Effects of fibrovascular traction and pooling of tears on corneal topographic changes induced by pterygium

Importance of Higher-Order Aberrations on Both Anterior and Posterior Surfaces After Pterygium Surgery

PURPOSE

The purpose of this study was to investigate the changes in higher-order aberrations (HOAs), coma, and spherical aberrations (SAs) on the anterior, posterior, and total corneal surfaces after pterygium excision.

METHODS

In this single-center study, we examined 19 eyes of 15 patients who underwent pterygium excision at Yokohama Minami Kyosai Hospital between January 2017 and December 2017. We also evaluated 25 eyes of 25 age-matched patients with no history of ocular disease as the control group. Corneal topography, total HOAs, coma, and SAs in all regions at 4 and 6 mm diameters were evaluated using anterior segment optical coherence tomography (CASIA SS-1000, Tomey, Japan). The pterygium area and extent were also assessed.

RESULTS

Significant improvements in the HOAs, coma, and SAs at both diameters were observed in the total and anterior corneas from the first postoperative month. Notably, the posterior cornea showed significant improvements in HOAs (4 mm: P < 0.001 [log HOAs]; 6 mm: P = 0.001 [log HOAs]) and coma (4 mm: P = 0.003 [log coma], 6 mm: P = 0.002 [log coma]) within both diameters at 1 month postoperatively. A strong correlation was identified among the pterygium area, posterior HOAs, and coma (Spearman correlation = 0.651). Pterygium induced 2 D of astigmatism when extension exceeded 2.1 mm.

CONCLUSIONS

HOAs in both the anterior and posterior corneas improved after pterygium excision. This finding underscores the importance of considering corneal aberrations on both anterior and posterior surfaces in pterygium management.

Effect of pterygium on corneal astigmatism, irregularity and higher-order aberrations: a comparative study with normal fellow eyes

Pterygium is an abnormal growth of fibrous conjunctival tissue that invades the cornea, resulting in corneal distortion, astigmatism, and increased higher-order aberrations (HOAs). However, few studies have compared eyes with pterygium to normal fellow eyes when interpreting HOAs and there is no study that revealed the effect of the thickness or grading of the pterygium on the change of HOAs. Therefore, we evaluated the effects of nasal pterygium by comparing the normal fellow eye of 59 patients. The pterygium significantly increased with-the-rule corneal astigmatism and corneal irregularity. Trefoils, horizontal coma, and quatrefoils were significantly induced by the pterygium. The grading of the pterygium was not correlated with its characteristics except for the thickness. In multiple linear regression analysis, pterygium-induced corneal astigmatic/irregularity values and horizontal trefoil/quatrefoil were associated with the area of the pterygium. The length of the pterygium was an independent inducer of oblique trefoil/quatrefoil, while horizontal coma was independently associated with both its length and width. The thickness was not correlated with any optical parameters. Together, the results demonstrate that nasal pterygium significantly induces corneal astigmatism, irregularity and some HOAs. These pterygium-associated changes in optical parameters could be predicted by the length, width and area of the pterygium.

The effect of pterygium surgery on intraocular lens power and ocular biometric parameters

AIMS

To evaluate the effect of pterygium surgery on intraocular lens (IOL) power and ocular biometric parameters and to evaluate the factors affecting these parameters.

METHODS

Twenty-eight eyes of 25 patients diagnosed with pterygium were evaluated. Axial length (AL), mean keratometry (Sim K), K1, K2, anterior chamber depth (ACD), corneal astigmatism, and ocular biometry parameters were obtained with a dual Scheimpflug analyzer. Pterygium sizes (horizontal, vertical) were measured manually, and pterygium height was analyzed with anterior segment optic coherence tomography. IOL power was calculated according to SRK/T, SRK II, Hoffer Q, Haigis, and Holladay formulas. Limbal conjunctival autograft was performed in all patients after excisional pterygium surgery. Preoperative and postoperative 1st month measurements were analyzed and compared.

