The Effect of Pterygium and Pterygium Surgery on Corneal Biomechanics

[Current possibilities for the diagnosis and treatment of pterygium]

Pterygium is a common inflammatory-proliferative disease characterized by the invasion of degeneratively altered fibrovascular tissue into the cornea. This literature review analyzes the etiological factors and pathogenetic concepts of its development, describes modern methods of diagnostics and surgical treatment of pterygium, and pays particular attention to the assessment of structural and functional changes in the cornea occurring during the growth of pterygium and after its excision.

Impact of pterygium on central corneal thickness measured by optical coherence tomography in older adults

PURPOSE

To measure the central corneal thickness (CCT) using anterior segment optical coherence tomography (AS-OCT) in older adults with and without pterygium from the Brazilian Amazon Region Eye Survey (BARES).

METHODS

BARES is a population-based epidemiological cross-sectional study conducted in Parintins city. Participants were residents ≥45 years of age identified through a door-to-door interview. Eligible participants were invited for a comprehensive eye exam. Pterygium occurrence and severity were assessed by ophthalmologists through slit-lamp examination considering its location (nasal or/and temporal) and severity (lesion with extension <3 mm, ≥3 mm not reaching the pupillary margin or ≥3 mm reaching the pupillary margin). CCTs were obtained and measurements from the more severely affected eye were included. Images were analyzed offline by masked observers.

RESULTS

A total of 671 subjects, 533 (79.4%) with pterygium in at least one eye and 138 (20.6%) without pterygium in either eye, were examined. The mean CCT evaluated by multiple linear regression and adjusted for demographic variables and pterygium severity was 521 ± 34 μm (median = 521; range = 304-665). Decreased CCT was significantly associated with age and pterygium severity. Individuals aged 65-74 years had CCT 7 μm thinner than those aged 45-54 years (p = 0.044), individuals aged 75 years and older had CCT 15 μm thinner than those aged 45-54 years (p = 0.001), and eyes with severe pterygium had CCT 33 μm thinner than eyes without pterygium (p < 0.001).

CONCLUSIONS

The CCT analysis in this population-based sample shows that a thinner cornea is associated with pterygium severity and older age.

Morphometric Measurement of Pterygium with Anterior Segment Optical Coherence Tomography and Relationship with Astigmatism

Purpose: We used anterior segment optical coherence tomography (AS-OCT) to measure the pterygial subepithelial invasion length and thickness before and after surgery, and to evaluate the corneal epithelium and the extent of astigmatism.Methods: This was a retrospective study. Ten eyes that underwent pterygial excision surgery were analyzed. We used corneal topographic data to assess astigmatism before surgery and employed AS-OCT to measure corneal epithelial thickness and the length of subepithelial invasion. We measured the relative pterygial length, width, and area on anterior segment photographs. Corneal topographic assessment and AS-OCT were repeated 1 month after surgery. Multiple regression and Pearson correlation analyses were used to analyze the relationships between normalization of astigmatism and the size and thickness of the excised pterygium.Results: The mean With-the-Rule proportion of preoperative astigmatism was 2.9 ± 2.3 D and the mean corneal epithelial thickness 269.60 ± 84.17 µm. The mean thickness of the excised pterygia was 210.73 ± 80.36 µm. Pterygial thickness was significantly associated with the extent of preoperative With-the-Rule astigmatism and the normalized With-the-Rule astigmatism after pterygial excision. These correlations were stronger than those of the relative pterygial length, width, and area. The mean subepithelial invasion length was 595.00 ± 310.32 µm.Conclusions: An increase in pterygial epithelial thickness influenced the extent of With-the-Rule astigmatism to a much greater extent than did the relative pterygial length, width, and area. AS-OCT measurement of the subepithelial invasion length identifies the required excisional area prior to surgery.

Vitamin D, the Vitamin D Receptor, Calcitriol Analogues and Their Link with Ocular Diseases

The global prevalence of eye diseases continues to grow, bringing with it a reduction in the activity levels and quality of life of patients, and partial or complete blindness if left untreated. As such, there is considerable interest in identifying more effective therapeutic options and preventive agents. One such agent is vitamin D, known to have a range of anti-cancer, anti-angiogenic, anti-inflammatory and anti-oxidative properties, and whose deficiency is linked to the pathogenesis of a range of cardiovascular, cancer, and inflammatory diseases. This review presents the current stage of knowledge concerning the link between vitamin D and its receptor and the occurrence of eye disease, as well as the influence of analogues of calcitriol, an active metabolite of vitamin D. Generally, patients affected by various ocular disorders have vitamin D deficiency. In addition, previous findings suggest that vitamin D modulates the course of eye diseases and may serve as a marker, and that its supplementation could mitigate some disorders. However, as these studies have some limitations, we recommend further randomized trials to clarify the link between vitamin D and its activity with eye disease.

