Electroretinography in streptozotocin diabetic rats following acute intraocular pressure elevation

Background

We consider whether pre-existing streptozotocin induced hyperglycemia in rats affects the ability of the eye to cope with a single episode of acute intraocular pressure (IOP) elevation.

Methods

Electroretinogram (ERG) responses were measured (?6.08 to 1.92 log cd.s.m^?2) in anaesthetized (60:5 mg/kg ketamine:xylazine) dark-adapted (>12 h) adult Sprague–Dawley rats 1 week after a single acute IOP elevation to 70 mmHg for 60 min. This was undertaken in rats treated 11 weeks earlier with streptozotocin (STZ, n?=?12, 50 mg/kg at 6 weeks of age) or citrate buffer (n?=?12). ERG responses were analyzed to derive an index of photoreceptor (a-wave), ON-bipolar (b-wave), amacrine (oscillatory potentials) and inner retinal (positive scotopic threshold response, pSTR) function.

Results

One week following acute IOP elevation there was a significant reduction of the ganglion cell pSTR (?35?±?11 %, P?=?0.0161) in STZ-injected animals. In contrast the pSTR in citrate-injected animals was not significant changed (+16?±?14 %). The negative component of the STR was unaffected by IOP elevation in either citrate or STZ-treated groups. Photoreceptoral (a-wave, citrate-control +4?±?3 %, STZ +4?±?5 %) and ON-bipolar cell (b-wave, control +4?±?3 %, STZ +4?±?5 %) mediated responses were not significantly affected by IOP elevation in either citrate- or STZ-injected rats. Finally, oscillatory potentials (citrate-control +8?±?23 %, STZ +1?±?17 %) were not reduced 1 week after IOP challenge.

Conclusions

The ganglion cell dominated pSTR was reduced following a single episode of IOP elevation in STZ diabetic, but not control rats. These data indicate that hyperglycemia renders the inner retina more susceptible to IOP elevation.     

Learning effect of dark adaptation among normal subjects

Purpose

To examine and quantify any change in the dark adaptation (DA) function of normal subjects due to learning effect on test?Cretest.

Methods

Sixteen normal subjects (12 women, four men) whose ages ranged between 24 and 52?years (mean 34.6?±?6.7?years) were studied. The interval period between test and retest ranged between 0.92 and 2.37?months (mean 1.38 ± 0.40?months). DA was measured with a Goldmann?CWeekers (GW) dark adaptometer, and subjects were pre-adapted using a light intensity of 2,700?cd/m² Ganzfeld background for 5 minutes. Exponential non-linear regression analysis was used to determine seven parameters of DA function. These were time of cone?Crod break, cone and rod final thresholds, and magnitude of change and time constant of the cone and rod limbs.

Results

The mean cone?Crod break time with 95% confidence intervals (CI) was 0.098 (CI: ?0.527, 0.330) minutes faster on retest (p?=?0.630)). Fourteen of the 16 subjects demonstrated an increase or 'worsening' of their final cone and rod thresholds on the second visit. The mean final threshold differences on retest for the cone limb was 0.105 (CI: 0.032, 0.179) log cd/m² (p?=?0.008) and 0.093 (CI: ?0.039, 0.225,) log cd/m² (p?=?0.155) for the rod limb. The magnitude of change for the cone limb was 0.016 (CI: ?0.122, 0.155) log cd/m² (p?=?0.805) and ?0.196 (CI: ?0.435, 0.827) log cd/m2 (p?=?0.518) for the rod limb, while the time constant on retest for the cone limb was ?0.021 (CI: -0.128, 0.169) minutes, (p?=?0.770) and 0.276 (CI: -0.424, 0.976) minutes (p?=?0.410) for the rod limb.

Conclusions

None of the DA parameters that were examined demonstrated a learning effect of clinical significance between test and retest. None of the changes in mean from test to retest for the seven parameters were found to be statistically significant, and the changes were clinically negligible. Therefore, any change among patients that may occur in dark adaptation between a visit interval may be considered real, and not due to the effect of learning.     

Assessment of age changes and repeatability for computer-based rod dark adaptation

Purpose

To characterize the rate of rod-mediated sensitivity decline with age using a PC-driven cathode ray tube (CRT) monitor. To provide data regarding the repeatability of the technique.

Methods

Dark adaptation was monitored for 30 min following a minimum 30 % pigment bleach, using a white 1° stimulus (modulated at 1 Hz), presented 11° below fixation on a CRT monitor. Thirty-three subjects with no ocular pathology and normal fundus photographs were divided into two groups: older (≥45, n?=?16) and younger (<45, n?=?17).

