Cataract surgery rises as one of the most common surgical procedures performed worldwide, and it has been suggested to be of clinical benefit for both diseases. Besides removing the opacified lens, cataract surgery has been suggested to reduce intraocular pressure (IOP) in eyes either with or without glaucoma, although with variable magnitude and influenced by several factors, including anterior chamber anatomy and angle configuration.
Ocular hypertension is defined as an IOP higher than normal (21 mmHg) in the absence of visual field loss or optic nerve damage and anatomically normal, open angles on gonioscopy with the absence of ocular conditions contributing to the elevation of pressure, such as narrow angles, neovascular conditions, and uveitis. It is, by itself, the main risk factor for progression to glaucoma. According to the Ocular Hypertensive Treatment Study (OHTS), phacoemulsification with intraocular lens (IOL) implantation decreases IOP in this subset of patients proportionally to their preoperative IOP.
There are studies on normotensive eyes which show that the cataract surgery significantly lowers the IOP. Some studies, however, show that there is an increase in IOP and ocular hypertension, which may or may not proceed to glaucoma as a known complication of the cataract surgery. All these studies show conflicting results and even the amount of IOP reduction or increase varies with different studies. However, definitive effect of cataract surgery on ocular hypertension has not been extensively studied in the Indian population. We want to analyze the prognostic efficiency of the predictive index pressure-to-depth (PD) ratio (IOP/anterior chamber depth [ACD]) in predicting postoperative IOP outcome with cataract surgery. We also intend to see if the type of surgery changes the postoperative IOP outcome.
Neither the OHTS nor European Glaucoma Prevention Study prediction models for the development of primary open-angle glaucoma (POAG) adjusted baseline IOP for corneal thickness by correction formulae. To determine whether doing so might improve the predictive ability of the model, the predictive model for the development of POAG substituting the value of IOP adjusted for central corneal thickness (CCT) for the unadjusted IOP was recalculated.
Taking into consideration various anatomical and biometric parameters, some predictive indexes of postoperative IOP were created. In 2005, Issa et al. developed a predictive index for IOP reduction in patients without glaucoma based on two anatomical factors IOP and ACD and concluded that it correlated better with IOP variation than each of the parameters individually considered. He described a novel index for predicting the degree of IOP reduction based on the ratio of the preoperative IOP and ACD, which they termed the PD ratio and investigated the predictive value of PD ratio as an indicator for IOP drop postcataract surgery. It has been discovered that the PD ratio was positively related to the extent of IOP reduction. Eyes with PD ratio 6.0 or more exhibited a mean reduction in IOP of 4.90 mmHg, and this reduction was significantly greater than for eyes with a PD ratio <6.0 who had a mean reduction of 1.64 mmHg.
| Materials and Methods|| |
This was a prospective longitudinal study consisting of 60 patients with age 35 and above who presented to the Department of Ophthalmology having ocular hypertension and concurrent cataracts. Detailed evaluation of the patient that included visual acuity, IOP measurement, IOL power and ACD calculation with ZEISS IOLMaster 500, CCT measurement, and adjusted IOP calculation was done. Thorough anterior chamber, examination was done on slit lamp. Patients were then posted for cataract surgery and were randomly allotted to undergo small incision cataract surgery (SICS) and phacoemulsification. Visual acuity of postoperative patients was checked on day 1, and IOP measurement on day 7, day 30, and day 90 and CCT measurement on day 90 were done. Progression of disease and efficacy of treatment was analyzed on the basis of IOP measurement and optic disc changes toward glaucoma.
Patients who were known cases of glaucoma, with visual field defects, coexisting ocular pathologies, patients developing hypotony postcataract surgery due to improper corneoscleral tunnel or any complication during the surgery, patients who were noncompliant to the treatment protocol, and who failed to follow-up were removed from the study.
Data were entered in Microsoft Excel and analyzed using SPSS 24 Trial Version. We calculated the means and standard deviations for the linear variables and proportions for the categorical variables. The means between two groups were compared using the unpaired t-test (for different groups). The proportions were compared using Chi-square test or Fisher's exact test (for low expected cell counts). We used Mann–Whitney test for comparing the distribution of the variables and Wilcoxon matched-pairs signed-ranks test for equality of matched pairs.
| Results|| |
A correlation matrix showing correlation values and P values of the given entities is shown below. P< 0.05 is considered to be significant.
