Corneal changes after laser in situ keratomileusis: measurement of corneal polarization magnitude and axis

PURPOSE: Laser in situ keratomileusis (LASIK) involves ablation of the corneal stroma, which may induce a change in birefringence. The purpose of this study was to determine the effect of LASIK on corneal birefringence by measuring corneal polarization magnitude (CPM) and axis (CPA). STUDY DESIGN: Cohort study. METHODS: In this prospective study, we measured the change in CPM and CPA before and after LASIK with a scanning laser polarimeter ([SLP] GDx-VCC; Laser Diagnostic Technologies, San Diego, California). Scans were completed on 23 subjects before and 3 months after LASIK. 14 normal controls were tested twice during the same time interval. Change in CPM, CPA, corneal thickness, and corneal curvature measurements were compared between LASIK and normal subjects. RESULTS: At baseline, the mean (95% confidence interval) values of CPM, CPA, corneal thickness, and corneal curvature measurements of the total population (n = 37) were 41.6 nm (36.6, 46.5); 31.5 degrees (25.7, 37.3); 548.4 microm (540.0, 556.7); and 7.6 mm (7.5, 7.7), respectively. There were no significant differences in baseline values between normal and LASIK subjects. The reproducibility, measured as the average standard deviation of CPM and CPA measurements in 30 normal control eyes, was 1.95 nm (1.43, 2.48) and 1.69 degrees (0.92, 2.46), respectively. Mean CPA, corneal thickness, and corneal curvature measurements were significantly different in patients after LASIK (all P <.0001). Mean absolute values of the change in both CPM and CPA were significantly greater in LASIK patients (4.8 nm [3.3, 6.4], and 10.4 degrees [6.8, 14.1], respectively) than in normal subjects (2.43 nm [1.53, 3.33], and 1.64 degrees [1.15, 2.14], respectively; both P < or =.05). The absolute value of change in CPA was linearly associated with the absolute value of change in both corneal thickness (R(2) = 0.46) and corneal curvature (R(2) = 0.44). CONCLUSIONS: LASIK causes a measurable change in corneal birefringence as measured by the CPM and CPA that may be related to loss of corneal tissue. Comparison of SLP measurements before and after LASIK requires eye-specific compensation to adjust for the change in corneal birefringence.     

Reduced corneal swelling and deswelling response in the iridocorneal endothelial syndrome.

PURPOSE: Despite severe abnormalities of the corneal endothelium in the iridocorneal endothelial (ICE) syndrome, the cornea can remain clear and maintain its normal thickness for years before corneal decompensation occurs. The aim of this study is to analyze this discrepancy by studying corneal hydration control in the ICE syndrome. METHODS: In four subjects with unilateral ICE syndrome, without signs of corneal decompensation, a "corneal stress test" was performed in both the affected and the unaffected eye. The stress test measures the recovery of corneal thickness after swelling induced by wearing a soft contact lens with the eyes closed. Corneal thickness was measured by noncontact pachymetry. RESULTS: Mean baseline corneal thickness of affected eyes (535+/-56 microm) was not different from unaffected eyes (526+/-39 microm). On the other hand, the corneal stress test showed a smaller induced swelling in affected eyes (33+/-15 microm) compared with unaffected eyes (67+/-11 microm) and a slower recovery of corneal thickness in affected eyes. In one of four subjects, the cornea of the affected eye was calculated not yet to have recovered its original thickness before midnight. After this finding, although the cornea of this subject did not show any signs of clinical decompensation, the study was discontinued. CONCLUSIONS: Corneal hydration control is altered in the ICE syndrome. The ICE cornea can maintain its normal thickness despite severe morphologic abnormalities of the endothelium. Because we found that recovery of corneal thickness can be extremely slow, it cannot be guaranteed that such corneal "stress tests" are completely safe for subjects with the ICE syndrome, and we therefore feel that they should no longer be performed in these subjects.     

