Cataract extraction is one of the most commonly performed surgery. Over recent years, the outcome of cataract surgery has improved due to consistent innovations in instrumentation, lens design, and surgical technique. [1] Phacoemulsification implantation of a foldable intraocular lens (IOL) is the currently preferred technique. [2] The procedure is efficient, and uneventful surgery is generally associated with good visual results. [3, 4, 5]

Cystoid macular oedema following cataract surgery was initially reported by Irvine in 1953 and demonstrated angiographically by Gass and Norton in 1966, so it is known as the Irvine-Gass syndrome. [6, 7, 8]

Postoperative cystoid macular oedema is a complication of uneventful cataract surgery. Though enhanced surgical procedures have diminished the frequency of cystoid macular oedema, it remains a reason for ominous visual outcomes post-surgery. Nevertheless, cystoid macular oedema (CME) may develop, and this can result in suboptimal postoperative vision. [9, 10, 11]. The incidence of clinical CME following modern cataract surgery is 0.1-2.35%. [12]

Macular oedema has been contemplated for long with fluorescein angiography. It is realized that in majority of cases following uncomplicated cataract surgery, CME would happen by the 4-6thweek and resolve spontaneously. Fundus fluorescein angiography has been the 'gold standard' for diagnosing subclinical cystoid macular oedema; nonetheless, non-invasive cross-sectional imaging of the retina with optical coherence tomography (OCT) is similarly compelling at distinguishing the condition.

 OCT is valuable in deciding subclinical cystoid macular oedema in case of uncomplicated cataract surgery patients; it detects the presence of retinal thickening and intra-retinal cysts very soon after surgery, thereby facilitating earlier diagnosis and treatment of postoperative CME.OCT done at different time interims post cataract surgery demonstrate that after an uncomplicated cataract surgery, the increase in retinal thickness and macular volume achieved the most extreme in months 1 and 2 and was probably going to diminish after month 3 on. The occurrence of CME was 3 %, however clinically significant CME was detected in 1 % of the cases only. [13]

OCT has all the earmarks of being a valuable strategy to uncover clinically significant postoperative CME and is corresponding to fluorescein angiography.  Utilizing no less than 40% increases in retinal thickness from baseline on OCT might be a substantial, objective, and uniform method for characterizing CME. [14]

Cystoid macular oedema can occur after uncomplicated surgery in patients with otherwise healthy eyes, after complicated surgery, or after surgery in patients with ocular diseases such uveitis or diabetic retinopathy. [15] Among these, the improvement of CME taking after cataract surgery in diabetic patients is absolutely a matter of worry with steadily increasing cases of diabetes in the populace and especially in India. While the development of CME in patients with diabetic retinopathy (DR) is a well-established certainty, the development of the same in eyes without DR is absolutely a matter of intrigue and alert.

Study Site: Ophthalmology OPD tertiary care referral hospital, pune.

Study Population: All adult patients who underwent uncomplicated phacoemulsification surgery and few of them having type 2 diabetes Mellitus included.

Study design: “A prospective, observational comparative study.”

Inclusion criteria: 

1. Patients with Age> 18 years
2. Patients who are, scheduled for phacoemulsification cataract surgery within at the most 28 days after the first evaluation and some of them are having type 2 diabetes mellitus and some with diabetic retinopathy.
3. Patients with ,Best corrected visual acuity perception of light or more
4. Patients with, Central macular thickness measured on cirrus OCT </= 310 microns at baseline
5. Patients who were willing to take part in the study.

