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Arthur C K Cheng

Publications and source records attributed to Arthur C K Cheng.

At least 19 recordsLinked to original sources
PubMed2006

Assessment of pupil size under different light intensities using the Procyon pupillometer.

PURPOSE: To study the relationship between pupil size and light intensity using the Procyon pupillometer. SETTING: University based clinic. METHODS: In this retrospective study, 20 consecutive patients had pupil size assessment with the Procyon pupillometer under 3 different light conditions--4, 0.4, and 0.04 lux. Correlation was established using the log unit of the light intensity and pupil size. RESULTS: The correlation coefficient for the association between pupil size and log unit of light intensity in all eyes was significant (P<.001). The mean correlation coefficient for the association between pupil size and log unit of light intensity in all patients was 0.968 +/- 0.089 (SD) in the right eye and 0.970 +/- 0.031 in the left eye. CONCLUSION: The linear relationship between the pupil size and the log unit of the light intensity showed a tight correlation in all cases. These results can be useful in the comparing pupil size with pupillometers that work under different light conditions.

Adult↗
PubMed2006

Effect of corneal curvature and corneal thickness on the assessment of intraocular pressure using noncontact tonometry in patients after myopic LASIK surgery.

PURPOSE: To evaluate the effect of corneal curvature and corneal thickness on the assessment of intraocular pressure (IOP) using noncontact tonometry (NCT) in patients after myopic LASIK surgery. METHODS: All patients who had myopic LASIK in a university-based eye clinic between February 2002 and May 2002 were retrospectively analyzed. Preoperative NCT was compared with postoperative NCT, postoperative corneal thickness, and postoperative corneal curvature. RESULTS: The difference between the mean preoperative NCT (15.46 +/- 2.50 mm Hg) and postoperative NCT (6.30 +/- 1.57 mm Hg) was significant (9.16 +/- 1.96 mm Hg, P < 0.010). Preoperative NCT significantly correlated with postoperative NCT (P < 0.001), postoperative corneal thickness (P = 0.006), and postoperative anterior corneal curvature (P < 0.010). CONCLUSIONS: Both corneal thickness and anterior corneal curvature affect IOP assessment in patients with myopic LASIK. Although correction formulas can be used to estimate the actual IOP, alternative methods should be investigated to assess IOP independent of corneal thickness and curvature.

Adult↗
PubMed2006

The effects of eye drops on corneal thickness in adult myopia.

PURPOSE: To study the effects of Complex Tropicamide (0.5% Tropicamide and 0.5% phenylephrine HCI) and Saline solution on corneal thickness in adult myopic patients with the Orbscan II system. SETTING: Department of Ophthalmology, Yantai Yuhuangding Hospital. DESIGN: Prospective, nonrandomized, clinical trial. METHODS: The thinnest pachymetry of the cornea was obtained before and 1.5 hours after administration of three drops of Complex Tropicamide to the left eyes of 58 patients (58 eyes) and Saline solution to their 31 right eyes, respectively. The corneal thickness of the other 27 right eyes before and 1.5 hours after eyelid closure without exposure to eye drops was used as the control group. RESULTS: The thinnest pachymetry of the cornea was significantly higher after exposure to eye drops in the Tropicamide group (23.36 +/- 15.01 microm; t = -11.855, P < 0.001). Similar findings were also noted in the Saline group (7.13 +/- 8.11 microm, t = -4.894, P < 0.001). The difference between the two groups was also significant (t = 6.737, P < 0.001). There were no statistically changes in corneal thickness in control group. The drops tested have no effect on the location of the thinnest corneal site and its distance form the visual axis. CONCLUSION: Eye drops including Saline solutions may have significant effects on the corneal thickness in myopia, and this may have implications for corneal refractive surgery.

Adult↗
PubMed2006

Prospective randomized double-masked trial to evaluate perioperative pain profile in different stages of simultaneous bilateral LASIK.

