Graefe's Archive for Clinical and Experimental Ophthalmology

, Volume 252, Issue 8, pp 1207–1212

Stereopsis after successful surgery for rhegmatogenous retinal detachment

Authors

    • Department of Ophthalmology, Faculty of MedicineUniversity of Tsukuba
  • Fumiki Okamoto
    • Department of Ophthalmology, Faculty of MedicineUniversity of Tsukuba
  • Yoshimi Sugiura
    • Department of Ophthalmology, Faculty of MedicineUniversity of Tsukuba
  • Sujin Hoshi
    • Department of Ophthalmology, Faculty of MedicineUniversity of Tsukuba
  • Yoshifumi Okamoto
    • Department of Ophthalmology, Faculty of MedicineUniversity of Tsukuba
  • Takahiro Hiraoka
    • Department of Ophthalmology, Faculty of MedicineUniversity of Tsukuba
  • Tetsuro Oshika
    • Department of Ophthalmology, Faculty of MedicineUniversity of Tsukuba
Retinal Disorders

DOI: 10.1007/s00417-014-2566-x

Cite this article as:
Watanabe, H., Okamoto, F., Sugiura, Y. et al. Graefes Arch Clin Exp Ophthalmol (2014) 252: 1207. doi:10.1007/s00417-014-2566-x

Abstract

Background

To evaluate stereopsis after successful surgery for unilateral rhegmatogenous retinal detachment (RD), and to investigate the relationship between stereopsis and clinical factors.

Methods

In 75 patients after RD surgery and 28 age-matched normal subjects, stereopsis was measured using the Titmus Stereo Test (TST) and TNO stereotest. Clinical data were collected, including age, gender, circumferential dimension of retinal tears, area and duration of RD, macular status, surgical procedures, postoperative spherical equivalent, and logarithm of the minimum angle of resolution best-corrected visual acuity (logMAR BCVA), low-contrast visual acuity, postoperative lens status (phakia/pseudophakia), and presence of postoperative epiretinal membrane (ERM), to determine the factors related to stereopsis.

Results

Stereopsis in patients after surgery was significantly worse than normal subjects (p < 0.0001). Stereopsis in TST was significantly correlated with the area of RD (p < 0.005), difference of postoperative spherical equivalent between two eyes (p < 0.05), postoperative logMAR BCVA (p < 0.005), difference of postoperative logMAR BCVA between two eyes (p < 0.01), and low-contrast visual acuity (p < 0.05). Stereopsis in TNO stereotest showed significant association with postoperative logMAR BCVA (p < 0.05). Stereopsis in both stereotests were significantly worse in patients with macula-off RD than macula-on RD (p < 0.005, p < 0.01 respectively). No significant relationship was found between stereopsis and other factors. Multiple regression analysis revealed that macular status (on/off) had a significant correlation with both stereopsis in TST and TNO stereotest (p = 0.028, p = 0.019 respectively), whereas other clinical parameters were not relevant.

Conclusions

Stereopsis is significantly deteriorated in patients after RD surgery than in normal subjects. Stereopsis was associated with the difference in refraction between two eyes, postoperative visual acuity and contrast sensitivity, and preoperative macular status.

Keywords

StereopsisVitrectomyRhegmatogenous retinal detachment

Introduction

Stereopsis is the ability to perceive the depth of field based on the disparity of the images formed by two eyes. In 1838, Wheatstone invented the stereoscope and discovered that if the areas on the retina of both eyes separated horizontally were stimulated simultaneously, stereopsis could occur [1]. With improved anatomical success rates of surgery for rhegmatogenous retinal detachment (RD), increasing attention has been directed toward the quality of postoperative vision. The effectiveness of RD surgery has generally been assessed by the rates of retinal reattachment and the postoperative visual acuity [210]. The influence of RD surgery on stereopsis has not been well-studied. Amemiya et al. evaluated binocular visual function after surgery for RD, and identified that worse stereopsis was associated with older age and worse visual acuity [11]. There is, however, no report evaluating the relationship between stereopsis and other visual functions except for visual acuity, or characteristics of RD.