Exclusion criteria:

1. Patients with, Type 1 diabetes Mellitus and Eyes underwent any major intraocular surgery in past 6 months.
2. Eyes with any significant extra-lenticular media opacity e.g. corneal opacity, vitreous hemorrhage etc. that interfered with patient’s vision and was not going to be addressed as a part of present protocol strategy.
3. Eyes of Patients harboring any serious systemic comorbidity e.g. End stage renal failure, Ischemic heart disease, uncontrolled hypertension etc. that had prevented the patient from attending the scheduled follow-up visits.
4. Patients with, any other ocular co-morbidity that is likely to confound the results of the current study e.g. glaucoma, retinal vascular occlusions etc.
5. Patients with posterior capsular rent during cataract surgery.
6. Patients with proliferative diabetic retinopathy

METHODOLOGY:

Method of investigation: The study population will undergo

Pre-operative

1. Evaluation of Best Corrected Visual Acuity - distant and near and refraction. It was done by using Snellen’s visual acuity charts
2. External ocular examination ,
3. Detailed slit-lamp bio microscopy,

Optical Coherence Tomography:

Optical coherence tomography was done using the Zeiss Stratus OCT scanners (Carl Zeiss Meditech, Inc, Dublin, California) after dilating pupils fully with tropicamide (0.08%) and phenylephrine (5%) eyedrops  in every patient using macular cube 512 × 128 and macular thickness was noted. The central macular thickness was defined as the distance between the innermost foveolar surface and the outermost foveolar surface and was measured using the manually assisted technique of the program with the OCT system software, with the fixation point regarded as the foveal center.

1. Central macular(sub-field) thickness[CMT]
2. Macular cube volume[CV]
3. Average macular cube thickness[AMT]

Ocular biometry for IOL power calculation

The recruited patients, after having undergone the baseline investigations and consultations, would be divided into following groups:

1. Group A: Patients with no diabetes mellitus. (n: 32)
2. Group B: Patients with type 2 diabetes mellitus with no diabetic retinopathy (n: 32)

Intra-operative: Phacoemulsification Technique:

Postoperative Treatment

A topical antibiotic and Prednisolone acetate 1% eye drops every 6 hourly with tapering doses over one month was prescribed along with oral preparation of ciprofloxacin 500 mg and a combination of Ibuprofen 400 mg and paracetamol 325 mg for two times a day for 5 days and 3 days respectively.

Post-operative follow – up:

Patients were followed up on Day 1, 1 week, 4 week & 12 week post operatively and OCT was done at baseline before cataract surgery and with every post-operative follow up visit following surgery.

1. Best corrected visual acuity
2. Slit Lamp Bio microscopy
3. Optical Coherence Tomography
4. The data collected would be recorded as follows:

This prospective observational comparative study was conducted at tertiary care referral hospital Pune. Sixty four eyes of patients fulfilling the inclusion criteria attending the Ophthalmology Department.

Sixty four eyes of patients underwent uncomplicated phacoemulsification of which Thirty two eyes of  non-diabetic patients(group 1) and remaining thirty two eyes of patients were having  diabetic   (group 2). The central (sub-field)macular thickness(CMT) ,Macular cube volume (CV),average macular cube  thickness (AMT) ,cystoid macular edema of the patients was assessed preoperatively and  postoperative on  day 1,week 1,week 4 and week 12 with help of OCT.

The baseline characteristics are as follows.

Table 1 BCVA (Log mar visual acuity chart) for distant vision wise distribution of the study subjects in the two groups preoperative and post-operative.

Table no 5 and Fig 5 represent the preoperative BCVA for distant vision wise distribution of  subjects in two groups, in the study shows in group 1 mean 0.40 with standard deviation of 0.16 and in group 2  mean  0.43 with standard of deviation of 0.14.  BCVA increase over time was different for the diabetic and the nondiabetic subgroups.

Conclusion: - By using 2 independent sample t-test p-value < 0.05 therefore there is significant difference between BCVA at week 1 and week 4.

Table 6 – BCVA for near vision wise distribution of the study subjects in the two groups.

Conclusion: - By using Fisher’s exact test p-value < 0.05 therefore there is significant difference between group 1 and group 2 with respect to near vision.

Table 2 – Comparisons of mean central macular (subfield) thickness (CMT) in the study groups on OCT.

The above table 7 and Fig 7 shows that mean value of central macular (sub-field) thickness (CMT) before surgery in group 1 was 249.38 µM with a standard deviation of 19.64 µM and in group 2 was 257.66 µM with a standard deviation of 23.65 µM. This difference was not statistically significant.