Results

Rod recovery was assessed using component S2 of dark adaptation. S2 was significantly slower in the older (0.19?±?0.03 log cd.m^?2.min^?1) compared with the younger group (0.23?±?0.03 log cd.m^?2.min^?1, t?=??4.05, p?<?0.0003), despite no difference in visual acuity and fundus appearance. Faster rates of S2 recovery were correlated with lower threshold at 30 min (T₃₀) (r?=??0.49). Correlation coefficients between first and second measurements for S2 and T₃₀ were 0.49 (p?<?0.009) and 0.84 (p?<?0.0001) respectively. The coefficient of repeatability was 0.07 log cd.m^?2.min^?1 for S2 and 0.35 log cd.m^?2 for T₃₀. The coefficients of variation for S2 and T₃₀ were 15 % and 10 % respectively.

Conclusions

Dark adaptation is slowed in normal ageing. CRT-based dark adaptometry is easily implemented and highly repeatable. The technique described in this article would be useful for documenting visual changes in future clinical trials assessing retinal health in the older eye with and without ocular pathology.     

Electrophysiologic evaluation of retinal function in patients with psoriasis and vitiligo

Purpose

To investigate the relation between psoriasis and vitiligo with the electrophysiologic function of the retinal photoreceptors.

Methods

Patients with psoriasis or vitiligo referred for PUVA therapy were enrolled. Complete eye examination was performed. Patients with any drug or familial history or abnormal eye examination that might affect the retinal function were excluded. Standardized full-field electroretinogram (ERG) elicited with Ganzfeld stimuli using the commercial ERG system (Retiport32; Roland Consult) according to International Society for Clinical Electrophysiology of Vision guidelines was performed. The outcome measures were the difference between the mean rod response, standard combined response, single-flash cone response and 30-Hz flicker wave amplitudes of the patients and normal population.

Results

Seventy-six eyes of 38 patients (vitiligo: 21; psoriasis: 17) and 40 eyes of 20 normal subjects were enrolled in this study. The mean age of patients was 31.3 ± 11.3 years (range 16–54 years). Twenty-two patients (58 %) were female. The mean rod response b-wave, standard combined a- and b-waves, single-flash cone response b-wave and the 30-Hz flicker (N1-P1) amplitudes were significantly lower than the normal population in the same range of age as the study group. There was no significant difference between the patients with vitiligo and those with psoriasis in all wave amplitudes (P = 0.094).

Conclusion

This study showed that overall retinal electrophysiologic function in patients with vitiligo or psoriasis is significantly impaired compared with normal population, independent of age and sex.     

The association between dark adaptation and macular pigment optical density in healthy subjects

Purpose

To investigate whether macular pigment optical density (MPOD) is related to dark adaptation in healthy subjects.

Methods

Dark adaptation was measured after a minimum 30 % pigment bleach in 33 subjects (aged 15–68), using a white 1° stimulus presented 11° below fixation on a cathode ray tube monitor. The luminance range of the monitor was extended using neutral density filters. A heterochromatic flicker photometry based instrument (MPS 9000) was used to measure MPOD.

Results

The average MPOD for the whole group was 0.37 ±0.21 optical density units. Subjects with lighter irides had on average 40 % lower MPOD compared to those with darker irides (0.3 ± 0.20 vs 0.5 ± 0.19). Group mean MPOD was weakly associated with second (r?=?0.32, p?=?0.07) and third rod-mediated recovery rates (r?=?0.31, p?=?0.08) and with the rod threshold (r?=??0.24, p?=?0.18) 30 min after the onset of bleach. MPOD was unrelated to cone time constant (r?=??0.02, p?=?0.91), cone threshold (r?=??0.01, p?=?0.96), rod–cone break (r?=?0.13, p?=?0.45) or the rod–rod break (r?=?0.11, p?=?0.52). The second rod-mediated recovery rate (S2) for the lower 10th percentile of MPOD (n?=?4) was 0.18 log cd.m^-2.min^-1 and 0.24 log cd.m^-2.min^-1 for the upper 10th percentile (n?=?4). The two groups were significantly different (t?=??2.67, p?=?0.037).

Conclusions

We report a statistically significant difference between subjects falling in the 10th percentile extremes of MPOD and rod-mediated but not cone-mediated sensitivity recovery. Further investigation into the relationship between MPOD and rod function is warranted, particularly extending the work to encompass those with low MPOD and poor night vision.     