RESULTS

The mean age of the patients was 51.5 ± 13.8 years. Mean horizontal pterygium length, vertical width, height, and percentage extension of the pterygium were 2.4 ± 0.9, 4.7 ± 1.0 mm, 297 ± 93µm, and 20.2 ± 7.2%, respectively. There was a significant increase in Sim K, K1, and K2 values postoperatively. Postoperative IOL power was significantly lower than preoperative values in all formulas. The change in IOL power after surgery was -0.3 ± 0.6D in the SRKT, -0.3 ± 0.5D in SRK II, -0.4 ± 0.7D in Hoffer Q, -0.5±0.7D in Haigis, and -0.3 ± 0.7D in Holladay 2 formulas. The change in IOL power has a moderate positive linear correlation with the horizontal and vertical sizes of the pterygium and a high positive linear correlation with the percentage extension of the pterygium.

CONCLUSIONS

Pterygium surgery causes a significant decrease in calculated IOL power obtained with all formulas. It becomes more pronounced with the increase in the size of the pterygium.

Does pterygium morphology affect corneal astigmatism?

PURPOSE

The purpose of this study was to evaluate the correlation between corneal astigmatism and the morphology of pterygium with anterior segment optic coherence tomography (AS-OCT).

MATERIAL AND METHODS

The size of pterygium (horizontal length, vertical width) was measured manually; pterygium area and percentage extension of the pterygium onto the cornea were calculated. Anterior and posterior corneal astigmatism, Sim K, K1, K2 were measured using a dual Scheimpflug analyzer. Morphological patterns of the pterygium analyzed with AS-OCT were determined according to the extension of the pterygium apex below the corneal epithelium. Two tomographic patterns were identified: continuous and nodular. Correlation between anterior corneal astigmatism and pterygium size, percentage extension of the pterygium, and morphological pattern of the pterygium was analyzed.

RESULTS

The mean ages of the 47 patients were 49.4 ± 16.6 (22-80) years. Mean horizontal pterygium length, vertical width, pterygium area, and percentage extension of the pterygium were 2.8 ± 1.2 mm, 4.8 ± 1.6 mm, 7.42 ± 5.6 mm2 and 24.5 ± 10.4%, respectively. Mean anterior corneal astigmatism was 2.3 ± 2.3 D and simulated keratometry was 43.4 ± 2.02 D. In terms of the morphological pattern of the pterygium, 24 eyes had continuous, 23 eyes had a nodular pattern and the median (interquartile range) anterior corneal astigmatism was 1.87 (1.01-3.80) and 1.22 D (0.58-2.35), respectively (p = 0.102). Other topographic and pterygium size parameters were similar between groups. Analyzing the correlations in groups separately, a positive moderate statistically significant correlation was present between vertical width, percentage extension, pterygium area, and anterior corneal astigmatism in both continuous and nodular groups.

CONCLUSIONS

Although not statistically significant, anterior corneal astigmatism was higher in continuous group. Using AS-OCT to standardize the morphology of pterygium could provide additional clinical information.

Myopic regression and recurrent Salzmann nodule degeneration after laser in situ keratomileusis in Ehlers Danlos Syndrome

PURPOSE

We describe the first case of Ehlers Danlos Syndrome (EDS) reported in the English language ophthalmic literature to have undergone Laser In Situ Keratomileusis (LASIK) surgery.

OBSERVATIONS

We review our patient's specific postoperative complications of myopic regression, Salzmann nodular degeneration, and dry eye syndrome, as well as the risks and consequences of performing LASIK on patients with this collagen disorder.

CONCLUSIONS AND IMPORTANCE

Refractive errors may prompt EDS patients to seek laser vision correction, placing them at increased risk for complications such as myopic regression, keratectasia, and dry eye syndrome. Aberrant wound healing and collagen dysfunction may have influenced our patient's myopic regression and Salzmann nodule degeneration post-LASIK. Currently, EDS is considered a relative contraindication in LASIK due to a presumed higher risk of postoperative keratectasia; however, we believe it is possible that not all forms of EDS need to be an absolute contraindication to LASIK. More research is warranted to determine preoperative risk stratification for laser vision surgery in each subtype of EDS.

Corneal tomography and biomechanics in primary pterygium

PURPOSE

To study the Scheimpflug's imaging and corneal biomechanics in primary pterygium.

METHODS

A prospective observational study of 55 patients with unilateral primary nasal pterygium was done. The normal fellow eyes of patients with pterygium were taken as controls. Clinical parameters noted included visual acuity, values of corneal curvature by doing Scheimpflug imaging, wavefront aberrations in terms of higher and lower-order aberrations and corneal hysteresis (CH) as well as corneal resistance factor (CRF) values by using ocular response analyzer.

