ABSTRACT
The aim of this study was to determine the effect of time of measurement on central corneal thickness in young myopes. Seventy healthy myopic subjects (non contact lens wearers) were involved in this study with mean age of 22.43 ± 1.76 years. Subjective refraction was determined using cross-cylinder technique, corneal curvature was measured using keratometer (Shin-Nippon) and central corneal thickness (CCT) was determined using specular microscope (Topcon SP-3000P). The CCT was measured in the morning (between 8 to 11 am) and in the afternoon (between 2 to 5 pm). The results showed that the mean of refraction for all subjects was -2.59 ± 1.85 DS and mean of cornea curvature was 7.74 ± 0.25 mm. Mean CCT in the morning was 517 ± 37 μm and 516 ± 36 μm in the afternon. Statistical analysis showed no significant difference between both measurements (T = 1.713 and P = 0.091). Correlation analysis showed insignificant correlation between CCT and refractive error (r = -0.078, p > 0.05) and CCT with corneal curvature in the horizontal meridian (r = 0.014, p > 0.05) and at vertical meridian (r = 0.029, p > 0.05). This study concluded that there is no significant effect of time of measurement on CCT in young myopes.
ABSTRACT
The aim of this study was to determine whether pattern-reversal Visual Evoked Potential (PRVEP) is affected in mild cognitive impairment (MCI). Participants aged ≥ 60 years diagnosed as MCI were invited to participate in a study together with a group of controls. PRVEP was measured using A RETI-port/Scan 21 and stimuli of large and small checks sizes, 1° (60 min of arc) and 0.25° (15 min) respectively were used to obtain responses. The amplitude and implicit times of the MCI and control groups were then compared. A total of 18 MCI participants (age 65.7 ± 3.1 years) and 18 controls (65.1 ± 3.8 years) consented to participate in the study. The amplitude and implicit times for the MCI group using the target sizes of 60 min of arc were 9.80 ± 4.06 μV and 108.83 ± 7.63 ms and for 30 min of arc were 11.00 ± 7.44 μV and 123.96 ± 6.18 ms respectively. Consecutively for the control groups the amplitudes and implicit times were 8.96 ± 3.52μV, 105.85 ± 3.60 ms and 11.97± 6.11 μV, 122.57 ± 8.28 ms. PRVEP results did not reveal significant differences in P100-wave amplitude nor implicit time between the two groups under investigation. This study concluded that the visual pathway of MCI participants may be unaffected in the early part of the disease process.
Subject(s)
AgedABSTRACT
It is possible that different techniques used to measure axial length (AL) and anterior chamber depth (ACD) is the cause of discrepancy in refractive outcomes of cataract surgery. This study evaluated the agreement and repeatability of AL and ACD measurements using immersion and contact A-scan biometry techniques and compared the refractive outcomes from both techniques. Twenty four patients were evaluated for agreement and repeatability of AL and ACD measurements using the two different methods. The results were analyzed using Bland and Altman plots. Another 60 patients with age-related cataract were selected to compare the refractive outcomes between both methods. The IOL power was calculated using Sanders- Retzlaff- Kraff- Theoretical (SRK-T) equation. Refraction was determined between four to six weeks postoperatively and the results were analyzed using paired t-test. The results of this study showed good agreement between both techniques was noted with no significant difference detected between measurements (p > 0.05). Significant correlation was found in all parameters (AL: r = 0.99; p < 0.01, r = 0.99; p < 0.01) ACD: r = 0.91; p < 0.01, r = 0.97; p < 0.01). No significant difference in refractive outcomes of post cataract surgery was detected between the two techniques (p = 0.07). This study concludes that contact A-scan biometry and immersion techniques provide reliable results and should not be the cause of discrepancy in the refractive planned and outcome of cataract surgery.
ABSTRACT
The purpose of this study is to determine the standard value of corneal thickness (CCT) and its relationship with the degree of myopia amongst one sample of myopic students in Malaysia. Eighty-four myopic subjects (168 eyes) were examined in this study. Ocular examination included subjective refraction, keratometry (Shin-Nippon, Japan) and optical pachometry (Sonogage INC). Corneal thickness was measured at five different locations i.e. central, superior, inferior, nasal and temporal of the cornea. However, only association of CCT with myopia is reported in this article. Mean age of subjects was 21.42 ± 1.47 years old (20.34 ± 1.15; 22.46 ± 0.88). Mean refractive error in spherical equivalent for the whole sample was –3.50 ± 2.10 DS. Mean corneal curvature for the all subjects was 7.74 ± 0.52 mm and mean value of CCT was 594.62 ± 66.51 mm. Significant differences (p 0.05) and between refractive error and corneal curvature (r = 0.24, p > 0.05). It was concluded from this study that high myopic subjects has significantly thinner CCT than lower ones. Measurement of CCT should be considered when undertaking procedures such as LASIK and orthokeratology.
ABSTRACT
This study illustrates and quantifies the changes on corneal tissue between the paraffin-embedded and resin-embedded blocks and thus, selects a better target in investigational ophthalmology and optometry via light microscopy. Corneas of two cynomolgus monkeys (Macaca fascicularis) were used in this study. The formalin-fixed cornea was prepared in paraffin block via the conventional tissue processing protocol (4-day protocol) and stained with haematoxylin and eosin. The glutaraldehyde-fixed cornea was prepared in resin block via the rapid and modified tissue processing procedure (1.2-day protocol) and stained with toluidine blue. The paraffin-embedded sample exhibits various undesired tissue damage and artifact such as thinner epithelium (due to the substantial volumic extraction from the tissue), thicker stroma layer (due to the separation of lamellae and the presence of voids) and the distorted endothelium. In contrast, the resin-embedded corneal tissue has demonstrated satisfactory corneal ultrastructural preservation. The rapid and modified tissue processing method for preparing the resin-embedded is particularly beneficial to accelerate the microscopic evaluation in ophthalmology and optometry.