Comparison of corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic pattern with inferior and superior steepening.

PURPOSE: To compare the corneal biomechanical parameters in healthy corneas with symmetric and asymmetric bow-tie topographic patterns. METHODS: In this cross-sectional study, 144 eyes were divided based on inferior-superior asymmetry value (I-S) into symmetric (zero I-S: - 0.50 to + 0.50 D) and asymmetric bow-tie topographic patterns with inferior (positive I-S: + 0.51 to + 1.4 D) or superior (negative I-S: - 2.5 to - 0.51 D) steepening. The biomechanical assessment was performed using Corvis ST and ocular response analyzer (ORA). A general linear model univariate analysis was used to compare the parameters, while the central corneal thickness, intraocular pressure, and age were considered covariates. RESULTS: Only the peak distance (PD) at the highest concavity phase (P = 0.007) and tomographic biomechanical index (TBI, P = 0.001) showed statistically significant differences between the three groups. For TBI, this difference was statistically significant between the positive I-S group separately with the zero I-S group (P < 0.001), and with the negative I-S group (P = 0.022). For PD, the significant difference was between the negative I-S group separately with zero I-S (P = 0.019), and positive I-S groups (P = 0.018). There was a statistically significant correlation between the I-S value with PD (r = 0.281, P = 0.001) and TBI (r = 0.170, P = 0.044). CONCLUSIONS: Most corneal biomechanical parameters are not statistically significant compared to the zero I-S group. However, superior steepening is associated with a stiffer response based solely on the shorter PD values seen in this group, and the group with the inferior steepening shows the highest or more suspicious values based on TBI.

After-effect on tear film quality and quantity of reading on laptop computer screen versus hardcopy.

CLINICAL RELEVANCE: Electronic displays, including laptops, tablets, and smartphones, have dramatically altered the way information is accessed and become significant factors in human daily life. They interfere with the blink rate and increase dry eye symptoms, which lead to more discomfort compared to hard copy while reading. BACKGROUND: Digital eye strain occurs when an individual suffers from symptoms, or they are exacerbated, while performing a task requiring digital screen viewing. This study assessed the tear film status immediately following reading on a laptop computer screen versus an identical hard copy. METHODS: Thirty young adults with normal ocular health and reporting no significant symptoms of dry eye (ocular surface disease index (OSDI) score < 13 and non-invasive tear break-up time (NITBUT) > 10 seconds) read a text as hard copy and on a laptop computer screen for 30 min on separate days in a random sequence in a controlled reading experimental condition. The texts were matched in size and contrast and presented at a viewing distance of 40 cm. The NITBUT and strip meniscometry tube tests were administered at baseline and after reading in both conditions. RESULTS: The median baseline NITBUT decreased from 13.0 s to 10.0 s (P < 0.001) after hardcopy reading and to 7.0 (P < 0.001) after reading from a laptop computer screen, with a significant difference between the task medium (P = 0.001). The baseline strip meniscometry tube results decreased from 6.7 mm to 5.0 mm (P < 0.001) after hardcopy reading and to 5.0 mm (P < 0.001) after reading from a laptop computer screen, but there was no significant difference with the task medium (P = 0.085). CONCLUSION: Reading in both conditions led to tear film instability in terms of the tear film quality and quantity. Additionally, the computer screen has a greater impact on the TBUT compared to hardcopy reading, while these two reading mediums had a similar effect on the tear volume.