Process and Outcomes of Fitting Corneoscleral Profilometry-Driven Scleral Lenses for Patients With Ocular Surface Disease.

OBJECTIVES: To assess the feasibility of obtaining cornea scleral profile (CSP) measurements using Scheimpflug imaging and report on the fitting process of free-form custom scleral lenses (SLs) for patients with ocular surface disease (OSD). METHODS: This prospective study of patients fit with free-form SLs collected data on the following: demographics, indications for wear, corneal and scleral tomography, scan acquisition process, and SL fitting process. RESULTS: Cornea scleral profile scans were acquired on 15 eyes of nine patients. Mean scan time for right eyes was 10.7, and 9.7 min for left eyes. A mean of 2.9 follow-up visits were required to complete SL fitting, with a mean of 2.1 lenses ordered. One eye did not tolerate lens wear, and one eye could not be fit using the CSP scan because of insufficient data. The initial lens ordered was dispensed at the first follow-up visit for seven of the remaining 13 eyes, all of which were ultimately fit successfully in free-form lenses. CONCLUSIONS: In this study of profilometry-guided SL fitting for eyes with OSD and low magnitude corneal astigmatism, the number of lenses and follow-up visits required were similar to outcomes of previous studies that described the diagnostic approach to SL fitting. In addition, imaging technology does not negate the need for skilled clinical observation while fitting SLs.

The influence of eyelid pressure and eye contour factors on rigid corneal contact lens fitting.

PURPOSE: This study aimed to investigate the impact of eyelid pressure (ELP) and eye contour factors on rigid corneal contact lens fitting. METHODS: This prospective cross-sectional study involved 20 participants (one eye per person). Rigid corneal contact lenses with three different base curves were selected for each participant. The base curves were calculated according to the average keratometry value. The original value and its variations (+0.1 mm and - 0.1 mm) were considered. Eye contour factors, lens decentration under natural eye position (LD I) and full eyelid exposure (LD II), and lens vertical movement were taken by a Canon camera mounted on a digital slit lamp biomicroscope. Upper and lower ELPs were measured by a novel blepharo-tensiometer. RESULTS: The mean values of LD I, LD II, and lens vertical movement significantly increased as the base curve increased (P＜0.001, ＜0.001, and = 0.005). Upper ELP was positively correlated with lens vertical movement of the three base curves (P = 0.047, 0.001, and 0.004). Furthermore, upper ELP (odds ratio [OR]: 1.039; 95 % confidence [CI]: 1.009-1.069; P = 0.009) and flat keratometry values (OR: 0.873; 95 % CI: 0.786-0.969; P = 0.011) independently influenced lens vertical movement. CONCLUSIONS: ELP and base curve independently influenced rigid corneal contact lens fitting. Thus, ELP should be considered during rigid corneal contact lens fitting in clinical practice.

Case Report: Remote Scleral Lens Fitting for High Toric Scleras in a Keratoconus Patient.

SIGNIFICANCE: Technology plays a crucial role in customizing scleral lenses and improving lens alignment, especially in challenging scleral shapes. In addition, remote fitting technology allows optometrists to extend their expertise globally, empowering patients to access to customized lenses without travel expenses. PURPOSE: The objective of this study was to document the difficulties encountered in fitting a scleral lens in a patient with keratoconus and pronounced scleral toricity. In addition, the study aimed to present the successful remote fitting achieved by using advanced technology. CASE REPORT: An Irish male patient diagnosed with keratoconus exhibited high scleral toricity. Generally, keratoconus eyes often exhibit significant scleral asymmetry associated with cone decentration and disease severity. Improperly aligned scleral lenses can lead to regional changes in scleral shape, lens decentration, discomfort, and visual disturbances. Indeed, previous scleral lens fits were unsuccessful because of these issues. Corneoscleral profilometry was acquired in Ireland and then used in Italy to design customized lenses, which were then delivered to the patient's optometrist in Ireland. The first lenses designed and delivered demonstrated excellent overall performance without requiring adjustments. CONCLUSIONS: This report highlights the importance of corneoscleral profilometry to increase efficiency and reduce lens reorders and chair time, and the remote fitting in overcoming barriers to accessing specialized lens fitting.

Novel deep learning approach to estimate rigid gas permeable contact lens base curve for keratoconus fitting.

