An update on intraocular lens power calculations in eyes with previous laser refractive surgery.

PURPOSE OF REVIEW: There is an ever-growing body of research regarding intraocular lens (IOL) power calculations following photorefractive keratectomy (PRK), laser-assisted in-situ keratomileusis (LASIK), and small-incision lenticule extraction (SMILE). This review intends to summarize recent data and offer updated recommendations. RECENT FINDINGS: Postmyopic LASIK/PRK eyes have the best refractive outcomes when multiple methods are averaged, or when Barrett True-K is used. Posthyperopic LASIK/PRK eyes also seem to do best when Barrett True-K is used, but with more variable results. With both aforementioned methods, using measured total corneal power incrementally improves results. For post-SMILE eyes, the first nontheoretical data favors raytracing. SUMMARY: Refractive outcomes after cataract surgery in eyes with prior laser refractive surgery are less accurate and more variable compared to virgin eyes. Surgeons may simplify their approach to IOL power calculations in postmyopic and posthyperopic LASIK/PRK by using Barrett True-K, and employing measured total corneal power when available. For post-SMILE eyes, ray tracing seems to work well, but lack of accessibility may hamper its adoption.

Contrasting cellular damage after Blue-IRIS and Femto-LASIK in cat cornea.

Blue-intra-tissue refractive index shaping (Blue-IRIS) is a new approach to laser refractive correction of optical aberrations in the eye, which alters the refractive index of the cornea rather than changing its shape. Before it can be implemented in humans, it is critical to establish whether and to what extent, Blue-IRIS damages the cornea. Here, we contrasted the impact of -1.5 D cylinder refractive corrections inscribed using either Blue-IRIS or femtosecond laser in-situ keratomileusis (femto-LASIK) on corneal cell viability. Blue-IRIS was used to write a -1.5 D cylinder gradient index (GRIN) lens over a 2.5 mm by 2.5 mm area into the mid-stromal region of the cornea in six freshly-enucleated feline eyes. The same correction (-1.5 D cylinder) was inscribed into another four cat eyes using femto-LASIK. Six hours later, all corneas were processed for histology and stained for terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) and p-γ-H2AX to label damaged cells. In Blue-IRIS-treated corneas, no tissue was removed and TUNEL-stained cells were confined to the laser focal zone in the stroma. In femto-LASIK, photoablation removed 14 µm of anterior stroma, but in addition, TUNEL-positive cells clustered across the femto-flap, the epithelium at the flap edges and the stroma below the ablation zone. Keratocytes positive for p-γ-H2AX were seen adjacent to all Blue-IRIS focal zones, but were completely absent from femto-LASIK-treated corneas. Unlike femto-LASIK, Blue-IRIS attains refractive correction in the cornea without tissue removal and only causes minimal, localized keratocyte death within the laser focal zones. In addition, Blue-IRIS induced DNA modifications associated with phosphorylation of γ-H2AX in keratocytes adjacent to the laser focal zones. We posit that this p-γ-H2AX response is related to alterations in chromatin structure caused by localized changes in osmolarity, a possible mechanism for the induced refractive index changes.

Intrastromal Antibiotic Injection in Polymicrobial Keratitis: Case Report and Literature Review.

Bacterial keratitis (corneal infection) caused by more than one organism is rare and exceedingly difficult to treat due to variable antibiotic susceptibilities. Intrastromal injections of antibiotics may be necessary to achieve higher drug concentrations at the site of infection, particularly in the case of deep stromal disease refractory to topical therapy. However, while this approach is increasingly used for fungal keratitis, there is a paucity of the literature regarding the use of intrastromal antibiotics bacterial keratitis. In the current case, an 86-year-old patient presented with a left corneal ulcer with corresponding microbiologic cultures positive for Staphylococcus epidermidis, Staphylococcus aureus, and Achromobacter species. The ulcer continued to progress despite maximal topical antibiotic treatment yet demonstrated marked improvement after two intrastromal injections of moxifloxacin administered 2 weeks apart. Polymicrobial keratitis can be particularly challenging to eradicate despite maximal topical antibiotic therapeutics. Intrastromal corneal injections provide a mechanism for drug delivery directly to the site of infection and thus may represent an important alternative in refractory cases.