*Pearsons Correlation (P) is Significant at 0.05 Level of Significance
**Pearsons Correlation (P) is Significant at 0.01 Level of Significance
| Discussion|| |
The study, effects of cataract surgery on ocular hypertension, was undertaken to analyze if cataract surgery would help in controlling IOP in patients with ocular hypertension and if so, what are the factors effecting the change in IOP and if we can predict postoperative IOP by any preoperative indicator. Many patients with glaucoma have concurrent cataracts, and some studies have suggested that glaucoma itself is a risk factor for cataract development., A study of long-term effects of phacoemulsification with IOL implantation in normotensive and ocular hypertensive eyes indicates that IOP reduction after cataract surgery is more significant and sustained than previously thought.
The mean preoperative IOP in our study is 25.11 mmHg ± 2.75 mmHg, and preoperative adjusted IOP in patients is 24.9 mmHg (this difference in IOP makes adjusting the IOP according to CCT an important factor before the surgery). Three-month postoperative IOP is 19.23 mmHg ± 2.22 mmHg that is a 22.7% fall in IOP which is statistically significant. OHTS shows 16.5% decrease in mean postoperative IOP from preoperative IOP after cataract surgery by the end of 12 months.
The mean PD ratio of our population (as computed between adjusted IOP and ACD) is found to be 8.63 ± 1.08, and 3-month postoperative IOP is 19.23 mmHg ± 2.22 mmHg. This accounts for 5.6 mmHg reduction of IOP by the end of 3 months, proving that PD ratio is a reliable predictive factor in ocular hypertension, indirectly proving that ACD and the angle of anterior chamber have increased after the cataract surgery along with IOP reduction.
Shingleton et al. stated that phacoemulsification, particularly clear cornea phacoemulsification, seems to lower IOP more than manual extracapsular cataract extraction during early postoperative period., A study of IOP reduction after phacoemulsification versus manual SICS states that reductions are almost similar by the end of 6 months with both the procedures. Both these studies provide two different conclusions. As this study was not conducted in ocular hypertensive population, we considered analyzing it for the mean IOP in patients who underwent phacoemulsification at the end of 1 week is 18.12 mmHg ± 2.3 mmHg, 1 month is 18.9 mmHg ± 1.9 mmHg, and 3 months is 18.96 mmHg ± 1.9 mmHg and mean IOP in patients who underwent SICS at the end of 1 week is 18.83 ± 3.7 mmHg, 1 month is 20.15 ± 2.7 mmHg, and of 3 months is 19.4 ± 2.3 mmHg, which is neither clinically nor statistically significant.
In a study conducted by Cetinkaya et al., the effect of phacoemulsification surgery on IOP and anterior segment anatomy of the patients with cataract and ocular hypertension shows that increase in CCT values of the 1st week and 1st month was statistically significant, but those of the 3rd month, 6th month, 1st year, and 2nd year were not significant. In our study with ocular hypertensive population of 60 patients, mean preoperative CCT was 547.7 microns while postoperative CCT at the end of 3 months was 548 microns. This is neither clinically nor statistically significant.
| Conclusion|| |
Through this study, we conclude that adjusting of IOP according to CCT is necessary in ocular hypertensives, and PD (IOP/ACD) ratio is a valuable prognostic indicator in ocular hypertensives as well to predict postoperative IOP outcome.
Cataract surgery alone gives a reduction of IOP postprocedure. In our study, 22.7% fall is noted by the end of 3 months. Type of surgery did not effect the reduction in IOP postsurgery by the end of 3 months. Although in the initial postoperative period, phacoemulsification showed better reduction in IOP than manual SICS, by the end of 3 months, the difference was insignificant.
However, some questions still remain unanswered like what is the mechanism of IOP lowering with these procedures, have we managed to study all the possible effects of cataract surgery on ocular hypertension, and finally will the fall in IOP postprocedure be sustained? If so, for how long?
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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