Srinivas K. Rao

Effect of laser in situ keratomileusis on tear stability

OBJECTIVE Patients frequently experience dry eye symptoms after laser in situ keratomileusis (LASIK). The mechanisms that lead to these changes are not well understood. The purpose of this study was to investigate the effect of LASIK on tear function. DESIGN Prospective, comparative, nonrandomized interventional trial. PARTICIPANTS Fifty-eight consecutive patients (96 eyes) who underwent myopic LASIK treatment. METHODS The prospective study involved 58 consecutive patients (96 eyes) who underwent sequential or bilateral LASIK for the correction of myopia. Dry eye symptoms, standardized Schirmer test values, basal tear secretion test, and tear break-up time were measured before surgery and 1 day, 1 week, and 1 month after surgery. MAIN OUTCOME MEASURES Schirmer test value, basal tear secretion value, and tear break-up time. RESULTS Before surgery, 15.6% of patients (15/96) had dry eye symptoms. After surgery, 94.8% of patients (91/96), 85.4% of patients (82/96), and 59.4% of patients (57/96) experienced dry eye symptoms at 1 day, 1 week, and 1 month, respectively. Schirmer test value (13.32 +/- 10. 67 mm) increased at 1 day (14.48 +/- 10.57 mm; P = 0.25) and subsequently decreased at 1 week (11.18 +/- 9.81 mm; P = 0.05) and at 1 month (10.83 +/- 10.02 mm; P = 0.03). Basal tear secretion test value (8.49 +/- 8.48 mm) decreased at 1 day (6.80 +/- 6.48 mm; P = 0.05), at 1 week (5.97 +/- 6.88 mm; P = 0.005), and at 1 month (5.89 +/- 6.24 mm; P = 0.007). Tear break-up time (5.32 +/- 2.35 seconds) decreased 1 day (4.14 +/- 1.90 seconds; P < 0.001) and 1 week (4.49 +/- 1.70 seconds; P = 0.004) after surgery and recovered by 1 month after surgery (5.09 +/- 3.03 seconds; P = 0.52). Poor preoperative tear functions with a Schirmer test value less than 10 mm was a significant risk factor (72% vs. 46%; relative risk, 1.58 [1.10-2.26]) for experiencing dry eye symptoms at 1 month after surgery. CONCLUSIONS Dry eye symptoms are common after myopic LASIK surgery. Laser in situ keratomileusis significantly altered the tear break-up time, Schirmer test values, and basal tear secretion. Patients with preexisting tear flow abnormality as demonstrated by Schirmer test values less than 10 mm are especially at risk of experiencing dry eye symptoms.

Central corneal thickness measurements using Orbscan II, Visante, ultrasound, and Pentacam pachymetry after laser in situ keratomileusis for myopia

PURPOSE: To compare corneal pachymetry assessment using 4 measurement methods in eyes after laser in situ keratomileusis (LASIK) for myopia. SETTING: Department of Ophthalmology & Visual Sciences, The Chinese University of Hong Kong, Hong Kong Eye Hospital, Hong Kong SAR. METHODS: Fifty‐two consecutive patients (103 eyes) who had LASIK for the correction of myopia had Orbscan II (Bausch & Lomb), Visante (Carl Zeiss Meditec), Pentacam (Oculus, Inc.), and ultrasound (US) pachymetry (Sonomed, 200P) 6 months after surgery. Data were analyzed using the paired sample t test, Bland‐Altman plots, and linear regression. RESULTS: The mean postoperative pachymetry measured by US, Orbscan (0.89 acoustic factor), Pentacam, and Visante pachymetry were 438.2 μm ± 41.18 (SD), 435.17 ± 49.63 μm, 430.66 ± 40.23 μm, and 426.56 ± 41.6 μm, respectively. Compared with the US measurement, Pentacam and Visante measurements significantly underestimated corneal thickness by a mean of 7.54 ± 15.06 μm (P<.01) and 11.64 ± 12.87 μm (P<.01), respectively. There was no statistically significant difference between US and Orbscan measurements. CONCLUSION: Pentacam and Visante measurements of corneal thickness 6 months after LASIK were significantly less than those obtained using Orbscan and US pachymetry, although all 4 measurement methods showed a high correlation with each other.

