Shetgar Anupama C, Mulimani Mariyappa B
Assistant Professor, Department of Ophthalmology, Sri Nijilingappa Medical College , Navanagar, Bagalkot, Karnataka, India .
J Clin Diagn Res. 2013 Jun;7(6):1063-7. doi: 10.7860/JCDR/2013/4292.3022. Epub 2013 Jun 1.
To compare the Central Corneal Thickness (CCT) of Normal Tension Glaucoma (NTG) with those of Primary Open Angle Glaucoma (POAG) and Ocular Hypertension (OHT) and to study the effect of CCT on the diagnosis and management of glaucoma patients.
A total of 99 patients [35(35.35%) females and 64(64.65%) males] were included in the study with four study groups-37 controls (males-24 and females-13), 22 NTG (males-11 and females-11), 28 POAG (males-21 and females-7), and12 OHT (males-8 and females-4). The CCTs of all the participants were measured by using ultrasonic pachymetry. The IOPs were measured by using applanation tonometry. The measured IOPs were corrected by using a linear correction formula. The measurement significant changes (>=1.5) and outcomes significant changes (>=3.0) for the study groups were calculated.
The mean CCT of the normals was 527.65± 21.90 μ, the mean NTG was 503.91 ± 11.31 μ, the mean POAG was 525.25± 23.59 μ and the mean OHT was 572.25± 22.71 μ. The difference which was observed in the mean CCT among the groups was statistically significant (p<0.05). The measurement significant change (>=1.5) after correcting the IOP for CCT was observed in 32.258% of the total glaucoma patients, with 27.3% patients ( 6 out of 22) in the NTG, 66.7% patients (8 out of 12) in the OHT and 21.4% patients ( 6 out of 28) in the POAG groups showing it. The difference which was observed was statistically significant (p<0.05). The outcomes significant change (>=3.0) after correcting the IOP for CCT was seen in 6.45% of the total glaucoma patients, with none of the NTG group patients showing outcomes significant changes, whereas 3.57% patients (1out of 28) in the POAG and 25% patients ( 3out of 12) in the OHT groups showed these changes. The difference which was observed was statistically significant (p<0.05).
This study confirmed that the central corneal thickness was significantly lower in the normal tension glaucoma patients as compared to those in the controls and in the primary open angle glaucoma patients, whereas the ocular hypertension patients had significantly higher central corneal thicknesses than the controls and the primary open angle glaucoma patients. No significant difference was found between the primary open angle patients and the controls. Due to the effect of CCT on the measurement of the IOP by using an applanation tonometer, which is the main parameter in the diagnosis and the follow up of the glaucoma patients, many POAG patients are misdiagnosed as NTG patients and the normals are misdiagnosed as OHT patients and they are improperly managed. Measurement of the central corneal thickness aid the ophthalmologist in making a correct diagnosis and in a better management of glaucoma and the glaucoma suspects, especially when their corneal thickness differs markedly from the normal thickness.
比较正常眼压性青光眼（NTG）、原发性开角型青光眼（POAG）和高眼压症（OHT）患者的中央角膜厚度（CCT），并研究CCT对青光眼患者诊断和治疗的影响。
本研究共纳入99例患者[35名女性（35.35%）和64名男性（64.65%）]，分为四个研究组——37名对照组（24名男性和13名女性）、22名NTG患者（11名男性和11名女性）、28名POAG患者（21名男性和7名女性）和12名OHT患者（8名男性和4名女性）。所有参与者的CCT均采用超声测厚法测量。眼压采用压平眼压计测量。测量的眼压使用线性校正公式进行校正。计算研究组的测量显著变化（>=1.5）和结果显著变化（>=3.0）。
正常组的平均CCT为527.65±21.90μm，NTG组为503.91±11.31μm，POAG组为525.25±23.59μm，OHT组为572.25±22.71μm。各组间平均CCT的差异具有统计学意义（p<0.05）。校正CCT后的眼压后，32.258%的青光眼患者出现测量显著变化（>=1.5），其中NTG组27.3%的患者（22例中的6例）、OHT组66.7%的患者（12例中的8例）和POAG组21.4%的患者（28例中的6例）出现该变化。观察到的差异具有统计学意义（p<0.05）。校正CCT后的眼压后，6.45%的青光眼患者出现结果显著变化（>=3.0），NTG组患者均未出现结果显著变化，而POAG组3.57%的患者（28例中的1例）和OHT组25%的患者（12例中的3例）出现这些变化。观察到的差异具有统计学意义（p<0.05）。
本研究证实，正常眼压性青光眼患者的中央角膜厚度显著低于对照组和原发性开角型青光眼患者，而高眼压症患者的中央角膜厚度显著高于对照组和原发性开角型青光眼患者。原发性开角型青光眼患者与对照组之间未发现显著差异。由于CCT对使用压平眼压计测量眼压有影响，而眼压是青光眼患者诊断和随访的主要参数，许多POAG患者被误诊为NTG患者，正常人被误诊为OHT患者，且治疗不当。测量中央角膜厚度有助于眼科医生做出正确诊断并更好地治疗青光眼及青光眼疑似患者，尤其是当他们的角膜厚度与正常厚度有明显差异时。
