Hyperglycemia activates several biochemical pathways leading to oxidative stress, the hallmark in the pathogenesis of diabetic retinopathy [
The term oxidative stress refers to an imbalance between the antioxidant defense system of the cell and the intracellular amount of harmful reactive oxygen species (ROS). Oxidative stress may result from endogenously produced ROS (caused by hyperglycemia) or by external sources (caused by cataract operation). Cataract surgery influences the intraocular balance in different aspects. It is one of the well-known sources of free radicals [
As a result of free radicals accumulation, the risk of developing or worsening of macular edema following cataract surgery is higher in patients with diabetes than in patients without diabetes and correlates well with the progression of diabetic retinopathy [
There are some controversies in the results of the studies reporting developed increase in central macular thickness (CMT) or macular edema after cataract surgery in patients with diabetes but no diabetic retinopathy (in diabetic patients without diabetic retinopathy). In a retrospective database study performed on more than 4500 diabetics without preoperative macular edema, the postoperative incidence of macular edema was reported 4%, higher than in the population without diabetes (
On the contrary, a recently published meta-analysis showed no statistically significant increase in CMT values after cataract surgery in diabetic patients without diabetic retinopathy at 1, 3, and 6 months after cataract extraction [
This clinical study was designed to compare visual function (visual acuity, retinal sensitivity) and morphologic retinal changes (macular thickness) before and after cataract surgery in diabetic patients without diabetic retinopathy in comparison to nondiabetic patients.
This prospective, comparative study was designed to assess the clinical outcome of diabetic patients without diabetic retinopathy undergoing cataract surgery. Participant enrolment and treatment took place at the Eye Hospital, University Medical Center Ljubljana, Slovenia. The study was approved by the Republic of Slovenia’s National Medical Ethics Committee and conducted in accordance with the Declaration of Helsinki 1964. Written and fully informed consent was voluntarily provided by all participants prior to enrolment in the clinical study.
Inclusion criteria were clinically significant age related cataract of LOCS III (lens opacities classification system) grade N3, diabetes mellitus type II for the group of diabetic patients, and no diabetes as proved by fasting blood glucose test for the control group.
Exclusion criteria were any other ocular pathology except cataract.
Eighteen eyes of diabetics without diabetic retinopathy and 10 eyes of nondiabetic patients were included in the test and the control group, respectively.
Preoperative visit evaluation was followed by a standard microinvasive cataract surgery. Postoperative follow-up visits were scheduled for day 1, 1 month, 3 months, and 6 months postoperatively.
A standard cataract surgery with phacoemulsification was performed by one of two surgeons (NVV, VP) as follows: preoperatively, topical installation of NSAID (Naclof®, Alcon, Texas) three times in 10-minute intervals, corticosteroid and antibiotic (Maxitrol®, Alcon, Texas) three times in 10-minute intervals, topical mydriatics, a combination of two eye drops, 1% tropicamide (Mydriacyl 1%®, Alcon Pharmaceuticals, Hünenberg, Switzerland) and generic 2,5% phenylephrine, three times in 10-minute intervals, followed by topical anesthetic and iodine application performed in 5-minute intervals. After sterile preparation, a 2,2 mm clear corneal incision, intracameral lidocaine, intracameral hydroxypropyl methylcellulose (Acryvisc®, Zeiss, Oberkochen, Deutschland), and 5–5.5 mm continuous curvilinear capsulorhexis were followed by phacoemulsification performed at the same phacomachine (Millenium®, Bausch & Lomb Storz) in all patients, aspiration irrigation, and hydrophobic IOL implantation. Intracameral antibiotic (1.0 mL generic vancomycin used off-label) was administrated at the end of the surgery. Postoperatively, topical NSAID (Naclof, Alcon, Texas) to prevent cystoid macular edema [
Preoperative visit evaluation in addition to routine comprehensive ophthalmological exam included best corrected visual acuity using the ETDRS charts (4-meter 2000 series revised ETDRS chart (Precision Vision®, La Salle, USA)), measurement of retina sensitivity by microperimetry (MP-1 Micro Perimeter, Nidek), and measurement of macular thickness, using optical coherence tomography (Topcon 3D OCT-1000, Tokyo, Japan) (Figure
(a) ETDRS chart for best corrected visual acuity test. (b) Macular photography with the microperimetry test area. (c) Optical coherence tomography of macula and ETDRS rings thickness measurements, blue arrow to the central subfield, encircled blue central 5-field area.
