Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 26  |  Issue : 2  |  Page : 111-117

Macular changes in diabetic patients using optical coherence tomography and fundus photography


Department of Ophthalmology, UP University of Medical Sciences, Saifai, Uttar Pradesh, India

Date of Web Publication13-Feb-2019

Correspondence Address:
Dr. Reena Sharma
House No. 199, Civil Lines, Etawah, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njo.njo_1_18

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  Abstract 


Aim: To identify and compare macular changes in patients with diabetic mellitus (DM) using optical coherence tomography (OCT) and fundus photography (FP). Setting and Design: This prospective comparative study was conducted at a tertiary care center. Materials and Methods: We examined 200 eyes of 107 diabetic patients with slit-lamp biomicroscopy, color FP using TOPCON fundus camera, and cirrus OCT. Fasting blood sugar (FBS), postprandial blood sugar (PPBS), and hemoglobin A1c (HbA1c) were measured. The clinical diabetic retinopathy (DR) and OCT findings were compared. Statistical Analysis: SPSS version 20, using Pearson’s Chi-square test, Student’s t-test, and analysis of variance. Results: Mean age of patients was 53.59 ± 10.8 years, with 68.2% males. Only six (5.5%) patients had type 1 DM. Mean FBS, PPBS, and HbA1c were 137.08 ± 34.4 mg/dL, 218.13 ± 70.5 mg/dL, and 6.65% ± 2.8%, respectively. The mean HbA1c of patients with OCT changes (7.08% ± 2.9%) was higher than those with normal OCT (5.52 ± 2.18) (P value < 0.001, t statistic—0.001). The retinopathy was found in 55 eyes (27.50%) on OCT and 74 (37%) eyes on FP. Of 126 eyes with normal fundus, 75 eyes (59.52%) had OCT changes. The mean central foveal, parafoveal, and perifoveal macular thickness in OCT were 260.95 ± 65.16, 322.78 ± 47.96, 281.73 ± 36.77 μm, respectively. The eyes with retinopathy had increased foveal (P < 0.001) and peripheral (parafoveal and perifoveal) thicknesses (P < 0.001). Conclusion: The OCT showed changes in the absence of clinical retinopathy in 59.2% eyes (P value < 0.001), indicating a role in detecting subclinical retinopathy. The eyes with clinical retinopathy however had a thicker fovea, implicating a more severe disease and retinopathy. Higher HbA1c values were associated with higher chances of OCT changes.

Keywords: Diabetic retinopathy, fundus photography, optical coherence tomography


How to cite this article:
Sami I, Sharma R, Sharma N, Sharma BD, Singh B. Macular changes in diabetic patients using optical coherence tomography and fundus photography. Niger J Ophthalmol 2018;26:111-7

How to cite this URL:
Sami I, Sharma R, Sharma N, Sharma BD, Singh B. Macular changes in diabetic patients using optical coherence tomography and fundus photography. Niger J Ophthalmol [serial online] 2018 [cited 2022 Jan 21];26:111-7. Available from: http://www.nigerianjournalofophthalmology.com/text.asp?2018/26/2/111/252179




  Introduction Top


Diabetes mellitus (DM) is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both (American Diabetes Association).[1] This chronic hyperglycemia of diabetes is associated with damage to various organs, including the retina. Diabetic retinopathy (DR), one of the most frequent complications of diabetes, is a major public health problem with significant socioeconomic implications, affecting approximately 50% of diabetic patients, and remains a leading cause of blindness.[2],[3],[4],[5] Patients with DR are 25 times more likely to become blind than nondiabetics.[6] The incidence of retinopathy increases with duration of the disease and the majority of patients developed some retinopathy after 20 years.[7]

Optical coherence tomography (OCT) is an innovation in ophthalmology; it is a noninvasive, fast, and noncontact investigation that gives two-dimensional cross-sectional images of the retina layers and provides quantitative measurements of the retinal thickness.[8],[9] It has evolved through generations to a resolution up to 4 µm and high level of reproducibility.[10] It has evolved from a research tool to a procedure commonly used for the diagnosis and monitoring of patients with macular disease[11] in the clinic.

OCT can be used either to qualitatively assess retinal features or to make quantitative measurements, which is especially important in the early stages of DR when the structural changes are not yet evident with slit-lamp biomicroscopy or by doing fundus fluorescein angiography.[12],[13] The purpose of the study was to identify and compare the macular changes in diabetic patients using OCT and fundus photography (FP).


  Subjects and Methods Top


The present study was a prospective, observational study conducted in patients with DM presenting to the ophthalmology outpatient department for regular fundus evaluation. The study included 200 eyes of 107 patients. Patients with DM with age between 20 and 80 years and willing to be the part of this study were included. Eyes with significant media opacities precluding a good OCT signal, macular edema due to other causes (such as age-related macular degeneration, posterior uveitis, retinal vascular occlusions, retinitis pigmentosa, and some medications) and eyes with other ocular pathologies were excluded.

