Mean cycloplegic refractive error in emmetropic adults – The Tehran Eye Study / Error refractivo ciclopléjico medio en adultos emétropes: estudio ocular de Teherán

Purpose: In children under 20 years, refractive development targets a cycloplegic refractive error of +0.5 to +1.5D, while presbyopes over 40 years generally have non-cycloplegic errors of ≥ +1D. Some papers suggest these periods are separated by a period of myopic refractive error (i.e., ≤ –0.50D), but this remains unclear. Hence, this work investigates the mean cycloplegic refractive error in adults aged between 20 – 40 years. Methods: In 2002 a cross-sectional study with stratified cluster sampling was performed on the population of Tehran, providing cycloplegic and non-cycloplegic refractive error data for the right eyes of 3,576 participants, aged 30.6 ± 18.6 years (range: 1–86 years). After grouping these data into age groups of 5 years, the refractive error histogram of each group was fitted to a Bigaussian function. The mean of the central, emmetropized peak was used to estimate the mean refractive error without the influence of myopia. Results: The mean cycloplegic refractive error at the emmetropized peak decreased from +1.10 ± 0.11D (95 % confidence interval) to +0.50 ± 0.04D before 20 years and remains stable at that value until the age of 50 years. The non-cycloplegic refractive error also sees a stable phase at 0.00 ± 0.04D between 15 – 45 years. After 45 – 50 years both cycloplegic and non-cycloplegic refractive error become more hypermetropic over time, +1.14 ± 0.12D at 75 years. Conclusions: The cycloplegic refractive error in adults is about +0.50D between 20 – 50 years, disproving the existence of the myopic period at those ages.(AU)

The influence of variations in ocular biometric and optical parameters on differences in refractive error.

PURPOSE: To present a paraxial method to estimate the influence of variations in ocular biometry on changes in refractive error (S) at a population level and apply this method to literature data. METHODS: Error propagation was applied to two methods of eye modelling, referred to as the simple method and the matrix method. The simple method defines S as the difference between the axial power and the whole-eye power, while the matrix method uses more accurate ray transfer matrices. These methods were applied to literature data, containing the mean ocular biometry data from the SyntEyes model, as well as populations of premature infants with or without retinopathy, full-term infants, school children and healthy and diabetic adults. RESULTS: Applying these equations to 1000 SyntEyes showed that changes in axial length provided the most important contribution to the variations in refractive error (57%-64%), followed by lens power/gradient index power (16%-31%) and the anterior corneal radius of curvature (10%-13%). All other components of the eye contributed <4%. For young children, the largest contributions were made by variations in axial length, lens and corneal power for the simple method (67%, 23% and 8%, respectively) and by variations in axial length, gradient lens power and anterior corneal curvature for the matrix method (55%, 21% and 14%, respectively). During myopisation, the influence of variations in axial length increased from 54.5% to 73.4%, while changes in corneal power decreased from 9.82% to 6.32%. Similarly, for the other data sets, the largest contribution was related to axial length. CONCLUSIONS: This analysis confirms that the changes in ocular refraction were mostly associated with variations in axial length, lens and corneal power. The relative contributions of the latter two varied, depending on the particular population.

The potential influence of the ligament of Wieger on the crystalline lens shape.

This research uses mathematical modelling to evaluate the influence of the ligament of Wieger on the crystalline lens shape at rest, and during accommodation. An axisymmetric model of the anterior segment, including the ligament of Wieger, was created using the finite element method. Different conditions including variations of stiffness and positions of the ligament, with and without the ligament, were tested to see how they affected lens curvature and optical power. Adding the ligament of Wieger to the simulation had a noticeable impact on the optical power of the lens, particularly on the posterior surface power and total power. Ligament stiffness and width significant influenced the accommodative range of the eye by - 0.95D and - 2.39D for ligaments with the same and 3× the stiffness of the capsular bag, respectively. Ligament width and inner diameter had negligible effects on lens thickness but did have significant effects on posterior surface power and accommodation. In this simulation, we found that the ligament of Wieger can significantly affect the lens shape, both at rest and during accommodation, and may need to be considered in lens models.

Allowable movement of wavefront-guided contact lens corrections in normal and keratoconic eyes.

