Evaluation of the agreement and reliability of Transpalpebral Tonometers compared with Goldmann Applanation Tonometer – A systematic Review and Meta-Analysis Protocol

In 2020, the global prevalence of glaucoma was estimated to be 76 million and it was projected to increase to 111.8 million by 2040. Accurate intraocular pressure (IOP) measurement is imperative in glaucoma management since it is the only modifiable risk factor. Numerous studies have compared the reliability of IOP measured using transpalpebral tonometers and Goldmann applanation tonometry (GAT). This systematic review and meta-analysis aims to update the existing literature with a reliability and agreement comparison of transpalpebral tonometers against the gold standard GAT for IOP measurement among individuals presenting for ophthalmic examinations. The data collection will be performed using a predefined search strategy through electronic databases. Prospective methods-comparison studies published between January 2000 and September 2022 will be included. Studies will be deemed eligible if they report empirical findings on the agreement between transpalpebral tonometry and Goldmann applanation tonometry. The standard deviation and limits of agreement between each study and their pooled estimate along with weights and percentage of error will be reported using a forest plot. Cochrane’s Q test and the I2 statistic will be used to assess heterogeneity, and the publication bias will be investigated using a funnel plot, Begg’s and Egger’s tests. The review results will provide additional evidence on the reliability of transpalpebral tonometers that, in turn, could possibly assist practitioners to make informed decision about using it as a screening or diagnostic device for clinical practice, outreach camps, or home-based screening. Institutional Ethics Committee registration number: RET202200390. PROSPERO Registration Number: CRD42022321693.

Reutilization of disposable rebound tonometer probes: Risk or return?

Purpose: An advantage of rebound tonometry (RT) is its ease of use so that it can also be operated by health care technicians. However, the cost of the disposable measuring probes is high and their reuse carries the risk of infection. Therefore, this study aims to objectify the potential risk of bacterial transmission by RT. Methods: Our experimental setting consisted of two experiments. The first aimed to quantify the number of bacteria on a tonometer probe after immersion in a bacterial suspension in vitro. The experiment was carried out with two different bacteria and compared with results from a Goldmann tonometer probe. The second experiment tested whether bacteria could be transmitted by simulating reuse of a nondisinfected rebound tonometer probe. Results: First experiment: After immersion of the rebound tonometer probe, we measured a bacterial count of 2.43 × 106 Escherichia coli (EC) and 1.12 × 106 Pseudomonas fluorescens. In total, 1.09 × 107 bacteria for EC and 2.61 × 106 for Pseudomonas fluorescens (PF) were measured on the Goldmann tonometer probe. Second experiment: A bacterial transmission could be detected in 36% of cases in which reuse of nondisinfected tonometer probes was simulated. Conclusion: These results show that despite the small surface of the rebound tonometer probe, there is a clear risk of bacterial transmission. Thorough disinfection according to general standards should be mandatory if the tonometer probes are to be reused.

Study-of-phacoemulsification-vs-phacotrabeculectomy-in-management-of-primary-angle-closure-glaucoma

Introduction: The study was conducted to evaluate IOP management by surgical modalities such as combined trabeculectomy and phacoemulsification and phacoemulsification surgery alone. Vision impairment is a major public health problem and the burden is increasing with increase in aged population. This study wasAims And Objectives: undertaken for study the IOP management by surgical modalities such as combined trabeculectomy and phacoemulsification and phacoemulsification surgery alone. A pre-designed prospective study was conducted at the OPD of upgraded Department of Ophthalmology at LLRM Medical College, Meerut. A total of 60 patients were divided in to two equal groups randomly and studied. Majority of the patients in both the groups wereObservation And Result: aged between 61 – 70 years. Females outnumbered males in this study which was statistically significant between the two groups. The mean pre- operative intra ocular pressure was 23.3 mm Hg in combined surgery group and 23.9 mm Hg in cataract surgery alone group. Mean Intra ocular pressure decreased regularly in each follow up more in combined group than the cataract surgery alone group. The mean intra ocular pressure after 1 years follow up in combined surgery group was 10.8 mm Hg and 13.4 mm Hg in the cataract surgery alone groups which was statistically significant. Mean BCVA before the operation was 3.2 in combined surgery group and 3.8 in cataract surgery before surgery. Mean BCVA declined after 1 year of follow up in combined surgery group was 1.9 and 2.7 in cataract surgery alone group which was statistically significant. The surgery success was complete in 80.0% of the combined surgery group and 60% of the cataract alone group. Criteria For Failure Of Surgeries Ÿ The IOP >23 MMHG at the end of 1 year or Ÿ The IOP not reduced by 20 % from base line at the end of 1 year Conclusion: This study was mainly undertaken to study the efficacy of combined trabeculectomy with cataract extraction and cataract only on primary angle closure glaucoma. This study had found that, the reduction of intra ocular pressure in both the groups but more prominent in combined surgery group than cataract alone surgery group.