The effect of contact lens induced corneal edema on Goldmann applanation tonometry measurements

AIM: To determine the effect of small increases in corneal hydration on the accuracy of Goldmann applanation tonometry estimates of intraocular pressure (IOP). MATERIALS AND METHODS: Twenty-five young healthy subjects presented on 3 separate days approximately 1 week apart. On 2 visits, subjects were required to wear a hydrogel contact lens with either a center thickness of 0.3 and 0.7 mm (HEMA 38% water content, parallel surface curve) in 1 eye only under closed-eye conditions for 2 hours to induce corneal swelling. The third visit acted as a control. IOP, corneal thickness, and corneal curvature were measured in both eyes before and after contact lens wear on all visits. RESULTS: There was a statistically significant increase in corneal thickness of 40.2+/-14.4 microm (P<0.001) and 41.9+/-16.4 microm (P<0.001) after wearing the 0.3 and 0.7 mm thick contact lenses, respectively (2-tailed paired t test). There was an increase in IOP of 2.8+/-2.2 mm Hg (P<0.001) after wearing the 0.3 mm thick contact lens, and a statistically insignificant difference of 1.3+/-3.0 mm Hg (P=0.058) after wearing the 0.7 mm thick contact lens (2-tailed paired t test). There was a statistically significant Pearson correlation between the change in corneal thickness and the change in IOP after lens wear (r=0.500, P<0.001, 0.3 mm lens and r=0.399, P<0.001, 0.7 mm lens). The corneal hydration-induced measurement error was 0.46 mm Hg per 10 microm change in corneal thickness (0.3 mm lens) and 0.35 mm Hg per 10 microm change in corneal thickness (0.7 mm lens). CONCLUSION: A small increase in corneal hydration and thickness may cause a clinically significant overestimation of IOP when measured using Goldmann applanation tonometry.     

Effect of hard contact lenses on corneal sensitivity and thickness.

Corneal sensitivity and central corneal thickness were measured on 11 subjects before and after 8 hours of hard contact lens wear. Both factors were monitored for 30 min after removal. It was found that hard contact lenses affect both corneal sensitivity and thickness, significantly. After 8 hours the reduction of sensitivity was found to be, on average, 94% in the centre and 116% in the periphery, and the average increase increase in thickness was 6.9%. Thirty minutes after removal corneal sensitivity had recovered 82% and 100% in the centre and periphery, respectively, and corneal thickness had decreased by 6.3%. A high correlation was found between central and peripheral corneal sensitivity. This investigation shows that corneal sensitivity measurements offer an alternative method of assessing corneal integrity which is simple and precise.     

Effect of proparacaine on central corneal thickness values: an evaluation using noncontact specular microscopy and pentacam

PURPOSE: To study the effect of 1 drop of 0.5% proparacaine on central corneal thickness values monitored by nonspecular microscopy and Pentacam, a corneal topographer with rotating Scheimpflug camera. METHODS: Forty subjects were divided into 2 groups with 1 group measured with a noncontact specular microscope and the other group with Pentacam (Oculus, Inc., Wetzlar, Germany). One eye was randomly selected, and corneal thickness values were monitored every 30 seconds for 10 minutes. Baseline corneal thickness values were defined as the average of all measurements taken over 10 minutes. One drop of 0.5% proparacaine was instilled, and the corneal thickness values were monitored by the same instrument every 30 seconds for another 10 minutes after drug instillation. RESULTS: The 2 groups shared similar age range, refractive error, and baseline corneal thickness values. The spontaneous variation of corneal thickness values was within 3 mum for 10 minutes before drug instillation. There was no obvious trend of corneal thickness value change after the instillation of local anesthetics. The variation of corneal thickness values against the baseline was within 5 mum. CONCLUSION: One drop of 0.5% proparacaine does not produce any significant change in central corneal thickness.     

Central corneal thickness in tilted disc syndrome.

