Clinical evaluation of keratometry and computerised videokeratography: intraobserver and interobserver variability on normal and astigmatic corneas

AIMS—To evaluate intra- and interobserver variability in measurements on normal and astigmatic corneas with keratometry and computerised videokeratography.
METHODS—Keratometric readings with the 10 SL/O Zeiss keratometer and topographic maps with the TMS-1 were obtained by two independent examiners on 32 normal and 33 postkeratoplasty corneas. Inter- and intraobserver coefficients of variability (COR) for measurements of steep and flat meridian power and location, in addition to the magnitude of astigmatism, were assessed.
RESULTS—Compared with TMS-1, the 10 SL/O keratometer showed a superior repeatability in measuring normal corneas (intraobserver COR for keratometry and TMS-1 respectively: 0.22 and 0.30 D for steep meridian power; 0.18 and 0.44 D for flat meridian power; 0.26 and 0.40 D for astigmatism; 5° and 26° for steep meridian location; 5° and 13° for flat meridian location). Astigmatism intraobserver COR (0.20 D and 0.26 D for the two observers) and interobserver COR (0.28 D) of the keratometer for normal corneas was very good and not affected by observers' experience. Repeatability of the TMS-1 on normal corneas was found to be: (a) observer related, and (b) astigmatism related. A novice observer showed a much greater COR (1.62 D for astigmatism, 30° for flat meridian location) compared with the experienced examiner (0.40 D for astigmatism, 13° for flat meridian location). Higher deviation scores were observed for corneas with higher astigmatism. For the postkeratoplasty corneas, again the keratometer achieved superior reproducibility (astigmatism interobserver COR 1.12 D for keratometry, 4.06 D for TMS-1; steep meridian location interobserver COR 10° for keratometry, 34° for TMS-1).
CONCLUSION—Keratometric readings are more reproducible than topographic data both for normal and postkeratoplasty corneas. The two instruments should not be used interchangeably especially on highly astigmatic corneas. For the TMS-1, users with the same level of experience should be employed in clinical or experimental studies.

Keywords: keratometry; computerised videokeratography; astigmatic corneas     

Effect of strabismus surgery on torticollis caused by congenital superior oblique palsy in young children

Purpose:

To evaluate the outcome of strabismus surgery for congenital superior oblique palsy (SOP) in relation to correction of head tilt and hypertropia. The cohort of patients mainly involved very young children. This is the first study to use a standardized instrument to objectively measure torticollis before and after surgery.

Materials and Methods:

A non-comparative interventional case series of 13 cases of congenital superior oblique palsy with head tilt, who underwent simultaneous superior oblique tuck and inferior oblique recession between Jan 2000 and Dec 2008, were studied.

Results:

The mean duration of SOP until surgery was 36.8 months. Of the 12 unilateral cases, 8 were right-sided. Mean follow-up period was 17 months (range 7-36). The outcome was determined at the last follow-up. Mean pre-and post-operative hypertropia (p.d.) in forced primary position was 19 ± 7 and 2 ± 6, respectively (P < 0.0001). The head tilt reduced from mean of 17 ± 9 to 2 ± 2 degrees (P < 0.0001). Success, defined as hypertropia <5 PD and head tilt less than 5 degrees, was achieved in 69% (9/13. C.I. 42-88%) and 85% (11/13. C.I. 56-96%), respectively. The success rate for achieving both criteria was 61.5% (C.I. 35-88%). Five patients required additional surgery; usually a contralateral inferior rectus muscle recession, which was successful in all cases. One case developed asymptomatic Brown syndrome (7.69% - C.I. 6.7-22.2).

Conclusions:

Simultaneous superior oblique tuck and inferior oblique muscle recession can successfully treat selected cases of congenital superior oblique palsy. About one-third required an additional procedure, which led to total normalization of the head position.     

The distinguishing anthropometric features of the Saudi Arabian eyes

Purpose

Identifying the peri-ocular anthropometric measurements characteristic of Saudi Arabian eyes.

Methods

A prospective, cohort, hospital-based study.