PURPOSE: The goal was to use SyntEyes modelling to estimate the allowable alignment error of wavefront-guided rigid contact lens corrections for a range of normal and keratoconic eye aberration structures to keep objectively measured visual image quality at or above average levels of well-corrected normal eyes. Secondary purposes included determining the required radial order of correction, whether increased radial order of the corrections further constrained the allowable alignment error and how alignment constraints vary with keratoconus severity. METHODS: Building on previous work, 20 normal SyntEyes and 20 keratoconic SyntEyes were fitted with optimised wavefront-guided rigid contact lens corrections targeting between three and eight radial orders that drove visual image quality, as measured objectively by the visual Strehl ratio, to near 1 (best possible) over a 5-mm pupil for the aligned position. The resulting wavefront-guided contact lens was then allowed to translate up to ±1 mm in the x- and y-directions and rotate up ±15°. RESULTS: Allowable alignment error changed as a function of the magnitude of aberration structure to be corrected, which depends on keratoconus severity. This alignment error varied only slightly with the radial order of correction above the fourth radial order. To return the keratoconic SyntEyes to average levels of visual image quality depended on maximum anterior corneal curvature (Kmax). Acceptable tolerances for misalignment that returned keratoconic visual image quality to average normal levels varied between 0.29 and 0.63 mm for translation and approximately ±6.5° for rotation, depending on the magnitude of the aberration structure being corrected. CONCLUSIONS: Allowable alignment errors vary as a function of the aberration structure being corrected, the desired goal for visual image quality and as a function of keratoconus severity.

Mean cycloplegic refractive error in emmetropic adults - The Tehran Eye Study.

PURPOSE: In children under 20 years, refractive development targets a cycloplegic refractive error of +0.5 to +1.5D, while presbyopes over 40 years generally have non-cycloplegic errors of ≥ +1D. Some papers suggest these periods are separated by a period of myopic refractive error (i.e., ≤ -0.50D), but this remains unclear. Hence, this work investigates the mean cycloplegic refractive error in adults aged between 20 - 40 years. METHODS: In 2002 a cross-sectional study with stratified cluster sampling was performed on the population of Tehran, providing cycloplegic and non-cycloplegic refractive error data for the right eyes of 3,576 participants, aged 30.6 ± 18.6 years (range: 1-86 years). After grouping these data into age groups of 5 years, the refractive error histogram of each group was fitted to a Bigaussian function. The mean of the central, emmetropized peak was used to estimate the mean refractive error without the influence of myopia. RESULTS: The mean cycloplegic refractive error at the emmetropized peak decreased from +1.10 ± 0.11D (95 % confidence interval) to +0.50 ± 0.04D before 20 years and remains stable at that value until the age of 50 years. The non-cycloplegic refractive error also sees a stable phase at 0.00 ± 0.04D between 15 - 45 years. After 45 - 50 years both cycloplegic and non-cycloplegic refractive error become more hypermetropic over time, +1.14 ± 0.12D at 75 years. CONCLUSIONS: The cycloplegic refractive error in adults is about +0.50D between 20 - 50 years, disproving the existence of the myopic period at those ages.

Definitions for Keratoconus Progression and Their Impact on Clinical Practice.

PURPOSE: There is currently no consensus on which keratoconus need cross-linking nor on how to establish progression. This study assessed the performance of diverse progression criteria and compared them with our clinical knowledge of keratoconus evolution. METHODS: This was a retrospective, longitudinal, observational study. Habitual progression criteria, based on (combinations of) keratometry (K MAX ), front astigmatism (A F ), pachymetry (P MIN ), or ABCD progression display, from 906 keratoconus patients were analyzed. For each criterion and cutoff, we calculated %eyes flagged progressive at some point (R PROG ), individual consistency C IND (%examinations after progression detection still considered progressive), and population consistency C POP (% eyes with CIND >66%). Finally, other monotonic and consistent variables, such as front steep keratometry (K 2F ), mean radius of the back surface (R mB ), and the like, were evaluated for the overall sample and subgroups. RESULTS: Using a single criterion (e.g., ∆K MAX >1D) led to high values of R PROG . When combining two, (K MAX and A F ) led to worse C POP and higher variability than (K MAX and P MIN ); alternative criteria such as (K 2F and R mB ) obtained the best C POP and the lowest variability ( P <0.0001). ABC, as defined by its authors, obtained R PROG of 74.2%. Using wider 95% confidence intervals (95% CIs) and requiring two parameters over 95CI reduced R PROG to 27.9%. CONCLUSION: Previous clinical studies suggest that 20% to 30% of keratoconus cases are progressive. This clinical R PROG value should be considered when defining KC progression to avoid overtreatment. Using combinations of variables or wider margins for ABC brings R PROG closer to these clinical observations while obtaining better population consistency than current definitions.