RESULTS

Of the total 55 patients, mean age was 43.0 + 11.4 years (range: 20-72 years). Mean LogMar uncorrected visual acuity in pterygium eyes and control eyes was 0.21 + 0.20 and 0.12 + 0.15, respectively (p = 0.016). On Scheimpflug imaging the mean anterior corneal curvature values (Ka1/Ka2 D) were 41.09 + 3.38/44.33 + 2.29 in pterygium eyes, 43.13 + 1.79/43.98 + 2.17 in control eyes (p < 0.0005) and mean posterior corneal curvature (Kp1/Kp2 D) values were 6.14 + 0.39/6.53 + 0.43 in pterygium eyes and 6.13 + 0.28/6.46 + 0.47 in control eyes (p > 0.05). Analysis of corneal aberrations showed significantly higher corneal wavefront aberrations in pterygium eyes. Highest correlation of corneal astigmatism was noted with corneal area encroached by pterygium (ρ = 0.540 for LOA and 0.553 for HOA) and distance from pupillary center (ρ = 0.531 for LOA and 0.564 for HOA). Corneal biomechanical parameters including CH and CRF were found to be lower in the pterygium eyes, though not statistically significant (p value 0.60 and 0.59, respectively).

CONCLUSION

Pterygium leads to deterioration of visual performance not only by causing refractive and topographic changes but also by causing a significant increase in corneal wavefront aberrations.

Predictability of Intraocular Lens Power Calculation After Simultaneous Pterygium Excision and Cataract Surgery

This study was aimed to assess the predictability of intraocular lens (IOL) power calculation after simultaneous pterygium excision and phacoemulsification with IOL implantation. We retrospectively reviewed the clinical charts of 60 eyes of 60 consecutive patients (mean age ± standard deviation, 73.5 ± 7.0 years) who developed pterygium and cataract. We determined visual acuity (logMAR), manifest spherical equivalent, manifest astigmatism, corneal astigmatism, and mean keratometry, preoperatively and 3 months postoperatively. Corrected visual acuity was significantly improved from 0.19 ± 0.20 preoperatively to -0.06 ± 0.07 postoperatively (P < 0.001, Wilcoxon signed-rank test). Uncorrected visual acuity was also significantly improved from 0.62 ± 0.33 preoperatively to 0.31 ± 0.32 postoperatively (P < 0.001). At 3 months, 48% and 82% of the eyes were within ± 0.5 and ± 1.0 D, respectively, of the targeted correction. We found significant correlations of the prediction errors with the changes in the mean keratometry (Spearman signed-rank test, r = -0.535, P < 0.001) and with the pterygium size (r = -0.378, P = 0.033). Simultaneous pterygium and cataract surgery was safe and effective, and the accuracy was moderately predictable. However, it should be noted that a significant myopic shift occurred postoperatively, possibly resulting from the steepening of the cornea after pterygium removal, especially when the size of pterygium was large.

Objective optical quality analysis using double-pass technique in pterygium surgery

PURPOSE

To analyze objective optical quality changes after pterygium surgical excision using the Optical Quality Analysis System.

METHODS

Forty eyes with primary pterygium suitable for surgical treatment were included. Uncorrected distance visual acuity, corrected distance visual acuity (CDVA), objective scattering index (OSI), and cutoff frequency of the modulation transfer function (MTFcutoff) were recorded preoperatively and at 1 and 6 months postoperatively. Slit-lamp measurement of pterygium size was performed to classify them: small in group 1 and medium size/large in group 2. A paired comparative study of all data that included preoperative with 1-month results (comparison A), preoperative with 6-month results (comparison B), and 1 month with sixth-month results (comparison C) was performed.

RESULTS

In global analysis, uncorrected distance visual acuity and OSI showed significant changes in comparison A, all parameters in comparison B, and CDVA, OSI, and MTFcutoff in comparison C. When subdividing into groups, in group 1, there was significant improvement between preoperative uncorrected distance visual acuity value and those at 1 and 6 months. Significant improvement in CDVA, OSI, and MTFcutoff values were observed in comparisons B and C. In group 2, MTFcutoff values significantly improved in comparisons B and C. The comparison of mean values between each group at each evaluation showed a lower value for MTFcutoff at 1 month after surgery. A comparative analysis of the evolution between both groups based on pterygium size did not reveal significant differences.