Effect of acupuncture on intraocular pressure and tear production in healthy horses / Efeito da acupuntura sobre a pressão intraocular e a produção lacrimal em equinos hígidos

ABSTRACT: Acupuncture is an ancient Chinese form of therapy that involves needle stimulation of specific points on the body for therapeutic and homeostatic effects. In ophthalmology, acupuncture helps as a conventional or adjuvant therapy for numerous eye disorders, including myopia, strabismus, dry eye, and cataracts. This study aimed to evaluate the effect of acupuncture on tear production (TP) and intraocular pressure (IOP) in horses. Ten healthy horses, females and males with ages varying between eight months and nine years, were used. Schirmer's I test and applanation tonometry were used to evaluate the basal TP and IOP of both eyes. The measurements were taken immediately before (T10) the insertion of the needles and 5 (T5), 15 (T15), 30 (T30) and 60 (T60) minutes and 24 (T24) hours after a 20-minute acupuncture session. Mean values of both eyes were analyzed over time. TP increased in 50% of the animals at T5, T15 and T24, in 30% at T30, and in 40% at T60, with an increase of up to 8.5 mm/min at T15 and T60. In addition, there was a significant difference between T24 and T30, with a 14.1% increase in TP at T24. Meanwhile, IOP decreased in 50% of the animals at T5 and T30, in 20% at T15, in 60% at T60, and in 70% at T24. Thus, we suggest that acupuncture is a technique that can benefit horses with diseases that alter these parameters, either alone or as an adjunct in conventional therapeutic protocols.

RESUMO: A acupuntura é uma terapia milenar de origem chinesa que funciona através da estimulação de pontos específicos do corpo com agulhas, visando efeitos terapêuticos e homeostáticos. Na área de oftalmologia a acupuntura tem auxiliado como terapia convencional ou adjuvante de inúmeras afecções oculares, incluindo miopia, estrabismo, olho seco, catarata, entre outras. Esse estudo teve como propósito avaliar o efeito da acupuntura no comportamento da produção lacrimal e da pressão intraocular em equinos. Utilizou-se 10 equinos hígidos, fêmeas e machos, com idades variando entre oito meses e nove anos. O teste lacrimal de Schirmer tipo I e da tonometria de aplanação foram utilizados para avaliar a produção basal de lágrima (PL) e a pressão intraocular (PIO) de ambos os olhos. As aferições foram realizadas imediatamente antes da inserção das agulhas (T0) e cinco (T5), 15 (T15), 30 (T30) e 60 (T60) minutos e 24 (T24) horas após sessão de acupuntura de 20 minutos. Os valores obtidos foram analisados quanto ao seu comportamento ao longo do tempo, utilizando-se a média dos dois olhos de cada animal. A PL aumentou em 50% dos animais em T5, T15 e T24, 30% dos animais em T30 e 40% dos animais em T60, com aumento de até 8,5 mm/min em T15 e T60. Além disso, observou-se diferença significativa entre o T24 e o T30 (p = 0,0128), com aumento de 14,1% na PL no T24. Com relação à PIO, notou-se que 50% dos animais sofreram redução na pressão em T5 e T30, 20% dos animais redução em T15, 60% dos animais em T60 e 70% dos animais apresentaram redução em T24. A estimulação dos acupontos relacionados ao sistema visual foi capaz de aumentar a produção lacrimal e diminuir a pressão intraocular em equinos sadios. Dessa maneira, sugere-se que a acupuntura é uma técnica que poderá trazer benefícios a cavalos portadores de doenças que cursam com a alteração desses parâmetros, tanto quando empregada isoladamente, como quando adjuvante a protocolos terapêuticos convencionais.

