BACKGROUNDCorneal curvatures measured by conventional instruments after refractive surgeries were greater than the real values. This study on the instruments and methods for measuring corneal curvature was carried out with the aim of determining an accurate, simple and effective method to evaluate corneal refractive power after radial keratotomy (RK).

METHODSA retrospective study was carried out on 52 eyes of 42 patients with a history of RK. The postoperative measurements after RK were performed with a manual keratometer (Rodenstock, Munchen-Hamburg, Germany), a corneal topographer (Tomey TMS-1) and an automated IOLMaster keratometer (Carl Zeiss GmbH, USA). The results obtained from analyzing clinical histories (clinical history method, CHM) were compared to the postoperative measurements with a two-way analysis of variance. Adjusted keratometry was used to correct the corneal central refractive power (K) values of the three keratometers. The CHM results were also compared to the corrected K values obtained with the three keratometers using the same statistical method.

RESULTSThe smallest mean value was found for the CHM ((36.61 ± 2.23) diopters). The K values obtained with the CHM were very different from the results obtained with the three different instruments. The corrected K values obtained with the IOLMaster were the closest to the K values from the CHM.

CONCLUSIONSIt was shown that K values from measurements with the three instruments were higher. When the power of the intraocular lens of the patients after RK was calculated, the errors of the K values measured with the instruments should be taken into consideration.

Adult ; Cornea ; anatomy & histology ; Corneal Topography ; Female ; Humans ; Keratotomy, Radial ; Male ; Retrospective Studies

This experimental study sought to determine the repeatability of a Video Keratography System specially designed for animals with small eyes. From day 5, ten newly hatched White Leghorn chicks were reared with monocular hyperopic defocus using -5.0D (n = 3), -10.0D (n = 3), -15.0D(n = 4) spherical PMMA lenses on their right eyes; the left eyes served as controls. Two sets of corneal topographical measurements, each set separated by about 5 minutes apart, were collected from both eyes of each animal at the end of 2-wk treatment period (i. e., 19 days of age). Each set of measurements consisted of five consecutive readings of corneal astigmatism. Bland-Altman plots were used to evaluate the repeatability of 3, 4 or all 5 readings from each set of data. When all 5 consecutive readings were used, the mean difference (95% limits of agreement) for the right treated and left untreated eyes were, respectively, -0.09D (-0.81, 0.64) and -0.02D (-0.86, 0.82). There was a tendency that lesser readings from each set of data produced greater difference between the two sets of measurements, although the differences (-0.19D) were not clinically significant. The Video Keratography System specially designed for animals with small eyes produced repeatable measurements for both treated and untreated eyes in chickens. Further studies are needed to validate other biometric features associated with corneal changes during normal and abnormal eye growth.
Animals ; Astigmatism ; diagnosis ; Chickens ; Cornea ; anatomy & histology ; Corneal Topography ; instrumentation ; Equipment Design

The central corneal thickness (CCT) in age 48 years or less of Chinese was characterized and its relationship with gender, age, refraction and intraocular pressure (IOP) was investigated. Right eyes of 1669 participants were included in this study (880 men, 52.7% and 789 women, 47.3%). Mean age of the samples was 23.8 +/- 5.9 years. After the examination of corneal topography and refraction, Goldman applanation tonometry was carried out by one physician. Tonometric values were the mean of three consecutive readings. Subsequently, another physician carried out ultrasonic pachymetry with the DGH 2000 AP ultrasonic pachymeter. Six measurements were made at the center of the cornea of each eye. The mean value was used for analysis. The results showed that mean CCT of male participants was 551.33 +/- 34.62 microm, 5.79 microm more than that of female participants. Linear regression analyses revealed that CCT was negatively related with age only in female and no association was found between refractive status and CCT. IOP was positively related to CCT, and there was a difference in IOP of 1.5 mmHg (1 mmHg = 0.133 kPa) per 100 microm difference in CCT. Ocular hypertension group was prone to have thicker cornea than average. The results indicated that in adult Chinese CCT tended to decrease with aging in female only. IOP measured by Goldmann tonometry was positively related with CCT so that CCT should be measured along with IOP.
Age Factors ; China ; Cornea/*anatomy & histology ; Corneal Topography ; Intraocular Pressure ; Reference Values ; Sex Factors ; Tonometry, Ocular

PURPOSE: To evaluate reliability of Fourier-domain optical coherence tomography (OCT) (RTVue), time-domain OCT (Visante), and slit-lamp adapted ultrasonic pachymetry (SL-US) in the measurement of central corneal thickness (CCT). MATERIALS AND METHODS: Thirty healthy volunteers visited our clinic 3 times and fifty eyes were measured by one physician. RTVue and Visante were randomly performed, and then SL-US, in which the ultrasound probe was inserted into the Goldmann tonometry mount, was done. During the second visit, each measurement was repeated 3 times. Measurements on the second visit were averaged, and agreement among the instruments was investigated with Bland-Altman plots. RESULTS: RTVue showed smaller repeatability coefficient than Visante and SL-US (4.7, 8.3, and 7.7 microm, respectively). Intersession reproducibility of RTVue and Visante was worse than their repeatability. CCT of RTVue was estimated to be maximally different by 11.8 microm from CCT of Visante and 8.8 microm from CCT of SL-US. The repeatability coefficient of SL-US was 7.7 microm and its reproducibility was similar to the repeatability. CONCLUSION: CCT measured by RTVue showed good reliability and generally agreed with Visante and SL-US. SL-US was as reliable as triple touching conventional US even with a single touch on the cornea.
Adult ; Cornea/*anatomy & histology/pathology/ultrasonography ; Corneal Topography ; Female ; Humans ; Male ; Reproducibility of Results ; Tomography, Optical Coherence/*methods