Longitudinal changes in crystalline lens thickness and power in children aged 6-12 years old.

OBJECTIVES: To determine the three-year changes in crystalline lens power (LP) and thickness (LT) in children and their associated factors. METHODS: Schoolchildren aged 6-12 years living in Shahroud, northeast Iran were examined in 2015 and 2018. The Bennett formula was used to calculate LP. Multiple generalized estimating equations (GEE) analysis was used for data analysis. RESULTS: Among the 8089 examined eyes, the mean LP in Phase 1 and 2, and the three-year change were 21.61 ± 1.47D, 21.00 ± 1.42D, and -0.61 ± 0.52D, respectively. The GEE model showed that negative shifts in LP were less pronounced with increasing age (ß = 0.176; p < 0.001), and were also less noticeable in hyperopes compared to emmetropes (ß = 0.120; p < 0.001). The changes in LP decreased when outdoor activity increased among urban residents (ß = 0.013; p = 0.039), while it increased in rural area (ß = -0.020; p = 0.047). Mean three-year change in LT was 0.002 ± 0.13 mm. Female sex and aging by one year increased the LT by 0.022 mm (P < 0.001). However, LT decreased in 6-8-year-olds, while it increased in 10-12-year-old children, both in a linear fashion. The change in LT was less in myopes than in emmetropes (ß = -0.018, P-value = 0.010). CONCLUSION: LP decreases after three years in 6 to 12-year-old children. LT increases slightly after three years in 6 to 12-year-old children. The changes in LP and LT were associated with the refractive errors, place of residence, age and gender and outdoor activity time.

Retinal shadows produced by myopia control spectacles.

PURPOSE: To analyse ocular coherence tomography (OCT) images of the retinal shadows caused by defocus and diffusion optics spectacles. METHODS: One eye was fitted successively with the Hoya Defocus Incorporated Multiple Segments (DIMS) spectacle lens, two variations of the +3.50 D peripheral add spectacle (DEFOCUS) and the low-contrast dot lens (Diffusion Optics Multiple Segments, DOMS); each at a vertex distance of 12 mm. Simultaneously, a retinal image of the macular region with central fixation was obtained using infrared OCT. The corneal power and intraocular distances were determined using an optical biometer. RESULTS: The retinal images for the DIMS and DOMS lenses showed patterns of obvious retinal shadows in the periphery, while the central 10-11° remained clear. The DEFOCUS lens produced a darkened peripheral area. Dividing the size of the retinal pattern, measured with the calliper of the OCT software, by the actual size on the spectacle lens gave a magnification of -0.57 times. This is consistent with the incoming OCT beam being imaged to a position approximately 31 mm beyond the front of the eye. [Correction added on 26 October 2023 after first online publication: The preceding paragraph was corrected.] CONCLUSION: With device-specific correction, retinal OCT images can help visualise the regions affected by the defocus or lowered contrast induced by myopia control spectacles. This is of potential value for improving myopia therapies.

New keratoconus staging system based on OCT.