Comparison of dynamic contour tonometry and Goldmann applanation tonometry in relation to central corneal thickness in primary congenital glaucoma

Background

To compare intraocular pressure (IOP) measurements obtained with dynamic contour tonometer (DCT) and Goldmann applanation tonometer (GAT), and to investigate their relationship to central corneal thickness (CCT) in primary congenital glaucoma (PCG) eyes.

Methods

Thirty-one eyes of 31 PCG patients (25.7?±?7.2 years old) were examined. PCG was defined as elevated IOP, enlarged corneal diameter (buphthalmos), Haab’s striae and abnormal findings at gonioscopy. The mean of three measurements of GAT, DCT (quality scores 1 and 2), and CCT were obtained and assessed for agreement by means of Bland–Altman plot and for Spearman correlation test.

Results

Mean CCT was 534?±?72.3 μm (range: 430 to 610 μm). Mean IOP measurements were 15.1?±?4.2 mmHg (range: 5.5 to 22.7 mmHg) for DCT and 14.5?±?5.6 mmHg (range: 7.0 to 34.0 mmHg) for GAT (P?=?0.244). Spearman correlation tests showed that IOP difference (DCT ? GAT) was not correlated with CCT (r ²?=?0.023, P?=?0.417). IOP measurements by DCT were weakly but statistically correlated with those obtained with GAT (r²?=?0.213, P?=?0.0089). Bland–Altman analysis revealed poor agreement between DCT and GAT readings, considering the 95 % confidence intervals of ±10.45 mmHg.

Conclusions

The differences between DCT and GAT readings were not influenced by CCT in this series of patients. Considering the weak correlation and the poor agreement observed between GAT and DCT measurements and that they both may be affected by corneal biomechanical changes, these methods should not be used interchangeably, and may possibly give no meaningful IOP values in PCG patients.     

Retinal function and PKC alpha expression after focal laser photocoagulation

Purpose

To examine the effects of focal laser photocoagulation on general and local retinal function and to relate electrophysiological findings with changes in protein kinase C (PKC) alpha expression.

Methods

Twelve rabbits were treated with 70 spots of laser photocoagulation in the central cone-rich retina. The operated eyes were investigated with electroretinography (full-field ERG and multifocal electroretinography, mfERG) preoperatively and at 1, 3, and 5 weeks after surgery. The expression of PKC alpha was examined at all three time points using immunohistochemistry, and PKC alpha mRNA levels were quantified using real-time polymerase chain reaction (PCR). Immunohistochemistry for glial fibrillary acidic protein (GFAP) and hematoxylin and eosin staining was employed to monitor the extent and dynamics of the morphological response.

Results

The full-field ERG revealed a significant increase in b-wave amplitudes derived from the isolated rod response (blue light) at all three time points after surgery (p?Conclusions Focal laser treatment in the rabbit eye induces local and wide-spread alterations in both rod- and cone-mediated retinal function in the form of supernormal b-wave amplitudes in the full-field ERG and increased latency in the mfERG. The electrophysiological abnormalities are accompanied by a progressive down-regulation of the PKC alpha isoenzyme in rod bipolar cells, reaching far beyond the treated area. PKC alpha is down-regulated directly by impaired protein synthesis, and also possibly indirectly by protein consumption related to GFAP up-regulation. The results indicate that focal laser photocoagulation interferes with PKC-alpha-mediated inhibitory regulation of inner retinal signal transmission.     

Long-term intraocular pressure changes after vitrectomy for epiretinal membrane and macular hole

Background

To investigate long-term intraocular pressure (IOP) changes after vitrectomy for epiretinal membrane (ERM) or macular hole (MH).

Methods

We retrospectively reviewed the medical records of 57 eyes with ERM and 61 eyes with MH that underwent vitrectomy. IOP levels and changes at 1, 3, 6, 12 months, and the final visit from baseline were evaluated in vitrectomized eyes and non-vitrectomized fellow eyes.

Results

In the ERM group, the mean follow-up period was 29.3 months; the mean preoperative IOP in the operated eyes was 12.9?±?2.5 mmHg and the final IOP was 13.2?±?2.9 mmHg. In the MH group, the mean follow-up period was 25.6 months; the mean preoperative IOP in the operated eyes was 13.3?±?2.5 mmHg and the final IOP was 14.0?±?3.2 mmHg. The mean final IOP of the fellow unoperated eyes was 13.0?±?2.5 mmHg in the ERM group and it was 12.9?±?3.2 mmHg in the MH group. A significant difference was found between the operated eyes and fellow eyes at the final visit in the MH group (P?<?0.01) but not in the ERM group (P?=?0.40). MH group was significantly at high risk of IOP increase after vitrectomy (P?<?0.01).