Results

Measurements were made on 668 subjects (mean age 33.8 years; 58.7% female). The horizontal palpebral aperture was 30.1 ± 2.9 mm (mean ± SD), vertical palpebral aperture was 10.1 ± 0.85 mm, upper lid skin fold height was 3.6 ± 1.9 mm, upper lid crease height was 9.6 ± 0.8 mm, eyebrow height was 10.2 ± 2.7 mm, and intercanthal distance was 32 ± 2.7 mm. There was a statistically significant correlation between gender and eyebrow height (P = 0.001) and gender and horizontal palpebral aperture (P = 0.016), but no significant correlations were noted between any measurement and age.

Conclusions

Saudi Arabian eyes are unique in exhibiting a higher upper lid skin fold, higher lid crease.     

Choroid thickness and ocular pulse amplitude in migraine during attack

Aim

To compare the choroidal thickness and ocular pulse amplitude (OPA) measurements obtained during the attack period in migraine patients and age and gender matched control group participants using high definition optical coherence tomography (OCT).

Methods

Thirty eyes at the side of the headache of 30 subjects with a diagnosis of migraine with or without aura and unilateral migraine and 29 age and gender matched healthy participants were enrolled in this observational, cross-sectional study. OCT scans were performed to all participants. Choroidal thicknesses were measured at the fovea, 1500 μm nasal and 1500 μm temporal to the fovea. Intraocular pressure (IOP) and OPA were also measured.

Results

The choroidal thickness measurements obtained during the attack period in migraine patients were (mean±SD) 279.82±35.87, 250.05±29.49, and 239.58±27.92 and in control group were 308.20±44.97, 276.95±41.39, and 281.60±41.38 at foveal, nasal, and temporal measurement points, respectively. Choroidal thickness significantly decreased according to the control group (P<0.05) at all measured points in migraine patients during attack. IOP (mean±SD) values were 16.71±3.26 and17.40±3.19 and OPA (mean±SD) values were 2.26±0.81 and 2.64±1.03 in migraine and control groups, respectively, and did not seem to be changed (P>0.05).

Conclusions

Choroidal thickness was found to be significantly decreased in unilateral migraine patients during the attack period when compared with the control group, whereas OPA did not change. The possible implications of these findings on the association between migraine and glaucoma are discussed.     

Modified deep anterior lamellar keratoplasty for the treatment of advanced keratoconus with steep corneal curvature to help in eliminating the wrinkles in the Descemet's membrane

Aims:

To determine the clinical efficacy of modified deep anterior lamellar keratoplasty (DALK) for the treatment of advanced-stage keratoconus with steep curvature.

Materials and Methods:

In this interventional, non-comparative case series, 30 patients with advanced stages of keratoconus and curvature of more than 60 D underwent a modified DALK procedure. In this technique, after big-bubble formation, posterior stromal lamella was cut and removed 5 mm centrally (baring Descemet''s membrane completely) with posterior stromal layer remaining peripherally.

Results:

The study included 30 eyes (30 patients with a mean ± SD age of 25 ± 5.4 years). The follow-up examination was performed for all participants up to 12 months after the surgery. The mean uncorrected visual acuity (UCVA) increased from 20/800 before the surgery to a subsequent 3/10 (P =0.12). Likewise, best spectacle corrected visual acuity (BSCVA) improved, reaching 6/10 postoperatively (former quantity 20/200) (P =0.18). In addition, mean keratometry and keratometric astigmatism managed to achieve considerable improvement, from 58.8 ± 5.4 D to 46.5 ± 2.1 D and 7.8 ± 2.1 to 4.54 ± 1.54 D, respectively (P =0.52). Descemet''s membrane wrinkling was not seen in any patient postoperatively.

Conclusions:

This technique is effective in restoring acceptable vision and corneal regularity in advanced cases of keratoconus with a curvature more than 60 D who are also at risk of Descemet''s membrane wrinkling after DALK. Therefore, this procedure could prevent from Descemet membrane wrinkling in such cases.     

Peripapillary nerve fiber layer thickness changes after macular photocoagulation for clinically significant diabetic macular edema

Purpose

To evaluate the effect of macular photocoagulation (MPC) on peripapillary nerve fiber layer (PNFL) thickness measurement in patients with clinically significant diabetic macular edema (CSME).

Methods

This study was a prospective interventional case series. Patients with CSME underwent MPC. Optical coherence tomography (OCT) was used to measure the PNFL and central macular thicknesses before and 3 months after MPC.