PURPOSE.: Earlier literature reports that abnormal optic disc shape or size seem to be closely associated with the shape or size of the cornea. Here we search for an association between the presence of tilted disc syndrome and the central corneal thickness. METHODS.: Sixty-one eyes of 61 patients with tilted disc syndrome were included in the study. Sixty-one eyes of 61 subjects were chosen as controls. Corneal thickness was evaluated with ultrasound pachymetry from the central region after instillation of topical proparacaine hydrochloride and before the ophthalmologic examination. RESULTS.: The mean central corneal thickness in the tilted disc syndrome group was found to be 547.5 +/- 36.16 mum (median 546, range 467 to 638). The mean central corneal thickness in the control group was measured as 541.09 +/- 29.52 mum (median 540, range 500 to 627). There was no statistically significant difference in corneal thickness between the tilted disc syndrome group and control group (p = 0.218). CONCLUSION.: There seems to be no correlation between the central corneal thickness and the presence of tilted disc syndrome.     

长期配戴角膜塑形镜对角膜厚度和角膜内皮细胞的影响

目的评价近视眼患者长期配戴角膜塑形镜对角膜厚度和角膜内皮细胞的影响。方法利用超声角膜测厚仪和非接触角膜内皮显微镜,测量和观察132名青少年近视眼患者（264只眼）配戴角膜塑形镜（透氧系数为100）前和戴镜期间的角膜中央和旁周边部的角膜厚度,以及角膜内皮细胞的密度和形态学改变。结果无论采用夜戴方式还是日戴方式配戴角膜塑形镜3年以上,角膜中央及旁周边部厚度均无明显改变（P〉0．05）,角膜内皮细胞密度均无明显降低（P〉0．05）,角膜内皮细胞平均面积和细胞变异系数均无明显增大（P〉0．05）,角膜内皮细胞六角形比率均无明显降低（P〉0．05）。结论利用高透氧材料的角膜塑形镜进行科学的角膜塑形治疗,对角膜代谢的影响轻微,长期配戴用于控制近视发展基本是安全的。     

Age differences in corneal hydration control

Dynamic changes in corneal thickness were measured in eight young and eight older normal subjects (mean ages 24.4 +/- 4.3 years and 71.9 +/- 7.3 years, respectively) to provide data for quantitative assessment of corneal hydration control and thereby provide information for studying age differences in this important aspect of corneal function. For each subject, pachometry data were obtained by (A) monitoring corneal recovery following hypoxic stress, and by either (B1) measuring recovery after sleep or (B2) by measuring corneal thickness in the late afternoon. The combined data from A and B1 or A and B2 were analyzed through an exponential model to provide information on the: (1) percent recovery per hour (PRPH) following induced corneal hydration; (2) open-eye steady-state (OESS) corneal thickness; (3) residual corneal swelling just before the hypoxic stress test; (4) amount of corneal edema induced by hypoxic stress; and (5) time to reach 95% recovery back to the OESS thickness level (T95%). The results show that between the two age groups, there are substantial differences in some characteristics of corneal hydration while other aspects are similar. For example, the mean PRPH values (58.9 +/- 7.8% and 34.2 +/- 6.4%/hr) were significantly higher in the younger subjects (P = 0.0002) and the mean time for 95% recovery to OESS thickness (207 +/- 42 min and 452 +/- 117 min) was significantly lower in the younger vs. the older group (P = 0.0002).(ABSTRACT TRUNCATED AT 250 WORDS)     

Differences in corneal thickness and corneal endothelium related to duration in diabetes

PURPOSE: This study evaluated the differences of corneal thickness and corneal endothelial morphology in diabetes compared with age-matched, healthy control subjects; in addition, we tested for correlation according to the duration of diabetes. METHODS: Ultrasound pachymetry and noncontact specular microscopy were performed on 200 patients with diabetes and 100 control subjects. We compared the values for diabetics and normal persons with ANACOVA to adjust for age. Moreover, we examined the correlation between the subject parameters and the duration of diabetes by using a partial correlation coefficient that controlled for age. RESULTS: The diabetic subjects had thicker corneas, less cell density and hexagonality, and more irregular cell size of the corneal endothelium than did the controls (P < 0.05). Central corneal thickness and the coefficient of variation for cell size were significantly higher for diabetes of over 10 years' duration than for diabetes of under 10 years' duration (P < 0.05). The endothelial cell density and percentage of hexagonal cells were lower for diabetes of over 10 years' duration than for diabetes of under 10 years' (P > 0.05). Central corneal thickness was correlated with duration of diabetes (P < 0.05), but corneal endothelial morphology was not (P < 0.05). Conclusions: Those patients with diabetic duration of over 10 years have more corneal morphological abnormalities, especially the coefficient of variation in cell size, compared with the normal subjects. The central corneal thickness was significantly correlated with diabetic duration after controlling for age.     

