Importance of optical coherence tomography before cataract surgery

Abstract

Purpose

To determine the importance of optical coherence tomography (OCT) in patients scheduled for cataract surgery who present with no pathologies in biomicroscopic fundus examination.

Design

Retrospective study.

Methods

In this study, the routine ophthalmologic examination of patients who were recommended cataract surgery was performed.Occult retinal pathologies were evaluated using OCT in patients without any pathologies in biomicroscopic fundus examination.According to whether retinal pathologies were detected on OCT, the patients were divided into two groups: normal and abnormal OCT.The findings of patients with retinal pathologies on OCT and their distribution according to age were also evaluated.

Results

A total of 271 eyes from 271 patients were evaluated.The number of patients with retinal pathologies on OCT despite normal fundoscopic examination findings was 38(14.0%).Of these patients,15(39.4%) had an epiretinal membrane,10(26.3%) had age-related macular degeneration, eight(21%) had vitreomacular traction, two(5.2%) had a lamellar hole, and 1(2.6%) patient each had a full-thickness macular hole, an intraretinal cyst, and photoreceptor layer damage.The age distribution of the patients with retinal pathologies was as follows: two patients,<60 years; six patients,60–70 years;14 patients,70–80 years; and 16 patients,>80 years.The rate of patients aged > 70 years and above was 78.9%.There was no statistically significant difference between the normal and abnormal OCT groups in terms of age, gender, the presence of systemic diseases, visual acuity, central macular thickness, and cataract type or density(p > 0.05 for all).

Conclusion

In one of seven patients evaluated, retinal pathologies were detected on OCT despite normal fundoscopic examination findings.OCT can be used to detect occult retinal pathologies that cannot be detected by biomicroscopic fundus examination before cataract surgery.

Introduction

Cataract is an important ocular pathology that causes a decrease in visual acuity across the world [1]. Cataract is seen more frequently with increasing age and constitutes one of the most common surgical operations performed by ophthalmologists [2]. Today, the surgical success of cataract is increasing through the minimal incision technique and advanced intraocular lens technology. Detailed preoperative examination is one of the main principles for a successful outcome in cataract surgery. For cataract surgery, a detailed examination is required, starting from the external ocular structures and extending to the retina [3].

Suboptimal improvements in visual acuity and visual quality after cataract surgery are important factors affecting patient satisfaction [4, 5]. Therefore, occult macular pathologies that cannot be detected by biomicroscopic fundus examination are important. Identification of these pathologies is essential for preoperative patient information, the evaluation of patient expectations, and postoperative follow-up.

Optical coherence tomography (OCT) is an important imaging method in the diagnosis and follow-up of clinical and subclinical macular lesions and pathologies [6]. Providing non-invasive, rapid, reproducible, and quantitative results, this examination is frequently preferred in ophthalmology practice [7, 8]. In a review evaluating the importance of OCT for detection and diagnosis before cataract surgery, the rate of patients with occult macular pathologies that could affect postoperative vision was reported to be 13.7% [9]. This substantial rate led us to evaluate our own patient population.

In this study, we aimed to detect occult retinal pathologies by OCT imaging in patients scheduled for cataract surgery with no retinal pathology detected in biomicroscopic fundus examination.

Methods

This retrospective, single-center study was conducted at the Ophthalmology Clinic of Yozgat City Hospital with patients scheduled for cataract surgery between June 2022 and June 2023. Before starting the study, all participants were informed about the study, and it was explained that patient files related to cataract surgery and OCT images would be evaluated and that these data would be used. This information of the patients who gave written and verbal consent was analyzed after the approval of the local ethics committee. After obtaining ethical approval (approval code: E1-23-3653), the study was initiated by following the tenets of the Declaration of Helsinki.

The study started with 288 patients scheduled for cataract surgery. Exclusion criteria were as follows: mature, white, or rubra cataracts; clear retinal pathologies on fundoscopy [drusen, retinal pigment epithelial changes, retinal pigment epithelial detachment, geographical atrophy, choroidal neovascularization, diabetic retinopathy, hypertensive retinopathy, exudate, retinal tear, retinal detachment, myelinated nerve fiber, myopic fundus, macular edema, aneurysm, retinal hemorrhage, retinal artery or vein occlusion, epiretinal membrane (ERM), macular hole, vitreomacular traction (VMT), vitreous degeneration, and vitritis]; glaucoma; uveitis; a history of intraocular surgery; corneal opacity that could obstruct the examination; <18 years of age; and cooperation difficulties. Inconsistent results and OCT images with a signal strength of < 7/10 were not included in the study.