INTRODUCTION: Rigid gas permeable contact lenses (RGP) are the most efficient means of providing optimal vision in keratoconus. RGP fitting can be challenging and time-consuming for ophthalmologists and patients. Deep learning predictive models could simplify this process. OBJECTIVE: To develop a deep learning model to predict the base curve (R0) of rigid gas permeable contact lenses for keratoconus patients. METHODS: We conducted a retrospective study at the Rothschild Foundation Hospital between June 2012 and April 2021. We included all keratoconus patients fitted with Menicon Rose K2® lenses. The data was divided into a training set to develop the model and a test set to evaluate the model's performance. We used a U-net architecture. The raw matrix of anterior axial curvature in millimeters was extracted from Scheimpflug examinations for each patient and used as input for the model. The mean absolute error (MAE) between the prediction and the prescribed R0 was calculated. Univariate and multivariate analyses were conducted to assess the model's errors. RESULTS: Three hundred fifty-eight eyes from 202 patients were included: 287 eyes were included in the training dataset, and 71 were included in the testing dataset. Our model's Pearson coefficient of determination (R2) was calculated at 0.83, compared to 0.75 for the manufacturer's recommendation (mean keratometry, Km). The mean square error of our model was calculated at 0.04, compared to 0.11 for Km. The predicted R0 MAE (0.16 ± 0.13) was statistically significantly different from the Km MAE (0.23 ± 0.23) (p = 0.02). In multivariate analysis, an apex center outside the central 5 mm region was the only factor significantly increasing the prediction absolute error. CONCLUSION: Our deep learning approach demonstrated superior precision in predicting rigid gas permeable contact lens base curves for keratoconus patients compared to the manufacturer's recommendation. This approach has the potential to be particularly beneficial in complex fitting cases and can help reduce the time spent by ophthalmologists and patients during the process.

Average Scleral Lens Replacement Period at a Tertiary Care Hospital.

OBJECTIVE: To evaluate the average scleral lens replacement period at a tertiary care hospital. METHODS: Patients were identified retrospectively through electronic medical records. Inclusion criteria included scleral lens patients treated at the USC Department of Ophthalmology who had reordered a scleral lens at least once in one eye. Lens order histories were evaluated, and statistical analysis included a multivariable, mixed-methods, linear, regression model. RESULTS: Two hundred fifty-one patients (120 men and 131 women; average age 57.1±17.4 years, range 9-93 years) and a total of 445 eyes (227 OD, 218 OS; 199 irregular corneas, 246 ocular surface disease) were included. The average replacement period for a scleral lens was 23.9±14.3 months (range 5-2,617 days). Patients with greater scleral lens experience had a statistically significant increase in their average scleral lens replacement period; for every one year of additional experience wearing scleral lenses, average replacement period increased by 30.7 days ( P =0.001). There was no statistically significant correlation between average scleral lens replacement period and sex, diagnosis, prior outside scleral lens treatment, lens brand, or lens diameter. CONCLUSION: The average scleral lens replacement period in this patient cohort at a tertiary care hospital was 23.9±14.3 months (1.99±1.19 years). Further studies are needed to better understand the impact of scleral lens age on ocular health and vision. Certainly, proper scleral lens training and education are essential to ensure optimal lens condition and treatment outcomes.

Evidence of Contact Lenses for Vision Rehabilitation in Corneal Diseases: A Review.

OBJECTIVES: To evaluate the efficacy and safety of contact lenses (CL) as a therapeutic option for patients affected by a corneal disease and to determinate which is the best lens modality for each disease. METHODS: A literature review using PubMed was performed. All relevant articles published during the last 15 years have been included. RESULTS: Various studies point to CL as the best therapeutic option for some corneal diseases and even as an alternative to surgery in some cases. After fitting, patients show an improvement in their functional vision and quality of life, in some cases being able to drive or work again. CONCLUSIONS: There is a lack of scientific evidence to determine which lens modality is suitable for each corneal pathology. Currently, according to this review, the reason for choosing between the different options depends on the severity of symptoms, and it is worth mentioning that scleral lenses seem to be the best option in advanced stages of disease. However, the expertise of professionals is also an important factor at the time of choosing a particular CL modality. Standardized criteria are still necessary for correct selection of lens modality for a correct management of the disease.

Short partial doffs of release/relock sockets may effectively stabilize limb fluid volume in prosthesis users with transtibial amputation.

