Computerized corneal topography (also known as computer assisted corneal topography, computer assisted keratography, or videokeratography) is a computer- assisted diagnostic technique in which a special instrument projects a series of light rings on the cornea, creating a color-coded map of the corneal surface as well as a cross-section profile. This test is used for the detection of subtle corneal surface irregularities and astigmatism as an alternative to manual keratometry.

The American Academy of Ophthalmology’s guidelines on “Primary open-angle glaucoma” (AAO, 2010) mentioned no role for corneal topography in the management of patients with open-angle glaucoma.

Choi and Kim (2012) examined the longitudinal changes in corneal topographic indices over time in patients with mild keratoconus (KC) and determined predictive factors for the increase in corneal curvature. These investigators retrospectively reviewed the data of 94 eyes of patients with mild KC who had undergone computerized video-keratography (Orbscan IIz; Bausch & Lomb Surgical, Rochester, NY) at least twice at an interval of greater than or equal to 1 year. Patients with an increase of greater than or equal to 1.50 diopters (D) in the central keratometry (K) were placed in the progression group, and the others were placed in the non-progression group. In each group, the quantitative topographic parameters were compared and tested as predictive factors for KC progression. Additionally, corneal astigmatic changes were evaluated by means of vector analysis. In total, 94 eyes of 85 patients were included -- 25 of 94 (26.5 %) eyes showed progression of the central K greater than or equal to 1.50 D; progression took 3.5 years on average. Median time to progression by Kaplan-Meier analysis was 12 years. Significant predictors for KC progression were as follows: highest point on the anterior elevation from the anterior best-fit sphere (BFS), greater than or equal to 0.04 mm; irregularity index at 3 mm, greater than or equal to 6.5 D; irregularity index at 5 mm, greater than or equal to 6.0 D; thinnest pachymetry, less than 350 μm at baseline examination; yearly change rate of anterior BFS, greater than or equal to 0.1 D/year; central K, greater than or equal to 0.1 D/year; simulated K in maximum, greater than or equal to 0.15 D/year; simulated K in minimum, greater than or equal to 0.2 D/year; and anterior chamber depth, greater than or equal to 0.0 mm/year. The dominant with-the-rule pattern of astigmatism at the baseline examination was changed to an oblique pattern of astigmatism at the last examination. The authors concluded that mild KC tended to be progressive in approximately 25 % of patients, and progression lasted 3.5 years on average. They stated that longitudinal changes in the corneal topography quantitative indices can be used as predictors of KC progression.

Follow-Up Evaluation of Keratoconus

An UpToDate review on “Keratoconus” (Wayman, 2015) states that “Corneal topography -- The introduction of corneal topography has helped in the identification of subtle presentations, which can lead to an earlier diagnosis. Major topographic patterns found in keratoconus include asymmetric bowtie, with or without inferior steepening, and skewed radial axes. However, once the diagnosis is made, serially corneal topography is of little value in following patients”.

Microphthalmia

Hu and colleagues (2015) determined the typical corneal changes in pure microphthalmia using a corneal topography system and identified characteristics that may assist in early diagnosis. Patients with pure microphthalmia and healthy control subjects underwent corneal topography analysis to determine degree of corneal astigmatism (mean A), simulation of corneal astigmatism (sim A), mean keratometry (mean K), simulated keratometry (sim K), irregularities in the 3 - and 5-mm zone, and mean thickness of 9 distinct corneal regions. Patients with pure microphthalmia (n = 12) had significantly higher mean K, sim K, mean A, sim A, 3.0 mm irregularity and 5.0 mm irregularity, and exhibited significantly more false keratoconus than controls (n = 12). There was a significant between-group difference in the morphology of the anterior corneal surface and the central curvature of the cornea. The authors concluded that changes in corneal morphology observed in this study could be useful in borderline situations to confirm the diagnosis of pure microphthalmia. These preliminary findings need to be validated by well-designed studies.