Does systemic inflammation play a role in patients with pterygium?

PURPOSE

To compare parameters of systemic inflammation and serum lipid levels in patients with pterygium versus healthy individuals.

METHODS

Thirty-five patients with pterygium and 30 healthy individuals were enrolled as two respective groups in a retrospective study. The participants' complete blood count (CBC) parameters and levels of serum total cholesterol, low-density lipoprotein, high-density lipoprotein (HDL), and triglycerides (TG) were obtained from digital records and compared. Their neutrophil/lymphocyte, platelet/lymphocyte, and monocyte/HDL ratios were calculated and compared as well. As secondary outcomes, longitudinal length (LL), basal length (BL), and total area (TA) of pterygium among the patients were quantitatively measured by using ImageJ software. Correlations between serum parameters and pterygium measurements were analyzed.

RESULTS

Although between-group differences in CBC parameters and the ratios were not statistically significant, HDL levels were significantly lower (p = 0.014) and TG levels significantly higher (p = 0.031) among patients with pterygium than among the controls. A positive correlation was detected between the patient's age and the pterygium's BL (p = 0.002, r = 0.516), LL (p = 0.00, r = 0.547), and TA (p = 0.00, r = 0.515). Neutrophil levels negatively correlated with LL (p = 0.025, β = - 0.308) and TA (p = 0.002, β = - 0.420).

CONCLUSION

Local instead of systemic inflammation should be considered in the management of pterygium. Besides, decreased HDL levels may indicate systemic oxidative stress in patients with the condition.

Posterior Corneal Surface Changes After Pterygium Excision Surgery

PURPOSE

To evaluate the effect of pterygium excision on the posterior corneal surface and analyze the factors associated with those changes.

METHODS

A prospective, interventional study including 33 eyes of 31 patients who underwent pterygium excision at the Tel Aviv Medical Center (Tel Aviv, Israel). Exclusion criteria included corneal dystrophy, pseudopterygium, corneal scarring, or previous ocular surgery in the treated eye. Data were obtained by using the Galilei dual Scheimpflug analyzer. Recorded posterior corneal data included steep keratometry, flat keratometry, mean keratometry, corneal astigmatism, best-fit sphere, and the squared eccentricity index (e). Posterior surgically induced astigmatism (SIA) was calculated to demonstrate the astigmatic effect of surgery. Anterior-segment high resolution optical coherence tomography was used to measure pterygium dimensions (depth and horizontal/vertical size).

RESULTS

The mean age was 53.7 ± 16.7 years. Posterior corneal SIA was 0.9 ± 1.1 D (P < 0.001) and was significantly correlated with age (r = 0.568, P = 0.002), horizontal pterygium size (r = 0.387, P = 0.046), and preoperative posterior astigmatism (r = 0.688, P < 0.001). In a multivariable analysis, only age (coefficient = 0.010, P = 0.038) and preoperative posterior astigmatism (coefficient = 0.648, P = 0.002) remained significant. Pterygium dimensions were not significantly associated with SIA magnitude. Flat keratometry steepened by 0.5 ± 1.1 D (P = 0.019), mean keratometry steepened by 0.3 ±0.6 D (P = 0.035), posterior astigmatism was reduced by 0.4 ± 1.2 D (P = 0.072), and e decreased by 5.1 ± 17.3 (P = 0.021).

CONCLUSIONS

Pterygium excision has a significant astigmatic effect on the posterior corneal surface. The astigmatic effect increases with age and with higher preoperative posterior astigmatism. Pterygium depth and size are not associated with the degree of surgical astigmatic effect.

Pterygium in adults from the Brazilian Amazon Region: prevalence, visual status and refractive errors

AIMS

To determine prevalence of pterygium, its role as main cause of unilateral and bilateral visual impairment and blindness and its impact on refractive errors from adults living in a high ultraviolet exposure area in the Brazilian Amazon Region.

METHODS

Cluster sampling was used in randomly selecting subjects ≥45 years of age from urban and rural areas of Parintins city. Eligible subjects were enumerated through a door-to-door household survey and invited for an eye exam including refraction. Pterygium was assessed considering location (nasal, temporal or both) and size (<3 mm or ≥3 mm reaching or not pupillary margin).