The purpose of this study is to evaluate stereopsis after successful surgery for unilateral RD, and to investigate the relationship between stereopsis and other visual functions as well as clinical factors.

Subjects and methods

We analyzed 75 patients (43 men, 32 women) after successful surgery for unilateral RD undertaken at University of Tsukuba Hospital from October 2008 to April 2010, and 28 age-matched normal subjects (13 men, 15 women). Their ages averaged 53.9 ± 10.7 years (means ± SD) and 51.8 ± 14.8 years respectively. Exclusion criteria were age under 18 years, previously diagnosed anterior segment disease, glaucoma, moderate and severe cataract, strabismus, any systemic disease that influenced ocular motility, and vitreoretinal disorders except RD. Patients with history of low vision or reduced stereopsis were also excluded.

Between 6 and 12 months after surgery, all patients underwent an examination including visual acuity, cover test, and ocular motility. A 4-diopter prism test was performed to detect the presence of a central suppression scotoma or small manifest deviation, and to prove bifoveal fixation. All patients had good corrected visual acuity in the fellow eye, no shift of either eye on cover test at distance and near, and normal or atypical one response to 4-diopter prism test. Stereopsis was measured with the Titmus Stereo Test (TST) and TNO stereotest at the standard viewing distance of 40 cm with appropriate spectacle correction. To ensure that patients were not using monocular clues in TST, responses were checked by inverting the stereotarget and asking the patient if the target appeared in front of or behind the page. The research followed the tenets of the Helsinki Accord. The subjects gave informed consent after our explanation of the nature and possible consequences of the study. The study was approved by the hospital’s ethics committee.

Clinical data were collected, including age, gender, circumferential dimension of retinal tears, area of RD, duration of RD, macular status (on or off), surgical procedures (scleral buckling or vitrectomy), postoperative spherical equivalent, postoperative logarithm of the minimum angle of resolution best-corrected visual acuity (logMAR BCVA), difference of postoperative logMAR BCVA between the two eyes, postoperative low-contrast visual acuity, postoperative lens status (phakia or pseudophakia), and presence of postoperative ERM (with or without), to determine factors related to stereopsis.

Surgery was performed at our clinic by an experienced vitreoretinal surgeon (F.O.). Twenty-eight patients were treated with primary scleral buckling, and the other 47 with primary vitrectomy. The buckling surgery consisted of cryopexy and circumferential silicone sponge buckling (no. 506; MIRA, Waltham, Massachusetts, USA). The encircling was performed with a silicone band (no. 240; MIRA) or a silicone sponge (no. 506G; MIRA). Subretinal fluid drainage and air injection were performed when required. A standard three-port pars plana vitrectomy was carried out, and the surgical technique comprised a vitrectomy that released vitreous traction around the breaks, internal drainage of the subretinal fluid, a total fluid/gas exchange with 20 % sulfur hexafluoride (SF6) to effect internal tamponade, and endolaser photocoagulation. None of the vitrectomy group had any additional external buckling elements. In both groups, patients who were injected with gas were instructed to maintain a face-down position during the first postoperative week.

The mean score and standard deviation were calculated for each clinical characteristic, surgical procedure, and postoperative visual function in patients undergoing surgery for RD. The results of stereotests were expressed as ‘seconds of arc’ and used for the assessment. The relationship between stereopsis and age, circumferential dimension of retinal tears, area of RD, duration of RD, difference of postoperative spherical equivalent between the two eyes, postoperative logMAR BCVA, difference of postoperative logMAR BCVA between the two eyes, and postoperative low-contrast visual acuity, were examined with the Spearman rank correlation test. A Mann–Whitney’s U test was performed to compare stereopsis between the RD and normal subject groups. The same test was also used to compare stereopsis related to surgical procedures (scleral buckling/vitrectomy), macular status (on/off), postoperative lens status (phakia/pseudophakia) and postoperative ERM (with/without). All tests were considered statistically significant at p < 0.05. The analyses were carried out using Statview (SAS Institute Inc., Cary, NC, USA).