Other Experimental Indications

In a retrospective, clinic-based, case-control study, de Paiva et al (2003) determined the correlation between the regularity indices of the Tomey TMS-2N computerized videokeratoscopy (CVK) instrument (Tomey, Waltham, MA) with conventional measures of dry eye symptoms and disease. A total of 16 eyes of 16 asymptomatic normal subjects and 74 eyes of 74 patients with reports of ocular irritation were included in this study. Corneal surface regularity and potential visual acuity indices (PVAI) of the Tomey TMS-2N CVK instrument were evaluated in patients with ocular irritation symptoms and in normal subjects. The surface regularity index (SRI), surface asymmetry index (SAI), PVAI, and irregular astigmatism index (IAI) of the Tomey TMS-2N were compared between normal and dry-eye patients. Severity of dry-eye symptoms was assessed with a validated questionnaire. Schirmer 1 test (without anesthesia), biomicroscopic meibomian gland evaluation with a composite severity score (MGD score), fluorescein tear break-up time (TBUT), and corneal fluorescein staining were performed. The correlations between CVK indices of the Tomey TMS-2N and the symptom severity score, Schirmer 1 test, MGD score, TBUT, and corneal fluorescein staining score were studied. Dry-eye patients had greater mean symptom severity scores, lower Schirmer 1 test scores, greater MGD scores, more rapid TBUT, and greater total corneal fluorescein staining scores (p < 0.001 for all parameters). The SRI, SAI, and IAI were all significantly greater in dry-eye patients than normal subjects. These were 0.46 +/- 0.36 (normal) versus 1.09 +/- 0.76 (dry) for the SRI (p= 0.0017), 0.30 +/- 0.15 (normal) versus 0.90 +/- 1.09 (dry) for the SAI (p = 0.0321), and 0.42 +/- 0.28 (normal) versus 0.56 +/- 0.24 (dry) for the IAI (p = 0.0321). The PVAI was significantly lower in the dry-eye patients (0.89 +/- 0.13) than normal eyes (0.68 +/- 0.23; p = 0.0008). The SRI, SAI, and IAI were positively correlated with total and central corneal fluorescein staining scores (p < 0.00001 for all indices). An SRI greater than or equal to 0.80), SAI (greater than or equal to 0.50), and IAI (greater than or equal to 0.50) had sensitivities in predicting total corneal fluorescein staining (score greater than or equal to 3) of 89 %, 69 %, and 82 %, respectively. The specificity of these indices was 80 %, 78 %, and 82 %, respectively. In all 90 eyes, the mean SRI was greater in subjects older than 50 years (p = 0.012) compared with younger patients, whereas no age effect was noted in the dry-eye patients. The SRI and PVAI showed better correlation with symptoms of blurred vision than the best-corrected visual acuity (BCVA). The authors concluded that patients with ocular irritation had an irregular corneal surface that may contribute to their irritation and visual symptoms. Because of their high sensitivity and specificity, the regularity indices of the Tomey TMS-2N have the potential to be used as objective diagnostic indices for dry eye, as well as a means to evaluate the severity of this disease.

The American Academy of Ophthalmology Cornea/External Disease Panel’s Preferred Practice Pattern on “Dry Eye Syndrome” (AAO, 2013) had no recommendation for computerized corneal topography.

The AAO’s guideline on “Herpes simplex virus keratitis” (White and Chodosh, 2014) does not include a recommendation for corneal topography.

Furthermore, UpToDate reviews on “Retinal detachment” (Arroyo, 2018) and “Diagnosis and classification of Sjogren's syndrome” (Baer, 2018) do not mention corneal topography as a management tool.

Evaluation of Corneal Ectasia

The AAO Preferred Practice Pattern Cornea and External Disease Panel’s “Corneal Ectasia Preferred Practice Pattern” (Garcia-Ferrer et al, 2019) states that “Corneal ectasia is progressive corneal steepening and thinning. Types of corneal ectasia include keratoconus, pellucid marginal degeneration, keratoglobus post kerato-refractive ectasia, and wound ectasia after penetrating keratoplasty (PK). Corneal ectasias are associated with decreased uncorrected visual acuity (UCVA), an increase in ocular aberrations, and often a loss of best-corrected distance visual acuity. Corneal ectasias can result in significant ocular morbidity and may require surgical intervention … The diagnosis of corneal ectasia is usually based on a typical patient history and characteristic findings on topography and tomography … A comprehensive evaluation of both the anterior and posterior surfaces (topographically and tomographically) as well as full pachymetric mapping of the cornea is felt to be important in establishing the diagnosis of corneal ectatic disease and following its course. Slit-scanning corneal topography and Scheimpflug imaging systems can evaluate these parameters and have expanded diagnostic criteria for keratoconus, subclinical keratoconus, pellucid marginal degeneration, and post kerato-refractive corneal ectasias. Their use are necessary to properly screen potential refractive surgery patients … Prior to refractive surgery, corneal topography and tomography performed following a period of contact lens abstinence should be reviewed for evidence of irregular astigmatism or abnormalities suggestive of keratoconus or other forms of corneal ectasia”.

