Nanosuspensions in ophthalmology: Overcoming challenges and enhancing drug delivery for eye diseases

This review article provides a comprehensive overview of the advancements in using nanosuspensions for controlled drug delivery in ophthalmology. It highlights the significance of ophthalmic drug delivery due to the prevalence of eye diseases and delves into various aspects of this field. The article explores molecular mechanisms, drugs used, and physiological factors affecting drug absorption. It also addresses challenges in treating both anterior and posterior eye segments and investigates the role of mucus in obstructing micro- and nanosuspensions. Nanosuspensions are presented as a promising approach to enhance drug solubility and absorption, covering formulation, stability, properties, and functionalization. The review discusses the pros and cons of using nanosuspensions for ocular drug delivery and covers their structure, preparation, characterization, and applications. Several graphical representations illustrate their role in treating various eye conditions. Specific drug categories like anti-inflammatory drugs, antihistamines, glucocorticoids, and more are discussed in detail, with relevant studies. The article also addresses current challenges and future directions, emphasizing the need for improved nanosuspension stability and exploring potential technologies. Nanosuspensions have shown substantial potential in advancing ophthalmic drug delivery by enhancing solubility and absorption. This article is a valuable resource for researchers, clinicians, and pharmaceutical professionals in this field, offering insights into recent developments, challenges, and future prospects in nanosuspension use for ocular drug delivery.

Comparison of anterior segment parameters of the eye between type 2 diabetic with and without diabetic retinopathy and non-diabetic

AIM: To compare anterior segment parameters between two groups of type 2 diabetic with and without diabetic retinopathy (DR) and non-diabetic elderly subjects based on hemoglobin A1c (HbA1c) levels and status of DR. METHODS: This study was conducted on 997 residents aged 60y or over in Tehran, Iran. Diabetic group had HbA1c level ≥6.4% with no other systemic problems. The non-diabetic participants had normal eye findings and no systemic diseases. K1, K2, mean K, Q-value, anterior, central, posterior, and total corneal densitometric findings, anterior chamber volume (ACV), anterior chamber depth (ACD), corneal volume (CV), and pachymetry were measured by Pentacam AXL. RESULTS: A total of 678 non-diabetic (39% male) and 319 diabetic (35% male) subjects with mean age of 66.31±5.23 and 67.22±4.96y were examined, respectively. No statistically significant difference was found in anterior segment parameters between non-diabetic and diabetic groups (all P>0.05). However, middle, posterior, and total corneal densitometric values were statistically different between two groups after controlling the effects of confounders (P=0.014, 0.007, and 0.042, respectively). Corneal densitometric values in all layers, ACD, and ACV were different between diabetic subjects with and without DR (all P<0.05). In the diabetic group, only corneal densitometric values had a negative relationship with fasting blood sugar (P<0.001). ACD and ACV had a negative correlation with HbA1c levels (all P<0.05, r=-0.129 and -0.146, respectively). However, the relationships were not observed after controlling the confounders (P=0.938, 0.466, respectively). CONCLUSION: Considering the higher densitometric values of the cornea and lower ACD and ACV in diabetic subjects with DR, it is suggested that the examiners should perform comprehensive retinal examinations when faced with such conditions.

Changes in Refractive and Optometric Findings During Pregnancy

Background: Pregnancy-induced changes in the physiological responses during the gestational period can affect the eye. This study aimed to evaluate the effect of pregnancy on visual, refractive, vergence, and accommodative status. Methods: In this cross-sectional study, twenty-five healthy pregnant women with a mean age of 29±3.1 were examined. All of the subjects underwent comprehensive ophthalmologic examinations, including anterior segment and fundus examinations and tonometry. Refractive error was determined in each trimester using Autokeratometer. Furthermore, near the point of convergence (NPC), best-corrected visual acuity (BCVA), and near the point of accommodation (NPA) were measured. Data analysis was performed using SPSS version 22. To compare the data during pregnancy, repeated measures analysis of variance (ANOVA) was performed. Results: During pregnancy, in the right and left eye, spherical equivalent (SE) had a myopic shift from -0.13 to -0.35 D and +0.096 to -0.23 D, respectively (p=0.049 and p=0.020, respectively). Also, in the right and left eyes BCVA significantly decreased from -0.13 to 0.00 and -0.14 to 0.00 LogMAR, respectively (p=0.039 and p=0.045, respectively). NPA and NPC did not change statistically significantly during pregnancy (p=0.385, and p=0.801, respectively). Conclusion: Due to the unstable hormonal status, a myopic shift and decrease in BCVA occur during pregnancy. So, any change in their spectacle prescription, fitting of contact lenses, performing refractive surgeries, etc., during this period should be postponed.

