Quality of life assessment before and after laser in situ keratomileusis.

Objective: To assess the health-related quality of life in patients who underwent conventional laser in situ keratomileusis (LASIK). Methods: Eighty-five patients who underwent LASIK at the Excimer Unit at Siriraj Hospital were enrolled in the study. They were asked to complete a quality of life questionnaire before and after having an operation at 1, 3 and 6 months. The details of the questionnaire were published elsewhere. The questionnaire included 19 items in four categories and one independent item. Paired t-test, non parametric test and repeated measures were performed to compare pre- and post-operation results. Results: Of the total, there were 51 females (58.6%). Patients’ ages ranged from 16-50 years, with a mean age of 30.7 ± 8.7 (years ± SD). Cronbach’ alpha coefficients of the questionnaire were 0.74-0.81. In one-month (n=67), three-month (n=42) and 6-month (n=14) follow-ups, patients tended to score better on visual tasks and had a significantly better score satisfaction and emotional feeling domain. However, their score on the eye symptoms domain was worse after one month and got better after three months. In general, patients were satisfied with the results of the operation on follow-ups. Conclusion: The quality of life for patients undergoing LASIK has improved. Patients have better uncorrected vision, with more satisfaction and emotional feeling. Although they have more eye symptoms resulting from the operation, they were very satisfied with the results.

Correlation factors for posterior corneal curvature after myopic LASIK.

Objective: To evaluate the correlation factors for posterior corneal curvature after myopic LASIK. Methods: The retrospective study of 92 eyes which underwent myopic LASIK was conducted. All LASIK procedures were done using Hansatome ® Microkeratome and Tecnolas ® 217 excimer laser (B&L, USA). Pre- and post-operative data were collected including refraction, corneal thickness, anterior and posterior corneal curvature measured by Orbscan ® Corneal Topography. Statistical analysis was done to evaluate the posterior corneal curvature related to other factors. Results: The posterior corneal curvature after myopic LASIK showed low to moderate correlation to the amount of myopia treated (R2 = 0.286), anterior corneal curvature (R2 = 0.37) and corneal thickness (R2 = 0.37 for measured corneal thickness and R2 = 0.40 for calculated corneal thickness which is calculated by subtracting ablation depth from pre-operative thickness) (all p value < 0.05). Conclusion: The posterior corneal curvature after myopic LASIK can be partially correlated with corneal thickness, anterior corneal curvature and the amount of myopia treated.

Performance of conventional biometry vs. integrated laser interferometry with keratometry device in intraocular lens measurement.

OBJECTIVE: To compare the performance of the Conventional Biometry (CB) (Applanation Ultrasound and Keratometry) and the Integrated Laser Interferometry with Keratometry Device (LI) in the measurement of Intraocular Lens (IOL). MATERIAL AND METHOD: A prospective study of 100 eyes in 50 cataract patients was conducted. The IOL measurement using the LIfollowed by the CB was done on all eyes. The keratometry (K), axial length (AL), IOL power, and time required for both methods were compared in the same subject by ANOVA with repeated measurement. RESULTS: The LI could not obtain the AL in 14%. There were 21% that the signal to noise ratio was below 1.6. The AL obtained by the LI was significant higher compared to the CB by mean of 0.28 mm (p < 0.05). The K showed no statistically significant difference (p = 0.05). There was statistically significantly higher IOL power calculated by the LI compared to the CB by mean of 0.63 D (p < 0.05). The time required for the LI was 2.77 +/- 1.44 min and the CB was 9.63 +/- 3.82 min (p < 0. 05). CONCLUSION: The LI required less time than the CB in measurement of the IOL but could not measure the AL in the group of patients with dense cataracts. The LI give a higher IOL power compared to the CB.

Unfocused effect on the measurement of ocular aberrations.