Accuracy of intraocular pressure measurements between non-contact tonometer and ICare rebound tonometer / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To analyze the accuracy of non-contact tonometer(NCT)and ICare rebound tonometer(RBT)in measuring intraocular pressure in glaucoma patients. <p>METHODS:A retrospective proportional control study. Totally 113 patients(185 eyes)with glaucoma were studied. Intraocular pressure was measured by RBT, NCT and Goldmann Applanation tonometer(GAT)at 9:00 and 16:00 and recorded as two sets of data, respectively. Their accuracy is evaluated by the rank sum test, and the international standard 8621 guide, Bland-Altman consistency analysis analyzed the consistency of the two groups of measurements, and the data were divided into two groups: abnormal intraocular pressure group(<10mmHg or >21mmHg)and normal intraocular pressure group(10-21mmHg). The consistency was analyzed between different groups. The spearman correlation analysis is adopted to analyze the correlation between ophthalmotonometers.<p>RESULTS: There were differences among the GAT, NCT and RBT measurements(<i>P</i><0.01). There was a strong correlation between the intraocular pressure measured value obtained by GAT and measured values obtained by RBT and NCT(<i>rs</i>=0.71, 0.77, <i>P</i><0.001). The measured values of NCT and GAT are close to each other without statistically significant differences(<i>P</i>=0.92). Compared with GAT, RBT has a higher intraocular pressure measured value, and there are significant differences(<i>P</i><0.05). However, compared with GAT, both NCT and RBT have a wide range of limits of agreement, and they are(-6.2-6.0mmHg)and(-5.2-7.6mmHg)respectively. In normal intraocular pressure groups, the ranges of limits of agreement are(-5.9-5.9mmHg)and(-4.3-7.5mmHg)respectively. In abnormal intraocular pressure groups, the ranges of limits of agreement are(-7.3-6.4mmHg)and(-7.5-5.6mmHg)respectively. The evaluation carried out in accordance with ISO 8612 guides indicates that the abnormal values more than the 95% of consistency restriction of NCT and RBT in the three groups are(3.9%, 11.3%, 12.2%)and(26.3%, 11.3%, 12.2%)respectively.<p>CONCLUSION: Both NCT and RBT cannot simply replace the GAT to measure the intraocular pressure of glaucoma patients. In glaucoma patients, with the deviation of the measured value from the normal intraocular pressure range, the measurement error of NCT and RBT also increase.

Comparison of IOP detected by three kinds of tenonometers in children with high intraocular pressure and their relations with corneal thickness / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To investigate the central corneal thickness(CCT)distribution of the children with ametropia in the non-contact tonometry(NCT), and the different intraocular pressure(IOP)measurements with Goldmann applanation tonometry(GAT)and the OCULUS Corvis ST(CST)corneal biomechanical analyzer, meanwhile, to evaluate the correlation between IOP and CCT. <p>METHODS: NCT was used to measure 39 children(78 eyes)of non-glaucomatous ametropia with single eye or binocular IOP higher than 21 mmHg. The IOP was measured again with CST and GAT. The two instruments were measured in random order and the CCT was measured by CST and corrected the IOP according to the CCT. The eyes were divided into the normal group and the thicker group according to the CCT. The three IOP values were analyzed by the ANOVA, and the IOP and CCT was analyzed by the Pearson correlation coefficient. <p>RESULTS: In the normal CCT group, the IOP by CST was lower than that the GAT and NCT measurements and the difference was statistically significant(<i>F</i>=5.12, <i>P</i>=0.01). In the thicker group, the comparison of the three intraocular pressure measurement methods was statistically significant(<i>F</i>=15.72, <i>P</i><0.001). IOP by NCT and GAT were significantly correlated with CCT(<i>r</i>_NCT=0.298, <i>P</i>_NCT=0.04; <i>r</i>_GAT=0.408, <i>P</i>_GAT=0.01). There was no significant correlation between CST corrected intraocular pressure and CCT(<i>r</i>_CST=0.062, <i>P</i>_CST=0.593). <p>CONCLUSION: The CCT of ametropia children with high IOP by Topcon tonometry were thicker. The corrected intraocular pressure of CST is lower than NCT and GAT. NCT and GAT were positively correlated with CCT. For children with thicker CCT, CST corrects intraocular pressure was closer to the real intraocular pressure value than NCT and GAT.