Descemet Stripping Endothelial Keratoplasty: Effect of the Surgical Procedure on Corneal Optics

PURPOSE To determine the changes in corneal optical performance after posterior lamellar corneal transplantation. DESIGN Retrospective case series. METHODS The anterior segment in four eyes of four patients who underwent Descemet stripping endothelial keratoplasty (DSEK) with cataract extraction and intraocular lens (IOL) implantation were imaged with the Visante anterior segment optical coherence tomography [OCT] (Carl Zeiss Meditec, Dublin, California, USA). The curvature of the posterior surface of the donor graft was compared with that of the host cornea, and corneal thickness was measured. RESULTS All eyes had a hyperopic refractive error after surgery. The posterior corneal curvature after surgery was more than that before surgery. Average preoperative keratometry was 43.4 diopters (D), and after surgery, it was 42.8 D using keratometry. However, when the postsurgical corneal power was calculated using the Gaussian optics method, the average value was 40.8 D. CONCLUSIONS The addition of a donor corneal graft to the posterior surface of decompensated corneas may lessen the effective optical power of the cornea and may have implications for IOL power calculations in these eyes.

Topical atropine in retarding myopic progression and axial length growth in children with moderate to severe myopia: a pilot study.

PurposeTo study the safety and efficacy of topical 1% atropine eye ointment in retarding myopic progression in children with moderate to severe myopia.MethodsThis was an interventional control study. Children (aged 5–10 years) with myopia of −3.00 diopters (D) or more were treated with 1% atropine ointment once daily for 1 year. Baseline and regular assessments of refractive errors by cycloplegic autorefraction and of axial length were done by ultrasound biometry, and the results were compared with data of control subjects.ResultsTwenty-three children (mean age: 7.4 ± 1.6 years) with moderate to severe myopia, being treated in the Hong Kong Eye Hospital of the Chinese University of Hong Kong, were recruited into the atropine group, and 23 children from the same eye clinic were matched with the study subjects with respect to age, sex, and initial spherical equivalent refraction, as controls. The initial refractive errors were −5.18 ± 2.05 D and −5.12 ± 2.33 D in the atropine and the control groups, respectively (P = 0.934). Myopic progression was significantly less (P = 0.005) in the atropine group (+0.06 ± 0.79 D) than in the control group (−1.19 ± 2.48 D). Axial length increase was also significantly smaller in the atropine group (0.09 ± 0.19 mm) than in the control group (0.70 ± 0.63 mm) (P = 0.004). One child (4.3%) developed an allergic reaction. No other major adverse effects related to the treatment were noted.ConclusionTopical 1% atropine ointment is a safe and effective treatment for retarding myopic progression in moderate to severe myopia. Further large-scale randomised controlled study with longer follow-up seems warranted. Jpn J Ophthalmol 2007;51:27–33

Current status of limbal conjunctival autograft.

The past decade has witnessed several major advances in the field of ocular surface reconstruction. It is now established that the limbal and corneal epithelia belong to the same clonogenic lineage and that conjunctival transdifferentiation does not occur. These facts have engendered the increasing use of limbal transplantation in several ocular conditions involving limbal compromise. Many reports on this procedure have been published in the past year. They add to the growing body of evidence that limbal transplantation is efficacious in replenishing the stem cell pool, promoting improved vision and enhancing ocular comfort. Recent clinical studies on limbal autograft transplantation also underscore the importance of preoperative impression cytology in donor eyes, highlight the fact that transplantation in inflamed eyes is to be avoided, and indicate that the procedure is likely to provide better outcomes if performed several months after ocular surface burns. The appreciation of the utility of amniotic membrane transplantation in ocular surface reconstruction has provided a surgical tool to use in tandem with limbal transplantation. Questions such as why limbal autografts fail, the long-term results of LAT, and whether limbal inclusion is mandatory during conjunctival transplantation after pterygium excision have not been answered fully. Studies on long-term outcomes with limbal allograft transplantation and those reporting on experience with newer techniques such as epithelial transplantation using tissue culture-cultivated epithelium are likely to provide better perspectives on the best way to reconstruct the ocular surface in stem cell-deficient eyes.

Pathogenesis and management of laser in situ keratomileusis flap buttonhole

PURPOSE To describe the clinical features and outcomes in patients who had a flap buttonhole during laser in situ keratomileusis (LASIK) and propose an etiopathogenic mechanism for this complication. SETTING University Eye Center, Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China. METHODS Retrospective review of case records of 6 patients (6 eyes) who had a flap buttonhole during LASIK. RESULTS The mean patient age was 38.2 years +/- 4.1 (SD) and the mean preoperative spherical equivalent (SE) refraction, -8.13 +/- 4.04 diopters (D). Mean keratometry was 44.20 +/- 1.30 D. Retreatment was performed after a mean interval of 9.2 +/- 3.2 months. Final postoperative SE refraction was -0.44 +/- 0.58 D after a mean follow-up of 59.0 +/- 5.3 weeks. No patient experienced loss of best spectacle-corrected visual acuity. CONCLUSIONS Retreatment of eyes that have a flap buttonhole during LASIK is associated with good visual outcomes. Flap buttonholes can produce alterations in refraction, so retreatment is best performed after the refractive error has stabilized. Microkeratome malfunction may be responsible for the occurrence of a flap buttonhole during LASIK in eyes that do not have significant corneal steepening.

