The effect of prolonged and nocturnal use of contact lenses on the cornea: about a case of corneal decompensation and decreased endothelial count.

Corneal edema and decreased endothelial cell count are complications related to chronic low-grade hypoxia experienced by contact lens wearers, primarily due to prolonged and overnight wear. This case shows the example of a patient who has blurred vision problems in both eyes and who underwent a complete ophthalmologic examination that included photographs, corneal topography and endothelial cell count. Subsequently, the corneal metabolism, the etiopathogenesis and the complications derived from the use of contact lenses are reviewed.

Comparability of the Retinomax K-plus 3 handheld autorefractometer in quick mode versus on-table autorefractometer in standard mode.

INTRODUCTION: This study analyzes the comparability of measurements taken by a Retinomax K-plus 3 handheld autorefractometer in Quick mode and a Topcon KR-800 on-table autorefractometer in standard mode on the pediatric population, and establishes their correlation. METHODS: It is a retrospective comparative study. Spherical diopter power (SPH), cylindrical diopter power (CYL), angle of cylindrical axis (AX), and spherical equivalent (SE) were measured with the Retinomax in Quick mode and with the Topcon in standard mode. Each patient was evaluated in cycloplegic and non-cycloplegic conditions by both autorefractometers. Student's t-test was performed between the two instruments for SPH, CYL, and SE. The Pearson correlation coefficient was calculated and the dispersion was represented using Bland-Altman graphs, also evaluating the subgroup of patients under 4 years of age. A descriptive analysis of the percentages of measures that differed was performed. RESULTS: It included 98 eyes of 49 subjects (age range: 3-16 years). The data for HPS without cycloplegia are virtually identical, whereas with cycloplegia there is a hyperopic bias of +0.5 diopters measured with Retinomax. CYL results are very similar with and without cycloplegia. There is a high Pearson correlation for both instruments (>0.91) and a low degree of dispersion in the Bland-Altman plots under cycloplegia. CONCLUSION: The Retinomax data were consistent with those obtained by Topcon. The Retinomax is a useful instrument for detecting refractive errors in children between 3 and 16 years of age.

Permanent damage of the inner retinal layers in a patient with migraine: a different case of paracentral acute middle maculopathy.

We report the case of a 20-year-old patient who presented a paracentral scotoma in her left eye that had not disappeared after a migraine attack two days before. Ocular examination showed two pale paracentral areas suggesting an acute ischemia insult. Several causes of retinal ischemia were ruled out and the patient was diagnosed with secondary retinal vasospasm. One year later, the patient suffers an atrophy of the inner layers of the affected retina and has a paracentral chronic scotoma in her left eye. Retinal vasospasms can result in irreversible lesions and chronic symptoms due to ischemia and cell destruction. This unusual case reports a permanent damage due to retinal vasospasm secondary to migraine attack. The finding of typical lesions and the history of migraine could be compatible with the diagnosis of paracentral acute middle maculopathy (PAMM).

Limits of the precision in refractive results after cataract surgery.

BACKGROUND AND OBJECTIVE: In order to improve refractive results in cataract surgery with an intraocular lens implant, it is important to know the sources of error as well as the limit of this process. Therefore, the objective of the present work is to approximate the theoretical limit in the precision in the refractive result after cataract surgery with the currently available means and to assess the impact of different sources of error in this process. MATERIALS AND METHODS: We conducted a search of the literature to determine the variability provided by each component of the process. Based on the Barrett Universal-II formula, we performed an error propagation analysis. The theoretical limit was defined as the situation in which the refractive result is only affected by the variability in the parameters introduced in the formula, the tolerance of the intraocular lens and the subjective refraction. RESULTS: The main contributors to the error were (1) intraoperative and postoperative variability variables not considered by the formulas (49.33%), (2) postoperative subjective refraction (38.29%), (3) mean keratometry (5.98%) and (4) the variability in the labelling of the power of the intraocular lens (5.09%). The theoretical limit obtained for the intraocular lens calculation with the means available today was 91.9% of the eyes between ±0.50D. CONCLUSIONS: We found a theoretical limit for the intraocular lens calculation of 91.9% of the eyes between ±0.50D. Approaching the precision limit described in the study requires the use of optical biometrics and state-of-the-art formulas, a reproducible surgical technique, and the compensation of systematic errors by adjusting constants.