Higher order aberrations in keratoconus .

INTRODUCTION: Keratoconus is a progressive disorder of the cornea that causes thinning (Sedaghat et al. in Sci Rep 11(1):11971, 2021), ectasia, and irregular astigmatism, resulting in poor visual acuity that cannot be corrected with standard sphero-cylindrical spectacle lenses. One feature distinguishing keratoconic corneas is ocular aberrations, manifesting up to five or six times the amount of higher-order aberrations than a normal, healthy eye. These aberrations can cause visual disturbances even at the very early stages of the disease. METHODS: In the past, a diagnosis was derived from clinical symptoms, but technological advances have revealed multiple pre-clinical features, allowing for the differentiation between keratoconic and normal eyes at a much earlier stage. These include anterior and posterior corneal surface elevations, the corneal pachymetry profile, corneal epithelial patterns, wavefront aberration metrics, and corneal biomechanics (Sedaghat et al. in Sci Rep 11(1):11971, 2021).This review discusses the aberrations associated with keratoconus, how to measure them, and treatment methods to minimize their negative influence. CONCLUSIONS: Early diagnosis can lead to early treatment and may allow for arresting progression, thereby improving the long-term prognosis. With the acceleration of refractive surgery, it is important to identify patients with keratoconus, as they are usually contraindicated for refractive surgery.

Intraocular lens power calculation in eyes with previous corneal refractive surgery.

Intraocular lens (IOL) power calculation after corneal refractive surgery (CRS) becomes an expanding challenge for ophthalmologists as more and more cataract surgeries after CRS are required. These patients typically also have high expectations as to visual performance. Conventional IOL power calculation schemes frequently provide inaccurate results in these cases. This review aims to summarize and recommend currently available IOL power calculation methods for eyes with the most common CRS methods: radial keratotomy (RK), photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE). To this end, biometry measuring methods and IOL formulas will be explained and combinations of both are proposed. In synopsis, it is evident that the latest generation of vergence formulas exhibit favorable IOL power prediction accuracy in post-CRS eyes, even though the predictive precision of methods in eyes without CRS is not attained. Ray tracing computation, intraoperative aberrometry, and machine learning-based formulas hold potential to further improve refractive outcomes in post-CRS eyes.

Why a dedicated section on keratoconus in the European Journal of Ophthalmology?

Keratoconus is emerging as a new subspecialty in ophthalmology. The literature is booming with publications on the topic as we have better understanding of the pathophysiology, treatment and prognosis of the disease over the past two decades. Advances in diagnostic tools as well as genuine increase in prevalence have shifted perspective of the disease from being a rare one. Early diagnosis is of public health interest as early treatment arrests progression. With the view to encourage research, increase awareness and to reflect the evolution of knowledge related to keratoconus, the European Journal of Ophthalmology has dedicate a special section on keratoconus in its journal.

Transient Horner syndrome following epidural anesthesia for labor: case report and review of the literature.

UNLABELLED: Epidural anesthesia is a widely used method for pain control during labor; nevertheless, it is not without risks. Horner syndrome is an uncommon related complication. We report a case of transient Horner syndrome following epidural anesthesia and a review of the literature. We discuss the pathophysiologic and contributing factors to this syndrome and its potential complications. TARGET AUDIENCE: Obstetricians & gynecologists, family physicians. LEARNING OBJECTIVES: After completion of this activity, physicians will be able to educate healthcare professionals working on the labor ward to be able to estimate the small incidence of Horner Syndrome following epidural anesthesia administered in labor. This will result in optimal management and will minimize the need for costly and inappropriate diagnostic investigations. The reader will also be able to compare the difference in the incidence of Horner syndrome following epidural anesthesia, as reported in the literature; appraise the clinical presentation, the pathophysiology, and the mechanism of Horner syndrome developing as a complication of regional anesthesia; and analyze the different theories proposed in the reported cases in the literature.

Laser ablation in eyes with congenital nystagmus.