All patients underwent a detailed ophthalmological examination before cataract surgery. Best-corrected visual acuity (BCVA) was evaluated using the logMAR chart. Intraocular pressure measurements and anterior segment examination were performed. A detailed fundus examination was undertaken half an hour after pupil dilation with a cycloplegic agent. During fundus examination, a 90-D lens was used, and the optic disc, macula, and peripheral retina were carefully scanned. After the slit-lamp biomicroscope examination was completed, the OCT examination was performed on the same day. Macular evaluation was performed with the ‘Macular Cube 512 × 128’ protocol. The presence of retinal pathologies was evaluated on the images obtained from linear sections passing through the central fovea, parafovea and perifovea using a spectral-domain OCT device (Carl Zeiss Meditec, Jena, Germany). According to the presence of retinal pathological on OCT, the patients were divided into two groups: normal OCT and abnormal OCT. The normal OCT group was defined as patients without any retinal pathology on OCT imaging. The abnormal OCT group was defined as the presence of ERM, age-related macular degeneration (AMD), drusen, VMT, lamellar hole, full-thickness macular hole, intraretinal cyst, photoreceptor layer damage, macular edema and choroidal neovascularization on OCT imaging. The central macular thickness (CMT) values ​​of all patients were also recorded (Fig. 1). Evaluation of OCT sections was performed by two researchers at different times. Inconsistent results and OCT images with a signal strength of < 7/10 were not included in the study.

Fig. 1

OCT images of different patients with retinal pathologies; A:epiretinal membrane; B:age-related macular degeneration C: vitreomacular traction

The cataract grades of all patients were determined according to the Oxford Clinical Cataract Classification and Grading System [10]. The demographic data of the patients were recorded, and the presence of diabetes mellitus, hypertension, cardiovascular disease, and cerebral vascular disease was questioned.

In the sample size calculation based on the preliminary results of our study data; effect size value was accepted as 0.4, type 1 error value as 0.01, power value as 80% and the minimum number for total participation was determined as 102. SPSS for Windows, version 22 (IBM Corp., Armonk, NY, USA) was used for statistical analyses. Continuous variables were expressed as mean ± standard deviation. The compliance of the data with a normal distribution was evaluated with the Shapiro-Wilk test and histograms. The chi-square test was used in the analysis of categorical two-group data. The independent-samples t-test and the Mann-Whitney test were conducted to evaluate the distribution of variables between groups. p < 0.05 was considered statistically significant.

Results

After the exclusion of 17 patients who did not meet the inclusion criteria, 271 eyes from 271 patients were included in the sample. The mean age of the patients was 71.45 ± 12.81 (range, 45–87) years, and 122 (45%) of the patients were female and 149 (55%) were male. The number of patients with normal fundoscopic examination findings who had retinal pathologies detected on OCT was 38 (14%), and the number of patients without any pathologies was 233 (86%). Table 1 presents the demographic findings of the normal and abnormal OCT groups and their distribution in terms of systemic diseases. There was no statistically significant difference between the two groups in terms of the rates of patients with diabetes mellitus, hypertension, cardiovascular disease, or cerebrovascular disease (p > 0.05 for all). According to the fundoscopic examination findings, seven patients with diabetic retinopathies, five patients with drusen bodies, two patients with a full-thickness macular hole, two patients with ERM, and one patient with retinal detachment were excluded from the study.

Table 1 Patients’ demographic data and the distribution of systemic diseases

The mean BCVA was 0.52 ± 0.22 (range, 0.20–1.00) logMAR in the normal OCT group and 0.56 ± 0.19 (range, 0.20–1.00) logMAR in the abnormal OCT group. There was no statistically significant difference between the groups in terms of BCVA (p > 0.05). The mean CMT values of the normal and abnormal OCT groups were 252 ± 18 (range, 218–279) micron and 261 ± 28 (range, 211–287) micron, respectively, indicating no statistically significant difference (p > 0.05). Table 2 shows the distributions of cataract types and density grades of the two groups according to the Oxford Clinical Cataract Classification and Grading System. There was no statistically significant difference between the two groups in relation to cataract type or nuclear cataract grade (p > 0.05 in all values).