PURPOSE: To establish a numerical spectral-domain optical coherence tomography (SD-OCT)-based keratoconus (KC) staging system and compare it with existing KC staging systems. SETTING: Eye Hospital of Wenzhou Medical University, Wenzhou, China. DESIGNS: Retrospective case-control study. METHODS: Scheimpflug tomography, air-puff tonometry, and SD-OCT were performed on 236 normal and 331 KC eyes. All SD-OCT-derived parameters of the corneal epithelium and stroma were evaluated based on their receiver operating characteristic (ROC) curves, area under the curve (AUC), sensitivity, and specificity to discriminate between normal and KC eyes. The best performing parameters were subsequently used to create an OCT-based staging system, which was compared with existing tomographic and biomechanical staging systems. RESULTS: 236 eyes from 236 normal patients and 331 eyes from 331 KC patients of different stages were included. The highest ranked AUC ROC SD-OCT parameters, derived from stroma and epithelium, were stroma overall minimum thickness (ST: AUC 0.836, sensitivity 90%, specificity 67%) and epithelium overall SD (EP: AUC 0.835, sensitivity 75%, specificity 78%). A numerical SD-OCT staging system called STEP including 2 parameters-"ST" and "EP"-with 5 stages was proposed. CONCLUSIONS: The new SD-OCT-based KC staging system is the first to take the epithelium with its sublayer stroma information into account, showing a strong agreement to the existing staging systems. This system could be incorporated into daily practice, potentially leading to an overall improvement in KC treatment and follow-up management.

IMI-Onset and Progression of Myopia in Young Adults.

Myopia typically starts and progresses during childhood, but onset and progression can occur during adulthood. The goals of this review are to summarize published data on myopia onset and progression in young adults, aged 18 to 40 years, to characterize myopia in this age group, to assess what is currently known, and to highlight the gaps in the current understanding. Specifically, the peer-reviewed literature was reviewed to: characterize the timeline and age of stabilization of juvenile-onset myopia; estimate the frequency of adult-onset myopia; evaluate the rate of myopia progression in adults, regardless of age of onset, both during the college years and later; describe the rate of axial elongation in myopic adults; identify risk factors for adult onset and progression; report myopia progression and axial elongation in adults who have undergone refractive surgery; and discuss myopia management and research study design. Adult-onset myopia is common, representing a third or more of all myopia in western populations, but less in East Asia, where onset during childhood is high. Clinically meaningful myopia progression continues in early adulthood and may average 1.00 diopters (D) between 20 and 30 years. Higher levels of myopia are associated with greater absolute risk of myopia-related ocular disease and visual impairment, and thus myopia in this age group requires ongoing management. Modalities established for myopia control in children would be options for adults, but it is difficult to predict their efficacy. The feasibility of studies of myopia control in adults is limited by the long duration required.

Combinations of Scheimpflug tomography, ocular coherence tomography and air-puff tonometry improve the detection of keratoconus.

PURPOSE: To determine whether combinations of devices with different measuring principles, supported by artificial intelligence (AI), can improve the diagnosis of keratoconus (KC). METHODS: Scheimpflug tomography, spectral-domain optical coherence tomography (SD-OCT), and air-puff tonometry were performed in all eyes. The most relevant machine-derived parameters to diagnose KC were determined using feature selection. The normal and forme fruste KC (FFKC) eyes were divided into training and validation datasets. The selected features from a single device or different combinations of devices were used to develop models based on random forest (RF) or neural networks (NN) trained to distinguish FFKC from normal eyes. The accuracy was determined using receiver operating characteristic (ROC) curves, area under the curve (AUC), sensitivity, and specificity. RESULTS: 271 normal eyes, 84 FFKC eyes, 85 early KC eyes, and 159 advanced KC eyes were included. A total of 14 models were built. Air-puff tonometry had the highest AUC for detecting FFKC using a single device (AUC = 0.801). Among all two-device combinations, the highest AUC was accomplished using RF applied to selected features from SD-OCT and air-puff tonometry (AUC = 0.902), followed by the three-device combination with RF (AUC = 0.871) with the best accuracy. CONCLUSION: Existing parameters can precisely diagnose early and advanced KC, but their diagnostic ability for FFKC could be optimized. Applying an AI algorithm to a combination of air-puff tonometry with Scheimpflug tomography or SD-OCT could improve FFKC diagnostic ability. The improvement in diagnostic ability by combining three devices is modest.

Ray tracing optimization: a new method for intraocular lens power calculation in regular and irregular corneas.