RESULTS

A total of 2384 persons were enumerated and 2041 (85.6%) were examined. Prevalence of pterygium was 58.8% (95% CI 53.8% to 63.7%) and associated with male gender (OR=1.63; 95% CI 1.37 to 1.94; p=0.001), while higher education was a protective factor (OR=0.63; 95% CI 0.44 to 0.92; p=0.018). Older age and rural residence were associated with pterygium ≥3 mm reaching or not pupillary margin, while higher education was a protective factor for pterygium ≥3 mm reaching pupillary margin. Prevalence of pterygium as cause of visual impairment and blindness was 14.3% and 3.9%, respectively. Significantly higher hyperopic refractive errors were found in eyes with pterygium ≥3 mm reaching or not pupillary margin.

CONCLUSIONS

Pterygium was highly prevalent and the second cause of visual impairment and blindness after provision of refractive correction. Risk factors for pterygium were male gender, advanced age, lower education and rural residency. Strategies to provide pterygium early detection and proper management should be considered by healthcare authorities in this population.

The Effect of Strabismus Muscle Surgery on Corneal Biomechanics

Purpose

Studying the early effect of different extraocular muscle (EOM) surgeries on corneal biomechanics.

Subjects and methods

This is a prospective, nonrandomized, interventional study, in which 42 eyes of 29 candidates for EOM surgery for strabismus correction at Cairo university hospitals, aged 14–37 years, were recruited. All participants had measuring of the visual acuity, refraction (spherical equivalent (SE)), assessment of the EOM motility and muscle balance, sensory evaluation, fundus examination, and assessing the ocular biomechanics using the Ocular response analyzer (ORA, Reichert, INC., Depew, NY) noting the corneal hysteresis (CH) and corneal resistance factor (CRF) preoperatively. Same patients were reassessed using ORA 4 weeks postoperatively following a different standard EOM surgery (recti weakening/strengthening and inferior oblique weakening either (graded recession) according to the surgical indication, and ∆CH and ∆CRF were calculated, each is the preoperative − the postoperative value.

Results

∆CH and ∆CRF = −0.78 ± 1.56 and −0.72 ± 2.15, respectively, and a highly significant difference was found between each of the pre- and postoperative CH and CRF (p < 0.001). 18 eyes had single EOM surgery, while 24 had multiple (2 or 3) EOM surgery; ∆CH in the single group = −1.28 ± 1.5, and ∆CH in the multiple group = 0.4 ± 1.49 (p=0.07). 23 eyes had EOM weakening surgery, while 18 had combined weakening and strengthening EOM surgery: ∆CH in the weakening group = −1.24 ± 1.77 and ∆CH in combined group = −0.26 ± 1.07 (p=0.04). A nonsignificant difference was found for ∆CRF (p=0.53).

Conclusion

A different EOM surgery has an early tendency for increase of the postoperative CH specially for muscle weakening procedures (recti recession/inferior oblique muscle weakening).

Risk factors for early onset elevated intraocular pressure after pterygium surgery

Purpose

In this study, we aimed to identify the risk factors for early postoperative elevation of intraocular pressure (IOP) after pterygium surgery.

Patients and methods

All patients in this retrospective cohort study were evaluated for inclusion from a single tertiary care center at Boston Medical Center. Their pre- and postoperative IOP measurements (day 1, week 1, month 1, month 3, and when clinically necessary) were compared. Patients with postoperative IOP measurement of >22 mmHg or with an increase in IOP by ≥10 mmHg compared with the preoperative measurement value were grouped as “Ocular Hypertension” group; otherwise, patients were grouped in the “No Ocular Hypertension” group. Age, sex, race, baseline IOP, cup-to-disc (C/D) ratio, history of glaucoma, and frequency of use of postoperative steroid drops in all patients were compared. Chi square test was performed to compare the categorical variables, whereas Student’s t-test was performed to compare continuous variables. We performed a multivariate logistic regression analysis of categorical data with a significance level of p < 0.05.

Results

In total, 240 patient charts were reviewed for inclusion in this study. Twenty-six patients required pterygium surgery on both eyes; for these patients, the eye with higher IOP was analyzed. Two patients were discontinued from this study because of elevated IOP in the contralateral, nonsurgical eye. Fortyeight out of 212 eyes (22.64%) developed postsurgical elevation of IOP within the first 3 months of operation. No significant differences were found between age, sex, baseline IOP, C/D ratio, history of glaucoma diagnoses, and frequency of use of postoperative steroid drops. However, Hispanic/Latino race (p = 0.036) and lack of application of steroid ointment (p = 0.001) were found to be the significant risk factors for the development of “Ocular Hypertension” in multivariate analysis.

Conclusion

Early elevation of IOP is a risk of pterygium surgery. One nonmodifiable risk factor, Hispanic/Latino race, and one modifiable risk factor, lack of application of steroid ointments, were identified as potential causes of early postoperative IOP elevation.