The effects of long-term contact lens wear on corneal thickness, curvature, and surface regularity

PURPOSE: To evaluate the effect of long-term contact lens wear on corneal thickness, curvature, and surface regularity. DESIGN: A prospective, clinic-based, case-control study. PARTICIPANTS: A total of 40 eyes of 20 normal subjects and 64 eyes of 35 subjects wearing contact lenses for more than 5 years were evaluated. METHODS: The Orbscan Corneal Topography System was used to evaluate the entire corneal thickness and curvature, anterior curvature and the anterior and posterior elevation topographic patterns in normal eyes and subjects wearing contact lenses on a regular basis for more than 5 years. Indices of TMS-1 Corneal Topography System were used to determine corneal surface regularity in subjects wearing contact lenses and normal eyes. All topographic examinations were performed after contact lenses had been removed for at least 2 weeks. MAIN OUTCOME MEASURES: The entire corneal thickness, curvature, surface regularity index (SRI), surface asymmetry index (SAI), potential visual acuity (PVA) and topographic patterns were compared between normal eyes and subjects wearing contact lenses for more than 5 years. RESULTS: The 64 eyes of 35 subjects evaluated by the Orbscan instrument had an average of 13.45 +/- 6.42 years of contact lens wear. The mean corneal thickness in the center and in eight peripheral areas measured in contact lens wearing subjects was significantly reduced by about 30 to 50 microm compared to normal subjects (P < 0.001 for central and peripheral sites). No correlation was noted between central corneal thickness and degree of myopia in diopters (r = 0.15, 0.10 < P < 0.25). The corneal curvature, maximum keratometry (Max K) and minimum keratometry (Min K) readings, were significantly steeper in eyes wearing contact lenses than normal eyes (P < 0.01 for Max K and Min K measured by both instruments). No difference in the mean corneal astigmatism was noted between groups. The SRI and SAI, but not the PVA index, of the TMS-1 were significantly greater in contact lens wearers than in the control group (P < 0.01 for both SRI and SAI, P = 0.15 for PVA). The color-coded patterns of all curvature and elevation maps made with both instruments showed no significant difference between subjects wearing contact lenses and the control group. There was no significant difference between corneal curvature measurements taken with the Orbscan System or the TMS-1 System in both normal and contact lens groups. CONCLUSIONS: Long-term contact lens wear appears to decrease the entire corneal thickness and increase the corneal curvature and surface irregularity.     

蓝光对小鼠角膜上皮和角膜全层厚度的影响——基于光学相干断层扫描血管造影观察

目的　应用光学相干断层扫描血管造影（optical coherence tomography angiography，OCTA）观察蓝光对小鼠角膜上皮和角膜全层厚度的影响。方法　选取40只小鼠随机分为实验组和对照组，每组各20只，其中实验组小鼠每天8～16 h于蓝光环境下饲养，而对照组小鼠于正常环境下饲养。分别于照射前及照射后1周、2周、1个月、2个月、3个月，利用OCTA分别测量实验组和对照组小鼠的角膜上皮和角膜全层厚度。结果　与蓝光照射前相比，实验组、对照组分别在照射后1周、2周、1个月，各区域角膜上皮厚度无明显改变，差异均无统计学意义（均为P＞0.05）。与蓝光照射前相比，对照组在照射后2个月、3个月各区域角膜上皮厚度无明显改变，差异均无统计学意义（均为P＞0.05）。与对照组相比，实验组角膜上皮中央、N5、I5、T5区域明显增厚，差异均有统计学意义（均为P＜0.05）；蓝光照射后3个月，与对照组相比，实验组小鼠角膜中央、内环及N6、T6区域角膜上皮厚度均明显增厚，差异均有统计学意义（均为P＜0.05）。蓝光照射前，照射后1周、2周、1个月、2个月、3个月，实验组与对照组相比，各区域角膜全层厚度比较无明显改变，差异均无统计学意义（均为P＞0.05）。两组角膜上皮厚度的极值，即最大值和最小值差值比较，差异有统计学意义（P<0.05），但两组角膜全层厚度最小值和最大值的差值比较无明显统计学意义（P＞0.05）。结论　蓝光能引起小鼠角膜上皮厚度改变，且中央区域改变较为明显，但短期内角膜全层厚度无明显改变。     

