Subjects.
This study was approved by the Ethical Committee of Osaka City University Graduate School of Medicine (No. 2009 and 2421), carried out on the basis of the Declaration of Helsinki, and SRT was registered with University hospital Medical Information Network (UMIN) (No. 000005396 and 000010471). Written informed consent was obtained from all patients prior to enrolment. This study investigated 77 eyes in 77 CSC patients (61 eyes of 61 males and 16 eyes of 16 females), who underwent SRT in the Department of Ophthalmology at Osaka City University Hospital between June 2011 and December 2016 and were followed-up for at least 6 months. The mean age of patients was 51 years (range, 29–78 years). Table 1 shows baseline characteristics of the patients in this study.
SRT Inclusion and Exclusion Criteria.
Inclusion criteria for selection of patient treated with SRT were as follows:
1) minimum age of 20 years,
2) subjective symptoms of central scotoma, metamorphopsia, or decline of visual acuity,
3) history of more than 3 months with no sign of improvement of CSC diagnosed with optical coherence tomography (OCT),
4) presence of SRF on OCT, and
5) presence of active leakage in fluorescein angiography (FA).
Ophthalmologic exclusion criteria were as follows:
1) macular diseases with SRF caused by the disease other than CSC,
2) history of other laser treatments for CSC, such as conventional laser, PDT or SMPL.
3) absence of leakage in FA
Systematic exclusion criteria were as follows:
1) inflammatory disease,
2) bleeding tendency and anticoagulation therapy,
3) presence or possibility of pregnancy,
4) untreated hypertension and diabetes mellitus,
5) taking of diuretic, such as acetazolamide or spironolactone.
Clinical Observations.
All patients underwent the following ophthalmic observations at baseline and at 3 and 6 months after the treatment: the best corrected visual acuity (BCVA) measurement, slit-lamp microscopy, funduscopy, OCT (SPECTRALIS®; Heidelberg Engineering GmbH, Heidelberg, Germany), color fundus photography, fundus autofluorescence, and FA (SPECTRALIS®). For the BCVA analysis, decimal visual acuities were converted to logarithmic minimum angle of resolution (logMAR) values.
SRT Method
The SRT system utilizes a Q-switched frequency-doubled neodymium-doped yttrium lithium fluoride (Nd:YLF) laser, frequency doubled to a wavelength of 527 nm (Medical Laser Center Lübeck, Lübeck, Germany). In a single irradiation, a short 1.7 µs laser pulse is repeated 30 times at a repetition rate of 100Hz. The laser beam was adjusted such that the irradiation diameter on the retina was approximately 200 µm with a top hat beam profile under the use of a 1.05× magnification Mainster central field contact lens.
All SRT laser irradiations have been conducted by one ophthalmologist only. The treatment procedure of SRT is principally based on the previous study by Roider et al [20], and briefly as follows; test irradiations were conducted outside of the pathological central region, mostly near the vascular arcade. Beginning with the lowest energy (about 50–60 μJ), the irradiation energy was increased stepwise (every 10 to 20 μJ). In total, about 4–10 different energies were used for two test lesions to examine optoacoustic (OA) value (indicator of microbubble formation: detail described in previous reports [18, 21]. The OA value is a number which is calculated from the ultrasonic waves generated during microbubble formation leading to cell disintegration. The pressure waves are recorded by an ultrasonic transducer embedded in the contact lens [24]. According to the study, the OA value indicating 50% probability of RPE cell disruption (Effective Dose (ED) 50) is 70, and the one indicating 90% probability (ED90) is 112 as a result of calculating the leakage as positive on FA in the used system. Followed by the test laser irradiations, FA was conducted, and the treatment energy was determined, basically with FA findings and supplementarily with the OA value. In order to achieve RPE cell disruption with minimally-required energy, the energy, with which weakly positive leakage was detected in FA, was chosen as the initiation energy for the treatment. After deciding the treatment energy, the treatment was performed at and around the leakage point assessed with FA, giving an interval between spots of about one spot diameter.
Outcome Measures
BCVA, OCT, and FA were performed before treatment and 3 and 6 months after SRT. Central macular thickness (CMT), and central choroidal thickness (CCT) were also investigated. With regard to BCVA, changes of ≥0.2 in logMAR unit were considered significant. A change in CMT and CCT ≥15% compared with the pre-treatment baseline was regarded as significant as previously described [21]. SRT was considered effective if CMT decreased significantly compared to baseline, and as ineffective if this was not the case. As factors that might influence the rate of change in CMT and resolution of SRF 6 months after SRT, we evaluated sex, age, previous hypertension, smoking history, duration of symptom (months), number of episodes (first and second or more), history of medicine, leakage type on FA (focal or diffuse), baseline BCVA, baseline CMT and baseline CCT.
Statistical Analysis
Changes in BCVA (logMAR), CMT and CCT from baseline were assessed using a paired t-test with Bonferroni correction. In order to assess the associations between the changes of CMT after SRT treatment and clinical factors among SRT treated patients, we performed a univariable linear regression analyses with the change value of CMT at 6 months as the function of each clinical characteristic. The correlation between resolution of SRF and clinical factors was also assessed by using univariable logistic regression analysis. Factors showing p values <0.2 in univariate analyses were used for a multivariate analysis. IBM® SPSS® Statistics 24.0 (IBM Japan, Ltd., Tokyo, Japan) was used for statistical analysis, in which p values <0.05 were regarded as significant.