Conclusion: - By using 2 independent sample t-test p-value < 0.05 therefore there is significant difference between mean CMT at week 1. For intragroup in our study p value is Significant (paired t-test used).

Table 3- Showing comparison of mean macular cube volume (CV) in the study group on OCT.

The above table 8 and Fig 8 shows that mean value of macular cube volume ( CV)  before surgery in group 1 was 9.44 µM with a standard deviation of 0.38 µM and in group 2 was 9.67 µM with a standard deviation of 0.55 µM. This difference was not statistically significant.

Conclusion: - By using 2 independent sample t-test p-values < 0.05 therefore there is significant difference between mean CV at week 1. In the study group intragroup p value also Significant (paired t-test used).

Table 4 - Comparisons of mean average macular thickness (AMT) in the study groups on OCT.

The above table 9 and Fig 9 shows that mean value of average macular cube thickness before surgery in group 1 was 267.94 µM with a standard deviation of 12.70 µM and in group 2 was 274.34 µM with a standard deviation of 13.92µM. This difference was not statistically significant.

Conclusion: - By using 2 independent sample t-test p-value > 0.05 therefore there is no significant difference between mean AMT at pre op to week 12.  For intragroup p value is Significant (paired t-test used).

This prospective observational non-interventional study was undertaken with the aim of assessing the changes in macular thickness before and after cataract surgery in diabetic and non-diabetic patients. This study was conducted at the Department Ophthalmology and included 64 consecutive patients (64 eyes) attending the Screening OPD from october 2018 to may 2019. Among the patients included in the study, 32 patients were non-diabetic (group 1) and 32 were diabetic (group 2).

Macular edema is a common cause of unfavorable visual outcome after cataract surgery.(26)Diabetes has been associated with an increased incidence of postoperative macular edema.

OCT has been shown to be highly reproducible in measuring macular thickness in normal individuals and diabetic patients. (17) since OCT can assess macular thickness quantitatively; it can detect subtle changes of macular thickness and is especially useful in mild cases. Due to the non-invasive and non-contact properties of the OCT, obtaining preoperative and postoperative OCT scan at day 1, 1 week, 4 week, 12 week allowed the researcher to quantify the changes in foveal thickness and to follow the progression in the present study.

Informed consent was taken from all the patients recruited in the study.

Despite of the large number of diabetic patients undergoing cataract surgery in India, studies assessing changes in macular thickness in Asian Indian diabetic patients undergoing phacoemulsification surgery have been few in number. Most of research done in this regard has been done in western population, e.g. study done by Stephen J et al in analysis of macular oedema after cataract surgery in patients with diabetes using optical coherence tomography included north American population.(26) Few of the prominent Indian studies belong to Eastern part of India - study done by Ghosh S et al comparing MSICS and Phacoemulsification surgery effect on central macular thickness which concluded that in spite of the greater theoretical risk of increased postoperative inflammation following MSICS, there was no evidence of cystoid macular edema, either clinically or on OCT. However, chance of sub-clinical increase in CMT was more following MSICS compared to phacoemulsification.(18) Generally there is paucity of similar studies conducted in past that include western Indian populations in our study.

  In  our study among 64 eyes of patients included 44 were males(68.75%), 20 were females(31.25%), sex distribution in our study was skewed ,similar studies have been done in past with unequal distribution of gender. For example study done by Hayashi et al examined 39 were male and 29 women. They carried out study to quantitatively examine changes in macular oedema after phacoemulsification surgery in eyes with diabetic retinopathy (DR) and in eyes without DR. They concluded that the degree of diabetic macular oedema increases up to 3 months after cataract surgery, but there after decreases gradually. Grade of diabetic macular oedema also worsens up to 3 months, but certain percent of macular oedema that occurs after surgery resolves spontaneously. These changes are more prominent in eyes with DR than in eyes with no DR. there were also no statistically significant differences between sex distributions like in present study .so the unequal gender distribution not going to affect the outcome of the study. (19)

In our study we have studied change in macular thickness in diabetic and non-diabetic population after cataract surgery done by phacoemulsification technique alone, unlike the studies by Ghosh et al, which wakes a similar comparison in patients undergoing cataract surgery by phacoemulsification and small incision cataract surgery [SICS] Techniques.(18)