Evaluation of Keratoconus after Treatment with Penetrating Keratoplasty

In an observational study, Ono and colleagues (2020) examined the characteristics of anterior and posterior corneal topography in keratoconic eyes more than 30 years after PK. Patients who maintained clear grafts for more than 30 years after PK were included and divided into the keratoconus (KC) group or other diseases (Others) group, based on the primary indication; 26 eyes of 26 patients were included. The KC group and the Others group included 14 eyes and 12 eyes, respectively. The KC group subjects were younger at the time of surgery (p = 0.03). No differences were observed in best-spectacle-corrected VA, keratometric power, and central-corneal-thickness. Based on corneal topography using Fourier harmonic analyses, regular astigmatism in the anterior cornea was significantly larger (p = 0.047) and the spherical component in the posterior cornea was significantly lower (p = 0.01) in the KC group. The area under the receiver operating characteristic curve (AUC) of the spherical component, regular astigmatism, asymmetry component, and higher-order irregularity were 66.07 %, 63.10 %, 57.14 %, and 59.23 %, respectively, in the anterior cornea and 80.65 %, 52.98 %, 63.10 %, and 63.99 %, respectively, in the posterior cornea. The authors concluded that these findings suggested that Fourier harmonic analysis of corneal topography could be useful for patients with KC long after PK. Moreover, these researchers stated that prospective, clinical studies that examine more items, compare the pre-operative and post-operative data, and detect risk factors for recurrence are needed.

The authors stated that this study had several drawbacks. First, the study design was retrospective, and the number of patients was small (n = 26) owing to the rarity of patients who have maintained clear grafts for more than 30 years after PK. These findings successfully disclosed significant differences in some parameters with Fourier harmonic analysis, although the small patient number could have resulted in a low detection power. Second, the frequency at which corneal topographic analysis was conducted was limited. With relatively stable corneal surfaces, patients did not need to frequently visit a medical facility and undergo corneal topographic analysis. Third, some patients underwent PK at another institution and their data were unavailable for pre-operative and post-operative comparison.

Neurotrophic Keratoconjunctivitis

In a retrospective, case-control study, de Paiva et al (2003) examined the correlation between the regularity indices of the Tomey TMS-2N computerized video-keratoscopy (CVK) instrument (Tomey, Waltham, MA) with conventional measures of dry eye symptoms and disease. A total of 16 eyes of 16 asymptomatic normal subjects and 74 eyes of 74 patients with reports of ocular irritation were included in this analysis. Corneal surface regularity and potential visual acuity (VA) indices of the Tomey TMS-2N CVK instrument were evaluated in patients with ocular irritation symptoms and in normal subjects. The surface regularity index (SRI), surface asymmetry index (SAI), potential VA index (PVA), and irregular astigmatism index (IAI) of the Tomey TMS-2N were compared between normal and dry-eye patients. Severity of dry-eye symptoms was assessed with a validated questionnaire. Schirmer 1 test (without anesthesia), biomicroscopic meibomian gland evaluation with a composite severity score (MGD score), fluorescein TBUT, and corneal fluorescein staining were performed. The correlations between CVK indices of the Tomey TMS-2N and the symptom severity score, Schirmer 1 test, MGD score, TBUT, and corneal fluorescein staining score were studied. Dry-eye patients had greater mean symptom severity scores, lower Schirmer 1 test scores, greater MGD scores, more rapid TBUT, and greater total corneal fluorescein staining scores (p < 0.001 for all parameters). The SRI, SAI, and IAI were all significantly greater in dry-eye patients than normal subjects. These were 0.46 +/- 0.36 (normal) versus 1.09 +/- 0.76 (dry) for the SRI p = 0.0017), 0.30 +/- 0.15 (normal) versus 0.90 +/- 1.09 (dry) for the SAI (p = 0.0321), and 0.42 +/- 0.28 (normal) versus 0.56 +/- 0.24 (dry) for the IAI (p = 0.0321). The PVA index was significantly lower in the dry-eye patients (0.89 +/- 0.13) than normal eyes (0.68 +/- 0.23; p = 0.0008). The SRI, SAI, and IAI were positively correlated with total and central corneal fluorescein staining scores (p < 0.00001 for all indices). An SRI (greater than or equal to 0.80), SAI (greater than or equal to 0.50), and IAI (greater than or equal to 0.50) had sensitivities in predicting total corneal fluorescein staining (score greater than or equal to 3) of 89 %, 69 %, and 82 %, respectively. The specificity of these indices was 80 %, 78 %, and 82 %, respectively. In all 90 eyes, the mean SRI was greater in subjects older than 50 years (p = 0.012) compared with younger patients, whereas no age effect was noted in the dry-eye patients. The SRI and PVA index showed better correlation with symptoms of blurred vision than the BCVA. The authors concluded that patients with ocular irritation had an irregular corneal surface that may contributed to their irritation and visual symptoms. Because of their high sensitivity and specificity, the regularity indices of the Tomey TMS-2N have the potential to be used as objective diagnostic indices for dry eye, as well as a means to evaluate the severity of this disease.