Conclusions

IOP increase after vitrectomy was found in some eyes with MH during long-term follow-up but it was unlikely in eyes with ERM.     

Retinal and optic nerve evaluation by optical coherence tomography in adults with obstructive sleep apnea–hypopnea syndrome (OSAHS)

Objective

To assess the peripapillary retinal nerve fiber layer (RNFL) thickness, optic nerve head (ONH) morphologic parameters, and macular thickness and volume in patients affected by obstructive sleep apnea–hypopnea syndrome (OSAHS).

Methods

This prospective, observational case-control study consisted of 96 eyes of 50 OSAHS patients (mean age of 50.9?±?12.4 years, best-corrected visual acuity ≥20/20, refractive error less than 3 spherocylindrical diopters, and intraocular pressure <21 mmHg) who were enrolled and compared with 64 eyes of 33 age-matched controls. Peripapillary RNFL thickness, ONH parameters, macular thickness and volume were measured by optical coherence tomography (OCT).

Results

OSAHS patients showed a significant reduction of the nasal quadrant RNFL thickness (74.7?±?15.8 μm) compared with those values observed in control patients (81.1?±?16.6 μm, p?=?0.047, Student's t-test). No differences in peripapillary RNFL thickness were observed when dividing the OSAHS group in accordance with disease severity. Vertical integrated rim area (VIRA) (0.67?±?0.41 mm³ in OSAHS vs 0.55?±?0.29 mm³ in controls; p?=?0.043, Student's t-test), horizontal integrated rim width (HIRW) (1.87?±?0.31 mm² in OSAHS vs 1.8?±?0.25 mm² in controls; p?=?0.039, Student's t-test) and disc area (2.74?±?0.62 mm² in OSAHS vs 2.48?±?0.42 mm² in controls; p?=?0.002, Student's t-test) showed significant differences, all of them being higher in the OSAHS group. Severe OSAHS had significant higher disc area (2.8?±?0.7 mm²) than controls (2.5?±?0.4 mm²; p?=?0.016, ANOVA test). Temporal inner macular thickness was significantly higher in mild–moderate OSAHS patients (270?±?12 μm) than in severe OSAHS patients (260?±?19 μm; p?=?0.021, ANOVA test).

Conclusions

OSAHS patients showed decreased peripapillary nasal RNFL thickness, and increased ONH area and volume parameters when they were evaluated by OCT. These findings suggest that neuronal degeneration might be present in the retina of OSAHS patients, as previously observed in some neurodegenerative disorders     

Flicker cone function in normal and day blind sheep: a large animal model for human achromatopsia caused by CNGA3 mutation

Purpose

Recently we reported on day blindness in sheep caused by a mutation in the CNGA3 gene, thus making affected sheep a naturally occurring large animal model for therapeutic intervention in CNGA3 achromatopsia patients. The purpose of this study was to characterize flicker cone function in normal and day blind sheep, with the aim of generating a normative data base for ongoing gene therapy studies.

Methods

Electoretinographic (ERG) cone responses were evoked with full-field conditions in 10 normal, 6 heterozygous carriers and 36 day blind sheep. Following light adaptation (10 min, 30 cd/m²), responses were recorded at four increasing light intensities (1, 2.5, 5 and 10 cd s/m²). At each of these intensities, a single photopic flash response followed by 8 cone flicker responses (10–80 Hz) was recorded. Results were used to generate a normative data base for the three groups. Differences between day blind and normal control animals were tested in two age-matched groups (n = 10 per group).

Results

The normal sheep cone ERG wave is bipartite in nature, with critical flicker fusion frequency (CFF) >80 Hz. In all four flash intensities, the single photopic flash a-wave and b-wave amplitudes were significantly lower (p < 0.005), and implicit times significantly delayed (p < 0.0001), in day blind animals. In all four flash intensities, CFF values were significantly lower (p < 0.0001) in day blind sheep.

Conclusions

Cone function is severely depressed in day blind sheep. Our results will provide a normative data base for ongoing gene therapy studies.     

Full-field electroretinogram findings in children in the atropine treatment for myopia (ATOM2) study

Background

The aims of this study were to determine the longitudinal effects of myopia on full-field electroretinogram (ffERG) in children, and whether there were any effects due to atropine treatment.

