Off the Cuff: The Value of Caring

A multicenter survey was conducted using a questionnaire, in eight contact lens (CL) centers among two groups of presbyopes: successful wearers (SWs), who were presbyopic and wearing CLs successfully; and unsuccessful wearers (UWs), who tried unsuccessfully to wear CLs to manage their presbyopia and had stopped wearing CLs to evaluate the key factors behind successful and unsuccessful wear of CLs for patients with presbyopia.

A total of 237 completed questionnaires were returned; 178 from SWs and 59 from UWs. Successful wearers used CLs 5.8 ±1.5 days a week, and additional reading spectacles were never used by half of the SWs. Among SWs, the most important reason to continue wearing CLs was convenience (61%), whereas among UWs, the most important reason to discontinue wearing CLs was poor vision (80%). A logistic regression analysis showed that the absence of astigmatism, a higher subjective satisfaction, a better subjective perceived vision at distance and a lower subjective loss of visual contrast were able to predict the success of CL use for presbyopia.

This study explored the predictors for determining successful or unsuccessful CL wear in presbyopes. Researchers wrote that, among ophthalmic, demographic, lifestyle and subjective variables, the latter seemed to be of greater importance in determining the success of CL wear. Therefore, they added, it is necessary that subjective variables are taken into account by the CL practitioner when approaching presbyopic CL fitting in practice.

Investigators systematically conducted this meta-analysis based on observational studies published up to Jan. 15 2018, identified from PubMed and Web of Science to address inconsistency as well as investigate the relationship between glaucoma and the risk of Alzheimer's disease (AD). Two team members independently extracted the data and assessed the quality of each included study. Summary relative risk (RR) and 95% confidence intervals (CIs) were calculated using a random-effects model. Eight observational studies with 6,870 AD cases were included.

The majority of these studies (n=6) were graded as low risk according to the Newcastle-Ottawa Quality Assessment Scale. Individuals diagnosed with glaucoma, compared with those who were not, had an increased risk of AD (RR=1.52; CI: 1.41 to 1.63; I2=97%). A significant finding was also observed for primary open-angle glaucoma (RR=1.52; CI: 1.41 to 1.63; I2 =97%). However, when stratified by study design, only the case-control studies (RR=1.08; CI: 0.89 to 1.31; I2=37.3%) yielded significant results, while the cohort studies did not (RR=1.08; CI: 0.89 to 1.31; I2=97.7%). Of note, our meta-regression analysis suggested that study design might be a source of heterogeneity. Additionally, a significantly positive association was observed when the analyses were restricted to Asia (RR=2.03; CI: 1.02 to 4.07). There was no significant publication bias in these analyses.

Investigators wrote that recent evidence suggests that glaucoma may increase the risk of AD. They concluded that additional cohort studies would be needed to confirm these findings and to have improved knowledge on the true nature of this association.

An axially symmetric finite element model of the posterior eye was constructed with an elongated optic nerve and retro-orbital subarachnoid space ensheathed by pia and dura mater to characterize the relative contributions of intraocular pressure (IOP) and intracranial pressure (ICP) on lamina cribrosa (LC) behavior, specifically LC depth (LCD) and LC peak strain. The mechanical environment in LC was evaluated with ICP ranging from 5mm Hg to 15mm Hg and IOP from 10mm Hg to 45mmHg. LCD and LC peak strains at various ICP and IOP levels were estimated using full factorial experiments. Multiple linear regression analyses were then applied to estimate LCD and LC peak strain using ICP and IOP as independent variables.

Both increased ICP and decreased IOP led to a smaller LCD and LC peak strain. The regression correlation coefficient for LCD was -1.047 for ICP and 1.049 for IOP, and the ratio of the two regression coefficients was -1. The regression correlation coefficient for LC peak strain was -0.025 for ICP and 0.106 for IOP, and the ratio of the two regression coefficients was -0.24. A stiffer sclera increased LCD but decreased LC peak strain; besides, it increased the relative contribution of ICP on the LCD but decreased that on the LC peak strain.

ICP and IOP have opposing effects on LCD and LC peak strain. While their effects on LCD are equivalent, the effect of IOP on LC peak strain is three times larger than that of ICP. The influences of these pressure are dependent on sclera material properties, which might explain the pathogenesis of ocular hypertension and normal-tension glaucoma.