Vector analysis of moderate to high myopic astigmatism after small-incision lenticule extraction (SMILE): 12-month follow-up

PURPOSE

To evaluate the refractive outcomes of small-incision lenticule extraction (SMILE) surgery in moderate to high myopic astigmatism.

STUDY DESIGN

Prospective interventional case series.

METHODS

This study evaluated 111 eyes of 68 patients treated with femtosecond SMILE surgery for the correction of myopia and astigmatism. Inclusion criteria were myopia of - 0.5 D or more and astigmatism between - 1.0 D and -5.0 D. Refractive and visual measurements were obtained preoperatively, 1 and 12 month(s) postoperatively. Vector analysis was used to study the astigmatic outcomes at 12-month follow-up. Comparison of results in two groups of patients with astigmatism below and over 3.00 D was performed.

RESULTS

The preoperative mean spherical equivalent was -5.48 ± 2.17 D (range - 1.75 to - 10.00 D) and the mean cylinder was -2.02 ± 1.09 D (range - 1.00 to - 5.00 D). The mean postoperative cylinder value was -0.60 ± 0.52 D at 12-month visit. The 12-month safety and efficacy indices were 0.98 ± 0.07 and 0.97 ± 0.12, respectively. The high astigmatism group showed significantly lower safety and efficacy indices. The postoperative residual astigmatism was 0.5 D or less in 73% of the eyes. Higher amount of residual astigmatism was observed in the high astigmatism group. The angle of error was ± 5 degrees in 49% and ± 15 degrees in 87% of the eyes.

CONCLUSION

SMILE surgery is effective and safe method for correcting myopic astigmatism. Vector analysis indicated a tendency for the under correction of astigmatism in subjects with high astigmatism.

Is there any connection between choroidal thickness and obesity?

Obesity is a health-threatening and epidemic medical condition that can affect individuals of different ages and is potentially associated with an increased risk of systemic and ocular disorders. Despite the well-documented adverse effects of obesity on different parts of the body vasculature, less published data are available concerning obesity-related consequences on the ocular vasculature. As the human choroid is a highly vascularized tissue, its morphology and function might be altered in obese individuals. The micro-structural changes within the choroid could also trigger development of subsequent functional abnormalities of the eye. Previous population-based studies have asserted an association between obesity and choroidal thickness; however, they reported conflicting patterns of association between obesity and changes in choroidal thickness. Therefore, to enhance our understanding of the changes in choroidal morphology secondary to obesity, we reviewed studies describing the micro-structural consequences of obesity on the choroidal thickness profile and its underlying physiological and anatomical basis. This review includes all original publications related to the association between choroidal thickness and obesity published until mid-2021 that were indexed in PubMed, Google Scholar, ScienceDirect, or Scopus.

Refractive characteristics of keratoconus eyes with corneal Vogt's striae: A contralateral eye study

PURPOSE

The aim of this study was to assess and compare clinical characteristics of bilateral keratoconus patients with unilateral Vogt's striae.

METHODS

In this contralateral eye study, refractive status were evaluated in patients with bilateral keratoconus whose corneas had definite slit-lamp biomicroscopic evidence of unilateral Vogt's striae. All cases underwent a comprehensive ophthalmic examination. Some refractive errors components provided by autorefraction were converted to vectorial notation for power vector analysis. Finally, the outcomes were compared between keratoconus eyes with and without Vogt's striae.