Effect of timolol on central corneal thickness and endothelial cell density

BACKGROUND: The measurement of corneal thickness plays an increasing role in glaucoma screening and diagnosis. The influence of a variety of drugs on corneal thickness is well established. Especially for antiglaucomateous drugs this effect seems to be important. However, little is known about the influence of beta receptor antagonists on corneal thickness. The aim of this study was to provide evidence of the effect of timolol on central corneal thickness and endothelial cell density. MATERIALS AND METHODS: Ten healthy volunteers (five women and five men) with a mean age of 29 years (range 25 to 56 years) were examined in a double-blind, prospective and randomised pilot study. Intraocular pressure, corneal thickness and endothelial cell density was estimated before as well as fifteen minutes, 24, 48, 72 and 96 hours after application of timolol 0.5 % eye drops twice daily. The partner eye received sodium hyaluronate eye drops twice daily and served as a control. RESULTS: The application of timolol showed a decrease of intraocular pressure from initially 12 mmHg to 9 mmHg after four days (p = 0,0188) as well as an increase of corneal thickness from 537 microm to 557 microm after four days (p = 0,0659). There was no change of intraocular pressure (p = 0,9935) or corneal thickness (p = 0,9998) in the control eyes. There was also no effect of timolol (p = 0,2782) or sodium hyaluronate (p = 0,1940) on endothelial cell density. CONCLUSIONS: The study provides evidence of the influence of beta receptor antagonists on corneal thickness. This effect may be caused by receptor mediated influences on corneal ion and fluid transport. Further studies are needed to show if the increase of corneal thickness after application of topical timolol has clinical importance.     

糖尿病患者白内障超声乳化术后角膜内皮的变化

目的:应用共聚焦显微镜观察糖尿病患者行白内障超声乳化术前后角膜内皮的变化。方法:随机选取年龄相关性白内障合并糖尿病患者(糖尿病组)50例56眼和单纯年龄相关性白内障患者50例60眼(对照组),行白内障超声乳化摘除联合折叠式人工晶状体植入术。术前及术后1wk;1,3mo应用共聚焦显微镜分别对中央角膜厚度、内皮细胞密度、内皮细胞变异系数及六角形内皮细胞百分比进行观察,分析结果。结果:两组术前中央角膜厚度、内皮细胞密度、内皮细胞变异系数、六角形内皮细胞百分比差异无统计学意义(P>0.05);跟术前相比,术后两组角膜厚度、内皮细胞变异系数均增加,内皮细胞密度、六角形细胞百分比均呈下降趋势;术后1wk;1,3mo糖尿病组中央角膜厚度均高于对照组(P<0.05),内皮细胞密度均低于对照组(P<0.05);术后1wk;1,3mo糖尿病组六角形内皮细胞百分比明显低于对照组(P<0.01),内皮细胞变异系数明显高于对照组(P<0.01)。结论:合并糖尿病的年龄相关性白内障患者超声乳化术后角膜内皮的损伤更严重,且创伤愈合的速率和效率均差于单纯相关性白内障患者。     

Corneal volume measures for monitoring contact lens induced corneal swelling: a pilot study