Dada et al (2007) examined the corneal topographic response to intra-ocular pressure (IOP) reduction in vernal keratoconjunctivitis (VKC) with steroid-induced glaucoma. A total of 42 eyes of 21 patients with VKC and steroid-induced glaucoma (Group I) and 66 eyes of 33 patients with VKC without glaucoma (Group II) underwent an evaluation by Orbscan topography. In eyes with glaucoma, the IOP was controlled medically; and the corneal topography was repeated at 3 months to evaluate effect on corneal parameters. The mean baseline IOP was 36.40 +/- 13.08 mmHg in Group I, 14.67 +/- 4.62 mmHg in Group II (p < 0.0001). The IOP after treatment at 3 months follow-up was 15.00 +/- 5.41 mmHg in Group I (p < 0.0001). In Group I, the mean maximum Sim K decreased from 44.86 +/- 3.21 D to 43.87 +/- 2.62 D (p = 0.031) and mean posterior corneal elevation decreased from 64.9 +/- 22.36 um to 35.7 +/- 28.91 um at 3 months after reduction of IOP (p = 0.001). There was a significant positive correlation between the reduction in the IOP and the decrease in the posterior corneal elevation (r = 0.664, p = 0.001). The authors concluded that eyes with VKC with and without glaucoma had similar corneal topography. Increased IOP associated with steroid-induced glaucoma and VKC may contribute to an increase in the corneal curvature and posterior corneal elevation. These changes may be reversed by a reduction in the IOP with medical therapy.

Umale et al (2019) noted that association of keratoconus with VKC is well-known; however, there are few topographic studies describing actual prevalence especially in India where it is a common condition. There is also scarce literature on the topographic patterns and sub-clinical topographic anomalies in cases of vernal catarrh and their relationship with various subtypes. In a cross-sectional study, these investigators estimated the prevalence of sub-clinical keratoconus among Indian subjects with VKC and described the various topographic abnormalities that could aid in screening for these cases. This study was carried out at a tertiary care center; a total of 76 established cases of VKC were evaluated with placido disc-based video-keratography for topographic abnormalities and early keratoconus based on modified Rabinowitz-McDonnell criteria. A total of 17 (11.2 %) eyes satisfied both the modified Rabinowitz-McDonnell criteria of keratoconus. Corneal topographic pattern analysis showed asymmetric bowtie with inferior steepening in 17.11 % of the patients. None of these patients had clinical evidence of keratoconus. The authors concluded that the findings of this study showed 11.2 % prevalence of keratoconus in patients suffering from VKC (statistical significance). The findings highlighted the importance of using a simple placido disc-based corneal topography system for screening the patients with VKC for keratoconus. This can help in early detection and preventive intervention.

Scope of Policy

This Clinical Policy Bulletin addresses

.

Medical Necessity

Aetna considers computerized corneal topography medically necessary for

of the following conditions:

*Generally, 1 testing for each eye is sufficient for fitting, unless there is some reason for repeat testing conducted in the medical record, such as a change in the member's condition from the prior examination. Repeat testing to monitor disease progression in keratoconus or Terrien's marginal degeneration may be necessary over time.

Experimental and Investigational

Computerized corneal topography is considered experimental and investigational because the effectiveness of this approach has not been established for the following:

Policy Limitations and Exclusions

ver computerized corn