OBJECTIVES: To evaluate the effect of unfocused measurement in the value of ocular aberrations. MATERIAL AND METHOD: The present study was conducted at Siriraj Hospital, Mahidol University. Ocular aberrations of 20 eyes in 10 myopic patients (myopia less than -6.00 diopters (D) and astigmatism less than -2.00 diopters (D)) were analyzed by using Zywave aberrometer (Bausch and Lomb, USA). The measurements were done at the pupillary plane (focus) and 6 other different planes (unfocus); 5, 10 and 15 mm inside and outside pupillary plane respectively. The value of each measurement was analyzed to find the effect of unfocused measurement on ocular aberrations. RESULTS: The magnitude of error (root mean square, RMS) of the spherical component of refraction at 5, 10, 15 mm inside and outside the pupillary plane was 0.16, 0.44, 0.57 D and 0.21, 0.38, 1.35D respectively. The RMS of astigmatic component of refraction inside and outside the pupillary plane at the same distance was 0.19, 0.50, 0.80 and 0.18, 0.52, 1.55 D respectively. The RMS of higher order aberrations inside and outside the pupillary plane at the same distance was 0.05, 0.13, 0.15 and 0.06, 0.1, 0.1 microns respectively. CONCLUSION: There was more effect of outward unfocused measurement in the value of refraction (spherical and astigmatism) than inward unfocused measurement. Higher order aberration showed a similar error in both inward and outward defocus. The magnitude of error was 10 - 12% within 5 mm unfocused planes.

Corneal characteristics in myopic patients.

OBJECTIVES: To evaluate the characteristics of the cornea in myopic patients. MATERIAL AND METHOD: A retrospective study of 420 eyes in 210 patients who visited the Excimer Laser Surgery Clinic at Siriraj Hospital, Mahidol University from January 1999 to June 2002 was conducted. All cases that were eligible for myopic refractive surgery were included in the present study. A preoperative ocular examination was done in a fashionable method, including manifest refraction and Orbscan Topography to evaluate corneal thickness, corneal curvature and corneal diameter Statistical analysis was performed to identify the characteristics of the cornea in the patients. RESULTS: The mean age of the patients was 31.66 +/- 7.77 years. (ranging from 16-51). The mean manifest refraction (spherical equivalent) was -4.9 +/- 2.29 diopters (ranging from -0.50 to -13.75). The mean corneal diameter (white to white) was 11.60 mm +/- 0.37 mm (ranging from 10.8-12.9). The thinnest point of the cornea varied from 409 to 597 microns (mean = 522.55) and located mostly in the infero-temporal quadrant of the eye (23.69% in the right and 32.05% in the left). The mean curvature of the corneal was 44.6 +/- 13.8 diopters (ranging from 39.05-47.65). The mean corneal astigmatism was 1.34 +/- 0.71 diopters and 93.96% were with the rule astigmatism. Positive angle kappa was found in 408 eyes (97%) but all cases were within a 0.5 mm horizontal and 0.3 mm vertical radius from the pupillary axis. CONCLUSION: Characteristics of the cornea in Thai myopic patients were demonstrated in the present study. Most of the cornea showed with the rule astigmatism with positive angle kappa and the thinnest point, located at the infero-temporal quadrant.

Tonometry after laser in situ keratomileusis treatment: a preliminary study in Thai patients.

OBJECTIVE: To evaluate the change in intraocular pressure (IOP) measurement by Goldmann applanation tonometer after Laser in Situ Keratomileusis (LASIK) for myopia and myopic astigmatism, and to assess the correlation between the changes of lOP reading and the reduction of central corneal thickness (CCT) after LASIK in Thai patients. STUDY DESIGN: Prospective correlational study. MATERIAL AND METHOD: LASIK was performed on 65 eyes of 33 patients for correction of myopia and myopic astigmatism. IOP was measured by Goldmann applanation tonometer before and 3 months after LASIK. The correlation between the change in IOP reading and the change in central corneal thickness were evaluated. RESULTS: IOP reading was significantly reduced by mean of 2.9 +/- 2.5 mmHg (p = 0.0001). The authors used Pearson analysis to study the correlation between the change in IOP and the reduction of CCT. In subgroup analysis the patients were divided by degree of myopia: group 1, myopia less than -3 diopters (D) (n = 14); group 2, myopia -3 to -6 D (n = 31); group 3, myopia greater than -6 D (n = 20)). The result showed more correlation in higher myopia group (Pearson; r = 0.158 in group 3, r = -0.098 in group 2 and r = -0.102 in group 1). CONCLUSION: Goldmann applanation tonometry underestimates the IOP in thin cornea. Variability in CCT is a potent confounder of this tonometry technique. Therefore, it has important implications for considering CCT measurement incorporated with Goldmann applanation tonometry for glaucoma diagnosis especially in myopic patients who undergo LASIK surgery.

Outcome of manifest refraction performed by first year residents evaluating the schematic eye.

