Off the Cuff: This. That. And Other Things

Twenty participants suspected of having obstructive sleep apnea syndrome (OSAS) were recruited to analyze nocturnal intraocular pressure (IOP) fluctuations in patients with OSAS using a contact lens sensor (CLS) and to identify associations between the OSAS parameters determined by polysomnographic study (PSG) and IOP changes. During PSG study, IOP was monitored using a CLS placed in the eye of the patient. The patients were classified according to the apnea-hypopnea index (AHI) in two categories, severe (>30) or mild/moderate (<30) OSAS. Researchers evaluated several parameters determined by the IOP curves, including nocturnal elevations (acrophase) and plateau times in acrophase (PTs) defined by mathematical and visual methods.

The IOP curves exhibited a nocturnal acrophase followed by PTs of varying extent at which the IOP remained higher than daytime measurements with small variations. Researchers found significant differences in the length of the PTs in patients with severe OSAS compared with those with mild/moderate disease. Researchers found a positive correlation between PTs and OSAS severity measured by the total number of apneic events and AHI. Respiratory-related arousal and oxygen saturation also were associated significantly with the IOP PT length.

Periods of nocturnal IOP elevation lasted longer in severe OSAS patients than those with mild/moderate OSAS and correlated with the severity of the disease. The length of the nocturnal PT was also associated with respiratory parameters altered in patients with OSAS.

Excimer laser ablation is an increasingly popular option for the correction of mild to moderate refractive errors in the United States. It is generally regarded as safe, with an overall annual complication rate of less than 0.8% since 2010.

Central toxic keratopathy (CTK), first described in 1998, has numerous alternative descriptive names including stage IV diffuse lamellar keratitis, central lamellar keratitis, central flap necrosis, central necrosis lamellar inflammation and keratinocyte-induced corneal micro edema (KME). This rare clinical syndrome classically presents as a central or paracentral, amorphous corneal opacification with associated striae, stromal loss and hyperopic shifts that usually present within nine days of excimer laser ablation (i.e., laser-assisted keratomileusis (LASIK) or photorefractive keratopathy [PRK]). It is believed to be non-inflammatory, but its cause is still unknown.

Though initially thought of as a progression, or severe form, of diffuse lamellar keratitis (DLK), there is significant support that CTK is a distinct and separate entity from DLK. In addition to cases in other refractive surgeries, there are proposals that CTK exists as an entity outside of the refractive surgery literature. There have been reports of CTK associated with contact lens use with and without recent mechanical debridement, idiopathically, as well as potentially with selective laser trabeculoplasty or topical anesthetic use.

These researchers evaluated the antimicrobial efficacy of a povidone-iodine system (PVP-I; cleadew, OPHTECS), a peroxide system (AOSEPT Plus with HydraGlyde, Alcon), and a chemical multipurpose system (renu fresh, Bausch & Lomb) on contact lens case surfaces that are both in contact and not in contact with the solutions during lens disinfection. The surfaces of the inner walls, underside of the lid, and lens holder (if applicable) of the cases were inoculated with P. aeruginosa ATCC 27853. The cases were disinfected with the solutions as per their manufacturer instructions. After disinfection, the inoculated surfaces were swabbed and the amount of surviving P. aeruginosa was determined. Following this experiment, separate cases were inoculated and disinfected as before. This time the cases were agitated after recommended disinfection time and the amount of P. aeruginosa in the disinfecting solution was quantified immediately, and again after resting for seven days. Experiments were conducted in triplicate (n=3).

Units were expressed in log CFU. All three solutions significantly reduced P. aeruginosa on direct-contact surfaces. On non-contact surfaces, the reduction of P. aeruginosa in the PVP-I system (pre-disinfection: 6.8 ± 0.5, post-disinfection: 1.0 ± 0.0) was significant, but not for the hydrogen peroxide system (pre-disinfection: 6.3 ± 0.6, post: 5.5 ± 0.5) and the chemical multipurpose system (pre-disinfection: 6.6 ± 0.1, post-disinfection: 5.6 ± 0.8). After seven days post-disinfection, no P. aeruginosa regrowth was observed in the PVP-I system (Day 1: 1.0 ± 0.0, Day 7: 1.0 ± 0.0) and the chemical multipurpose system (Day 1: 4.2 ± 0.2, Day 7: 1.8 ± 0.9); however, regrowth was observed in the hydrogen peroxide system (Day 1: 3.4 ± 0.6, Day 7: 6.1 ± 0.4).

The PVP-I system was more effective against P. aeruginosa on non-contact surfaces than the hydrogen peroxide system or the chemical multipurpose system and was capable of inhibiting regrowth of P. aeruginosa for at least seven days post-disinfection.