Results

Thirty-three eyes of 25 patients with a mean age of 59.4 ± 7.2 years were included. There was no statistically significant difference between pre- and post-MPC mean best corrected visual acuity (0.35 ± 0.29 and 0.40 ± 0.23 LogMAR, respectively, P = 0.2). Mean baseline and 3 months central macular subfield thickness was 305.9 ± 90.7 and 317.5 ± 112.4 microns, respectively (P = 0.1). Peripapillary nerve fiber layer thickness was 105.7 ± 10.0 before and 106.1 ± 9.9 three months after MPC (P = 0.7). No significant differences were found between pre and post MPC measurements in temporal, nasal, inferior and superior nerve fiber layer thickness in each quadrant around optic nerve head (P > 0.05).

Conclusions

Macular photocoagulation has no statistically significant effect on PNFL thickness measurements in patients with CSME.     

Contralateral lateral rectus muscle recession in patients with Duane retraction syndrome type 3

Aims

The aim of this study was to evaluate the motor, sensory, functional, and head posture results of recession of the lateral rectus muscle contralateral to the involved eye in patients with exotropic Duane retraction syndrome (DRS) type 3.

Methods

This was a retrospective, longitudinal, observational study of a consecutive clinical case series. Of the 11 patients with DRS type 3 operated on at a tertiary medical center from 1977 to 2012, 8 underwent recession of the lateral rectus muscle contralateral to the involved eye (with combined Y-splitting of ipsilateral lateral rectus muscle in 3 of them). Full ophthalmic, orthoptic, and neurological examination was performed before and after surgery. Main outcome measures included intragroup changes in motor misalignment, abnormal head turn, ocular upshoot, and stereopsis.

Results

Mean patient age was 8.75±3.1 years at surgery. Mean exodeviation for distance was −17.3±3.5 prism diopters (PD) preoperatively and −4.0±6.1 PD postoperatively; corresponding values for near were −23.1±7.2 PD and −5.9±8.7 PD. Motor deviation improved by 77% for distance (P=0.017) and 74.5% for near (P=0.01). In 7/8 patients, the postoperative residual exodeviation (distance and near) was <8.0 PD. There was an 80% improvement in head turn, from 15.3±4° before surgery to 3.1±5.0° after (P=0.01). Stereopsis improved significantly in 6/8 patients. Findings remained stable during follow-up (mean duration 35.9±50.8 months, range 5–132 months).

Conclusions

Contralateral lateral rectus muscle recession appears to be a promising technique for the treatment of moderate unilateral DRS type 3, with patients showing significant motor and functional improvement and a decrease in head turn.     

Decision making nomogram for intrastromal corneal ring segments in keratoconus

Purpose:

To create a nomogram for the insertion of intrastromal corneal ring segments (ICRS) (Intacs^® ) in eyes with keratoconus.

Setting:

Tertiary eye care center in South India.

Materials and Methods:

This prospective, non-randomized, interventional case series used a self-designed decision-making nomogram for the selection of ICRS in keratoconus patients based on the centration of the cone, mean refractive spherical equivalent (MRSE), and mean keratometry (Km) values. The 3, 6, and 12 months clinical outcomes were compared to historical controls. Primary endpoints were improvement in uncorrected and best-corrected vision and change in the keratometric values.

Results:

Group A comprised of 52 eyes of 50 patients that followed the nomogram, while Group B comprised of 25 eyes of 23 non-nomogram historical controls matched for baseline parameters. In Group A, the uncorrected distance visual acuity (UDVA) improved from 0.16 ± 0.15 to 0.25 ± 0.16 (P < 0.001), corrected distance visual acuity (CDVA) from 0.58 ± 0.2 to 0.69 ± 0.21 (P = 0.022), MRSE from -5.41 ± 4.94 to -1.71 ± 2.88 (P < 0.001), Km from 51.77 ± 5.45 to 48.63 ± 4.37 (P < 0.001), and astigmatism reduced from 5.86 ± 2.61 to 4.91 ± 2.72 diopters (P < 0.001).In Group B, improvement in the average MRSE was from -6.44 ± 5.32 to -3.26 ± 2.82 (P < 0.013) and in the average Km from 53.64 ± 5.32 to 50.31 ± 5.02 (P < 0.001). Other parameters did not improve significantly. A statistically significant difference was present in the percentage of patients achieving a good clinical outcome between the two groups (P < 0.001; Chi-square).