BACKGROUND: A challenge often faced by people with lower extremity amputation is management of prosthetic socket fit due to changes in fluid volume within their residual limb. Prior research suggests that intermittently doffing the prosthetic socket may help stabilize daily residual limb fluid volume. METHODS: To assess the effects of partial doff duration on residual limb fluid volume retention, participants with transtibial amputation were tested by walking on a treadmill in a controlled, laboratory setting under three conditions. An automated system to release the locking pin and enlarge the socket was used to produce the partial doffing. Percent limb fluid volume changes after partial doffing for 4 min (Short Rest) and for 10 min (Long Rest) were compared with no partial doffing (No Release). Limb fluid volume was monitored using bioimpedance analysis. FINDINGS: Mean percent fluid volume changes in the posterior region were  -1.2% for No Release, 2.7% for Short Rest, and 1.0% for Long Rest. Short and Long Rests had larger increases than No Release (P = 0.005 and 0.03, respectively); Short and Long Rests were not statistically different (P = 0.10). Eight of the thirteen participants experienced a higher percent fluid volume gain for both release protocols while four experienced a higher percent fluid volume gain for only one release protocol. INTERPRETATION: A partial doff duration as short as 4 min may be an effective strategy to stabilize limb fluid volume in prosthesis users with transtibial amputation. Trials in at-home settings should be pursued.

The Comparison of Soft HydroCone (Toris K) Silicone Hydrogel and Rigid Gas-Permeable Contact Lenses in Patients With Posterior Microphthalmos.

OBJECTIVE: To evaluate and compare soft HydroCone (Toris K) silicone hydrogel and rigid gas-permeable contact lenses (RGPCLs) in patients with posterior microphthalmos (PMs), for visual rehabilitation and comfort. METHODS: The records of 11 patients who were followed up in our hospital with the diagnosis of PM and were fitted with both Toris K and RGPCLs in our contact lens department were reviewed retrospectively. Patient age, gender, axial length (AL), topographic keratometry (K) values and best-corrected visual acuity (BCVA) with both lens types and subjective lens comfort status were recorded. RESULTS: A total of 22 eyes of 11 patients with a mean age of 20.9±11.1 years were included in the study. The mean AL were 16.01±0.1 and 15.9±0.2 mm in the right and left eyes, respectively. Mean K1 and K2 were 48.6±2.2 and 49.4±2.2 D, respectively. Mean logMAR BCVA of the 22 eyes before contact lens fitting was 0.63±0.56 with spectacle. After Toris K and RGPCLs fitting, mean logMAR BCVA were 0.43±0.20 and 0.35±0.25, respectively. Both lenses provided better visual acuity than spectacles; RGPCLs also provided significantly better visual acuity than HydroCone lens ( P <0.05). Eight of 11 patients (73%) had ocular discomfort with RGPLs, and there was no complaint with Toris K. CONCLUSIONS: The corneal surfaces are steeper in patients with PMs than in normal population. For that reason, their vision should be rehabilitated by special design keratoconus lenses like Toris K and RGPCLs. Although vision rehabilitation seems better with RGPCLs, these patients prefer Toris K more because of discomfort.

Scleral lens prescription and management practices: Emerging consensus.

PURPOSE: To describe international scleral lens prescription and management practices across multiple practice types. METHODS: For this cross-sectional study, scleral lens practitioners were asked to complete an electronic survey that requested information about a single scleral lens patient. Data collected included practitioner demographics (practice type, country, years of experience) and patient indications for scleral lens wear, fitting process, lens design, and care products. RESULTS: Data were collected for 259 patients (419 eyes). Most participants (60%) practiced in the US, 75% worked primarily in community practice, and 58% claimed more than 5 years' experience fitting scleral lenses. Indications for scleral lens wear were corneal irregularity (87%), ocular surface disease (9%), and uncomplicated refractive error (4%). During the fitting process, the mean (SD) number of lenses ordered was 2.4 (1.6) (range, 1-16 lenses) during 3.8 (2.4) visits (range, 1-18 visits). Of patients, 62% used a daily surfactant cleaner, 47% used hydrogen peroxide disinfection, and 67% used single-use vials of nonpreserved saline. Mean lens diameter was 16.2 (1.1) mm (range, 11.8-23.0 mm). The landing zones were spherical (64%), toric (26%), quadrant-specific (7%), and custom (3%) designs. Optical power was spherical in 70%, toric in 27%, and higher-order aberration correcting in 3% of lenses. Only 5 lenses had multifocal optics. CONCLUSIONS: General consensus regarding prescribing patterns (lens design, wearing schedules, care products) between US vs non-US, community vs academic, and new vs established providers is reported in this study. Relatively low percentages of patients wearing lenses with advanced landing zones or optical designs suggest that these new options have not been widely adopted.