At all follow-up visits, the complete ophthalmological exam with best corrected visual acuity using the ETDRS charts and the optical coherence tomography of the macula were repeated. Additionally, microperimetry was repeated at 1, 3, and 6 months after surgery.
The scanning protocol for optical coherence tomography used in this study was the Fast Macular Thickness program (Topcon 3D OCT-1000, Tokyo, Japan), which creates a retinal map algorithm consisting of six radiating cross-sectional scans, each of 6 mm length, that produces a circular plot in which the fovea is a central circular zone of 1 mm diameter. Superior, nasal, inferior, and temporal parafoveal zones represent annular bands in these respective sectors. There are other two concentric zones, the first having a diameter of 3 mm and the second one of 6 mm. The nine zones (the central zone is named field 1, the first annular ring fields 2–5, and the second annular ring fields 6–9) have been called ETDRS-type regions because of their similarity to zones of analysis of photographs by ETDRS graders (Figure
Microperimetry was performed after pupil dilatation with automatic fundus-related perimeter (MP-1 Micro Perimeter; Nidek Technologies, Padova, Italy) (Figure
The statistical analysis of the data was performed using SPSS (SPSS, Inc., Chicago, IL) for Windows 11.5 package program. Power analysis was performed to detect the sample size. Mean standard deviation (SD) was used to describe quantitative data. Student’s
Twenty-eight eyes of twenty-eight patients, with a mean age of
Demographics of all patients included in the study with type of diabetes treatment and percentage of accompanying systemic diseases.
Number of eyes | Age (years) | Duration of diabetes (years) | Therapy for diabetes (% of patients) | Systemic diseases (% of patients) | |
---|---|---|---|---|---|
Diabetics without DR | 18 | 57–83 | 1–30 | Insulin (17%) | Arterial hypertension (83%) |
| |||||
No diabetes | 10 | 60–73 | NA | NA | Arterial hypertension (40%) |
| |||||
|
NA: not applicable.
The cataract surgery was uneventful in all eyes. The mean phacoemulsification time was 2,73 seconds, without statistically significant difference between the groups.
Table
Mean best corrected visual acuity (BCVA) in ETDRS letters preoperatively and at all postoperative follow-ups.
BCVA | The association between preoperative and postoperative (6 months) BCVA | |||||
---|---|---|---|---|---|---|
Preoperative | Postoperative | |||||
Day 1 | 1 month | 3 months | 6 months | |||
Diabetics without DR | 64.2 ± 5.6 (SD) | 75.5 ± 5.9 (SD) | 80.7 ± 3.6 (SD) | 80.9 ± 3.9 (SD) | 81.0 ± 2.9 (SD) | |
No diabetes | 61.9 ± 8.9 (SD) | 78.1 ± 3.9 (SD) | 79.5 ± 3.5 (SD) | 80.1 ± 2.1 (SD) | 82.1 ± 3.7 (SD) | |
Significance level if
Best corrected visual acuity (BCVA) in ETDRS letters before (exam 1) and after cataract surgery: 1st day (exam 2), 1 month (exam 3), 3 months (exam 4), and 6 months (exam 5).
The mean best corrected visual acuity ETDRS in the diabetics without diabetic retinopathy group eyes improved for 16.8 ETDRS letters or 26.2%,
At OCT examination, mean retinal thickness in the central field (field 1) in the diabetic group changed from 238.6
Central macular thickness (CMT) in
CMT ( | The association between preoperative and postoperative (at 6 months) BCVA | |||||
---|---|---|---|---|---|---|
Preoperative | Postoperative | |||||
Day 1 | 1 month | 3 months | 6 months | |||
Diabetics without DR | 238.6 ± 29.0 (SD) | 233.7 ± 30.2 (SD) | 244.5 ± 24.0 (SD) | 251.3 ± 27.8 (SD) | 255.2 ± 31.5 (SD) | |
No diabetes | 247.6 ± 25.0 (SD) | 240.2 ± 23.0 (SD) | 247.5 ± 21.0 (SD) | 247.6 ± 20.0 (SD) | 261.7 ± 29.0 (SD) | |
Significance level if
Central macular thickness on optical coherence tomography in
Observing a wider macular area, namely, the central five fields (Figure
Mean retinal thickness of the macular 5 fields (RT 5 fields) at optical coherence tomography in
RT 5 fields ( | RT 5 fields Day 1 | RT 5 fields 1 month | RT 5 fields 3 months | RT 5 fields 6 months | The association between preoperative and postoperative (6 months) OCT RT 5 fields | |
---|---|---|---|---|---|---|
Diabetics without DR | 284.2 ± 19.1 (SD) | 280.7 ± 19.1 (SD) | 290 ± 19.4 (SD) | 294 ± 16.7 (SD) | 291.2 ± 16.8 (SD) | |
No diabetes | 284.0 ± 18.0 (SD) | 280.3 ± 18.0 (SD) | 286.2 ± 15.0 (SD) | 283 ± 13.0 (SD) | 288.1 ± 20.0 (SD) | |
Significance level if
Mean retinal thickness of the macular 5 fields on optical coherence tomography in
Investigations of a 58-year-old diabetic patient. (a) One month postoperatively: above mean thickness in the central 5-field macular area at OCT (blue circle), BCVA, and below microperimetry sensitivity. (b) Six months postoperatively: above increased mean thickness in the central 5-field macular area at OCT (blue circle), decreased number of ETDRS letters of BCVA, and below microperimetry mean sensitivity decrease (arrow).