Conclusion:

The nomogram provides a means to choose the appropriate ICRS, hence improving the outcome in patients with keratoconus.     

Evaluation of intrastromal corneal ring segments for treatment of keratoconus with a mechanical implantation technique

Purpose:

To evaluate the clinical outcomes of intrastromal corneal ring segment (ICRS) implantation in patients with keratoconus using a mechanical implantation technique.

Materials and Methods:

Thirty eyes of 17 patients with keratoconus were enrolled. ICRSs (Keraring) were implanted after dissection of the tunnel using Tunc''s specially designed dissector under suction. A complete ophthalmic examination was performed, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent, keratometric readings, inferosuperior asymmetry index (ISAI), and ultrasound pachymetry. All 3-, 6-, and 12-month follow-ups were completed, and statistical analysis was performed.

Results:

The mean preoperative UDVA for all eyes was 1.36 ± 0.64 logMAR. At 12 months, the mean UDVA was 0.51 ± 0.28 logMAR (P = 0.001), and the mean preoperative CDVA was 0.57 ± 0.29 logMAR, which improved to 0.23 ± 0.18 (P = 0.001) at 1 year. There was a significant reduction in spherical equivalent refractive error from –6.42 ± 4.69 diopters (D) preoperatively to –1.26 ± 1.45 D (P = 0.001) at 1 year. In the same period, the mean K-readings improved from 49.38 ± 3.72 D to 44.43 ± 3.13 D (P = 0.001), and the mean ISAI improved from 7.92 ± 3.12 to 4.21 ± 1.96 (P = 0.003). No significant changes in mean central corneal thickness were observed postoperatively. There were no major complications during and or after surgery.

Conclusion:

ICRS implantation using a unique mechanical dissection technique is a safe and effective treatment for keratoconus. All parameters improved by the 1-year follow-up.     

Evaluation of the role of timolol 0.1% gel in myopic regression after laser in situ keratomileusis

Purpose

To evaluate the efficacy of the concomitant administration of antiglaucoma medications namely timolol 0.1% gel in cases with myopic regression after myopic laser in situ keratomileusis (LASIK).

Design

Prospective observational clinical trial.

Subjects and methods

Ninty five eyes of 75 patients were included in this study prospectively. The mean myopic regression was −1.29 ± 0.83 diopters (range −0.5 to −4.62) after myopic LASIK. The eyes were divided into two groups: 50 eyes administrated timolol 0.1% gel once daily for 12 months (treated group), and 45 eyes were age matched (control group). We assessed the amounts of myopic regression in terms of changes in the refraction (spherical equivalent and astigmatism), intraocular pressure (IOP), pachymetry and the refractive power of the cornea measurements for all participants.

Results

The refractive error and visual acuity were similar between the two groups at baseline. The treated group had an improvement in spherical equivalent significantly from −1.29 ± 0.83 to −0.94 ± 1.07 diopters (P = 0.012). Astigmatism was changed from −0.94 ± 0.53 to −0.86 ± 0.60 diopters but this change was not statistically significant (P = 0.20). The IOP was decreased significantly from 12.6 ± 1.9 to 9.0 ± 1.1 mm Hg (P < 0.001). Central corneal thickness was changed from 425.6 ± 19.86 to 429 ± 18.1 μm but not statistically significant (P = 0.56). The central corneal power decreased significantly from 37.2 ± 1.8 to 36.4 ± 1.3 diopters (P < 0.05).

Conclusion

Timolol 0.1% gel was effective for reduction and improvement of myopic regression especially the spherical errors after myopic LASIK.     

Transitioning to intravitreal aflibercept following a previous treat-and-extend dosing regimen in neovascular age-related macular degeneration: 24-month results

Purpose:

To evaluate frequency of injections, visual and anatomical outcomes of neovascular age-related macular degeneration (nAMD) patients transitioned to intravitreal aflibercept after failure to extend treatment interval beyond 8 weeks with prior intravitreal bevacizumab or ranibizumab.

