The genetic and environmental factors for keratoconus

Keratoconus (KC) is the most common cornea ectatic disorder. It is characterized by a cone-shaped thin cornea leading to myopia, irregular astigmatism, and vision impairment. It affects all ethnic groups and both genders. Both environmental and genetic factors may contribute to its pathogenesis. This review is to summarize the current research development in KC epidemiology and genetic etiology. Environmental factors include but are not limited to eye rubbing, atopy, sun exposure, and geography. Genetic discoveries have been reviewed with evidence from family-based linkage analysis and fine mapping in linkage region, genome-wide association studies, and candidate genes analyses. A number of genes have been discovered at a relatively rapid pace. The detailed molecular mechanism underlying KC pathogenesis will significantly advance our understanding of KC and promote the development of potential therapies

Chinese eye exercises and myopia development in school age children: a nested case-control study

Chinese eye exercises have been implemented in China as an intervention for controlling children’s myopia for over 50 years. This nested case-control study investigated Chinese eye exercises and their association with myopia development in junior middle school children. Outcome measures were the onset and progression of myopia over a two-year period. Cases were defined as 1. Myopia onset (cycloplegic spherical equivalent ≤ −0.5 diopter in non-myopic children). 2. Myopia progression (myopia shift of ≥1.0 diopter in those who were myopic at baseline). Two independent investigators assessed the quality of Chinese eye exercises performance at the end of the follow-up period. Of 260 children at baseline (mean age was 12.7 ± 0.5 years), 201 were eligible for this study. There was no association between eye exercises and the risk of myopia-onset (OR = 0.73, 95%CI: 0.24–2.21), nor myopia progression (OR = 0.79, 95%CI: 0.41–1.53). The group who performed high quality exercises had a slightly lower myopia progression of 0.15 D than the children who did not perform the exercise over a period of 2 years. However, the limited sample size, low dosage and performance quality of Chinese eye exercises in children did not result in statistical significance and require further studies

Current applications and efficacy of scleral contact lenses — a retrospective study

Purpose: To evaluate the indications and efficacy of high gas permeable scleral contact lenses (GP-SCL). Methods: A total database of 97 consecutive patients (140 eyes) fitted with GP-SCL between January 2003 and December 2008, was retrospectively analyzed to determine the benefits of fitting scleral lenses. All lenses were fitted by preformed technique and were non-fenestrated. Patients included keratoconus – 88 eyes (63 %); corneal irregularities after penetrating keratoplasty – 39 eyes (28 %); various ocular surface disorders: Stevens-Johnson syndrome (SJS), graft versus host disease (GVHD) and exposure keratopathy – 6 eyes (4 %); post refractive surgery keratoectasia – 4 eyes (3 %), and high refractive error – 3 eyes (2 %). Results: Mean follow up was 27.5 months (range 1–71), mean wearing time in successful wearers group was 12.2 hours per day (range 10–16), mean wearing time in group of wearers who dropped out using GP-SCL, was 5.8 hours (range 3–8). Keratoconus patients achieved median best corrected visual acuity (BCVA) of 20/32, 84 % of patients achieved BCVA of 20/40 or more. The post keratoplasty group achieved median BCVA of 20/25, 92 % of patients achieved BCVA of 20/40 or better. In the other groups, median BCVA was as follows: ocular surface disorders – 20/50, keratoectasia – 20/30, high refractive error – 20/32. Positive fluid-venting was highly associated with successful GP-SCL wearing. Twenty patients (21 %) failed to wear GP-SCL. Conclusions: GP-SCL's expand the management of various corneal abnormalities. The main indication for GP-SCL is optical correction of an irregular corneal surface, especially keratoconus and corneal transplant

SENSITIVITY AND FRAGILITY IN KERATOCONUS

38 persons with various degrees of keratoconus were examined. Using the photokeratoscope an index of the severity of the cone was established and compared to a group of normal eyes. Sensitivity was measured in the centre and periphery of the cornea. It was found to be significantly lower than in normal eyes and those eyes wearing contact lenses exhibited the lowest sensitivity. There was no correlation between peripheral CTT (Corneal Touch Threshold) and the severity of keratoconus, but there was a significant correlation between central CTT and severity, though only for the group of eyes not wearing contact lenses. Corneal fragility was also found to be greater in keratoconus than in normal eyes and more so in those eyes wearing contact lenses. There was a significant correlation between the severity and the fragility. 1983 Institution Acta Ophthalmologica Scandinavic