RESULTS

Fifty patients aged 20 to 38 years (27.43±5.5) were recruited in this study. The results showed a significant difference in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), non-cycloplegic and cycloplegic autorefraction including sphere, cylinder, spherical equivalent, and J₀, between keratoconus eyes with and without Vogt's striae (all P<0.05), except for J₄₅ (P=0.518 in non-cycloplegic autorefraction and P=0.574 in cycloplegic autorefraction). Comparison of cycloplegic and non-cycloplegic autorefraction in both study groups showed significant differences in the sphere and spherical equivalent (all P<0.001), but no significant difference was found in cylinder, J₀, and J₄₅ between the study groups (all P>0.05).

CONCLUSIONS

Comparison of the cycloplegic and non-cycloplegic autorefraction in keratoconus eyes with and without Vogt's striae showed significant differences in UDVA, CDVA, and some refractive errors components provided by autorefraction between the two groups, with a worse condition in KCN eyes with Vogt's striae.

Evaluation of the presence of a central fusion lock effect on fixation disparity curve parameters in symptomatic and asymptomatic subjects

Clinical relevance: Several parameters are likely to affect the magnitude of fixation disparity (FD) and FD curve characteristics. Presence of a central fusion lock may have an important effect on clinical testing of FD and interpretation of its results.Background: The aim of this study was to evaluate FD curve parameters using the modified near Mallett unit (with a central fusion lock) and the Sheedy disparometer (without a central fusion lock) in symptomatic and asymptomatic subjects.Methods: This cross-sectional study was conducted in 147 patients with a mean age of 22.5 years who presented to the optometry clinic of Paramedical College of Mashhad University of Medical Sciences. The symptoms were recorded in a questionnaire for each patient. FD was measured using the modified near Mallett unit and Sheedy disparometer and FD curves were generated using the AutoCAD 2005 software.Results: There was a significant difference in the FD, associated phoria, and slope measurements between the two devices (all p values < 0.05). Significant difference was found in the mean FD between symptomatic and asymptomatic subjects using the modified near Mallett unit (p < 0.0001) and Sheey disparometer (p = 0.007). In symptomatic subjects, the mean slope was steeper for the modified near Mallett unit compared to the Sheedy disparometer (p = 0.001). Although the mean centre of symmetry was more negative in the modified near Mallett unit versus the Sheedy disparometer, the difference between the instruments was not significant in symptomatic (p = 0.477) and asymptomatic (p = 0.257) participants.Conclusion: There are differences in the FD curve parameters between the modified near Mallett unit and Sheedy disparometer. Slope is a proper criterion for differentiating asymptomatic subjects from symptomatic individuals. The modified near Mallett unit is a more precise tool for assessment of non-compensated heterophoria compared to the Sheedy disparometer.

Choroidal Thickness Profile in Normal Iranian Eyes with Different Refractive Status by Spectral-Domain Optical Coherence Tomography

Purpose

To investigate the choroidal thickness and its association with age, gender, spherical equivalent (SE), and axial length (AL) in a sample of Iranian population with different refractive status using spectral-domain optical coherence tomography (SD-OCT).

Methods

In a cross-sectional study, a total of 469 right eyes of 469 healthy subjects comprising 194 (41.4%) males and 275 (58.6%) females were examined. The mean age was 32.76 ± 15.77 years (range, 4-60 years). All subjects were divided into different groups according to their refractive status, age, and AL. The choroidal thickness was evaluated through enhanced-depth imaging (EDI) modality at subfoveal (Sf), 1, and 3 mm nasal (N1 and N3, respectively), temporal (T1 and T3, respectively), superior (S1 and S3, respectively), and inferior (I1 and I3, respectively) to the foveal center.

Results

In the whole population, the mean subfoveal choroidal thickness (SfChT) was 329.83 ± 70.33 μm, and the choroid was thickest at S1 (342.04 ± 71.28 μm) and thinnest at N3 (209.00 ± 66.0 μm). Our data indicated a significant difference in the mean choroidal thickness across all points in different age groups (P < 0.0001). For emmetropic, myopic, and hyperopic subjects, mean SfChT values were 346.64 ± 59.63, 319.66 ± 73.17, and 364.00 ± 74.54 μm, respectively. Linear regression estimated that SfChT decreased about 12.8 and 8.71 μm for every 10 years of aging and each diopter increasing in myopia, respectively. Additionally, the SfChT decreased as 13.48 μm per mm increase in AL.