Methods

Fifty children, enrolled in the atropine treatment for myopia study, were randomly selected and 35 children consented to undergo ffERG at baseline (prior to atropine treatment), 24 months (at end of treatment) and 32 months (8 months after cessation of treatment). An extended ISCEV ffERG protocol was used for all recordings. The relationship between axial length (AL) and the following scotopic and photopic ffERG responses was analyzed: a- and b-wave amplitude and implicit time, saturated amplitude (V _max), and retinal sensitivity (logK).

Results

Reliable ffERG recordings with acceptable level of noise were obtained on all 3 visits from 29 children (mean age: 9.5 ± 0.8 years and mean spherical equivalent: ?5.0 ± 1.6 D). At baseline, the correlation detected between AL and logK was 0.37 (p = 0.047). There was no significant correlation between AL and V _max or any scotopic and photopic ffERG amplitude and implicit time measures. Longitudinal data suggested a reduction in photopic a- and b-wave and 30 Hz flicker response amplitudes over time. Multivariate analysis showed that the change in 30 Hz flicker response amplitude was likely to be associated with AL change. There was no evidence that changes in other responses were associated with age, baseline AL, or atropine dose used.

Conclusion

Retinal sensitivity was reduced in myopic children. There was a gradual decline in cone function over time which was not influenced by atropine treatment.     

Decreased retinal–choroidal blood flow in retinitis pigmentosa as measured by MRI

Purpose

To evaluate retinal and choroidal blood flow (BF) using high-resolution magnetic resonance imaging (MRI) as well as visual function measured by the electroretinogram (ERG) in patients with retinitis pigmentosa (RP).

Methods

MRI studies were performed in 6 RP patients (29–67 years) and 5 healthy volunteers (29–64 years) on a 3-Tesla scanner with a custom-made surface coil. Quantitative BF was measured using the pseudo-continuous arterial spin-labeling technique at 0.5 × 0.8 × 6.0 mm. Full-field ERGs of all patients were recorded. Amplitudes and implicit times of standard ERGs were analyzed.

Results

Basal BF in the posterior retinal-choroid was 142 ± 16 ml/100ml/min (or 1.14 ± 0.13 μl/mm²/min) in the control group and was 70 ±19 ml/100ml/min (or 0.56 ± 0.15 μl/mm²/min) in the RP group. Retinal–choroidal BF was significantly reduced by 52 ± 8 % in RP patients compared to controls (P<0.05). ERG a- and b-wave amplitudes of RP patients were reduced, and b-wave implicit times were delayed. There were statistically significant correlations between a-wave amplitude and BF value (r=0.9, P<0.05) but not between b-wave amplitude and BF value (r =0.7, P=0.2).

Conclusions

This study demonstrates a novel non-invasive MRI approach to measure quantitative retinal and choroidal BF in RP patients. We found that retinal–choroidal BF was markedly reduced and significantly correlated with reduced amplitudes of the a-wave of the standard combined ERG.     

Clinical results of selective laser trabeculoplasty in silicone oil-induced secondary glaucoma

Background

To analyze the efficacy of selective laser trabeculoplasty (SLT) on silicone oil-induced secondary glaucoma in terms of intraocular pressure (IOP).

Patients and Methods

42 patients (42 eyes) with silicone oil-induced secondary glaucoma were selected, and SLT was performed with 360° of the trabecular meshwork. During the 12-month follow-up, the complications, IOP, and antiglaucoma medication usage were observed.

Results

The mean IOP decreased from 23.1?±?1.9 mmHg before treatment to 18.4?±?3.7 mmHg after treatment (p?<?0.05). Mean number of antiglaucoma medications used for IOP control also decreased from 2.17?±?1.21 to 1.25?±?0.89 (p?<?0.05). The 12-month success rate in the total sample was 59.5 %. The success rate was 60.7 % (17 eyes) and 57.1 % (eight eyes) for phakic and aphakic eyes, respectively (p?>?0.05)

Conclusions

SLT is a safe and effective option for the treatment of patients with silicone oil-induced secondary glaucoma.     

The effect of reactive oxygen species on the myogenic tone of rat ophthalmic arteries with and without endothelium

Background

Reactive oxygen species (ROS) play an important role in the pathogenesis of various ocular diseases. ROS can induce vasodilation or vasoconstriction depending on the species, the tested vessel bed, and the condition of the vessel. This study investigates the effect of different dosages of ROS on the tone of rat ophthalmic arteries.