Results

All patients had unilateral RD and surgery only in the affected eye during the perioperative and 12-month postoperative period. Retinal reattachment was attained at primary operation in all eyes. Among the 75 RD patients, 28 underwent scleral buckling surgery and 47 underwent vitrectomy, of which 31 eyes received combined cataract surgery and vitrectomy. During the follow-up period, three cases of phakic patients eventually proceeded to cataract surgery due to a development or progression of cataract observed by slit-lamp examination and postoperative ERM observed by funduscopic examination or optical coherence tomography images occurred in 11 cases. No significant intraoperative and postoperative complications were observed, such as subretinal hemorrhage, persistent elevation of intraocular pressure for more than 3 days, cystoid macular edema, and choroidal detachment. In the scleral buckling group, air was injected in five patients (18 %), and subretinal fluid drainage was performed in 17 patients (60 %). In the vitrectomy group, 20 % SF6 gas was injected in all 47 patients.

Table 1 shows clinical characteristics, surgical procedure, and postoperative visual functions in patients undergoing surgery for RD. Duration of RD was 11.1 ± 8.4 days, with 31 of 75 eyes being macular-off RD. Postoperative logMAR BCVA was 0.05 ± 0.15, the difference of postoperative logMAR BCVA between the two eyes was 0.12 ± 0.13, and postoperative low contrast visual acuity was 0.37 ± 0.22.
Table 1

Clinical characteristics, surgical procedures, and postoperative visual functions in patients undergoing surgery for RDa

Factors

 

Preoperative logMAR BCVAb

0.52 ± 0.72

Preoperative spherical equivalent of affected eye

−4.1 ± 4.1

Preoperative spherical equivalent of fellow eye

−3.1 ± 3.5

Circumferential dimension of retinal tears (degrees)

18.6 ± 15.0

Area of RD (degrees)

123 ± 70

Duration of RD (days)

11.1 ± 8.4

Macular status (on/off)

44/31

Surgical procedures (scleral buckling/vitrectomy)

28/47

Difference of postoperative spherical equivalent between both eyes (diopter)

0.94 ± 0.87

Postoperative logMAR BCVA

0.05 ± 0.15

Difference of postoperative logMAR BCVA between both eyes

0.12 ± 0.13

Postoperative low contrast visual acuity

0.37 ± 0.22

Postoperative lens status (phakia/pseudophakia)

40/35

Postoperative ERMc (with/without)

11/64

Values are presented as the mean±standard deviation

aRetinal detachment

bLogarithm of the minimum angle of resolution best-corrected visual acuity

cEpiretinal membrane

The results of stereopsis in the RD group and normal subjects are shown in Table 2. Stereopsis in patients after RD surgery was significantly worse than that of normal subjects (TST: p < 0.0001, TNO stereotest: p < 0.0001).
Table 2

Stereopsis in patients undergoing surgery for RD and normal subjects

 

Patients with RD

Normal subjects

P value

Number of cases

75

28

 

Age (years)

53.9 ± 10.7

51.8 ± 14.8

0.43

Gender (man : woman)

43 : 32

13 : 15

0.32

TSTa (seconds of arc)

269 ± 494

52 ± 22

<0.0001*

TNO stereotest (seconds of arc)

870 ± 844

67 ± 45

<0.0001*

Values are presented as the mean±standard deviation

aTitmus Stereo Test

*Significantly different between the groups (Mann–Whitney’s U test)

As shown in Table 3, stereopsis in TST was significantly associated with area of RD, difference of postoperative spherical equivalent between the two eyes, postoperative logMAR BCVA, difference of postoperative logMAR BCVA between the two eyes, low-contrast visual acuity, and macular status, but not with age, circumferential dimension of retinal tears, duration of RD, and surgical procedures. Multiple regression analysis revealed that stereopsis in TST had a significant correlation with macular status (P = 0.028), whereas other variables (area of RD, difference of postoperative spherical equivalent between the two eyes, postoperative logMAR BCVA, difference of postoperative logMAR BCVA between the two eyes, low-contrast visual acuity) were not relevant.
Table 3