Purpose: To evaluate the efficacy of manifest refraction performed by beginners (first year residents) Methods: Prospective study of manifest refraction obtained by first year residents at the Department of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University was done. The schematic eye (model BC 2174, Bernell Corporation 1995) was present to 7 types of refractive error, including simple hyperopia, simple hyperopic astigmatism, simple myopic astigmatism, compound hyperopic astigmatism, compound myopic astigmatism and mixed astigmatism. Blind manifest refraction was performed by all residents. The results were analyzed. Results: Eight residents with 56 manifest refraction were included. The overall mean error in the spherical equivalent was 0.26+0.99 diopter. The maximum error in the spherical component and spherical equivalent was found in the simple hyperopic astigmatism group (1.32+1.01 diopter and 1.34+0.63 diopter, respectively). The minimum error in the spherical component and spherical equivalent was found in the simple hyperopic group (0.12+0.37 diopter and 0.09+0.02 diopter, respectively). The maximum error in the cylinder was found in the mixed astigmatism group (0.84+0.59 diopter) but no error in the axis was found. The maximum error in the axis of the cylinder was also found in the simple hyperopic astigmatism group (13.75+17.06 degree). Conclusion: Manifest refraction performed by beginners is most likely to have an error in the simple hyperopic astigmatism. The axis cylindrical component is easiest to identity in mixed astigmatism but difficult to quantify in its amount. Refraction of these types of refractive error should be cautionary for the beginners.

Intraoperative perception and sensation in laser in situ keratomileusis (LASIK).

PURPOSE: To investigate intraoperative perception and sensation during Laser in situ Keratomileusis (LASIK). PATIENTS AND METHOD: Sixty patients with uneventful LASIK were included. All procedures were performed by one surgeon with one technique. Any patient with intra-operative complications was excluded. The patients were asked to fill in the subjective evaluation form regarding their perception and sensation during the operation. RESULTS: Twenty-nine patients (48%) reported no pain and twenty-six patients (43%) reported no burning sensation during the surgery. Nineteen patients (32%) reported no light perception during the suction period of microkeratome. There was no correlation between duration of the suction and no light perception (R2 0.01). Thirty-four patients (56%) reported no trouble in maintaining visual fixation at the red light during the laser treatment. Ten patients (16%) reported they could clearly see the movement during the surgery and 5 out of 10 patients (50% of 16%) reported visual frightening. Fifty cases (84%) reported no visual frightening during the surgery after reassurance of the visual experience by the surgeon before the surgery. CONCLUSIONS: Patients undergoing LASIK may experience different visual perceptions. Reassurance of the intraoperative perception and sensation before the surgery can reduce the visual frightening.

Comparison of topical lomefloxacin 0.3 per cent versus topical ciprofloxacin 0.3 per cent for the treatment of presumed bacterial corneal ulcers.

PURPOSE: To compare the efficacy and safety of topical lomefloxacin 0.3 per cent with topical ciprofloxacin 0.3 per cent for treating mildly severe suspected bacterial corneal ulcers. METHOD: This prospective, randomized, double-masked controlled clinical trial was conducted on 41 patients (41 eyes) with suspected bacterial corneal ulcers who were randomized into 2 groups: 23 patients were in the lomefloxacin group and 18 patients in the ciprofloxacin group. All of these corneal ulcers were scraped for gram's stain, KOH preparation and microbiologic cultures before starting treatment. The clinical success rate, the time to cure, the rates of treatment failures, ocular signs and symptoms and the adverse effects of the study medication were evaluated. RESULTS: Topical lomefloxacin is equivalent clinically and statistically to topical ciprofloxacin. No statistically significant treatment differences were found between lomefloxacin (100%) and ciprofloxacin (100%) in terms of success rate. Similarly, no differences were noted in the time to cure (p > 0.05), the treatment failure, or the resolution of the clinical signs and symptoms (p > 0.05). The adverse effects of lomefloxacin were superficial punctate keratitis (26.1%) and irritation (8.7%), whereas those of ciprofloxacin were superficial punctate keratitis (22.2%), white precipitate (11.1%) and irritation (11.1%). However, no statistically significant differences of these adverse effects were found between the two groups (p > 0.05). CONCLUSION: Lomefloxacin ophthalmic solution (0.3%) is equivalent clinically and statistically to ciprofloxacin ophthalmic solution (0.3%) for the treatment of mildly severe presumed bacterial corneal ulcers without statistically significant differences in the adverse effects and discomfort.

Internal astigmatism and its correlation to corneal and refractive astigmatism.