Methods

Freshly dissected rat ophthalmic arteries were pressurized in a perfusion setup in steps of 10 mmHg to 180 mmHg in three consecutive cycles. The first cycle was run under mostly physiological conditions, the second cycle was run after ROS treatment, and the third cycle as passive dilation after all Ca²⁺ was removed from the solution. ROS-induced dilation or constriction was calculated in relation to the passive dilation. All experiments were performed with or without endothelium.

Results

For vessels with endothelium, dilation in control experiments was 20.0?±?0.1 %; after 5 s of ROS dilation was 74.4?±?0.6 %, and after 20 s 87.4?±?0.3 %. ANOVA revealed significant differences between these groups (P?=?0.048). For vessels without endothelium, a slight dilation was seen in control experiments (14.5?±?0.4 %), which was also present after 5 s of ROS treatment (15.4?±?0.4 %). Treatment with ROS for 20 s led to a constriction of the vessel preparations (?16.6?±?0.5 %; P?=?0.831).

Conclusions

ROS led to a vasodilation in vessels with endothelium that was not seen in vessels without endothelium. Endothelial function seems to determine the effect of ROS on the vessel tone in isolated rat ophthalmic arteries.     

Corneal biomechanical properties measured by the ocular response analyzer in acromegalic patients

Purpose

To investigate the effect of acromegaly on corneal biomechanical parameters.

Methods

This cross-sectional, comparative clinical study included 34 acromegalic patients and 30 age-matched and sex-matched healthy controls. Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated and corneal-compensated intraocular pressure (IOPg and IOPcc, respectively) were measured using the Ocular Response Analyzer. Central corneal thickness (CCT) was determined with the ultrasonic pachymeter.

Results

The mean duration of disease for the acromegalic patients was 5.3 years. There was no significant difference between the groups regarding mean CH, CRF, IOPg and IOPcc values. The respective mean values in patients with acromegaly and controls were 10.3?±?2.2 and 9.5?±?1.5 mmHg (p?=?0.13) for CH; 10.5?±?2.4 and 9.7?±?1.7 mmHg (p?=?0.16) for CRF, 16.1?±?3.6 and 15.5?±?2.9 mmHg (p?=?0.49) for IOPg, 16.8?±?3.4 and 17.0?±?2.8 mmHg (p?=?0.82) for IOPcc, and 544.8?±?32.2 and 530.7?±?22.9 μm (p?=?0.05) for CCT. A significant moderate correlation was detected between the duration of acromegaly and IOPg OD (r?=?0.430, p?=?0.01). There was no significant correlation between other ocular parameters and levels of GH and IGF-1 at the time of diagnosis, the status of control, adenoma type, radiotherapy treatment, and drug usage.

Conclusions

In acromegalic patients, the duration of disease was correlated with IOPg OD level. Corneal biomechanical parameters and CCT values were not significantly different than those in age-matched and sex-matched healthy individuals.     

A comparison between Goldmann applanation tonometry and dynamic contour tonometry after photorefractive keratectomy

Background

The intraocular pressure (IOP) could be measured by both Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT). Although these two methods have been discussed widely after laser-assisted sub-epithelial keratectomy (LASIK), there is little data in the cases undergoing photorefractive keratectomy (PRK). We aimed to compare the changes of IOP measurements obtained by GAT and DCT after PRK for myopia/myopic astigmatism.

Methods

This prospective study enrolled 77 candidates (154 eyes) for PRK to correct myopia or myopic astigmatism and 30 matched patients (30 eyes) with myopia or myopic astigmatism who served as controls. Changes of the IOP measurements (ΔIOP) obtained by GAT and DCT before and at 6 months after PRK in the operated eyes, and at baseline and 6 months later in the controls, were documented. Changes of the central corneal thickness (ΔCCT) were determined in the same fashion.

Results

The mean IOP readings obtained by DCT were comparable before and at 6 months after procedure (18.34 ± 3.03 mmHg and 17.87 ± 2.61 mmHg respectively, p?=?0.41); whereas the mean IOP reading obtained by GAT decreased significantly 6 months postoperatively (17.92 ± 3.63 mmHg and 16.25 ± 2.66 mmHg, p?<?0.001). A significant correlation was present between the ΔIOP obtained by GAT and ΔCCT (r?=?0.61, p?<?0.001). Similar correlation was not significant between the DCT-obtained ΔIOP and the ΔCCT (r?=?0.07, p?=?0.44). The mean ΔIOP obtained by GAT was significantly higher in the operated eyes than in the controls (?1.54?±?1.45 vs 0.07?±?0.44 mmHg, p?=?0.02). The mean DCT-obtained ΔIOP was just marginally insignificant between the operated and nonoperated eyes (?0.63?±?0.59 vs 0.02?±?0.38 mmHg respectively; p?=?0.09).