Amplitude of accommodation and refractive error

No. 7 Reports 1187 Amplitude of Accommodation and Refractive Erro

Validation of keratometric measurements obtained with a new integrated aberrometry-topography system

Purpose: A clinical evaluation of the L80 videokeratographer (Visionix Luneau, Chartres, France) was performed to assess its validity and repeatability compared with a traditional Bausch and Lomb (B & L) keratometer. Methods: 87 right eyes of 87 subjects, (mean age 23.72 ± 3.62 years old, 70 women and 17 men), participated in this study. Corneal curvature was measured using the L80 instrument by one practitioner and the manual B & L keratometer by a different practitioner. Intratest and intertest repeatability were assessed. Results: Corneal curvature was found to be statistically different between the two instruments (p < 0.001), with the L80 providing a slightly steeper bias of 0.05 mm and 0.07 mm for the horizontal and vertical meridians, respectively than the B & L keratometer. 78.2% and 86.2% of the L80 results were within ±0.1 mm (±0.06 D) and 95.4% and 97.7% within ±0.2 mm (±0.11 D) of the readings obtained with the B & L keratometer along the horizontal and the vertical meridians, respectively. The agreement between the L80 and B & L keratometers axes was 31.0% within ±5°, 54.0% within ±10°, 60.9% within ±15°, 71.3% within ±20° and 87.4% within ±40°. Intratest repeatability was the same for both instruments. Intertest repeatability was better for the L80 videokeratographer compared to the B & L keratometer and showed no significant difference between the two sessions. Conclusion: The L80 videokeratographer is a reliable objective instrument comparable to other autokeratometers which, in addition, combines many other useful clinical features. It provides steeper radii of curvature measurements than the B & L keratometer. An offset incorporated into the instrument could mitigate the difference between the two instruments and make them interchangeable

Effect of ageing on keratoconic corneas

Purpose: To explore the potential effect of ageing on the corneal curvature and corrected visual acuity in patients with long-term keratoconus because of the paucity of these patients older than 50 years. Methods: Records of keratoconic patients, who had initially presented to a specialized contact lens clinic and followed for more than 20 years after disease onset, were reviewed. Collected information included age, gender, date of first and last examination, date of onset of the disease, central corneal curvature, refraction, best corrected visual acuity (BCVA), therapeutic modality and clinical signs. Results: Age of patients at last examination was 53.8 years ± 7.2 (range 44–67 years). Disease onset was self-reported to be at age 18.4 years ± 3.8. First examination was at age 25.1 years ± 9.4 and the mean number of years between first and last examination was 28.7 years. Mean central corneal curvature was 6.87 mm (48.77 D) ± 0.65 and 6.56 mm (51.09 D) ± 0.74, at first and last examination, respectively, a difference which was significant (p < 0.001). However, the last measurement of corneal curvature was found to remain approximately constant over the years from about 20 to 50 years after onset. Mean BCVA was not significantly different between first and last examination and was found to be approximately constant over the years. Conclusion: Corneal curvature became steeper possibly within the first 20 years after disease onset but remained approximately unchanged afterwards. Likewise, BCVA remained practically constant over the years indicating relative stability of the disease after 20 years

Bilateral chorioretinal coloboma discovered with ultra-wide field retinal imaging

Uveal coloboma results from incomplete closure of the optic cup fissure. While conducting an evaluation of a new ultra-wide field retinal imaging camera (Optomap), which provides a view of the fundus up to 200° at one time without mydriasis, we discovered a case of bilateral chorioretinal coloboma in a 21-year-old student. The lesion was located in the midperiphery of each eye less than 2 disc diameters (DD) below the optic disc in the inferonasal quadrants. The size of the coloboma in the right eye was 1.8 DD in height and 1.3 DD in width, while the left lesion was 2.4 DD in height and 2.6 DD in width. The subject was totally asymptomatic and without any complication such as retinal detachment or choroidal neovascularization, which often accompany this type of lesion. The visual field of each eye displayed an absolute scotoma corresponding to the size and location of the coloboma. No management was necessary but the subject was advised to report for visual examination at regular intervals because complications can occur at any age