Taiwan Journal of Ophthalmology

ORIGINAL ARTICLE
Year
: 2013  |  Volume : 3  |  Issue : 3  |  Page : 103--107

Optical coherence tomography study of foveal microstructure after successful retinal detachment surgery


Hsuan-Chieh Lin, Po-Ting Yeh, Jen-Shang Huang 
 Department of Ophthalmology, National University Hospital, College of Medicine, National University, Taipei, Taiwan

Correspondence Address:
Jen-Shang Huang
Department of Ophthalmology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Number 7, Chung- Shan South Road, Taipei
Taiwan

Abstract

Purpose: To evaluate foveal anatomical abnormalities after the successful repair of rhegmatogenous retinal detachments (RRDs) and to investigate the relationship between foveal microstructural changes and postoperative best-corrected visual acuity (BCVA). Materials and methods: This study was a retrospective consecutive case series comprising all RRD patients with anatomical reattachment performed bya single surgeon fromJanuary 2009 toJune 2010. Complete medical and ophthalmic histories, BCVA, duration of symptoms, number of breaks, extent of the retinal detachment (RD), lens status, and type of surgery were preoperatively recorded. The main outcome measurements for data analysis were postoperative BCVA and optical coherence tomography (OCT) imaging of the foveal microstructure. Results: Clinical data and OCT images were obtained from 83 eyes of 80 patients who underwent successful RRD surgeries. Anatomic foveal abnormalities were identified in 72% of eyes, including disruption of the junction between the inner and outer photoreceptor segments (IS/OS) in 59% of all cases with or without external limiting membrane (ELM) disruptions, residual subretinal fluid (7%), epiretinal membranes (22%), cystoid macular edema (7%), uneven surface (4%), retinal pigment epithelium (RPE) defects (1%), RPE folding (1%), and macular holes (2%). Multiple linear regression analysis showed that the significant factors associated with postoperative BCVA were ELM disruption and macular holes. Foveal photoreceptor layer integrity as determined by OCT imaging after a successful macula-off RD repair was used to classify each eye included in the study into one of three subgroups: intact IS/OSjunction and ELM (11), disrupted IS/OS junction but intact ELM (11), and disruption of the IS/OS junction and ELM (37). Mean postoperative BCVA (0.18 ± 0.13 logMAR units, 0.43 ± 0.26 logMAR units, and 0.69 ± 0.42 logMAR units, respectively) was significantly different among these subgroups (p < 0.001). Conclusion: OCT is a useful, noninvasive tool for evaluating foveal microstructural abnormalities and predicting visual outcomes after a successful RRD repair.



How to cite this article:
Lin HC, Yeh PT, Huang JS. Optical coherence tomography study of foveal microstructure after successful retinal detachment surgery.Taiwan J Ophthalmol 2013;3:103-107


How to cite this URL:
Lin HC, Yeh PT, Huang JS. Optical coherence tomography study of foveal microstructure after successful retinal detachment surgery. Taiwan J Ophthalmol [serial online] 2013 [cited 2022 Jun 28 ];3:103-107
Available from: https://www.e-tjo.org/text.asp?2013/3/3/103/203874


Full Text

 1. Introduction



Visual complaints such as poor visual recovery or meta-morphopsia may be encountered postoperatively in patients with macula-off rhegmatogenous retinal detachments (RRDs), even after a successful retinal reattachment.[1] Damage to the macular structures during retinal detachment (RD) may result in incomplete visual recovery. Several in vivo and histological studies have reported that RDs induce photoreceptor apoptosis.[2,[3],[4],[5] Subtle changes in foveal structures, which impede visual recovery, can be difficult to find during clinical examinations performed using slit-lamp biomicroscopy or indirect ophthalmoscopy.