The Dynamic Tracheoesophageal Prosthesis Length.

OBJECTIVE: In a postlaryngectomy patient, tracheoesophageal (TE) speech is considered to be the most effective and preferred method of communication. Previous research has demonstrated that despite an appropriately sized TE prosthesis placement at the time of puncture, there are a portion of patients that require resizing postoperatively. The purpose of this study was to report on the variability of the tracheoesophageal prosthesis length. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary care academic medical center. METHODS: This was a retrospective chart review of 62 patients who underwent secondary tracheoesophageal puncture (TEP) at a tertiary care academic medical center from January 2008 to November 2019. Patient demographic information, average changes in prosthesis length, number of prosthesis adjustments, and timing of prosthesis exchanges were collected. RESULTS: 62 patients met criteria for study inclusion. Mean age was 61.96 years old with 49 being male (79%) and 13 (21%) females. Overall change in prosthesis length was - 3.85 mm ± 3.58 with time to first prosthesis change at 2.29 months ± 2.73. There was an average of 4.37 changes ± 3.43 before reaching a stable length. Twenty-six patients (41.9%) had increases in their prosthesis length resulting in closure of the tracheoesophageal fistula requiring seven patients (11.3%) to return to the operating room for repuncturing. History of smoking (P = 0.02), Blom-Singer prosthesis type (P = 0.03), and larger diameter (P = 0.01) appeared to be predisposing factors for a fluctuating prosthesis length. CONCLUSION: Tracheoesophageal prosthesis length decreases over time for secondary punctures, requiring adjustments with a speech language pathologist. There are a clinically significant portion that have fluctuations in prosthesis length resulting in an increased risk for requiring re-puncturing.

Feasibility testing of a novel prosthetic socket sensor system.

PURPOSE: Poorly fitting prosthetic sockets contribute to decreased quality of life, health, and well-being for persons with amputations. Therefore, improved socket fit is a high clinical priority. METHODS: In this study, we describe the design and testing of a novel sensor system that can be incorporated into a prosthetic socket to measure distal end weight bearing in the socket and can alert a prosthesis user if poor socket fit is suspected. We present the results of testing this device with three Veterans who were new prosthesis users and three Veterans who were experienced prosthesis users. RESULTS AND CONCLUSIONS: We collected sensor data during walking trials while participants wore varying numbers of sock plies and qualitative feedback on the design of the socket fit sensor system. For analysis, peak sensor measurements during walking cycles were identified and combined with socket fit data (i.e., a clinician-determined level of "good," "too tight," or "too loose" and the number of sock ply worn each trial). We found consistent relationships between peak sensor measurements and socket fit in our sample. Also, all users expressed an interest in the device, highlighting its potential benefits during early prosthesis training.Implications for RehabilitationEnsuring socket fit is challenging for many prosthesis users.A novel wearable sensor system can be used to identify socket fit issues for some prosthesis users.This type of system could be most helpful for new prosthesis users and those with sensory and cognitive challenges.

What we know about the scleral profile and its impact on contact lens fitting.

Scleral contact lens fitting has provided practitioners with one of the earliest pieces of evidence that the sclera was more often asymmetric than symmetric. Some preliminary observations such as different haptic alignment patterns over the sclera in 360 degrees, the appearance of fogging in the fluid chamber and excessive tear out-in flow through specific meridians, quadrants, or areas of the haptic provide evidence of some scleral asymmetry. The advent of technologies that allowed measurement of the scleral profile led to formal research confirming that only about 6% of scleras are symmetric, while the rest are toric, quad-specific, or irregular. This has an evident impact on how to focus scleral lens fitting. Measuring the scleral profile also provided us with true ocular sagittal height data for cord diameters beyond the cornea. Although high variability was expected in pathological eyes, healthy eyes also showed a wide range of ocular sagittal heights. Due to this variability among healthy eyes, a discussion has emerged on whether the one-size-fits-all approach to soft lens fitting is a proper strategy to fit the whole spectrum of sagittal heights. The traditional mode of selecting the parameters for custom soft lenses through corneal parameters is also questioned.

Trends in Scleral Lens Fitting Practices: 2020 Scleral Lenses in Current Ophthalmic Practice Evaluation Survey.

