Corneal structure in tilted disc syndrome

To evaluate the central corneal thickness (CCT), corneal volume (CV), and anterior and posterior corneal surfaces using the Scheimpflug imaging system in patients diagnosed with tilted disc syndrome (TDS).

Methods:

The study group (Group 1) and the control group (Group 2) comprised 35 eyes of 35 age-, sex-, and refraction-matched cases. All cases underwent a full ophthalmic examination that included cycloplegic refraction, axial ocular length measurement, and Scheimpflug imaging.

Results:

The mean age was 34.68 ± 15.48 years in Group 1 and 34.11 ± 12.01 years in Group 2 (p=0.864). The gender distribution was 18 males and 17 females in Group 1 and 16 males and 19 females in Group 2 (p=0.618). All subjects were Caucasian. The spherical equivalent was 3.62 ± 1.75 D in Group 1 and 3.69 ± 1.51 D in Group 2 (p=0.850). There was no significant difference in age, sex, race, or spherical equivalent between groups. There was no significant difference in mean keratometric value and CV3 (the CV in the central 3 mm) between groups (p=0.232 and 0.172, respectively). There were statistically significant differences in CCT, CV5, and CV7 (CV in the central 5 and 7 mm³, respectively) and total CV between groups (p=0.008, 0.003, 0.023, and 0.019, respectively). The values of all parameters were lower in the study group than in the control group. There was also a statistically significant difference in the anterior elevation parameters of the cornea between groups (p<0.05). The mean values of Group 1 were higher than those of Group 2. There were statistically significant differences in the two parameters referring to the posterior elevation of the cornea between the two groups (p<0.05).

Conclusion:

The results of this study showed that eyes with TDS have thinner CCT, lower CV, and different anterior corneal curvature than normal eyes.

Keywords:
Corneal topography; Cornea/pathology; Optic disk/abnormalities; Diagnostic techniques, ophthalmological

	Group 1 (n=35)	Group 2 (n=35)
Patient	(Mean ± SD)	(Mean ± SD)	p-value
Age, years	34.68 ± 15.48	34.11 ± 12.01	0.864
BCVA	9/10	10/10	0.963
IOP	16	17	1
Sex
Male, n (%)	18 (51.42%)	16 (45.71%)	0.618
Female, n (%)	17 (48.57%)	19 (54.28%)
ALX, mm	23.50 ± 0.38	23.39 ± 0.41	0.234
Spheric equivalent, D	3.62 ± 1.75	3.69 ± 1.51	0.850

	Group 1 (n=35)	Group 2 (n=35)
Pentacam data	(Mean ± SD)	(Mean ± SD)	p-value
Mean K	40.91 ± 14.66	43.93 ± 12.96	0.232
CCT, µm	517.06 ± 36.31	542.66 ± 41.33	0.008^* * statistically significant; n= number; SD= standard deviation; K= keratometry; CCT= central corneal thickness; CV3= corneal volume in 3 mm3; CV5= corneal volume in 5 mm3; CV7= corneal volume in 7 mm3; CV= total corneal volume.
CV3, mm³	3.75 ± 0.27	3.86 ± 0.37	0.172
CV5, mm³	11.00 ± 0.77	11.59 ± 0.79	0.003^* * statistically significant; n= number; SD= standard deviation; K= keratometry; CCT= central corneal thickness; CV3= corneal volume in 3 mm3; CV5= corneal volume in 5 mm3; CV7= corneal volume in 7 mm3; CV= total corneal volume.
CV7, mm³	23.86 ± 1.86	24.83 ± 1.60	0.023^* * statistically significant; n= number; SD= standard deviation; K= keratometry; CCT= central corneal thickness; CV3= corneal volume in 3 mm3; CV5= corneal volume in 5 mm3; CV7= corneal volume in 7 mm3; CV= total corneal volume.
CV, mm³	57.92 ± 4.25	60.40 ± 4.30	0.019^* * statistically significant; n= number; SD= standard deviation; K= keratometry; CCT= central corneal thickness; CV3= corneal volume in 3 mm3; CV5= corneal volume in 5 mm3; CV7= corneal volume in 7 mm3; CV= total corneal volume.