Optical coherence tomography (OCT) has been used for the noninvasive evaluation of morphologic macular changes after successfully treating an RRD. The presence of persistent residual subretinal fluid (SRF) may be related to delayed and/or incomplete visual recovery after a successful reattachment of the retina.[6],[7] The presence of cystoid macular edema (CME) or an epiretinal membrane (ERM) can also affect the visual outcome after retinal reat-tachment.[8],[9] Ultra high-resolution OCT[9] has previously revealed distortion of the photoreceptor inner/outer segment (IS/OS) junction in patients with decreased visual acuity after RD repair. In another study using Fourier-domain OCT (FD-OCT) to assess postoperative foveal microstructure, the authors found that postoperative best-corrected visual acuity (BCVA) was significantly correlated with the integrity of the IS/OS and external limiting membrane (ELM) signals detected by FD-OCT.[10]

In this study, structural changes in the macula after anatomically successful RRD repairs were evaluated using Cirrus OCT (Carl Zeiss Meditec, Dublin, CA, USA). The OCT images were then used to investigate the relationship among the type of surgery performed, structural changes in the fovea, and postoperative levels of BCVA.

 2. Materials and methods



This retrospective consecutive case series included patients who had been diagnosed with a fresh RRD during the period from January 2009 to June 2010. A single retina specialist (J.-S.H.) in the Ophthalmology Department, National Taiwan University Hospital (Taipei, Taiwan) performed all of the surgeries. Each patient underwent complete preoperative and postoperative clinical ophthalmic examinations, including the assessment of BCVA using a Snellen chart, a slit-lamp examination, and a dilated fundus examination, which was performed by experienced retina specialists (H.-C.L., P.-T.Y., and J.-S.H.). Data related to the patient’s preoperative medical and ophthalmic history, preoperative BCVA, the duration of symptoms, the number of breaks, the extent of the RD, macular detachment, lens status, and the type of surgery performed were collected and recorded in detail. The main outcome measurements for data analysis were postoperative BCVA and OCT images of foveal microstructures. All examinations and investigations adhered to the tenets of the Declaration of Helsinki. The Institutional Review Board Committee of National Taiwan University Hospital approved the study.

Microstructural imaging of the fovea was performed using a Cirrus OCT (Carl Zeiss Meditec), an FD platform that uses an 840-nm superluminescent diode as the optical source. The diode has a spectral bandwidth of 50 nm, axial resolution of 5 μm, and a scan velocity of 27,000 axial scans per second. Scans were obtained at horizontal cross sections through the fovea; the scan showed three distinct lines, indicating reflection from the ELM, IS/OS junction, and retinal pigment epithelium (RPE)/Bruch’s membrane, respectively [Figure 1]. Microstructural changes in the photoreceptor layer were defined as disruption or loss of the photoreceptor IS/OS junction, the ELM, or both. CME was defined as increased macular thickness (>300 μm) with intraretinal cystic spaces. The presence of thin, highly reflective bands anterior to the neurosensory retina with focal or global adherence to the retinal surface was considered as an indication of an ERM. Each of the OCT images was interpreted by two investigators (H.-C.L. and P.-T.Y.). If there was any disagreement, a third investigator (J.-S.H.) was consulted.{Figure 1}

2.1. Statistical analyses

Visual acuity values were converted into the logarithm of the minimal angle of resolution (logMAR) for statistical analysis. Statistical analyses were conducted using SPSS version 17.0 (SPSS Inc., Chicago, IL, USA). An independent sample t test was used to compare the macula-on and macula-off groups. Multiple linear regression analysis was used to identify the significant factors associated with postoperative BCVA. Postoperative structural changes were evaluated by analysis of variance. A p value <0.05 indicated statistical significance.

 3. Results



Eighty-three eyes of 80 patients (48 men and 32 women), who had undergone an anatomically successful repair for RRD, were included in this study. The basic characteristics of these 83 eyes are summarized in [Table 1]. The mean age of the patients was 48.12 ± 13.83 years (range: 17-74 years). Twenty-four eyes (29%) had macula-on RD and 59 (71%) had macula-off RD. Twenty-two eyes (26%) were treated with a pars plana vitrectomy and 61 (74%) with segmental scleral buckles.{Table 1}

The time interval between surgery and postoperative OCT examination was approximately 24 months (range: 18-30 months). The mean postoperative BCVA at the time of the OCT examination was 0.44 ± 0.39 logMAR units. Disruptions in the IS/OS junction were found in 49 eyes (59%), 38 of which also exhibited ELM disruption. In addition, ERM, CME, and SRF were observed in 18 (22%), six (7%), and six eyes (7%), respectively. Three eyes (4%) had uneven retinal surfaces, one eye (1%) had an RPE defect, and one eye (1%) exhibited RPE folds. Two eyes (2%) had macular holes. Sixty eyes (72%) had at least one abnormality that was detectable by OCT.