Comparison of Intraocular Pressure via Goldmann-applanation Tonometry and TonoPen in Thyroid-associated Ophthalmopathy Accompanying Restrictive Strabismus

PURPOSE: To compare the intraocular pressure (IOP) measured using Goldmann-applanation tonometry (GAT) and Tonopen® tonometry and to evaluate the factors influencing the measurement difference in patients with thyroid-associated ophthalmopathy (TAO)-related restrictive strabismus. METHODS: In 50 eyes of 50 patients who were diagnosed with TAO, IOP measurements were taken using both GAT and a Tonopen® and were subsequently compared between the devices. Factors influencing the measurement difference between the devices were determined, including the restriction of eyeball movement, eyeball deviation, exophthalmometry, central corneal thickness, refractive errors, and blood thyroid hormone levels. RESULTS: In the TAO patients, the GAT-measured IOP was higher than for Tonopen® (16.1 ± 4.7 vs. 13.8 ± 4.5 mmHg, respectively, p < 0.001). As the restriction of vertical eyeball movement increased, the IOP difference between the devices also increased (p = 0.037). The absolute IOP difference between the devices was positively correlated with restrictions in vertical eyeball movement (p = 0.027), degree of vertical strabismus (p = 0.021), and central corneal thickness (p ≤ 0.031). CONCLUSIONS: In patients with TAO accompanying vertical eyeball movement restriction, potential errors in IOP measurements should be considered between the different IOP-measuring devices.

Comparison of Dynamic Contour Tonometry and Goldmann Applanation Tonometry in Relation to Central Corneal Thickness

PURPOSE: In this study we compared the intraocular pressures (IOPs) measured using dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) and investigated the correlation between central corneal thickness (CCT) and IOP. METHODS: In a prospective study, 178 eyes of 91 subjects with glaucoma and glaucoma suspect were enrolled. IOP was measured using DCT and GAT and CCT was measured using ultrasound pachymetry. Each eye was classified into 1 of 3 groups according to their CCT: low CCT (Group A; CCT or = 561 microm). In each group, we investigated the correlation between CCT and IOP measurement using GAT and DCT. RESULTS: A significant correlation was found between CCT and IOP measured using GAT (p < 0.001), but not between CCT and IOP measured using DCT (p = 0.108) in all patients. Subgroup analysis showed that CCT affected IOP measured with GAT only in Group A (p = 0.027) and IOP measured with DCT was not affected by CCT in all 3 groups. CONCLUSIONS: IOP measured using GAT and DCT were significantly affected by CCT, especially when the CCT was low. CCT may have no effect on DCT thus, IOP measured using DCT is more reliable than GAT in patients with thin corneas.

Tonometría neumática vs. tonometría aplanación, en sospechosos de glaucoma / Pneumatic tonometry vs. applanation tonometry in patients with glaucoma suspicion

Se presentó un estudio descriptivo, transversal, sobre la tonometría ocular, donde se determinó la presión intraocular con dos métodos diferentes de exploración en pacientes sospechosos de glaucoma, y un grupo normal en los pacientes que asistieron a la consulta externa del Hospital Universitario Clínico Quirúrgico Comandante Faustino Pérez, de Matanzas, de enero a diciembre de 2010, con el objetivo de comparar en término de seguridad ambos métodos, y así determinar el más idóneo para los pacientes. El método de neumotonómetro resultó el ideal. Se puso de manifiesto un mejoramiento de la calidad del proceso asistencial y de los servicios de salud que se brindan; el neumotonómetro (air-puff) permitió avances en el diagnóstico y tratamiento en una modalidad no invasiva, precisa, eficiente, más segura y fácil de realizar.

We presented a descriptive, prospective study on the ocular tonometry, where we determined the intraocular pressure using two different exploring methods in glaucoma suspected patients, and a normal group of the patients who assisted the outpatient consultation of the University Clinical Surgical Hospital Comandante Faustino Pérez, of Matanzas, from January to December 2010. The objective was comparing both methods in security terms, and determining which is the most efficacious for the patients. The pneumotonometry method was the ideal one. It was showed the quality improvement of the health care process and the given health care services; the pneumotonometer (air-puff) allowed advances in the diagnostic and treatment with a non-invasive, precise, efficient modality, more secure and easier to make.