The excimer laser diopter correction has proven to be efficient and safe. This paper presents the principle of excimer laser refractive surgery. Based on analyzing the mathematics model of the human eye cornea, the authors have proposed a new model which can be used to proceed the myopia, hyperopia, astigmatism diopter correction. Also studied were the excimer laser's ablation mechanism and the flying-spot scanning technology. The research results have been directly applied to Ophthalmic excimer laser system. The correction of diopter is well improved.
Algorithms ; Cornea ; anatomy & histology ; Humans ; Keratomileusis, Laser In Situ ; methods ; Lasers, Excimer ; Models, Theoretical ; Photorefractive Keratectomy ; methods ; Refractive Surgical Procedures

It is very difficult to measure the human eye properties directly, such as the accommodation mechanism, intraocular pressure distribution, the dynamics of aqueous humor flow and the bio-heat transfer in human eyes. Modeling and simulation may, therefore, play an increasingly important role in the ophthalmologic investigation. The major computer modeling methods, including geometric modeling, physical modeling and mathematical modeling, are introduced in this paper. Modeling and simulation anatomy properties and physiological properties of eye tissues, such as the cornea, aqueous humor and crystalline lens, vitreous, optic nerve head, sclera, are analyzed in the order from global to local, from front to back, from outside to inside. Finally, the problems of computer modeling in ophthalmologic investigation are discussed, and the development trends of the future are pointed out.
Aqueous Humor ; physiology ; Computer Simulation ; Cornea ; physiology ; Eye ; anatomy & histology ; Humans ; Lens, Crystalline ; physiology ; Ophthalmology ; trends ; Sclera ; physiology

BACKGROUNDMeasurement of anterior segment parameters plays an important role in diagnosis and treatment of glaucoma. The objective of this study was to evaluate the repeatability and reproducibility of anterior chamber volume (ACV) measurements with rotating scheimpflug camera (RSC) and to examine agreement with anterior segment optical coherence tomography (AS-OCT).

METHODSThirty nine healthy normal subjects were recruited from the Eye Center of Tongren Hospital. ACV was measured using RSC and AS-OCT in a randomly selected eye for each subject. For RSC measurements, both automatic and manual ACV measurements and 2 independent operators' ACV measurements were obtained. All subjects were invited for 3 visits within a week to evaluate repeatability and reproducibility of ACV measurement by RSC. Agreement was evaluated between RSC and AS-OCT.

RESULTSGood repeatability and reproducibility were found for both automatic and manual ACV measurements obtained by RSC. For intrasession repeatability, coefficient of variation (CVw) and intraclass correlation coefficient (ICC) values for automatic were 3.52% and 0.98; the values for manual were 3.44% and 0.97, respectively. For intersession reproducibility, the respective CVw and ICC values were 3.96% and 0.96. Good agreement was also found in 2 operators for both automatic and manual ACV measurements; nevertheless, poor agreement was found between RSC and AS-OCT (95% confidence interval (CI) for agreement of automatic RSC measurement versus AS-OCT were -96.3 to 72.8 microl and 95% CI for agreement of manual RSC measurement versus AS-OCT were between -41.7 to 10.1 microl).

CONCLUSIONSBoth RSC automatic and manual ACV measurements showed good repeatability and reproducibility, and showed comparable agreement between 2 independent operators, but poor agreement was found between RSC and AS-OCT.

Adult ; Anterior Chamber ; anatomy & histology ; Anterior Eye Segment ; anatomy & histology ; Cornea ; anatomy & histology ; Diagnostic Techniques, Ophthalmological ; instrumentation ; Female ; Glaucoma ; diagnosis ; Humans ; Male ; Reproducibility of Results ; Tomography, Optical Coherence ; methods ; Young Adult

We report two cases of band keratopathy who were treated with thick amniotic membrane that contained a basement membrane structure as a graft, after ethylenediaminetetraacetic acid chelation with trephination and blunt superficial lamellar keratectomy in the anterior stroma. In each case, basement membrane was destroyed and calcium plaque invaded into anterior stroma beneath Bowman's membrane. The calcified lesions were removed surgically, resulting in a smooth ocular surface, and the fine structures of band keratopathy were confirmed by pathologic findings. After that, amniotic membrane transplantation was performed to replace the excised epithelium and stroma. Wound healing was completed within 10 days. Stable ocular surface was restored without pain or inflammation. During the mean follow-up period of 13.5 months, no recurrence of band keratopathy was observed. This combined treatment is a safe and effective method for the removal of deep-situated calcium plaque and allowing the recovery of a stable ocular surface.
Amnion/*anatomy & histology/*transplantation ; Calcium/metabolism ; Chelating Agents/*therapeutic use ; Cornea/pathology/surgery ; Corneal Diseases/*drug therapy/pathology/*surgery ; Edetic Acid/*therapeutic use ; Female ; Humans ; Male ; Middle Aged