The mean BCVA of the six eyes with CME was 0.70 ± 0.37 log-MAR units, which was not significantly different from the mean BCVA among eyes without CME (mean BCVA: 0.42 ± 0.39 logMAR units; p = 0.087). The mean BCVA of the 18 eyes with ERMs was 0.58 ± 0.42 logMAR units, which was similar to the mean BCVA among eyes without ERMs (mean BCVA: 0.40 ± 0.38 logMAR units; p = 0.120).

The comparison between the macula-on and macula-off groups is presented in [Table 2]. Both preoperative and postoperative visual acuity were superior in the macula-on group than in the macula-off group (preoperative BCVA: 0.28 ± 0.26 logMAR units vs. 1.55 ± 0.61 logMAR units; p < 0.001 ; postoperative BCVA: 0.21 ± 0.22 logMAR units vs. 0.56 ± 0.41 logMAR units; p < 0.001). The incidence of OCT abnormalities was 29% in the macula-on group and 89% in the macula-off group (p < 0.001). Disruptions of the IS/OS junction with or without disrupted ELM, an uneven retinal surface, RPE defects, RPE folds, and macular holes were observed only in the macula-off group. The incidences of ERMs, CME, and SRF were similar in both groups.{Table 2}

In the macula-on group (n = 24), the only abnormalities detected by OCT were ERMs (n = 4), CME (n = 2), and SRF (n = 2).

Postoperative BCVA did not differ between eyes with OCT abnormalities and eyes without OCT abnormalities (p = 0.491). Eyes in the macula-off group (n = 59) exhibited several abnormalities detected by OCT, including IS/OS disruption, ELM disruption, an uneven retinal surface, RPE defects, RPE folds, ERMs, CME, SRF, and macular holes.

Multiple linear regression analysis was performed to identify the significant risk factors for poor postoperative visual acuity. The results showed that the most important factors associated with postoperative BCVA were ELM disruption (p = 0.033) and the presence of a macular hole (p = 0.039; [Table 3]).{Table 3}

To investigate the relationship between macular detachment and microstructural changes, OCT images of the foveal photore-ceptor layer after the anatomically successful repair of a macula-off RD were divided into three subgroups: intact IS/OS junction and ELM (n = 11), disrupted IS/OSjunction and intact ELM (n = 11), and disrupted IS/OS junction and ELM (n = 37; [Figure 2]. Baseline characteristics such as age, the duration of symptoms, preoperative BCVA, extent of the RD, number of breaks, and the type of surgery were similar among all the three subgroups [Table 4]. There was a significant difference in postoperative BCVA among these subgroups (postoperative BCVA: 0.18 ± 0.13 logMAR units, 0.43 ± 0.26 logMAR units, and 0.69 ± 0.42 logMAR units, respectively; p < 0.001). A post hoc test revealed significant differences between the intact IS/OS junction and ELM group and the disrupted IS/OS junction and ELM group (p < 0.001) as well as the disrupted IS/OS junction and intact ELM group and the disrupted IS/OS junction and ELM group (p = 0.021), but there was no statistical significance between the intact IS/OS junction and ELM group and the disrupted IS/OS junction and intact ELM group (p = 0.148; [Figure 3].{Table 4}{Figure 2}{Figure 3}

 4. Discussion



ERMs were observed in 18 eyes (22%) in which surgical repair of the RD had been anatomically successful. Postoperative ERM formation may distort the patient’s vision and result in decreased visual acuity.[11],[12] However, in our study, the mean BCVA of the 18 eyes with ERMs was similar to the mean BCVA of eyes without ERMs. It is possible that some of the ERMs did not exert traction on the macula or induce macular edema, both of which are typical causes of postoperative reductions in visual acuity.