Evaluation of the Perkins handheld applanation tonometer in horses and cattle

The objective of this study was to evaluate and validate the accuracy of the Perkins handheld applanation tonometer for measuring intraocular pressure (IOP) in horses and cattle. Both eyes of 10 adult horses and cattle were evaluated in a postmortem study. The eyes from 10 clinically normal adult horses and cattle were also examined after bilateral auriculopalpebral nerve block and topical anesthesia for an in vivo study. IOP was measured postmortem using direct manometry (measured with an aneroid manometer) and tonometry (measured with a Perkins handheld applanation tonometer). The correlation coefficients (r2 ) for the data from the postmortem manometry and Perkins tonometer study were 0.866 for horses and 0.864 for cattle. In the in vivo study, IOP in horses was 25.1 +/- 2.9 mmHg (range 19.0~30.0 mmHg) as measured by manometry and 23.4 +/- 3.2 mmHg (range 18.6~28.4 mmHg) according to tonometry. In cattle, IOP was found to be 19.7 +/- 1.2 mmHg (range 18.0~22.0 mmHg) by manometry and 18.8 +/- 1.7 mmHg (range 15.9~20.8 mmHg) by tonometry. There was a strong correlation between the IOP values obtained by direct ocular manometry and the tonometer in both horses and cattle. Our results demonstrate that the Perkins handheld tonometer could be an additional tool for accurately measuring IOP in equine and bovine eyes.

Comparison Between Dynamic Contour Tonometry and Goldmann Applanation Tonometry

PURPOSE: To compare the intraocular pressures (IOPs) measured by dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT), and to investigate the association of IOPs on eyes of varying central corneal thickness (CCT). METHODS: In this prospective study, 451 eyes of 233 subjects were enrolled. IOPs were measured by GAT and DCT. CCT was measured three times and the average was calculated. Each eye was classified into one of three groups according to CCT: low CCT (group A, CCT550 micrometer, n=142). In each group, we investigated the association of CCT with IOP measurement by GAT and DCT. RESULTS: The IOPs measured by GAT and DCT were significantly associated for all eyes (R=0.853, p<0.001, Pearson correlation). CCT was related with both IOP measurement by GAT and DCT with statistical significance (mixed effect model, p<0.001). However, subgroup analysis showed that CCT affected IOP measured by GAT for groups B and C, whereas it affected IOP measured by DCT only for group C. CONCLUSIONS: IOP measured by DCT was not affected by CCT in eyes with low to normal CCT, whereas this measurement was affected in eyes of high CCT range. CCT may have less effect on IOP measurements using DCT than those obtained by GAT, within a specified range of CCT.

A Wide Discrepancy between Intraocular Pressure by Applanation and Non-contact Tonometry after LASIK

PURPOSE: To report the case of a glaucoma patient with a history of LASIK surgery who presented with a wide discrepancy in intraocular pressure between the Goldmann applanation tonometry and non-contact tonometry. METHODS: A 20-year-old male glaucoma patient was referred to our clinic with a chief complaint of blurred vision in his right eye. The patient had a history of uneventful bilateral LASIK surgery. Upon our initial examination, his best-corrected visual acuity in the right eye was 0.04 and his right eye IOP was 14 mmHg by Goldmann applanation tonometry and 40 mmHg by non-contact tonometry. A slit lamp examination showed corneal epithelial edema with diffuse interface opacities. The central corneal thickness in the right eye was 587 micrometer. An ultrabiomicroscopy demonstrated an interface fluid accumulation between the LASIK flap and the stromal bed. The patient was diagnosed with juvenile open-angle glaucoma and was scheduled for a trabeculectomy. RESULTS: Seven days after trabeculectomy, the patient's vision in the right eye improved to 0.7 and his IOP was 12 mmHg by Goldmann applanation tonometry and 14 mmHg by non-contact tonometry. In addition, the corneal epithelial edema, interface opacities, and fluids had all resolved and the central corneal thickness was reduced to 489 micrometer. CONCLUSIONS: In eyes that have undergone LASIK surgery, the IOP measured by Goldmann applanation tonometry may underestimate the true pressure due to fluid accumulation under the LASIK flap. In such cases, non-contact tonometry can be a convenient and a reliable method for determining treatment plan.

Diurnal Variation of Pulse Wave Velocity Assessed Non-Invasively by Applanation Tonometry in Young Healthy Men