CONCLUSIONS

Pterygium can undermine visual quality, and its excision provides significant improvement even at 6 months after surgery. Optical Quality Analysis System proved useful for postoperative outcomes.

The effect of pterygium surgery on wavefront analysis

Background:

Pterygium is a common disorder of the ocular surface. It causes vision impairment -usually irregular type astigmatism- through different mechanisms. In addition, it is believed that surgical excision of the pterygium improves visual problems. The appropriate method to investigate irregular astigmatism is using wavefront analysis. This study was aimed to evaluate wavefront analysis pre and post pterygium surgery.

Materials and Methods:

This study was performed on 32 patients who underwent surgical excision of pterygium in January 2012. Data were recorded and compared after pre and postoperative comprehensive ophthalmologic examinations including uncorrected and best corrected visual acuity, Orbscan, wavefront analysis and autorefraction to figure out the effects of surgery on different parameters.

Results:

Comparison of pre and postoperative parameters showed that surgical treatment of the pterygium improves numerous parameters significantly including uncorrected and best corrected visual acuity, spherical and cylinder refractive error, higher order aberration, quadrafoil (Z440), corneal astigmatism and 3 and 5 mm central zone corneal irregularity (all P-values < 0.0001). In addition, it improves vertical coma (P:0.003) and secondary astigmatism (Z420) (P:0.004).

Conclusion:

It is concluded that surgical excision of the pterygium improves visual acuity, refractive errors and most of the corneal topographic indices and wavefront analysis parameters.

The change in ocular higher-order aberrations after pterygium excision with conjunctival autograft: a 1-year prospective clinical trial

PURPOSE

To investigate the effects of pterygium excision with conjunctival autograft plus corneal polishing on ocular higher-order aberrations (HOAs) and to monitor the changes throughout the first postoperative year.

METHODS

A total of 18 eyes of 16 patients with primary pterygium who had an indication for surgical excision were included in the study. All patients underwent a detailed ophthalmologic examination preoperatively and at the third and twelfth postoperative months. Pterygium excision with conjunctival autograft plus corneal polishing was performed by the same surgeon (K.G.). Corneal topography and ocular HOAs were measured by NIDEK optical path difference scanning system ARK-10000 refractive power/corneal analyzer.

RESULTS

Root mean square values of total aberrations and total HOAs were found to be significantly decreased both at 3 and 12 months after an uneventful pterygium surgery. Although solely root mean square values of coma and trefoil revealed a statistically significant reduction in the third postoperative month (P=0.043 and P=0.018, respectively), after 1 year, all parameters (total coma: P<0.001; total trefoil: P=0.004; total quatrefoil: P=0.010; and total high astigmatism: P=0.016) except for total spherical aberration (P=0.236) were found to be lower when compared with the preoperative values.

CONCLUSION

Uneventful pterygium excision with conjunctival autograft plus corneal polishing can significantly reduce most of the pterygium-induced HOAs. Moreover, the reduced postoperative aberrations continue to change beyond the early postoperative period even into the 1-year postoperative period. Therefore, any refractive procedures should be postponed at least 1 year after the pterygium surgery until corneal stability occurs.

Effects of pterygium surgery on front and back corneal surfaces and anterior segment parameters