Use of OCT to detect post cataract surgery cystoid macular edema is well validated by plethora of studies in literature. In a study done by Ching et al, 131 eyes of 131 patient’s presence of senile cataract in patients older than 50 years old Cataract extraction required because of visual impairment clear fundal examination before cataract surgery were studied in an ophthalmology clinic. They also concluded that OCT was useful in detecting and confirming clinical CMO after cataract surgery (21)

Many studies done in past assessing the change in macular thickness in diabetic patients perioperatively only compute the absolute increase in Central macular thickness[CMT], and in our opinion, disregard the baseline anatomical variation. In our study we accounted for the baseline variation in Central macular thickness of diabetic and non-diabetic patients by computing a percent change in Central Macular Thickness over baseline thickness- in our study, central macular (sub-field) thickness [CMT] at 1 week in diabetic patients was significantly higher than in non-diabetic patients. The percent change in central macular thickness at 1 week in group 1 was (non –diabetic group) 6% where as it was 13 % in group 2(diabetic group). A studies with similar approach are few- e.g. a study done by Degenring et al which assessed 108 eyes by optical coherence tomography preoperatively and 1 day, 1 week and 4 weeks after phacoemulsification showed significantly increased Minimal Foveal Thickness measurement in diabetic patients showing a tendency towards increase in retinal thickness than non-diabetic subjects. The percent change  in minimal foveal thickness  in non-diabetics at  day 1, 1week and 4 week  it was  4.8%, 32% and 24% respectively  whereas in diabetic subject at day 1 ,1 week and 4 week it was 17.4%, 21.7%  and 33.3 % respectively. They also concluded that, the foveal thickness at and volume demonstrated increase within 4 weeks after uncomplicated cataract surgery. (22)

In our study the significant increase in macular thickness was at 1 week and thereafter the difference between the two groups lost statistical significance, although the trend in diabetic patients of having higher CME continued through the study period. Different studies show different time patterns of having peak macular thickness. The study done by Kwon S II et al carried out evaluation of changes of macular thickness in diabetic retinopathy after cataract surgery ,in 104 eyes of diabetic patients  in which Macular edema occurred in 19 eyes (18%) ,among 19 eyes 12 eyes ( 63% )  developed  macular edema developed at 1 month after surgery. The incidence of macular edema after cataract surgery in diabetic patients was 18%, which was having peak incidence at 1 month post-surgery. (23) Such clinical observations may have impact on the perioperative monitoring strategies for macular oedema and time patterns and a spontaneous resolution, as was seen in our study would influence a choice for more aggressive therapies of macular oedema, e.g. intravitreal steroids.

In our study the macular cube volume [CV] in group 1 and group 2, the % increase from baseline at 1 week in group 1 was 1.6% and group 2 was 3%, the difference between two groups was statistically significant. Previously there were very few studies done which also study changes in macular cube volume.  A similar study was done by Degenring et al which assessed 108 eyes by optical coherence tomography preoperatively and 1 day, 1 week and 4 weeks after phacoemulsification and also studied central foveal thickness change and macular volume change after phacoemulsification. They also concluded that in non-diabetic group at week 1 there was 9.9% increase in volume whereas in diabetics it was 16.7 %. Similar to our study. We propose that having macular cube volume calculation in addition central macular thickness has high functional implications (22)

In our study there was no stastically significant difference in average macular thickness [AMT] between the two groups, at any time of post-operative follow up to 12 week. However in diabetic group there is a trend in terms of increase in AMT, up to postoperative 4 week. Most of the studied done in past studied mainly central macular thickness [CMT] only and similar studies  which included average macular cube thickness are few in number. A study done by Saxena S et al revealed that (conclusions) and concluded that cube average thickness provides a global perspective of defining DME within the macular cube (24)