Mean sensitivity on microperimetry showed relatively stable improvement in the diabetic group when comparing preoperative exam to 1-, 3-, and 6-month postoperative follow-up exams; the average difference was 3.62 dB (SD 2.31), 3.69 (SD 2.39), and 3.45 (SD 2.34). Direct comparison of the mean sensitivity improvement after cataract surgery between the DM2 without DR and the control eyes groups was not done, because the absolute improvement depends mainly on the severity of the cataract, and the groups were not balanced on the basis of cataract severity. However, when the comparison was made among the postoperative follow-up exams between the groups, a decrease in the mean sensitivity was found in the DM2 without DR group eyes (Figure
The microperimetry testing area corresponds to the five-field retina on the OCT, so the above results were paralleled and correspondent.
In our study, we demonstrated that cataract surgery in diabetic patients without diabetic retinopathy did not influence the good visual acuity outcome after cataract surgery. However, slight increase in paracentral macular thickness and a corresponding decrease in mean retinal sensitivity after 6 months were present in diabetics without diabetic retinopathy group eyes and not in the control group.
Our study included both functional and morphological examination methods of the macula, in order to try to find clinical and subclinical difference after cataract surgery between nondiabetic and diabetic patients without diabetic retinopathy. A wider macular area was examined additional to the central macular thickness, and macular sensitivity test was added to the visual acuity testing, which, according to our knowledge, was not analyzed in previous published studies.
In our study, both groups, diabetics and nondiabetic patients, showed equal statistically significant thickening of the central macular subfield 6 months after cataract operation, diabetics for 16.6
Additional analysis of the ETDRS subfields at OCT of the macula showed slightly more pronounced thickening in the cumulative central 5 fields in the diabetic group 6 months after surgery in comparison to the control group. The area covered by central 5 fields corresponds to the testing area of the automated microperimetry retinal sensitivity testing [
Several authors reported increased central macular thickness in diabetic patients with diabetic retinopathy after cataract surgery. Kim et al. studied changes in central point thickness on optical coherence tomography (OCT) after uncomplicated cataract operation in diabetic patients with different status of the retina and reported thickening for more than 30% in 22% of the participants [
Our results show an increase in the central 5-field area of macular thickness and a corresponding decrease in retinal sensitivity in diabetic patients without diabetic retinopathy 6 months after cataract surgery not observed in the control group and not reported before. Both OCT measurements and microperimetry are known to show diurnal and long term variability; thus, the results need to be interpreted carefully [
There are certain limitations of this study. There were a relatively small number of cases included, and the optical coherence tomography measurements were not repeated.
In conclusion, the combination of increased macular thickness in the central 5-field macular area and decreased retinal sensitivity in diabetics after cataract surgery in the era of premium intraocular lenses and refractive lens procedures, where a perfect status of the macula is desired, might be of interest. On the other hand, the improvement of the best corrected visual acuity and only minimal functional macular changes ease the decision to perform cataract surgery in diabetic as in healthy patients when appropriate. However, diabetics should be treated with additional caution, the use of topical NSAID after cataract surgery should be considered, and follow-up visits could be more accurate with additional measurements of macular morphology and function.
Whether changes in macular thickness and retinal sensitivity observed in diabetic patients without diabetic retinopathy in our study could progress to clinical important consequence over a longer period of time remains to be elucidated in studies with longer follow-up and higher number of subjects enrolled.
The authors declare that there is no conflict of interests regarding the publication of this paper.