All patients underwent clinical evaluation by a physician with a review of the medical history. Information about the type of diabetes, duration of diabetes, smoking, alcohol intake, current medications and any history of systemic, and ocular disease was collected. The laboratory investigations [fasting and postprandial blood glucose, glycosylated hemoglobin A1c (HbA1c)] were performed in all cases.

Visual acuity was tested using Snellen’s visual acuity chart and anterior segment examined using a slit lamp (Haag-Streit USA, Inc., Mason, Ohio, USA). Fundus evaluation was performed using a 90D lens with slit-lamp biomicroscope and Heine indirect ophthalmoscope after instilling 0.8% tropicamide and 5% phenylephrine eye drops. FP (color stereoscopic) was taken using the TOPCON TRC 50IA 35° fundus camera (TOPCON, Tokyo, Japan). The FPs were examined by a masked examiner and the DR was graded according to the early treatment DR study classification.

The macular cube scans of 512 × 128 protocol were taken with the spectral domain OCT (Cirrus™ HD-OCT 4000; Carl Zeiss Meditec, Dublin, California, USA). The software, patented by Carl Zeiss Meditec, measured the retinal thickness to produce data for further analysis. The scans were taken three times to get scans with the highest signal intensity, no centration error, and minimal segmentation error. Only scans with signal strengths ≥7 and without artifact were included. Of the macular scan, the central macular thickness, average of the four-quadrant macular thicknesses in the inner (1–3 mm) and outer (3–6 mm) rings, was used for analyses. The data were analyzed using SPSS version 20 (IBM SPSS Inc., Chicago, USA). Discrete data were analyzed using Pearson’s χ2 test for nonnormal distribution and continuous data were analyzed using Student’s t test and analysis of variance.


  Results Top


The study included 200 eyes of 107 patients. The mean age of the patients was 53.59 ± 10.89 years. Of these 107 patients, 73 (68.22%) were males and 34 (31.77%) were females. There were six (5.6%) patients (11 eyes) with type 1 DM and 101 (94.4%) patients (189 eyes) with type 2 DM. The mean duration of diabetes in the study patients was 6.67 ± 5.40 years (range 1–29 years, median 4.00 years).

The mean fasting blood sugar (FBS), postprandial blood sugar (PPBS), and HbA1c in the patients were 137.1 ± 34.4 mg/dL (range 79.9–325.0 mg/dL), 218.1 ± 70.5 mg/dL (range 113.6–542.0 mg/dL), and 6.6% ± 2.9% (range 2.8%–14.2%), respectively.

On OCT, normal macular thickness scan was found in 145 eyes (72.50%), whereas changes in scan were seen in 55 eyes. The mean central macular thickness of patients with normal OCT scan was 246.29 + 4.97 μm (230–256 μm), and that of cases with OCT changes was 265 + 75.47 μm (43–659 μm). The mean HbA1c of the patients with normal OCT was 5.52% ± 2.18%, and in the patients with OCT changes, it was 7.08% ± 2.99%. Thus, the prevalence of OCT changes was higher in patients with higher HbA1c values (P value < 0.0001) [Table 1].
Table 1 Correlation of mean HbA1c with fundus and OCT findings

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The personal history of the patients revealed that 20 (18.7%) patients had positive history of smoking, whereas alcohol intake was present in 16 (15.0%) patients. Of the 20 cases having positive history of smoking, fundus changes were present in six patients, that is, 30%, and OCT changes were present in 12 cases, that is, 60%. Out of the 16 cases having positive history of alcohol intake, fundus changes were present in six cases, that is, 37.5%, and OCT changes were present in 14 cases, that is, 87.5%. Hence, we can conclude that smoking and alcohol consumption were not found to be related to either the fundus changes or the mean macular thickness as illustrated by OCT (P values 0.15 and 0.20, respectively).

On fundus examination, 74 (37%) showed various grades of DR, whereas there was no DR in 126 eyes (63.0%) [[Table 2]; [Figure 1] and [Figure 2]]. Clinically, significant macular edema was seen in 28 eyes (13.8%).
Table 2 Clinical classification of eyes with diabetic retinopathy

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Figure 1 Fundus photograph and OCT macular scan of a patient with no diabetic retinopathy

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Figure 2 Fundus photograph and OCT macular scan of a patient with normal fundus. OCT shows decreased parafoveal and perifoveal thicknesses in right eye and decreased foveal thickness in left eye