In our study the incidence of cystoid macular oedema, in group 1 at  1week  was 6% which was also same at 4 week whereas in group 2 it was found to be 28% at 1 week and 31 % at 4 week ,the incidence of cystoid macular oedema in group 2 ( diabetics) was more compared to group 1  (non –diabetic ),these finding are corroborated by the study done  by Katsimpris et al in which  central foveal thickness was studied before and after cataract surgery using OCT in  49 eyes from normal patients and 49 eyes diabetic patients  . The incidence of cystoid macular edema (CME) was 4.0 % and 28.6 % for the control group and the diabetic group, respectively. They also concluded that eyes of diabetic patients present higher CFT and a higher incidence of CME after cataract surgery on OCT examination compared to eyes of healthy controls. (25)

In study done by Kim S J et al, the incidence of macular edema on OCT was 22%, which at follow up period of 1 month in Diabetic eyes which also have a high incidence of increased center point thickness on OCT after cataract surgery.(26)The patient having presence of more cystoid spaces and more increased in central macular thickness, as was seen in our study would influence choice  for more aggressive therapies of macular oedema, e.g. intravitreal steroids.

In our study percentage change in the BCVA between group 1 and group 2   (estimated using LOGMAR visual acuity chart) at 1week and 4 week was statistically significant. However, this difference was no longer statistically significant at 12 week. At 1 week and 4 week % change in BCVA in group 1 was 91% and 93.98% and in group 2 it was 77.37% and 91.26% respectively.

There were similar studies done in past, study done by Degenring et al assessed. There was also a significant difference in visual acuity of non-diabetic and diabetic subjects at 1week and 4 weeks after surgery, however they studied it in stastical mean value in logmar visual acuity chart which was in group 1 at 1 and 4 week was 0.13 ±0.12 and 0.09± 0.11 and in group 2 ,at 1 and 4 week it was 0.20± 0.24 and 0.20± 0.22 respectively. (22). We computed the percent change in same as we believed that it accounted for the baseline variations in visual acuities in patients with varying grades of cataract.

The present study also found that statistically significant difference between study group in near vision before and after surgery. In group 1 at postoperative day 1, 30 patients had near vision n6, 2 patients had near vision n8. At postoperative 1 week, 30 patients had near vision n6, 2 patients had near vision n8.  At 4 week 30 patients had near vision n6, 1 patient had near vision n8 and 1 patient had near vision n10. In group 2 at post-operative 1 day, 21 patients had near vision n6, 9 patients had near vision n8, 2 patients had near vision n10.  At 1 week postoperatively 22 patients had near vision n6, 8 patients had near vision n8,2 patients had near vision n10. At post-operative 4 week 22 patients had near vision n6, 9 patients had near vision n8, 1 patient had near vision n10. The increased in central macular thickness and development of cystoid macular edema, influences the near visual acuity of patients.

Diabetic patients are a challenge to the ophthalmologists as they are more likely to develop macular edema after cataract surgery than non-diabetic patients. It is the most important cause for uneventful visual outcome after surgery. Early detection of macular edema helps in prevention and treatment. Optical Coherence Tomography is an important tool in monitoring the progression of the cystoid macular edema after surgery such as phacoemulsification. Pre-operative OCT testing provides a baseline for post-operative comparison. This strategy helps the clinician in early detection of increase in macular thickness and cystoid macular edema. This study has demonstrated change in central macular thickness, change in macular cube thickness, change in average macular cube thickness, and appearance/ worsening of cystoid macular edema in both non –diabetic and diabetic patients.  The incidence of optical coherence tomographically evident cystoid macular edema was 28% at 1 week and 31 % at 4 week among the diabetic patients. The incidence of substantial increase in macular thickness was associated with impaired visual acuity. This study has demonstrated that the increase in the macular thickness and macular edema is more prominent in diabetic eyes than non-diabetic eye at 1 week after surgery. The patients having more increased of central macular thickness and presence cystoid macular edema may need more aggressive treatment than other patient for example intravitreal steroids. OCT is noninvasive and has good reproducibility and thus helps in monitoring the anatomical changes of the retina in the postoperative period. Owing to its high sensitivity, OCT is suitable to demonstrate the postoperative subtle changes of the macular thickness and subclinical macular edema.  

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