Clinical Factors Associated with Stereopsis Measured by TST after Successful Surgery for RD

Factors

Correlation coefficient (r)

P value

Age

0.03

0.78

Circumferential dimension of retinal tears

0.03

0.83

Area of RD

0.36

0.003

Duration of RD

0.08

0.54

Difference of postoperative spherical equivalent between both eyes

0.27

0.03

Postoperative logMAR BCVA

0.36

0.003

Difference of postoperative logMAR BCVA between both eyes

0.32

0.007

Postoperative low contrast visual acuity

0.26

0.04

Factors

TST (seconds of arc)

P value

Macular status

(on)

215 ± 490

0.001*

(off)

362 ± 541

Surgical procedures

(scleral buckling)

181 ± 174

0.36

(vitrectomy)

330 ± 627

Postoperative lens status

(phakia)

167 ± 156

0.10

(pseudophakia)

436 ± 760

Postoperative ERM

(with)

435 ± 860

0.42

(without)

244 ± 414

Values are presented as the mean±standard deviation.

† A significant correlation (Spearman rank correlation coefficient)

* Significantly different between the groups (Mann-Whitney’s U test)

Stereopsis in TNO stereotest showed significant association with postoperative logMAR BCVA and macular status, whereas other factors were not relevant (Table 4). Multiple regression analysis revealed that stereopsis in TNO stereotest had a significant correlation with macular status (P = 0.019), whereas postoperative logMAR BCVA was not relevant.
Table 4

Clinical Factors Associated with Stereopsis Measured by TNO Stereotest after Successful Surgery for RD

Factors

Correlation coefficient (r)

P value

Age

- 0.06

0.62

Circumferential dimension of retinal tears

- 0.12

0.34

Area of RD

0.22

0.08

Duration of RD

0.15

0.27

Difference of postoperative spherical equivalent between both eyes

0.14

0.26

Postoperative logMAR BCVA

0.31

0.01

Difference of postoperative logMAR BCVA between both eyes

0.19

0.12

Postoperative low contrast visual acuity

0.23

0.07

Factors

TNO (seconds of arc)

P value

Macular status

(on)

671 ± 790

0.006*

(off)

1156 ± 847

Surgical procedures

(scleral buckling)

702 ± 801

0.09

(vitrectomy)

969 ± 861

Postoperative lens status

(phakia)

754 ± 797

0.32

(pseudophakia)

1043 ± 896

Postoperative ERM

(with)

1478 ± 860

0.05

(without)

756 ± 797

Values are presented as the mean±standard deviation.

† A significant correlation (Spearman rank correlation coefficient)

* Significantly different between the groups (Mann-Whitney’s U test)

Discussion

Our results indicated that even after successful retinal reattachment, stereopsis has markedly deteriorated compared with that of normal subjects. It is known that stereopsis could also be damaged in patients after successful surgery of unilateral epiretinal membrane or macular hole [1214]. Wright et al. investigated binocularity in patients after successful RD surgery, and observed aniseikonia in 35 % of patients, distortion in 23 %, and diplopia in 18 % [15]. It is thus considered that such disruption of binocularity deteriorated stereopsis in patients after surgery for RD.

Stereopsis in TST was associated with the area of RD in our study. Shiragami et al. clarified that the extent of RD was significantly associated with postoperative displacement of the retina using fundus autofluorescence [16]. They suggested that a large extent of RD could cause retinal translocation even after successful surgery, resulting in dislocation of the macula from its original location. It is known that high-grade stereopsis requires bifoveal fixation and a high level of visual acuity [15]. Thus, displacement of the fovea may cause deterioration of stereopsis. In consideration of the previous reports, our results suggested that large RD could cause translocation of the fovea from its original site after surgery and damage bifoveal fixation, thus deteriorating stereopsis.

