2.2.7. Eyemate® (Implandata Ophthalmic Products GmbH; Hannover, Germany)

This is a CE-certified IOP sensor placed into the ciliary sulcus during cataract surgery or Boston keratoprosthesis Type 1 (BI-KPro) implantation. Similarly to an intraocular lens, the sensor is foldable and can be injected into the eye through a corneal incision. This 11.2 mm wide silicone implant consists of eight pressure-sensitive capacitors in a single application-specific integrated circuit and a microcoil antenna arranged circumferentially. In order to obtain IOP measurements, a handheld reader device is placed at a short distance in front of the eye. The device emits a high frequency field that powers the sensor, and <2 s is needed for the sensor to measure the IOP and send the data to the reader device. A clinical trial demonstrated the successful implantation of Eyemate® in six patients; pupillary distortion and pigment dispersion were observed and some IOP measurements were significantly different from that of Goldmann applanation [38]. Another clinical trial involved 12 patients who underwent BI-KPro surgery and Eyemate® implantation; IOP measurements were found to correlate with surgical manometry (*r* = 0.87) with a mean difference of 3.9 ± 8.6 mm Hg [39]. The Eyemate® intraocular sensor is the first of its kind and can potentially revolutionize IOP monitoring for post cataract surgery or post BI-KPro surgery patients.

#### 2.2.8. Injectsense (Injectsense, Inc.; Emeryville, CA, USA)

This is an IOP sensor, smaller than a grain of rice, that can be implanted transsclerally via an injection. Similarly to an intravitreal injection, implantation of the sensor can be performed in clinic using an injector that pierces the sclera and pars plana. The device selfanchors in the sclera and acts as a plug to prevent the egress of vitreous humor. The sensor measures the IOP at preset time intervals and stores the data. The patient is instructed to wear a pair of smart glasses once a week in order to recharge the sensor and download the stored IOP data, which are then automatically uploaded to a physician-accessible cloud database. This device is limited to investigational use at this time.

#### 2.2.9. Diaton Transpalpebral Tonometer (DevelopAll Inc.; New York, NY, USA)

This is a digital device that measures IOP through the upper eyelid without contact with the cornea. The patient lies in a recumbent position looking up at a 45-degree angle. A measurer pulls up the upper eyelid so that the lid margin is at the corneal limbus. The tonometer tip is placed perpendicular to the eyelid and parallel to the lid margin. A measurement is conducted when the tonometer tip touches the eyelid. The advantages of this device are measurements that can be performed by anyone after a brief training session, a topical anesthetic is not needed and it causes minimal patient discomfort. When compared with Goldmann applanation, Diaton demonstrated a moderate correlation acceptable for glaucoma screening but not as a substitute for Goldmann applanation in the management of glaucoma patients [40–43].

## 2.2.10. Finger Palpation

A crude method for the patient to estimate IOP is via finger palpation on the eye through the upper eyelid and describe whether the eye feels such as a tomato (low IOP), grape (normal IOP), or apple (high IOP). This is especially useful for patients who had recent glaucoma surgery and may experience extremes in IOP. An abnormally soft or firm eye would usually require a visit to the clinic soon.