To develop a novel algorithm based on ray tracing, simulated visual performance and through-focus optimization for an accurate intraocular lens (IOL) power calculation. Custom-developed algorithms for ray tracing optimization (RTO) were used to combine the natural corneal higher-order aberrations (HOAs) with multiple sphero-cylindrical corrections in 210 higher order statistical eye models for developing keratoconus. The magnitude of defocus and astigmatism producing the maximum Visual Strehl was considered as the optimal sphero-cylindrical target for IOL power calculation. Corneal astigmatism and the RMS HOAs ranged from - 0.64 ± 0.35D and 0.10 ± 0.04 µm (0-months) to - 3.15 ± 1.38D and 0.82 ± 0.47 µm (120-months). Defocus and astigmatism target was close to neutral for eyes with low amount of HOAs (0 and 12-months), where 91.66% of eyes agreed within ± 0.50D in IOL power calculation (RTO vs. SRK/T). However, corneas with higher amounts of HOAs presented greater visual improvement with an optimized target. In these eyes (24- to 120-months), only 18.05% of eyes agreed within ± 0.50D (RTO vs. SRK/T). The power difference exceeded 3D in 42.2% while the cylinder required adjustments larger than 3D in 18.4% of the cases. Certain amounts of lower and HOAs may interact favourably to improve visual performance, shifting therefore the refractive target for IOL power calculation.

Refractive development I: Biometric changes during emmetropisation.

PURPOSE: Although there are many reports on ocular growth, these data are often fragmented into separate parameters or for limited age ranges. This work intends to create an overview of normal eye growth (i.e., in absence of myopisation) for the period before birth until 18 years of age. METHODS: The data for this analysis were taken from a search of six literature databases using keywords such as "[Parameter] & [age group]", with [Parameter] the ocular parameter under study and [age group] an indication of age. This yielded 34,409 references that, after screening of title, abstract and text, left 294 references with usable data. Where possible, additional parameters were calculated, such as the Bennett crystalline lens power, whole eye power and axial power. RESULTS: There were 3422 average values for 17 parameters, calculated over a combined total of 679,398 individually measured or calculated values. The age-related change in refractive error was best fitted by a sum of four exponentials (r2  = 0.58), while all other biometric parameters could be fitted well by a sum of two exponentials and a linear term ('bi-exponential function'; r2 range: 0.64-0.99). The first exponential of the bi-exponential fits typically reached 95% of its end value before 18 months, suggesting that these reached genetically pre-programmed passive growth. The second exponentials reached this point between 4 years of age for the anterior curvature and well past adulthood for most lenticular dimensions, suggesting that this part represents the active control underlying emmetropisation. The ocular components each have different growth rates, but growth rate changes occur simultaneously at first and then act independently after birth. CONCLUSIONS: Most biometric parameters grow according to a bi-exponential pattern associated with passive and actively modulated eye growth. This may form an interesting reference to understand myopisation.

Investigating the Link Between Visual Quality and Vision-Related Quality of Life in Patients With Keratoconus.

PURPOSE: The purpose of the study was to investigate the optical and visual determinants of vision-related quality of life (VR-QoL) in patients with keratoconus. METHODS: A cross-sectional case-control study was conducted at the Department of Ophthalmology, Antwerp University Hospital, Belgium. Patients previously diagnosed with keratoconus and healthy emmetropic or ametropic volunteers were included. Patients younger than 18 years, with ametropia of more than ±10 D, or with a history of corneal surgery or relevant ocular comorbidity limiting visual acuity were excluded. Assessment included autorefraction, high-contrast visual acuity testing, corneal imaging, intraocular straylight analysis, contrast sensitivity, aberrometry, and the National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25). The Rasch-modified visual functioning scale (VFS) and socio-emotional scale were used to quantify VR-QoL. Stepwise linear regression was used to investigate the association between the clinical variables and VR-QoL. RESULTS: Seventy-seven patients with keratoconus (77 pairs of eyes) and 77 age-matched and sex-matched controls were included in the study. The scores on the VFS and the SES were significantly lower in patients with keratoconus compared with controls ( P < 0.001). Higher-order and lower-order aberrations, high-contrast visual acuity, and contrast sensitivity were poorer in patients with keratoconus ( P < 0.001). Bivariate analyses showed that spectacle-corrected high-contrast visual acuity, higher spatial frequency contrast sensitivity, and higher-order aberration metrics were strong predictors of SES ( P < 0.001) and of VFS ( P < 0.001). Higher-order aberration of the worse eye was the strongest predictor for both SES (b = 0.310, P < 0.001) and VFS (b = 0.638, P < 0.001) on stepwise regression. Contrast sensitivity was not included in the stepwise regression because of insufficient data in the keratoconus group (33/77 patients; 42.9%). CONCLUSIONS: Both higher and lower aberration showed a strong correlation with VR-QoL, surpassing high-contrast visual acuity. These findings underline the importance of visual quality measures within keratoconus research and clinical care.