The purpose of this study was to evaluate the effects of pterygium surgery on front and back corneal surfaces and anterior segment parameters. This prospective study included 96 eyes with primary pterygium that underwent surgery. Preoperatively and at 1, 3, and 6 months postoperatively, Pentacam was used to evaluate front and back corneal surfaces, anterior chamber depth (ACD), anterior chamber angle (ACA) and anterior chamber volume (ACV). Mean simulated keratometry at the front corneal surface increased from 42.73 ± 2.21 D preoperatively to 44.45 ± 2.05 D at 1 month (P < 0.001); it then decreased to 44.32 ± 2.07 D at 3 months (P < 0.001) and 44.19 ± 2.10 D at 6 months (P = 0.01). There was no statistically significant change in mean simulated keratometry at the back corneal surface. Radius of the front corneal best-fit sphere (BFS) decreased from 7.99 ± 0.29 mm preoperatively to 7.77 ± 0.25 mm at 1 month postoperatively (P < 0.001), without further change up to 6 months. Radius of the back corneal BFS increased from 6.42 ± 0.24 mm preoperatively to 6.50 ± 0.24 mm at 1 month (P < 0.001), without further change. Postoperative changes in mean simulated keratometry and radii of BFS had statistically significant positive correlations with pterygium extension onto the cornea and grade of pterygium morphology but, not with the surgical technique. There were no significant changes in ACD, ACA, and ACV values after pterygium surgery. Furthermore, the spherical equivalent of manifest refraction changed from +0.75 ± 1.06 D preoperatively to -0.72 ± 1.33 D at 1 month postoperatively (P = 0.001), with no further significant change. In conclusion, after pterygium surgery there were significant changes in front mean keratometry and front and back corneal radii of BFS. These were correlated with preoperative pterygium size and morphology grade. No significant changes in anterior segment parameters were noted postoperatively.

Effect of pterygia on refractive indices, corneal topography, and ocular aberrations

PURPOSE

To investigate the effect of different sizes of pterygium on ocular aberrations along with corneal refractive changes, keratometry, and corneal topography.

METHODS

Forty eyes of 34 patients who had different sizes of primary nasal pterygium and 40 eyes of 22 age- and sex-matched healthy subjects without a clinical diagnosis of pterygium or pinguecula were enrolled in this study. All patients underwent a measurement of uncorrected and best spectacle-corrected visual acuities, corneal topography, and ocular aberrations. The pterygia sizes were measured with a slit lamp by using a slit beam of light.

RESULTS

All indices (topographic/refractive spherical and astigmatic values and topographic/refractive spherical equivalent) were higher in the pterygia group than in the control group. Both horizontal length (Rho: 0.64 and P < 0.001) and width of pterygia (Rho: 0.68 and P < 0.01) were found to be correlated with corneal astigmatism. When the root mean square values of ocular aberrations were compared among the groups (control, small, medium, and large size pterygia), differences were found to be statistically significant regarding all parameters including total (P < 0.001), tilt (P < 0.001), higher order aberrations (P < 0.001), total coma (P < 0.001), total trefoil (P < 0.001), total tetrafoil (P < 0.001), total spherical aberrations (P = 0.004), and higher order astigmatism (P < 0.001). Moreover, the root mean square values of ocular aberrations seem to strongly correlate with both horizontal length and width of pterygia.

CONCLUSIONS

Pterygia, particularly with larger sizes, seem to be correlated with increased ocular aberrations. Moreover, increase of ocular aberrations may become one of the indications for surgical treatment if this association is supported by further investigations.

Effect of pterygium surgery on corneal topography

PURPOSE

To evaluate the effect of successful pterygium surgery on corneal topography.

METHODS

Computerized corneal topography was performed on 20 eyes with pterygium before and 3 months after successful excision and limbo-conjunctival autograft surgery. Corneal shape, corneal spherical power, simulated keratometric astigmatism, surface regularity index (SRI), and surface asymmetry index (SAI) were assessed before and after surgery. Pre- and postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction spherical equivalent (MRSE) were also evaluated.

RESULTS

Changes in corneal shape were mainly a decrease in midline corneal flattening. Corneal spherical power was 41.65+/-3.29 diopters (D) (mean +/- SD) preoperatively and 44.58+/-1.55 D postoperatively (p=0.04). Simulated keratometric astigmatism was 5.47+/-3.45 D preoperatively and 1.79+/-1.52 D postoperatively (p=0.0005). SRI was 1.39+/-0.93 preoperatively and 1.10+/-0.57 postoperatively (p=0.03). SAI was 1.17+/-1.09 preoperatively and 0.75+/-0.73 postoperatively (p=0.02). UCVA was 0.31+/-0.33 preoperatively and 0.52+/-0.32 postoperatively (p=0.04). BSCVA was 0.73+/-0.20 preoperatively and 0.89+/-0.16 postoperatively (p=0.008). MRSE was -0.54+/-3.29 D preoperatively and -1.30+/-3.05 D postoperatively (p=0.45).