Methods:

Retrospective review of patients with nAMD switched to aflibercept following ≥6 prior intravitreal ranibizumab or bevacizumab injections at 4–8-week intervals. Three monthly aflibercept injections were given followed by a treat-and-extend dosing regimen.

Results:

Twenty-one eyes of 18 patients who had received a mean of 23.8±18.8 (mean±SD; range 6–62) prior ranibizumab or bevacizumab injections were included. Over a mean follow-up of 24 months after the transition, 9.2±2.9 (range 4–21) aflibercept injections were required. Interval between aflibercept injections increased to 57.3 days (range 35–133 days), as compared with 37±6.1 days (range 29–54 days) with the prior agents (P=0.01). Mean best-corrected visual acuity was preserved (0.42±0.31 vs 0.42±0.23 logMAR; P=0.2). Mean OCT central subfoveal thickness (292.1±83.2 μm to 283.6±78.6 μm; P=0.4) and mean macular volume (7.9±0.95 mm³ to 7.67±0.94 mm³; P=0.16) remained stable.

Conclusion:

Patients requiring treatment more frequently than every 8 weeks with ranibizumab and bevacizumab were transitioned to >8-week treatment interval with aflibercept while maintaining the anatomic and visual gains.     

Effect of Head Position and Tube Entry on Corneal Endothelial Cells in Patients with Glaucoma Drainage Implants: A Cross-sectional Study

PurposeTo investigate the effect of head tilt on the tube position of the Ahmed glaucoma valve (AGV) implanted in patients with glaucoma and to assess how the head tilt-induced alterations of tube parameters and the level of tube entry influence corneal endothelial cell density (ECD).MethodsA total of 29 eyes of 26 patients with AGV implantation were included. Tube-cornea distance, tube-cornea angle, and intracameral tube length were measured using anterior segment optical coherence tomography in three different head positions (neutral, 30° temporalward tilt, and 30° nasalward tilt). The tube entry was assessed using static gonioscopy. ECD was measured using specular microscopy before and after surgery.ResultsThe mean tube-cornea distance, tube-cornea angle, and intracameral tube length (neutral: 0.87 ± 0.39 mm, 30.56 ± 5.89˚, and 3.10 ± 0.82 mm, respectively) decreased with head tilts (temporalward: 0.82 ± 0.39 mm, 29.27 ± 5.82˚, and 3.04 ± 0.82 mm, respectively; nasalward: 0.83 ± 0.40 mm, 29.61 ± 6.04˚, and 3.05 ± 0.81 mm, respectively; all p < 0.01). The multivariate analyses found age and the tube insertion level to be associated with postoperative changes in the central ECD (p = 0.039 and 0.013, respectively), and the postoperative follow-up period and tube insertion level to be associated with the difference between the inferonasal and superotemporal ECDs (p = 0.034 and 0.007, respectively).ConclusionsMild alterations of head positions induced changes in the intracameral tube positions of AGV implants; nevertheless, it did not significantly affect ECD loss. However, the eyes with tubes inserted anteriorly to Schwalbe’s line may be more susceptible to corneal ECD loss.     

Flap characteristics,predictability, and safety of the Ziemer FEMTO LDV femtosecond laser with the disposable suction ring for LASIK

Aims

The outcomes of laser-assisted in situ keratomileusis (LASIK) operations performed with the Classic FEMTO LDV femtosecond laser using the plastic single-use suction ring (Ziemer Ophthalmic Systems) and the Allegretto Wave Concerto 500 Hz excimer laser (Wavelight AG) are presented in terms of accuracy, predictability, and safety of the operation.

Methods

A FEMTO LDV plastic suction ring was used for flap creation in 342 eyes of 179 patients. The intended flap thickness was 90 μm. The size of the suction ring varied from 9.0 to 10.0 mm. Flap dimensions were measured and correlated to preoperative characteristics.

Results

Mean flap thickness was very constant, 89.6±2.0 μm (range 84–97). In 163 bilateral operations, the second flap was 1.1 μm thinner than the one cut first (P<0.0001). Mean flap diameter was 9.4±0.2 mm (range 8.1–9.9). Mean hinge length was 3.9±0.2 mm (range 3.0–4.2). In hyperopic eyes, flap thickness correlated negatively with keratometric power K₁ and flap diameter. In hyperopic eyes, flap diameter correlated positively with spherical equivalent refraction and with keratometric power K₁ as well as hinge length both in myopic and hyperopic eyes. Complications were reported in 12 (3.5%) eyes. Complications were very mild and none of them prevented further refractive laser treatment. Two Snellen lines of corrected distance visual acuity were lost in one (0.3%) eye.