Technical notes on peripheral refraction, peripheral eye length and retinal shape determination.

PURPOSE: To give an overview of the misconceptions and potential artefacts associated with measuring peripheral refractive error and eye length, the use of these measures to determine the retinal shape and their links to myopia development. Several issues were identified: the relationship between peripheral refractive error and myopia development, inferring the retinal shape from peripheral refraction or eye length patterns, artefacts and accuracy when measuring peripheral eye length using an optical biometer. METHODS: A theory was developed to investigate the influence of artefacts in measuring peripheral eye length and on using peripheral eye length to make inferences about retinal shape. RESULTS: When determining peripheral axial length, disregarding the need to realign instruments with mounted targets can lead to incorrect field angles and positions of mounted targets by more than 10% for targets placed close to the eye. Peripheral eye length is not a good indicator of the effects of myopia or of treatment for myopia development because eyes of different lengths but with the same retinal shape would be interpreted as having different retinal shapes; the measurement leads to overestimates of changes in retinal curvature as myopia increases. Determining peripheral eye length as a function of estimated retinal height rather than field angle will halve the magnitude of the artefact. The artefact resulting from the peripheral use of biometers with an on-axis calibration is modest and can be ignored. CONCLUSION: There are significant issues with peripheral measurements of the refractive error and eye length that must be considered when interpreting these data for myopia research. Some of these issues can be mitigated, while others require further investigation.

Influence of rigid lens decentration and rotation on visual image quality in normal and keratoconic eyes.

PURPOSE: To investigate whether the movement of a rigid sphero-cylindrical contact lens has a greater impact on the visual image quality in highly aberrated eyes than in normal eyes. METHODS: For 20 normal and 20 keratoconic SyntEyes, a previously determined best sphero-cylindrical rigid lens was permitted to shift by up to ±1 mm from the line of sight and rotate up to ±15°. Each of the 52,111 lens locations sampled was ray-traced to determine the influence on the wavefront aberration. In turn, the logarithm of visual Strehl ratio (log10 [VSX]) was calculated for each aberration structure and was used to estimate the associated changes in logMAR visual acuity. Finally, contour surfaces of two-letter change in visual acuity were plotted in three-dimensional misalignment space, consisting of decentrations in the x and y directions and rotation, and volumes within these surfaces were calculated. RESULTS: The variations in image quality within the misalignment space were unique to each eye. A two-letter loss was generally reached with smaller misalignments in keratoconic eyes (10.5 ± 4.7° of rotation or 0.27 ± 0.13 mm of shift) than in normal eyes (13.4 ± 1.8° and 0.39 ± 0.15 mm, respectively) due to larger cylindrical errors. For keratoconic eyes, on average, 14.4 ± 14.9% of misalignment space saw VSX values above the lower normal VSX threshold, well below the values of normal eyes of 48.5 ± 18.5%. In some eyes, a specific combination of lens shift and lens rotation away from the line of sight leads to a simulated improvement in visual image quality. CONCLUSION: Variations in visual image quality due to the misalignment of rigid sphero-cylindrical contact lens corrections are larger for keratoconic eyes than for normal eyes. In some cases, a specific misalignment may improve visual image quality, which could be considered in the design of the next generation of rigid contact lenses.

Influence of Specialty Contact Lens Wear on Posterior Corneal Tomography in Keratoconus Subjects.

