Response #2 to Immediate Intraocular Pressure Tendency Following Intravitreal Delivery of Dexamethasone Implant;Alagöz et al. J. Ocul. Pharmacol. Ther. 32:44–49,2016

To the Editor,

We read with interest the article by Alagöz et al. ¹ regarding immediate intraocular pressure (IOP) changes following dexamethasone intravitreal implant (DII) in eyes with macular edema secondary to diabetic retinopathy (DR) or retinal vein occlusion (RVO). The authors measured the IOP at baseline, 1 min, 10 min, 1 h, and at 1 day. None of the eyes showed hypotony (defined as IOP <6 mmHg) at 1 h or 1 day, although visible reflux after needle removal was reported in 26% of the patients. This result does not match with our study ² mentioned in the article. This study, which included 27 eyes with macular edema secondary to branch RVO (37.03%), central RVO (29.62%), inflammation (22.22%), and DR (11.11%), not only reported a higher hypotony rate but also described 2 self-limited choroidal detachments (CDs). ³ These CDs were caused by continued leaking through the nonplanned oblique sclerotomy, as demonstrated by anterior segment spectral domain optical coherence tomography (AS-OCT).

Encouraged by these results and looking for better resolution images, we designed a prospective observational study including 18 eyes of 18 consecutive patients with macular edema that underwent DII injection between February and April 2013. All research and data collection followed the tenets of the Helsinki Agreement. Incisions were prospectively analyzed with Swept source AS-OCT (Casia OCT SS-1000; Tomey Corporation, Nagoya, Japan) to assess scleral wound architecture at 1 and 5 h, and at 1, 3, 7, 10, and 14 days postoperatively. Three IOP measurements per visit were obtained with a noncontact automatic tonometer (Canon TX-F; Canon Europe NV, Amstelveen, The Netherlands, Europe) and the mean of the 3 was registered.

The mean time of the sclerotomy closure was 7.06 days (range 3–14) and mean incision length was 0.928 mm (range 0.668–1.263 mm). Of the 18 eyes, 16 eyes (88.88%) had ciliochoroidal detachment and 4 (22.22%) had vitreous incarceration.

The mean preoperative IOP was 15.2 mmHg and the mean postoperative IOP was 12.2, 14.8, 13.7, 14.1, 19.3, 17.4, and 18.6 mmHg at 1 and 5 h, and at 1, 3, 7, 10, and 14 days postoperatively. One patient (5.55%) had transient hypotony with a local CD and the AS-OCT image also showed ciliochoroidal detachment with vitreous incarceration (Fig. 1). The CD resolved spontaneously by day 8. The mean postoperative pressure was significantly lower than the preoperative IOP at 1 h (P = 0.0259).

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FIG. 1.

Local choroidal detachment: (A) behind the scleral buckle (arrow) and (B) an echographic image (arrow). Swept source anterior segment optic coherence topographies: (C) Ciliochoroidal detachment (arrow), choroidal detachment (star), and vitreous incarceration (short arrow), and (D) oblique sclerotomy. Color images available online at www.liebertpub.com/jop

Therefore, there are differences in rates of clinically significant hypotony. An explanation was recently provided by Meyer et al. ⁴ These authors demonstrated that the new needle of the Ozurdex device reduces the amount of force required to penetrate the sclera, which leads to good wound architecture. Our 2 studies were performed using the old needle, and we think that our hypotony rates are due to the destructured scleral tunnel generated by the higher force required to introduce the old needle through the sclera. Further head-to-head studies are necessary to compare the wound architecture created by the 2 needles.