Conclusions

The authors recommend DCT after PRK in the cases with myopia or myopic astigmatism     

Psychophysically determined full-field stimulus thresholds (FST) in retinitis pigmentosa: relationships with electroretinography and visual field outcomes

Purpose

The purpose of this study is to describe the relationships between full-field stimulus threshold (FST), electroretinography (ERG), and visual field (VF) outcomes in retinitis pigmentosa (RP).

Methods

Data from 47 patients with RP (n = 94 eyes) were evaluated. Patients were submitted to comprehensive ophthalmological examination including measurement of best-corrected visual acuity (BCVA), 30-2 threshold static VF, and microperimetry. Full-field ERG (ISCEV standard) was recorded, and achromatic FST was measured using a Diagnosys Espion system with the ColorDome? LED full-field stimulator (Diagnosys LLC, Lowell, MA, USA).

Results

BCVA mean ± SD was 0.31 ± 0.03 logMAR, and FST mean ± SD was ?18.45 ± 9.53 dB. No significant correlation was found between BCVA and FST. In contrast, statistically significant correlations were found between FST and static 30-2 VF mean deviation (r = ?0.389; P < 0.01), microperimetry mean threshold (r = ?0.607; P < 0.01). Dark and light-adapted ERGs were detectable in 28 and 48 eyes, respectively. Nevertheless, considering only the eyes with recordable ERG responses, moderate correlations were found between combined dark-adapted a-wave amplitude (r = ?0.560; P < 0.01), b-wave amplitude (r = ?0.643; P < 0.001), 30-Hz flicker response (r = ?0.501; P < 0.01), and FST, and high correlation with FST for cone b-wave amplitude (r = ?0.715; P < 0.01).

Conclusions

FST could be successfully determined in RP patients with a wide range of vision loss. FST results showed stronger correlations with full-field ERG amplitude than with sensitivity measured with visual field tests. FST is as an alternative to VF or ERG for assessment of retinal function in patients unable to do visual fields or with non-detectable ERGs.     

Corneal biomechanics predict the outcome of selective laser trabeculoplasty in medically uncontrolled glaucoma

Purpose

To evaluate the predictive value of clinical parameters, including biomechanical properties on the outcome of selective laser trabeculoplasty (SLT) in medically uncontrolled open angle glaucoma (OAG).

Methods

Sixty-eight eyes from 68 patients with OAG and IOP insufficiently regulated by topical medications were enrolled. Patients’ follow-up occurred 6 and 12 months after the procedure. The recorded parameters intraocular pressure (IOP), angle characteristics, central corneal thickness (CCT) and biomechanical properties of the eyes, including corneal hysteresis CH and corneal resistance factor CRF measured with the Ocular Responses Analyzer (ORA, Reichert Ophthalmic Instruments) were tested on their predictive value of SLT-induced IOP lowering effect using correlation analyses and regression models.

Results

Mean IOP reduction 12 months after SLT was 4.2?±?5.7 mmHg (23.2 %, from baseline 18.1?±?5.2 mmHg). The preoperative IOP correlated significantly with IOP reduction (maximum Spearman’s correlation r?=?0.75, p?<?0.001). In linear regression analysis, the corneal biomechanical properties (CH and CRF) together with the baseline IOP revealed good modelling for the IOP lowering effect of SLT (R²?=?0.64, respectively).

Conclusions

In addition to the baseline IOP biomechanical properties (CH and CRF) are significant predictors of SLT induced IOP lowering effect in medically uncontrolled OAG.     

The effect of photodynamic therapy on macular sensitivity in eyes with acute central serous chorioretinopathy

Background

To evaluate the effect of half-fluence rate indocyanine green angiography (ICGA)-guided verteporfin photodynamic therapy (PDT) on macular sensitivity (MS) in eyes with acute symptomatic central serous chorioretinopathy (CSC).