OBJECTIVE: To evaluate the internal astigmatism and its relationship to corneal and refractive astigmatism in a refractive surgery patient population. METHOD: Patients who underwent pre-operative evaluation for Laser in situ Keratomileusis (LASIK) at Excimer Laser Clinic, Siriraj Hospital, Mahidol University were included. Pre-operative data including age, manifest refraction and corneal topography obtained by Orbscan Corneal Topography were performed. Regression Analysis was done to find the correlation between refractive and corneal astigmatism. RESULTS: 110 patients (220 eyes: 110 right eyes and 110 left eyes) were included. The mean age was 31.14 +/- 7.00 year (range 19 to 48 years). The mean astigmatism measured by manifest refraction (refractive astigmatism) was 0.76 +/- 0.72 diopters (range 0 to 3.50 diopters). The mean astigmatism measured by Orbscan Corneal Topographer (corneal astigmatism) was 1.38 +/- 0.72 diopters (range 0.20 to 5.30 diopters). The mean difference in magnitude of refractive and corneal astigmatism (internal astigmatism) was 0.62 +/- 0.67 diopters (range 0 to 3.00 diopters) and 74 per cent were within +/- 1.00 diopters difference. The mean difference in axis of astigmatism was 0.95 +/- 23 degree (range 0 to 85 degree) and 79.6 per cent were within +/- 15 degree difference. There was low correlation between corneal and internal astigmatism (R2 = 0.12, p < 0.05), also low correlation between refractive and internal astigmatism (R2 = 0.27, p < 0.05). There was a statistically significant difference between magnitude of corneal and refractive astigmatism (p < 0.05) but no difference in the axis of astigmatism (p = 0.55). CONCLUSION: This study demonstrated non-mutual agreement between refractive and corneal astigmatism (presence of internal astigmatism). High value (> 1.00 diopter) of internal astigmatism was demonstrated in 1/3 of the cases. Kerato-refractive surgery that attempts to correct refractive astigmatism at corneal plane may effect long-term evaluation of the astigmatism.

Blunt Trauma after LASIK.

We present 6 cases of blunt trauma after uneventful laser in situ keratomileusis (LASIK). The trauma was strong enough to cause macular edema in 2 cases, which lead to a transient decease of visual acuity, and 1 case had partial loss of the flap. No cases had rupture of the globe. This is evidence that LASIK surgery may not increase the risk of rupture of the globe after blunt trauma.

Penetrating keratoplasty after excimer laser surgery.

We present six patients who were referred after undergoing excimer laser surgery and subsequently required penetrating keratoplasty (PKP) to correct complications of the initial surgery. The excimer laser procedures included 5 cases of astigmatism and 1 case of hyperopic correction. All cases had complications, which decreased visual function and could not be corrected by non-surgical methods. Five cases had severe corneal haze and one case had an acute perforation following excimer laser surgery. After PKP, all patients had a best-corrected visual acuity (BCVA) which varied from 20/30 to 20/20. Awareness of potential complications, which need PKP after excimer laser surgery, is necessary.

Relationship between corneal thickness and level of myopia.

A retrospective study of 533 eyes, which underwent complete pre-operative evaluation for refractive surgery, was done. Regression Analysis was performed to find the correlation between corneal thickness and level of myopia and between corneal thickness and corneal curvature. There was statistically significant correlation between corneal thickness and level of myopia (p = 0.039) and also in corneal thickness and corneal curvature (p = 0.04). No clinical correlation was demonstrated (R2 = 0.014 and R2 = 0.0153, respectively). There was no clinical correlation between corneal thickness and level of myopia and also between corneal thickness and corneal curvature.

Rotation of the Eye from the Sitting to the Supine Position: A New Measurement Device.

A prospective study of 32 eyes, undergoing laser refractive surgery, was performed. Routine complete pre-operative evaluation was done. A new device (Ocular Cyclotorsion Measurement Device, OCMD‚ has been used to evaluate the rotation of the eye from the sitting to the supine position. 68.75 % (n = 22) of the eyes had no rotation with the position changes. 15 % (n = 5) had inward rotation and 15% (n = 5) had outward rotation. The range of rotation varied from 5 degrees to 10 degrees. There was no correlation between the degree of nearsightedness or astigmatism with the degree of rotation (R2 =0.037). The rotation of the eye from the sitting to supine position can cause misalignment of the axis of treatment especially cases with astigmatism. Care should be taken when treating cases with high astigmatism.