PURPOSE: Pulse wave velocity (PWV) is at least partially controlled by vascular tone. Vascular tone and underlying physiological processes such as sympathetic activity, plasma catecholamin, and cortisol levels have been shown to follow diurnal variations. MATERIALS AMD METHODS: Carotid-to-radial PWV was non-invasively assessed by applanation tonometry in 21 young (26.5+/-2.3 years) healthy men at three different time points (8:00hr, 12:00hr, 17:00hr) during a day. Additionally, heart rate, systolic, diastolic and mean blood pressure, and radial pulse pressure were assessed at the same time points. RESULTS: The mean PWV was significantly higher at 8:00 hr compared with the mean PWV assessed at later time points. No significant differences were found between mean PWV at 12:00 hr and at 17:00hr. When PWV was corrected for blood pressure, the difference between values at 8:00hr and 12:00hr was no longer significant. Systolic, diastolic and mean blood pressure were significantly lower at 17:00hr compared with those at 8:00hr. CONCLUSION: A small but significant diurnal variation of PWV was observed in young healthy men, which might have been caused at least partly by variations of blood pressure. This finding could be of value, when PWV is used in human research. Thus, in longitudinal investigations the measurements should be performed at similar time points in the course of a day, in order to obtain comparable data. Additionally, our observations ought to be of assistance to studies in which novel pharmacological compounds with activity on the vasculature are investigated.

Measurement of Intraocular Pressure after LASIK by Dynamic Contour Tonometry / 华中科技大学学报（医学）（英德文版）

Changes of corneal properties induced by laser in situ keratomileusis (LASIK) results in low inaccurate intraocular pressure (IOP) readings by Goldmann applanation tonometry (GAT).Before and after LASIK, the applied value of IOP, measured by dynamic contour tonometry (DCT)in comparison to GAT, was evaluated. Before and 1, 4 weeks after LASIK, the IOP in 30 cases (60 eyes) was measured by GAT and DCT respectively. The obtained results were statistically processed by SPSS11. 5 statistical software. The results showed that central corneal thickness (CCT)could affect GAT measurements but not DCT measurements. The comparison of IOP one and 4 weeks after LASIK revealed that the readings from GAT was separately decreased by 5.00±1.12 and 5.45±1. 13 mmHg as compared with those before LASIK, while those from DCT had no significant difference. It was concluded that LASIK-induced changes of CCT could influence the accuracy of GAT measurements, but had no influence on those from DCT. DCT was more beneficial to the measurements of IOP in normal eyes and those subject to LASIK surgery.

Precision measurement of the intraocular pressure in glaucoma by applanation - a new method

The drawbacks of Indentation Tonometry and the advantages of Applanation Tonometry have been discussedFor the precise measurement of the intraocular pressure, Applanation Tonometry is unsurpassed. (Conclusion)

Change of Values of Intraocular Pressures Measurements after Laser In Situ Keratomileusis

There have been reports of a reductioin in the intraocular pressure(IOP) measured with the Goldmann applanation tonometer(GAT) in eyes that have undergone excimer laser photorefractive keratectomy(PRK). The authors determined whether laser in-situ keratomileusis(LASIK) for myopia also affected GAT readings. The IOP was measured with the GAT before LASIK and 1 and 3 months postoperatively on 45 eyes of 30 patients. Measurements were performed at the central and temporal parts of the cornea; the paired Student`s t test was used for statistical analysis. The mean preoperative IOPs at the central and peripheral cornea were 13.2+/-2.5mmHg and 13.2+/-2.5mmHg, respectively. Three month after LASIK, IOPs at the central and peripheral cornea decreased to 8.9+/-1.8mmHg and 12.3+/-2.3mmHg, respectively. Similar to PRK, the GAT readings from the central cornea after LASIK for myopia were significantly lower than the preoperative IOPs(P<0.001) and the postoperative GAT readings from the peripheral cornea(p<0.001).

Effect of Excimer Laser Photorefractive Keratectomy on Goldmann Applanation Tonometry

It can be speculated that the thinned and flattened central cornea after excimer laser photorefractive keratectomy (PRK) might give a falsely low Goldmann applanation tonometer(GAT) reading. We studied 353 eyes of 264 patients who underwent PRK to determine the effect of excimer laser PRK on the accuracy of Goldmann applanation tonometry. PRK was done with a VISX 20/20 excimer laser and topical fluorometholone was used after PRK. The intraocular pressure(IOP) was measured with the GAT before surgery and 1, 3, 6, 9, and 12 months postoperatively. The mean ablation depth of the cornea was 71.4 +/- 22.0 micrometer, and the eyes were divided into three groups according to their ablation depths. The mean postoperative IOP measured with the GAT decreased as compared with the mean preoperative IOP(P<0.01). The mean postoperative IOP at 9 or 12 months was lower than that at 1, 3, or 6 months(p<0.05). The mean IOP(11.9 +/- 2.5 mmHg) at 12 months was 2.8 mmHg lower than the mean preoperative IOP(14.7 +/- 2.7 mmHg). There was no statistically significant difference in the amount of postoperative IOP decrease among the three groups.