Table 2 Distribution of visual acuity, retinal thickness and cataract types and density of grades

Of the 38 patients with normal fundoscopic examination findings but retinal pathologies on OCT, 15 (39.4%) had ERM, 10 (26.3%) had drusen bodies or retinal pigment epithelium changes [AMD] eight (21.0%) had VMT, two (5.2%) had a lamellar hole, one (2.6%) had a full-thickness macular hole, one (2.6%) had an intraretinal cyst, and one (2.6%) had photoreceptor layer damage. The distribution of retinal pathologies is given in Table 3.

Table 3 Distribution of retinal pathologies in the abnormal OCT group

The distribution of the 38 patients with retinal pathologies on OCT according to the age groups (< 60 years, 60–70 years, 70–80 years, and > 80 years) was as follows: two patients, < 60 years; six patients, 60–70 years; 14 patients, 70–80 years; and 16 patients, > 80 years. The rate of patients aged > 70 years and above was 78.9% (Fig. 2). The age distribution of the group without retinal pathology on OCT was as follows: 20 patients, < 60 years; 54 patients, 60–70 years; 95 patients, 70–80 years; and 64 patients, > 80 years. The rate of patients aged > 70 years and above was 68.2%.

Fig. 2

Age distribution of patients with retinal pathologies detected on OCT

Discussion

Cataract surgery is one of the most frequently performed operations across the world [3]. Adequate and appropriate evaluation before surgery is very important for postoperative success. OCT is a fast, reliable, and non-invasive method that can be used in the detection of retinal pathologies [4]. In this study, we addressed the diagnostic importance and necessity of OCT examination in patients scheduled for cataract surgery without any pathologies in the slit-lamp examination of the fundus. We consider that the possible pathologies that can be detected by an OCT examination are important for guiding and evaluating patient expectations before cataract surgery, determining the visual prognosis, and knowing the preoperative status of retinal pathologies that can develop in postoperative follow-up. In addition, although similar studies have been previously conducted in different countries, our study contributes to the literature as the first prevalence study from Turkey.

In a study in which 614 Brazilian cataract patients with normal fundoscopic examination findings were evaluated, pathologies were reported on OCT in 7.2% of patients. The frequency of the detected pathologies was as follows: ERM in 31 eyes, AMD in seven eyes, an intraretinal cyst in four eyes, a lamellar hole in four eyes, and a full-thickness hole in one eye [11]. In a study from China including a large number of patients, OCT revealed macular pathologies in 25% of the examined eyes. ERM, myopic atrophy, and dome-shaped macula with pathological myopia were the three most common macular pathologies detected, while AMD, central serous chorioretinopathy, and polypoidal choroidal vasculopathy were the least frequently reported conditions [8]. In another study including 98 patients, macular pathologies were detected in 11.2% of patients in biomicroscopic fundus examination, and maculopathy was reported in 21.4% of patients using spectral-domain OCT [12]. Although the rates of maculopathy detected with OCT were similar in the last two studies, the rate of maculopathy we detected with OCT in our study was 14%. This discrepancy may be due to the differences in patient selection. Additionally, although Pinto et al. reported the rate of retinal pathologies detected by OCT to be 7.2%, they did not provide detailed data on cataract grade or density [11]. It is known that the density and type of cataract affect the slit-lamp examination of the fundus. In both studies, OCT pathologies detected in patients with normal biomicroscopic fundus examination were evaluated [11, 12]. In another study that included 401 eyes, patients with clinically detectable fundus pathologies were evaluated, and pathologies were reported in OCT in 26.7% of all eyes, while abnormal OCT findings were found in 17.6% of patients with normal fundoscopic examination findings [13]. Klein et al. evaluated a total of 265 eyes and reported pathologies on OCT at a rate of 13%, which is similar to our findings (Table 4) [5].

Table 4 The current literature and detection rate of retinal diseases before cataract surgery