Background: This study investigated the use of corneal volume to monitor the corneal swelling response induced by wearing high plus power contact lenses. Methods: Twelve young non‐contact lens wearers were recruited with one eye fitted with a soft contact lens (Polymacon material, 38.6 per cent water, Dk of 9 and 0.27 mm centre thickness) and the fellow eye served as control. The treated eye was patched for two hours leaving the control eye uncovered. Central corneal thickness (CCT) was measured with non‐contact specular microscopy and corneal volumes (at three, five and 10 mm zones) were measured with a corneal topographer (Pentacam, Oculus Inc, Germany), before eye patching as well as immediately after and every 20 minutes for 100 minutes. Results: Subjects had similar CCT and corneal volumes between the two eyes before treatment. The treatment eyes showed a mean corneal swelling of 8.1 per cent immediately after lens removal. Corneal volume was significantly increased at the three (mean swelling of 5.9 per cent), five (5.6 per cent) and 10 millimetre (3.3 per cent) zones. It took 20 minutes for the corneal volume at the 10 mm zone to return to baseline but required 60 minutes for the three and five millimetre zones to return to the baseline level. The central corneal thickness was still significantly thicker 80 minutes after patching. Conclusion: Corneal volume could be a useful parameter to monitor corneal change when an event affects the entire cornea. Corneal volume combined with central corneal thickness could give more comprehensive information to monitor central corneal swelling.     

Residual bed thickness and corneal forward shift after laser in situ keratomileusis

PURPOSE: To prospectively assess the forward shift of the cornea after laser in situ keratomileusis (LASIK) in relation to the residual corneal bed thickness. SETTING: Miyata Eye Hospital, Miyazaki, Japan. METHODS: Laser in situ keratomileusis was performed in 164 eyes of 85 patients with a mean myopic refractive error of -5.6 diopters (D) +/- 2.8 (SD) (range -1.25 to -14.5 D). Corneal topography of the posterior corneal surface was obtained using a scanning-slit topography system before and 1 month after surgery. Similar measurements were performed in 20 eyes of 10 normal subjects at an interval of 1 month. The amount of anteroposterior movement of the posterior corneal surface was determined. Multiple regression analysis was used to assess the factors that affected the forward shift of the corneal back surface. RESULTS: The mean residual corneal bed thickness after laser ablation was 388.0 +/- 35.9 microm (range 308 to 489 microm). After surgery, the posterior corneal surface showed a mean forward shift of 46.4 +/- 27.9 microm, which was significantly larger than the absolute difference of 2 measurements obtained in normal subjects, 2.6 +/- 5.7 microm (P<.0001, Student t test). Variables relevant to the forward shift of the corneal posterior surface were, in order of magnitude of influence, the amount of laser ablation (partial regression coefficient B = 0.736, P<.0001) and the preoperative corneal thickness (B = -0.198, P<.0001). The residual corneal bed thickness was not relevant to the forward shift of the cornea. CONCLUSIONS: Even if a residual corneal bed of 300 microm or thicker is preserved, anterior bulging of the cornea after LASIK can occur. Eyes with thin corneas and high myopia requiring greater laser ablation are more predisposed to an anterior shift of the cornea.     

角膜厚度和角膜曲率对LASIK术后眼压测量值的影响

目的探讨准分子激光原位角膜磨镶术（LASIK）后角膜厚度和角膜曲率对眼压测量值的影响。方法150例（285眼）近视行LASIK并随访1年，对手术前后的角膜厚度、角膜曲率及眼压进行统计学分析。结果LASIK术后3、6、12个月的角膜厚度、角膜曲率及眼压测量值均较术前明显下降（P〈0．01）。术前及术后3、6、12个月的眼压测量值与角膜厚度、角膜曲率呈正相关。结论LASIK术后眼压测量值低于术前，眼压测量值与角膜厚度和角膜曲率均呈正相关，角膜厚度和角膜曲率是眼压测量值的影响因素。     