PURPOSE: To evaluate the perioperative pain profile in simultaneous bilateral LASIK. METHODS: Fifty consecutive Chinese patients undergoing simultaneous bilateral LASIK were randomly allocated to have either the right or left eye operated first. The pain scores for each eye at speculum placement, microkeratome cut, laser ablation, and at 15, 30, and 45 minutes after the procedure were recorded. In addition, an overall score for the whole operation was evaluated immediately after the procedure for each eye. Comparisons between eyes and among different stages of the procedures were analyzed. RESULTS: The second eye was significantly more painful than the first eye at the stage of speculum placement and microkeratome pass (P < 0.001). Laser ablation was the least painful stage for both eyes. There were no statistical differences in pain scores for the postoperative period. CONCLUSION: Higher pain scores were associated with the stages involving eyelid manipulation. In patients with small palpebral fissures where stretching of the eyelid structures are anticipated, supplementary anesthesia for the lid region should be considered when required.

Adult↗
PubMed2006

Correction factor in Orbscan II in the assessment of corneal pachymetry.

PURPOSE: Comparison of corneal pachymetry assessment with ultrasound and Orbscan II using acoustic factor and subtraction methods. METHODS: Ultrasound and Orbscan pachymetry for all patients with LASIK performed between July 2002 and May 2003 were retrospectively analyzed. Comparison between the 2 preoperative measurements was analyzed. RESULTS: Using a custom acoustic factor of 0.93, there was no significant difference between the overall ultrasound and Orbscan pachymetry (P = 0.696). However, there was underestimation in thick corneas and overestimation in thin corneas. Using the subtraction method as the correcting technique, the magnitude of over- and underestimation was reduced. CONCLUSION: The current correction method by means of acoustic factor may result in error in assessing extremes of corneal thickness. Alternative approaches such as the subtraction method can be considered to achieve more accurate results.

Adult↗
PubMed2006

Pachymetry assessment with Orbscan II in postoperative patients with myopic LASIK.

PURPOSE: To compare central corneal thickness after LASIK for myopia, using ultrasonic pachymetry and Orbscan II measurements, and to evaluate changes in these measurements over time. METHODS: Central corneal thickness measurements obtained by ultrasonic pachymetry and Orbscan II (Bausch and Lomb, Rochester, NY) in patients who underwent myopic LASIK between July 2002 and May 2003 were analyzed. The two measurements were assessed preoperatively and postoperatively at 1 day and 1, 3, 6, and 12 months. RESULTS: In 237 eyes, using the correction factor 0.93, no significant difference was noted in the preoperative central corneal thickness measured by ultrasonic pachymetry (561.89 +/- 28.66 microm) and Orbscan pachymetry (562.28 +/- 28.18 microm) (P =.713). Postoperatively, the difference was statistically significant at day 1 and 1, 3, and 6 months (P < .001), but was not significant at 12 months (P = .130). CONCLUSIONS: Orbscan II measurements of central corneal thickness after myopic LASIK are less than those measured by ultrasonic pachymetry; however, this difference decreases with time and may not be significant after 1 year.

Adult↗
PubMed2006

Late traumatic flap dislocations after LASIK.

PURPOSE: To report the management and outcome of late onset traumatic dislocation of LASIK flaps. METHODS: This retrospective, interventional case series presents three patients with late onset LASIK flap dislocation following mechanical trauma 1 to 7 years postoperatively. RESULTS: In all cases, the flap was surgically repositioned. Epithelial ingrowth was removed and diffuse lamellar keratitis was treated with an intensive steroid regimen. All patients returned to their preoperative best spectacle-corrected visual acuity. Aggressive steroid treatment during the perioperative period and meticulous handling of the epithelium are important in preventing further recurrence. CONCLUSIONS: Laser in situ keratomileusis flaps may experience mechanical dislocation as late as 7 years postoperatively. Diffuse lamellar keratitis and epithelial ingrowth are associated with flap dislodgment.

Administration, Topical↗