Effect of time of measurement on central corneal thickness in a sample of young myopes

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

Clinical characteristics of keratoconus patients in Malaysia: a review from a cornea specialist centre

AbstractPurposeTo evaluate the demographic profile, refraction, visual acuity (VA), corneal curvature (K) and severity of keratoconus (KC) patients from a cornea specialist centre in Malaysia. This may improve the management of KC patients in this country.MethodsRecords of 13,000 patients were reviewed. The patients were categorized into 4 age groups: (Gp 1: <23 years, Gp 2: 23–32 years, Gp 3: 33–42 years, Gp 4: >42 years). Refraction and VA were determined using subjective refraction and Snellen chart. Corneal curvature was measured using Orbscan II topography. Severity of KC was graded following Amsler–Krumeich system. Data were analysed according to age, gender and ethnicity.ResultsA total of 159 patients had KC and the prevalence was 1.2%. Mean age of onset was 20.9±5.6 years, with 71.1% of males and 28.9% of females. Majority were of Indian and Malay origins. Percentages of patients within each age group were 26.4%, 52.8%, 18.9% and 1.9% respectively. Regarding severity, 37.6% were stage I, 30.1% stage II, 4.4% stage III and 27.8% stage IV at the time of diagnosis. The age of onset, refraction, mean K and VA was found to be similar between gender and ethnicity (p>0.05). Age of onset was not strongly correlated to the severity of the disease.ConclusionThis study concludes that there are higher percentages of Malays and Indians with KC than other races in Malaysia. The condition was found to manifest at a younger age and was more common in males than females. These findings should be considered during vision screening in Malaysia

Pattern Visual Evoked Potential (VEP) is unaffected in the early stage of mild cognitive impairment

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

Mild cognitive impairment does not affect pattern electroretinogram in the elderly - a pilot study

The purpose of this study was to examine the effects of mild cognitive impairment on pattern electroretinogram (pERG) among urban elderly Malays. A total of 36 subjects aged 60 years and above comprising of 18 MCI subjects and 18 normal controls were recruited for this study. The inclusion criteria for both the MCI and normal subjects included best corrected distance visual acuity ≥ 6/9 (Snellen) with refractive error less than ±4.00 DS and/or ±2.00 DC (astigmatism), near visual acuity ≥ N8, absence or no previous history of any significant media opacities, retinal disorders and ocular pathologies. pERG was recorded with the RetiPort/Scan21 system in accordance with the International Society for the Clinical Electrophysiology of Vision standards. The target presented to subjects through a 19” CRT monitor was a black and white reversing checkerboard with luminance equal to 80 cd/m2, contrast 97% and stimulus frequency 2.00 Hz (4 rev/s). Amplitudes and implicit times of P50 and N95 waves generated by the system were noted and compared between the two groups. The results showed no significant difference in the amplitude and implicit times between the right and left eyes so only the right eye was used for comparison between the MCI and control groups. The mean amplitude and implicit times of the right eye of the MCI and control groups were 1.86±0.65 μV, 56.27±6.20 ms and 1.54±0.74 μV, 56.15±4.98 ms, respectively. T-test showed no significant differences in pERG amplitudes and implicit times between MCI and the control groups. In conclusion, our results may imply that the inner retina is intact in early MCI elderly subjects

Refractive error and visual acuity of elderly Chinese in Selangor and Johor, Malaysia

The first aim of this study was to determine the refractive error and visual acuity of Chinese elderly age 60 and above in Selangor and Johor, Malaysia. The second aim was to determine the percentage of elderly with vision impairment. Participants of this study were from the on-going population-based longitudinal study on neuroprotective model for healthy longevity (TUA) among Malaysian older adults using multistage random sampling. A total of 259 Chinese elderly aged 60 and above from state of Selangor and Johor agreed to participate. Refractive error was determined using autorefractometer Retinomax K-plus followed by subjective refraction. Best corrected visual acuity (VA) was measured using logMAR chart. Analysis was performed on data of 202 participants and the remaining 57 were excluded. Overall percentage of refractive error was higher for hyperopia (54%) compared to myopia (23.2%). High percentage of astigmatism was noted for all age groups (> 50%). Both gender showed similar distribution of refractive status. Mean overall VA was 0.24 ± 0.17 logMAR (≅ 6/9–) and mean VA declined with age. Overall, the percentage of elderly having at least mild vision impairment (> 0.3 logMAR or 6/12) was higher (62.9%) compared to normal vision (≤ 0.3 logMAR). However, percentage of vision impairment (VI) was highest in the mild category compared to others and only one participant had severe VI. This study found a high percentage of Chinese elderly with refractive error. The most common type of refractive error was hyperopia. A high proportion of them had mild vision impairment followed by moderate VI even with best correction. Vision impairment could affect daily life functioning and this effect can be further explored in the future

The resin-embedded cornea prepared via rapid processing protocol : a good histomorphometric target for clinical investigation in opthalmology and optometry.