Postoperative visual impairment may also be due to CME. The incidence of CME after RD surgery was approximately 4–17%.[11],[12] Previous studies have indicated that pseudophakia, aphakia, older age, cryotherapy, and the external drainage of SRF were associated with a higher incidence of CME development.[13],[14],[15] Six of the eyes (7%) included in this study developed CME postoperatively. Among these six eyes, five were phakic and four underwent scleral buckle surgery combined with cryopexy and external drainage. The mean age of the CME patients was 54.21 ± 4.88 years, which was similar to the mean age of the patients without CME (p = 0.330). Our results showed that CME may be more common among patients treated by cryopexy in combination with external drainage (p = 0.002). The mean postoperative BCVA in eyes with CME (0.70 ± 0.37 logMAR units) was decreased compared with the levels observed in eyes without CME (0.42 ± 0.39 logMAR units), but this difference was not significant (p = 0.087). Thus, CME appears as one of the many factors that affect postoperative visual acuity. The presence of persistent SRF may delay visual recovery after RD surgery.[16]

The other factors associated with postoperative BCVA in our study were ELM disruption and the presence of a macular hole. The incidence of macular-hole formation after RRD surgery was low (approximately 1%).[17] Two eyes (2%) included in our study developed macular holes and both had poor postoperative visual acuity. Nonetheless, the rarity of this finding suggests that macular holes may not represent the most common cause of poor visual recovery after RRD surgery.

Among the eyes in the three subgroups distinguished on the basis of OCT images, those without disruptions to either the IS/OS junction or the ELM had the best visual outcomes. The eyes with disruptions to both the IS/OS junction and ELM had the worst vision. These data are consistent with findings published previ-ously.[10] Although the eyes with macula-off RD had poorer postoperative BCVA, some of them still had favorable outcomes. Despite the poor preoperative BCVA (1.40 ± 0.54 logMAR units) observed among the 11 macula-off eyes with intact IS/OSjunctions and ELM, postoperative BCVA in this group (0.18 ± 0.13 logMAR units) was similar to that of the 24 eyes in the macula-on group (0.21 ± 0.22 logMAR units). Changes to the microstructure of the retina are therefore the most reliable predictors of postoperative visual outcome.

After RD, the OSs of the photoreceptors degenerate and many of these cells subsequently undergo apoptosis. The reversibility of the resulting drop in BCVA was determined by the duration of the interval for which the retina had been detached.[2],[18],[19],[20] Notably, photoreceptor apoptosis and degeneration are difficult to quantify in vivo. Wakabayashi et al[10] proposed that disruptions to both the IS/OS junction and ELM indicate that the morphologic changes in the photoreceptor layer extend from the level of the IS/OS junction to that of the cell bodies; whereas disruption to the IS/OS junction in association with an intact ELM may indicate that the morphological changes are limited to the level of the IS/OSjunction without extension to the cell bodies. Wakabayashi et al[10] also found that 64% of eyes with disruptions at the level of the IS/OS junction and intact ELMs ultimately achieved complete restoration of the IS/OS junction. By contrast, the IS/OS junction remained disrupted in eyes with ELM damage even after an anatomically successful reattach-ment surgery. Therefore, the extent of microstructural changes may account for the differences in BCVA among the three subgroups investigated here. Furthermore, results of multiple linear regression analysis suggested that the ELM plays a more important role than the IS/OS junction in determining postoperative BCVA.

This study had several limitations. First, it was a retrospective study. Second, OCT images were obtained only once. The lack of serial follow-up images prevented us from following the evolution of microstructural changes in the fovea. In addition, the lack of preoperative OCT images meant that we could not tell whether the microstructural changes had existed prior to the surgery.

In summary, OCT is a useful, noninvasive tool for evaluating anatomic abnormalities in the fovea. ELM disruption and macular-hole formation predict poor visual outcomes in eyes after the anatomically successful repair of RRDs.

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