Short-term, high-dose hydroxychloroquine corneal toxicity.

PURPOSE: To describe the corneal findings and management of a 61-year-old female with vortex keratopathy following short term, high dose hydroxychloroquine used in the setting of a clinical trial for recurrent breast cancer. OBSERVATIONS: The patient was found to have significant corneal vortex keratopathy without retinal pathology within 3 months of 1200 mg daily hydroxychloroquine treatment as an adjuvant medication for cancer therapy. Cessation of the medication led to the resolution of the corneal verticillata within 1 month yet the vision did not return to baseline. Ultimately, remaining irregular astigmatism and ocular surface disease required a scleral contact lens to achieve a BSCVA of 20/25 OU. CONCLUSIONS AND IMPORTANCE: Hydroxychloroquine-induced vortex keratopathy is largely considered dose and duration dependent and is uncommon with most standard treatment algorithms. However, with increasing use of high-dose hydroxychloroquine in adjunct cancer therapy, corneal findings are likely to become more frequent. Persistent visual impairment may occur, thus increased understanding of this pathology can aid in counseling patients and guiding treatment recommendations.

Comparable change in stromal refractive index of cat and human corneas following blue-IRIS.

Blue intratissue refractive index shaping (blue-IRIS) is a method with potential to correct ocular refraction noninvasively in humans. To date, blue-IRIS has only ever been applied to cat corneas and hydrogels. To test the comparability of refractive index change achievable in cat and human tissues, we used blue-IRIS to write identical phase gratings in ex vivo feline and human corneas. Femtosecond pulses (400 nm) were focused ? 300 ?? ? m below the epithelial surface of excised cat and human corneas and scanned to write phase gratings with lines ? 1 ?? ? m wide, spaced 5 ?? ? m apart, using a scan speed of 5 ?? mm / s . Additional cat corneas were used to test writing at 3 and 7 ?? mm / s in order to document speed dependence of the refractive index change magnitude. The first-order diffraction efficiency was immediately measured and used to calculate the refractive index change attained. Our data show that blue-IRIS induces comparable refractive index changes in feline and human corneas, an essential requirement for further developing its use as a clinical vision correction technique.

First demonstration of ocular refractive change using blue-IRIS in live cats.

PURPOSE: To determine the efficacy of intratissue refractive index shaping (IRIS) using 400-nm femtosecond laser pulses (blue light) for writing refractive structures directly into live cat corneas in vivo, and to assess the longevity of these structures in the eyes of living cats. METHODS: Four eyes from two adult cats underwent Blue-IRIS. Light at 400 nm with 100-femtosecond (fs) pulses were tightly focused into the corneal stroma of each eye at an 80-MHz repetition rate. These pulses locally increased the refractive index of the corneal stroma via an endogenous, two-photon absorption process and were used to inscribe three-layered, gradient index patterns into the cat corneas. The optical effects of the patterns were then tracked using optical coherence tomography (OCT) and Shack-Hartmann wavefront sensing. RESULTS: Blue-IRIS patterns locally changed ocular cylinder by -1.4 ± 0.3 diopters (D), defocus by -2.0 ± 0.5 D, and higher-order root mean square (HORMS) by 0.31 ± 0.04 µm at 1 month post-IRIS, without significant changes in corneal thickness or curvature. Refractive changes were maintained for the duration they were tracked, 12 months post-IRIS in one eye, and just more than 3 months in the remaining three eyes. CONCLUSIONS: Blue-IRIS can be used to inscribe refractive structures into live cat cornea in vivo that are stable for at least 12 months, and are not associated with significant alterations in corneal thicknesses or radii of curvature. This result is a critical step toward establishing Blue-IRIS as a promising technique for noninvasive vision correction.