Shiragami et al. also reported that the macular status (on or off) was significantly associated with postoperative retinal displacement [16]. This means that macula-off RD patients could exhibit displacement of the retina even after postoperative reattachment, which may disrupt foveal fixation. Stereopsis of macula-off RD patients hence tends to be damaged more severely than macula-on RD patients.

In our study, postoperative logMAR BCVA and difference of postoperative logMAR BCVA between the two eyes were significantly correlated with stereopsis. A relationship between visual acuity and stereopsis was previously observed in normal subjects [1719], in patients after macular hole surgery [12], and in patients after RD surgery [11]. Meanwhile, Lam et al. reported that difference in visual acuity between two eyes was a cause of reduced stereopsis [20]. Burian also reported that as visual acuity got worse in one eye, stereopsis degraded [21]. Their findings are consistent with our results. In addition, our results indicated that stereopsis was associated with contrast sensitivity. Contrast sensitivity is also one of the measures of visual function. Therefore, decreased contrast sensitivity is likely to reduce stereopsis.

A correlation between the difference of postoperative spherical equivalent and stereopsis was observed in our study. In general, a relative difference in the refractive state of the two eyes is regarded as anisometropia [22]. Anisometropia was associated with an increase in aniseikonia [23], with both visual functions recognized as a factor in the disruption of fusion [24]. Thus, it is considered that a greater difference in spherical equivalent between the two eyes could lead to more severe deterioration of stereopsis.

In our study, stereopsis was significantly associated with postoperative visual acuity and macular status (in both TST and TNO stereotest).However, the area of RD, difference of spherical equivalent between the two eyes, difference of postoperative logMAR BCVA between the two eyes, and postoperative low-contrast visual acuity were associated only with the measurement values of stereopsis in TST, but not with the levels of stereopsis in the TNO stereotest. The difference may arise from the different index size in both tests. The stimulus used for fine stereopsis in the TNO stereotest is much larger than the Titmus circles. At the standard examination distance, the TST circles subtend a visual angle of only 0.7°, in comparison with 8.5° in the TNO stereotest. The fovea measures 1500 μm in diameter and the foveola 350 μm, with visual angles of approximately 5° and 1.2°, respectively. Hence, TST circles are closer to the size of index of good visual acuity and contrast sensitivity. This may explain the finding that TST results exhibited a correlation with more visual function factors than TNO.

Our study has several limitations. First, we did not evaluate stereopsis of the patients before they suffered from RD because of the characteristic of this disease. If stereopsis was already impaired before RD, the state might have affected the postoperative outcome of stereopsis. Second, other factors are known to affect stereopsis, such as eye dominance [25, 26], pupil size [27, 28], and accommodation [19, 29]. But we did not take these factors into consideration in this study. Third, the postoperative follow-up was short. We evaluated the patients at 6 to 12 months postoperatively. It has been reported that visual acuity in patients with RD improved more at 5 years postoperatively than at 6 months postoperatively [30]. Future studies with a longer follow-up period will further facilitate our understanding of the relationship between stereopsis and visual functions in patients undergoing surgery for RD.

In conclusion, the results of this study demonstrated that stereopsis in patients after successful retinal reattachment surgery was significantly deteriorated compared to that in normal subjects. Stereopsis after RD surgery was associated with the area of RD, visual acuity, contrast sensitivity, difference in refraction between both eyes, and macular status. Hence, we should have much interest not only in morphological improvement and visual acuity but also in stereopsis.

Conflict of interest

The authors declare that they have no conflict of interest.

The authors have no individual or family investments, stock or business ownership exceeding 1 % of a company’s worth, consulting, retainers, patents, or other commercial interests in the product or company described in the current article. There is no involvement in the marketing of any product, drug, instrument, or piece of equipment discussed in the manuscript that could cause or be perceived to be a conflict of interest.

Copyright information

© Springer-Verlag Berlin Heidelberg 2014