OBJECTIVES: To explore trends in demographic characteristics of scleral lens (SL) practitioners and primary indications for SL fitting over 5 years. METHODS: An online survey similar to the 2015 Scleral Lenses in Current Ophthalmic Practice Evaluation (SCOPE) study was designed and administered from November 8, 2019, through March 31, 2020, to attendees at two international contact lens meetings, members of the Scleral Lens Education Society, and participants in the 2015 SCOPE study. Practitioners reporting at least five completed SL fits were included in the analysis. RESULTS: Of 922 respondents, 777 had fit at least five SLs: 63% from the United States (59 other countries were represented), findings similar to the 2015 survey, in which 799 respondents (72%) were US-based and 49 from other countries. Most practitioners were in community practice (76%) than academic practice (24%). In 2015, 64% were in community practice and 36% in academic practice. A median of 84% of SLs were fit for corneal irregularity, 10% for ocular surface disease, and 2% for uncomplicated refractive error. In comparison, the 2015 indications were 74%, 16%, and 10%, respectively. The median number of fits completed per practitioner was 100 (range, 5-10,000; mean [SD] 284 [717]; n=752). In 2015, the median was 36 (range, 5-3,600; mean [SD] 125 [299]; n=678). CONCLUSIONS: The number of experienced SL practitioners is increasing, as is international representation. Most practitioners practice in community rather than academic settings. SLs continue to be primarily prescribed for corneal irregularity and are rarely used solely for correction of refractive error.

Corneal RGP Contact Lens Fitting Software for Keratoconus Built-In Anterior Segment Optical Coherence Tomography.

OBJECTIVE: To assess the performance of the contact lens fitting software built into anterior segment optical coherence tomography (AS-OCT). METHODS: This retrospective study enrolled patients with keratoconus prescribed with spherical corneal rigid gas-permeable contact lenses based on a contact lens fitting software. Subjects were classified into four subgroups based on corneal morphology: nipple, oval, globus, and marginal type. Software performance was evaluated according to the correlation between the back optical zone radius (BOZR) calculated by the contact lens fitting program and the BOZR of the lens prescribed, and the number of trial lens replacements required.Results:A total of 340 eyes of 254 patients with a mean age of 40.4 ± 13.6 years were included. The oval type was the most common (61.8%), followed by the nipple type (26.2%). Linear regression analysis revealed a significant correlation between the prescribed and the calculated BOZR in all subgroups (R 2 = 0.92, P < 0.01 for the nipple type; R 2 = 0.76, P < 0.01 for the oval type; R 2 = 0.93, P < 0.01 for the globus type; and R 2 = 0.79, P < 0.01 for the marginal type). Furthermore, the globus type had the highest proportion of cases requiring at least one trial lens replacement (36.3%), followed by the nipple group (27.0%). There were no significant differences among the subgroups ( P = 0.14). CONCLUSIONS: In conclusion, our findings reveal that the contact lens fitting software built into AS-OCT may be useful for accurate contact lens prescription for any corneal shape.

Prosthetic Replacement of the Ocular Surface Ecosystem for Terrien Marginal Degeneration: A Case Series.

OBJECTIVES: To assess outcomes of the Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) treatment in patients with advanced Terrien marginal degeneration (TMD). METHODS: This is a retrospective case series of patients with advanced TMD who were assessed and fit with customized PROSE lenses. Data were collected on PROSE fitting details including visual acuity (VA) before and after PROSE, slit-lamp findings, and corneal tomography scans. RESULTS: Six eyes in four patients were included. All patients attempted at least one other contact lens (CL) modality before PROSE. Some patients had corneal comorbidities such as pseudopterygium and pseudobleb that contributed to intolerance to previous lenses and warranted extra considerations in the fitting process. With PROSE, VA improved in all six eyes. Patients with structural corneal comorbidities achieved improved vision, comfort, and lens tolerance with PROSE. Two eyes had noncorneal ocular comorbidities that limited PROSE efficacy. Another eye discontinued PROSE wear because of limbal stem-cell disease progression necessitating a limbal stem-cell transplant. CONCLUSIONS: PROSE treatment can be an effective option to improve vision and comfort for patients with advanced TMD who are intolerant to first-line therapeutic CL modalities, even in the presence of other corneal comorbidities.

Benefits of Scleral Lens in the Management of Irregular Corneas and Dry Eye Syndrome After Refractive Surgery.