Conclusions

The mean SfChT of a sample of Iranian emmetropic subjects was 346.64 ± 59.63 μm. The choroidal thickness has a decreasing trend with increasing age, and the choroid is thinner in myopes and thicker in hyperopes compared with emmetropic subjects. In the whole participants, the thickest and thinnest points were S1 and N3, respectively.

Comparative evaluation of tomographic and biometric characteristics in bilateral keratoconus patients with unilateral corneal Vogt's striae: a contralateral eye study

PURPOSE

The aim of this study was to evaluate and compare tomographic and biometric characteristics measured by the corneal tomography and ocular biometry in bilateral keratoconus (KCN) patients with and without corneal Vogt's striae.

METHODS

Ninety-two eyes of 46 subjects with a reliable diagnosis of bilateral KCN with unilateral Vogt's striae were enrolled in this cross-sectional contralateral eye study. In addition to refraction (calculated by vectorial analysis) and visual acuity, corneal tomographic measurements were obtained by the Pentacam (Scheimpflug-based anterior segment tomography). Also, ocular biometric characteristics were evaluated using the Ocuscan® RxP (ultrasound biometer). The KCN eyes were categorized into two groups, including eyes with Vogt's striae and eyes without Vogt's striae.

RESULTS

Our results showed significant differences in the sphere, cylinder, spherical equivalent, J0, corrected and uncorrected distance visual acuity, flat, steep and maximum keratometry, anterior chamber depth (ACD), and central corneal thickness (CCT) between the two groups (all P<0.001). The eyes without Vogt's striae had a shorter ACD measured by the Pentacam and biometer. There were no differences in axial length (AL) and vitreous length (VL) between the two groups (all P>0.05). Also, there was poor agreement between the measurements of the Pentacam and ultrasound biometer for ACD in the study groups.

CONCLUSION

Corneal tomographic and ocular biometric measurements showed significant differences between KCN eyes with and without Vogt's striae except for AL and VL. These differences should be noticed in clinical evaluations and treatment of KCN patients.

Comparison between Pentacam HR and Orbscan II after Hyperopic Photorefractive Keratectomy

Purpose:

The aim of this study was to determine the agreement between Pentacam HR (Scheimpflug imaging, Oculus) and Orbscan II (scanning slit topography, Bausch and Lomb) in measuring corneal parameters after photorefractive keratectomy (PRK) for hyperopia.

Methods:

In this prospective cross-sectional study, 38 hyperopic eyes undergoing PRK were examined before refractive surgery and 8 to 10 months postoperatively using Pentacam HR and Orbscan II. Ultrasound (US) pachymetry was also used to measure central corneal thickness (CCT). The radius of anterior (A-) and posterior (P-) best-fit sphere size (BFS), central elevation (CE), and anterior maximum tangential power in 3 mm (TG3) and 3-5 mm (TG5) zones, anterior chamber depth (ACD), and central corneal thickness (CCT) were collected and used in the analyses. To study the agreement between the measurements made by the two devices, the method described by Bland and Altman was used and the 95% limits of agreement were calculated.

Results:

The 95% limits of agreement show reasonable agreement between the measurements by Pentacam HR and Orbscan II for A-BFS, P-BFS, A-TG3, and CCT, but not for A-CE, P-CE, A-TG5, or ACD. CCT values obtained by both Pentacam HR and Orbscan II correlated well with the values determined by US pachymetry.

Conclusion:

Pentacam HR and Orbscan II after PRK for hyperopia show reasonable agreement for determining A-BFS, P-BFS, A-TG3, and CCT, but not for A-CE, P-CE, A-TG5, or ACD. CCT measurements with Pentacam HR have reasonable agreement with US pachymetry.

Investigation of the effects of Islamic fasting on ocular parameters

Purpose

To investigate the effects of religious fasting during the month of Ramadan on intraocular pressure (IOP), refractive error, corneal tomography and biomechanics, ocular biometry, and tear film layer properties.