OBJECTIVE: To evaluate the effect of specialty contact lens (CL) wear on posterior corneal tomography in keratoconus subjects. METHODS: Patients with keratoconus who were wearing specialty CL were included in this retrospective cohort study. Tomographic parameters were evaluated with Scheimpflug imaging (Pentacam HR) before lens fitting and immediately after removal of CLs worn habitually for a period of several months. Subjects were divided into groups, according to type of lens (corneal, scleral, and hybrid) and keratoconus severity based on Belin/Ambrosio D (BAD-D) score, for further analysis. RESULTS: Thirty-four eyes of 34 subjects diagnosed with keratoconus were included. Mean duration of habitual CL wear was 7.0±0.3 months. For the entire cohort, a small increase in flat keratometric reading at the anterior corneal surface (K1F; P =0.032) and at the posterior surface (K1B; P =0.041) was found. In the corneal CL group (10 eyes; 29.4%), flattening of the anterior corneal curvature was detected (K max ; P =0.015). An increase in K1B value was seen in the scleral CL group (15 eyes; 44.1%) ( P =0.03). Combined topometric indices showed a small but significant difference in the entire cohort ( P <0.05) and in the subgroups of corneal CL wear and of moderate keratoconus (BAD-D score≥7). CONCLUSION: Various types of specialty CLs exert a differential influence on corneal parameters. A small steepening of keratometry at the posterior surface (K1B) was observed in the scleral lens group. Although corneal lens wear flattens the anterior cornea (K max ), it does not significantly alter the posterior corneal surface.

Combining Spectral-Domain OCT and Air-Puff Tonometry Analysis to Diagnose Keratoconus.

PURPOSE: To investigate the diagnostic capacity of spectral-domain optical coherence tomography (SD-OCT) combined with air-puff tonometry using artificial intelligence (AI) in differentiating between normal and keratoconic eyes. METHODS: Patients who had either undergone uneventful laser vision correction with at least 3 years of stable follow-up or those who had forme fruste keratoconus (FFKC), early keratoconus (EKC), or advanced keratoconus (AKC) were included. SD-OCT and biomechanical information from air-puff tonometry was divided into training and validation sets. AI models based on random forest or neural networks were trained to distinguish eyes with FFKC from normal eyes. Model accuracy was independently tested in eyes with FFKC and normal eyes. Receiver operating characteristic (ROC) curves were generated to determine area under the curve (AUC), sensitivity, and specificity values. RESULTS: A total of 223 normal eyes from 223 patients, 69 FFKC eyes from 69 patients, 72 EKC eyes from 72 patients, and 258 AKC eyes from 258 patients were included. The top AUC ROC values (normal eyes compared with AKC and EKC) were Pentacam Random Forest Index (AUC = 0.985 and 0.958), Tomographic and Biomechanical Index (AUC = 0.983 and 0.925), and Belin-Ambrósio Enhanced Ectasia Total Deviation Index (AUC = 0.981 and 0.922). When SD-OCT and air-puff tonometry data were combined, the random forest AI model provided the highest accuracy with 99% AUC for FFKC (75% sensitivity; 94.74% specificity). CONCLUSIONS: Currently, AI parameters accurately diagnose AKC and EKC, but have a limited ability to diagnose FFKC. AI-assisted diagnostic technology that uses both SD-OCT and air-puff tonometry may overcome this limitation, leading to improved treatment of patients with keratoconus. [J Refract Surg. 2022;38(6):374-380.].

Influence of eye tilt on corneal densitometry.

PURPOSE: To investigate whether Pentacam densitometry readings are affected by corneal tilt. METHODS: In a prospective study, the right eyes of 86 healthy participants aged 42.8 ± 20.0 years (range 18-79 years) were imaged using Scheimpflug tomography. Elevation maps were exported to calculate corneal tilt using custom-made software, and densitometry readings were acquired directly from the corneal densitometry analysis add-on to the standard software Oculus Pentacam HR. Simple mediation analysis was applied to study age as a confounding factor in the correlation between corneal tilt and corneal densitometry. RESULTS: Corneal tilt and corneal densitometry are not independent from one another because age is significantly correlated with both corneal tilt (r = 0.50, p < 0.001) and corneal densitometry (r = 0.91, p < 0.001). Only 3.8% of the correlation between tilt and densitometry operates directly, while the remaining 96.2% depends on age. CONCLUSIONS: Corneal tilt plays a role in corneal densitometry readings, even though the interaction is strongly influenced by age. Age is a well-known factor in densitometry readings that should be taken into consideration when interpreting Scheimpflug densitometry.