Corneal thickness values before and after oxybuprocaine 0.4% eye drops

PURPOSE: To determine changes in corneal thickness after topical anesthesia. METHODS: Corneal thickness was measured before and 3 minutes after administration of two drops of oxybuprocaine 0.4% to 26 patients (26 eyes). We analyzed the corneal thickness of a control group, which was made up of 26 patients (26 eyes) before and 3 minutes after administration of two drops of saline solution. Corneal thickness was measured with the Orbscan Topography System II (Bausch Lomb Surg., Barcelona). RESULTS: Variations higher than +/- 10 microm were found following the instillation of 2 oxybuprocaine eye drops in eight eyes (30.76%) at the inferonasal cornea, in six eyes (23.08%) at the superotemporal, temporal and inferotemporal cornea, in five eyes (19.23%) at the nasal cornea, in three eyes (11.53%) at the central cornea, and in two eyes (7.69%) at the superonasal cornea. Nevertheless, no significant differences in the mean corneal thickness at each corneal location between the first and the second corneal thickness measurements were found in anesthetized eyes. CONCLUSIONS: Some individuals can present important increases and decreases in corneal thickness values after anesthetic eye drops. This effect of anesthetic eye drops must be considered by refractive surgeons when carrying out preoperative laser in situ keratomileusis corneal thickness measurements.     

Corneal endothelial cell morphometry and corneal thickness in diabetic contact lens wearers.

PURPOSE: To assess corneal endothelial cell morphometry and corneal thickness in diabetic patients who wear contact lenses. METHODS: Images of the central corneal endothelium were analyzed quantitatively and qualitatively and corneal thickness was measured in a group of diabetic patients (type 1, N = 26; type 2, N = 4) who wear soft contact lenses and in a group of nondiabetic age-matched control subjects who were also contact lens wearers. RESULTS: Endothelial cell characteristics and corneal thickness values were similar for the two groups (p > 0.05). Four of the diabetic patients (and none of the nondiabetic patients) displayed folds in the endothelial mosaic. CONCLUSIONS: The morphometry of corneal endothelial cells and central corneal thickness values in diabetic patients who wear soft contact lenses were not appreciably different from those found in lens-wearing control subjects.     

Corneal thickness after cataract extraction. Early observations]

The corneal thickness was measured after cataract extraction. In 36 patients the thickness was tested by an ultrasound pachymetry before the operation and on the 1, 3 and 7 day after surgery. The visual acuity and the clinical status of the cornea of the operated eye were also examined. The most pronounced oedema was seen on the first day in the neighbourhood of the incision. On the 7th postoperative day the corneal thickness approximated the status existing before the operation in the majority of patients. There was a dependence between the corneal thickness and its clinical status and the visual acuity.     

Factors affecting the central corneal thickness of Hong Kong-Chinese.

PURPOSE: The aims of this study were to investigate the effect of age, intraocular pressure, refractive error (spherical equivalent) and corneal curvatures on the central corneal thickness of Hong Kong-Chinese. We also compared the central corneal thickness of Hong Kong-Chinese with those previously reported for other national/ethnic groups. METHODS: The central corneal thicknesses of 151 subjects of age 10-60 yrs were measured using an ultrasound pachometer. Intraocular pressure, refractive error and the corneal curvatures of these subjects were also recorded. RESULTS: The mean +/- SD central corneal thickness of the right eye and left eye were 575 +/- 32 microm and 574 +/- 31 microm respectively. No significant difference in central corneal thickness was found between the right and left eyes or between male and female subjects. Central corneal thickness decreased with increasing age but the effect appeared to be due to differences in female subjects only. The maximum decrease in central corneal thickness occurred in subjects in the age group of 10-25 yrs, and in this age group, central corneal thickness and age was significantly correlated in both male and female subjects. Intraocular pressure and central corneal thickness was significantly correlated. There was no correlation between central corneal thickness and refractive error or between central corneal thickness and corneal curvatures. CONCLUSIONS: Central corneal thickness decreased with increasing age but this appeared to be due to female subjects only. Central corneal thickness was significantly correlated with intraocular pressure, but not with refractive error or corneal curvatures. Our subjects also had significantly thicker corneas than those reported for Caucasian subjects.