Conclusion

The FEMTO LDV plastic single-use suction rings yielded accurate and reproducible flaps and were safe for the creation of thin corneal flaps.     

Posture-Dependent Collapse of the Optic Nerve Subarachnoid Space: A Combined MRI and Modeling Study

PurposeWe hypothesize that a collapse of the optic nerve subarachnoid space (ONSAS) in the upright posture may protect the eyes from large translamina cribrosa pressure differences (TLCPD) believed to play a role in various optic nerve diseases (e.g., glaucoma). In this study, we combined magnetic resonance imaging (MRI) and mathematical modeling to investigate this potential ONSAS collapse and its effects on the TLCPD.MethodsFirst, we performed MRI on six healthy volunteers in 6° head-down tilt (HDT) and 13° head-up tilt (HUT) to assess changes in ONSAS volume (measured from the eye to the optic canal) with changes in posture. The volume change reflects optic nerve sheath (ONS) distensibility. Second, we used the MRI data and mathematical modeling to simulate ONSAS pressure and the potential ONSAS collapse in a 90° upright posture.ResultsThe MRI showed a 33% decrease in ONSAS volume from the HDT to HUT (P < 0.001). In the upright posture, the simulations predicted an ONSAS collapse 25 mm behind lamina cribrosa, disrupting the pressure communication between the ONSAS and the intracranial subarachnoid space. The collapse reduced the simulated postural increase in TLCPD by roughly 1 mm Hg, although this reduction was highly sensitive to ONS distensibility, varying between 0 and 4.8 mm Hg when varying the distensibility by ± 1 SD.ConclusionsThe ONSAS volume along the optic nerve is posture dependent. The simulations supported the hypothesized ONSAS collapse in the upright posture and showed that even small changes in ONS stiffness/distensibility may affect the TLCPD.     

High intravitreal TGF-β1 and MMP-9 levels in eyes with retinal vein occlusion

Purpose

Vascular endothelial growth factor is a leading target to reduce macular oedema and improve visual acuity in patients with retinal vein occlusion (RVO), whereas the role of vascular destabilizing and fibroproliferative transforming growth factor (TGF)-β1 and matrix metalloproteinases (MMP)-2 and -9 in pathological manifestations of RVO is anticipated but less studied.

Methods

Undiluted vitreous samples were collected from three central RVO and one branch RVO eyes, all with neovascularization and fibrosis-related sight-threatening complications of RVO. Undiluted vitreous samples of 40 eyes operated due to non-ischemic condition either macular hole or pucker were used as controls. Growth factor and protease concentrations were measured by ELISA and gelatin zymography.

Results

Vitreous concentrations of TGF-β1 (92.0±17.4 pg/ml vs 18.3±27.0 pg/ml, mean±SD; P=0.002) and MMP-9 (847.9±1196.4 AU/ml vs 87.7±174.0 AU/ml; P=0.010) were higher in the eyes with ischemic RVO than in the controls.

Conclusions

High intravitreal levels of TGF-β1 and MMP-9 are found in RVO eyes having neovascular and fibrosis manifestation. Further studies are warranted to elucidate whether targeting TGF-β1 and MMP-9 could be beneficial in patients with ischemic RVO.     

Agreement between Two Swept-Source Optical Coherence Tomography Biometers and a Partial Coherence Interferometer