Methods

This prospective study was carried out one week before and in the last week of Ramadan. Ninety-four eyes of 94 healthy adult volunteers (54 males and 40 females) with a mean ± SD age of 35.12 ± 9.07 were enrolled in this study. Patients with any systemic disorder, ocular disease, or a history of previous surgery were excluded. Corneal tomography and biomechanics, ocular biometry, IOP, refractive error, and tear break up time (TBUT) were evaluated in non-fasting and fasting periods by the Pentacam (Oculus), Corvis ST (Oculus), IOL Master (Carl Zeiss), computerized tonometer (Topcon CT-1/CT-1P), auto kerato-refractometer (Topcon KR-1), and Keratograph 5M (Oculus), respectively.

Results

There was no significant difference in the central corneal thickness (CCT) between the study groups (P = 0.123) using the Pentacam while the Corvis ST showed a significant difference in all participants (P < 0.0001). Moreover, the peak distance (distance of the two surrounding peaks of the cornea at the highest concavity) of male and female participants showed a significant difference between the fasting and non-fasting groups (P = 0.002). The anterior chamber depth (ACD) using the Pentacam decreased in the male group (P = 0.004) in the fasting period. During the fasting period, computerized tonometer showed a decrease in IOP only in males in comparison to the non-fasting group (P = 0.018) while the Corvis ST showed decreased IOP in all participants (P < 0.0001). The steep keratometry (K2) in the corneal posterior surface appeared to be different in males between the study groups (P = 0.034). We were unable to show any significant difference in other ocular parameters between fasting and non-fasting periods.

Conclusion

This study showed that ACD, IOP, CCT, and peak distance were different between fasting and non-fasting groups while no difference was observed in other ocular parameters. Interpretations of these significant differences should be considered in the clinical setting.

Corneal hysteresis and corneal resistance factor in pellucid marginal degeneration

Purpose

To evaluate and compare corneal hysteresis (CH) and corneal resistance factor (CRF) in pellucid marginal degeneration (PMD), keratoconus (KCN), and normal eyes using the Ocular Response Analyzer (ORA).

Methods

In this retrospective study, corneal biomechanical parameters were measured in patients with PMD (n = 102) and KCN (n = 202) and normal subjects (n = 208) using the ORA. Data, including full patient history as well as the results of refraction, slit-lamp biomicroscopy, Pentacam HR (Oculus), and ORA (Reichert; Buffalo, New York, USA), were collected from medical records. Also, the data of only one eye per individual were selected for the analysis. The inclusion criteria for PMD and KCN groups were a reliable diagnosis of these ectatic disorders based on the clinical and corneal tomographic findings. CH, CRF, CH–CRF, intraocular pressure (IOP) measurements were assessed for each subject. Data were analyzed with SPSS and MedCalc using the ANOVA, Pearson Correlation, and receiver operating characteristic (ROC) curve analysis.

Results

The mean CH was 8.91 mmHg ± 1.05 [standard deviation (SD)], 8.43 ± 0.78, and 10.89 ± 1.08 in the PMD, KCN, and normal group, respectively. Also, the mean CRF was 8.21 ± 1.35, 7.19 ± 1.11, and 10.69 ± 1.41 in the PMD, KCN, and normal group, respectively. ANOVA showed differences in the mean CH, CRF, and CH–CRF between three groups (P < 0.001). Also, ROC curve analysis showed the cut-off points ≤9.5, ≤9.5, and >1.3 mmHg for CH, CRF, and CH–CRF in the PMD group, respectively. For biomechanical parameters in PMD eyes, CRF had the highest sensitivity (75.49%) while the greatest area under the ROC curve (AUC) was seen for CH (0.903). Moreover, central corneal thickness (CCT) showed no correlation with CH (P = 0.30, r = −0.104) or CRF (P = 0.75, r = 0.033) in the PMD group.

Conclusions

This study presented the values of corneal biomechanics for PMD using the ORA. The results of the ORA were markedly different between PMD, KCN, and normal eyes.