In a population-based study including a large number of patients in which vitreoretinal interface diseases were evaluated by OCT, ERM was detected in 34.1% of eyes, paravascular cysts in 20.0%, macular cysts in 5.6%, a lamellar macular hole in 3.6%, and VMT in 1.6% eyes. It was also noted that the prevalence of ERM and VMT increased with age [14]. In our study, the most common retinal pathology was ERM (15 patients, 39.4%). When we examined the age distribution of patients with retinal pathologies, we observed that the most common age groups were 70–80 years and ˃80 years. In different prevalence studies, ERM has been reported to be more common over the age of 70 years [15,16,17], which supports our findings. Similar to our study group, Jahn et al. examined the preoperative and postoperative fundus examinations of patients with senile cataracts and reported that the prevalence of ERM was higher in the examination performed seven days after cataract surgery [18]. In another study, the authors showed that ERM that could be overlooked in a biomicroscopic examination could be easily detected on OCT in cataract patients [19]. It has also been reported that the visual prognosis of patients with ERM before cataract surgery may be adversely affected after surgery. A possible mechanism is considered the rupture of the existing ERM or macular edema [20, 21]. Another important vitreoretinal interface disease detected in the current study was VMT, which was seen in eight eyes from 38 patients with retinal pathologies. Although the slit-lamp examination did not show any clear findings, the detection of VMT on OCT shows the importance of this imaging modality before cataract surgery. The detection of retinal pathologies that may develop due to VMT during postoperative follow-up also reveals the necessity of preoperative OCT evaluation.

Although the CMT was found to be higher in the abnormal OCT group in our study, there was no statistically significant difference when compared to the normal OCT group. However, it should be kept in mind that the retinal thickness may increase and the visual prognosis may worsen in the postoperative follow-up. Therefore, patients and their relatives should be informed in detail about their existing pathologies before surgery. The lack of visual improvement expected after cataract surgery and the related patient dissatisfaction can be minimized by appropriately informing patients in the preoperative period. Another important point is that in the presence of ERM detected before surgery, if visual prognosis and visual quality are affected, combined surgery may be preferred. With this procedure, the patient can be operated on in a single session rather than in two different sessions.

In AMD, while visual acuity is preserved in the early period, pigment changes and drusen deposits can be seen in the fundus. These patients are known to have affected OCT sections without significant pathologies in the fundus [22]. Kowallick et al. reported drusen bodies in four of 162 eyes and retinal pigment epithelial atrophy in one eye. The authors considered that these rates might have been low due to the high cataract densities of the patients included in their study [23]. In a study by Neto et al., AMD was detected in 10 of 98 eyes, and six of these patients had normal biomicroscopic fundus examination findings but were diagnosed with AMD using OCT [12]. In our study, AMD findings were detected in 10 of the 271 eyes. In the diagnosis of AMD, the central retina must be clearly visualized by fundus examination. Fundus examination may be difficult due to cataract or different media opacities. However, the degree and density of cataracts in the patients included in our study were not severe and dense enough to affect the biomicroscopic fundus examination of the central retina. Although some studies conducted in previous years have reported that AMD may progress in patients undergoing cataract surgery, recent meta-analyses indicate that cataract surgery has no effect on AMD progression, and visual acuity increases after surgery [24, 25]. In this sense, it may be important to detect preoperative AMD findings in patients with AMD findings without the expected increase in visual acuity after cataract surgery. Considering that AMD is a progressive process, it is also important to inform patients through an early diagnosis and follow-up.

Other pathologies detected in our study, such as a lamellar hole, a full-thickness macular hole, an intraretinal cyst, and photoreceptor layer damage, may also directly affect the visual prognosis after cataract surgery. With the preoperative identification of these pathologies, more detailed and objective evaluations can be made for patients and their relatives concerning potential visual acuity expected in the postoperative period. It is also very important to detect these pathologies to select appropriate intraocular lenses given the advances in lens technology. It is known that if multifocal or trifocal intraocular lenses are used, visual performance may not reach optimal levels in the presence of macular pathologies, and contrast sensitivity may decrease [5].

Considering the limitations of our study, the first concerns the single-center, retrospective design and relatively small sample size. Another limitation is the exclusion of postoperative follow-up and postoperative OCT imaging. It should also be acknowledged that the results obtained from the study cannot be generalized to all cataract patients since we only examined cases in which a fundus examination could be performed in terms of cataract density and grade. Lastly, in our study, only spectral-domain OCT and a single OCT image were used, and no imaging or comparison was made with different OCT devices.

In conclusion, we detected retinal pathologies on OCT in 14% of patients scheduled for cataract surgery with normal findings in the slit-lamp examination of the fundus. We were not able to establish a significant relationship between systemic diseases and retinal pathologies; however, 78% of our patients were 70 years or older, showing the importance of the age factor. Our study is also noteworthy for being the first population-based study with a large number of patients from Turkey. The detection of retinal pathologies before cataract surgery is important for appropriately informing patients and their relatives. A preoperative OCT examination can provide a more objective evaluation of visual prognosis expectation, surgical strategy, and postoperative follow-up.