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Various OCT changes seen in our patients have been summarized in [Table 3]. OCT showed findings such as microaneurysms, hard exudates, hemorrhage, cotton wool spots, and increased or decreased foveal and peripheral (perifoveal and parafoveal) ring thicknesses. Changes in zonal macular thickness were the most common feature of OCT changes in DR [[Figure 3] and [Figure 4]]. Of the two, decreased thickness was as common as increased foveal thickness. These OCT changes have no relation with duration of diabetes (P value = 0.34).
Table 3 Distribution of OCT changes in diabetes

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Figure 3 Fundus photograph shows absence of diabetic retinopathy. OCT macular scan shows decreased parafoveal and perifoveal thicknesses in right eye, and increased (superior outer quadrant) and decreased perifoveal thickness (remaining outer quadrant) in left eye

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Figure 4 Fundus photograph and OCT macular scan of a patient with severe NPDR with CSME. It shows microaneurysms, hard exudates, hemorrhages, cotton wool spots, and dull foveal reflex. OCT macular scan shows above lesions as hyperreflective areas in outer retina, CSME as cystoid spaces and increased macular thickness (pink and yellow color)

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In eyes with normal OCT (N = 55; 27.50%), fundus was found to be normal in 51 eyes (92.73%), whereas four eyes (7.27%) had fundus changes/retinopathy. On the contrary, out of 126 eyes with normal fundus, 75 eyes (59.52%) were having abnormal OCT, whereas normal OCT was seen in 51 eyes (40.48%) [Table 4]. Thus, the OCT showed changes in eyes in the absence of clinically apparent fundus changes (37.50%) as compared to the clinical examination of fundus, which showed changes in eyes with normal OCT (2.00%), which was highly statistically significant (P < 0.0001).
Table 4 Correlation between fundus and OCT findings

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The eyes with clinical retinopathy had a thicker fovea than those with normal fundi (P < 0.001). In the same way, average parafoveal and perifoveal thickness were significantly more in eyes with fundus changes compared to those with normal fundi (P = 0.000) [Table 5].
Table 5 Correlation of macular thickness with fundus findings

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  Discussion Top


OCT can perform high-resolution, cross-sectional imaging of the retina. A major advantage of OCT is that patients find it very comfortable because it is noncontact and the measurement time is very short. Our study compares the OCT and fundus examination for the detection of DR and describes the changes in zonal macular thickness.

The prevalence of DR has been shown to increase with age, even after adjustment for duration of diabetes.[14] Similarly, prevalence also increases with longer duration of diabetes (P < 0.0001).[15],[16],[17]

No correlation was found between the OCT changes and either the increasing age of the patient or the duration of diabetes in our study (P = 0.27 and 0.17, respectively). This is similar to the studies by Sng et al.[18] and Rodrigues et al.[19] However, increasing age has been noted to have inverse relation with macular thickness in some studies,[15] whereas others have not observed this relationship.[20],[21],[22]

We observed that patients with OCT changes had greater mean values of blood sugars, that is, FBS (P = 0.001), PPBS (P = 0.029), and HbA1c (P = 0.000) compared to those with normal OCT. This is similar to the previous studies that reported increased macular thickness with higher HbA1c levels.[23],[24] On the contrary, Lonneville et al.[25] have demonstrated that macular thickness decreases with poor metabolic control in diabetic patients with or without clinically detectable DR as high sugar cause apoptosis of ganglion cells, inner nuclear, and inner plexiform layers leading to early neurodegeneration leading to thinning of the retinal layers.

The most common lesion detected on SD-OCT was hard exudates (29.00%) followed by hemorrhages (24.50%), microaneurysms (11.00%), and cotton wool spots (3.50%) in that order. Similar findings were noted in the study conducted by Gella et al.[26] But the most common findings on OCT noted in our study was decreased parafoveal and perifoveal thickness (36.50%) followed by increased parafoveal and perifoveal thickness (32.50%). We observed more patients with decreased parafoveal thickness than increased thickness, which is similar to the observations reported by Asefzadeh et al.,[27] Biallosterski et al.,[28] Nilsson et al.,[29] and Verma et al.[30] The contradictory results, that is, increased macular thickness, were shown in some studies such as Schaudig et al.,[31] Lattanzio et al.,[32] Sugimoto et al.,[33] and Fritsche et al.[34]Recent evidence suggests that the selective thinning of inner retinal layers is due to the early neurodegenerative component in patients with minimal DR[35] and thicker macula is due to microvascular abnormalities.[36],[37] The OCT can thus be successfully utilized for objective monitoring of the macular thickness before and after therapy in patients with DR.

We thus found that OCT can be used for preclinical evaluation and follow-up of DR patients. The OCT changes may even precede the development of fundus changes. Early changes in macular thickness in particular can be found in diabetic patients without retinopathy.[36] These changes may be related to both neuronal and vascular abnormalities that occur in the early stage of diabetic retinas.[38] We also suggest that if there is abnormal macular thickening or thinning on OCT, the patient should be followed up more closely.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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