Combined intravenous pulse methylprednisolone and oral cyclosporine A in the treatment of corneal graft rejection: 5-year experience.

Purpose To report the mid-term results of a treatment strategy using topical steroids, intravenous pulse methyl prednisolone and oral cyclosporine A (CSA) for the treatment of acute corneal graft rejection.Methods Noncomparative, interventional case series. Treatment of corneal graft rejection included 1% prednisolone eye drops, intravenous infusion of 500 mg methyl prednisolone, and oral CSA in two regimens—standard dose was 15 mg/kg/day for 2 days, 7.5 mg/kg/day for 2 days, then adjusted to maintain trough blood levels of 100–200 μg/l; low dose was 2 mg/kg/day with no loading dose.Results Outcome in 34 eyes of 34 patients (21 M;13 F) aged 60 ± 17.7 years (range 9–83 years), who presented after an average duration of 6.6 ± 6.3 days (range 0–30 days) following acute corneal graft rejection, are reported. Twenty-five patients received standard dose CSA while nine patients received the low dose regimen. Mean duration of treatment before reversal of graft rejection was 13.6 ± 12.1 days (range 3–54 days). Treatment was successful in reversing the graft rejection in 32/34 (94%) eyes. Irreversible graft failure occurred in one eye in each group. During a mean follow-up period of 19.2 ± 16.7 months (range 1–55 months), further episodes of graft rejection were seen in 1/32 (3%) eyes. Complications due to treatment included: duodenal ulcer in one patient that responded to medical treatment, and transient elevation in serum creatinine levels in three patients, which returned to normal after decrease in dosage or cessation of oral CSA.Conclusion Our 5-year experience with the use of oral CSA in the treatment of acute corneal graft rejection has shown this treatment approach to be safe and effective in reversing the rejection process. This approach may also protect the graft from subsequent episodes of allograft rejection. A randomised controlled trial to further delineate the role of CSA in reversing acute graft rejection seems warranted.

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.

Macular pigment optical density in a Chinese sample.

Purpose: Extensive efforts have been devoted to determining the macular pigment optical density (MPOD) in Caucasian subjects. Unfortunately, no such data in ethnic groups with naturally dark irises are currently available. In this study, we report the values in a sample of Chinese subjects. Methods: The MPOD was measured psychophysically using a densitometer at 0.25°, 0.50°, 1.00°, and 2.00° eccentricity from the foveal center in 92 Chinese subjects. Results: The spatial profile for the averaged MPOD was approximately exponential in form and showed a decline with age (r = −0.23). Subjects aged below 60 years had significantly higher averaged MPOD than those aged 60 years or above. Significant gender differences, in favor of males, were also found in the middle-age groups. Conclusions: Our study reports for the first time the MPOD in a Chinese population. Baseline information on MPOD would aid future research in preventive measures against age-related macular degeneration.

Changes in refraction and ocular dimensions after cataract surgery and primary intraocular lens implantation in infants

PURPOSE: To study refraction and axial length changes after cataract extraction and primary intraocular lens (IOL) implantation in children younger than 1 year of age. SETTING: Two regional hospitals. METHODS: After determining the IOL power for emmetropia, 80% of the value was used to choose the IOL for implantation to counter anticipated myopic shift with age. The main outcome measures were changes in refraction and axial length 3 years after surgery. RESULTS: Thirty‐four eyes of 20 children (mean age 6.7 months ± 3.9 [SD]) were studied. Refraction in the immediate postoperative period was +4.53 ± 1.45 diopters (D). Three years after surgery, the mean refraction was −2.49 ± 3.08 D (P<.001). Twenty‐two eyes (64.7%) had surgery during the first 6 months of life (group 1) and had a shorter axial length at surgery (mean 18.92 ± 1.32 mm) compared with 12 eyes (35.3%) that received surgery between 7 and 12 months (group 2, mean 20.29 ± 1.00 mm) (P = .007). However, the final axial length was greater in group 1 (mean 22.67 ± 1.04 mm) than in group 2 (mean 21.23 ± 0.26 mm) (P = .019). CONCLUSIONS: Primary IOL implantation is an option for children having cataract surgery in the first year of life. Significant myopic shifts occurred, and this seemed to be more pronounced in younger children. It appears that rethinking current strategies for IOL power calculation may be required to achieve more optimal refractive outcomes.