	Group 1 (n=35)	Group 2 (n=35)
Pentacam data	(Mean ± SD)	(Mean ± SD)	p-value
Max AE5, µm	12.22 ± 6.66	7.51 ± 4.23	0.001^* * statistically significant; n= number; SD= standard deviation; MaxAE5= the maximum elevation value above the BFS at the central 5.0 mm3 of the anterior elevation map; MaxAD5= the maximum depression value below the BFS at the central 5.0 mm3 of the anterior elevation map; AER= anterior elevation ratio obtained from the anterior elevation data; AEDD= anterior elevation depression difference obtained from the anterior elevation data.
Max AD5, µm	-13.11 ± 6.68	-8.31 ± 5.17	0.001^* * statistically significant; n= number; SD= standard deviation; MaxAE5= the maximum elevation value above the BFS at the central 5.0 mm3 of the anterior elevation map; MaxAD5= the maximum depression value below the BFS at the central 5.0 mm3 of the anterior elevation map; AER= anterior elevation ratio obtained from the anterior elevation data; AEDD= anterior elevation depression difference obtained from the anterior elevation data.
AER	1.42 ± 0.95	0.96 ± 0.62	0.001^* * statistically significant; n= number; SD= standard deviation; MaxAE5= the maximum elevation value above the BFS at the central 5.0 mm3 of the anterior elevation map; MaxAD5= the maximum depression value below the BFS at the central 5.0 mm3 of the anterior elevation map; AER= anterior elevation ratio obtained from the anterior elevation data; AEDD= anterior elevation depression difference obtained from the anterior elevation data.
AEDD, µm	24.80 ± 11.82	15.02 ± 9.00	0.001^* * statistically significant; n= number; SD= standard deviation; MaxAE5= the maximum elevation value above the BFS at the central 5.0 mm3 of the anterior elevation map; MaxAD5= the maximum depression value below the BFS at the central 5.0 mm3 of the anterior elevation map; AER= anterior elevation ratio obtained from the anterior elevation data; AEDD= anterior elevation depression difference obtained from the anterior elevation data.

	Group 1 (n=35)	Group 2 (n=35)
Pentacam data	(Mean ± SD)	(Mean ± SD)	P
Max PE5, µm	26.28 ± 15.56	19.74 ± 11.40	0.066
Max PD5, µm	-29.17 ± 13.15	-24.51 ± 12.32	0.140
PER	4.21 ± 2.45	2.88 ± 1.51	0.001^* * statistically significant. n, number; SD= standard deviation; MaxPD5= the maximum depression value below the BFS at the central 5.0 mm3 of the posterior elevation map; MaxPE5= the maximum elevation value above the BFS at the central 5.0 mm3 of the posterior elevation map; PER= posterior elevation ratio obtained from the posterior elevation data; PEDD= posterior elevation depression difference obtained from the posterior elevation data.
PEDD, µm	54.77 ± 27.06	43.17 ± 20.83	0.048^* * statistically significant. n, number; SD= standard deviation; MaxPD5= the maximum depression value below the BFS at the central 5.0 mm3 of the posterior elevation map; MaxPE5= the maximum elevation value above the BFS at the central 5.0 mm3 of the posterior elevation map; PER= posterior elevation ratio obtained from the posterior elevation data; PEDD= posterior elevation depression difference obtained from the posterior elevation data.

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[1] Corresponding author: Abuzer Gunduz. Inonu University School of Medicine. Malatya 44280 - Turkey - E-mail: abuzergunduz@hotmail.com

MaxAE5	The maximum elevation value above the BFS at the central 5.0 mm of the anterior elevation map obtained by moving the cursor to the highest point on the anterior elevation map.
MaxAD5	The maximum depression value below the BFS at the central 5.0 mm of the anterior elevation map obtained by moving the cursor to the lowest point on the anterior elevation map.
AER (anterior elevation ratio)	Obtained from the anterior elevation data. The maximum elevation value above the BFS at the central 5.0 mm of the anterior elevation map divided by the BFS (AER Z MaxAE5/BFS).
AEDD (anterior elevation depression difference)	Obtained from the anterior elevation data. The highest minus lowest value above and below the best-fit sphere (BFS) (AEDD Z MaxAE5 _ MaxAD5).
MaxPD5	The maximum depression value below the BFS at the central 5.0 mm3 of the posterior elevation map obtained by moving the cursor to the lowest point on the posterior elevation map.
MaxPE5	The maximum elevation value above the BFS at the central 5.0 mm3 of the posterior elevation map obtained by moving the cursor to the highest point on the posterior elevation map.
PEDD (posterior elevation depression difference)	Obtained from the posterior elevation data. The highest minus lowest value above and below the BFS (PEDD = MaxPE5 - MaxPD5).
PER (posterior elevation ratio)	Obtained from the posterior elevation data. The maximum elevation value above the BFS at the central 5.0 mm3 of the posterior elevation map divided by the BFS (PER = MaxPE5/BFS).