OBJECTIVES: To evaluate the utility of the SPOT scleral lens (Oxygen Permeable Scleral Lens of Thonon; LAO, Thonon-les-Bains, France) in the management of the irregular cornea after refractive surgery. METHOD: We included 19 patients (35 eyes) with irregular corneas after refractive surgery. Patients were fitted with scleral lenses after the failure of conventional contact lenses adaptation. The ophthalmologic examination included measurement of best-corrected visual acuity (BCVA), slitlamp examination, and evaluation of ocular aberrations (Objective Scattering Index [OSI] and higher-order aberration [HOA]). RESULT: Scleral lens fitting increases significantly the BCVA from 0.33 (±0.25) to 0.08 (±0.13) LogMAR (P<0.001). There was also a significant decrease in Ocular Surface Disease Index from 66.2±22.8 to 42.4±18.9 (P<0.001). Ocular aberrations (OAs) are also significantly reduced by the scleral lenses, the mean OSI goes from 7.2 (±4.2) to 3.0 (±1.8) (P<0.001), OA from 2.58 (±1.34) to 1.98 µm (±2.31) (P=0.035), and HOA from 0.94 (±0.51) to 0.48 (±0.23) (P=0.0018). CONCLUSION: Fitting with scleral lenses improves patients' optical and ocular surface problems. Scleral lens restores BCVA and the quality of life. Fitting with scleral lenses is an alternative to further surgery on these fragile eyes and is sometimes the only viable treatment option for the patient.

Conventional-based contact lens fitting in pure microphthalmia associated with irregular cornea.

In this case, a female teenager presented to the clinic with blurring of vision at a distance in both eyes since 2 years. All preliminary examinations were recorded. Retinoscopy revealed split reflex in both eyes. Both anterior and posterior segment findings seem to be within normal limits except for the microcornea. Topography depicts an asymmetric bow tie with superior steeping in both eyes. This case was diagnosed as pure microphthalmos associated with irregular corneal curvature, suggestive of keratoconus without corneal thinning with the help of topography and biometric measurements. Contact lens trial was advised to improve the visual potential. Fitting this patient in RGP lenses has been a challenging task because of narrow palpebral fissure height and small cornea.

The Acoustics of Instant Ear Tips and Their Implications for Hearing-Aid Fitting.

OBJECTIVES: Today, approximately 70 to 80% of hearing aid fittings are made with silicone instant ear tips rather than custom earmolds. Nevertheless, little is known about the impact of instant ear tips on the acoustic coupling between the hearing aid receiver and the individual ear canal, even though it can have a major impact on the overall sound of the hearing aids. This study aimed to investigate the acoustic properties of different instant ear tip types and their across-subject variability, the within-subject reliability of those properties, and the influence of the users' level of experience with ear-tip insertion on the acoustics. Furthermore, subjective ratings of occlusion produced by the ear tips were considered. DESIGN: Five types of instant ear tips (Open, Tulip, Round [2-vent], Round [1-vent], Double Domes) provided by the hearing aid manufacturer Widex were considered in this study. Probe-microphone measurements were performed at the eardrums of 30 participants (60 ears). In the first experiment, the real ear occluded insertion gain and the vent effect (VE) were measured, and the listeners rated the subjective occlusion experienced with each ear tip. In the second experiment, the same measurements were repeated six times per participant. The within-subject variability of the acoustic ear tip properties was investigated as well as the impact of the degree of users' experience with ear tip insertion on the resulting real ear measurements. RESULTS: All tested ear tips were, on average, acoustically transparent up to 1 kHz except Double Domes, which were only transparent up to 600 Hz. Distinct VE profiles were found for each ear tip type, but a large across-subject variability was observed for both real ear occluded insertion gain and VE. However, the within-subject reliability was high. The measured VE was highly correlated with the perceived occlusion. Finally, no significant effect of the level of experience in ear tip insertion on the acoustic properties of the ear tips was found, but the within-subject variability was larger in the less experienced group. CONCLUSIONS: These results suggest that the acoustic properties of instant ear tips and their coupling to the individual ear canal impact the resulting hearing aid fitting and should be considered by the hearing care professionals and reflected in the fitting software. The high within-subject reliability indicates that the ear tip acoustics remain stable for the individual in daily use. Finally, real ear measurements should be considered an essential part of the hearing aid fitting process in clinical practice to ensure an optimal fit for the individual hearing aid user.