Methods

Single-center consecutive case series by retrospective chart review. Sixteen eyes of 16 patients with acute CSC of 3 months duration or less, treated with half-fluence (25 mJ/cm²) ICGA-guided verteporfin PDT were reviewed. At baseline and after 1, 3, and 6 months, all patients underwent MS testing of the central 20 °, MS testing of the retinal area covered by the PDT laser spot (MSLS), and evaluation of fixation stability (FS) for the central two degrees with the MP-1 microperimeter (Nidek, Vigonza, Italy).

Results

Macular sensitivity improved from 16.4?±?3.0 dB at baseline (n?=?16) to 18.2?±?2.4 dB (p?<?0.001) at 1 month (n?=?16). At the 3-month (n?=?13) and 6-month (n?=?12) follow-up, MS stabilized at 19.5?±?0.9 dB (p?=?0.21) and 19.0?±?1.3 dB (p?=?0.74), without changes when compared to respective precedent follow-up. Mean MSLS improved from 12.9?±?5.4 dB at baseline to 16.4?±?4.9 dB (p?<?0.001) after 1 month. At the 3- and 6-month follow-up, MSLS was 19.1?±?1.2 dB (p?=?0.1) and 18.9?±?1.9 dB (p?=?0.8) respectively. Mean FS at the central 2 ° was 78.8?±?30.4 % before treatment and 81.8?±?29.5 % (p?=?0.7), 81.9?±?27.5 % (p?=?0.7) and 83.6?±?17.1 % (p?=?0.5) respectively 1, 3 and 6 months after treatment.

Conclusion

Half-fluence (25 mJ/cm²) PDT significantly increased mean MS of central 20 ° and mean MSLS, in eyes with acute symptomatic CSC. Fixation stability was stable at baseline and throughout 6 months of follow-up.     

Multifocal electroretinography in type 2 idiopathic macular telangiectasia

Background

To characterize the electroretinographic response of the macula by multifocal electroretinography (mfERG) in patients with type 2 idiopathic macular telangiectasia (MacTel).

Methods

A prospective study of mfERG in patients with type 2 MacTel was conducted from April 2009 to November 2009. mfERGs were recorded using a visual evoked response imaging system (MonElec2, Metrovision, Perenchies, France). The International Society for Clinical Electrophysiology of Vision (ISCEV) guidelines were followed. Patients with type 2 MacTel confirmed by fundus fluorescein angiography without subretinal neovascularisation were included. For recording purposes, 61 stimulus hexagonal elements were used. The first-order kernel mfERG responses were analyzed. Individual mfERG responses for the hexagons were grouped into concentric rings centered on the fovea for analysis (< 2, 5–10, 10–15 and >15°). Student’s t-test and Mann–Whitney U test and linear regression analysis was performed with STATA ver 11.1 (StataCorp, College Station , TX, USA).

Results

Twenty eight eyes of 14 patients and 20 eyes of ten normal controls were included in the study. The mean logMAR visual acuity of the patients was 0.51 (Snellen equivalent 20/63). The mean N1 amplitude (nv/deg²) of patients were significantly reduced compared to controls and were as follows: 8.91?±?14.00 vs 43.44?±?9.55 (p?<?0.0001) in less than 2°, 9.24?±?10.47 vs 22.00?±?3.87 (p?<?0.0001) in 5–10°, 8.57?±?10.02 vs 15.24?±?1.89 (p?<?0.0001) in 10–15°, and 7.03?±?6.52 vs 12.47?±?2.62 in?>?15° (p?<?0.001). The mean P1 amplitude (nv/deg²) was also significantly reduced in patients compared to controls and was as follows: 27.66?±?37.44 vs 96.20?±?12.41 (p?<?0.0001) in less than 2°, 22.61?±?19.38 vs 53.78?±?9.79 (p?<?0.0001) in 5–10°, 18.75?±?20.21 vs 35.22?±?4.16 (p?<?0.001) in 10–15°, and 17.10?±?12.54 vs 25.71?±?3.93 (p?<?0.001). The implicit time of N1 and P1 were also delayed significantly in all the rings. The mean central foveal thickness assessed by optical coherence tomography (OCT) scan was 84.78?±?45.12 μm. There was poor correlation between mfERG amplitudes or implicit times with either the visual acuity or OCT central thickness.

Conclusion

mfERG showed significant reduction in amplitudes and implicit times of the waveforms in patients with type 2 MacTel in all the rings, suggesting a more generalized affection of the macula. The maximum reductions were seen in the <2^o rings. Although there was poor correlation between the visual acuity and the amplitudes a of the waveforms, mfERG is a useful investigative modality for functional assessment of macula in type 2 MacTel patients.