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

Colour vision status of staff working with radiation in public hospital

Growing application of radiation sources and lack of awareness among workers in practicing protective measures imply an increased risk of radiation exposure to eye. This study determined the status of colour vision and its association with working duration amongst staff working with radiation in a university hospital. A total of 55 employees (28 exposed (RS) and 27 not directly exposed to radiation (NRS)) were recruited and 30 employees were used as controls. Visual acuity (VA) was measured using Snellen chart. Colour vision assessments were conducted using Ishihara plates, D15 panel and FM 100 hues and the results were analysed using one way ANOVA. The subjects’ age ranged between 29 and 44 years old. Mean VA for all subjects was 6/6. More than 50% of the subjects has colour defects, 3.45% of RS failed D15, 37.93% failed FM 100 hue, 7.4% of NRS failed D15 and 55.56% failed FM 100 hue. Significant difference was found in the total error scores between RS (77.10 ± 6.05) and NRS (84.89 ± 7.76) with the controls (41.47 ± 3.10) [ANOVA F(2,83)=16.084, p=0.00]. There was no association between working duration and severity of colour defect [r(104)= -0.123, p>0.05]. This study concludes that majority of the studied subjects has color deficiency but not significantly correlated with their working duration. Protective measures need to be taken to improve the situation

Soal selidik kendalian kendiri indeks fungsi visual (VF14) dan korelasinya dengan akuiti visual koreksi terbaik pada warga emas

Kajian ini dilakukan untuk menentukan skor kendalian kendiri indeks fungsi visual (VF14) dan korelasinya dengan akuiti visual koreksi terbaik pada warga emas. Subjek kajian ialah warga emas berumur 60 tahun ke atas yang mengambil bahagian dalam kajian yang sedang dijalankan iaitu“Model Perlindungan Neuro Bagi Penuaan Sihat Di Kalangan Warga Emas (TUA). Akuiti visual diukur dengan menggunakan carta logMAR. Penilaian soal selidik kendalian kendiri diukur menggunakan Indeks Fungsi Visual (VF14) berbahasa Melayu yang telah diubah suai. Seramai 482 (93.05%) daripada 518 subjek kajian telah mengambil bahagian dalam kajian ini. Purata umur subjek kajian ialah 69.18 ± 5.67 tahun dan purata akuiti visual koreksi terbaik ialah logMAR 0.21 ± 0.17. Purata skor VF14 ialah 89.65 ± 13.19. Perempuan mempunyai purata skor VF14 yang lebih rendah jika dibandingkan dengan lelaki (skorperempuan89.21 ± 12.76, skorlelaki90.11 ± 13.65) tetapi tidak ada perbezaan secara statistik (z= -1.09, p= 0.277). Terdapat korelasi yang sederhana tetapi signifikan antara skor VF14 dan akuiti visual koreksi terbaik (r = -0.412, p < 0.01). Kesimpulannya, akuiti visual koreksi terbaik sahaja tidak boleh digunakan sebagai indikator untuk menjelaskan perubahan skor VF14. Kajian ini menunjukkan ia hanya menyumbang kepada 17.2% kepada perubahan skor VF14. Gabungan banyak faktor lain seperti faktor sosio demografik (bangsa, status pendidikan dan masalah kesihatan), sensitiviti kontras dan stereopsis perlu diambil kira apabila menilai fungsi visual yang diukur dengan VF14

Histomorphometric profile of the corneal response to short-term reverse-geometry orthokeratology lens wear in primate corneas: a pilot study

Purpose: To investigate the histological changes in primate cornea induced by short-term overnight orthokeratology (OK). Methods: Nine young adult primates were used. One animal served as negative control. The remaining 8 animals wore reverse-geometry OK lenses for periods of 4, 8, 16, and 24 hours on 1 eye with the other eye as control. Central and midperipheral corneal thickness, as well as ultrastructural changes in corneal epithelium, stroma and endothelium in response to OK lenses, were evaluated. Results: OK significantly reduced the thickness of the central cornea in all treatment groups. The central corneal thinning was both stromal and epithelial in origin. Substantial midperipheral corneal thickening was seen in 16-hour and 24-hour lens-wear groups and this effect was both stromal and epithelial in origin as well. Histology evidence indicated the primary epithelial response in the central cornea was compression of cells that resulted in wing cells becoming shorter and basal cells being squatted rather than lost or migration of cell layers. These pronounced cell shape changes occurred without compromising the structural integrity of the desmosomes. The thickened corneal epithelium has normal cell layers. The squamous cells have larger surface sizes and are composed of oval instead of flattened nuclei. This implied delayed surface cell exfoliation at the thickened midperipheral epithelium. Physical presence of OK lens over the cornea did not influence the microstructures of microvilli and microplicae, endothelium, and collagen distribution. Conclusions: The primate cornea, particularly the corneal epithelium, responds rapidly to the application of reverse-geometry OK lenses with significant epithelial cell shape alterations with short-term OK lens wear. This finding suggests that the corneal epithelium is moldable in response to the physical forces generated by the OK lenses

Ketamine-xylazine/tiletamine-zolazepam prolonged anesthesia in Cynomolgus monkeys

The physiological effects of a mixture of ketamine, xylazine, tiletamine and zolazepam (KT/XZ), in cynomolgus monkeys during 24 hr anesthesia is described. Eight were induced with ketamine IM and anesthetized with IV KT/XZ. In all, anesthesia was maintained for 24 hours with large decreases in rectal temperature, heart and respiratory rates but moderate hypotension. All monkeys recovered normally 4 hours post-anesthesia. These results suggest that KX/TZ mixture could be used for prolonged anesthesia in cynomolgus monkeys