CONCLUSIONS

Corneal topographic changes caused by the pterygium are almost reversible after surgical treatment. Successful pterygium surgery significantly reduces topographic astigmatism, SRI, SAI, and corneal flattening. However, precise prediction of these refractive changes is not always accurate.

Plica Semilunaris Temporal Ectopia

PURPOSE

To study whether plica semilunaris (PS) temporal ectopia is associated with primary nasal pterygia and whether such hypothetical ectopia is linked to with-the-rule astigmatism so that a discussion of the clinical and surgical implications of such possible findings might take place.

METHODS

Cross-section observational study of 208 consecutive eyes of 152 cases and 169 eyes of 109 control subjects enrolled for 6 months. Four PS position grades were designed. Grade 1 features a grossly vertical PS position. Grades 2 and 3 involve temporal displacement and an abnormal PS tilt. Grade 4 involves PS obliteration with possible associated temporal caruncle dragging. Pterygium corneal encroachment, pterygium fleshiness, and manifest refraction were recorded.

RESULTS

PS position was significantly displaced temporally in pterygium-affected eyes (P = 2 x 10(-4)). Corneal encroachment (P = 2.1 x 10(-5)), pterygium fleshiness (P = 2.7 x 10(-5)), and age (P = 1.3 x 10(-2)) were positively correlated with PS position grades > 1. The presence of with-the-rule astigmatism was significantly linked to PS position grades > 1 (P = 0.01).

CONCLUSIONS

Primary nasal pterygia result in PS temporal ectopia, and PS position grades (more than grade 1) are linked to the presence of with-the-rule astigmatism. These findings are consistent with the exertion of tractional forces at both pterygium ends. In eye abduction, medial canthus structures (PS, caruncule) may be dragged temporally. Thus, pterygium-related corneal traction may not always significantly increase in eye abduction. PS temporal ectopia may influence the decision to remove PS during pterygium surgical excision.

Tear function and goblet cell density after pterygium excision

PURPOSE

To evaluate the short-term effect of pterygium excision on tear function and conjunctival goblet cell density.

METHODS

In all, 70 patients (70 eyes) with primary pterygia who underwent a bare-sclera procedure were enrolled in this study. Tear break-up time, Schirmer, and tear-ferning tests and conjunctival goblet cell density obtained by impression cytology were evaluated before and 1 month after surgery.

RESULTS

At 1 month postoperation, the tear break-up time (11.49+/-3.76 s) was significantly prolonged when compared with the preoperation tear break-up time (9.74+/-3.43 s, P=0.002). Before surgery, only 17% of the patients showed normal crystallization in the tear-ferning test. This proportion was significantly increased to 90% 1 month after surgery (P<0.001). There is no significant difference in the Schirmer test value between pre- and postsurgery (P>0.05). The mean goblet cell density in conjunctival impression specimens before surgery was 41.82+/-18.29/10 fields, which was increased significantly 1 month after surgery (P<0.001) with a mean cell density of 50.67+/-18.71/10 fields.

CONCLUSION

Tear function in patients with primary pterygium improves after pterygium excision, which indicates that pterygium has a close relationship with dry eye.

Corneal topographic changes in a case of limbal conjunctival carcinoma

PURPOSE

To describe topographic changes in a case of limbal conjunctival carcinoma.

METHODS

Corneal topography was performed before and 3 months after excision.

RESULTS

Preoperative topography revealed a localized flattening (37.1 diopters [D]) adjacent to the tumor and extending to the corneal apex, causing a 3-diopter asymmetric with-the-rule astigmatism. Preoperative corneal curvature was abnormally flat in all hemimeridians (average 40.8 D). During surgical excision, no corneal infiltration was found. Three months later, the astigmatism was 0.3 D, and corneal curvature had increased to normal values in all hemimeridians (45.5 D in the tumor area; average of all hemimeridians 45.5 D). Corneal steepening after tumor excision measured by topography almost doubled that observed in refraction.

CONCLUSION

The similarity with the patterns induced by pterygia, the lack of corneal infiltration, and the complete reversal of astigmatism after excision support the theory that tear pooling at the tumor apex is responsible for secondary astigmatism and diffuse corneal flattening. However, the irregularity induced by the tumor may affect the precision of topographic measurements.