Off the Cuff: Hubble and the FTC: A Game of Chicken or Just Plain Chicken?

The aim of this study was to show the potential applicability of optical coherence tomography angiography (OCTA) for the evaluation of the peripheral fitting of fully scleral contact lenses. A pilot study was proposed fitting three different scleral contact lenses (Irregular Corneal Design [ICD]) with different sagittal heights (4,200mm, 4,800mm and 5,600mm) in a healthy volunteer of 27 years old. Researchers evaluated by means of optical coherence tomography (OCT, DRI Triton) the apical clearance achieved with each of the three lenses fitted. The impact over scleral flow was assessed with the OCTA module of the same device.

The apical clearance was 310µm, 901µm and 1,680µm with the scleral lenses of sagittal heights 4,200µm, 4,800µm and 5,600µm, respectively. With OCTA, researchers evaluated the impact of the lens bearing on the conjunctival vascular flow, observing an area of vascular interruption of 0%, 25% and 75% with the lenses of 4,200µm, 4,800µm, and 5,600µm of sagittal heights, respectively. The vascular interruption was induced in the perilimbar area, suggesting the need for readjusting the limbal clearance zone of the lens.

Researchers wrote that fully scleral contact lens fitting might be optimized with the use of OCTA, allowing the practitioner to perform the fitting with better control of the peripheral bearing of the lens on the conjunctival tissue, and assess the impact on vascular structures. They added that this potential use of OCTA must be investigated further in future studies including large samples of eyes.

Accommodating intraocular lenses (A-IOLs) require capturing the ciliary muscle forces. Prior work has demonstrated strong photo-initiated bonding between strips of capsular bag and poly(2-hydroxyethyl methacrylate); (pHEMA) polymer in an extraocular setting.

Investigators demonstrated that photobonding can be achieved intraocularly. Phacoemulsification was performed in porcine eyes (<24 hours postmortem). A commercial intraocular lens (IOL; pHEMA-MMA material) was inserted in the capsular bag. Surface contact between the lens and capsular bag was ensured by continuous air infusion into the anterior chamber of the eye, which provided sufficient pressure at the interface, as well as oxygen. The capsular bag and IOL then were stained with a 0.1% photosensitizer Rose Bengal (RB) solution.

A fiberoptic probe connected to a diode-laser (532 nm) was used to locally irradiate the capsular bag-IOL interface intraocularly. The bonding breaking load was evaluated in a uniaxial stretcher. Photobonding occurred in the 0.8W/cm2 to 1.6W/cm2 irradiance range and 2.5 minutes to 7 minutes irradiation time. Average forces of 0.12N stretched but did not break the bond. These forces, applied uniaxially, were higher than the summed net accommodating force of the ciliary muscle along the entire equator (0.08N). In two cases, the zonulae broke before the bonded region.

Investigators found that photobonding between the capsular bag and IOL polymer could be achieved intraocularly, in a procedure compatible with standard cataract surgery. This technique could enable the mechanisms of A-IOLs not to rely on capsular bag integrity or natural haptic fibrosis. They added that intraocular photobonding held promise to enable operation of A-IOLs to restore accommodation in presbyopia, affecting 100% of the population >45 years old. Furthermore, they wrote, intraocular bonding of polymer material to ocular tissue also might find other applications in ophthalmology.

In a double-blind, randomized, crossover trial, 30 non-presbyopic myopes wore MiSight, center-distance Proclear Multifocal (+2.00D add), and two prototype lenses for one week each to compare the visual performance of soft contact lenses reported to reduce myopia progression. High- and low-contrast visual acuities at 6m, and 70cm and 40cm; stereopsis at 40cm; accommodative facility at 33cm; and horizontal phoria at 3m and 33cm were measured after one week. Subjective performance was assessed on a numeric rating scale for vision clarity, lack of ghosting, vision stability, haloes, overall vision satisfaction and ocular comfort. Frequency of eye strain symptoms and willingness to purchase lenses were also reported with categorical responses.

Participants reported wearing times (total and visually acceptable). Linear mixed models and chi-square tests were employed in analysis with level of significance set at 5%. Theoretical optical performance of all lenses was assessed with schematic myopic model eyes (-1.00D, -3.00D and -6.00D) by comparing the slope of the edge spread function (ESF), an indicator for optical performance/resolution and the blur patch size of the line spread function, an indicator for contrast, between the lenses.

Researchers determined that Proclear Multifocal and MiSight provided the best distance acuities. However, the prototype lenses were rated significantly higher for many subjective variables, and there were no subjective variables where commercial lenses were rated significantly higher than the prototypes. Theoretical optical performance showed steeper slopes of the ESF and greater blur patch sizes of the LSP with commercial lenses, supporting the clinical findings of better visual acuities but reduced subjective performance. Participants wore prototypes longer and reported their vision was acceptable for longer each day compared with MiSight. Both prototypes had the highest willingness-to-purchase rate.

Researchers concluded that the prototypes were better tolerated by myopes compared with the commercial soft contact lenses currently used for slowing myopia progression.