PURPOSE: To report photorefractive keratectomy and LASIK for the correction of myopia in eyes with congenital nystagmus. METHODS: Photorefractive keratectomy was performed in one eye and LASIK performed in eight eyes of five adult patients (three men and two women) with congenital nystagmus. Mean patient age was 34 years. RESULTS: Preoperative refraction ranged between -1.50 and -22.00 diopters (D) sphere, and -0.50 and -3.25 D of astigmatism; best spectacle-corrected visual acuity (BSCVA) ranged between 2 m finger counting and 20/30. In all nine eyes, postoperative uncorrected visual acuity (UCVA) equaled or exceeded preoperative BSCVA. Postoperative topography showed central ablations. Results were stable at follow-up 18 months after surgery, except in one eye with follow-up of 4 months. Enhancement was not required in any eye. CONCLUSIONS: Positive results were achieved for ablation performed with a broad beam laser in eyes with nystagmus.

Reactivation of ocular toxoplasmosis after LASIK.

PURPOSE: To report a reactivation of ocular toxoplasmosis after LASIK. METHODS: Case report of a 34-year-old man who underwent bilateral LASIK. The posterior segment examination revealed an old toxoplasmosis scar in the retinal periphery of the right eye. RESULTS: Uncorrected visual acuity improved postoperatively, and the patient was satisfied. However, 52 days after the procedure, he complained of loss of visual acuity in his right eye. Examination revealed signs of anterior uveitis, vitreitis, and active chorioretinal lesion satellite of the old toxoplasmosis scar. The patient was treated with a multidrug regiment with resolution of the vitreous and lesion activity. CONCLUSIONS: Toxoplasmosis reactivation may develop after LASIK.

Management of pellucid marginal degeneration with intracorneal ring segments.

PURPOSE: To present intracorneal ring segments for potential management of pellucid marginal degeneration. METHODS: A 41-year-old man with pellucid marginal degeneration with poor visual acuity due to irregular astigmatism was treated with Intacs microthin insert (KeraVision, Fremont, Calif) in the left eye. RESULTS: Uncorrected visual acuity improved from 2/60 to 6/60 following the procedure. The procedure completely eliminated myopia of -8.00 diopters and improved the irregularity of the astigmatism, although it did not change its magnitude. CONCLUSIONS: Insertion of the intracorneal ring segment improves visual acuity in pellucid marginal degeneration by flattening the central corneal protrusion, thus reducing myopia and improving the astigmatism irregularity.

Intacs after laser in situ keratomileusis and photorefractive keratectomy.

PURPOSE: To evaluate the efficacy of intrastromal corneal ring segments (Intacs, Addition Technology) for the correction of residual myopia after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). METHODS: In this prospective noncomparative case series, Intacs were implanted in 5 eyes (4 patients) that developed myopic regression after LASIK or PRK. Intacs were implanted a minimum of 11 months after the laser procedure. The technique was identical to the standard procedure for myopic unoperated eyes. The Intacs thickness was based on the amount of residual myopia. RESULTS: Postoperative results revealed a reduction in the residual myopia and the mean K-reading. No eye lost best corrected Snellen visual acuity. No intraoperative or postoperative complications occurred. CONCLUSIONS: Implantation of Intacs in eyes with myopic regression after LASIK and PRK resulted in a good refractive outcome and an improvement in uncorrected visual acuity.

Keratitis after implantation of intrastromal corneal ring segments.

A 53-year-old man had implantation of 2 intrastromal corneal ring segments (Intacs, Addition Technology Inc.) in the left eye. Several days after the lower segment was exchanged, an infiltrate was present at the corneal incision site. This progressed to a lower channel infection followed by diffuse keratitis. Culture from the conjunctiva was positive for Staphylococcus epidermidis, but cultures from the cornea were negative for microorganisms. Later, 2 gas bubbles appeared at the interface. The patient was treated with topical and subconjunctival antibiotics and channel irrigation. The keratitis resolved, leaving a neovascularized opacity at the nasal part of the lower channel.