PurposeTo evaluate the level of agreement between ANTERION (Heidelberg Engineering, Heidelberg, Germany), OA-2000 (Tomey, Nagoya, Japan), and IOLMaster 500 (Carl Zeiss AG, Jena, Germany).MethodsFifty-one eyes of 51 patients were included in the study. Flat keratometry (K) and steep K, vector component of astigmatism (Jackson cross-cylinder at 0° and 90° [J₀] and Jackson cross-cylinder at 45° and 135° [J₄₅]), anterior chamber depth, and axial length were compared using the three devices. Repeated measures analysis of variance was conducted to compare the mean values of the biometrics. Pearson correlation test was conducted to analyze the correlations of the measured values, and a Bland-Altman plot was used to assess the agreement between the three devices. The predicted intraocular lens power of each device was compared to the others using the SRK/T, Haigis, Barrett Universal II, and Kane formulas.ResultsAll K values measured using ANTERION were flatter than those of other instruments. However, good agreement was observed for flat K (ANTERION - OA-2000; 95% limits of agreement [LoA], 0.86 diopters [D]) and steep K (ANTERION - OA-2000; 95% LoA, 0.93 D) and OA-2000 - IOLMaster 500 (95% LoA, 0.93 D). J₀ and J₄₅ vector components of astigmatism were not statistically different; however, the agreements were poor between the devices (95% LoA ≥1.97 D). Anterior chamber depth values of ANTERION and OA-2000 were interchangeable (95% LoA, 0.15 mm). The axial length showed a high agreement (95% LoA ≤0.17 mm) among the three devices. The predicted intraocular lens powers of the three devices were not interchangeable regardless of formulas (95% LoA ≥1.04 D).ConclusionsSignificant differences in ocular biometrics were observed between ANTERION and the other two devices. This study demonstrated that only axial length showed good agreement among devices.     

Accuracy of axial length measurements from immersion B-scan ultrasonography in highly myopic eyes

AIM:To evaluate the accuracy of axial length (AL) measurements obtained from immersion B-scan ultrasonography (immersion B-scan) for intraocular lens (IOL) power calculation in patients with high myopia and cataracts.METHODS:Immersion B-scan, contact A-scan ultrasonography (contact A-scan), and the IOLMaster were used to preoperatively measure the AL in 102 eyes from 102 patients who underwent phacoemulsification and IOL implantation. Patients were divided into two groups according to the AL:one containing patients with 22 mm≤AL<26 mm(group A) and the other containing patients with AL≥26 mm (group B). The mean error (ME) was calculated from the difference between the AL measurement methods predicted refractive error and the actual postoperative refractive error.RESULTS:In group A, ALs measured by immersion B-scan (23.48±1.15) didn’t differ significantly from those measured by the IOLMaster (23.52±1.17) or from those by contact A-scan (23.38±1.20). In the same group, the standard deviation (SD) of the mean error (ME) of immersion B-scan (-0.090±0.397 D) didn’t differ significantly from those of IOLMaster (-0.095±0.411 D) and contact A-scan (-0.099±0.425 D). In group B, ALs measured by immersion B-scan (27.97±2.21 mm) didn’t differ significantly from those of the IOLMaster (27.86±2.18 mm), but longer than those measured by Contact A-scan (27.75±2.23 mm, P=0.009). In the same group, the standard deviation (SD) of the mean error (ME) of immersion B-scan (-0.635±0.157 D) didn’t differ significantly from those of the IOLMaster (-0.679±0.359 D), but differed significantly from those of contact A-scan (-0.953±1.713 D, P=0.028).CONCLUSION:Immersion B-scan exhibits measurement accuracy comparable to that of the IOLMaster, and is thus a good alternative in measuring AL in eyes with high myopia when the IOLMaster can’t be used, and it is more accurate than the contact A-scan.     

The applicability of correction factor for corneal thickness on non-contact tonometer measured intraocular pressure in LASIK treated eyes

Purpose

To determine the applicability of central corneal thickness (CCT) based correction factor for non-contact tonometer (NCT) measured intraocular pressure (IOP) readings.

Method

A prospective, non-randomized study involved 346 eyes of 173 consecutive patients with age ⩾21 years undergoing laser-assisted in situ keratomileusis (LASIK) for myopia and/or myopic astigmatism. The CCT and IOP were measured before and after the LASIK procedure. The IOP pre and post-LASIK was compared after applying the correction factor for CCT. Patients not completing the 3 month postoperative follow-up were excluded.

Results

The median spherical equivalent before undergoing LASIK was −4.25D (inter-quartile range, −3.25D). The mean preoperative CCT was 536.82 ± 33.71 μm which reduced to 477.55 ± 39.3 μm (p < 0.01) post-LASIK. The mean IOP reduced from a preoperative value of 14.6 ± 2.32 mmHg to 10.64 ± 2.45 mmHg postoperatively (p < 0.01). On applying correction for the corneal thickness, the pre and postoperative IOP was 15.14 ± 2.8 mmHg and 15.37 ± 2.65 mmHg (p = 0.06) respectively with a strong positive correlation (r = 0.7, p < 0.01). Three hundred eyes (86.7%) had an absolute difference in IOP of less than 3.0 mmHg post-CCT correction which is within the retest variability of NCT. Only 46 eyes (13.3%) had an absolute difference of more than 3.0 mmHg.

Conclusion

The modified Ehler’s correction algorithm used in this study can be effectively applied in the normal IOP range in a majority of patients.     

Effects of head elevation on intraocular pressure in healthy subjects: raising bed head vs using multiple pillows

Purpose

To evaluate the effects of different methods of head elevation on intraocular pressure (IOP) in healthy young subjects.

Methods

Twenty-four healthy young Korean subjects were included in this prospective observational study. The IOP measurements were taken with the subjects in the sitting position and in the supine positions with the head flat and 30° up using two different methods: (1) raising the bed head and (2) using multiple pillows. IOP was measured using Tonopen AVIA in both eyes 10 min after assuming each position in a randomized sequence. The Wilcoxon signed-rank test was used to compare the IOP by changing the methods of head elevation.

Results

Mean IOP of both eyes when sitting was lower than that measured in the supine position with head flat (P=0.001). Compared with that measured in the supine position with head flat, the mean IOP was lower when measured in the supine position with the head kept 30 ° up by bed head elevation (P=0.001), whereas the mean IOP was not significantly different when measured in the supine position with the head elevated using multiple pillows (right eye, P=0.061; left eye, P=0.089).

Conclusion

In normal subjects, IOP was lower when measured in the supine position with the head kept up by the bed head elevation compared with that measured when lying flat. However, such head-up position-induced IOP reduction was not found when the head was kept up using multiple pillows. These findings suggest that elevating the head using multiple pillows may not help to reduce IOP in the supine posture.     

Selective laser trabeculoplasty (SLT) vs other treatment modalities for glaucoma: systematic review

Purpose

Systemic review to compare selective laser trabeculoplasty (SLT) to other glaucoma treatment options in terms of their intraocular pressure (IOP)-lowering effect.

Methods

Searches of the following databases were performed: PubMed, Cochrane Central Register of Controlled Trials, Ovid, EMBASE, metaRegister of Controlled Trials, and ClinicalTrials.gov. Only randomised controlled trials (RCTs) published in peer-reviewed journals comparing SLT to other glaucoma treatment options were considered. The main outcome measure was the change in IOP from baseline.

Results

An initial search of PubMed identified 23 RCTs with 17 meeting the inclusion criteria. Nine RCTs compared 180° SLT to 180° argon laser trabeculoplasty (ALT) and one trial compared 360° SLT to 360° ALT, all reporting no difference in terms of IOP reduction from baseline. One RCT reported better outcomes with SLT at 1 year but this effect regressed at 2 years. Three trials compared 360° SLT to medical therapy and found no difference between the two treatment options. One trial found greater IOP reduction with latanoprost vs 90° and 180° SLT, and greater IOP reduction with 180° and 360° SLT versus 90° SLT, however no differences were found between 360° SLT versus latanoprost or 360° vs 180° SLT. Two trials compared 180° SLT to 360° SLT finding no difference in IOP reduction. Two trials compared 180° SLT to 90° SLT, one finding no significant difference and one finding greater IOP reduction with 180° SLT over 90° SLT. One trial compared excimer laser trabeculotomy (ELT) to 180° SLT, finding no differences in IOP reduction up to 3 months follow-up but greater IOP reduction with ELT at time intervals between 9 and 24 months. There were no RCTs identified that compared SLT to surgery.

Conclusion

In terms of the IOP lowering effect, there is no difference between SLT and ALT. Three trials indicate no difference between 360° SLT and medical therapy, with one of the trials indicating greater IOP reduction with latanoprost over 90° and 180° SLT. Three trials indicate no difference between 180° SLT and 360° SLT. It is inconclusive whether 90° is less efficacious than 180° SLT. One trial reports greater IOP reduction with ELT over 180° SLT in the long term.